By F. Bascom, W. B. Clark, N. H. Dartoii, H. B. Kummel, R. D. Salisbury, B. L. Miller, and G. N. Knapp.
INTRODUCTION. tains and plateau. Topographically there is similar prominences rise 100 to 200 feet above the subsequently uplifted with more or less folding. usually a more or less abrupt passage from a upland. These facts are indicated by their constitution, LOCATION AND AREA. trenched upland to level-topped mountains and In Maryland the western edge of the upland their structure, and their mutual relations. They The area herein referred to as the Philadelphia ridges. reaches an altitude of 700 feet, and slopes to an include some of the oldest materials known to have district lies between 39° 45' and 40° 15' north On the east the plateau is separated from the eastern margin in the vicinity of Baltimore, 300 thus accumulated and some of the most recent. latitude and 75° and 75° 30' west longitude. It seaward margin of the continental shelf by a belt feet above tide level. Rocky Ridge and State The first sediments that were deposited in this covers one-quarter of a square degree, which is of coastal province 250 miles in width. The Ridge are monadnocks on this upland. Atlantic belt were of arkosic and argillaceous equivalent in this latitude to 915.25 square miles, greater part of this is under water in this latitude; In Virginia, North Carolina, South Carolina, character, and their deposition took place in pre- or about 34.50 miles from north to south and 26.53 the land portion is called the Coastal Plain. This and Georgia the plateau slopes southeastward and Paleozoic time. The subsequent compression and miles from east to west. dips gently eastward under the sea and increases southward. Its summits range from 500 to 1500 folding to which the arkose and argillites were The district consists of four quadrangles the greatly in width toward the south. The boundary feet in height along its western border, and its subjected have developed from them a hard, Germantown, Norristown, Philadelphia, and Ches between plateau and plain is usually defined by a eastern margin has an altitude of 300 to 500 feet. crystalline, finely banded gneiss, composed largely ter each of which measures fifteen minutes of well-marked change in the topographic features Southwest Mountains, Brushy Mountains, South of quartz and feldspar, and a mica gneiss with latitude and fifteen minutes of longitude. It lies and geologic formations. Topographically the Mountain, and many others are residual masses on interbedded mica schist facies. These gneisses in three States Pennsylvania, New Jersey, and change consists generally of an abrupt transition this plateau. have been differently named in different portions Delaware and embraces in whole or in part ten from a diversified upland to a relatively undiver- The plane surface which, sloping gradually from of the plateau. In the Pennsylvania Piedmont counties, namely: Bucks, Montgomery, Philadel sified lowland. Geologically there is a transition western border to eastern margin, forms the the finely banded quartz-feldspar gneiss is inti phia, Delaware, and Chester counties in Pennsyl from consolidated and for the most part crystalline plateau, does not owe its even contour to the mately associated with the more massive gneiss and vania ; Burlington, Camden, Gloucester, and Salem rocks to unconsolidated clays, sands, and gravels underlying rock formations, for they possess highly forms with it the composite Baltimore gneiss, while counties in New Jersey; and Newcastle County in of more recent age. These Coastal Plain forma complex structures. The larger streams, which the mica gneiss is known as the Wissahickon mica Delaware. Within these limits there is a population tions always overlap the eastern border of the have cut into the plateau, converting it into a gneiss. of more than a million and a half. plateau, and in some districts are found far inland diversified upland, maintain courses which are The pre-Cambrian movements which metamor and somewhat obscure the passage from plateau to quite independent of the structure and character of phosed these formations were accompanied by the OUTLINE OF GEOGRAPHY AND GEOLOGY OF ATLANTIC plain. the rock floor. The tributary or subsequent intrusion of bosses, irregular masses, sills, and BORDER REGION. The margin of the plateau is always indicated, streams, on the other hand, show adjustment to the dikes of molten material which further altered the The Atlantic border region, of which the Phila however, by a change in the character of the constitution of the rock floor; and by means of squeezed sediments and which consolidated as delphia district is a part, is divisible into two streams which pass from plateau to plain. An them the heterogeneity of rock character and the granite, gabbro, pyroxenite, and peridotite. distinct geologic provinces the Appalachian and abrupt decrease in stream velocity characterizes complexity of rock structure are finding expression. With the opening of Paleozoic time there were the Coastal. The Philadelphia district comprises this passage, and so frequently do falls or rapids The general trend of the highlands, which is deposited upon these gneisses successively arena portions of both provinces, each of which is char mark the margin of the plateau that this boundary northeast-southwest, in harmony with the strike of ceous, arenaceous-argillaceous, calcareous, and argil acterized by special topographic features which has been called the "fall line." This term is the underlying rocks, does not accord with the laceous sediments. This deposition, taking place record its geologic and physiographic history. imperfectly descriptive of the boundary, which is main drainage lines of the plateau but with the in Cambrian and Ordovician time, extended over The Appalachian Province is composed of three actually a zone of appreciable width. East of this courses of the secondary streams. The main a considerable portion of the Piedmont region, but well-defined geographic districts, which extend zone navigable streams leading to tidal estuaries streams of the plateau, rising either in the Appa not throughout the region. The intense folding, throughout its length. The Allegheny and Cum afford good shipping facilities; west of it the lachian Mountains or on the inland border of the faulting, and accompanying metamorphism to berland plateaus form the most western of these streams cease to be navigable and occupy narrow Piedmont, pursue courses consequent upon the which they were subjected by the close of Paleozoic divisions; the Greater Appalachian Valley, com turbulent channels. In the southern extension of slope of the upland i. e., to the east, southeast, time converted the arenaceous materials into quartz- prising in Pennsylvania a group of valleys and a the plateau the "fall line" gradually rises until in and south, and either empty into estuaries heading ite, the arenaceous-argillaceous sediments into inter- succession of narrow ridges, constitutes the central the Carolinas and Georgia, although falls and at the eastern margin of the Plateau or, crossing bedded quartzites and mica schists, the calcareous district, while the eastern division of the province rapids still mark its location and furnish power the Coastal Plain, empty directly into the Atlantic material into marble and calc schists, and the embraces the Appalachian Mountains, which for factories, it lies considerably above the tidal or into the Gulf of Mexico. The Delaware, Sus- argillaceous deposits into slates or micaceous schists. border the Greater Valley, and the group of plateaus limit. quehanna, and 'Potomac are such master streams These formations, which are widespread though which, stretching away to the east, constitute a The position of this "fall line," at the head of which have cut into the plateau rugged valleys not continuous throughout the Piedmont belt, are vast upland known as the Piedmont Plateau. navigation and at the source of water power, has transverse to the strike of the rock formation. respectively designated in the Pennsylvania Pied Of the three divisions of the Appalachian been a dominant factor in determining the location South of an east-west line drawn just north of mont the Chickies quartzite, the Shenandoah lime Province, only a part of the eastern, or Piedmont of the large cities of the Atlantic States. A line New Brunswick, N. J., the interstream areas are stone, and the Octoraro schist. Plateau, is embraced within the district described passing through New York, Trenton, Philadelphia, covered by a mantle of residual soil and are These crystallized sediments and igneous intru in this folio. Wilmington, Baltimore, Washington, Fredericks- characterized by absence of rock ledges. North of sions constitute the foundation of the Pennsylvania burg, Richmond, Petersburg, Raleigh, Columbia, this line the rock mantle is glacial drift, the depth Piedmont Plateau, but are uncovered only in PIEDMONT PLATEAU. Augusta, and Macon will therefore mark in a of which varies from zero to 200 feet. Rock detached belts trending northeast and southwest. By F. BASCOM. general way the passage from plateau to plain. ledges become an increasingly prominent feature They have been folded in synclinoria and anti- GEOGRAPHY. While the plateau exhibits diversity of scenery, toward the north, and contours are controlled, not clinoria made up of compressed anticlines and The Piedmont Plateau lies at the southeastern there are certain general features common to the by streamwork alone, but by ice erosion and synclines with dominant isoclinal southeast dips foot of the Appalachian Mountains, and owes its entire region which make it a topographic unit. deposition. and steep southeast cleavage dips, and have further name to this location. It extends northeastward The province is, in' brief, a sloping upland of The discordance of underground structure with suffered thrust faulting. until it merges into the New England Plateau and moderate elevation dissected by rather shallow the level contour of the plateau, the presence of These geologic formations and structures are not southwestward as far as Alabama, curving parallel open valleys, which become usually more rugged residual eminences, the V-shaped valleys within confined to the plateau but appear also in the to the Atlantic coast line. Its mean width is 60 and narrower on the > eastern border, and diversi broad U-shaped valleys, the nonadjustment of the Appalachian Mountains, into which the plateau miles, and it has a maximum width, in the central fied by isolated eminences rising above the general master streams to rock formations, the deep rock merges on the west without geologic change, form portion, of 120 miles. level of the upland. These valleys have been mantle and the absence of rock ledges, all have ing with the Appalachian Mountains a geologic unit. The Appalachian Mountains, which form its formed by recent stream cutting since the plateau their explanation in the history of the plateau, Upon the central and northeastern portions of northwest border, while more or less distinct topo surface was carved. If they were filled in, the which will be outlined under the heading "Physi this eroded crystalline floor there accumulated in,a graphically, are united with the Piedmont Plateau uplands would be converted into an elevated plain, ographic record." (See p. 18.) shallow inland estuary both coarse and fine ripple- in one physiographic division because the mountains or plateau, sloping eastward and southeastward marked sands and sun-cracked mud which in GEOLOGY. and the plateau express essentially one and the same toward the Atlantic or south to the Gulf of places bears the tracks of animals or is locally rich geologic and physiographic history. South of Mexico. The rocks of the Piedmont Plateau include both in vegetable matter. Contemporaneously with this Pennsylvania these highlands are chiefly repre Above the surface of this sloping upland rise highly metamorphosed crystalline material and deposition, which took place in the Triassic period, sented by the Cohutta Mountains of Georgia, the isolated eminences, left unreduced by the erosion unmetamorphosed fragmental material. The oldest igneous material was intruded between the beds of Great Smoky Mountains of Tennessee and North which produced the peneplain, now an upland. formation of the Pennsylvania Piedmont is presum sediment, or traversed them in the form of dikes, Carolina, and the Blue Ridge of North Carolina, On the New England Plateau, Mount Monad- ably of igneous origin i. e., the material consoli or was poured out in lava flows. The consolida Virginia, and Maryland. In Pennsylvania* the nock, a typical residual prominence, has furnished dated from a molten condition, Since consolidation tion and uplifting of these sediments took place continuation of the Blue Ridge in South, Never- to physiographic literature the term "monadiiock," it has been subjected to pressure and metamor- without metamorphism. The uplift was accom sink, Lehigh, and Musconetcong mountains limits by which similar residual hills are designated. phism, which have produced an obscurely banded panied by abundant normal faulting and tilting, the Plateau on the west. North of Pennsylvania In New Jersey the upland has a relief on its structure. Such rocks are largely composed of sufficient only to produce gentle west and north the Highlands of New Jersey and New York form western edge of about 800 feet, while a few quartz and feldspar and are known as gneisses. west dips. These formations, wherever they occur its western margin. monadnocks rise a little above that height, and the In the Pennsylvania Piedmont they form a part of on the Piedmont Plateau, possess a very uniform Physiographically this boundary between the eastern margin ranges from near sea level to an a composite formation known as the Baltimore constitution and character, and are known in Appalachian Mountains and the Piedmont Plateau altitude of about 60 feet. gneiss. Pennsylvania and New Jersey, where they cover a is not sharply defined but is crossed by features The Pennsylvania upland descends from an The later formations are chiefly of sedimentary large part of the plateau, as the Stockton and possessing similar and contemporaneous origins. altitude of 900 feet to an average elevation of 200 origin i. e., the materials of which they a,re com Lockatong formations and the Brunswick shale. Geologically there is no destinction, the same geo feet in the neighborhood of Philadelphia. The posed were accumulated beneath the sea, consoli The contemporaneous igneous material, occurring logic formations and structures appearing in moun monadnocks, Long Hill, Gibraltar Hill, and other dated by pressure and cementing materials, and in the form of lava flows, sills, and dikes, is diabase and basalt. The latter rocks resist erosion and From the "fall line" the Coastal Plain, or ment. This escarpment, beginning at the 20-foot Bridgeport a distance of 5 to 6 miles southeast form bold ridges whose level tops are a part of the subaerial portion, has a gentle slope to the south contour line and 40 feet in height, is separated by of the Delaware. The area between the river and Piedmont slope or whose summits rise as monad- east, seldom exceeding 5 feet to the mile, except in a faint and narrow terrace from a second escarp this escarpment is characterized by exceedingly nocks above the plain. Such eminences are the the vicinity of the Piedmont Plateau, where the ment, which rises to the altitude of 80 feet. The low relief, extremely gentle slopes, and correspond Palisades in New York and New Jersey, First and slope is occasionally as great as 10 to 15 feet to combined escarpments form a well-marked topo ingly sluggish streams bordered by marsh land. Second Watchung mountains and Sourland Moun the mile. The submarine portion, or continental graphic feature which in the neighborhood of Eastward the land gradually rises, over the divides, tain in New Jersey, Haycock Mountain, Rock Hill, shelf, is even more monotonously flat, as marine Philadelphia is some 5 miles from the river. To to a height of nearly 100 feet. At this height Long Hill, Gibraltar Hill, and many other lesser erosion and submarine deposition have smoothed the extreme north and south of the city it lies close occur the second escarpment and terrace. This hills in Pennsylvania. out the irregularities due to "earlier subaerial erosion. to the west bank of the Delaware. From the top terrace is not so flat as the low-lying one, and the On the extreme eastern border of the Piedmont The continental shelf bears the sandbars which of this escarpment, represented by the 80-foot con streams which have cut through it have a higher Plateau and in adjacent outlying areas the crystal fringe the Atlantic coast and the sand flats and tour line, the upland terrace gradually rises, reach gradient; consequently the marsh land diminishes line floor is concealed beneath unconsolidated marshes which almost unite the bars to the Coastal ing at a height of 160 to 180 feet the base of a and the valleys become more pronounced. From gravel, sand, and clay, which were deposited in a Plain. third well-defined escarpment. This escarpment, this second escarpment to the southeastern border marine estuary and along a former coast line dur The moderate elevation of the Coastal Plain, the crest of which is marked by the 180- and 200- of the Philadelphia district the country is rolling, ing Cretaceous time. These are the Patapsco and which seldom reaches 400 feet and is for the most foot contour lines, extends from Somerton on the and in the region of Turnersville the surface is Raritan formations of the Lower Cretaceous and part less than half that amount, has prevented the northeast southwestward to Gordon Heights, where even hilly. In the vicinity of Barnsboro, Wenonah, the Magothy formation and Matawan, Monmouth, streams from cutting valleys of any considerable the three escarpments merge. Fox Chase, Summit, Good Intent, and Laurel Springs the valleys are and Rancocas groups of the Upper Cretaceous. depth. Throughout the greater portion of the the Queen Lane reservoir, the Swarthmore College relatively deep and the stream gradients are suffi Overlapping these formations and left by erosion plain, therefore, the relief is inconsiderable, the buildings, and the Chester reservoir are located on cient for mill ponds. A more or less conspicuous in scattered areas is a thin covering of sand and streams flowing in open valleys which lie at only its crest, from which the relatively flat slope to the feature of the valleys of the Coastal Plain is the fact gravel belonging to the Tertiary and Quaternary slightly lower levels than the broad, flat divides. Delaware can be surveyed. that the northeast slopes are steeper than the south periods. They show that the eastern border of the The drainage is largely simple, most of the streams Northwest of the escarpment a more rugged west. This is particularly striking in the valleys plateau was intermittently submerged beneat^ being consequent upon the uplift of the plain from topography prevails. The upland rises more cut by Pensauken Creek, the branches of Mantua estuarine waters during these periods. They are the sea and lying wholly within the Coastal Plain. rapidly, and 10 to 14 miles northwest of the Creek, Edwards Run, etc., and is thought to be the Cohansey and Lafayette formations of the The master'rivers are the extension of streams that Delaware elevations of 400, 460, and 500 feet are due to the fact that weathering is stimulated on the Tertiary period and the Bridgeton, Pensauken, and rise in the Piedmont or Appalachian districts and reached. These elevations mark the level tops of southwest slopes, which are exposed to the sun, Cape May formations of the Quaternary. are therefore complex. hills which trend northeast-southwest and which more than -on the northeast slopes. The rapid Conspicuous features of the plain are the marshes constitute a more or less well-defined topographic melting of frost and snow and alternate freezing COASTAL PROVINCE. bordering the stream courses, and the numerous feature known as Buck Ridge. and thawing which take place on this slope wear By F. BASCOM and B. L. MILLER. bays and estuaries, which are due to the submer In the western part of the Philadelphia district, down the easily eroded Cretaceous materials more GEOGRAPHY. gence of valleys carved during a time when the in the southwestern portion of the Norristown rapidly on the right bank than on the left, where The Coastal Province forms the eastern margin province stood at a higher level than the present. quadrangle, Buck Ridge is separated by a shallow the materials may remain continuously frozen dur of the North American continental plateau, and is Chesapeake Bay (the old valley of the Susque valley, known as Cream Valley, from conspicuous ing the larger part of the winter season. in geologic and geographic features essentially hanna) and Delaware Bay (the extended valley of hills rising at Paoli and Devon to a height of 520 This differential weathering would be most unlike the Piedmont Plateau. Its western limit the Delaware) together with such tributary streams feet. These hills are known as the South Valley effective on such easily transported materials as coincides with the eastern boundary of the Pied as Patuxent, Potomac, York, and James rivers, Hills. North of them lie Chester Valley and the the unconsolidated sands of the Cretaceous, and mont Plateau and has already been characterized are chief among such bays and estuaries. The North Valley Hills, also trending northeast and would not be so effective on the crystalline forma as the "fall line." Its eastern limits are denned streams which have their sources in the Appa southwest and rising to a height of 600 feet. The tions of the Piedmont Plateau, where, therefore, a by the steep slopes of the continental shelf, which lachian province are sometimes turned at the "fall shapes of these hills and of Chester Valley are due similar difference of valley slopes is not found. vary in height from 5000 to 10,000 or more feet. line" in a direction roughly parallel to the strike to the character of the rock floor. Hard quartzite This declivity generally begins at a depth of 450 of the formation, or the old coast line. Otherwise and quartzose mica schist appear in the hills, while DRAINAGE. to 500 feet below sea level, and the descent from the structure of the geologic formations and the the valley is underlain by relatively easily weath Delaware River, which flows parallel to the this level to greater ocean depths is steep. Off character of the materials have had but slight effect ered limestone. Toward the north this rock floor trend of the geologic formations and topographic Cape Hatteras there is an increase in depth of upon stream development, except locally. slopes northwest and passes under a cover of Tri features, and Schuylkill River, tributary to the 9000 feet within 13 miles, a grade as steep as that assic formations, and the topography alters in Delaware and flowing transverse to the geologic found on the flanks of the greater mountain systems. GECXLOGY. character. In the eastern half of the Philadelphia and topographic conformations, are the chief In striking contrast to this declivity is the com The structure of the Coastal Plain is extremely district, in the Germantown quadrangle, the South drainage basins of the Philadelphia district. paratively flat ocean bottom stretching awajr to the simple. Upon a floor of crystalline and indurated Valley Hills disappear and Buck Ridge becomes Of the total length of Delaware River (410 miles) east with but few and slight irregularities. fragrnental rocks, the submerged border of the the southern boundary of Chester Valley. This only 35 miles are included in the Philadelphia dis Seen from its base the abrupt slope leading up Piedmont Plateau, rest overlapping beds of uncon valley diminishes in width and depth toward the trict. It is navigable by ocean steamers to Phila to the continental shelf would have the appear solidated sediments having a southeast dip of a few east and then likewise disappears, and Buck Ridge delphia, 100 miles from the Delaware capes, and ance of a high mountain range with an even sky feet to the mile, uniform with the slope of the rock and the North Valley Hills merge in a broad high with a low-water depth of 5 feet to Trenton, 30 line, broken here and there by notches produced floor. The materials of these beds are bowlders, land extending to the northeast and passing on the miles northeast of Philadelphia. It is tidal to this by streams which flowed across the shelf when it pebbles, sand, clay, and marl. Their total thick northwest under the Triassic cover. point, 130 miles above the capes. Like all the was a coastal plain. ness varies from a maximum of 50 feet in the The northern part of the Philadelphia Piedmont, streams of the district which are without natural The Atlantic Coastal Province is divided into neighborhood of the "fall line" to 2250 feet near underlain by flat-lying sandstone and shale, is less storage reservoirs the Delaware is subject to con two parts by the present shore line a submarine the coast line. than half as large as the southern part, which is siderable seasonal fluctuation in volume. The con portion, known as the continental shelf, and a In age the formations range from Jurassic to characterized by well-defined ridges and valleys. ditions favorable to floods are those common to the subaerial portion, known as the Coastal Plain. In Recent. Since the deposit of the oldest formation The range of elevation is not great; the average district heavy rainfall on frozen ground, or rain some cases the dividing line is marked by a low there have been many periods of deposition alter height of land is from 380 to 400 feet, while the fall in excess of what the ground is able to absorb. sea cliff, but more often the two portions grade nating with erosion intervals. The sea advanced greatest altitude reached is only 480 feet, in the Somewhat less than one-third of the total length into each other without perceptible topographic and retreated differently in different parts of the neighborhood of Fairview village. This elevation of Schuylkill River, or 30 miles, lies within the change, separated only by the shore line. Their province, and therefore few formations can be con marks the top of a relatively low and vaguely Philadelphia district. Its drainage area comprises relative areas have frequently altered in geologic tinuously traced throughout the entire Coastal Plain. defined highland trending northeast and southwest. 1915 square miles. With headwaters in the time because of a shifting of the shore line east Unlike conditions thus prevailed synchronously in The more open, level character of the territory anthracite coal regions of Schuylkill County, the ward or westward, due to local or general depres distinct portions of the district and produced great underlain by Triassic formations, contrasted with Schuylkill flows across the Triassic formations and sions or uplifts. Such changes are in progress also diversity in the character and thickness of deposits the rougher topography of the southern part of the the Paleozoic crystallines of the Piedmont Plateau, at the present time. of a single period. A full representation of the Piedmont, in which the crystalline rocks are emptying into the Delaware at Philadelphia. From That at some period the entire width of the successive stages can be found within the Coastal uncovered, is very apparent from the summits of source to mouth the Schuylkill has a fall of about continental shelf was above water is shown by Plain, but can not be seen in any one section. the North Valley Hills, which separate the two 800 feet, or an average grade of 8 feet to the mile. the fact that old river valleys the continuation of Their general character and the distinctive terms parts -and command them both. - Most of this fall is above Reading. From Reading valleys of existing streams have been traced applied to them are given in the description of the That limited portion of the Coastal Plain which to Norristown, a distance of 41 miles, the >iver entirely across the shelf, in which they have cut geology of the Piedmont Plateau. (See pp. 3-8.) is included in the Philadelphia district lies wholly descends 141" feet, or 3^ feet to the mile. From deep gorges. The channel of Hudson River is within the Delaware watershed. The original Norristown to the Delaware, a distance of 18 miles, well defined, extending uninterruptedly to the TOPOGRAPHY. slopes of this portion of the plain were toward the the river descends 60 feet, or 3^ feet to the mile. edge of the shelf, more than 100 miles east of By F. BASCOM. Delaware basin, and erosion has not materially The divide between the Schuylkill and the the present mouth of the river. The same facts modified them. Its greatest altitude, which is in Delaware basins on the southwest is followed by BELIEF. have been observed for Chesapeake Bay, the con the extreme southeast corner of the district, is only the tracks of the western division of the Pennsyl tinuation of the Susquehanna channel. About three-fourths of the Philadelphia district is 180 feet above sea level, while in the neighbor vania Railroad Company. The Delaware water The combined width of the submarine and sub- within the Piedmont Plateau and about one-fourth hood of the Delaware the plain lies approximately shed is drained by Cobbs, Darby, Crum, Ridley, aerial portions of the Coastal Province is uniform is within the Coastal Plain. Delaware River marks at sea level. This surface of low relief and gentle and Chester creeks, simple consequent streams. along the entire eastern border of the continent, the boundary between the two provinces. slopes yet shows traces of two escarpments which Rising in the South Valley Hills, they pursue being approximately 250 miles. In the south the The Piedmont Plateau portion of the Phila separate areas with somewhat contrasting topog courses which are, in general, transverse to the subaerial portion expands to 150 miles, while the delphia district is more or less conspicuously divis raphy. These two escarpments correspond to the strike of the underlying rock formations and in submarine portion dwindles in width and along ible into northern and southern parts. These parts, first two escarpments on the west side of the the direction of the prevailing dip. Having an the eastern shore of Florida almost disappears. which are of nearly equal area, are distinguished by Delaware, but are less pronounced. The first average fall of 480 feet in distances of 16 to 20 Northward the submarine portion increases in unlike topographies: The topography of the south escarpment southeast of the Delaware occurs at an miles, they have cut rocky channels 200 feet below width, while the subaerial portion diminishes, ern part is largely controlled by Quaternary and elevation between 45 and 58 feet above sea level. the level of the Plateau. These four creeks pursue disappearing altogether north of Massachusetts pre-Triassic formations, while in the northern part At Morris the escarpment borders the marshes roughly parallel courses through a fertile and culti through the submergence of the entire Coastal the topography is controlled by Triassic formations. of Delaware River; at Fish House it is half a vated country. They possess drainage basins of Province. Off Newfoundland this province is From the flood plains of Delaware River the mile from the river. As it extends southwest approximately the same area, averaging in round about 300 miles in width. southern part rises by an abrupt wave-cut escarp it retreats eastward, reaching in the vicinity of numbers 30 square miles. 3
The streams north of the divide Valley, Trout, important part of a broad belt of similar material and biotite. The gneiss shows two facies : It may The clastic, finely banded gneiss lies on the Gulf, and Mill creeks, lesser tributaries of the which extends from Newfoundland -tp Alabama be either quite massive and granitic; or it may be flanks of the massive gneiss, from which its con Schuylkill, which enter it on the right bank and forms an important part of the Continental characterized by a more pronounced banding which stituents are considered to be derived by subaerial having a higher gradient and flowing against the Shelf east of the Appalachian region. The Phila is usually fine and intensely plicated the gneissic disintegration, and subsequently to be covered by prevalent dip, are contesting the divide vigorously delphia belt passes under a cover of Triassic sedi facies. The former type has wide distribution in the deposits of an encroaching sea, with little with the four southern creeks. ments at Trenton, and emerges at the surface in the areas northwest of the Philadelphia district, reworking by water. The alternation of mineral On the northeast the location of Germantown southeastern New York and in New England. while the more gneissic rock is relatively more constituents and the other evidences of sedimentary and Chestnut Hill marks the divide between In southwestern New England and in New important within the district. origin seem to preclude the possibility of its being Schuylkill and Delaware rivers. The Delaware York, the following successions of formations have The granitic facies varies from a light-colored, a flow gneiss peripheral to a massive central core. watershed is drained by Pennypack and Tacony been determined: almost pure quartz-feldspar rock to a dark-gray There is no means of estimating the thickness creeks. The Pennypack rises on the Triassic New England: rock in which garnets may be developed in pro of this formation, which is the floor upon which formations and flows across the ancient crystalline Ordoviciaii______.Berkshire schist. fusion, together with hornblende, biotite, and more the other sediments were laid down. rocks, and is therefore a composite stream. The Cambro-Ordovician __Stockbridge limestone. Cambrian ______Cheshire quartzite. rarely augite. The feldspars are orthoclase, albite, Correlation and name. The Baltimore gneiss Tacony is confined to the Paleozoic area,' Like Pre-Cambrian______Stamford, Becket, and other and oligoclase (Ab 2 An 1 ). The following analysis underlies material known to be of Georgian the streams on the southwest, their courses are gneisses. of the igneous facies of the Baltimore gneiss was ("Lower Cambrian") age. It is therefore pre- transverse to the trend of the rocks and in the New York: made by W. F. Hillebrand from a composite Cambrian and is correlated approximately with the Ordovician______-Hudson schist. direction of the prevalent dip. Their valleys do Cambro Ordovician _ _Stockbridge limestone or dolomite. sample collected from six localities: pre-Cambrian Stamford gneiss of western New not exceed 100 feet in depth. Cambrian ______Poughquag quartzite. England, the Fordham gneiss of New York, the Analysis of Baltimore gneiss. The chief tributaries of the Schuylkill are the Pre-Cambrian______Fordham gneiss. Baltimore gneiss of Maryland, and the Carolina, Perkiomen and the Wissahickon. The former is The belt extends southward through the eastern 8iO8 ZrO 8 ------______Trace. gneiss of the District of Columbia and Virginia. P8 0 5 ______.10 .confined to the Triassic rocks and has cut a valley half of the Piedmont Plateau of Maryland and Fe8 O3 ______1.03 Cl ______Not estimated. While the Baltimore gneiss of Pennsylvania is not 270 feet deep. The latter flows on both the Tri into Virginia and the District of Columbia. In FeO.______8.08 F_____ Not estimated. stratigraphically continuous with the Baltimore assic cover and the uncovered crystallines, and has Maryland the following succession has been pro MgO ______1.20 S______.09 gneiss of Maryland, similar stratigraphic relations, CaO ______3.10 NiO _---__ Faint trace. cut a gorge 160 feet deep. visionally determined: Naa O ______3.27 MnO ______.11 like lithologic character, and proximity of the two Perkiomen Creek, only the last 10 miles of which Ordovician_---______---_Peach Bottom slate. K 8 O ______2.69 BaO______.09 formations have found recognition in a common SrO ______Trace. is. included in the Philadelphia district, has its Cardiff quartz conglomerate. H 8O+ ______.48 name. The pre-Cambrian gneiss of Maryland has Mica schist or phyllite. H 8 0 ______.19 LioO ______None. source in the Blackhead Hills, which border on C0,______.11 Cambro-Ordovician ______Cockeysville marble. 100. 30 been called the Baltimore gneiss because of a fine the east the Greater Valley. Its watershed com Cambrian ______Setters quartzite. ______.52 exposure of it at Jones Falls Creek in the city of Pre-Cainbian______.Baltimore gneiss. prises an area of 447.59 square miles. The Per The norm may be calculated as follows: Baltimore. kiomen falls, from its source to the entrance of Farther south similar pre-Cambrian mica schist, The Baltimore gneiss includes H. D. Rogers's Northeast Branch, about 800 feet in 24 miles, and and mica gneisses have been described by Keith Quartz______30.06 Orthoclase, __ 16.68 Primal lower slate and a part of his northern or 40 feet from this point to its mouth, a distance of under the term Carolina gneiss. Albite ______27.77 third gneiss belt. The major part of the "third 11 miles. In Pennsylvania the belt shows a basement of Anorthite _ 15.01 gneiss belt" is gabbro. Both the Baltimore gneiss Diopside_____ The watershed of Wissahickon Creek separates igneous rock, a sedimentary series of arkosic, Hypersthene arid the gabbro are included by the Second that of the Perkiomen from that of the Little argillaceous, arenaceous, and calcareous character, Magnetite ___ 1.39 Geological Survey of Pennsylvania under the term Neshaminy. The Wissahickon rises near Mont- and intrusive igneous material both basic and acidic Ilmenite_____ .91 Laurentian gneiss. Pyrite ___ .18 gomeryville, at the extreme northern limit of the in character. The sedimentary rocks have been Apatite______.34 Philadelphia district, and pursues a southerly completely crystallized and indurated. The argil H 2 0 ______.67 WJSSAHICKOJST MICA GNEISS. .11 course for 20 miles, emptying into Schuylkill laceous and arkosic sediments have been con Distribution. The Wissahickon mica gneiss River at Fairmont Park. It is the most important verted into gneisses and schists, -the arenaceous 100. 83 extends from Buck Ridge to the Delaware River of the creeks entirely within the Philadelphia sediments into quartzites and quartz schists, and Under the quantitative system of classification the. ruck valley, where it passes under Cretaceous and Qua district. Its watershed is 646 square miles in area the calcareous material into crystalline limestone falls into Class I, order 4, rang 3, and subrang 4 a persalane, quardofelic, alkalicalcic, dosodic yellowstonose, which means ternary materials. It is also found in a narrow belt and is underlain partly by Triassic shales and and marble. Both the sedimentary and the igne that the rock is extremely rich in salic constituents, i. e., on the northwest side of Buck Ridge in the south partly by crystalline rocks. The creek has a fall ous formations have been subjected to tangential quartz and feldspars, that of these minerals the feldspars are western portion of the Norristown quadrangle. dominant, that of the feldspars the orthoclase and albite of 420 feet from source to mouth, or an average thrust from the southeast, which has produced molecules do not greatly exceed the anorthite molecules, and This belt rapidly expands west of the Philadelphia gradient of 21 feet to the mile. The upper courses longitudinal folds overturned to the northwest and finally that of the alkaline feldspars albite is more abundant district and eventually becomes continuous with the of the Wissahickon north of Chestnut Hill are in trending northeast, cleavage normal to the compres- than orthoclase. The structure of the rock is hypautomorphic, and biotite mica gneiss of the southeast slope of Buck Ridge. an open, shallow valley, which is part of an agri sive force, and fissibility both normal and diagonal and hornblende are abnormative minerals. Recognizing Both areas are intruded by large bodies of granitic, cultural country. The percentage of woodland is to the force. In the argillaceous material and in these facts in the name it becomes a biotitic hornblende gabbroitic, pyroxenitic, and peridotitic material. gran oyellowsto nose. small. From Chestnut Hill to its mouth, a dis some of the arenaceous, mica has been abundantly Character. The Wissahickon mica gneiss is tance of 6 miles, the stream has cut a rocky channel developed with its longest axis and cleavage plane The gneissic facies of the Baltimore gneiss is manifestly a stratigraphic unit, although possessing which lies about 200 feet below the general level of normal to the compressive force, thus producing characterized by a gritty feel and a pseudoporphy- an extremely heterogeneous character. This heter the:country and has steep, well-wooded slopes. either a schistose structure or a gneissic banding. ritic texture. To the alteration of layers of biotite ogeneity, which is both local and regional, together The streams of that portion of the Coastal Plain Which of these two secondary structures is produced with quartz layers or quartz-feldspar layers is due with the intimate association of an intrusive gran which is within the Philadelphia district are all is determined by the character of the other constit the finely gneissic character of the rock. Biotite ite gneiss, has led to its separation by former subsequent and tributary to the Delaware. Pen- uents and the amount of mica developed. occurs in minute plates, but is never developed in surveys into three belts -the "Chestnut Hill," sauken, Cooper, Big Timber, Woodbury, Mantua, The sedimentary rocks of the Plateau fall into such dimensions or in such excess as to render the "Manayunk" (chiefly an intrusive granite gneiss), Raccoon, and Oldmans creeks are simple streams, four divisions: rock schistose. Associated with the biotitic layers and "Philadelphia" gneiss belts. With variations having their sources in the Upper Cretaceous marls are hornblende, epidote, titanite, garnets, and which are indicated later, the formation as a whole Ordovician ______Octoraro schist. or on the border of the Miocene sands, and pursu Cambro-Ordovician ______Shenandoah limestone. more rarely staurolite or augite. Hornblende is may be described as a medium- to coarse-grained ing northwest courses, against the gentle southeast Cambrian______-______Chickies quartzite. sometimes as prominent a constituent as biotite, a ad, banded rock characterized by an excess of mica. ward dip of the marls, clay marls, and plastic clays Pre-Cambrian______i Wissahickon mica gneiss. ' Baltimore gneiss. like it, is arranged in layers. The* feldspar, like The chief constituents of the formation are quartz, of the Cretaceous, into the Delaware. Flowing on that of the massive type, is orthoclase and acidic feldspar, both orthoclase and plagioclase, green or unconsolidated materials with an average fall of Into the pre-Cambrian formations there have plagioclase of about the composition of oligoclase; brown biotite, and muscovite. Magnetite, apatite, only 8 feet to the mile, their valleys are shallow, been intruded great masses, sheets, and smaller in addition considerable mierocline is present. zircon, tourmaline, garnets, andalusite, sillimanite,, even in the upper courses, while in their lower bodies of igneous material granite, gabbro, pyrox- The apparently porphyritic texture is due to lenses and zoisite are accessory constituents. The more courses they are flat and marshy and their channels enite, peridotite, and diabase. The sedimentary of quartz and of feldspar,irregularly interspersed gneissic beds contain abundant orthoclase and plag are meandering. formations lie in belts traversing the district from along layers. These lenticular areas are without ioclase, which whenever tested prove to be an acidic- These streams range in length between 10 and the southwest to the northeast. The igneous rocks crystal boundaries, are rounded and pebble-like, variety between oligoclase and andesine(Ab 3 An 1 ). 16 miles, and are tidal for about half their total cut across these belts more or less irregularly, but and sometimes obviously suggest that the rock is a The. rock is perfectly crystalline and the constitu lengths. Owing to this fact they have little impor with a general northeast and southwest trend. metamorphosed conglomerate. The micaceous ents possess clear-cut boundaries-. The freshness of tance as sources of water supply and water power. SEDIMENTARY ROCKS. layers bend about them. - Rounded apatites are the crystallization and the absence of -pressure also present in the gneiss. PRE-CAMBRIAN ROCKS. effects upon the constituents indicate a recrystallized DESCRIPTIVE GEOLOGY. The fresh character of the crystallization and the sediment. , BALTIMORE GNBISS. PIEDMONT PLATEAU AREA. absence of pressure effects in the crystals, indicat The belt passing through Chestnut Hill and PKE-TRIASSIC METAMORPHIC ROCKS. Distribution. The Baltimore gneiss appears in ing that strain was relieved by recry stabilization, the Bryn Mawr is composed of beds which are alter the middle portion of the district and traverses it rounded apatite, quartz, and feldspar grains, and the nately micaceous and quartzose. Cleavage and By F. BASC-OM. obliquely to the northeast. It is very thoroughly sorting of the mineral constituents are microscopic jointing are conspicuous features of this belt, and GENERAL STATEMENT. injected by a gabbro gneiss, which, with the Balti evidences of a sedimentary origin. In the field on weathering the rock readily splits up into The old crystalline rock formations of the more gneiss, constitutes the flat-topped highland the gneiss has the appearance of a stratified rock. pencil fragments aptly likened by Rogers to "half- Philadelphia district, which are covered in the known as Buck Ridge. Northwest of Chestnut Both east and west of the Philadelphia district rotted fibrous wood." A yellow color, with Coastal Plain by gravels, sands, clays, and marls, Hill the gneiss belt is very narrow, although still the Baltimore gneiss contains considerable graphite, brownish-black stains on the joint planes, such as and in the northwestern portion of the Piedmont persistent, while to the southwest and to the which is disseminated in flakes, in presumably partly decayed wood exhibits, ^adds tcKthe resem Plateau by shales and sandstones, are uncovered, northeast it rapidly expands in broad uplands. pegmatitic injections. blance. The formation is also very garnetiferous, save for a few scattered outliers of these younger In the southwest it is bounded on both sides by The Schuylkill River section exposes both types especially in the neighborhood of the peridotite formations, throughout a broad central belt. This faults, and on one side only in the northeast. of the Baltimore gneiss. The formation shows intrusives, and for this reason has been known as belt, trending northeast and southwest, traverses the The formation is best exposed on the east bank anticlinal folding; steep dips prevail on the the "garnetiferous mica schist." Philadelphia district obliquely. It has a width of of Schuylkill River between Lafayette and Spring periphery (see fig. 10, illustration sheet), while in Even in this excessively micaceous belt the 12 to 20 miles, widening southwestward, and con Mill. the center the folds are gentle and open and the formation is not free from feldspar, and in the stitutes nearly one-half of the whole district. Character and stratigraphic relations. The rock is more massive. The major folding is from direction of Manayunk and Philadelphia massive The belt is a complex of highly metamorphosed Baltimore gneiss is a medium-grained, thoroughly southeast to northwest, and the minor folding from gneissic strata interbedded with micaceous and sedimentary and igneous materials, and is an crystalline aggregate of quartz, feldspar, hornblende, northeast to southwest. quartzose layers become increasingly prominent Philadelphia. and garnets are replaced by andalusite and silli- gorge of that stream it is called the Wissahickon which continued through Cambrian and Ordovi syncline 2 or 3 miles in width, striking to the manite. mica gneiss. cian time. It is also conceivable that pegmatization northeast across the central portion of the Pied Within the contact zone of the most northerly The mica gneiss contains within itself no clue to may have occurred in connection with the intru mont division. of the serpentine dikes on the south flank of Buck its age, which must be determined wholly on the sions of Devonian and Carboniferous granites Ridge the mica gneiss has locally been altered to stratigraphic relations that the formation, appears which are found in the Appalachian Mountains CHICKIES QUARTZITE. a muscovite schist. It contains large lustrous areas to sustain with sediments that are correlated with far to the south. Distribution. The hard, resistant formation of muscovite which have won for it the designation fossil-bearing material. These stratigraphic relations and igneous associ known as the Chickies quartzite constitutes the "spangled mica schist." It is siliceous, light In northern Delaware and in the southwestern ations indicate that the Wissahickon gneiss is, North Valley Hills, the highlands at Hickorytown colored, coarsely crystalline, and splits readily. part of Chester County, Pa., the formation is in part at least, older than the Chickies quartzite, and Coldpoint, the hills west of Whitemarsh, Fort The mica gneiss on the northwest flank of Buck found in association with crystalline limestone and that to the southeast it often supplants the Hill, Camp Hill, the highland about Willow Ridge is adjacent to the Octoraro schist, from which and quartzite. While most of this limestone Chickies quartzite. There was some micaceous- Grove, and the long ridge known as Edge Hill it is distinguished with great difficulty. It becomes lies southeast of the main mass of Shenandoah argillaceous sedimentation during Cambrian time, and Lafayette Hill, also the hill that bounds the increasingly like the mica schist in the neighbor limestone of Chester Valley, the rock perfectly as shown in the Atglen section, in the gradation of northwest side of Huntington Valley. hood of that formation, losing completely the resembles that formation and a series of the expo mica gneiss into quartzite elsewhere, and in the Character. The Chickies quartzite usually gneissic character which characterizes the rock sures is in line with the strike of those in Chester passage of quartzite into rnica gneiss parallel to the shows a conglomeratic lower member, which is elsewhere. Valley. There is also a quartzite associated with strike in still other localities. Yet both north and largely composed of elongated pebbles of the blue On the whole, the gneiss is separated from the the limestone which resembles the thin-bedded south of Pennsylvania, sedimentation in earlier quartz that characterizes the pegmatites and some schist by the possession of a coarser crystallization. sandy material of the Chickies and, like it, contains Cambrian time was dominantly arenaceous. In facies of the Baltimore gneiss. This lower member The muscovite of the gneiss occurs in patches of broken tourmaline crystals. No fossils have been consideration of this fact, the Wissahickon gneiss, of the quartzite is not often exposed. One mile relatively considerable size, which gives to the found in either formation, but because of their probably representing originally many thousand south of Morganville and an equal distance east of rock a spangled appearance not possessed by the lithologic resemblance to recognized Paleozoic feet of scantily arenaceous sedimentation, is Willow Grove it is brought to the surface in the finer grained smooth fissile mica schist. Elsewhere rocks and their similar stratigraphic relations they assigned to pre-Cambrian time. Subaerial erosion end of a pitching syncline. It is also exposed at in this northwest area, removed from the vicinity are held to represent Cambrian and Cambro- of the mica gneiss subsequent to the deposit of sand the base of the North Valley Hills near the dam of. the mica schist and near igneous intrusives, Ordovician sediments. in an encroaching sea will explain the apparent at Valley Forge, where it is brought up on the garnets, staurolite, and tourmaline are developed; In all of the exposures of mica gneiss and lime gradations of the mica gneiss into the quartzite, limb of an anticline. The conglomerate passes these minerals, together with large muscovite crys stone the gneiss overlies the limestone. It is while the thin and lenticular character of lower upward into a gray, compact, crystalline quartzite, tals, make a rock type easily recognized. sometimes separated from the latter formation by Cambrian sediments to the east will explain the which, in turn, grades into a siliceous slate or a As shown by analysis the rock has a chemical thin beds of quartzite, but frequently is found in apparent passage of quartzite into gneiss along sericitic quartz schist, or is altogether supplanted composition which, while it resembles that of a immediate contact with the limestone. If the the strike. by the quartz schist. shale, is not of a decisive character. The high obvious stratigraphic relations of gneiss and lime As has been indicated, the Wissahickon gneiss The sericitic quartz schist, or so-called itacolu- alumina and low alkali percentages and the pre stone were the true relations, the Wissahickon occurs in extensive areas southeast of the Buck mite, is typically exposed in quarries half a mile ponderance of magnesia over lime, shown by the mica gneiss would be Ordovician in age. That, Ridge axis, and toward the south, overlapping this northeast of Somerton station and in the Edge Hill analyses, are characters common to siliceous argil- however, the superposition of the gneiss is only highland, is found immediately in contact with quarries. Here it is thin bedded. Bedding and lites, while in feldspar-bearing rocks of igneous apparent, while its actual stratigraphic relation is outlying Paleozoic rocks; but northwest of Buck schistosity coincide and dip steeply southeast. origin, on the other hand, lime dominates the that of an underlying formation, is presumed to Ridge the Wissahickon is missing and the Paleo The quartz schist is of a light buff to white color magnesia. The analyses permit, however, the be the case on the following field evidence: zoic formations immediately overlie the Baltimore and always contains feldspar. The feldspar is for calculation of norms, and fall into line with the 1. Within and west of the Philadelphia district gneiss. the most part orthoclase, more rarely microcline, quantitative system of classification of igneous Wissahickon gneiss is adjacent for 50 miles to This peculiar distribution compels one of two and is usually more or less kaolinized. Tourma rocks. recognized Ordovician mica schist. While in prox assumptions: Either there was land area during line, apatite, zircon, magnetite, and staurolite are Analyses of Wissahickon mica gneiss. imity to the latter formation, the mica gneiss shows Wissahickon time in the west while the Wissa accessory constituents. "Stretched" or broken a very close resemblance to the mica schist, making hickon was accumulating in an eastern sea, or tourmaline is so constant and characteristic a con 2. 3. it difficult to separate the two formations, yet a there was a subsequent abruptly defined uplift in stituent of the Cambrian quartzite, not only in the separation can be made, and is made, on the basis the west which permitted pre-Cambrian erosion to Philadelphia district but throughout the Pied Si03 ______56.40 66.13 73.68 of the greater nietamorphism of the.mica gneiss as cut deeply into the mica gneiss, removing it com mont Plateau that it is a guide in the identification A1.O 3 _ 19.76 15.11 12.49 Fe 2 O 3 _ -- _ - 4.35 2.52 2.10 exhibited in a more coarsely crystalline texture. pletely on the northwest, so that when subsidence of the formation. The schist readily splits into FeO ______4.40 3.19 2.22 It is true that crystallinity increases eastward in initiating Paleozoic sedimentation occurred Cam flattened rhombohedrons whose faces are parallel to MgO 3.11 2.42 2.04 all the formations, but this change in grain or brian sand was laid down first directly upon the planes of schistosity and fissility. Locally the CaO.__ .09 1.87 .56 crystallization seems sufficiently abrupt to indicate Baltimore gneiss and later, as the sea encroached quartzite may contain many geodes lined with Na2O ______5.82 2.71 2.97 a different arid older or pre-Ordovician formation. on the land, upon superficially decayed Wissa quartz crystals. Quartzite of this character occurs K 2 0 ______1.27 2.86 2.91 2. The structure of the limestone exposures hickon gneiss. This deposition to the east may at a locality known as Diamond Rock, on the H 2 0+ ______j 1.55 [ 3.37 j- 1.34 have taken place in bays or estuaries, and later in H 2 O ______( .24 permits the interpretation that they are over southwest flank of the North Valley Hills. CO2 ______None. turned synclines, or in some cases fan-shaped enlarging bays or estuaries where the Cambro- Thirty miles west of the Philadelphia district a TiO 2 1.05 .82 .81 synclines, in the troughs of which limestone is Ordovician limestone accumulated. This material, section through the Chickies quartzite shows Zr0 3 ______-__-.___ Not est. left by erosion. This structure puts the gneiss both pre-Cambrian and later sediments, was subse a considerable thickness of micaceous feldspathic P2 0 B ______- .37 .22 .12 below the limestone. quently folded, metamorphosed, faulted, and thrust material interbedded with the quartzite. Such 01 _ __ Not est. 3. The presence of tourmaline-bearing quartzite upon the western Paleozoics. In the Philadelphia beds occur as the uppermost member of the series, F Not est. S _ _ __ .03 between the limestone and the Wissahickon gneiss district the Cambro-Ordovician material which separating typical quartzite from the overlying c
rock. The phenocrysts range from one-half inch Age. Because of the relation which the granite the underlying rock. The gabbro bowlders are has been included in the "Third gneiss belt" or to 1^ inches in length. The chief constituents of sustains to gabbro and to serpentine, an alteration extremely tough, except along contacts with the the "Laurentian gneiss." the rock are quartz, feldspar, biotite, and horn product of a basic intrusive, the granite is held to gneiss, where the development of hornblende and Metagabbro dikes. Penetrating the Baltimore blende. Muscovite may also be present, but is not be the oldest of the pre-Paleozoic intrusives./ mica renders the rock more schistose and more gneiss and the Wissahickon gneiss are numerous as characteristic a constituent as is biotite. The North and west of Lansdowne considerable easily attacked mechanically. basic dikes which have been altered to hornblende feldspar is chiefly orthoclase and microcline and masses of gabbro have invaded the granite and Character.- The gabbro is a medium-grained schists. Many of them are distinctly connected subordinately oligoclase (Ab 6 An 1 ). Accessory con altered it along contact zones. massive rock, possessing a bronzy gray or a green with the great gabbro intrusive, and presumably stituents are titanite, apatite, epidote, and actinolite. Between Glen Kiddle and Lenni Mills the Wil- ish gray color, the shade depending on the fresh there is connection when it is not obvious. The rock shows the result of pressure by the pres mington and Baltimore Central divisions of the ness of the ferromagnesian constituents. Quartz, Such dikes occur 1|- miles south of Ithan on ence of microcline structure, by the granulation Pennsylvania Railroad afford a section through pyroxene, and feldspar may be determined in the Ithan Creek, one-half mile north of Ithan, one-half of the feldspar, by the granulation of quartz, and by granite and serpentine. Both rocks are greatly hand specimen. Further study shows the gabbro mile southeast of Villa Nova, in the Schuylkill the orientation of the constituents. Along the con decomposed, but the facts indicated by the section to be typically a hypersthene-augite-plagioclase section near Spring Mill, one-half mile north of tacts with the bounding rock (mica gneiss), an injec seem to be that the granite is the older intrusive and rock with accessory quartz, biotite, hornblende, Bryn Mawr station, on Crum Creek in Willistown tion gneiss has been produced by the penetration that the serpentine cuts through the granite and lies magnetite, apatite, titanite, pyrite, pyrrhotite, gar Township, parallel to Crum Creek in the neighbor of the acidic magma parallel to planes of fissility in on top of it as a sheet. The relation of the outcrop net, and orthoclase. Decomposition products are hood of Swarthmore, on Chester Creek near the mica gneiss. of granite and serpentine to the topography also actinolite, chlorite, and serpentine. Quartz is an Ridgewater, on Rocky Run in Middle-own Town In the Pennsylvania Railroad cut 1-J- miles south indicates that the latter rock overlies the granite. extremely variable constituent, ranging, where ship at Edgemont in Edgemont Township, at Val east of Overbrook station a contact facies of the HORNBLENDE GNEISS. present, from a trace to 30 per cent. The ley Falls station on Pennypack Creek, near granite gneiss is exposed. The porphyritic granite pyroxenic constituent may be exclusively or chiefly Verreeville on the same creek, at Ogontz, and at passes abruptly into a close-grained, aphanitic, In the eastern part of the Philadelphia district hypersthene, when the rock becomes a norite, or other localities. tough, light-gray rock which breaks with a there is a large body of hornblende gneiss whose less frequently chiefly augite (hypersthene gabbro) These dykes vary in width from 1 to 100 feet. conchoidal fracture. Quartz, feldspar (bytownite areal distribution is concealed by a covering of or exclusively augite or diallage, when the rock is While the larger dikes are more or less massive, the Abj An g ), colorless augite, and titanite are the chief younger materials. Quarries on the outskirts of a typical gabbro. The pyroxene constitutes from narrow ones are thoroughly schistose, and in all of constituents. The texture is microgranulitic. The Frankford near Chelten avenue, Germantown, and 10 to 40 per cent of the rock. them hornblende is the prevailing constituent. exposure is about 500 feet in width; no other an exposure on Pennypack Creek north of Holmes- The feldspathic constituent is labradorite or Feldspar, chiefly plagioclase, and quartz, scanty exposure of this type has been found. This may burg, reveal the character of the material. It is labradorite-bytownite, and varies in amount from and in part secondary, are the other essential con be a dike; if, on the other hand, it represents a also penetrated by the shafts and tunnel of the 5 to 60 per cent of the rock. Between the stituents. Apatite, titanite, biotite, magnetite, contact zone, the more 'rapid cooling and earlier Torresdale filtration plant. The contact of the pyroxene, whether hypersthene or augite, and the abundant garnets, and pyrite are accessory constit crystallization which would characterize the periph hornblende gneiss and the Wissahickon mica gneiss labradorite there occur reactionary peripheral zones uents. Secondary constituents, in addition to ery of the intruding granite may explain the finer was seen in this tunnel. The hornblende gneiss cuts of garnets. On the inner margins of the garnet quartz and hornblende, are actinolite, anthophyllite, grain and more basic character of the contact zone. across the structure planes of the mica gneiss and rims there may be a narrow zone of quartz and zoisite, epidote, chlorite, and muscbvite. Along the lower courses of Ridley and Crum sends apophyses into the mica gneiss. The char hornblende. These garnet rims are a persistent That hornblende, which usually occurs in fresh creeks the rock is nonporphyritic, of an even acter of this contact and the constitution of the and striking petrographic feature of the gabbro. green blades with a parallel arrangement of the medium grain, light colored, and is characterized rock, indicate an intrusive igneous origin. The (See figs. 18, 19, illustration sheet.) Wherever the longer axes, is an alteration product from pyroxene by the presence of both micas. rock is medium grained and dark colored, owing to gabbro has been subjected to pressure, as along the is proved by the presence in some cases of an unal This granite gneiss has not been separated by the prevalence of hornblende. This constituent is periphery of the intrusive mass, pyroxene has tered augitic core surrounded by hornblende. The the previous surveys from the "Manayunk" and dark green and is arranged with the longest axes been replaced chiefly by green hornblende and feldspars are twinned, granulated, or altered to "Philadelphia" gneisses. parallel, thus producing the gneissoid structure. subordinately by biotite and quartz. (See fig. 20.) zoisite, epidote, muscovite, and chlorite. The following two analyses have been made of The other constituents are quartz, orthoclase, mi A more or less schistose structure was produced by An analysis, made by W. F. Hillebrand, of a the granite at Port Deposit, Md., where there is a crocline, oligoclase, biotite, titanite, and apatite. the development of these two minerals. In the specimen from a dike of metagabbro occurring 1 southwestward extension of this intrusive body. The structure is granulitic and gneissoid. Owing intruded rock (Baltimore gneiss), hornblende is also mile north of Bryn Mawr station, is as follows: to the excess of hornblende the rock is darker developed along the intrusive contacts and accom Analyses of granite from Port Deposit, Md. a Analysis of metagabbro dike, Roberts road, Bryn Mawr. colored than the granitic intrusive on the west side panies biotite as a constituent of the gneiss. This 2. 1. of Schuylkill River. It is otherwise not unlike it Si08 __- __ 48.68 P2 0 5 ______0.29 contact phenomenon increases the difficulty of A18 08 ______14.39 Cl___ _ Not estimated. SiO,:- ______73.69 66.68 and may be genetically related to the granite. separating the gabbro and the gneiss. The gabbro Fes O3 ______4.00 T'__. _ Not estimated. A1S 0 3 ______12.89 14.93 The stone, which is extensively quarried at Frank- is associated with, and through decrease in feldspar FeO __ ___ 10.09 8 ______Trace. MgO 6.32 Cr3 O 3 ___1_____ None. Fes 0 3 1.02 1.58 ford, has been used for building purposes and for grades into, pyroxenite, or with the addition of CaO 9.23 NiO ______Trace. FeO 2.58 3.23 bridge abutments. olivine into peridotite. Na3 O______2.31 MnO ___-_- _ '.22 2.19 MgO ______.50 An analysis of the gabbro, made by W. F. K8 0 .47 BaO__ ___ Faint trace. CaO 3.74 4.89 GABBRO AND ALLIED ROCKS. H 8 O+______2.03 SrO ______None. NaB 0 2.81 2.65 Hillebrand, from a composite specimen represent H»O ______.46 Li8 O Trace (?). Distribution. A formation including gabbro, ing three localities, gives the following oxide per TiO8 ___ _ 1.69 K2 0 1.48 2.05 ZrO3 _-___ Not estimated. 100.18 H 8 0+ j 1.09 hypersthene gabbro, and norite constitutes a great centages : | 1.06 C0 3 ______None. HS O 1 .16 igneous body which intrudes itself into the crystal Ti08 _ ,.50 Gabbro from the neighborhood of Radnor and The norm is given below : line rocks of the Atlantic border from Virginia to of Bryn Mawr. PoOr .10 New York. It is an important formation in Mary Quartz______2. 82 MnO_ _ _ - .10 land, Delaware, and southeastern Pennsylvania. Si08 54.03 ZrO3 __--Not estimated. Orthoclase ______-_ __ -_ 2.78 BaO .08 A18 0« 16.71 PS0 5 ______0.13 Albite ______-_ 19.39 SrO ___ Trace. It invades alike pre-Cambrian Baltimore gneiss and Fe2 0 3 - 1.37 Cl _ - -Not estimated. Anorthite______....___ 27. 52 F______Not estimated. Hypersthene _____. ______21.78 Li2 0 Trace. Wissahickon mica gneiss. In the Philadelphia FeO_------.--_---_ 7.70 MgO______5.66 S ______.09 Diopside - _ _ _ 13.67 99.77 100. 23 district its maximum development is in the south CaO___ - 8.84 Gra O3 ______Trace. Apatite ______.67 west. From this section it extends northeast, Na2 0 __- _ - 2.99 NiO------Trace. Magnetite ______5.80 MnO ______.13 Ilmenite ______3.19 "Grimsley, GK P. Jour. Cincinnati Soc. Nat. His., vol. 17, forming the main mass of Buck Ridge, where it KS 0 .67 H3 0+ _ .53 BaO ______Trace. H B O ___ 2.49 1894, pp. 88, 89. shows itself at the surface in exceedingly irregular SrO --_--_ Trace (?). 1. Biotite granite or quartz moiizonite. Analysis by Wil H30-__ .14 100.11 Li3 O ___-____Trace. liam Brownell, Johns Hopkins University. areas. It is intimately associated with the Balti Ti02 _ .84 2. Hornblende-biotite granite or quartz monzonite. Anal more gneiss and has so affected this gneiss along CO2 -_ - .40 100.23 The rock falls into Class III, order 5, rang 4, subrang 3 i. e,, ysis by W. F. Hillebrand, United States Geological Survey. it is an auvergnose. Like the gabbro mass to which it is prob - contacts as to produce an appearance of gradation The norm according to the quantitative classifi ably genetically related, it is perfelic, docalcic, and presodic, These analyses give the following norms: from banded gneiss to massive' gabbro. Many though it is slightly more basic, the femic constituents being cation would be as follows: equal to the salic. This is the chemical relation which dikes instructive exposures of gabbro and Baltimore often bear to larger intrusive bodies from the same parent 1. 2. Quartz______4.56 gneiss show the intercalation, along the periphery Orthoclase______3.89 magma. The dikes, representing later intrusions, are, because Albite ______25.68 of differentiation, either more acidic or more basic than the 41.28 27.84 of the gabbro mass, of the gabbro between the Anorthite ______. ______30.30 earlier intrusives. Orthoclase _ 8.90 12.23 folded beds of the gneiss. The penetration of the Hypersthene ______20.67 Albite 23.58 23.06 gneiss by the gabbro is irregular, thin sheets swell Diopside______10.52 METAPY.ROXENITE, METAPERIDOTITE, AND RELATED ROCKS. 18.07 22 24 ing into larger masses which weather into rounded Apatite______.34 Distribution. More or less intimately associated .25 1.30 Ilmenite__-______----____-_---______-_____ 1.52 bowlders on exposure. Magnetite ______...______2.09 with the Atlantic belt of gabbro are altered pyrox- 5.13 8.80 Because of this peculiar injection of the gneiss Pyrite ______. ______.24 enites and peridotites, or metapyroxenites and meta- Magnetite _____.. _ _ 1.39 2.32 H 8 O _ .67 .91 by the gabbro, gabbro bowlders may appear sporad CO 2 ______.40 peridotites. These are the serpentines and allied .34 rocks. Serpentines of such origin are found in the ically in areas where gneiss is the prevailing 100. 88 * H 8 0 1.06 1.25 formation at the surface, and vice versa. Piedmont belt of North Carolina, Virginia, Mary The rock therefore falls into Class II, order 5, rang 4, 99.76 100.45 At Glen Mills, a few rods south of a large quarry subrang 3, and is a hessose. This means that the salic, or in land, Delaware, Pennsylvania, New York and the in gabbro, an abandoned quarry shows a composite this case the quartz feldspar, constituents are dominant and New England States. the femic or ferromagnesian constituents subordinate. Of These norms show that the more acidic facies of the granite In the Philadelphia district there are four belts of gneiss and gabbro, yet the gneiss does not the salic constituents feldspar predominates to an extreme from Port Deposit is a biotite granosusquehannose (Class I, appear as a surface formation. It is therefore degree and lime-soda feldspar with dominant lime is the pre of interrupted lenticular exposures of serpentine order 3, rang 3, subrang 4). This means that the salic or vailing feldspar. Augite is the only abnormative mineral quartz-feldspar constituents preponderate; that quartz and impossible,' in drawing the boundaries of these two and closely related rock types, trending northeast among the essential constituents of the rock, and it usually feldspar are present in nearly equal amounts; that of the formations, not to include some gneiss within the plays the role of a critical mineral. The texture of the rock and southwest. Two of these belts are on the south feldspars the alkali molecules are equal to the lime molecules; is hypautomorphic, granular; it may therefore be designated that of the alkalies soda is dominant; and finally that the gabbro area, while gabbro may be seen within east flank of the gabbro; one belt lies within the texture is megascopically hypautomorphic granular, and that the gneiss areas in rock cuts, though not prevailing an augitic granohessose. gabbro area, and the fourth belt lies on the north the only abnormative mineral present in the rock is biotite. at the surface. This is particularly true of the Age. The youngest material into which the west flank of the gabbro. All of these belts con The more basic facies falls in Class II, order 1, rang 3, sub- rang 4. Like the susquehannose it is dosodic and alkalicalcic, areas northwest of Media. The two formations gabbro has been found to intrude is the pre-Cam tinue southwestward into Delaware and Maryland. but differs from the other facies in the fact that the salic have not before been separated. They alike give brian Wissahickon gneiss. The gabbro is, there The areas that have been mapped under this minerals are merely dominant, not preponderating, and that feldspar is dominant over quartz. rise to a relatively elevated rolling country with fore, pre-Cambrian in age. Its relations to the heading are by no means underlain by serpentine The texture of the rock is hypautomorphic granular; bio irregular rounded eminences. Dark-colored bowl granite indicate that the granite is the earlier exclusively, nor even by rocks in which serpentine tite is the only abnormative mineral present and is a critical ders of disintegration with rusty exteriors strew intrusive. By the previous surveys the gabbro has is the predominating constituent. In some localities mineral. According to the quantitative classification the rock is therefore a biotite granotonalose. the fields and afford almost the only indication of not been separated from the Baltimore gneiss and the serpentine has been completely removed and 7 only siliceous ironstone or ".honeycomb rock" The second dike upon the southeast flank of the direction. The thickness of the sediments is great, RELATIONS IN PHILADELPHIA DISTRICT. remains. In other localities serpentine is scarcely gabbro mass extends from the east bank of the but as yet has been determined only approximately, GENERAL OUTLINE. developed and pyroxenite or peridotite is the under Schuylkill to 2 miles southwest of Chester'Creek. and only in portions of the belt. The great width The rocks of the Newark group occupy an area lying material. In still other localities talc, antho- It widens southward, reaching a maximum width of territory in which there are monoclinal dips of about 230 square miles extending across the phyllite, or chlorite is the prevailing alteration of 1-J- miles. There are numerous scattered out would indicate a vast succession of sediments, but northern portion of the Philadelphia district. Most product producing a soapstone, an anthophyllite crops southeast of the main areas. longitudinal faults cause frequent repetition of the of the rocks of the group in this region are com rock, or a chlorite schist. The occurrence on the As in the case of the first dike, contact meta- outcrops of the series. paratively soft sandstones and shales, forming val tributary to Green Creek 1^ miles southwest of morphism has affected the surrounding rock. The Age. The Newark group is believed to be of leys and rolling hills varying in altitude from about Chelsea is a pure anthophyllite-steatite rock, in Wissahickon gneiss has been altered to an actino- later Triassic age and possibly it includes the 70 to 485 feet. The most prominent topographic which the former mineral occurs in larger radiating lite schist or to a spangled muscovite schist or has earlier Jurassic, but its precise equivalency is not feature is a ridge which rises about 200 feet above crystals. A great variety of minerals, in addition become excessively garnetiferous. Petrographically established. Fossil plants, crustaceans, and verte the lower hills north of Norristown and which is to or replacing serpentine, may develop from the the rock shows alteration from an original type brates have been collected and compared with due to the increased resistance to erosion offered by alteration of the basic ignepus rocks. which differed from that of the first dike in the similar forms from European deposits of those ages, the hard beds of the Lockatong formation. At Talc, asbestos, anthophyllite, tremolite, horn possession of a larger amount of pyroxene and a and they correspond within general limits, but the southern margin of the group the older rocks blende, actinolite, epidote, chlorite, clinochlore, smaller amount of olivine. This original rock type correlation of exact horizons is not practicable. rise along a line which, in general, trends east-west vermiculite, pectolite, magnetite, hematite, limonite, seems to have been a pyroxenite in which enstatite The Newark rocks did not share in the folding but presents considerable sinuosity. Southwest calcite, breunnerite, magnesite, quartz, (especially was the prevailing pyroxene. Associated with the which occurred at the close of the Carboniferous of Norristown there are two small outliers of the drusy quartz), chalcedony, opal, chromite, and serpentine are enstatite, tremolite, and anthophyl period, and therefore must be of later date, and Stockton formation lying on the limestone. This corundum have been found associated with the lite in abundant development. The usual accessory they are clearly older than the earliest Cretaceous irregularity of margin is due in part to unequal serpentine of the Philadelphia district. constituents are present. formations, which overlap them unconformably in erosion and in part to undulations in the floor of Topography and soil. Serpentine country, even The third dike has few exposures. The most Maryland and southward. They are thus separated older rocks. South of Norristown it is evident that though so limited in area as in the Philadelphia conspicuous of them is located southeast of Edge- from earlier and later deposits by intervals of there were low hills and shallow valleys in the pre- district, has certain marked and characteristic fea mont. Here the rock lies piled up in picturesque upheaval and erosion of unknown but great dura Newark land surface. Originally the Newark sed tures. The areas underlain by serpentine stand masses which have won for the locality the name tion, and their position in geologic history can not iments extended farther toward the south, but they out in relief as low ridges. The rock, though very Castle Hock. (See fig. 6, illustration sheet.) Ser be determined more closely than by the general have been removed by erosion, except the two soft, is exceedingly stable chemically under atmos pentinization and steatization are not far advanced correlation of fossils above indicated. outliers southwest of Norristown. There is no pheric conditions, hence weathering leaves it in in the main mass of Castle Rock, which still shows special topographic evidence as to the original limits, NEWARK GROUP. relief. For the same reason the rock mantle, the character of the original rock, an augite-enstatite and the line of steep slopes extending along the the product of weathering, is scant or absent, rock or pyroxenite. Associated with this pyrox By N. H. DARTON. south side of the limestone valley westward from and rock lies close to the surface and crops out in enite is a pure green serpentine. DISTRIBUTION A]STD SUBDIVISION IN SOUTHEASTERN Conshohocken, is due to a fault. The thickness of PENNSYLVANIA. many places. In areas of the less-altered perid The serpentine of the fourth or most northwest the Newark group in this district is very difficult to otite, the material weathers in huge bowlders, erly intrusive extends with disconnected outcrops The Newark group in Pennsylvania occupies a estimate, for, although the altitude of the beds is which strew the ground. Where the peridotite from " the Gulf" south west ward. South of Paoli broad belt extending across the southeastern portion relatively uniform, probably there are so many has been completely altered to serpentine the it expands into a considerable area, which is con of the State from Delaware River to the Maryland faults that thicknesses calculated from dip arid surface of the ground is covered with flat frag tinuous to West Chester and has a sporadic exten line south of Gettysburg. It is 32 miles wide on breadth of outcrop are unreliable. The section ments broken along joint planes. The thin soil is sion into Maryland. The State line follows for the Delaware, 12 miles on the Susquehanna, 4 miles from Valley Forge northward up Perkiomen Creek of a light-green color, like the rock. On relatively several miles one of the more considerable out in northern Lancaster County, and 14 miles at the to the northern margin of the district indicates a low land, where the soil possesses greater depth, it crops ; for this reason the belt of rocks has been Maryland line. It is bounded by shales, limestones, thickness of more than 13,000 feet as calculated is of a deep-red color due to the oxidation of the commonly known as the State Line serpentines. sandstones, quartzites, mica schists, gneisses, and from the dips, but numerous small faults were iron silicate. The rock of this dike is chiefly a massive dark- granites, varying in age from Ordovician to observed which, with others not detected, should Serpentine soil, because of its thinness and be green or a light-green granular serpentine. Fibrous pre-Paleozoic, which it overlaps along irregular reduce this estimate. Normal faults are seen in cause of the magnesia which it contains, is not a serpentine is associated with it, also talc, quartz, boundary lines. In some portions of the area its every extensive exposure of the rocks, but their fertile soil, and vegetation on serpentine areas is magnetite, and limonite. The microscopic texture margin is determined by faults, but these marginal total number and amount of displacement could therefore scanty and of a peculiar character. The of the serpentine indicates that the original rock faults appear not to be extensive either in throw or not be ascertained. moss pink (Phlox subulata) covers the ground in type was olivinitic i. e., a peridotite. in length. Over wide areas the dips are to the The rocks of the Newark group have yielded but such profusion as locally to give the name Pink The genetic relationship of the metapyroxenite north and northwest, but in some districts there are very few traces of life in the Philadelphia district. Hill to some of the serpentine ridges. Cedars, and metaperidotite to the gabbro is to be seen (1) flexures of moderate amount and extent. The In the dark shale of the Lockatong formation, in scrub oak, and cat brier are very characteristic of in the petrographic character of the original types group is traversed by numerous normal faults, tunnels near Phoenixville and Gwynedd, a number the serpentine country, which usually presents a and (2) in the field relations which the serpentine mostly extending northeast-southwest and with of fish scales and reptilian remains were found by wild and barren aspect. sustains to the gabbro. The petrographic character downthrow on the east side of the fault plane. One Lea and Leidy. Numerous remains of Cypris were Character. Of the four belts or dikes the most shows it to be a differentiation product of the gabbro of these extending through Bucks and Montgomery found in the Gwynedd tunnel, and Lea has reported southeasterly, which extends from Bryn Mawr to magma; the field relations show it to be either counties has a vertical displacement of several fish scales and caudal rays in red shale near Yerkes Chestnut Hill, lies wholly in the Wissahickon peripheral in character or a subsequent intrusive thousand feet. station which resemble Radiolepis elegans Emm. of gneiss, but is presumably an offset from the main in spaces left by the contraction of the cooling In the rocks of the Newark group in south the "Chatham series" of North Carolina. Plant mass. Both the field and the petrographic char gabbro. eastern Pennsylvania, as in other regions, the impressions are reported from the middle beds of acters of the rock are those of an igneous intrusive. Age. The limitation of the serpentine dikes to typical red-brown sandstone and shale predom the Stockton formation at Fort Washington and The interrupted character of the exposures, the pre-Cambrian material, the field relations of the inate, and there are igneous rocks in intrusive sheets below Norristown, and carbonized plant fragments variation in width of the belt, the massive nature serpentine and the granite elsewhere described, and and dikes. The classification which has been estab are noticeable at many points. Dinosaurian tracks of the rock, the contact phenomena, and the dis the genetic associations of serpentine and gabbro lished in New Jersey is applicable here, and com have been found in ripple-marked shale of the placement of the mica gneiss which have accom show that the serpentine is pre-Cambrian, younger prises three formations the Stockton, Lockatong, Brunswick on Landis Brook, 1|- miles northwest of panied its intrusion are field evidences of an intru than the granite and contemporaneous with or and Brunswick, the last named being the youngest. Graters Ford. Two species are represented. Silici- sive origin. Petrographically the rock shows its somewhat subsequent to the gabbro. A series of names proposed by the Pennsylvania fied wood collected by E. T. Wherry from Stockton alteration from the igneous type, peridotite, an Geological Survey has not been found acceptable beds in railroad cuts north of Morganville and a oli vine-pyroxene rock. It is in general character TRIASSIC KOCKS. because of their indefinite application. mile northeast of Churchville proves to be a new ized by the remains of olivine crystals, by serpen GENERAL STATEMENT. The Stockton formation comprises gray to buff species of Dadoxylon (Araucarioxylon). tine, which is often the chief constituent of the By N. H. DARTON. arkosic sandstone, red-brown sandstone, and numer STOCKTON FORMATION. rock, by steatite which is an alteration product Extent. The Triassic rocks described in this ous masses of red shale, in no regular succession both of the original pyroxenite constituent and folio are a representative portion of an occurrence and presenting many local variations in stratig General character. The rocks of the Stockton of the serpentine and may be developed in crys of the Newark group which extends from Hudson raphy. It lies on gneiss, schist, quartzite, and formation are partly coarse sandstone and partly talline form (talc) or as a massive constituent, River southward through New Jersey, Pennsyl limestone, in Montgomery, Bucks, and northern red shale, the two alternating in bodies so irregular and by calcite, quartz, and the iron oxides. vania, and Maryland into Virginia. Other detached Chester counties. Many of the sandstones are that the stratigraphy is extremely variable. At The last three constituents, not' only occur in areas are found in Nova Scotia, Connecticut, Mas cross-bedded, and the finer grained rocks exhibit many horizons in the formation occur bodies of subordinate amount to the serpentine as by sachusetts, Virginia, and North Carolina. The ripple marks, mud cracks, and raindrop impres sandstone alternating with masses of bright red- products of serpentinization, but as the final belt of occurrences is thus more than 1000 miles sions, which indicate shallow-water conditions dur brown shale. Some of these sandstones are mod products of alteration they may constitute the long, but the areas are now widely separated and ing deposition. The lower beds usually are arkose erately hard and regular in texture and are used for entire rock mass. Breunnerite is also sometimes may never have been directly connected. a sandstone containing more or less feldspar and building stone, especially for rough work. present as a by-product. Constitution and structure. The Newark rocks kaolin derived from the gneiss. The Lockatong Lower and middle beds. Sandstones are of Locally the rock varies greatly. In some local in general are remarkably uniform in character. formation consists mostly of dark-colored, hard, general occurrence along the southern margin of ities, notably near Lafayette on both sides of the They comprise great thicknesses of alternating sand compact, fine-grained rocks originally composed of the formation, and lie on the older rocks. They Schuylkill, it is a fairly pure, gray-green steatite stones and shales, in larger part of reddish-brown a mixture of clay and fine sand in variable propor are usually arkosic, consisting of coarse quartz (soapstone); in others (near Mill Creek) it is a color, in which are intercalated sheets and dikes of tions. Some beds are moderately massive, others sand, which in many places includes numerous massive blue-green serpentine or a reddish-yellow igneous rocks. Many of the sheets are intrusive, vary from shaly to flaggy, and many of them quartz or quartzite pebbles and fragments of more siliceous rock; in still others (Black Rock quarry) but others, in New Jersey and in the Connecticut exhibit mud cracks and other evidences of shallow- or less decomposed feldspar. Mica and other the original rock type can still be traced. In this Valley, are unmistakably contemporaneous lava water deposition. Some of the beds contain car minerals are present in small proportion, as well as case - dark-green serpentinized olivine crystals mot flows. The structure of the strata is monoclinal bonaceous material. The Brunswick shale consists variable amounts of clay of white to red color. tle the light-gray steatite which forms the body of over wide areas, with faults having the upthrow mainly of a great thickness of soft, red shale with Some of the rock is a sandy conglomerate, and the the rock. Penetration twins of olivine, producing mainly on the side toward which the strata dip. some thin sandstone layers. coarser constituents comprise many fragments of cross and stellate forms, have been found in this From New Jersey southward this monocline in These three formations are not sharply separated the underlying older rock, the beds along the belt. (See fig. 21, illustration sheet.) The forma greater part slopes westward at angles of 10° to 15°, by abrupt changes of materials, but usually merge quartzite contact containing numerous quartzite tion is penetrated by a network of joints and on while in New England and Nova Scotia, and at through beds of passage which appear to vary some pebbles and fragments. Cross-bedding is rather the joint planes a blue-green opaline serpentine is some of the easternmost outcrops in Virginia and what in thickness and possibly also in strati- general and the layers are thick and irregular. The sometimes deposited. North Carolina, the inclination is in the opposite graphic position in different areas. colors are mostly gray, but buff, purplish, and red- Philadelphia. 8 dish tints are frequent. Many of the rocks are LOCKATOJiTG FORMATION". sediments. A part of this formation extends across Analysis of rock of Conshohocken dike. loosely consolidated and crumble quickly when General character. The second member of the the northwest corner of the Philadelphia district. SiO2 ______51.56 exposed to the weather. Exposures of these basal Newark group consists of fine-grained deposits, It consists of several thousand feet of red shale con A18 O 3 ______17.38 Fe3 03 _-______6.57 beds are numerous all along the southern margin of mostly of dark color and considerable hardness. taining here and there beds of reddish-brown sand --______3.85 the formation, but one of special clearness is in the Much of the rock, in its unweathered condition, stone. Some of the shales contain considerable MgO ______3.42 Trenton cut-off of the Pennsylvania Railroad 1^ CaO______10.19 is a very compact fine-grained sandstone of dark sand admixture, and there are also included some Na2 O -__-______L______- 2.19 miles southeast of Fort Washington. Long rail bluish-gray color, in beds from 1 inch to 6 inches inconspicuous thin local deposits of gray, brownish, KS 0 ______1.46 road cuts and old quarries along the north side of thick. The original material was a sandy clay. and greenish shales. In the railroad cut at Yerkes Loss______. ______2.15 TiO 2 ______1.63 Schuylkill River west of Norristown afford good Some of the beds are of lighter color, or become so station concretions of the size of a hickory nut and P0 4 ______.13 exposures of some of the middle and lower beds of on weathering. Many layers of dark shale occur, smaller are rather abundant in the Brunswick shale. Li2 O_-______Trace. the formation. There are extensive exposures about and at some localities, especially in the upper por The rocks are soft and the region which they 100.53 Morgan ville. tion of the formation, there are bodies of light- underlie is a general valley with hills having low This analysis gives the following norm: Upper sandstones. Sandstone beds occurring gray, brown, and red shales. A short distance slopes. The rocks are frequently exposed in road Quartz______13.44 toward the top of the formation present the most south of North Wales 200 feet or more of red shale cuts and low bluffs along the streams, but there are Orthoclase ______8.90 uniform grain, even texture, and regular bedding Albite______12.56 and sandstone appear to be included near the top many areas in which the soil covers the underlying Anorthite______36.42 and have been the source of supply for much of the formation, a feature which continues for some material. The region is a fertile one, and nearly Enstatite ______8.50 building stone for local use and in some cases for distance to the east and west. A similar body of all of it is occupied by productive farms. Wollastonite______5.57 Apatite ______.34 shipment. One of the freshest exposures of sand red shale is also seen at Doe Run. Usually when IGNEOUS ROCKS. Ilmenite ______3.04 stone high in the formation is in the quarry on red shales are included in the formation they are Hematite ______7.89 By F. BASCOM. the opposite side of the Little Neshaminy from of slightly darker color and of harder texture than ELO ______2.15 Grenoble station. The upper limit of the Stockton those in the adjoining formations. DIABASE. formation appears not to be clearly denned, as the Distribution and thickness. The Lockatong for The intrusion of igneous material which charac The rock therefore falls into Class II, order 4, rang 4, sub- next succeeding formation begins by a gradual rang 3 i. e., it is a dosalane bandose. This indicates close mation extends across the Philadelphia district in terized the Triassic period and which manifests itself similarity to gabbro, differing chiefly in the relation of the change in character of the sediments, probably not a belt which averages about 3 miles in width north to the north in the great diabase masses of Mount feldspar to the other salic constituents. Feldspar is dominant everywhere at the same horizon. of Norristown and east of North Wales, but nar Holyoke, Mount Tom, and the Palisades of New over quartz, but not to an extreme degree. Well sections. A boring 102 feet deep near rows locally on Wissahickon Creek and diminishes York and New Jersey shows itself in this district COASTAL PLAIN AREA. Stony Creek in Norristown, passed through the gradually toward the west, being only about a mile in a few dikes not exceeding 60 feet in width. By W. B. CLARK, H. B. KtiMMEL, and B. L. MILLER. following beds of the Stockton formation: wide north of Port Providence. These lesser widths One of these dikes has been known as the Con- GENERAL STATEMENT. Record of well 'boring near Stony Creek in Norristown, Pa. are due partly to increase of dip and partly to shohocken dike, because of a prominent outcrop decrease in thickness. East of Perkiomen Creek The geologic formations of the Atlantic Coastal Thick of it in that town This exposure is pictured in ness. Depth. the apparent thickness is somewhat over 3000 feet, fig. 12. The dike has been traced continuously Plain represent a nearly complete sequence of without making allowance for faults. deposits from later Jurassic or early Cretaceous to Feet. Feet. from Lafayette Hill to "the Gulf" and thence inter Made ground 15 15 Topography. Owing to the fact that the Locka mittently into Maryland. It has a width of about Recent. They form a series of thin sheets which Sandstone, light colored, coarse grained, tong formation is much harder than the adjoining are inclined slightly to the southeast, so that suc containing fragments of orthoclase feld 30 feet. The rock exhibits a very uniform char spar 23 38 sediments, it gives rise to a ridge of some promi acter, weathering in bowlders which are readily cessively later formations are generally encountered Sandstone, dull red, fine grained, with nence and the larger valleys are constricted into in crossing the Plain from its inland border to the specks of muscovite ; color due to iron recognized by a rusty-yellow oxidized coat and a oxide 33 71 canyons in crossing it. greenish-gray color and conchoidal fracture on coast. (See fig. 9, p. 17.) Variations in the angle Sandstone, light pink (produced by pink Local features. There are extensive exposures and direction of tilting, as well as later denudation, orthoclase), fine grained ; quartz grains fresh surfaces. The rock is a comparatively fresh, transparent; fine specks of muscovite along Perkiomen Creek, and the formation is medium-grained, typical diabase. Plagioclase and have occasioned in some places marked divergences mica_ . . 31 102 exhibited in nearly complete cross section in the pyroxene in about equal amounts are its primary from these normal conditions. These variations, Another well at Norristown passed through the deep cuts and tunnel of the Philadelphia and essential constituents, and ilmenite, quartz, and however, are most pronounced along the western following beds: Reading Railroad between North Wales and Hoyt apatite are accessory. The secondary minerals are margin of the belt, where, as the result of trans Record of well 'boring at Norristown, Pa. stations. In the principal excavation along this chlorite, scanty biotite, calcite, and epidote. The gression, it is not uncommon to find one or more railroad west of Gwynedd more than a thousand plagioclase, which is labradorite-bytownite, forms formations lacking in a given district. As a result Thick ness. Depth. feet of beds are exposed, consisting mainly of dark- a network of automorphic lath-shaped crystals. of denudation detached outcrops likewise appear gray to dark-buff fine-grained sandstone with shale The pyroxene, which is the aluminous monoclinic along the western margin of the several formations, Feet. Feet. Cased at 28 feet with 6 -inch pipe. layers. Several masses of dark-red sandstone and variety augite, is xenomorphic and fills the inter some of them far removed from the main body of Sandstone, very white and fine grained, shale are intercalated, as are numerous layers of stices of the feldspar network. the deposits. These various factors must of course containing a little pink orthoclase 30 30 dark-reddish fine-grained sandstone. Some of the be worked out for each individual district, and their Sandstone, white, containing coarse frag Another diabase dike extends northeast and south ments of orthoclase 5 35 shale layers contain considerable carbonaceous ma west in the neighborhood of Dreshertown, Jarret- relations in the Philadelphia district will be dis Shale, dark red 41 terial. In these cuts the beds are traversed by town, and Warminster. It is exposed in a cut on cussed on subsequent pages. Sandstone, white, containing muscovite__ 14 55 numerous faults, which are described under "Struc the Pennsylvania Railroad north of Camp Hill, Sandstone, lighter color, more feldspathic 10 65 tural geology" (p. 17). CRETACEOUS SYSTEM. Sandstone, very white, fine grained 3 68 where its width is 55 feet. It cuts across the beds Sandstone, dark red, coarse, containing A cut in the southern portion of the village of of the arkosic sandstone on a plane dipping about The Cretaceous deposits of the Philadelphia dis much iron oxide and a little mica- 6 74 North Wales exhibits 100 feet or more of fine 70° W. Here it does not seem to have appre trict represent portions of both the Lower and the Shale, red _ 4 78 grained buff to brown and gray sandstone and gray, ciably affected the sandstones, but shale traversed Upper Cretaceous. Still older Cretaceous deposits Sandstone, red, fine, micaceous 18 96 buff, and dark greenish-gray shale. These appear have been recognized beyond this district to the Shale, red _ 4 100 by it exhibits for several feet a darker color and to be underlain by several hundred feet of red sand increased hardness. south in Maryland and Virginia, and still younger A well drilled on top of Sandy Hill, Norristown, stones and shales exposed in the next cut south, but Some stray bowlders of the rock appear on Cretaceous deposits to the north in Burlington and which passed through Stockton beds, is reported as it could not be ascertained whether these beds are Camp Hill, and although the dike can not be Monmouth counties, N. J. In general the Upper follows: in regular succession in the formation or whether traced continuously in the Paleozoic area, it .is Cretaceous formations are best developed in New the dark beds north are brought up from the main Jersey and the Lower Cretaceous in Maryland and Record of well boring on Sandy Hill, Norristown, Pa. probably the continuation of the Conshohocken mass of Lockatong sediments by a fault. In most dike. Virginia. Thick The'Lower Cretaceous deposits of estuarine origin ness. Depth. portions of the district the summit of the Lockatong Toward the north it cuts diagonally across the formation is clearly defined by an abrupt change entire area of the Stockton formation, trending due were described by McGee as the Potomac formation, Feet. Feet. from dark fine-grained sandstones or shales to the northeast to a short distance beyonfl the Bucks- although they are now known to represent several Sandstone 56 56 Dark- red shale 6 62 red shale of the next succeeding formation. It is Montgomery county line and thence nearly north stratigraphic units. As the type of deposition was Red shale, micaceous 6 68 possible, however, that this change does not take to its end, just north of the northern margin of the much the same through the entire series of forma Sandstone, light-colored transparent place at the same horizon throughout. district. Throughout its course it crosses the strike tions, the name Potomac group is retained to desig quartz, abundance of silvery muscovite _ 2 70 Quarries. The Lockatong beds have been quar of the Stockton formation. Its width probably is nate them as a whole. Of the four formations into Red shale 5 75 White sandstone, muscovite, quartz, and ried to some extent, mainly for road metal, for which variable and at some points it may possibly be which the Potomac group is divided only two, the pink orthoclase 7 82 they are admirably suited. The largest quarry discontinuous for a short distances. Its course is Patapsco and the Raritan, are known with certainty Pink sandstone, more pink orthoclase_ 2 84 is a mile and a quarter southeast of Montgomery marked by rounded masses of diabase lying on the to occur in the Philadelphia district. Overlying White sandstone, finer grained _ 2 86 Square, where a steam crusher has been established. surface of the ground. These masses vary in size the Raritan formation are transitional beds that;" White sandstone, orthoclase, quartz, very little mica 5 91 Another quarry in the upper beds of the formation is from less than an inch to 2 feet in diameter and from their fossil remains at more northern localities, Red shale, no mica 4 95 half a mile northeast of Montgomery Square. The are ordinarily of an ocherous-yellow color on the have been referred to the base of the Upper Cre Red shale, slightly micaceous . 5 100 beds have a slabby character, which weathering surface. This color, which is due to iron oxide, is taceous. The deposits themselves contain materials Red sandstone, fine grained 2 102 brings out, and afford useful material for under limited to a thin layer of soft, decomposed material that ally them in part with the overlying and in Gray sandstone, little mica. 2 104 Light-red sandstone, orthoclase, quartz, pinning and fences, for which the rock is exten under which there is extremely hard, dark-gray, part with the underlying formations. They were and muscovite _ 8 112 sively employed. fine-grained rock. Many of these bowlders have evidently marine in the vicinity of Raritan Bay, White sandstone, feldspathic. 2 114 Equivalency. The Lockatong formation is been collected by farmers and used for fences, road but no marine fossils have been observed to .the Red shale _ .. 2 116 nearly equivalent to the Gwynedd shales of B. S. metal, and other purposes, which in some areas has south of Burlington County, and it is evident that Red sandstone, feldspathic ._ 9 125 White sandstone, very fine grained, little Lyman, of the Second Geological Survey of Penn given them a wide distribution along the roads. they were estuarine from that region southward mica, feldspar absent 5 130 sylvania. Apparently, however, the term Gwynedd Locally they are found a mile distant from the into Maryland. They have been designated the Dark-red sandstone, micaceous. 5 135 has been applied to a considerable but variable dike, but in all such places they appear to have Magothy formation. Dark-red sandstone, slightly micaceous ___ 5 140 thickness of beds of passage in the adjoining for been carried from their original position. The Upper Cretaceous deposits of strictly marine White sandstone like that at 130 feet ; re sembles sea sand 5 145 mations; at least it is so mapped as to include por The^rock of this dike is of the same petrographic origin were referred to by the older writers as the White sandstone, very fine grained, only tions of them. type as that of the Conshohocken dike and exhib "Clay marls" and the "Greensand marls," the little feldspar 5 150 Pink and white sandstone, orthoclase, its like constituents and texture. mineral glauconite occurring in greater or less and muscovite 10 160 BRUNSWICK SHALE. An analysis of the rock of the Conshohocken amounts in all of the formations. The lithologic Pink and white sandstone, muscovite, and more orthoclase . 9 169 The name Brunswick has been employed in New dike, made by F. A. Genth, jr. (Second Geol. Sur features of each formation are in general sufficiently Jersey for the entire upper portion of the Newark vey Pennsylvania, Report C 6, p. 134), is as follows: distinctive and persistent, however, to render the 9 determination of the several horizons, even in the of dicotyledonous plants not known positively to face upon which they were laid down. At the yielded a considerable flora and a marine fauna. absence of fossils, a relatively easy task. Three exist in beds earlier than those of the Cretaceous, outcrop the thickness it is evidently from 200 The animal remains described by Weller a were groups of formations, the Matawan, the Monmouth, and the similarity of other Patapsco organic forms to 300 feet, but this increases toward the southeast found mainly in smooth concretionary nodules in a and the Rancocas, are recognized in the Philadel to well-known types of Lower Cretaceous age in beneath the later formations, and in places has clay bed or lying loose on the beach, where they phia district. They will receive further considera European horizons, have caused the, reference of been penetrated in well borings to a depth of more were left by the erosion of the clay beds that orig tion on later pages. the Patapsco formation to the Lower Cretaceous. than 500 feet, although part of the latter may inally contained them. The fauna is characterized It probably represents a part of the Neocomian- represent the Patapsco and possibly even the by the presence of great numbers of crustacean LOWER CRETACEOUS DEPOSITS. Albian series of European geologists. Patuxent formation. Owing to the cover of remains. In almost every instance some portion of POTOMAC GROUP. Stratigraphic relations. The Patapsco outcrops Quaternary materials, only a small part of the a crab seems to have been the nucleus about which The Potomac group of the Coastal Plain consists previously mentioned, although numerous through Raritan is represented by outcropping strata in the nodule was formed. Pelecypods, gasteropods, of highly colored gravels, sands, and clays which out the district of their occurrence, are discontinu the Philadelphia district. and cephalopods also occur. The most abundant outcrop along a sinuous line that extends from New ous and small. They occupy depressions, probably Name and correlation. The Raritan formation forms are the pelecypods Trigonarca triquetra, Leda York to Richmond, passing near the cities of Phila holes of solution, in the crystalline limestones. was named by Clark from the typical development cliffwoodensis, Pteria petrosa, Nucula percrassa, delphia, Wilmington, Baltimore, and Washington. This relation is well shown in a large limestone of the deposits in the valley of Raritan River. Yoldia cliffwoodensies, Isocardia cliffwoodensis, In Maryland, where the Potomac deposits are best quarry about 1^- miles northeast of Conshohocken. As first used the term included the beds now classi Cymbophora lintea, Corbula bisulcata, and among developed four formations have been differentiated As previously stated, in some places in this region fied as Magothy. The flora, of the Raritan is the Crustacea Tetracarcinus subquadratus. These from below upward, the Patuxent, the Arundel, the the lowermost beds of Potomac materials may highly characteristic, with its large proportion of are of considerable importance for they are the Patapsco, and the Raritan. The two older forma represent the Patuxent formation, but the data are dicotyledonous forms, and affords the basis for a earliest marine fossils found in the deposit of the tions, of questionable Jurassic affinities, are not insufficient to determine this point. correlation of the deposits on paleontologic grounds. Atlantic Coastal Plain. Weller states that the known to occur in the Philadelphia district. Within the region under discussion Quaternary Prof. L. F. Ward is of the opinion that the Raritan assemblage of forms constitutes a distinct faunule of strata only are seen to overlie the Patapsco beds, flora represents for the most part the late Lower 43 species, of which 14 do not occur in other forma PATAPSCO FORMATION. but many well records about Philadelphia indicate Cretaceous and is therefore approximately equiva tions in New Jersey. Of the remaining 29 forms Areal distribution. The Patapsco formation in the presence of the Patapsco beneath the Raritan, lent to the Gault of England. E. W. Berry, on which have a wider range, a larger number occur the Philadelphia district has been recognized only a relation which is well exhibited in places in the other hand, suggests the possibility that the in the Woodbury and Wenonah formations than in in Pennsylvania, where it is represented by out Maryland. So far as observations have been made, flora is Cenomanian, and thus, perhaps, Upper the Merchantville, which immediately overlies the liers in the vicinity of Conshohocken, to the north unconformities separate the Patapsco from all the Cretaceous. Magothy. and northeast of that place in the valley of Ply formations, both below and above, with which it Stratigraphic relations. The Raritan formation The flora of the beds at Cliffwood Point & is mouth Creek, and to the northwest in small patches comes in contact. rests uncoriformably either on the floor of crystal notably varied, more than 80 species having been extending nearly to Valley Forge. With the line rocks or on the Patapsco deposits. This con described by Berry. Many of the species occur exception of one or two isolated localities still BARITAN FORMATION. tact has been reached in numerous well borings also in the Raritan formation, but most of them are farther north these are the last occurrences of the Areal distribution. The Raritan formation along the western margin of the formation. new or are characteristic of later formations else Patapsco formation in the North Atlantic region. occupies a belt along the valley of Delaware River, The Raritan is unconformably overlain by the where. The most common fossil plants of that Toward the south the deposits become more fre but for the most part it underlies the river or is Magothy formation, and where outcrops at the con locality are the imperfectly petrified cones of Sequoia quent until they finally merge into the main body covered by Quaternary deposits on the New Jersey tact are found the line is for the most part sharply gracillima. Other common species are Cunning- of the formation in Maryland and Virginia. side of that stream. The best exposures are those defined, although an exception to this appears when hamites squamosus, Dammara cliffwoodensis, and It is quite probable, however, that the Patapsco at the base of the sand pits north of Morris station. dark-colored carbonaceous beds occur at the top of Sequoia reichenbachi. Berry and Hollick state formation underlies the Raritan near the southwest A single outlier occurs at Media, in the hill con the Raritan. that the flora of the beds at Cliffwood Point show ern border of the quadrangle, where it is concealed taining the reservoir, near the northern limits of In the Philadelphia district the Raritan forma Cenomanian characteristics, while Weller has beneath the Quaternary cover, as an extensive out that town, where a deep pit has furnished an tion lies for the most part at low levels along the pointed out that the fauna is more like that of crop occurs a few miles farther to the south, near excellent section. valley of the Delaware, where it has been covered the Senonian. Wilmington, Del. Some of the well borings in the The Raritan formation continues beyond the by Quaternary deposits, which have obscured over Thickness. The thickness of the Magothy for vicinity of Philadelphia, notably those at League limits of the quadrangle along the valley of wide areas its contact with the crystalline rocks and mation is about 40 feet, but it increases toward the Island, also penetrate beds apparently of Patapsco Delaware River to the region of Trenton and other formations below and above. This is particu north, reaching about 80 feet on the shores of age, and in a few instances even reach strata that thence across New Jersey to Raritan River and larly true of its basal contact along the western Raritan Bay. Farther southward it thins and in possess many of the characteristics of the underlying beyond. To the south it extends across Delaware bank of the Delaware, where, for much of the dis southern Maryland is not more than 20 to 30 feet Patuxent formation. The very deep depression at to the headwaters of Chesapeake Bay in Maryland tance, the presence of the Raritan can be determined in thickness. League Island, which is perhaps the extension of and thence southward to the valley of Potomac only from well borings. Name and correlation. The Magothy formation, the ancient Schuylkill channel, furnishes an unusual River, where it finally disappears beneath the The deposits strike northeast and southwest and so called by Darton in 1893 from the typical section of pre-Raritan deposits that can with diffi cover of later deposits. The outcrops are more have a dip of about 40 feet in the mile to the development of the deposits in the valley of culty be referred in their entirety to the Patapsco extensive in New Jersey than toward the south and southeast. Magothy River, Maryland, can be traced almost formation. the late Cretaceous and Eocene deposits gradually continuously, except for the cover of Quaternary UPPER CRETACEOUS DEPOSITS. Lithologic character. The materials consist transgress until they come in turn to rest directly materials, from the valley of Raritan River south mainly of the highly colored clay so characteristic upon the Patapsco formation in southern Mary MAGOTHY FORMATION. ward to the western shore of Chesapeake Bay. It of the Patapsco formation farther south. This is land and Virginia. Areal distribution. The Magothy formation changes somewhat in character toward the south, ferruginous and plastic to a marked degree and Lithologic character. The character of the occurs as a narrow belt to the east of the Raritan and the marine fossils of the north have not thus commonly rests on a basal bed of yellow sand Raritan materials is somewhat variable, consisting formation but does not outcrop continuously in the far been observed south of Burlington County, which may possibly represent the Patuxent forma chiefly of light-colored sands and clays, the former Philadelphia district. It overlies the Raritan clays N. J., although the alternating clay and sand with tion, although in the absence of more conclusive in places so highly ferruginous that they form a in Hylton's pits on Pensauken Creek, New Jersey, their lignitic beds persist. A more or less constant evidence such reference would be unwise. No out firm ironstone. In general the deposits are not and in several of the streams that reach Delaware characteristic of the clays is the presence of iron crops of this sand have been found, but highly highly colored or variegated like those of the River from the New Jersey bank. The best nodules, many of which are fossiliferous. arkosic beds occur with the clay at Henderson. Patapsco formation. exposures are in Hylton's sand pits and at Red The flora of the Magothy presents a much more These arkose deposits are also like the Patuxent They are commonly very variable in composition, Bank on Delaware River. recent aspect than that of the Raritan. Only 37 formation, though their relations to the clay are the sandy layers being often replaced within short The Magothy formation extends as an almost per cent of Raritan forms have been described from such as seemingly to preclude such a correlation. distances by beds of clay. Cross-bedding is fre continuous belt from Raritan Bay to the District of the Magothy formation, and these are not of the Paleontologic character. The organic remains of quent in the sands and no section can be considered Columbia, where it disappears beneath the cover of oldest and most characteristic type. Many later the Patapsco are neither plentiful nor varied. The as typical except within very narrow limits. In later deposits. forms appear and the flora as a whole is regarded only remains of animals thus far discovered are a the vicinity of Raritan River, where the most com Lithologic character. The Magothy deposits are by paleobotanists who have examined and described single dinosaurian bone, found on the west side of plete section of the beds has been found, there is an highly variable, consisting of alternating beds of the specimens collected as showing Cenomanian Chesapeake Bay, probably redeposited from the evident preponderance of clays in the lower and of dark clays and light sands, the latter in places red affinities. Arundel formation, and a few molluscan shells. sands in the upper half of the formation. dish or brownish. The clay beds are commonly The fauna consists mainly of marine molluscan The vegetable remains are more numerous and Paleontologic character. The fossils of the lignitic, and near Raritan Bay, where they carry shells, crab claws, and shark teeth. It is the low have been found at many localities. The forms Raritan formation consist largely of plant remains a large marine fauna, some of them are slightly est appearance of a fauna which recurs in the identified belong to the ferns, cycads, conifers, which have been recognized in many different glauconitic. The carbonaceous clays are in Woodbury, Wenonah, and Redbank; Weller con monocotyledons, and dicotyledons. Of the last a localities in New Jersey. The known flora of the many localities filled with minute fragments of siders that it possesses close affinities to that of the few only have been found as compared with the formation includes about 170 species, including one lignite which give the materials a somewhat spotted Ripley formation of the South, and that it is thus number collected from the next younger formation. thallophyte, ten ferns, six cycads, eighteen conifers, appearance. The clays are locally micaceous allied to the Senonian of Europe. Thickness. The thickness of the small outliers and one monocotyledon, the remainder being dico and not unlike some of the overlying Matawan Stratigraphic relation. The Magothy formation often exceeds 40 feet, but at no point can an ade tyledons distributed among many genera, some of materials. overlies the Raritan formation unconformably, quate idea of the full thickness of the formation be which still exist. Within the area of the Phila Segregation of the ferruginous matter, usually although the contact is not commonly observed on gained, as the deposits are not overlain at any delphia quadrangle fossil plants have been found somewhat evenly distributed through the sand, has account of the extensive cover of Quaternary mate point by the next younger or Raritan formation, in the upper part of this formation at the extreme occurred in several places, producing irregular iron rials along the western margin of the Coastal Plain. except in the deep-well borings, where the limits of base of the section at Hylton's pit, from which crusts, with many fantastic shapes. These are well To the south the Matawan transgresses the Magothy the formation can not be satisfactorily determined. Berry -has identified the following species: Andro shown near the east end of Hylton's pits and at Red and rests upon the Raritan, but in New Jersey local Name and correlation. The Patapsco formation meda parlatorii, Aralia quinquepartita, Aralia Bank. sections show no evidence of any break in sedi receives its name from Patapsco River, Maryland, rotundiloba, Cinnamomum intermedium, Eucalyptus Paleontologic character. In this district the only mentation, and there is no distinct indication of in the valley of which stream it is typically devel attenuata, Ficus woolsoni, Laurus plutonia, Lirio- organic remains thus far recognized in the Magothy any overlap. oped. The name was proposed in 1897 (Jour. dendropsis simplex,-Sequoia heterophylla, and Wid- are leaf impressions in the drab clays that occur in The deposits generally strike northeast and sputh- Geology, vol 5, pp. 479-506), after careful strati- dringtonites reichii. The known fauna is very thin laminae alternating with layers of sand. These west and have a dip to the southeast of about 40 graphic work had shown that the deposits formerly limited, consisting of a few Mollusca, a plesiosaurian are mostly fragmentary, but careful search would feet in the mile. included in the Potomac formation were readily bone, and possibly an insect. doubtless reveal the presence of identifiable forms. "Greol. Survey New Jersey, Paleontology, vol. 4, pp. 33-42. separable, on the basis of unconformities and fossil Thickness. The thickness of the deposits is At Cliffwood Point, on the south side of Raritan 6 Bull. New York Bot. Gard., vol. 3, No. 9, pp. 45-103; Bull. contents, into four distinct formations. The remains somewhat variable, on account of the irregular sur Bay, New Jersey, beds of this formation have Torrey Bot. Club, vol. 31, pp. 67-82 ; vol. 32, pp. 43-48. Philadelphia. 10
MATAWAIST GROUP. Stratigraphic relations. The Merchantville clay Stratigraphic relations. The Woodbury forma tenuistriatum are prominent species which are recur The strata included in the Matawan group have rests upon the Magothy and is overlain by the tion rests upon the Merchantville and is overlain rent from the Merchantville; the most conspicuous been regarded by Clark as constituting a single Woodbury clay, with which it is conformable. by the Englishtown, with both of which it is con characteristic fossils, however, constitute a new formation, composed of two members, the Cross- The base of the Merchantville clay is a sharply formable. Like the other Cretaceous formations of element, which persists in the recurrent fauna of wicks clays and Hazlet sands. To this formation marked stratigraphic line, readily recognized wher the district, the Woodbury in the region of its out the Mount Laurel and Navesink. Weller, in Clark gave the name Matawan because of the typical ever exposed and easily traceable throughout the crop is in many places unconformably overlain by Paleontology of New Jersey, volume 4, 1907, page Quaternary deposits. 88, savs: deposits of this age along Matawan Creek in Mon- entire area in which it outcrops. The underlying ' V mouth County, N. J., but the geologists of the New Magothy strata consist of loose, coarse lignite- ENGLISHTOWN SAND. This element is represented most conspicuously by the Jersey State Survey have subdivided it into five bearing sands or finely interlaminated sands and ponderous species Exogyra and Gryphcea, by the little parts, which are regarded as distinct formations for clays, with the upper sandy layers not infrequently Areal distribution. The Englishtown sand in oyster O.falcata, which is of the type of 0. larva, and by this district. The fifth formation, the "Wenonah, cemented to form an. ironstone. The contrast the Philadelphia district appears as a series of out Grypliasostrea vomer. Besides these oyster-like forms though paleontologically distinct from the overlying between those materials and the overlying Mer crops extending from Ellisburg to Swedesboro. In which so strongly characterize the Marshalltown and the Mount Laurel, is not sharply distinguished from chantville black marly clay or its weathered equiv its wider distribution it has been recognized from Favesink, some other species should probably be included in the same faunal element, among which are the follow it lithologically, and is therefore combined with alent is striking. The contact of the Merchantville the Atlantic Highlands to Salem County, N. J. ing species which are as yet known only from these two that formation in the Philadelphia district for and Magothy formations is exposed on Pensauken Owing to the generally loose, incoherent character faunas: Plagiostoma erecta, Unicardium umbonatum, and mapping purposes and will be discussed in con Creek a mile north of Maple Shade station, and at of the materials composing the formation, fresh Odontofusus medians. To these should also be added, in nection with the Monmouth group. Farther south, the clay pits near City Line station, Camden. The exposures are speedily washed down and obscured. all probability, Tigonia thoracica, which has been recog in Delaware and Maryland these distinctions grad upper contact of the Merchantville clay is much It outcrops on the banks of Cooper Creek at Had- nized in both the faunas and also in the intermediate ually, disappear and the Matawan strata finally con less distinct, but the transition to the overlying donfield and along Beaver Brook near Bellmawr, Wenonah, where, however, only a single occurrence of a single individual has been observed. stitute a single unit of very constant lithologic Woodbury strata is generally accomplished within and forms the surface over considerable areas south character. 1 to 3 feet, and where exposures are fresh there is west of Woodbury. Thickness. Along its outcrop the thickness of The five formations in New Jersey which are rarely any question as to where the division between Lithologic character. This member of the Mata the Marshalltown formation is about 30 to 35 feet, believed to be the correlative of the single Matawan the two should be made. wan group is a conspicuous bed of white or yellow but this increases toward the southeast to at least 50 formation of Maryland are the Merchantville, and In much of the region of its outcrop the Mer quartz sand, slightly micaceous and with minute feet, as shown by a well boring at Grenloch. Woodbury clays, the Englishtown sand, the Mar- chantville is unconformably overlain by deposits amounts of glauconite. It is in some places marked Name and correlation. Marshalltown, Salem shalltown formation, and the Wenonah sand, all of Quaternary age. by delicate lines of red, giving it a highly variegated County, N. J. near which strata belonging to this of which outcrop in the Philadelphia district, the appearance, while locally the percentage of iron division were once extensively worked for marl, has first four being separately represented on the WOODBURY CLAY. present is much greater and the sands have been furnished the name for the formation. In Mon accompanying maps. Areal distribution. The Woodbury clay out cemented into rather massive beds of sandstone. mouth County these beds are a part of the "Lami crops in a narrow belt lying just southeast of the Although for the most part the formation is com nated sands" which formed the upper portion of the MERCHANTVILLE CLAY. Merchantville line of outcrop. The upper part is posed of loose quartz sand, often closely resembling Clay-marl series of Cook, but in their extension Areal distribution. In the Philadelphia district exposed in the railroad cut 1 mile north of Had the sand of the present beaches, not infrequently it in the Philadelphia district and southwest they were the Merchantville clay occupies a narrow belt in donfield, where a few feet of the overlying English- contains thin lamina? of fine brittle clay, which correlated and mapped by him as Lower marl New Jersey roughly parallel to Delaware River town sand is also shown. The clay pits southwest stand in sharp contrast to the adjoining sands, with (Navesink). They were included in the Hazlet and diagonally crossing the Philadelphia and of Cuthbert afford a good section of the lower out any gradation between them. Toward the sands (upper Matawan) of Clark. Chester quadrangles. It has not been recognized portion of the formation. There are good exposures upper portion of the formation there is a horizon Stratigraphic relations. No unconformities have in Pennsylvania, unless some beds penetrated in along the banks of Woodbury Creek and its at which a, bed of clay a few feet in thickness been observed between the Marshalltown and the a well on Gordon Heights be referred to this branches west of Woodbury, and also on Raccoon occurs locally. It is apparently not continuous, underlying Woodbury, nor between the Marshall- formation. It is principally covered by later Creek west of Swedesboro. Southeast of Merchaut- although it has been seen at a number of widely town and the overlying Wenonah strata. Locally deposits over the divides, but outcrops along ville it is but slightly concealed by wash from later separated points. the Marshalltown formation is overlain unconform many of the tributaries of Delaware River. In deposits over a considerable area. Paleontologic character. So far as known the ably by later deposits of the Quaternary. the area under discussion the best exposures are Lithologic character. The Woodbury is com Englishtown sand contains no fossils. MONMOUTH GROUP. along the railroad east of Merchantville and in posed primarily of a thick bed of clay. It is Thickness. Its thickness ranges from 20 feet the clay pits near City Line station, Camden. somewhat micaceous, black, not sandy in the near Swedesboro to nearly 50 feet on Crosswicks The deposits in New Jersey which are here placed Exposures also occur in the banks or bed of lower portion but slightly so in the upper, Creek (a few miles northeast of the Philadelphia in the Monmouth group consist of the Mount Laurel most of the creeks from Pensauken Creek to where it is distinctly laminated. It does not con district) and to about 100 feet still farther north in sand, the Navesink marl, and the Redbank sand. Raccoon Creek. tain glauconite except, perhaps, at the very base Monmouth County. The first two only are represented in the Philadel Lithologic character. The Merchantville clay, and locally to a slight amount in the extreme Name and correlation. The formation receives phia district; and in Maryland no differentiation of the lowest member of the Matawan group, is black, upper portion. In this respect it is to be distin its name from Englishtown, Monmouth County, the Monmouth into parts is possible, the deposits glauconitic, and micaceous. It is usually greasy guished from the Merchantville clay. It weathers where it is well developed. It represents the lower being known as the Monmouth formation. The in appearance, and commonly massive in texture, to a light-chocolate color, and when dry breaks part of the Hazlet sands (upper Matawan) of Clark Wenonah sand, although included in .the group of particularly in the lower portion, while the upper into innumerable blocks, large and small, fre and forms a part of Cook's Clay-marl series. It is formations held to be correlatives of the Matawan of part is more sandy and is sometimes distinctly quently with a conchoidal fracture. In its lower the formation formerly called Columbus sand in Maryland, has not been mapped separately from the laminated. The upper and basal portions of this portion it is penetrated by numerous joints, which reports of the New Jersey State Survey, but that Mount Laurel in this district and is therefore dis bed are commonly much more glauconitic than in some localities, as in the clay pits at West name was abandoned because preoccupied by a cussed in connection with that formation. Similarly the middle part, and have, at times, been dug for Collingswood, are smoothed and polished. Many Devonian formation in Ohio. the absence of the Redbank sand in this district marl, although their use for this purpose has not of the joints are filled with crusts of limonite, Stratigraphic relations. The formation is con brings the Navesink marl into immediate contact been extensive. The glauconite is unevenly dis which sometimes form large honeycomb masses formable with the underlying Woodbury clay and with the overlying Hornerstown marl of the Ran- tributed, occurring commonly in patches rather many feet in diameter and tons in weight. In fact, the overlying Marshalltown formation. Through cocas group, from which lithologically it cannot be than as disseminated grains. It is entirely absent all gradations between films of limonite coating out considerable areas the Englishtown sand is readily distinguished. Paleontologically the two are at some horizons. Locally, small pebbles occur joints faces and these large masses can be found. covered by unconformable Quaternary strata. readily separable, but as fossils are in many places very sparingly in the basal portion. Lithologically the Woodbury is ^readily differen absent, separation of the Navesink and Horners The weathered portions of this formation are MARSHALLTOWN FORMATION. town is rather difficult. Consequently, for the tiated from the -n Merchantville byi/ its light-brownO very characteristic. Where marly they form an color where weathered, its usual lack of glauconite, Areal distribution. The outcrops of the Mar cartographic purposes of this folio, the Navesink indurated, cinnamon-brown earth, in which the and its numerous joints. The change to the over shalltown formation border those of the Englishtown of the Monmouth is combined with the Horners small black unweathered grains of marl are con lying Englishtown sand is comparatively abrupt, sand on the southeast and form a belt extending town of the Rancocas, just as the Wenonah of the spicuous. Where more sandy the weathered por the transition beds rarely exceeding 2 or 3 feet in diagonally across the southeastern portion of the Matawan group is combined with the Mount Laurel tion has a peculiar pepper and salt aspect. The thickness. district in a northeast-southwest direction from of the Monmouth group, and to avoid confusion weathered part of the nonmaiiy portion is less Paleontologic character. The Woodbury clay Haddonfield to Swedesboro. Small but good expo these same groupings are followed in the descrip characteristic and is sometimes a light chocolate- contains an abundant fauna, 95 species having been sures of the strata occur on Tindale Run southeast tions. colored clay, resembling the weathered part of the recognized. Lingula subspatulata, Yoldia longi- of Haddonfield, along Otter and Beaver brooks, WENONAH AND MOUNT LAUREL SANDS. next higher formation. frons, Lucina cretacea, and Cyprimeria cretacea are near Woodbury Heights, along Mantua Creek and Paleontologic character. The Merchantville the most characteristic forms. The fact that not its tributaries, and along the creeks between There has been some difference of opinion regard fauna is a large and varied one (102 species), and one of these forms has been seen in the Merchant Mickleton and Swedesboro. H- ing the classification and nomenclature of these is characterized by the abundance of Axinea subaus- ville clay and that the several abundant forms of the Lithologic character. The formation ranges from sands. The terms Mount Laurel and Wenonah tralis, Cucidlcea antrosa, Cardium tenuistriatum, Merchantville are exceedingly rare in the Woodbury a black sandy clay to an argillaceous marl. In the have both been used for them in part. There are Turritella merchantmllensis, and Panopea decisa, shows a faunal as well as a lithologic difference area under discussion the latter phase is the most somewhat definite lithologic differences between species which are conspicuous for their absence or between the t^vo formations. The Woodbury fauna common one, but farther northeast it is chiefly a them, although not always to the same degree, thus great' rarity in both the underlying Magothy and has more in common with that of the Magothy and black, laminated, micaceous clay with thin seams of rendering it difficult to separate them in many the Woodbury clay above, but which recur more or Wenonah than it has with the Merchantville below sand. Locally glauconite forms so large a con places. Paleontologically they are distinct, how less frequently in the Marshalltown and Navesink or the Marshalltown above. stituent of the mass that the bed has been ever, the lower portion containing a fauna with formations. Thickness. The thickness of the Woodbury clay exploited as a "marl bed," and, indeed, by earlier many species recurrent from the Woodbury, while Thickness. The greatest thickness of the Mer is about 50 feet. geologists was correlated with the "Lower marl" a much less number is common either to the chantville formation is about 60 feet. Name and correlation. The formation receives (Navesink) of Monmouth County. Marshalltown immediately below or to the Mount Name and correlation. The formation receives its name from the town of Woodbury, in Gloucester Paleontologic character. The Marshalltown clay Laurel and Navesink above. This fauna is further its name from the small town of Merchantville, in County, N. J. It was so designated because of the in its southern extent (within the limits of the Phila more closely allied to that of the Redbank. The Camden County, N. J., which is underlain by beds good sections formerly exposed in the railroad cut delphia district and farther southwest) is abundantly fauna of the upper portion (Mount Laurel), on the of this age. It represents the lower part of the at that place. It represents the upper part of the fossiliferous (43 species). Near Swedesboro, in contrary, is identical with that of the Navesink "Crosswicks cla,ys" (lower Matawan), described by "Crosswicks clays" (lower Matawan), described by particular, just beyond the southern limit of the marl, and is closely allied with that of the Marshall- Clark in the reports of the New Jersey Geological Clark in the reports of the New Jersey Geological district, the fossils occur in a remarkably perfect town on the one hand and of the Tinton (upper Survey, and forms the base .of the Clay-marl series Survey, and forms part of the Clay-marl series of state of preservation and in great numbers. Cucul- most sand member of the Redbank) on the other^ of Cook. Cook. Ic&a tippana, Neithea quinquecostata, and Carolium It therefore seems best to recognize both subdivisions 11 in the stratigraphic column, restricting the term name Rancocas w£s applied because of the typical Mount Laurel sand, the changed position of overlies the Vincentown, as is also the case in this Wenonah to the lower and Mount Laurel to the development of strata of this age in the valley of the base of the marl in reference to the shell bed, district a short distance down the dip. The Vin upper subdivision. For representation on the map Rancocas Creek, Burlington County, N. J. More and the beginning of the Belemnitella fauna, sug centown rests conformably upon the Hornerstown of the Philadelphia district, where the Wenonah recent studies by members of the Ne,w Jersey State gests very strongly that the upper part of what is formation. sand is thin and with difficulty separated from the Survey indicate that there are good paleontologic classed as Mount Laurel sand in the region near TERTIARY SYSTEM. overlying Mount Laurel, it seems best to combine reasons for uniting not only the Hornerstown and Philadelphia becomes a nearly pure glauconite in them as a single formation. Vincentown, but also the Manasquan in a single Monmouth County, thus reducing the Mount The Tertiary deposits of the Philadelphia district Areal distribution. These formations outcrop group, although their lithologic likeness to one Laurel sand in the section at Atlantic Highlands represent both the Miocene and the Pliocene; the along a comparatively high belt, 2 to 3 miles in another is no greater than to the subjacent forma to a thin bed scarcely more than 4 or 5 feet thick. Eocene deposits do not occur in this district, though width, from Tladdonfield to Swedesboro. At the tions of the Upper Cretaceous. As stated in a Name and correlation. Navesink River, in shown in different facies both to the north and to east end of the deep railroad cut 2 miles east of preceding paragraph, the Navesink marl in the Monmouth County, N. J., has furnished the name the south. Haddonfield, just beyond the eastern limit of the Philadelphia district is in immediate contact with for the Navesink marl, and the village of Horners The Miocene deposits of the Philadelphia district Philadelphia district, are shown 25 feet of coarse, the Hornerstown marl, the Redbank sand which town, in Burlington County, near which are comprise a part only of the extensive series of beds reddish, iron-cemented sand (Mount Laurel) under separates them in Monmouth County, N. J., being extensive marl pits, has supplied the name for the so characteristically developed along Chesapeake lain by a 6-foot exposure of fine, more or less mica absent in this region. Lithologically they can not Hornerstown marl. The Navesink has about the Bay and its tributaries and known by the name of ceous sand which is somewhat clayey (Wenonah). be readily separated, and so it seems best to map same limits as the Lower marl of Cook; the the Chesapeake group. In that region they are The Wenonah is also exposed, 15 feet thick in a them for the Philadelphia folio as a single unit. Hornerstown and Vincentown together constitute divided into three formations, which are, from deep road cut a mile south of Haddonfield. A The paleontologic studies indicate greater faunal Cook's Middle marl. below upward, the Calvert formation, the Choptank mile northeast of Runnemede there are exposures changes between the Navesink and Hornerstown Stratigraphic relations. The Navesink and formation, and the St. Marys formation. Within showing 25 feet of fine micaceous mottled sand with than between the Navesink and any earlier forma Hornerstown marls are conformably underlain in the Philadelphia district two divisions have been thin seams and small pellets of clay (Wenonah), tion. The greatest faunal break in the Upper the Philadelphia district by the Mount Laurel made of the Tertiary beds the Kirkwood and the grading upward into a coarse reddish-yellow sand Cretaceous of New Jersey occurs at the base of the sand, while overlying them, also conformably, is Cohansey, the former corresponding in part at (Mount Laurel). Along the ravines north and Hornerstown, the fauna of which is closely allied the Vincentown sand, or unconformably the Mio least, to the Calvert formation of Maryland and west of Wenonah there are exposures of an argil to that of the Vincentown and overlying Manasquan. cene sands and clays. The outcrops of the Nav- Virginia. The Cohansey is unconformable to the laceous, micaceous sand (Wenonah), probably 20 to sirik and Hornerstown are in many places concealed Kirkwood and may represent a horizon higher than 25 feet thick, above the Marshalltown, while in the NAVESINK AND HORNERSTOWN MARLS. from view by the unconformable deposits of the the St. Marys, since beds of similar lithologic char railroad cut and south and east of the town there Areal distribution. The Navesink and Horners Quaternary. acter are found farther east above strata carrying are thick exposures of the Mount Laurel. town marls outcrop in this district in a belt fossils recognized only in beds of St. Marys age VINCENTOWN SAND. Lithologic character. Northeast of the Philadel extending in a southwest direction from Ashland farther south. In Maryland the Choptank forma phia quadrangle, in Monmouth County, the deposits nearly to the southwest corner of the Philadelphia Areal distribution. The outcrops of the Vincen tion presents lithologic characters not unlike those at'this horizon consist mainly of a fine micaceous quadrangle. They are not found in the Chester town sand in this district are confined entirely to of the Cohansey and rests unconformably on the sand with some clay laminse, overlain by a coarse quadrangle. Many very excellent exposures occur the Philadelphia quadrangle and occur in a nar Calvert, but in the absence of fossils it is impossible quartz sand and containing considerable glauconite, along the streams in the vicinity of Sewell and at row belt extending from Laurel Springs southwest- to establish a satisfactory correlation between them. the grains of quartz being one-eighth to one-quarter Mullica Hill, a short distance south of the borders ward to the vicinity of Jefferson. There are The deposits of supposed Pliocene age (unless of an inch in diameter. Southwest of the Philadel of the district. good exposures showing induration of the materials the Cohansey sand is Pliocene) are confined to the phia and Chester quadrangles, in Salem County, the Lithologic character. The Navesink and at Laurel Springs, where the nodular limestone few worn remnants of the great mantle of coarse deposits consist essentially of the upper, coarse red Hornerstown strata are composed chiefly of glauco was formerly dug in a line of pits along Timber gravels and sands that closed the series of Tertiary dish quartz sand type, with glauconite throughout. nite, with 10 to 20 per cent of clay and a small Creek; along the creek below Grenloch; and on sediments along the Atlantic and Gulf borders and This deposit is strongly impregnated with iron, amount of quartz sand, which commonly increases Mantua Creek southwest of Hurffville. known as the Lafayette formation. They cover which forms crusts of all imaginable shapes and in amount toward the lower and upper portions of Lithologic character. The Vincentown sand, only a small area within the Philadelphia district locally has cemented the sand into firm beds of the marl bed. The basal portion of the Navesink where most typically developed, consists of a mass and - are confined to the Pennsylvania side of sandstone. In the Philadelphia district both types grades downward into the Mount Laurel, the of broken bryozoan, echinoid, coral, and other Delaware River. They reach their first important of sand have been recognized, although the coarser transition beds being sometimes referred to as calcareous remains, with some quartz sand and development in southern Maryland, from which phase has the greater development, and the litho- "sand marl," which in many places contains numer glauconite. The more calcareous layers frequently point southward they are a significant part of the logic differences are not so marked as farther to the ous fossils. This shell bed is well exposed at form beds of limestone intercalated with softer surficial deposits. northeast, owing to a gradual change in the lower Mullica Hill and at a number of points along the layers, which are sometimes a lime sand, but more KIRKWOOD FORMATION. member. tributaries of Edwards Run, 2 miles southwest of commonly a glauconitic quartz sand. The alter Paleontologic character. Though the Wenonah Mantua. nating hard and soft layers range from 4 inches to Areal distribution. The Kirkwood formation in fauna (80 species) contains an equal number of The top of the Hornerstown marl is also marked 2 feet in thickness, the indurated beds being, on an this district is confined to the southeast corner of Merchantville and Woodbury species, characteristic in many places by another shell bed locally 5 feet average, only about half as thick as the incoherent the Philadelphia quadrangle, lying southeast of the forms of the Merchantville are absent or very rare, thick and made up almost exclusively of shells of layers, so that at the best the larger part of the Navesink and Hornerstown marls. The extreme while its affiliations with the Woodbury fauna are two or three species. These two shell beds furnish formation is a glauconitic quartz sand. Traced width of outcrop is about 5 miles, not including close. The ponderous Gryphcea and Exogyra of the definite horizon lines which, where present, can northeast beyond the limits of the Philadelphia one or two small outliers that occur along its west Marshalltown fauna are absent in the Wenonah, be readily recognized and'mapped. quadrangle, the lime-sand phase becomes less ern margin. These outliers are exposed in the but Ostrea plumosa is in places a very common Paleontologic character. The Navesink marl marked, particularly in the upper portion, until 120-foot and 140-foot hills south of Woodbury, in species. The fauna of the Mount Laurel sand is (with the Mount Laurel sand) has yielded a large in Monmouth County the whole formation is the 140-foot hill (Irish Hill) west of Magnolia, and marked by the introduction of a new factor entirely fauna of 121 species of which Belemnitella ameri essentially a yellow quartz sand carrying varying in the hill just north of Mechanicsville. foreign to the earlier faunas of the region, the most cana and Terebratella plicata are the most charac amounts of glauconite with some broken shells, Lithologic character. The Kirkwood of the characteristic species of this new element being the teristic element, neither of them occurring in any which was described by Cook as the "yellow sand." Philadelphia district is principally a very fine, cephalopod Belemnitella americana and the brachio- other formation. A second conspicuous element is Paleontologic character. The calcareous phase flourlike sand, usually delicately banded in shades pod Terebratella plicata, both of which are also the Exogyra and Gryphcea group of forms, which of the Vincentown is almost entirely made up of of salmon-pink and yellow. The lower portion especially abundant and characteristic of the over recur from in the Marshalltown formation, E. the remains of bryozoans, while Foraminifera and often contains some glauconite, and scattered peb lying Navesink marl. The paleontologic data ponderosa being succeeded by E. costata. A third echinoids are very abundant, forming a fauna bles up to half an inch in thickness are found in indicate that the line between the Mount Laurel conspicuous element, distinct from the European quite different in these respects from that occurring this portion, although not abundantly. Locally, and Wenonah sands marked by the introduction of Belemnitella element and from the southern in the Hornerstown marl. But where the "yellow thin beds of coarse sand or even fine gravel occur the Belemnitella fauna is of greater significance than Exogyra element, is the^ Gucullc&a fauna recurrent sand" phase is developed Terebratula harlani, a immediately at the base. In very many places the the relatively slight difference in the character of from the Merchantville and Marshalltown, among Gryphcea, and other pelecypods belonging to the lower few feet are composed of black beds made up the sediments would imply. which are Axinea subaustralis and Cucullcva antrosa, same genera as the forms occurring in the shell bed of thin clay and sand laminse, as is well shown in Thickness. The combined thickness of the while there is an entire absence of the characteristic at the top of the Hornerstown are found in associ the marl pits at Sewell, where a bed of sandy clay Wenonah and Mount Laurel strata ranges from 40 members of the Lucina cretacea fkuna of the ation with forms characteristic of the calcareous 6 feet thick rests upon the Hornerstown toiarl. to 80 feet. Woodbury clay. phase of the formation, thus furnishing a sufficient Less commonly, the lower sands have been con Name and correlation. The town of Wenonah, The fauna of the Hornerstown marl is small reason for placing the Hornerstown and Vincen verted to nodular masses of quartzite by the infil in Gloucester County, N. J., and the hill known and, apart from.the shell bed at the top of the town in one paleontologic group, in which may tration of silica, and a silicified log was found in as Mount Laurel in Camden County, furnish the formation, has not yielded many fossils, but it is also be included the overlying Manasquan, although this formation at Lindenwold. The "bull's-head" names to these formations. As already stated, the totally different in essential characteristics from this formation does not occur in the Philadelphia bowlders of quartzite which occur commonly on the Wenonah constitutes the uppermost division of the faunas of all the underlying formations. district. surface from which the Kirkwood has been eroded the Matawan group and the Mount Laurel is the Terebratula harlani, Cucullcea vulgaris, and Gry- Thickness. The thickness of the Vincentown are believed to have been derived from this basal division of the Monmouth group. phcva sewellensis are characteristic forms. The shell along the line of its outcrop in^'fhe Philadelphia formation. /Stratigraphic relations. Beneath the Wenonah bed at the top of the marl contains a fauna so quadrangle is rarely more than 25 feet, but from Northeast of the Philadelphia quadrangle the lies the Marshalltown formation, with no strati- closely allied to that of the Vincentown sand that well borings it is known to attain a thickness of formation is predominantly a fine, fluffy sand, with graphic unconformity separating them, and the same it is a question whether it ought not to be regarded more than 100 feet a few miles to the southeast. black lignitic clays at or near the base and some condition holds true regarding the Mount Laurel as the base of that formation rather than as the top Name and correlation. The Vincentown sand similar clayey layers at other horizons. Southwest and the overlying Navesink marl. of the marl. received its name from Vincentown, N. J., near of this quadrangle the Kirkwood changes consider Thickness. The thickness of the Navesink and which the calcareous phase is typically developed. ably in character. Near the base occurs a fine, RAXCOCAS GROUP. Hornerstown marls, as shown by the record from It was included by Cook as a part of the " Middle loose, somewhat glauconitic sand, above which are The formations composing the Rancocas group numerous artesian wells, is from 40 to 45 feet. marl." several feet of very soft, micaceous sand and clay are two in number and were earlier described by Northeast of the Philadelphia district the Navesink Stratigraphic relations. In the Philadelphia dis that has a soapy, talclike feel and is snow-white Clark as the Sewell marls and the Vincentown marl extends several feet below the shell bed which trict the Vincentown along its outcrop is overlain where pure, but is not uncommonly stained with lime sands. He later applied the name Horners- in this region marks its base, and in Monmouth unconformably by Quaternary beds or by the Kirk- iron. Above this sand is a thick (80- to 90-foot) bed town to the "Sewell marls," the latter name having County, ;N. J., shows a thickness of 40 feet. This wood formation of the Miocene. Northeast of this of clay, chocolate to drab in color, and locally black. been elsewhere employed. They were first classed increased thickness to the northeast, which is district other Cretaceous and Eocene beds intervene It is in many places cut by joint planes into small as members of a single formation, to which the coincident with a decrease in the thickness of the and there the Manasquan formation conformably cubes, many of the joint faces being covered with Philadelphia. thin crusts of iron oxide. Borings show logs of either late Miocene or Pliocene. Obscure casts of /Stratigraphic relations. The Lafayette rests, for Another distinction between the formations is lignite, leaf beds, and considerable lenses of sand molluscan shells have been found in it near Mill- the most part, in the several outliers within the found in their relation to drainage lines. This occurring within the clay, although no sand layers ville. Philadelphia district, on crystalline rocks, though, applies particularly to the Pensauken and Cape are recognized in its area of outcrop. Locally it is Thickness. At its outcrop in the Philadelphia as has already been stated, a small outcrop of May formations. fossiliferous, but fossils are not common. quadrangle, the Cohansey has a thickness of 40 Raritari materials shows beneath the cover of the The separation of the formations as here defined Above this clay is a bed of brown clay and fine to 50 feet, but this is only a portion of its entire Lafayette at Media, Pa. is not on the basis of any one of these three clayey gray sand, containing great numbers of thickness, since it had been much eroded before the The Lafayette formation is found at considerably criteria, but on all three, and especially on their shells. It is known only from openings along the deposition of the Pleistocene Bridgeton formation, higher levels than the later Quaternary deposits, so relations to one another. headwaters of Stowe Creek and its tributaries and by which it is unconformably overlain. Its maxi that its relations to them in this district can not be Origin. The study of the Quaternary formations has been often described by earlier writers as the mum thickness is not definitely known, but it definitely determined. Farther south the oldest of of this and adjacent regions has led to the conclusion Shiloh marl. It forms the upper bed of the Kirk- unquestionably exceeds 200 feet, the Quaternary formations often rests unconform that streams played an important part in their wood in the region in which it occurs. Name and correlation. This formation takes its ably upon the Lafayette. deposition. The Pensauken and Cape May for Paleontologic character. Along its outcrop the name from Cohansey Creek, Cumberland County, Nothing definite can be determined regarding the mations, so far as they occur in this district, are Kirkwood formation is not markedly fossiliferous, N. J., along which it is well developed. It corre strike and dip of the beds from the small outliers interpreted as deposits made chiefly by surface except that part known as the Shiloh marl, from sponds to the sand member of the Beacon Hill in the Philadelphia district. The main body of drainage; but this statement is not to be interpreted which a large fauna, more than a hundred species, formation as formerly described in the New Jersey the formation farther south shows that the strata, to mean that there was no submergence of any part has been described (Whitfield, Mon. U. S. Geol. reports (Salisbury, 1901). Data regarding its age have the usual northeast-southwest strike, conform of the area where these formations occur during Survey, vol. 24). It contains the characteristic are indefinite and in a measure contradictory. ing to the continent margin, and that the dip of the the Quaternary period. The reasons for assigning fauna of the Calvert formation of Maryland and Paleobotanic evidence favors its reference to late beds is in general that of the other late Tertiary to rivers an important part in the origin of these Virginia. Miocene or Pliocene, while the scanty paleozoologic formations, being southeastward and about 10 feet formations will appear when the constitution of the Thickness. The thickness of the Kirkwood data are indecisive. At its outcrop it rests on the to the mile. formations has been considered. formation in the Philadelphia district is probably Kirkwood without apparent unconformity, but far The alternative conclusion to which some stu QTJATEKNARY SYSTEM. about 90 feet. To the southwest the thick clay bed ther southeast beds of similar lithologic character dents of these and equivalent formations in adjacent about Woodstown and Alloway is known to have a overlie strata bearing a St. Marys fauna, and it is EAST OF DELAWARE RIVER. regions have been led is that the formations are thickness of at least 80 feet, while locally the Shiloh therefore apparently unconformable to the Kirk By R. D. SALISBURY and G. N. KNAPP. primarily of marine origin. marl bed has been penetrated for 30 feet, and the RELATIONS AND ORIGIN OF THE FORMATIONS. wood. BRIDGETON FORMATION. talclike sand sometimes reaches 10 feet. Toward Stratigraphic relations. The Cohansey is over In that part of this district which lies east of Distribution. The Bridgeton formation, the the southeast these members increase greatly in lain unconformably by the Quaternary formations, Delaware River there are several Quaternary for oldest of the Quaternary formations of this region, thickness by the intercalation of beds at the top while its relation to the Kirkwood is indefinite, as mations, whose relations are somewhat complex. has but slight representation in this district. East and the base, so that at Atlantic City strata carry above indicated. Its dip is fairly regular to the Unlike the older formations beneath, they do not of the Delaware it appears only in the southeastern ing a Miocene fauna range from 390 to 1220 feet southeast, its base declining from 100 feet above sea lie in regular beds with fairly constant dip in a part of the Philadelphia quadrangle, and there in below mean tide and comprise beds representing level at Grenloch to about 390 feet below at Atlantic uniform direction. Each formation, as now seen, small areas only. Southeast of this quadrangle the the entire Miocene series found farther south. City a descent of 490 feet in 45 miles, or 11 feet consists of a series of patches of gravel, sand, loam, formation occurs in much larger areas, and the Name and correlation. The name Kirkwood to the mile. etc., at somewhat various levels, but yet standing patches which appear in the Philadelphia quad is taken from the small village of Kirkwood, Cam- The strike of the beds is northeast and southwest, in rather definite relations both to the relief and to rangle are to be looked on as outliers. (See figs. 1 den County. The formation is to be correlated, in conforming in a general way to that of the under the drainage of the region. Much difference of and 2.) They are larger and less widely separated part at least, with the Calvert formation of Mary lying Cretaceous formations, although northeast opinion has arisen concerning the interpretation to the southeast, and smaller and more widely land, the fauna of the Shiloh marl member being ward across New Jersey the higher members of the of these formations, a difference which still exists. separated to the northwest. The most northwest closely related to that of the Plum Point marl Cretaceous and finally the Eocene beds appear from Principal formations. There are three principal erly outliers are a few small areas arranged in a member, and the lower fine micaceous sand prob beneath the Kirkwood, showing that the strike of Quaternary formations in the area east of the Del ably corresponding closely to the Fairhaven diato- the Tertiary formations is a little more to the east aware, according to the interpretation here stated. BeUmawr Chews maceous earth member, although no diatoms have than that of the Cretaceous beds. These are, in order of age, the Bridgeton, the Pen- yet been found in it. sauken, and the Cape May. -Minor variations being LAFAYETTE FORMATION. FIG. 1. Section through hill east of Runneinede and hill east Stratigraphic relations. The Kirkwood forma disregarded, these formations may be said to lie at of Mechanicsville, N. J., showing the relations of the tion in the Philadelphia district overlies uncon- Areal distribution. The Lafayette formation is different levels along any line drawn at right angles Bridgeton and Pensauken formations. K, Cretaceous; M.Miocene; B, Bridgeton; p, Pensauken. formably the various Cretaceous strata (chiefly the entirely confined to the higher lands lying north to the Delaware. The Bridgeton formation occurs Vincentown and Hornerstown), but some of the and west of Philadelphia, where it occurs as irreg in small remnants only in the southeastern part of northeast-southwest line extending from a point a outliers rest on even lower formations, and in the ular outliers. The Lafayette formation has not the Philadelphia quadrangle. The altitude of its mile or so south of Clarksboro on the southwest adjoining districts the Manasquan (a higher forma been recognized at any point in the New Jersey base at the extreme southeast ranges from about 175 to a point near Haddonfield on the northeast. In tion) is locally exposed along stream banks in small portion of the district, and the outliers in Pennsyl feet to about 110 feet, but in most places the range is these areas remnants of the Bridgeton formation outcrops beneath the Kirkwood. vania represent apparently the most northerly from 125 to 140 feet. The Pensauken formation cap four somewhat conspicuous hills, which rise The relation of the Kirkwood to the Cohansey is deposits of this formation. They become gradually occurs in larger areas at lower levels, and its to altitudes of 133, 144, 146, and 140 feet. The not positively known. There is no definite evi more numerous southward, but do not constitute any altitude becomes lower to the south and west. The base of the Bridgeton formation in these four hills dence of a break in sedimentation, and within the important part of the Coastal Plain series of forma larger patches of this formation near Delaware area under discussion they seem to be conformable, tions until they extend as.a broad mantle down the River are believed to be remnants of a once con ClarkslDoro but in their wider extent there is good reason for backbone of the southern Maryland peninsula. tinuous formation deposited in the main valley, SEA LEVEL believing that the Cohansey overlaps the Kirkwood. The best exposure of Lafayette materials in this while the patches more remote from the Delaware FIG. 2. Section through Jefferson and Clarksboro, N. J., Well borings farther southeast indicate the presence district occurs near the reservoir in Media. are believed to consist chiefly of materials brought showing relations of Bridgeton and Pensauken formations. beneath the Cohansey of beds that are much Lithologic character. The deposits of the Lafay down at about the same time by tributary streams K, Cretaceous; M.Miocene; B, Bridgeton; p, Pensauken. younger than the Kirkwood at its outcrop. ette formation consist of gravels, gravelly loams, descending from the east and southeast. The has elevations ranging from about 125 to 135 feet. sands, and sandy loams, locally firmly indurated. extreme range of the base of the formation is from These heights give some indication of the position COHANSEY SAND. The coarser materials are much decayed, and the sea level, or even below, as at some points near of the surface along this line when the Bridgeton Areal distribution. The Cohansey sand appears whole deposit gives an indication of age which is Camden, to about 120 feet in the southeastern part formation was deposited. Two other remnants of only in the southeast corner of the Philadelphia lacking in the Quaternary formations. The north of the Philadelphia quadrangle: The Cape May doubtful Bridgeton gravel appear about 2 miles quadrangle, where it is for the most part thinly ern deposits are in the main less highly colored formation, which appears chiefly along the streams, south of Woodbury. covered by a discontinuous mantle of unclassified than those farther south, where they have a charac occurs at various altitudes from tide level, along The bases of the remnants of this formation lying Quaternary materials. It occurs at higher eleva teristic orange color. the Delaware and the lower ends of its tributaries, farther southeast, about Jefferson, Barnsboro, Fair- tions than any of the other Cretaceous or Tertiary Paleontologic character. No fossils have been up to the level of the Pensauken, or at the south view, Blackwood, and Turnersville, have elevations formations, near the headwaters of the northwest found in the Lafayette beds of the North Atlantic east corner of the Philadelphia quadrangle well up ranging from about 110 to 130 feet, while at the ward-flowing tributaries of Delaware River. Coastal Plain, the materials being wholly unadapted toward the base of the Bridgeton formation. extreme southeast corner of the quadrangle the Lithologic character. The Cohansey is primarily to their preservation. Criteria for separation. The differentiation of base of the formation is at a distinctly higher level, a sand formation, but it contains some gravel and Thickness. The thickness of the Lafayette for the formations is based on their topographic rela about 170 feet. locally considerable beds of clay, none of the latter, mation is variable in the Philadelphia district. tions, constitution, and relations to drainage lines. Phenomena of adjacent areas beyond these quad however, occurring within this area. The sand is The outliers have probably been much reduced by Looked at in a large way, the three formations rangles are of similar import, and make it appear predominantly coarser than that of the Kirkwood, erosion and no longer represent the full thickness are topographically distinct, and this distinction that at the time of the deposition of the Bridgeton and the grains are often coated with clay, so that of the deposits. The beds at no place apparently holds over a much larger area than that considered formation there was a broad tract of low land when moist it readily compacts. The fine mica exceed 20 feet in thickness. in this folio. This 0general statement does not>. lose adjacent to Delaware River, the surface of which ceous, mealy sand with its delicate pink and buff Name and correlation. The name Lafayette was sight of the fact that the range of level of the stood at a level which is now 110 to 135 feet above mottlings characteristic of the Kirkwood does not early used by Hilgard to designate deposits of this Cape May formation is from sea level up nearly to sea level, and that this lowland was bordered on occur in the Cohansey. The gravel of the Cohan age in the central Gulf region. The correlation the base of the Bridgeton in this district, and not the southeast by land some 50 feet higher. The sey consists of pebbles of quartz, chert, and quartz- and wider extension of the term were made by ably higher at a few points elsewhere; but for any strike of the slope between these two tracts had a ose sandstone, ranging in size from one-quarter McGee, and although some questions regarding the given region the topographic distinction of the northeast-southwest direction, passing through the inch to 11* inches in diameter and havingO angularO equivalency of the deposits 'still remain unsolved, several formations is reasonably sharp. Exceptions southeast corner of the Philadelphia quadrangle. to subangular forms. geologists have in recent years generally followed to this general rule are not wanting. The Bridgeton formation was deposited chiefly on Paleontologic character. No fossils have been McGee in the use of the name. The deposits here The three formations are characterized by certain the lowland to the northwest. Where the scarp to found in these beds in the Philadelphia quadrangle, referred to the Lafayette were earlier described differences in constitution, though they are not so the southeast was low the lowland appears to have but Hollick (New7 Jersey Geol. Survey, vol. 6, pp. under the name "Bryn Mawr gravels." From distinct that any one of them could be certainly been aggraded to its top; where it was higher the 138-139) reports fifty species of plant remains in their location, relations, and lithologic features there identified from a single exposure on the basis of Bridgeton formation appears to have failed to reach collections made near Bridgeton, in beds that may can be no question that they are part of the dis its constitution alone. In spite of all confusing its top, but to have been banked against it on the prove to be of the same age and that contain a flora sected mantle of the late Tertiary deposits that are gradations, there are certain broad distinctions northwest side. comparable with that of certain European upper so well developed farther south in Maryland and which persist, not only in this area, but throughout Constitution. The Bridgeton formation is made Miocene localities, and he regards the sands as Virginia. the State. up primarily of sand and gravel, the former pre- 13 dominating. The sand is largely, but not alto down to mean tide level locally, and near Camden are parts of a once continuous formation; those of The ironstone came from the Cretaceous and later gether, coarse and angular, and is generally more material that has the composition of the Pen the latter were, perhaps, never continuous. formations. The quartz and chert pebbles, which or less arkose. The material of the gravel has sauken has been thrown out of excavations 20 feet are generally prominent constituents, were probably DELAWARE RIVER PHASK. notable lithologic range. It includes quartz, sand below tide. It is inferred, therefore, that jthe Dela derived chiefly from the Bridgeton and older for stone of various sorts, quartzite, chert, trap, gran ware Valley was a little deeper than now when the Composition. The Pensauken formation is mations to the southeast. The giauconitic sand is ite, gneiss, schist, and shale. "While stones of deposition of the Pensauken formation began, and composed primarily of sand and gravel, but locally, evidently from the Cretaceous southeast of the these sorts of rocks rarely exceed a few inches in that tributary streams had valleys at harmonious as at Fish House, it includes beds or bodies of clay. Delaware. diameter, they sometimes attain the size of bowlders levels. The deeper parts of these valleys appear The gravel beds carry occasional bowlders which, in /Structure. The upper part of the formation does and some of them give evidence of but little wear. to have been narrow. Farther from the Delaware exceptional cases, are 4 and even 6 feet in diameter. not usually appear to be distinctly stratified. This The gravel is distributed more or less generally the base of the Pensauken is somewhat higher. At Fish House the clay constitutes a bed 20 to 25 is often the case to a depth of 8 to 10 feet. If the through the sand, often in thin seams, but some The configuration of the surface beneath the feet thick. In general, coarse and more or less formation attains greater thickness, and in places times irregularly. (See fig. 14 on illustration sheet.) Pensauken formation indicates that above the some angular sand predominates, while the gravel gener where it does not, stratification may be distinct in A thin layer (1 or 2 feet) of coarse gravel is espe what narrow and deep valley of the Delaware there ally appears either in thin beds or seams in the the lower part. Cross-bedding is conspicuous (fig. cially likely to occur at the very base of the forma was a broad plain along the Delaware after this sand or at its base. Locally, however, gravel pre 15 on illustration sheet). The materials are, on the tion. Those varieties of rock which are subject to interval of erosion, and that the level of this plain dominates, but even in such cases stones larger than whole, not well assorted, and the details of the sec decay are generally thoroughly softened. This is now ranges from about 50 feet above sea level near cobbles are rarely abundant. The sand and gravel tions vary notably not only from pit to pit but true, for example, of most of the crystalline rock, Swedesboro to 60 feet at Woodbury and to 70 feet are usually accompanied by a little loam, more or often in the faces of the same pit. of the shale, and of the sandstones which are not or a little more at Haddonfield. This valley plain less generally distributed through the coarser The formation is, on the whole, rather compact, composed almost wholly of quartz. More or less sloped gently toward the Delaware below Camden, materials, but more abundant in the upper part a characteristic which is often conspicuous in the pits earthy matter is mingled with the sand and gravel, while farther north it maintained its high level than in the lower. The materials are commonly that have been opened in it. The compactness is giving the whole a compactness not characteristic nearly to the stream, and then dropped off abruptly somewhat highly colored, generally with iron oxide. due to (1) incipient cementation of the material by of common sand and gravel. In most places, to the valley along the line where the large areas of Toward the top the color is in places orange-brown. iron oxide; (2) the presence of clay, loam, etc., indeed, compactness is one of its distinguishing Pensauken now approach that stream. This valley In some places the ferrugination has gone so far which fill the interstices between the grains; or (3) characteristics. As a result, the gravel often stands plain was affected by low swells on the one hand that the material is firmly cemented into conglom most commonly to both. The formation is ex with vertical faces year after year, in the pits where and by shallow valleys on the other. erate, but more commonly the iron oxide has only tensively worked for road material, its value depend it is dug for road material. This plain along the Delaware is believed to made the gravel and sand somewhat coherent. (See ing on the presence of the loam and clay, the iron Lithologically the material of the Bridgeton for have been terminated eastward by a slope or low figs. 16 and 17, illustration sheet.) oxide, and the decayed condition of many of the mation could not be distinguished with certainty scarp some 50 feet in height, which ran from The coarse materials consist of quartz, quartzite, coarser materials, which crush readily and pack from much of that of the Pensauken formation, Swedesboro on the southwest through Woodbury to sandstone of various sorts, chert, shale, gneiss, well in the road bed. though certain minor differences may often be Haddonfield. Its position was determined prima schist, granite, gabbro, basalt, and iron-cemented Thickness. The formation appears to have been detected. In many places it contains more loose rily by the outcrop of certain relatively resistant sandstone and conglomerate. Much more com thickest near the Delaware, but in many places its sand than that phase of the Pensauken which it beds of the Cretaceous (Wenonah and Mount Lau monly than otherwise these materials are well worn. present thickness depends on subsequent erosion, most resembles, probably because sand from the rel sands to the southwest, Englishtown sand to (See fig. 16.) The proportions of these several so that existing remnants are thin near the Delaware Kirkwood and Cohansey formations of the vicinity the northeast). At the time of the deposition of constituents vary greatly, but in the area under as well as far from it. Within this area the forma entered more largely into its make-up. the Pensauken formation this scarp was much inter consideration quartzose materials (quartz, quartzite, tion is at few places more than 30 feet thick and its Exposures. The Bridgeton formation is well rupted by the valleys tributary to the Delaware. quartzose sandstone, chert, etc.) predominate greatly. average thickness is probably less than half that exposed in Irish Hill 1 £ miles southeast of Bell- It has since been largely destroyed by erosion. Granites, gneisses, etc., rarely make so much as 10 amount. In the city of Philadelphia it has a mawr, in the hill at Woodbury Heights, a little to The higher surface southeast of the scarp had been per cent of the stones large enough to be readily known thickness of 50 feet. the northeast of Jefferson, half a mile north of somewhat maturely dissected by streams which led identified, and shale and arkose sandstone even less. Originally the upper surface of the Delaware Barnsboro, a mile southeast of Fairview, 2 miles to the Delaware along courses essentially the same Locally the waterworn pieces of ironstone are more River phase of the Pensauken probably extended west of Turnersville, and a mile north-northeast as those of the present streams, before the Pensau abundant than any of the other constituents, but from an elevation of about 120 feet in the vicinity of Blackwood. It is, indeed, exposed fairly well ken formation was deposited. in the Delaware River phase of the formation they of Haddington (West Philadelphia), to about the on most of the hills which it caps. Since the surface on which the Pensauken for are, as a rule, .distinctly subordinate. The sand same elevation at Haddonfield, N. J. (See fig. 3.) Difficulties of correlation. It is possible that mation was deposited is believed to have been Haddonfield PHILADELPHIA P some of the gravel classed as Bridgeton on the geo developed by subaerial erosion after the deposition l"*"85^ logic maps and lying at the lower levels has crept of the Bridgeton beds, the interval between these or slumped down somewhat from its original posi formations must have been somewhat long. While FiGK 8. Section through Philadelphia and Haddonfleld, showing the topographic position of the Pensauken formation. The tion. It is possible too that some of it has been erosion seems to have been the dominant process of remants are probably parts of a once continuous formation. shifted somewhat and redeposited, retaining essen this interval in this region, there was doubtless gr, granitic rocks; K, Cretaceous; P, Pensauken. tially its original composition. Material which has some deposition on the lower slopes and valley consists primarily of quartz, but it locally contains If so, approximately 80 feet of the formation had this history is really younger than the Bridge- plains. more or less decomposed feldspar (kaolin), glau- must have been removed from the vicinity of the ton proper, but its association with that formation conite, and grains of iron oxide. city hall in Philadelphia, where its original thick PENSAUKEN FORMATION. may yet be closer than that with the next younger This phase of the formation varies somewhat, ness must have been about 120 feet. This prob formation which is definitely recognized. It should Distribution. After the development of the both physically and lithologically, from the north ably represents about the maximum original thick be distinctly borne in mind that in a series such as topography just sketched the valleys of the Dela west to the southeast. The materials, which are ness of the formation. The area was narrow where that of which the Bridgeton formation is a member ware and its tributaries became the sites of deposi coarse near the Delaware, become finer with increas the thickness was so great. deposits of all ages, from the oldest to the young tion, and the deposits made constitute the Pensau ing distance from the river, and at the same time Local details. The type locality of the Pensauken forma est, are possible, or even probable. ken formation. Proceeding from the Delaware, the various sorts of crystalline rock, the shale, and tion is at the northern border of the Philadelphia quadrangle, The difficulties of correlation are greatest at the deposition spread laterally over the valley plain, some varieties of sandstone decrease in abundance at the mouth of Pensauken Creek. The best exposures are south of the creek, south of Palmyra and east of Morris. southeast, for here the base of the Bridgeton is aggrading it to a level which approached, but did and the sand becomes less arkose. On the other The thickness of the formation here ranges from 8 to 30 feet, nearly as low as the uppermost part of the Pensau not generally reach, the top of the Swedesboro- hand, fragments of ironstone are more abundant and its base is from 30 to (30 feet above sea level. The general character of the formation is shown by fig. 9. ken. Where the topographic distinction between Haddonfield scarp to the southeast. As its com and coarser toward the southeast. These variations The extensive sections exposed vary so much from point to the two formations fails their separation is based position shows, much of the material deposited on appear to mean that the materials which were con point that the range,of the formation for this region may be chiefly on their constitution. The younger forma the plain east of the Delaware was brought in from tributed by streams from the north are scarcer seen at this locality. At one point the section is as follows: tion (Pensauken) is made up in part of material the north, while some of it was brought in from the toward the southeast, while the materials contributed Section of Pensauken formation near mouth of derived from the older (Bridgeton), but in its shift southeast by the tributaries of'the Delaware. by the streams from the southeast increase in Pensauken Creek, New Jersey. abundance in that direction. The northwesterly Feet. ing and redeposition the softer constituents, such as Deposition in the main valley caused the tribu Brown sand and gravel______4 the decayed crystalline rock, the shale, etc., largely taries to aggrade their valleys. The formations on derived materials do not, as a rule, extend southeast Brownish-yellow sand, somewhat arkose______20 disappeared. Another of the marks of the reworked which they worked ranged from the Cretaceous to of the scarp referred to. The materials from the Gravel and cobbles______£ Cretaceous clay. material of the later formation is the presence in it the Bridgeton formations which were, 'on the southeast extend northwest of this scarp to a much of worn pieces of iron-cemented parts of the Bridge- whole, unlike those from which the Delaware and greater extent than the northerly materials extend A few rods distant the section is as follows: ton. It is true, however, that after all considera the Schuylkill derived their sediments. The result southeast of it. These general statements are per Feet. Coarse, compact gravel and brown sand______8 tions bearing on the question of correlation for a was that the deposits in the tributary valleys, made haps less true of the area southwest of Woodbury Coarse, brown, arkose sand.______16 given area have been weighed reasonable doubt may contemporaneously with the deposits in the main than of the area farther north. Coarse gravel and cobbles______$ Cretaceous clay and sand. remain. This is true, for example, in the case of valley, are of somewhat different constitution. Sources of the material. It is not generally pos some portions of areas mapped as unclassified sands Materials from the tributaries entered into the sible to identify the precise localities whence the As the Cretaceous beneath contains gravel at some points, it is locally difficult to determine the exact line of junction of and gravels. deposits along the main valley to some extent, but materials of the Pensauken came, but the northern the Pensauken and the Cretaceous. material brought down by the main stream did not origin of most of its coarse materials is certain. In the gravel of the above sections cobbles and pebbles of EROSION INTERVAL BETWEEN BRIDGETON AND PENSAUKEN. crystalline material, such as granite, gneiss, and schist, are enter into the deposits of the valleys of the tribu Thus certain types of the sandstone which it con abundant and are for the most part thoroughly decomposed. After the deposition of the Bridgeton formation taries. While, therefore, the Pensauken formation tains appear to correspond with the sandstone of Shale and basaltic rocks, probably of Triassic origin, are a period of erosion followed, during which much of is not uniform lithologically, its variations are some the Newark at various points up the Delaware, as perhaps equally abundant. Most of the coarse materials are distinctly waterworn, but angular pieces are not wanting. the formation within this district was removed. what definitely related to the several contributing at Stockton and Milford. Red shale from the Other exposures of the same sort occur at various points for The evidence of this erosion is found chiefly in the drainage basins. The distinction here made is Newark group is also a constituent of the Pen a mile southeast of the principal pits. East of Palmyra the formation in some places contains a configuration of the surface on which the next suc recognized on the map. In New Jersey, within sauken, though some of the red shale probably considerable amount of dark clay, associated with the sand ceeding formation, the Pensauken, was deposited. this district, the one phase of the formation is found comes from the Paleozoic formations of Pennsyl »nd gravel. The sections showing the clay are 30 to 40 feet This has a very considerable relief. Near the northwest and the other southeast of a line running vania. The occasional pieces of diabase are also above sea level and suggest that during the early stages of Pensauken deposition slack-water conditions obtained, at Delaware the altitude of the base of the Pensauken from Ellisburg, near the eastern margin, to Swedes doubtless from the Newark. Much of the gneiss least locally. formation generally ranges from about 40 feet at boro, at the southern margin. That phase of the and schist may be confidently referred to the gneiss The most exceptional section of the Pensauken occurs at Fish House, where it contains 20 to 25 feet of dark clay. the southwest to 80 to 90 feet at the northeast, formation which lies in the main valley, nearer the of the Philadelphia region, but it is not possible to The clay rests on Cretaceous clay at some points and on with a tendency to sink to lower levels toward the Delaware, is called the Delaware Hiver phase, while identify the precise localities whence they came. Pensauken gravel at others. The latter contact has not been the phase which lies to the southeast is called the The source of the granite and gabbro, both of which seen in section, but material thrown out from holes sunk Delaware and near tributary streams. Along the below the floor of the clay pit for drainage purposes has the Delaware, indeed, the formation probably runs tributary-valley phase. The patches of the former are extremely rare south of Camden, is not known. distinctive characteristics of Pensauken gravel. It contains Philadelphia. 14 numerous bits of shale, granite, etc., apparently identical in some of the gravel and sand mapped as Pensauken locality is somewhat cemented and is sometimes covered with they would probably have disappeared except from kind with materials seen in section at corresponding levels at may have been deposited prior to the deposition of dune sand. Several small areas of the same sort of material other points in the valley, especially in Philadelphia, where occur about Snow Hill, 2 miles south of Haddonfield. The the clayey parts, for the formation now contains a layer of clay 4 feet thick, like that at Fish House except in the Delaware River phase and some afterward. gravel here is thin, and consists almost wholly of quartz. practically nothing which is not nearly insoluble color, has been seen in the Pensauken formation. The The material was originally deposited chiefly in the Locally greenish or brownish clay is associated with the under normal conditions. A bit of limestone, for general relations of the clay at Fish House are shown in gravel. The material may have been derived from the Cre tributary valleys and on the gentle slopes above taceous of the vicinity. example, has never been found in the formation, them, and the scattered patches of the present time About Ashland, exposures show 6 feet of gravel, sand, and and the condition of the sand and gravel is such as are not believed ever to have been united into a loam, containing none of the materials which indicate a north westerly origin. Ironstone, quartz, quartzite, sandstone, and to lead almost inevitably to the conclusion that if continuous stratum. Since this phase of the for chert appear, but no granite or shale. Similar gravels occur limestone pebbles had ever been present they would mation was deposited the streams have shifted their about Greenland, Somerdale, and Kirkwood, at elevations have been leached out long ago. The absence of FIG. 4. Section showing the relationship of the clay (cl) to ranging from 95 to 115 feet. These gravels may have accumu the gravel of the Pensauken formation (p) at Fish House. courses down the dip of the underlying beds, and lated during the degradation which followed the deposition of marine fossils, therefore, can hardly be considered Dashed line above the section marks the former extension some of the old valley accumulations have thus the Bridgeton, and preceded the deposition of the main part conclusive evidence against the marine origin of of the Pensauken. been left well back from the present streams. Some of the Pensauken. In many places there is not more gravel the formation. in these localities than might have been left on the surface fig. 4. It has been seen to grade laterally into sand. At one of them, indeed, now constitute low divides. during its reduction from the Bridgeton to the Pensauken The structure of the formation has been referred stage the face of the pit here showed a bed of black clay 8 level. to. The extensive cross-bedding is consistent with feet thick, with no trace of sand, grading into sand with no Local details. Northeast of Swedesboro in the southeast The geologic map includes under the heading Pensauken clay, the transition being accomplished in a distance of 60 corner of the Chester quadrangle there is a series of patches formation certain areas of gravel and sand which are regarded a fluviatile origin, and perhaps not inconsistent feet. of gravel capping hills which range from 90 to 115 feet in ele as of somewhere near Pensauken age. These beds may include with deposition in standing water. The formation The clay at Fish House contains abundant fresh-water vation. These gravel caps are mere remnants. The slopes material which is older than the Pensauken but younger than fossils (Unio), one species being still represented in the below the hilltops and above the main body of the Pensauken the Bridgeton, and some which is younger than the Pensau has nowhere been seen to possess structural features Delaware of the immediate vicinity (Woolman). (Delaware River phase) to the west are nearly bare Cretaceous. ken but not so young as the Cape May. Inasmuch as deposits different from those which affect the deposits of In the.area about Haddontield the surface of the Pensau These caps of gravel are essentially without arkose sand, crys of slight extent at least appear to have been made at all stages glacio-fluvial waters. The ill assortment of the ken attains the maximum altitude for this region, 120 feet. talline rock, and shale. They are probably not strictly con since the deposition of the Bridgeton beds, a complete and The base of the Pensauken is here uneven, being higher to temporaneous with the Delaware River phase of the Pensau decisive classification into formations representing definite gravels, sands, and loams is a feature of stream the southeast. As the base rises the constitution of the for ken, but were probably deposited in the pre-Pensauken-post- periods of sedimentation is not possible. Some of the areas of deposits, rather than of ocean deposits. mation changes; it becomes less and less arkose, and carries Bridgeton interval of erosion. The sand and gravel are more doubtful Pensauken may possibly be the equivalent of some less and less shale and other material to which a northerly or less cemented by iron oxide (see fig. 17, illustration sheet). of the areas mapped as Bridgeton. Where there is no topo Another point which seems to favor the inter origin can be confidently assigned. The formation thins to West of some of these hills, which have steep slopes, the graphic basis for the separation of these two classes of areas pretation of the Pensauken formation as a land the southeast as its surface rises, and pinches out against the arkose sand of the Delaware River phase of the Pensauken their differentiation, as mapped, is based on the lithologic con rather than a marine deposit is found in the chem slope of the underlying Cretaceous, the top of which, about comes in about where the angle of slope changes. Similar stitution of the deposits. It should be clear from what has the 140-foot hill, has an elevation of about 100 feet. The remnants occur at various points northeastward to Wenonah, been said above that all gradations between these formations ical constitution of the material. It is usually as Pensauken material about the 140-foot hill (with cap of where there are larger areas of this phase of the Pensauken. may exist and that the separation of the deposits into Bridge- thoroughly decayed at the bottom as at the top. Bridgeton) is more or less generally cemented by iron oxide. A section along the railway south of Wenonah, in the south ton and Pensauken must in some cases be arbitrary. Good exposures occur in the pits a mile southwest of bank of Mantua Creek, is as follows: While this is by no means a conclusive line of evi Haddonfleld. ORIGIN OF THE PENSAUKEN. dence, it is a condition rather characteristic of river Near Audubon, at an elevation of about 70 feet, the Section south of Wenonah, in tank of Mantua Creek. section of the Pensauken is as follows: The Delaware River phase of the Pensauken is deposits, which are made slowly and under condi Feet. composed of debris which is believed to have been tions favoring decay, and it is less characteristic of Section of Pensauken for mation near Audubon. Reddish-brown clay loam______8 Gravel with sand and loam interstratified ______8 brought down by streams from the north during marine formations. Feet. Loam and sand______4 one of the early glacial epochs, an epoch which On the whole, therefore, if the formation can not Sandy loam with small pebbles ______2 Gravelly sand, with glauconite and green clay ______3 Brown arkose sand, very compact, with bands of Conglomerate with ferruginous cement.______1 antedated the last glacial epoch by a very long be said to possess characteristics which demonstrate pebbles ______4to6 Cretaceous sand. period of time. The streams, such as the Delaware, its fluviatile origin, it is yet true that such an origin Gravel and cobbles, many of granite and snale __ £ Yellowish arkose sand______<.______1 to 3 Waterworn bits and small slabs of ironstone are common in leading out from the ice sheet and laden with seems, all things considered, to accord best with the the gravel, also cobbles of quartzose material. The material debris which the ice had prepared, aggraded their facts, as now understood. Near Mount Ephraim, on the Haddonfield road, in the is strikingly like that now being deposited in the stream beds southwest bank of the creek, 10 feet of Pensauken sand and of the region. The general relations of this material are valleys, and the ice floating down the streams helped While the Pensauken appears to be chiefly a gravel are exposed, with the base about 20 feet above sea shown in fig. 5. This material is regarded as sediment them to transport the large pieces of rock, occasion ffuviatile formation, there is some reason to think level. The gravel is in thin sheets in the sand, and the sand ally of bowlder size, which occur in the formation that subsidence affected the region while the Pen is coarse, angular, and arkose. Many of the cobbles and pebbles are of decomposed granite and shale. Jefferson. of this region. The same agency floating ice sauken formation was being deposited. If so, some Half a mile north of Barrington, at an elevation of about 90 helps to account for the unworn character of some of the materials of this formation may be marine or feet, the irregularity of the base of the Pensauken is shown in the railway cut. Its relations are suggested by tig. 8. The of the coarse material of the formation, and at the estuarine. There is evidence in the clay beds of irregularity of its base is shown again in the vicinity of Bellr FIG. 5. Section through Jefferson, Barnsboro, and Wenonah. same time affords a rational explanation of the the formation that deposition took place locally in The Pensauken on the divide to the right of Chestnut mawr, where it ranges from 80 feet or so down to 20 feet. presence so far from its source of such soft materials standing rather than running water. Standing Exposures showing the contact of the Pensauken and Creta Branch was probably deposited by that stream, which has ceous have been well seen just west of the Beilmawr station, since shifted its bed toward the west. The Pensauken at as the friable Newark shale and sandstone. It is water, of course, does not necessarily imply sub where its altitude is about 50 feet, and half a mile to the north, Wenonah was probably deposited by Mantua Creek, which not believed that rivers, unaided by floating ice, mergence beneath the sea, and it is significant that on the east side of the Bellinawr-Mount Ephraim wagon has since shifted its position likewise toward the west. road, in the south bank of the creek, where its altitude is but K, Cretaceous; M.Miocene; B. Bridgeton; p, Pensauken. could have carried them so far, and it is still more the only fossils found in that part of the formation 20 feet. The Pensauken sand here is distinguished from the incredible that they could have been transported which surely implies standing water are all fresh accumulated in a valley at about the time that the Delaware Cretaceous sand beneath only by careful observation. The from their original position by waves. Furthermore, water shells and the bones of land animals. In former is somewhat arkosic, and has a few pebbles, whereas River phase of the formation was being deposited farther the latter has neither of these features. The contact of the west. The material was probably deposited by Chestnut a single well-glaciated stone has been found in the some other parts of New Jersey, however (near two formations, including part of each, is often cemented Branch, rather than by Mantua Creek. The dotted line of fig. 5 suggests the topography at the time of its deposition, Pensauken at Falsington, Pa., a few miles north of Tuckerton, for example), marine shells, which are (see fig. 6). The Pensauken is well exposed in pits about North Wood- since which Chestnut Branch has shifted toward the west to this district. Material much like the Pensauken perhaps ito be referred to this epoch, are found bury, where there is great variation in its constitution. its present position. Mantua Creek has probably shifted its occurs up the Delaware, as at Raven Rock, at much at elevations somewhat above the present level of position comparably, and remnants of the deposits which it About Clarksboro there is a large irregular area of Pensau higher levels (200 feet), seeming to point to the the sea; but since the age of these shells is not cer ken, composed chiefly of the usual arkose sand, with frag is thought to have made in the Pensauken epoch appeal- ments of shale and crystalline rock in the gravel. The nature north of t^alina. direction whence the material came. At least one tainly known, great weight should not be attached of the material here is well seen only in cuts, since the surface From 1£ to 2 miles southeast of Woodbury there are some distinctly glaciated bowlder has been found at to them in this connection. While, therefore, the is covered with younger loam. At the northwest its base has thin beds of gravel capping knolls which have an elevation of an elevation of 30 to 50 feet; to the southeast it rises to nearly about 100 feet. In general the gravel caps are very thin 2 Raven Rock. As already indicated, the material Delaware River phase of the Pensauken is regarded feet or less. A mile east of Woodbury Heights, where there is of the tributary valley phase of the formation had as primarily a river deposit, the hypothesis is enter 100 feet. fully 6 feet of gravel, is some material of northwestern origin. About Asbury and Rulons is a very considerable area of a different and more local source. tained that when the. material was deposited the Pensauken which locally attains a thickness of 80 feet. It is It is possible that these materials, exceptional for this region, made up chiefly of arkose sand, locally cemented by iron were derived from the Bridgeton to the east, though all the There may be some question as to whether the region where it was deposited may have been some oxide. At the northwest its base has an elevation of 20 to 50 soft materials, such as the shale, decayed granite, etc., gener material of the Delaware River phase of the Pen what depressed, thus facilitating the deposition by feet; at the southeast, 50 to 90 feet. At this level, which ally disappeared when the Bridgeton material was reworked. appears to represent nearly its original maximum elevation It is more likely that the area where these materials occur was sauken formation of this region, brought from the the streams. here, it terminates against the old Cretaceous scarp, remnants once connected with the Delaware River phase of the forma north by streams, was deposited by them directly, of which appear in the hills, rising to elevations of 114 to 122 tion, though now isolated by erosion. Bits of gneiss are also DISTINCTION OF PENSAUKEN FROM BRIDGETON. feet. The basal part (one-half to two-thirds) is of arkose sand, found in the Pensauken remnant 2 miles east of Woodbury. or whether the area of deposition was depressed while the upper part (one-third to one-half) contains gravel. This remnant was probably once connected with the larger sufficiently to be submerged beneath the sea or a It has been seen that the constitution of the Del The higher remnants of gravel to the east belong to the other areas to the west, and represents about the summit level of bay. It seems clear that the material of the forma aware River phase of the Pensauken formation is phase of the formation. the Delaware River phase of the formation. Between Chews Landing and Turnersville there are numer tion was essentially river borne, not wave derived. essentially the same as that of the Bridgeton, while TRIBUTARY-VALLEY PHASE. ous patches of surface material mapped as Pensauken, but This is shown by its constitution, for it was derived the composition of the tributary-valley phase of the their deposition may have taken place at any time after the The second phase of the Pensauken formation degradation of the Bridgeton surface was well advanced. from very different levels, some of them levels Pensauken differs in that its distinctive constituents differs notably from the first. Its areas are, on the They are made up of materials derived from the Bridgeton which no moderate submergence would have made came from the southeast. The Delaware River and lower formations to the east. phase of the Pensauken is much like the Bridgeton whole, smaller and less well defined. The material The correlation of the remnants of this region is more or less accessible to the waves. It is shown also by the is, in general, not arkose; and in few places is there uncertain, for between the Bridgeton and the Pensauken relation of the constitution of the formation to the lithologically, but distinct from it topographically. there seem to be all possible gradations, and it is sometimes rock terranes along its borders. If it were a marine The tributary-valley phase of the Pensauken is anything which can be referred definitely to a impracticable to distinguish between portions of the Bridge- northwestern source. Such sand and gravel as ton which were deposited at lower levels than usual at the deposit, or at any rate if its materials wereHin any unlike the Bridgeton lithologically, but is not might have come from the Cretaceous and from outset and portions which have been redeposited with little considerable part wave derived, they should change always distinct from it topographically. The traiispoi tatiori and wear, and so remain inuch like the original tributary-valley phase of the Pensauken is unlike the Kirkwood, Cohansey, and Bridgeton formations in constitution. An instance of such uncertainty appears in from point to point, as the shore formations change. to the east predominate; crystalline rock, shale, etc., the little hill just north of Turnersville, where the gravel is Their failure to change in this way is a strong cemented so as tb,be quarried for stone. The quarrying takes argument against the wave origin of the material, are essentially lacking; and, locally at least, iron place just above the 100-foot level. The material, which was stone is very abundant. As a whole, therefore, the originally cross-bedded sand with cobbles, is fairly character if not against its deposition in the sea. Again, no material packs less readily and is less useful for istic of the Bridgeton, including shale, sandstone, quartzite, distinctive mark of a marine formation has been etc. Over the cemented portion lies sand, which appears to road material than that of the Delaware phase. It have been a derivative from the Miocene. This is one of the recognized in the Pensauken formation. Its only nowhere occurs in such thick, beds as the Delaware cases where it is impossible to say whether the material is known fossils are fresh-water and land species. No Bridgeton in its original position or whether it should be sea cliff, nor any shore line, definitely identified as River phase of the formation, thicknesses of more classed with the Pensauken. than 10 to 15 feet being rare. On the whole, the Southeast of Barrington (2 miles southwest of Haddonfield) such, is found. Various lines of cliffs at one point the base on which the Pensauken rests is irregular and the base of this phase of the formation is slightly higher and another have been interpreted as sea cliffs, but b. gravel is without the distinctive constituents which point to a FIG. 7. (a) Ideal section showing deep covering of Quaternary than the base of the other phase, and it rises toward northwesterly origin. (See fig. 6.) The Pensauken of this it does not appear that they are not equally well interpreted as the bluffs of river valleys. So far as sediments over an irregular surface, (b) Same section after the heads of the valleys, locally approaching or erosion. The remnants of surficial deposits are so distrib perhaps even reaching the level of the Bridgeton. New Jersey is concerned, indeed, this seems the uted as to give the appearance of constituting two separate As already indicated, this phase of the formation better interpretation. formations, 1 and 2. is regarded as the sedimentary matter deposited FIG. 6. Section 2 miles southeast of Haddonfield, showing the On the other hand, it should be said that the the Bridgeton lithologically,' but is not everywhere irregular base of the Pensauken formation. The sand and physical condition of the formation is such that, distinct from it topographically. The general con- chiefly by tributary drainage during the deposition clay at the contact of the Pensauken and Cretaceous, are of the Delaware River phase of the Pensauken; but more or less cemented into ironstone. even if it once contained abundant marine shells, ception of its historical relations is indicated by fig. 7. 15
The outliers of Bridgeton well away from the had the effect''of "ponding its tributaries. Their the streamward edge of the terrace flat arid the from-stream sauken from the undifferentiated material below edge undulatory. At Ellisburg the corresponding terraces highlands at the southeast, as near Jefferson, Barns- currents, thus checked, dropped the coarser (parts have an elevation of about 30 feet. Farther up the valley the can not be drawn accurately, for in the absence of boro, and Bellmawr, are much more readily distin of their loads, though some of their fine sand and formation rises to an elevation of 60 feet or more within the exposures it is not always, and perhaps not gener guished from the Pensauken than the areas to the silt doubtless reached the Delaware Valley and Philadelphia quadrangle. It is, however, not everywhere ally, possible to determine the exact limit of the o disposed in the form of distinct terraces. southeast, as about Turnersville, where the Pen helped to silt it up. Under these conditions, Newton Creek. The formation is widespread in the basin Pensa-uken as originally deposited. This would be sauken is higher and rather less unlike the Bridge- material derived from the Paleozoic rocks to the of Newton Creek, but its thickness rarely exceeds 8 to 10 feet, simple if its base were everywhere at the same level, The top part is usually loam, below which there are 2 to 8 feet ton in constitution. In spite of the fact .that the north appear in the Cape May formation of the of sand and gravel. The gravel is fine, and thins out back or at the same level everywhere in a given region, two formations seem to grade into each other in main valley, especially to the north, while the equiv from the streams, where in many places loam is all that but it is not. some places, the balance of evidence seems to be in alent deposits in the tributary valleys are made up appears over the older formations. Shallow valleys appear to A lesser amount of the undifferentiated material have been filled up with the sand and gravel, and the loam favor of their separation by a long period of erosion. of such materials as the tributary streams could get then spread over all. The surface is undulatory, especially lies on slopes between the Bridgeton and the from the Cretaceous, Miocene, Bridgeton, and Pen marked by shallow basins at some points, as south and south Pensauken. Such areas are less extensive than the CAPB MAT FORMATION. east of Mount Bphraim station and on the north slope of Little sauken formations. Timber Creek. It is riot possible to say how far these undu others. In a few places the undifferentiated mate Distribution. The Cape May formation is the In the reworking of the arkose sands of the older lations of surface are due to the deposition of the Cape May rial lies on slopes between the Bridgeton above and youngest formation of the region, if wind-blown Quaternary formations the kaolin was separated formation and how far they are the result of movement of the the Cape May below, where the Pensauken forma underlying Cretaceous beds. sand, modern alluvium, and swamp accumulations from the coarser materials, and the decayed pieces Big Timber Creek. The Cape May formation is more tion, if once present, has been removed. When the of vegetable matter be left out of consideration. of crystalline rock, the soft shales and sandstones, extensively developed along Big Timber Creek than along material is in such situations its age can only be most others. It is well shown on the Delaware at "VVestville The largest areas of the formation in New Jersey, and the decayed cherts were destroyed. The more and for 1-J- miles up the creek. Here it is fully 20 feet thick, is said to be post-Bridgeton. within the limits of this district, occur along Dela resistant quartzose materials of these formations, composed of sand and gravel, arid its base is at least as low as Slope wash and lodgment, slumping, the creep of ware River, especially in the Chester quadrangle, however, entered into the new Cape May forma tide level. The formation is also well shown on the narrow material down the slopes, and the wind, all have belt between Big Timber and Beaver creeks, and again and about Camden in the Philadelphia quadrangle. tion. Fragments of iron-cemented sandstone and between Big Timber and Almonesson creeks, just above their contributed to the development of this class of The significant feature of its distribution is that it conglomerate from these formations, and the iron- junction. Up Almonesson Creek there are deposits of the undifferentiated material. It is not unlike the same age, but they do not constitute well-defined terraces. occurs chiefly along the streams. It is indeed pri cemented sandstone from the Cretaceous, Miocene, Along the main creek the formation extends to the edge of the other phases of the Quaternary deposits, except in marily a valley deposit, but at the lower levels some and Pliocene also entered into the sediments depos district. It is well exposed a mile northeast of Almonesson, its thinness and in the fact that its age can not of its material was probably deposited in standing ited in the valleys and were mingled with the finer where it is 15 to 20 feet thick 'and where it runs up the slope always be determined. to an elevation of about 50 feet. The material consists of water, though brought to its position by streams; sediments. clean, incoherent, well-stratified sand and fine gravel, very Where the undifferentiated material is but elsewhere it is strictly fluviatile. There are reasons for thinking that the surface like that at Westville. At Mechanicsville it attains an eleva slightly below the formations from which it is of the land may have stood somewhat lower than tion of 50 feet and is at least 20 feet thick. At Blackwood it derived it may closely resemble them in constitu Being essentially a stream deposit, the formation has risen to the Pensauken level and is not readily distin is not limited by contour lines, but its variations of now when the formation was deposited, or at some guished from that formation. tion. Where it has been transported farther its level are systematic, increasing in altitude up the stage during its deposition. One reason is found On the north branch of the creek, a little above the junc composition has been more altered, particularly by tion, there is 10 feet of the Cape May formation on the streams.- Along the Delaware the formation ranges in the nature of the deposits along the Delaware Cretaceous, the top being at an elevation of about 50 feet. the elimination of the readily destructible materials, up to 30 feet in altitude in this district, but toward itself. The sand and gravel which are characteristic Loam of uncertain age occurs on the slope above. A mile east such as kaolin, soft shale, decayed granite, etc., of this formation to the north essentially fail below of Chews Landing the formation has a thickness of 20 feet or which often exist in some of the older and higher the heads of the larger streams tributary to the so, but thins up the stream, where it rises to the Pensauken Delaware from the east it rises to the level of the Philadelphia. Again, marine diatoms have been level, 60 to 75 feet, arid the separation of the two becomes members of the Quaternary. tributary-valley phase of the Pensauken formation, abundantly identified in the loam of the Cape May confusing. During the deposition of the Cape May formation the WIND-BLOWN SAND, LOAM, AND ALLUVIUM. and in such situations it is sometimes difficult to formation in Philadelphia up to levels of 40 feet or valley of Big Timber Creek seems to have been filled up to a Eolian sand is widespread within the district, distinguish the two, topographically as well as lith- a little more. While it is of course recognized that level of 20 feet or a little more at,Westville and to 40 feet at but it is rarely in such quantity as to merit separate ologically. Locally, as east of Mantua, the Cape diatom tests might be blown about, it would appear trlendora, the South Branch to 60 feet at Blackwood and 70 feet at Turnersville, and the .North Branch to 6U feet or more mapping. A few areas of dune sand are shown. May formation rests on the Pensauken; in other that if this were their origin they should not be at Laurel Springs. A thin mantle of loam, of uncertain origin is places it lies against that formation (see fig. 8), so restricted to rather definite levels, as is said to be The surface loam is less conspicuous in the Big Timber the case. On the other hand, it is to be remembered Creek basin than in most other parts of the region. It is not, also widespread. A part of it may be eolian; and however, absent, for the ridge between Big Timber Creek and parts may have originated in other ways. Quanti that marine diatoms, often in secondary positions, Almonessen Creek is loam covered. This loam may be eolian have been found in the glacial drift of the Great so far as known. tatively it is of little importance, except that it is Woodbury Creek. There are terraces of Cape May material in many places just thick enough to cover up the -. 8. Section illustrating a common relation of the Cape Plains and about the head of Lake Michigan (Daw- on Woodbury Creek below Mathews Brook, at an elevation of May formation in the tributary valleys. son, Jour. Geology, vol. 5, p. 257), where the 20 feet, on the south side of the main stream. The formation material beneath, so that the various features of the K, Cretaceous; P, Pensauken; CM, Cape May. deposits in which they occur can hardly be sup here departs from its usual habit in that it contains some silt underlying formations are obscured at the surface. and clay along with the sand and gravel. The same phenom The data on which the mapping of the underlying that while the streamward edge of the terrace is posed to be of a marine origin. At other points in enon recurs at Swedesboro. formation is based include hundreds of borings a Cape May, the inner edge is Pensauken. As both the State, too, especially on the south coast, marine Near the junction of Mathews Brook the Cape May terraces approach a level of 30 feet, the formation having a thickness few feet in depth, penetrating the masking and formations are often covered with loam sufficiently shells of various sorts have been found in this of about 10 feet. Distinct benches occur just west of Wood- deceptive mantle of loam. These borings have deep to conceal the more characteristic materials formation a few feet above tide. bury at 10 to 20 feet, but they are probably degradational. Loam often covers the terraces, concealing the sand and gravel often led to a mapping which would hardly have beneath, absolute lines can not always be drawn below. Delaware River. In the Chester quadrangle the Cretaceous been justified on the basis of the natural surface. Mantua Creek. Along the lower course of Mantua Creek between them. In still other cases the Cape May near the Delaware is covered with but a thin mantle of loam there are 20 to 80 feet of sand and gravel, filling old valleys in Alluvium occurs in the marshes bordering the formation appears at low levels along the streams, and sand, which in places is gravelly near the streams. It is the Cretaceous plain. The surface is loamy or sandy, as about rarely more than 5 or 6 feet in depth, but locally thickens as Delaware and the flood plains near the mouths of while the Pensauken caps the divides; and over Thorofare, or clayey, as east of Paradise. At Berkeley gravel it becomes coarser. Here and there this surface mantle is so and sand make a terrace 20 to 25 feet high on the left bank of its tributaries. the slopes, above the upper edge of the Cape May, thin and discontinuous that the Cretaceous appears in patches the stream. The material is mainly well-stratified sand with at the surface, as at Billingsport and Gribbstown, at very low WEST OF DELAWARE RIVER. there is detritus washed down from the Pensauken a little fine gravel. Between Mantua Creek and Edwards levels. It is possible that the surface of this lowland has been Run, and just above their junction, there is perhaps 40 feet of BY F. BASCOM. above, which grades into the Cape May below. degraded since the Cape May formation was deposited, but it Cape May material; that is, the formation at this- point These relations make it difficult to separate the for is regarded as more probable that the amount of Cape May The Quaternary deposits on the west side of appears to go down to tide level. The surface is more or less material deposited here at the outset was slight. mations in some places. affected by wind-blown sand. Delaware River in this area form a narrow band The topography of the lowland along the Delaware in the Half a mile west of Mantua the terrace level is about 40 The Cape May formation occurs locally in the Chester quadrangle is not in strict accord with the drainage. from 1 to 5 miles in width, extending entirely across feet, 10 feet of sand and gravel overlying the Cretaceous. Though drainage features predominate, they are somewhat form of terraces along the streams, but many of the The formation is well exposed both north and south of the the Germantown, Philadelphia, and Chester quad masked by the surface loam, which, in its'deposition, seems to little creek tributary from the south, west of Mantua. On the terraces are ill defined. It is, on the whole, more have developed undulations of a feeble sort. The topography rangles. The inner border of the oldest deposits is right bank of the Mantua above Wenonali the Cape May for extensively developed on the right sides of the is such as might be developed if an old plain of but few feet marked by a distinct escarpment that passes near mation appears at an elevation of 60 feet, having a thickness relief were submerged and a few feet of loose material depos streams than on the left, probably because of the of 20 feet. It was formerly well exposed in the railroad cut Somerton, Fox Chase, Cheltenham, Wayne Junc ited on it. On the_other hand, there are ^occasional traces of between Mantua and Monongahela creeks. monoclinal shifting which the streams suffered wind-blown sand, and at least many of the' undulations may tion, Falls of the Schuylkill, Fairmount Park Raccoon Creek. Three miles from the Delaware 20-foot before the Cape May epoch, giving them gentler be explained in this way. (Philadelphia), Lansdowne, Swarthmore, Booth- The formation appears to a greater or less extent along terraces appear along the left bank of this stream, the material slopes on the right and steeper slopes on the left. every tributary to the Delaware within this region, and to a being sand and fine gravel, and its surface affected by eolian wyn, and Gordon Heights. More faintly defined Composition. The formation is for the most greater extent in the larger valleys than in the smaller ones. sand. About 4$ miles from the Delaware, on the right bank, escarpments mark the inner border of each of the the terrace level is about 80 feet, though the mantle of Cape part a mixture of sand and gravel; but locally About Camden the wide area of the Cape May formation two later divisions of the Quaternary deposits. A seems to be connected in origin with Cooper Creek, rather May material is thin. Half a mile west of Swedesboro the loam and even clay are among its constituents. than with the Delaware. terrace has an elevation of about 35 feet, with 20 feet of Cape few of the deposits over part of the region lying to These materials, especially the sand and gravel, Pensauken Creek. The Cape May formation appears up May sand so clean that it is dug for mason's sand. At some the southeast of these escarpments are so thin that both branches of Pensauken Creek, but more on the right points along the lower course of the Raccoon there is a little are as a rule distinctly stratified, and the char side than on the left, as is the case generally throughout the clay in the lower part of the Cape May formation. they have not been represented on the map. The acter of the stratification is not unlike that of region. The first well-defined terrace appears about Parry, UNCLASSIFIED DEPOSITS. Quaternary deposits have been cut through by the the Pensauken formation. Cross-bedding is com but the formation appears in more considerable thickness tributary streams of Delaware River that have their between the two principal branches of the stream, just above mon, and the sand and gravel are often not well their junction. The material is here loose sand and gravel, In the Philadelphia district considerable areas sources in the Piedmont crystalline rocks. Thus separated. The formation is distinguished from and its surface has an elevation of 20 to 25 feet. The Cape are covered by a thin and discontinuous mantle of in many places the crystalline rocks are exposed May terraces, or terraces covered with Cape May material, surface material, the age of which is, in many places, the Delaware River phase of the Pensauken in that appear at other points up the South Branch, as west of Maple along the valleys, while the Quaternary deposits it is not arkose and does not contain the pieces of Shade, and again near the east edge of the district, where they not determinable. In other places, as at the level cap the stream divides. The deposits are usually crystalline rock, shale, soft sandstone, or soft chert have an elevation of 80 to 40 feet. At this point, as at many of the Cape May formation, its age may not be open thin, except in the immediate vicinity of the Dela others, the streamward edge of the terrace is flat, while the characteristic of that formation, and in that it con inner edge is undulatory and slightly lower. to great doubt, but its amount is so meager that ware, where they have a very considerable thick tains many more fragments of iron-cemented sand Cooper Greek. The upper edge of the Cape May formation the underlying beds are but poorly masked and the ness, as is shown by 'well borings in the city of is ill-defined in many places along Cooper Creek. The forma surface material is chiefly derived from them. It Philadelphia. In physical and lithologic charac stone. It is less compact than the Pensauken, tion is often easily recognized near the streams, where it may contains notably less iron oxide, and less loam in have a depth of 10 to 20 feet, but back from the streams it thins has seemed best to put such areas together on the ters they are similar to the corresponding deposits the form of coatings over the grains and pebbles. out, usually with no well-defined topographic limit. Where as map. The material of this mantle is of various on the east side of Delaware River elsewhere much as 10 to 20 feet thick, it consists of well-stratified gravel The formation has but slight thickness, often less and sand, generally free from loam; but as it thins out it ages. In many places it lies on slopes or areas described in detail. than 5 feet and rarely so much as 15 feet. takes on loam akin to that of the slope above, so that there is intermediate between the Pensauken above and the Besides the Quaternary sediments within the often between the Cape May below and the Pensauken above Cape May below. In such situations it is probably Origin. The Cape May formation is of late an uncertain belt. Cooper Creek heads back in the Miocene Delaware Valley, there are isolated areas covered glacial age. This is shown by the fact that, traced area, and the peculiar sand of the Miocene influenced the made up largely of material which lodged on flats with rather thin deposits of Quaternary materials up the valley of the Delaware, it is continuous with character of the Cape May deposits below. or gentle slopes below the Pensauken in post- in Chester Valley. Few of these deposits are more Terraces appear on Cooper Creek 3 miles from the Dela the gravels of late glacial age that are well developed ware, at an elevation of about 20 feet. They are often affected Pensauken time. Some of it came to its present than 10 feet in thickness, and many of them con about Trenton and at various points between Tren by wind-blown sand, which sometimes occurs in low ridges, 2 position, probably, before the Cape May epoch, sist of mere films of surface waterworn gravels. to 4 feet high. The terraces rise upstream, slowly. Five miles some of it during that epoch, and some of it after ton and Philadelphia, especially on the west side of from the Delaware they are a little higher, and the material is The latter are not shown on the map, though they the river. The aggradation of the Delaware Valley more than 20 feet deep on the right bank of the stream, with ward. In many places the line separating the Pen are present in a number of places. One of the Philadelphia. 16 thickest deposits is situated in Chester Valley, more varied, ranging from open and nearly sym they have given rise, are possibly continuous over tion, though in different formations one process about 2 miles southeast of Valley Forge, and con metrical to inclined, overturned, or isoclinal folds. the crest of the anticline north of Chestnut Hill. may be dominant. The processes called into play sists of loose gravels and sands that have been dug The unsymmetrical folds are uniformly inclined to The Cream Valley fault splits into two faults and the results produced will be dependent on the for road-building purposes. Other deposits of the northwest. about 3 miles west of the Schuylkill. The more original constitution of the rocks. similar materials occur in the vicinity of Swede- Normal and thrust faults are both found in the northern branch is the plane of contact between Crystallization and metasomatism have been the land; in the vicinity of the old iron-ore mines Piedmont district. The Triassic sediments, which the Wissahickon gneiss and the Octoraro schist, dominant processes concerned in the production of about 11 miles north of Conshohocken, in the Nor- were uplifted with little or no folding or with a and continues for many miles to the west. The the Octoraro schist and the pre-Cambrian gneisses ristown quadrangle; and in the vicinity of Flour- very gentle northwest tilt, show scarcely any but southern fault causes the almost complete disap from shale and arkose. The Octoraro schist and town and Oreland, in the Germantown quadrangle. normal faults. These faults are so numerous that pearance of the limestone and quartzite of the the Wissahickon gneiss were both developed from These isolated patches of sands and gravels are so they may be seen in every extensive exposure of northwest limb of the anticline. argillaceous material the former from a more far removed from the Quaternary deposits border the Newark rocks. It is impossible to ascertain Limestone appears in Mechanicsville, west of the completely weathered product than the latter. ing the Delaware and differ so much in their their total number or amount of displacement, Schuylkill, on the crest of a subordinate anticline This fact may go far to explain the present differ position and lithologic characteristics that it is not which is often exceedina;lvo «/ slight.O Theyt/ were bounded on the southeast by the Cream Valley ences and resemblances between the two formations. possible to establish any definite correlation. Pro developed in connection with the crustal movement thrust fault, which first brings the Shenandoah The Octoraro schist was presumably developed visionally, however, they are correlated with the which resulted in the uplift of the Triassic sedi limestone and the Baltimore gneiss in contact and from a fine clay containing muscovite in minute older gravels of the Delaware River area. They ments, and presumably are not confined to the thence southwestward brings in contact the Wissa scales and possibly some undecomposed orthoclase. represent deposits of stream-borne materials laid present Triassic cover but occur also in the adjacent hickon gneiss and the Octoraro schist. Within the From the kaolin and the orthoclase muscovite and down when the streams that now cross the valley crystallines. It is very difficult to trace such faults Philadelphia district the quartzite of the northwest quartz may develop, with a loss of water, and a were flooded or when the region stood at a lower in the crystallines, where there is an absence of limb of the primary syncline appears at only two mica schist be produced. level than at present. These gravels now lie in the well-defined beds. Several small, nearly vertical points west of the Schuylkill. The first outcrop, In the case of the Wissahickon gneiss the interstream areas at a considerable elevation above faults can be seen in the railroad cut just east of one-quarter of a mile southeast of Gulf Ravine, on original deposit was more feldspathic and therefore the channels of the present streams. Overbrook station, and similar faults show in the the flank of Buck Ridge, is probably due to an presumably coarser grained. The resulting rock Schuylkill River section. infolding of the quartzite in the gneiss. In the is both more feldspathic and more coarsely crystal STRUCTURAL GEOLOGY. Thrust faulting is the rule in the Appalachian other exposure, between St. Davids and Strafford line than the mica schist. PIEDMONT PLATEAU AREA. structure, and many important faults of the Pied stations, the quartzite is brought to the level of the In the production of the pre-Cambrian gneisses By F. BASOOM. mont Plateau are of that nature. Those that have Wissahickon gneiss by the Cream Valley thrust injection and impregnation have also been active. been traced in the southern Piedmont area lie fault. The Baltimore gneiss is in some places thoroughly GENERAL STATEMENT. nearly parallel to the planes of schistosity of the The anticlinal character of the fold in the Balti injected with pegmatitic bands, and much of the The prevailing structural features of the Pied formations i. e., they dip at a high angle. Adjust more gneiss is shown in the Schuylkill River sec Wissahickon mica gneiss owes its pronounced mont Plateau are major folding of the Appalachian ment, by means of innumerable microscopic dislo tion. The secondary folding is close on either limb gneissic character to injection and impregnation. type, forming anticlinoria and synclinoria, which cations, has also taken place along planes of of the anticline and open in the center. The dips The fact that the new minerals which have extend for long distances northeast and southwest schistosity, which have thus become planes of vary from vertical to a steep southeast dip on the crystallized out from the impurities of the sedi and are roughly parallel; gentle minor folding at fissility. northwest limb, and are predominantly northwest ments are all minerals which, by a parallel orien right angles to the major folds; normal and thrust on the southeast limb, thus showing a divergence of tation of their longer axes normal to the direction LOCAL STKUCTUBES. faulting of varying magnitude; a very complete foliation. There is a very gentle northeast pitch, of compression, enable the rock to occupy less metamorphism of the formations, extensively pro Structure sections. The structure of the forma indicating a subordinate minor fold. The only other horizontal space than before crystallization, shows ducing schists and gneisses which show cleavage tions of the Philadelphia district is shown in the locality where the structure of the Baltimore gneiss that their development, like the folding, was in and fissility. A small portion of the Plateau is sections on the structure-section sheets and in fig. 9. can be seen is in a cut of the Cresheim branch of response to pressure and was a means of relieving covered with Triassic sediments and outliers of the On the structure-section sheet the vertical and hori the Pennsylvania Railroad near Laverock. Here strain. The intensity of the pressure is further Coastal Plain deposits, whose freedom from meta zontal scales of the sections are the same and the the gneiss is vertical to 60° SE. Elsewhere the indicated by the fact that muscovite and biotite are morphism and structural simplicity are in striking actual dips of the strata, as they appear at the sur gneiss when exposed is either so decayed or so developed in excess of hornblende and chlorite. contrast to the complexity of the crystalline floor face, are incorporated in the sections. Of course, thoroughly penetrated by the gabbro as to obscure Locally, in the pre-Cambrian gneisses, the upon which they lie. on the scale of the sections the smaller structures structural planes and the record of the folding to action of the processes of crystallization and The structures of the crystalline formations are can not be shown, and all folds of tertiary order which it has been subjected. metasomatism has been intensified by the intrusion due to compressive force acting in a northwest- are omitted. Faults are represented on the map The Huntington Valley fault, on the southeast of large bodies of igneous material.' In this case southeast direction, normal to the strike of the by heavy solid or broken lines, and in the sections flank of the Buck Ridge anticline, dips to the pressure has been relatively a less active agent, and major folds. A minor force acted at right angles by a solid line whose inclination shows the probable southeast, and by means of it the Wissahickon the crystallization has therefore been of a more to this major force and to it is due the gentle trans dip of the fault. The relative direction of the gneiss was thrust upon the pre-Cambrian and granular character. Under these conditions gar verse folding. While much remains to be accom movement of the strata on either side of the fault Paleozoic materials. The mica gneiss, susceptible net, tourmaline, staurolite, andalusite, hornblende, plished in the mapping of these major anticlines plane is indicated by arrows. to crumpling, shows much secondary folding. and chlorite have developed, and have reached a and synclines in their extension throughout the Folds and faults. The formations in this part This fact, together with the absence of recognizable size which render them conspicuous to the naked Piedmont Plateau, some well-defined folds have of the Piedmont Plateau illustrate very perfectly beds, obscures the primary folding, and while eye. The development of garnet, tourmaline, been recognized. the structures which have just been mentioned. there are evidences of two synclines and one staurolite, and andalusite is not confined, however, Such an anticline extends from the neighborhood The northwestern portion of the crystallines is anticline southeast of the Huntington Valley fault to contact zones. They occur very generally in of Cabin John, Md., where it has been traced by concealed beneath the Triassic cover, which has the line, they can not be distinctly traced in the the mica gneiss and show that the formation has Keith, northeastward through Maryland, where it gentle northwest dip and normal faulting common Philadelphia district. The presence of intrusives been in that deep-seated zone of metamorphism has been mapped by Mathews, and into Pennsyl to all the Triassic rocks of the Piedmont Plateau. and the cover of Quaternary materials further where minerals of high specific gravity are devel vania, where it shows itself in the Buck Ridge The crystalline foundation emerges from beneath obscure the structure of the mica gneiss. Along oped. anticline. To the east of this anticline two syn- the Triassic to form the Chester Valley syncline. the Wissahickon, where the gneiss is well exposed, In the Chickies quartzite induration and crystal clines and an anticline have been partly traced The limbs of the syncline, separating it from the the dips are often very gentle and predominantly lization have been the processes at work and have in Maryland and the District of Columbia. They adjacent anticlines, are formed by the Chickies northwest. The cleavage dip remains constant to converted the relatively pure beach sand into a are not well denned in the Philadelphia district. quartzite. This formation, resisting erosion more the southeast. quartzite made up of interlocking crystals of quartz. West of the Cabin John-Buck Ridge anticline is a successfully than the limestone, gives rise to the Where the sand was originally impure i. e., METAMORPHISM. synclinal basin which is clearly marked in Penn hills which border Chester Valley on the north, feldspathic or argillaceous metasomatism has also sylvania and Maryland. In Pennsylvania it is the and in the eastern half of the valley forms also the Every process of metamorphism has been con taken place and brought about the development of Chester Valley syncline. It passes through Mary southern hills. These hills are thus monoclinal in cerned in the transformation of the simple sediments muscovite and sericite. Such crystallization taking land in the neighborhood of Cardiff and is recog structure. To the southwest the southeastern limb of the Philadelphia district to crystalline schists place under pressure results in an arrangement of nized by Keith in the Washington area just west is progressively faulted out (Cream Valley fault) and gneisses; a more limited number of processes the cleavage planes of the mica normal to the com of Great Falls. Such is the succession of anticline near Conshohocken and along the South Valley is concerned in the metamorphism of the igneous pressive force; in this way is produced a rock and syncline of the first order from east to west in Hills. This shearing action is combined with a material. Chief of such processes are: (1) Indu cleavage parallel to the mineral cleavage, and the the Piedmont area east of the Triassic cover. The cross or minor fold which produces a general south ration, a mass movement of mineral particles in rock becomes quartz schist. Sometimes infiltration Cambro-Ordovician sediments of the whole width west pitch of the syncline. It is this southwest response to pressure, by means of which the material has caused an enlargement of both quartz of the Piedmont Plateau, ignoring the Triassic for pitch of the syncline that brings the older beds to mineral constituents of a rock are brought closer and feldspar, if the latter mineral is present, and mations which conceal a broad central area, appar the surface in succession at the northeast end of together and hardened; (2) crystallization, a mole has produced a rock which is much like gneiss. ently form an anticlinorium, which has brought to Chester Valley, and causes the expansion north cular movement in response to pressure, by means In the Shenandoah limestone, crystallization has the surface pre-Cainbrian gneiss along a central eastward of the oldest formation, the Baltimore of which, in association with induration, an inter been the process chiefly active in converting cal axis flanked by Cambrian quartzite, Cambro- gneiss, and the expansion south westward of the locking crystalline texture may be formed; (3) careous sediments into crystalline limestone or Ordovician limestone, and Ordovician mica schist. youngest formation, the Octoraro schist. impregnation, the penetration of a rock along marble. Amorphous calcium carbonate has crys The surface outcrop of these formations is inter The character of the secondary synclines and planes of parting (which may be either bedding, tallized and sometimes partly interchanged with rupted parallel to the strike and controlled in width anticlines which compose the main fold is inferred joint, or fissility planes) by vein material i. e., magnesium carbonate, and the amorphous impur by the minor folding, which, alternately bending from that of the tertiary folding on their limbs. by material precipitated from solutions; (4) injec ities have crystallized into silicates such as phlogo- the axis of the anticlinorium in a low trough or These tertiary folds (see fig. 13) in the Shenandoah tion, the penetration of a rock along planes of pite (chiefly), tremolite, and diopside, and thus a raising it in a low arch, brings to the surface suc limestone are isoclinal in character, the dips vary parting by molten material in relatively thin dolomitic marble, or in some places a dolomite, has cessively younger or successively older formations. ing from 45° to 80° SE. layers; (5) metasomatism, a processs whereby the been developed, and all evidence of the organisms There is, then, an anticlinorium compounded of anti The Chester Valley syncline is paralleled on the original mineral constituents of a rock are altered which may have assisted in the original formation clines and synclines of the first order, which are in southeast by the Buck Ridge anticline, which to, or replaced by, other minerals; (6) granulation, of the rock is lost. Not only have new minerals turn composed of secondary and tertiary anticlines brings to the surface the Baltimore gneiss. In the or the crushing of mineral particles under com been developed in the sediments, but new struc and synclines. east the adjacent syncline is faulted on the south pression, which, together with differential move tures have been produced, namely, schistosity and The secondary folds in the limestone and quartzite east flank of this anticline, and to the west the com ments along parallel planes and recrystallization, gneissic banding. These structures were the result of the eastern portion of the Plateau are isoclinal plementary syncline is faulted. These two faults, results in the deformation of the rock. of deformation due to compression and were brought in character and are uniformly overturned to the called respectively the Huntington Valley and the Two or more of these processes have usually about by the flattening through granulation and northwest, while in the gneisses and schists they are Cream Valley faults, from the valleys to which combined in the metamorphism of a single forma recrystallization, and the rotation of the original 17 minerals of the sediments, such as quartz or feld northeastward from Fort Washington into Bucks feet to the mile in the later Tertiary deposits. The history opens along the Atlantic border the present spar, and by the parallel orientation, described County, which widens the outcrop area of the direction of the dip, although in general easterly, is continent had not come into existence and only above, of the new minerals, which combined to Stockton .formation. somewhat more northerly in the Lower Cretaceous isolated and limited portions of the continental produce a parallel arrangement of the constituents. Faults. There are evidences of faults at many formations than in the Upper Cretaceous and plateau were above the sea. Here was situated a This parallel arrangement gives rise to rock cleavage localities, but the only exposures in which their Eocene formations, which become progressively comparatively limited land mass, which has been or to actual fracture, called fissility. relations are exhibited are in the long, deep rail more southerly. In the Miocene beds, however, called " Appalachia." Appalachia extended east This ease of fracture along approximately parallel road cuts between North Wales and Hoyt station. the direction of dip swings gradually back toward of the present shore line, but probably not beyond but usually wavy planes, combined with actual frac Here the Lockatong strata are broken by a succes the north and reaches its climax in this direction the present continental plateau. West of it was ture or fissility, produces a structure which is known sion of faults trending with the strike of the rocks again in the upper Miocene. From the gradual the Appalachian sea, in which sediments were as schistosity. The deformation which results in and dipping approximately at right angles to the disappearance northward of the marine Pliocene accumulating. The western border of Appalachia schistosity is microscopic as well as macroscopic. dip of the beds. At least ten of these faults are beds of the Carolinas the dip evidently changes was brought under water during the early history A strained molecular condition which shows itself visible within a distance of a mile. One, a short again to the south before the close of the Tertiary. of this region by a submergence taking place in in undulatory extinction, granulation confined to distance north of the tunnel, appears to have a The mantle of Quaternary formations slopes time known as pre-Paleozoic. Pre-Paleozoic sub the periphery of the mineral, complete granulation, throw of only 6 feet, with the drop on the south gradually either seaward or locally toward the mergence is recorded by a shallow-water deposit of and granulation with rotation of the grain were side. Some of the others may be of much greater channels of the various estuaries. These forma granitic sand and, with denudation of the land and stages in the process. Granulation is not a marked throw than this, for they have considerable tions occur as a veneer over the older deposits. deepening of the sea, by a fine argillaceous deposit. feature of the Piedmont sedimentary formations. breccia along the plane of movement. These In the Philadelphia district, as elsewhere in the These sediments accumulated upon an uneven floor The presence of water, included with them as sedi faults, however, are very small in comparison Coastal Plain, the Lower Cretaceous formations dip of granitic rocks and in an encroaching sea which ments, was favorable to crystallization rather than with the great displacements in adjoining regions eastward at a higher angle than any of the other permitted the argillaceous material to collect to the to granulation, and less energy was consumed in in New Jersey, some of which amount to several Coastal Plain formations about 40 to 50 feet to east of the earlier arkosic deposits, this process than in granulation and rotation. The thousand feet. It is believed that the deformation the mile while the unconformably overlying In this way the arkosic sand was both overlain intensity of the pressure also favored crystallization of the Newark beds is probably due to vertical Upper Cretaceous formations have a slightly lower by argillaceous mud and altogether supplanted by rather than granulation. movements in the floor of crystalline rocks upon dip about 35 feet to the mile but in a more this material on the east. Where feldspar was a more or less abundant which they lie. W. M. Davis has suggested that southerly direction. The Miocene formations, In the north mechanical sedimentation was constituent, giving a granular character to the rock, these movements were the result of tangential which unconformably overlie the Upper Cretaceous succeeded by organic and chemical deposits of cal and where alternating layers of the rock varied compression in the inclined granites and schists, deposits in this area (see fig. 9), the Eocene forma careous material. These sediments grew to a thick somewhat in mineral constitution, owing either to which caused unequal tilting and faulting of the tions being absent, dip at a still less angle about ness undetermined and in a period not definitely an original difference in the beds or to the injec overlying sedimentary rocks. 15 feet to the mile but in a more northerly direc known, but presumably long enough before Cam tion or impregnation of newr material, gneissic tion, the dip becoming progressively more marked brian time to permit not only their accumulation COASTAL PLAIN AREA. banding rather than schistosity was produced by in the higher beds, as shown by the general overlap but also their consolidation, partial metamor the reorientation of the constituents. By W. B. CLARK. of the lower Miocene beds by the higher toward phism, and uplift to a land surface. This uplift The minerals which have developed near the The Coastal Plain has not the simple structure the north. The overlying mantle of Quaternary was accompanied by the intrusion of great igneous contacts of the igneous bodies do not, howewer, which was earlier assigned to it. From the begin formations has in general the same characteristics masses which consolidated into granite, gabbro, take part in this parallel orientation. Their longer ning of Cretaceous time onward the angle and as in adjacent areas, and has already been described pyroxenite, and peridotite. axes or their prominent cleavages may be transverse direction of tilting constantly changed, and for the whole Coastal Plain district. During Cambrian time the sea again encroached to the schistosity of the containing rock. This although the angle of dip is to-day slight and its Numerous unconformities appear in the series of on the land and gradually deepened. At first a fact, the relatively large dimensions of the crystals, direction is prevailingly eastward or southeastward Coastal Plain formations. Omitting from consid pebbly beach deposit was formed, the material of and their granular form give them a porphyritic it differs in nearly all the formations. As a result eration the formations not represented in this dis which was derived from pre - Cambrian granite, character and show that their formation must have of uplifts and depressions the landward margins of trict, the first occurs between the Patapsco and the gneiss, and mica gneiss of Appalachia. The gravel been subsequent to the period of greatest pressure. the formations particularly show much complexity, Raritan. No satisfactory contact between these was succeeded by a clean beach sand deposit. With The results of the processes of metamorphism in with a marked change in the sequence of deposits formations has been observed in the Philadelphia deepening sea, clay was mixed with the sand, fol the igneous rocks of the Piedmont area are not less from point to point. At times transgression has j district, but their relationship is probably the lowed by calcareous mud and, with a clearing of characteristic than are the results of these processes buried the landward outcrop over wide areas, i same here as elsewhere. A marked unconformity, the sea, by calcareous sediments. This continued
ISO' BELOW SEA LEVEL FIG. 9. Section along line A-A on Philadelphia geologic map, showing sequence, relation, and structure of Cretaceous and Tertiary strata. (Vertical scale five times the horizontal.) Kr, Raritan formation; km, Magothy formation; Kmv, Merchantville clay; Kwb, Woodbury clay; Ke, Englishtown sand; Kmt, Marshalltown formation; Kw-Kml, Wenonah and Mount Laurel sands; Kns-Kh, Navesink and Hornerstown marls; Kv, Vincentown sand; Kmq, Manasquan formation; Tk, Kirkwood formation; To, Cohansey sand; Q, Quaternary deposits. in the sediments. Unlike the sediments, the igne although the formation may be found in sections however, appears between the Raritan and the into Ordovician time, when the sea shallowed ous rocks, already possessing an interlocking crys farther east. These differential movements have Magothy formations, and the same probably occurs again, the land rose, and a clay deposit followed talline texture and little if any included water, in portions of the Coastal Plain even brought between the Magothy formation and the Matawan over a wide area. responded to pressure by such strain effects as about the total disappearance above sea level of group. The later Upper Cretaceous formations are In this district there is no record of further sedi undulatory extinction, granulation, and a partial en tire'groups of formations, although they may at evidently conformable to the Matawan, but a pro mentation during Paleozoic time. It is not proba mineral alteration. Instead, therefore, of the fresh times be found far from the region of surface out nounced unconformity occurs between them and ble, however, that the subsequent movements of crystallization of the metamorphosed sediments, crops in deep-well borings. the overlying Miocene Kirkwood formation. (See uplift immediately followed the deposition of sandy the igneous rocks exhibit strained or granulated The\ older formations of the Potomac group fig. 9.) The latter is again overlain unconformably clay and that sedimentation on this border of quartzes, zoisitized feldspars and pyroxenes partly exposed in Delaware and Maryland have been in i by the Cohansey, of later Miocene age, while the Appalachia ceased. The amount of material or completely altered to hornblende. this way gradually transgressed toward the north Quaternary formations rest everywhere unconform deposited in Paleozoic time which has disappeared in New Jersey and Pennsylvania by the Raritan through subsequent erosion is not known, but was NEWARK GROUP. ably upon the underlying deposits. formation, while toward the south the Raritan is An epitome of the oscillations of the Coastal presumably considerable. By N. H. DABTON. itself gradually transgressed by the Upper Creta Plain in this district is as follows: On the New Jersey Piedmont Plateau there is a General relations. The Newark rocks in the ceous formations until it finally disappears in partial record of overlapping sedimentation during Subsidence and deposition of the Patapsco formation. Philadelphia district constitute the southern portion southern Maryland, the Matawan deposits resting Uplift and erosion. Silurian and Devonian time, followed by an uplift of an extensive monocline in which the strata dip directly upon the Patapsco. Subsidence and deposition of the Raritan formation, -with with open folding, faulting, and slight metamor northerly tilting. north or west of north at angles of 12° to 20°. The Upper Cretaceous formations from the Uplift and erosion. phism. Owing to this structure the formations outcrop in Magothy to the Manasquan, as well as the Eocene Subsidence and deposition of the Magothy formation, with Beginning perhaps at the close of Devonian time regular succession from older to younger from Shark River marl, are similarly transgressed from southerly tilting. and continuing until the close of Paleozoic time, Uplift and erosion. southeast to northwest. The dip is due to tilting New Jersey southward by the Aquia formation, of Subsidence and'deposition of the conformable sequence of there were earth movements along the Atlantic of the strata, and not to inclined deposition, for later Eocene age, although the probable northward Matawan, Monmouth, and Rancocas groups, with southerly border Avhich resulted in the uplifting, folding, and tilting. the bedding planes of the shales, with ripple extension of the latter is again buried by trans Uplift and erosion. recrystallization of these sediments. The eroded marks, rain-drop impressions, and footprints, are gressions of Miocene strata, with the result that Subsidence and deposition of the Kirkwood formation, pre-Cambrian crystalline rocks were further all tilted. Cross-bedded sandstones often exhibit the Shark River and Aquia formations nowhere with northerly tilting, accompanied by extensive transgres deformed and faulted; the Cambrian beach deposits sion over the latest Cretaceous and Eocene formations. dips of deposition, but the layers incline in vari come into actual contact so far as known. Uplift and erosion. were altered to quartz conglomerate, quartzite, and ous directions. The monocline is not traversed by Although the lowest beds of the Matawan group Subsidence and deposition of the Cohansey formation, quartz schist; the calcareous sediments were meta with northerly tilting. folds in this district, as it is in some other portions still outcrop as far southward as southern Mary Uplift and erosion. morphosed into calcareous schist and crystalline of the Newark area. land, they disappear in Virginia below the Aquia Subsidence and deposition of the Lafayette formation, limestone, and the sandy clay deposits were consol Local dips. The direction of dip in this region formation, being represented in that State only in accompanied by an extensive transgression. idated and crystallized into a schist. Uplift and erosion, producing main drainage lines. is from 18° to 20° west of north through the center deep-well borings near the seaward margin of the Subsidence and deposition of the Pleistocene formations at The uplifting of the sediments above the sea was of the area, and varies from due north to 10° west Coastal Plain. different levels during successive oscillations. probably not a continuous process, but intermittent, of north toward the northeast corner and along Transgression likewise occurs within the series of and while erosion did not keep pace with the Perkiomen Creek. Local variations of small the Miocene formations, the Choptank formation of HISTORICAL GEOLOGY. upward movement, Paleozoic topography undoubt amount are numerous, but the general dip is Maryland gradually overlapping the older Miocene PIEDMONT PLATEAU AREA. edly never exhibited a constructional form i. e., remarkably uniform in direction. The amount of beds toward the north. By F. BASOOM. the arches and troughs of the folded crystallines inclination varies irregularly from 12° to 20° in The marked changes in the sequence-of strata never existed unmodified by erosion. Before the greater part, mostly ranging from 14° to 16° in from one part of the Coastal Plain to the other pro SEDIMENTARY- AND IGNEOUS RECCED. beginning of the next period of sedimentation of the western portion of the area and from 12° to 15° duced by these transgressions are reflected in the The Atlantic Ocean basin and the North Ameri which there is a record they had been eroded to a in the eastern portion. There appear to be no angle and direction of dip of the beds. In general can continental plateau are very ancient. The relatively even surface. large areas of exceptional dips nor any regular the dip is slight, ranging from 40 to 50 feet to the North American continent in its present form, This period, known as the Triassie, is separated regional variation, except a general diminution mile in the earlier Cretaceous formations to 10 to 15 however, is much younger. At the time geologic by a long interval of time from Paleozoic sedimen- Philadelphia.. 18 tation. There was time enough during this interval deposits were accumulating on the border of the an uplift and an erosion interval of long duration. Drainage may in like manner be superimposed for the formation by uplift and the removal by Plateau. Later the inland basin disappeared, the During this period portions of the Coastal Plain by peneplanation. The streams which cross Chester erosion of mountain ranges, and finally the devel Delaware estuary narrowed, and the later Pleisto were intermittently beneath and above water, but Valley are superimposed by the peneplanation opment of great tidal estuaries or inland basins cene deposits are to be found in the Philadelphia the Piedmont region remained above water contin subsequent to which the valley developed. embracing all the areas now covered by Triassic Piedmont only on the margin of the Plateau. uously until Lafayette time, when all the Coastal Chester Valley is exactly confined to the outcrop formations. At the close of Pleistocene time estuaries disap Plain and part of the Piedmont Plateau were of the Shenandoah limestone and is not now occu These basins were long, narrow troughs roughly peared, the coast line assumed its present position, brought beneath the sea by tilting which raised pied by a stream, nor does it show evidences of parallel to the coast and extending from Hudson and the physical geography of the district the northern half of the plateau. Stream velocity such occupation at any time; but, on the other River through New Jersey and Pennsylvania into approached that of the present day. was accelerated so that the streams were able to hand, it is crossed in the Philadelphia district by Virginia and North Carolina. They were probably carry to the sea coarse as well as fine gravel. This tributaries of the Schuylkill and west of this dis due, not to erosion, but to warping or faulting, and PHYSIOGRAPHIC EECOED. was true for the first time since early Cretaceous trict by tributaries of the Delaware. The limestone early in their history possessed shores steep enough It was stated in the "Introduction" that the time. The uplift which followed this tilting, and yields to weathering much more readily than does on the west at least to supply to the basins quartzose present form of the Piedmont Plateau is not a which brought the continental shelf as well as the the quartzite or the schist adjacent to it, but does gravel and calcareous cliff debris. A quartzose con constructional form, and that the rock structure is Coastal Plain above water, inaugurated a drainage not show the same difference in resistance to glomerate and a limestone breccia which has consid discordant with the surface. which could not have been very unlike that of the mechanical corrasion. Chester Valley must have erable local development on the western border are If the comparatively slight depressions made by present. The lower courses of the Schuylkill and developed since the peneplanation and presumably evidences of this earlier configuration of the land. the present streams were filled in, a perfectly level the Delaware became established along the present by means of differential weathering. Huge reptiles, now extinct, and smaller vertebrate plain would result, sloping seaward. If, on the other lines and the development of the present topography The Wissahickon and the Schuylkill, crossing animals wandered over these sand flats, and their hand, the arches and troughs of the original anti began. The gorges carved in the continental shelf, the limestone valley and cutting gorges in hard tracks imprinted on the soft mud are now preserved clines and synclines of the underlying rock were mentioned in the "Introduction," date from this gneisses, are examples of superimposed streams in the indurated mud stone or shale. restored, a region of lofty mountains and deep erosion interval. superimposed by peneplanation and by sedimenta Before the close of the period of Triassic sedi valleys would be developed. These two strikingly Following this time of active erosion there was tion. The peculiar courses of Gulf and Valley mentation igneous material was intruded between unlike topographies are separated by a long and a subsidence of the eastern portion of the Pied creeks, both of which have cut through divides the beds, or traversed them in the form of dikes, or more or less complex erosion history. It is to be mont district, sufficient to admit the entrance of composed of relatively hard materials, are due to flowed out at the surface. Following the consoli doubted whether the perfect constructional form estuarine waters upon the margin of the Plateau. superimposition. The secondary tributaries do not dation and accompanying the uplifting and gentle ever existed, but a greater height of land than A stationary position of the shore line is indicated show the characters of superimposed streams, but tipping of these sediments there occured seismic exists at the present time must have characterized by the escarpment crossing the Plateau diagonally are adjusted to the constitution of their rock bed. movements which dislocated the sandstones and this region during some portion of Paleozoic time. from southwest to northeast, described in the Intro This fact and differential weathering explain the shales and the associated igneous rocks. These This height of land was so far reduced at the duction. The 180-foot contour approximately out diversities of topography which have been noted in formations were ruptured and displaced by slipping opening of Triassic time that it was upon a com lines the escarpment, which extends from Gordon that portion of the Plateau in which the Paleozoic along the planes of rupture. paratively level and deeply eroded floor that the Heights northeastward to Somerton. It can be and pre-Paleozoic rocks are uncovered. There is little, if any, record in the Philadelphia materials of the Triassic were laid down. easily located by the present boundaries of the COASTAL PLAIN AREA. district of events which took place in the following The later sediments of the Paleozoic series of the earliest Pleistocene deposits, though erosion has By W. B. CLARK. period, the Jurassic. Erosion rather than sedi Appalachian region must, in large measure, repre removed this material for the most part from the mentation marks this period. Toward the close of sent material removed from this belt of high land immediate neighborhood of the former shore line. GENEEAL STATEMENT. Jurassic time, however, and at the opening of the when the main drainage basin discharged in a In the vicinity of Somerton it is a well-defined The later geologic formations along the Atlantic succeeding period, the Cretaceous, estuarine con western sea. During Triassic time the portion of escarpment, from which the plain of estuarine border form a low plain of varying width that ditions are known to have prevailed. the Plateau east of the Triassic estuary drained erosion to the south may be overlooked. This extends from the New England coast to the Gulf. The basin of the most inland estuary was located northwestward into this estuary and furnished escarpment is the western wave-cut shore of the The deposits consist of a succession of gravels, along the eastern edge of the old Triassic estuary. materials to the sediments accumulating there. broad estuary whose eastern shore is located on sands, clays, and marls, with a gentle dip toward This is inferred from the fact that in the Philadel The reduction of the surface of the Philadelphia the Coastal Plain to the east of the Philadelphia the southeast. Representatives of nearly every phia district deposits of the Cretaceous estuary lie district must have continued during Jurassic and district and whose waters found access to the open epoch from the Upper Jurassic or the Lower Cre immediately upon a deeply eroded crystalline floor, early Cretaceous time. It was during this time sea to the southwest, following the submerged taceous to the Recent are recognized, the oldest from only a part of which a Triassic cover has been that a nearly featureless plain sloping seaward was channel of the post-Lafayette and pre-Pleistocene formations in general being found along the western removed, and also from the fact that they gained formed. Such a plain, carved by subserial erosion, Delaware River. side of the Coastal Plain and the younger forma some of their material from Triassic formations to the work of the atmosphere and of running water, The uplift which interrupted the deposition of tions successively farther east. the west. These deposits are now found in outly is called a peneplain. Only peneplanation can early Pleistocene materials in these waters reduced A detailed study of the character and distribu ing areas on the Piedmont Plateau, left in scattered explain the even skylines of the ridges and hills, the limits of the estuary, and in middle Pleistocene tion of the several formations shows that the angle pockets by subsequent erosion; they occur also as and the discordance between surface configuration time a second stationary position of the shore line and direction of the tilting were not constant from a continuous deposit in the basin of the Delaware, and underground structure. The time of the pene is marked by the 60 to 80-foot escarpment on the Cretaceous time onward. The oscillations resulted where a second estuary was located. They are still planation is established by the age of the deposits Plateau and the 100-ioot efecarprnent on the Coastal in transgressions of the waters with their accom mainly unconsolidated. borne upon its surface. A peneplain of so vast a Plain. The final position of the shore line before panying sediments, which at several periods entirely About the middle of Cretaceous time the barrier scope as that of which the Philadelphia district is the contraction of the estuarine waters to the present overlapped locally the earlier formations, burying between the Delaware estuary and the sea disap an insignificant part is necessarily not of the same channel of the Delaware is preserved in the first from view their landward exposures and bringing peared and the Paleozoic crystallines bearing a age throughout its extent. Peneplanation, begins escarpments on either side of Delaware River, the about at times the deposition of some of the later cover of early Cretaceous deposits were submerged along the main drainage lines, but spreads with 20- to 60-foot scarp on the west and the 45- to formations far to the westward of any outcrops of beneath the Atlantic. This submergence, scarcely incredible slowness away from these lines. Thus 58-foot scarp on the east. The late Pleistocene the earlier deposits.
reaching west of the Delaware, was gradual, as the the eastern border of the Piedmont region may shore line is more stronglyO t/ marked on the Plateau Denudation at various periods down to the pres character of the deposits of this period indicates, have been reduced to a peneplain and even sub than on the Plain. An unequal tilting gave an ent has left remnants of all formations scattered as and was accompanied by seaward tilting and land merged while erosion was still progressing on the opportunity to cut into and expose the crystallines outliers along the western margin of the main ward uplift. Erosion of the Plateau was renewed western margin. of the Plateau. bodies of the deposits. With the exception of the and furnished material for thick beds of clay and The oldest deposits on this border are the Since Pleistocene time both Piedmont Plateau Pliocene and Pleistocene formations, however, the sand. While, on the whole, during later Cretaceous Patapsco and Raritan formations, belonging indis and Coastal Plain have been continuously above chief outcrops of the several formations in the time depression of the sea floor increased at the putably to Lower Cretaceous time; the peneplain water, and the drainage of the Plateau has assumed Philadelphia district are successively encountered same time that erosion, lowering the surface of the also carried Upper Cretaceous, Tertiary, and its present form. The pre-Cretaceous peneplain in crossing the Coastal Plain from northwest to land, decreased the activity of the streams, which Quaternary deposits. The presence of these depos now stands at a height sufficient for the establish southeast. Farther toward the south also the nor consequently supplied a diminished amount of its and their character indicate that in this region ment of a drainage actively eroding its surface. mal succession of most of these formations is shown, mechanical sediments, there must also have been submergence terminated Jurassic peneplanation The cover of Cretaceous, Tertiary, and Quaternary although the relations of the Pleistocene deposits to oscillation of the level of sea floor and land surface, and that this submergence was not due to a single formations has been so far removed as to lay bare the other members of the series are complicated accompanied by variations in the angle and direc crustal movement but to an interrupted and com large areas of the crystalline peneplaned floor. The because of the extensive erosion that took place at tion of the tilting. The interbedding of sand, plex series of movements. streams have not only eroded the cover, but have the close of the Tertiary period and the consequent gravel, and clay which characterizes the deposits of First there was subsidence with tilting, which cut into the crystalline rocks. The peneplain which submergence of the valleys throughout the coastal this period indicates temporary increased activity produced estuaries bordering the sea and extending thus by uplift became a plateau has by the renewal area. of the streams, while the change in direction and ,inland roughly parallel to the present sea border. of erosion become a dissected plateau. POTOMAC HISTOEY. amount of dip of these formations indicates a warp In these estuaries were deposited the clay and gravel Post-Jurassic peneplanation on the western mar ing of the sea floor. The deposits of Upper Cre of the Patapsco formation. An uplift followed gin of the Piedmont Plateau is recorded in traces A great variety of conditions characterize the taceous time have suffered little, if any, alteration which brought the Piedmont district above the sea. of three peneplains, which, on the eastern margin, deposition of the Coastal Plain sediments. During since their deposition. The erosion which succeeded this uplift removed embracing the Philadelphia district, can not be the earlier periods of this history estuarine condi The periods following the Cretaceous, the Ter the Patapsco deposits, except from the deepest por discriminated from the older peneplain. tions prevailed throughout the region. A great tiary and Quaternary, were marked by a changing tion of the inland estuary. It was stated in the "Introduction" that the estuary, the extent of which can be no longer deter shore line, by renewed uplift'of the Appalachians, Following upon the erosion interval was a second larger streams maintain courses which are inde mined, occupied a depression in the Piedmont sur by the doming of the Piedmont Plateau, and by subsidence and the renewal of estuaries in which pendent of the lithologic character and structure of face and followed in general the main structure the glaciation of northern North America. The Raritan deposits were laid down. The uplift that the underlying rock. An explanation of this fact lines of the Appalachian uplift. ' Just when this accelerated rivers, supplied from the ice sheet and followed was more marked than the preceding and is found in the presence of the cover of Cretaceous, later estuary was formed can not be definitely deter the Plateau, furnished abundant sand and gravel the district remained above water a long time, Tertiary, or Quaternary materials which, existing mined, but the dinosaurs which have been found in for the thick deposits of these periods. These during which extensive erosion took place. The at the time of the development of the drainage, one of the lower formations have led soipe eminent deposits, while in the main spread upon the third subsidence, which followed this erosion inter masked the pre-Paleozoic and Paleozoic formations vertebrate paleontologists to regard the^ge as late Coastal Plain, also accumulated in estuarine waters val, lasted during all Upper Cretaceous time, was beneath it. The drainage, superimposed upon this Jurassic. The plant forms found in these earlier bordering the Piedmont Plateau, and extended more extended than any of the preceding, and was cover, became too well established in courses conse beds likewise show certain Jurassic affinities, but during Tertiary time 10 miles west of Delaware oscillatory in character. The adjoining land inust quent on the slope of the Plateau and independent primitive dicotyledonous types also occur, which on River. In early Pleistocene time an inland basin have been low, so that the streams furnished only of the concealed rock floor to alter these courses the whole have led paleobotanists to regard even occupied part of Chester Valley, while estuarine fine sand deposits. Following Cretaceous time was when subsequently the rock floor was uncovered. the oldest beds as early Cretaceous. 19
Uplifts and depressions took place during the the outset by extensive deposits of clays and sands. toward the west had become extensively elevated Thejquarries are conveniently located for transpor time of formation of these estuarine deposits, which The sea encroached over a more or less even floor, as the Tertiary period advanced, causing the streams tation. are collectively known as the Potomac group, and producing sediments that had their origin in the to transport large amounts of coarser materials Wissahickon gneiss. The Wissahickon gneiss which have been divided in Maryland, where the still unconsolidated materials of the earlier Creta down their courses to the sea. A great thickness of furnishes a very acceptable building stone, which most complete sequence occurs, into the Patuxent, ceous as well as in the older rocks to the west. highly characteristic sandy deposits was laid down, is accessible, easily quarried, and readily dressed. the Arundel, the Patapsco, and the Raritan forma Marine life was abundant and varied, an extensive which farther off shore or in regions remote from The joints and bedding planes are such as to permit tions. Of these, the two lower have been doubt fauna of cephalopods, gasteropods, and pelecypods the mouths of streams became finer, with beds blocks to be quarried of sufficient size for ordinary fully referred to the Jurassic because of the verte characterizing the period. The conditions of sedi of clay bearing an extensive molluscan fauna. Ibuilding purposes. The color of the stone is a brate remains, as above mentioned, in the Arundel mentation changed during this time, especially in Toward the south in Maryland, where these warm gray, the grain medium. In hardness and beds. So far as known, neither of these formations the north, where a clearly defined differentiation deposits are most characteristically developed, a durability the stone is somewhat variable; although appears at the surface within the Philadelphia dis in the materials occurs. Southward this feature is great number of species have been recognized. it disintegrates readily when exposed at the surface trict, the earliest of the Potomac beds being refera less pronounced and the deposits gradually become The latest portion of Miocene time is represented of the ground, experience has shown that it wears ble to the Patapsco, of whose Cretaceous affinities more homogeneous, the distinctions being entirely east of the Philadelphia district, by deposits of sand very well if properly laid in a building and that there can be no doubt. Land conditions existed at lost in Maryland. and clay which are now buried beneath a cover pleasing effects may be obtained with it. the close of Arundel time, as shown both by a of Pleistocene materials. In the deeper well bor Near Walnut Lane station, on the Philadelphia marked unconformity between the Arundel and MONMOTJTH HISTORY. ings along the coast and toward the south in Mary andl Reading Railroad, a quarry owned by Glassy Patapsco formations and by the existence in the The advent of Monmouth time was not marked land these deposits afford sands and clays that & Fowler has furnished stone for Blair Hall, strata of certain lignitic deposits, the tree stumps of by any pronounced change, sedimentation having lithologically are not unlike those of the earliest Princeton University; for Memorial Chapel, Wil which are to-day found in an upright position. continued without interruption. As the period period in many respects, although generally finer, liams College; and for the library at Vassar Col With the advent of Patapsco time a consider advanced, however, thick - bedded glauconitic indicating in all probability the lessening volume lege. At Mermaid a quarry owned by Jerry able widening of the estuary took place, and it is deposits were laid down, and the greensand of of sedimentation. O'Neil has furnished stone for .Rockefeller Hall possible that the Philadelphia district was then for the Monmouth is very unlike anything which and the library at Bryn Mawr College. The gym the first time submerged. Potomac time closed had preceded it. The middle formation of the PLIOCENE HISTORY. nasium, Dalton, Denbigh, and Pembroke halls of with the deposition of the Raritan formation, the Monmouth, known as the Navesink marl, is a char The close of the Tertiary along the Atlantic and Bryn Mawr College are built of stone furnished by most extensive of the early Cretaceous formations acteristic greensand marl, and in its numerous Gulf borders is marked by the deposition of a cover Hayden's and Foulton's quarries, on the west side represented in the Philadelphia district and neigh fossils shows the extensive marine fauna that of gravels and sands. This was brought about by of the Schuylkill. Many private houses in Ger- boring areas. Deposits coarser than the preceding existed at this period. Many of the species are landward uplift accompanied by a depression of mantown and throughout the suburban districts Patapsco characterize the Raritan, and it would different from those of earlier time, although many the shore line, since the deposits of the Lafayette are'built of this stone. seem that considerable deformation of the shores of fossils are found common to one of the zones of the formation, which has been thought to represent the Chickies quartzite. There are large quarries in the ancient estuary must have been in progress, earlier Matawan and to the later Redbank. The Pliocene, are found distributed widely above the the Chickies quartzite at Edge Hill and between later culminating in the breaking down of the red sands found both above and below the green- Miocene strata as well as those of earlier time, Edge Hill and Abington. Quarries have also been eastern barrier and the entrance of the open waters sand marl are quite unknown at later horizons, reaching to the crystalline rocks of the Piedmont worked in the quartzite of Huntington Valley and of the Atlantic. except in the northern phase of the later Rancocas. area, Within the Philadelphia district these in the neighborhood of Chestnut Hill. The mate Locally the beds are highly calcareous on account deposits .are to-day limited to the Piedmont rial is quarried in thin slabs cut parallel to the MAGOTHY HISTORY. of the great number of molluscan remains entombed Plateau, lying to the west of Philadelphia, so that steeply dipping cleavage and bedding planes, and The date of the change just mentioned was evi in the deposits. their relations to the other Tertiary formations is used for cellar walls, furnace linings, and, in a dently not earlier than the close of the Lower Creta must be sought in Maryland and Virginia, where limited way, for building purposes. ceous. At first the marine faunas, which apparently RANCOCAS HISTORY. they are more fully developed. The period of time The quartzite of the North Valley Hills is quar entered the basin of deposition in the Raritan Bay "With the close of Monmouth sedimentation came represented by the Lafayette must have been short, ried extensively. The material is transported to region, did not extend far southward, for the Mago- a time of pronounced glauconitic accumulation. and was terminated by extensive uplift of the sea Valley Forge, where it is crushed and shipped to thy deposits in the Philadelphia district and toward The greensands of the Hornerstown constitute the floor, during which time the present drainage lines iron works throughout the Schuylkill Valley and the south have not as yet afforded marine fossils. most significant beds of glauconitic materials in the of the Coastal Plain were largely developed. used for bottoms in heating furnaces and steel It seems probable that the encroaching sea merged entire Cretaceous system. They represent quiet works. Twenty-five to 50 tons are shipped daily. into an extensive estuary that extended southward seas, in which the accumulation of materials must PLEISTOCENE HISTORY. /Shenandoah limestone. The Shenandoah lime along the old line of Potomac sedimentation across have been extremely slow. The land area to the In these ancient channels and on the adjoining stone is always crystalline and much of it is a white Delaware to the western shore of Chesapeake Bay. west by this time had become reduced to a feature lowlands the deposits of the Pleistocene epoch were or blue marble of medium grain. The stone is The same is probably true in a measure northward, less peneplain, while the sea floor itself may have laid down. The materials consist of gravels, sands, fairly accessible throughout Chester Valley and although the exact limits of the so-called " Island been still further depressed, carrying the area of and clays that were to a considerable extent derived can be quarried parallel to the bedding and joint series," on which this generalization must be based, sedimentation farther landward. Conditions must from the earlier Coastal Plain strata, although the planes, yielding blocks which range from 5.94 by are not fully comprehended. The flora of the in any event have persisted through a considerable streams flowing from the Piedmont Plateau added 5.90 by 5.92 feet in the vicinity of Conshohocken, Magothy strata suggests that this change was not period, for the thick deposits of nearly homogene their quota to the materials deposited. The life of where the formation is somewhat thinly bedded, consummated until late Cenomanian time, and the ous greensand extend throughout the district from the Pleistocene approached more nearly that of the to 6,50 by 6.05 by 6.03 feet in the open valley. fauna points even to the Senonian. Magothy time Raritan River southward to the point of their Recent, although relatively few localities are known The average crushing strength of the stone per apparently represents a transitional period between final disappearance near the Maryland border. in the north Atlantic coastal region in which any square inch, calculated from eight samples, is the estuarine conditions of Potomac time and the The Rancocas closed with an extensive accumula considerable assemblage of Pleistocene species 12;075 pounds. distinctly marine conditions that characterize the tion of quartz deposits, known as the Vincentown occurs. There are now more abandoned than active remainder of the Cretaceous. sand, which are in places largely made up of the The blocking of the minor post-Lafayette chan quarries in the Shenandoah limestone, notably at remains of Bryozoa and Foraminifera, forming a nels in later Pleistocene time produced ponded Five Points, Plymouth Meeting, Marble Hall, Port MATAWAN HISTORY. lime sand, and are at other places decidedly glau- areas in which were laid down the thick deposits Kennedy, New Centerville, and Rennyson. In the The materials composing the marine sediments coiiitic. These deposits where calcareous are of black clay so typically developed at Fish House early history of Philadelphia, marble from Chester are mainly sand and clay, which from the base of among the most striking in the entire Cretaceous and at numerous other points toward the south, Valley was in great demand for house trimmings, the group upward contain greater or less amounts system of the north Atlantic Coastal Plain, and through New Jersey, Delaware, and Maryland. doorsteps, and for more elaborate architectural pur of glauconite, showing that during much of the indicate a great profusion of life in the seas of the poses. The sarcophagi at Mount Vernon, Va., and time land-derived materials must have reached the time. ECONOMIC GEOLOGY. the marble blocks contributed by the State of area of deposition in small amounts. It is probable Pennsylvania to the Washington Monument were MINERAL RESOURCES. that the region was not far removed from the shore LATE CRETACEOUS AND EOCENE HISTORY. quarried in Chester Valley, which has also fur line of the period, and that the land had been A long period of time passed after the close of PIEDMONT PLATEAU AKEA. nished stone for Girard College, the United States gradually reduced until a great peneplain had Rancocas deposition before the next younger sedi By F. BAsqoM. custom-house at Philadelphia, and many other been developed, extending westward at least into ments of the Philadelphia district were deposited. In the Piedmont Plateau area the chief natural noted buildings. Within the last fifty years Ver the Appalachian district. The evidence for this is The record of these times is represented in the products of economic importance are building stone mont marble, owing to its greater beauty, its free found not only in the glauconitic character of the Manasquan formation, of late Cretaceous time, and and road metal. The former product is supplied dom from iron pyrites, and the cheaper methods of sediments throughout late Cretaceous and early the Shark River marl, of early Eocene time, to a greater or less degree by all the formations of quarrying it, has gradually replaced the Chester Tertiary time but also in the even-topped ridges developed mainly toward the north, and in the the Plateau, and the latter in large amount by sev Valley stone. At present the Shenandoah limestone throughout the Atlantic border district as far back Aquia and Nanjemoy formations, of middle eral of the formations. is more frequently quarried for use as lime and road as the Allegheny Plateau. A marked similarity Eocene time, developed mainly toward the south metal than to furnish building stone. Large quarries BUILDING STONE. in composition characterizes these late Cretaceous in Delaware and Maryland. are being operated at Williams station, at Plymouth sediments, from the Matawan to the Manasquan, Baltimore gneiss.- The Baltimore gneiss, of which Meeting, and, intermittently, at Mogee, the stone MIOCENE HISTORY. as a whole, although they vary sufficiently over the character and distribution have been discussed, from which is burnt for lime. At two localities considerable areas to make it possible to separate Evidently much the same conditions as hitherto does not furnish a large amount of building stone one-half mile west of Plymouth Meeting and a mile them on lithologic grounds into several formations. prevailed along the Atlantic border, as far as can in the Philadelphia district. The granitic facies west of Port Kennedy the limestone is utilized Glauconite in greater or less amounts appears, as be judged from, the deposits farther south, until supplies a better stone than the sedimentary facies, for the manufacture of magnesium carbonate by above stated, at nearly all horizons, in places con Miocene time. The deposits of the earliest period whose serviceableness for building purposes is the American Magnesia and Covering Company, stituting the main body of the deposits, while in are for the most part clays and fine sands, although reduced by its finely banded character. Between and the Ehret Magnesia Manufacturing Company, other places it is sparsely distributed and may be in the extreme southern part of New Jersey occur Bethayres and Paper Mills, on Pennypack Creek, respectively. The product is used for magnesia limited to definite beds or may occur as small marl beds which by their numerous fossils show there are large quarries in the massive phase of the steam-pipe and boilerr coverings and locomotive lenses or patches inclosed in other materials. In the existence of an extensive molluscan fauna. To gneiss, from which fair building stone has been lagging. general the beds become gradually more glauco the south, however, extensive diatomaceous beds taken, as well as a large amount of road metal. Three-fourths of a mile southeast of King of nitic in passing upward in the series, the highest give evidence of the existence of vast numbers bf The rock possesses a nearly vertical jointing, is light Prussia a quarry in the limestone yields both light- beds consisting in places almost entirely of diatoms in the seas of early Miocene time. colored with gray bands, and is medium to coarse colored and dark-blue marble. This stone is used glauconite. Unlike the early Miocene sediments of this grained. It resembles in appearance the granite for monuments and other ornamental purposes. The opening period of this later division of the district, the later deposits consist of coarser sands gneiss at Port Deposit, to which in hardness, At Howellville a large quarry is successfully oper Cretaceous, known as the Matawan, was marked at and fine gravels, which show that the land areas strength, and durability it is probably not inferior. ated. The stone is used for concrete, ballast, Philadelphia. 20 macadam, and building purposes, and is shipped by these quarries have been operated almost continu quantity of rock fragments of definite size; tough River to Buck Ridge the soil is chiefly a brownish- railroad to points within a radius of 50 miles. ously for more than a century. Bridges, curbing, ness is the power possessed by a material to resist buff micaceous clay loam derived from the decay of For a distance of five-eighths of a mile northwest dwelling houses, churches, public buildings, and fracture by impact; hardness is the resistance which the Wissahickon mica gneiss. This is exclusive of of West Conshohocken, on both sides of Schuylkill monuments have been made from the stone. It a material offers to the displacement of its particles an alluvial soil confined to the lowlands in the River, the limestone contains so low a percentage of has horizontal and vertical partings, which enable by friction; cementing value is the power possessed immediate vicinity of the Delaware and limited lime as to unfit it for burning into lime. There it. to be quarried in cubical blocks, and is strong, by a rock powder to bind the coarser fragments. areas of a loose sandy soil; these soils are described are three quarries in this lime-poor rock of calcare durable, and attractive. Tests of the crushing Physical properties of road metal. later among the Coastal Plain products, the former ous schist on the west side of the river, operated by strength of granite gneiss from Holmesburg made [Edwin C. E. Lord, BuU.'No. 31, U. S. Dept. of Agr., 1907.] as the Meadow and the latter as the Norfolk sand. the West Conshohocken Stone Company, and a like in 1902 by Lathbury and Spockman gave the The clay loam is characterized by the presence of Per Tough Hard Cement number on the east side, controlled by the Schuyl following results: Crushing strength per square Metal. centage ing Specific abundant fragments of mica, of gneiss, and of vein of wear. ness. ness. value. gravity. kill Stone Company and the Philadelphia and inch on edge, 24,034 pounds; crushing strength quartz. It is a mellow, fertile soil and grades Conshohocken Stone Quarry Company. This per square inch on bed, 26,254 pounds. Biotite granite ___ 4.4 10 16.8 17 2.64 imperceptibly into solid rock through a considera stone is used for constructing railway bridges and Hornblende gneiss. The hornblende gneiss is Grabbro. 2.8 16 17.9 29 3.00 ble depth of decayed rock. It corresponds to soil in foundations for heavy buildings and for wall quarried at Frankford and Queen Lane. Stone Fresh diabase __ 2.0 30 18.2 49 3.00 which, in adjacent regions in Maryland, has been Altered diabase.-.. 2.5 24 17.5 156 2.95 work requiring a nice face. These quarriess also from Frankford is used for cellar walls and for designated by the Bureau of Soils, Department of Limestone ._ 5.6 10 12.7 60 2.70 furnish standard foundation material. dwellings. Stone from McKinney's quarry, Queen Agriculture, the Cecil mica loam. The names of Octoraro schist. The mica schist is an inferior Lane, is used for Belgian blocks, for bridge build soils used in this folio are those adopted by the IKON ORE. stone for economic use of any sort. In a very ing, and for schoolhouses. Bureau of Soils, Department of Agriculture, and small way it has been quarried at numerous locali Sandstones in the Newark. The sandstones of In the pockets here and there throughout Ches are not in any sense of the term geologic names. ties, where the material taken out has been used for the Stockton, Lockatong, and Brunswick formations ter Valley is found a limonitic iron ore. In places The decay of the granite gneiss forms a very cellar walls. One of the larger quarries is at have been quarried to some extent to supply build it is accompanied by hematite. Its presence is due similar soil, which often is scarcely to be distin Bridgeport Hill, where the siliceous character of ing stone for local use. The sandstone of the to the segregation of the iron oxide upon the lime guished from the mica loam. It is a clay loam the rock renders it fairly serviceable for founda Stockton is of gray to buff color and much is of stone by leaching from the mica schist. This must showing fewer fragments of mica. It is not con tions. Sand for local use has been obtained from sufficient hardness and homogeneity to be of con have taken place subsequent to the folding of lime fined exclusively to the areas underlain by granite, a pit opened in the disintegrated quartzose member siderable value. The most extensive quarries are stone and schist, and has been deposited in disregard but is a residual product of the less micaceous of the mica schist, three-eighths of a mile west of in the bluffs on the north bank of Schuylkill River of stratification. These iron-ore pockets were at gneiss. This soil has been designated the Cecil Radnor and 2 miles north of Wayne, on the road 3 to 5 miles above Norristown and at Grenoble, one time mined, as the numerous pits distributed loam. to King of Prussia and near the northern base of but they are only worked occasionally to supply throughout the limestone area testify, but of late The gabbro which constitutes the greater part of the South Valley Hills. This pit is operated by some transient demand for stone. There are small years the iron interests have been diverted to other Buck Ridge disintegrates into red clay soil thickly James Fletcher of Mount Pleasant, Wayne. quarries half a mile north of Fort Washington, in and more profitable districts. set with tough bowlders of gabbro. The soil is not Gabbro, diabase, serpentine, and soapstone. the eastern part of Norristown, at Warrington, and as deep as on the mica gneiss and gives place some FELDSPAK. Gabbro has been used somewhat as a building half a mile north of Horsham. what abruptly to solid rock. This soil character stone. It is very tough for quarrying, but on the The hard, dark-colored, slabby sandstones of the Penetrating the gneisses, particularly in the izes the broken hilly country. It corresponds to other hand can be worked in blocks of any size Lockatong formation are extensively utilized for southwestern part of the Philadelphia district, are the Cecil clay of the Bureau of Soils. The Balti desired and is a permanent stone with a crushing underpinning and are crushed in large amounts for pegmatitic masses or dikes which in a few instances more gneiss supplies a sandy clay soil like the Cecil strength twice that of limestone. It is, however, road metal. The principal quarries are on the furnish feldspar of a marketable character. The clay, free from mica scales, but possessing a yellow too dark colored to be popular as a building stone, main road halfway between Spring House and dikes are usually composed of a coarsely crystalline rather than a red color, and containing flat frag but is suitable for curbing and for Belgian blocks. Montgomery Square and a half mile northeast of aggregate of microcline, albite, quartz, and mus- ments of the gneiss. This sandy clay soil and the Diabase, which has been used in ornamental the latter place. Many small openings have been covite. In many of the granite quarries in the Cecil clay clothe Buck Ridge. stone walls and in the construction of stables, is, made at other localities. neighborhood of Chester such pegmatitic masses The mica schist of the South Valley Hills forms like the gabbro, too dark colored for general use in The brownish-red sandstones of the Brunswick have been exposed. a yellow micaceous sandy soil, differing from the dwelling houses. formation are as a rule too soft to be of use for The Chester Heights Feldspar Company, located mica loam, chiefly in a larger content of sand, in Serpentine usually occurs badly jointed, but building, but they serve to some extent for local at Chester Heights, about 6 miles southwest of freedom from mica plates, and in containing many notwithstanding this feature, the stone has had a use. A small quarry on the east side of Perkiomen Media, furnishes feldspar both for dental purposes small fragments of mica schist. The limestone wide use for building purposes because of its soft Creek 1|- miles above Graters Ford has been worked and for pottery. One mile east of Glen Mills, on valley beyond is characterized by the reddish clayey ness and consequent ease of quarrying and dressing, at intervals for many years and yields a rock of the Sharpless estate, there is an abandoned feldspar soil which normally results from the decay of lime its remarkable durability, and its soft green color. hardness unusual for that formation. and mica quarry. About 1^- miles south of Chelsea stone. It is free from stones, is deep, and is very Many dwelling houses, churches, and the older a potash feldspar has been quarried. On the east productive. Some of the best farms of the plateau buildings of the University of Pennsylvania and of KOAD METAL. bank of the Schuylkill River, in the Baltimore are located on this soil. It corresponds to the the Academy of Sciences at Philadelphia are built Road metal is abundantly provided by the for gneiss, a mass of acidic feldspar was for a short time Conestoga loam of the Bureau of Soils. of this material. There are no quarries now in active mations of the Piedmont Plateau. The Baltimore quarried. The amount of feldspar in the Philadel The quartz schist of the North Valley Hills, operation in the serpentine of the Philadelphia dis gneiss, the Shenandoah limestone, the gabbro, and phia district is limited, but west of the Philadelphia Camp Hill, Edge Hill, and other highlands gives trict, and much of the serpentine used in Philadel the diabase are utilized for this purpose; Yeakle's region feldspar and the kaolin derived from it sup rise to a sandy soil which contains also both mica phia has been obtained from Brinton's quarry, 3 quarry, one-half mile west of Glenside, and the port an important industry. and clay. It is less productive than the other soils miles southwest of West Chester, west of this district. lower quarries on Pennypack Creek in the Balti because less tillable, being thickly studded with COAL. The rare combination of softness and indestruc more gneiss are provided with stone crushers and quartzite fragments and characterized by a rugged tibility offered by soapstone renders it, when pure, furnish road metal. Limestone has been exten Some very thin beds of coal occur in the dark topography. There is no distinction between soil suitable for a considerable range of application. sively used in road construction. The cementing shales of the Lockatong formation, but most of the and subsoil and it does not exceed 2 feet in depth. Soapstone has but a scanty distribution in the quality of the limestone is excellent and its wearing coal is very impure. Several attempts have been This -corresponds to the Edgemont stony loam Philadelphia district. It is confined to the most qualities are improved by the siliceous character of made to develop coal mines, notably at a locality on mapped by the Bureau of Soils in Lancaster southerly of the serpentine dikes and to the the rock. In durability, however, it is inferior to Perkiomen Creek near Arcola station, where it is County, Pa. neighborhood of Schuylkill River. Even here it the gabbro, and roads macadamized with limestone claimed that a bed 26 inches thick was found. A The serpentine areas -are marked by a thin, is only locally quite pure (steatite) and free from soon present a dusty white surface which may be thin coal bed is reported in wells bored at North light greenish yellow soil. This soil may be only serpentine or serpentinized olivines. These con avoided by the use of gabbro. Some of the quarries Wales and Lansdale. It is improbable that any a few inches deep "or merely lodged in pockets on stituents are much harder than steatite and cause now operated in the limestone furnish stone solely deposit of value exists at this place or elsewhere in the otherwise bare rock. When the serpentine the soapstone to wear unevenly. The Philadelphia for road metal. Such a quarry is situated one-half the formation. soil is deeper it usually has a reddish color. Its stone was once in demand for door sills. Such old mile southwest of Oreland. thinness and consequent incapacity to hold water LEAD AND COPPEK. door sills now show the serpentine knots projecting The hard sandy shades of the Lockatong forma H. ' is a sufficient reason for its unproductiveness. above the soapstone like " hobnails in a plank." tion have been used to a considerable extent in the Traces of lead and copper materials (galenite, Chemically it differs from the other soils in the Soapstone has been much more extensively northern part of the Philadelphia district for road copper pyrites, and the carbonates of copper) occur presence of a large percentage of magnesia and the quarried in the past than it is at present. A metal. in many places in rocks of the Newark group, and absence (or the presence of only an excessively low quarry (Prince's) on the east bank of the Schuyl Of the rocks of the Plateau that are abundant in a single locality in the Baltimore gneiss of the percentage) of lime and potassa and other nutrient kill near Lafayette station, opened more than a and available the best road metal is furnished by Philadelphia district, but not in sufficient amount materials. Where the serpentine soil is deep hundred years ago to furnish door sills for the old the gabbro. Diabase affords equally good or even to give the least promise of value. Such traces are enough to hold moisture and has been treated with State House and for a long time operated, is now better material, but is too meager in occurrence to to be found in the gneiss 1^- miles west by south the usual fertilizers it does not differ from other closed and is partly buried by a landslide. An be of economic importance in the Philadelphia dis of Valley Forge. A pit known as the "Perkiomen soils in productiveness. It has been called the old quarry (Rose quarry) on the west bank of the trict. Gabbro owes its superiority to limestone or mine " was opened half a century ago in the Stock- Conowingo barrens. Schuylkill in the same formation has been recently gneiss as road material to its greater toughness, ton formation and was worked at intervals, but was The soil derived from the disintegration of the reopened and, like Prince's quarry, furnishes mate hardness, and consequent wearing quality. In finally abandoned. It is in the valley of Mine Run, Triassic sandstones and shales covers a larger area rial of good quality, which is used for stove and binding power it is inferior to these stones. north by west of Shannonville; the rock is light- than any other single type of soil in the Philadel furnace linings, as a filler in the manufacture of Large quarries in the gabbro at Wayne, at Glen brown sandstone containing small amounts of cop phia district. It is a sandy clay loam characterized paint and paper, and as a lubricant. Mills, and at Locksley furnish to this district an per pyrites and malachite. At the Acton mine by an Indian red or brownish-red color. Confined Granite gneiss. One of the best building stones inexhaustible supply of crushed stone. A smaller one-half mile west of Shannonville, small traces of as it is to gently rolling country and being com of the district is furnished by the granite gneiss, quarry for the same purpose has been opened on copper pyrites, blende, and galenite appear iri the paratively free from stones, it is tillable and pro whose distribution and character have been dis Little Darby Creek. Gabbro is widely used in excavated material, which is mostly a brownish ductive. This is the Penn loam of the Bureau of cussed: There are large quarries in this formation road construction in the Philadelphia district, which sandstone with sandy shale. Soils. at Holmesburg, at the Falls of Schuylkill on the west is justly famous for good roads. Crushed rock With the exception of the Conowingo barrens, SOILS. bank of the river, at Overbrook (southeast of the from the Glen Mills quarry has been used in mak which support a scanty and characteristic vegeta station), south of Overbrook on Indian Creek, at ing artificial stone for building purposes. The soils of the Piedmont Plateau of Pennsyl tion, the soils of the Piedmont area are not dis Kellyville, and on the lower courses of Crum and In the table given below, percentage of wear vania are residual and are derived from the rocks similar in productiveness. A great variety of Chester creeks. Here are the Avondale, Ward's, represents the amount of material under 0.16 centi which immediately underlie them. They are, with forest trees of fine proportions characterize the Deshony's, and Leiperville quarries. Some of meter in diameter lost by abrasion from a weighed one exception, productive soils. From Delaware plateau. Among them are several varieties of the 21 oak, beech, chestnut, tulip tree, sycamore, basswood, shohocken region, especially near Harmansville and these clays have been used at numerous places in tions of the Bureau of Soils, 1901" describes the hickory, butternut, soft maple, locust, gum, sassa Spring Mill. The clay occurs in deep depressions the suburbs of Philadelphia in the manufacture of soil types for a considerable part of the Philadelphia fras, dogwood, and cedar. in the surface of the limestone that are generally of common building brick. In places the clay has Coastal Plain area, under the following names: small areal extent. The clay is interbedded with been removed over large areas which have later Sassafras loam, Quinton sandy loam, Elsinboro COASTAL PLAIN AREA. sand and gravel lenses of variable character. In been built upon, and it is now being worked in the fine sand, Elkton clay, Alloway clay, Norfolk By W. B. CLARK and B. L. MILLER. some places the clay is as much as 25 feet in vicinity of Frankford, Nicetown, Point Breeze, and sand, Westphalia sand, Collington sandy loam, The mineral resources of the Coastal Plain area thickness, but elsewhere it is only a few feet thick or between Angora and Haddington. The material Windsor sand, Sassafras gravelly loam, and consist of gravel, sand, clay, marl, and soils. No is entirely wanting. The clay is of variable color is a rather tough reddish-brown clay loam and has Meadow. By far the greater part of the Coastal one of them can be regarded as of great economic drab, red, black, and mottled being most common. been formed mainly from the decomposed products Plain of the Philadelphia district is composed of significance except the soils, although industries of It is exceedingly tough, so that the deposits are of the crystalline rocks of the near-by region. The Norfolk sand, Meadow, Sassafras gravelly loam, importance have been established in connection worked with difficulty. The overburden is also clay occurs at the surface, so that little or no strip and Quinton sandy loam, here named in the order with the sand, the clay, and the marl. heavy in some of the pockets, rendering the working ping is required. Where worked the clay loam is of importance. of the deposits unprofitable. from 5 to 18 feet in thickness. The Norfolk sand consists of a loose sand of GRAVEL. The Patapsco clay is the most valuable clay of the On the New Jersey side of Delaware River the medium to coarse texture containing a small per The gravels wherever found have been employed Philadelphia district, although at present not most extensive deposit of Pleistocene clay occurs at centage of silt and clay. It is derived from the to a greater or less extent for road building, the worked as extensively as are some of the Upper Fish House. At this place there is a deposit of several Quaternary formations and is found, at all most important of these materials coming from the Cretaceous clay deposits on the east side of Dela plastic black clay varying in thickness from 20 to elevations from sea level to the highest portions of Magothy, Lafayette, and Quaternary formations. ware River. It is used in the manufacture of fire 30 feet and extending over an area about two-thirds the upland. This soil, which covers a larger area The Lafayette gravel, as earlier described, is con brick, terra cotta, pottery, furnace linings, etc. of a mile long and one-third of a mile wide. This than any of the others, is particularly well adapted fined to the elevated areas west of Philadelphia, Raritan clay. The Raritan formation through clay has been worked for a great many years and is for truck farming. where its loamy and ferruginous character has out New Jersey is the most valuable clay formation by far the largest single clay pit in the Philadel The next most important soil is the Meadow, led to its extensive use on the local highways. of the State and yields a great variety of clays phia district. The clay has attracted much atten which occupies the low areas along Delaware River The gravel and coarse sand of the Magothy suitable for many purposes. In the Philadelphia tion because of the presence of a great many Unio and its tributaries. In the main this land is so are confined to the New Jersey area bordering district the Raritan has a very scanty exposure casts. It also contains considerable lignitic matter low and wet as to be unfitted for agricultural Delaware River. They are likewise highly ferru and very little clay has been utilized from deposits in places. The clay rests on coarse sand and gravel purposes until drained. These meadows supply ginous and well adapted for road building, although of this age. On the south side of Pensauken Creek of the same age and is overlain by a few feet of sur herd's grass in large amount for rough forage, and they have not been employed to any great extent. near its junction with Delaware River white and face loam. It has been mainly used in the manu they also furnish pasturage for cattle. Vegetables The most widely used gravels are those of the mottled clays have been dug to a limited extent. facture of building brick, though some has been are also raised on some of the higher portions, but Quaternary formations, which cap the higher levels The clays are of good quality and are suitable for utilized for stoneware. in general the region is still largely forested, black on both sides of Delaware River and are particularly fire brick, saggers, tile, and some grades of pottery. Some of the Quaternary clay near the mouth of and sweet gum, willow oak, white oak, magnolias, important throughout the New Jersey district as A few years ago a somewhat similar deposit of white Woodbury Creek has been used by the Camden and two or three varieties of cedar being the trees road-building materials. They will doubtless be clay of Raritan age was exposed in the vicinity of Iron Works. most commonly found. The Sassafras gravelly loam, as well as the other much more extensively employed in the future the clay pits at Fish House, but it is not worked GLAUCOISTITE MAUL. than they have been in the past. at the present time. ... types referred to, occupy much more restricted The formations of the Monmouth and Rancocas areas than the Norfolk sand and the Meadow. SAND. MATAWAN CLAYS. groups are rich in deposits of glauconitic marls, The Sassafras gravelly loam occupies the upland Sands of various kinds, both coarse and fine, The Matawan clays are contained in the Mer- which are of value as fertilizers. From New Jersey areas, being mainly derived from the higher-lying occur at several horizons. Those which have chantville, Woodbury, and Englishtown formations to North Carolina such deposits have been worked Quaternary formations. The soil consists of a hitherto been economically employed are for the and are the most extensive clay deposits of the spasmodically since the early part of the last cen brown sandy loam mixed with gravel and is most part confined to the Magothy, Kirk wood, district. tury, when their value was first determined, yet especially well adapted to fruit culture, particularly and Cohansey formations. Immense pits have been Merchantville clay. Clay belonging to the Mer- their importance in enriching the soil has never that of peaches, pears, plums, and cherries. Corn is opened in the Magothy along the south bank chantville formation is worked at Budd Brothers' been generally recognized. They consist of quartz also raised. A forest growth of oak and pine also of Pensauken Creek and the materials have been brick-yard in the southeastern part of Camden, sand with an admixture of many grains of glau covers some parts of the region. shipped in great quantities to Philadelphia and near City Line station. The clay bed is from 14 to conite, a soft green mineral, which is essentially a The Quinton sandy loam is largely derived from elsewhere for general building and other purposes. 16 feet in thickness; it rests upon coarse white sand hydrous silicate of iron and potassium. On account the Cohansey sand or its reworked materials. It The Magothy sand used in this locality consists of of the Magothy and is in turn overlain by a few feet of the glauconite, the marls are green in color and are consists primarily of a loamy sand and is largely white quartz grains remarkably free from impuri of Pleistocene gravelly loam. In color the clay is commonly known as "greensand marls." They are adapted to the production of corn as well as of ties and varying in size from fine to coarse, while black to greenish black, the green color being due rich in calcium carbonate, derived from the shells clover. the grains themselves are angular. The sands that to the presence of considerable glauconite, which is which are abundant in the deposits, and chemical The other soil types referred to are developed are profitable occur in pockets or lenses which may in small pockets or evenly distributed throughout analyses usually show the presence of small amounts only in very small areas in that portion of the have a thickness of only a few feet and a horizon the clay. Mica flakes of small size are also numer of mineral phosphate. The marls thus contain Salern region which falls within the Philadelphia tal extent of a few rods or in lenses 15 to 20 feet ous. The clay is easily obtained, as the thin bed three important plant foods potash, lime, and district, and as the remainder of this district main and an areal extent of several acres. The even- of overlying Pleistocene is mixed with the Matawan phosphates. Altogether these constitute only a tains much the same soil conditions as far as the grained character of these sands has led to their ex clay without any injurious effects. The presence small percentage of the entire content of the depos eastern border, these less important soil types will tensive adoption as filter materials. They have of coarse sand beneath the clay is also of consider its, yet whenever the marls can be obtained at low not be described in detail. Enough has been said also been employed in the manufacture of fire brick able importance, as it facilitates easy drainage of cost they furnish economical means for increasing to show that the Coastal Plain portion of the because of their infusibility, caused by the absence the pit. All that is necessary to rid the pit of soil fertility. Where the glauconite marls have Philadelphia district possesses a considerable vari of fluxible substances, while some of the sands have water is to dig a few small holes into the Magothy been used it is claimed that their beneficial effect is ety of soil conditions in which important truck-soil sufficient bonding power to render them valuable sand; into these the water drains and finds its way much much more lasting than that obtained by areas predominate, although fruit, corn, and wheat for molding purposes. to the river by underground channels. The clay means of artificial fertilizers. lands also occur. The soils are generally well The Kirkwood sand is much finer than the fuses rather easily and makes a good building brick. The marls of the Rancocas group have been drained, except along the main stream courses, and Magothy or the Cohansey sands, and considerable Similar clay is worked for the manufacture of extensively worked for many years in the vicinity important crops are raised throughout the region. quantities have been shipped from pits to the north brick a short distance east of Maple Shade, just of Sewell, where a large plant is at the present WATER RESOURCES. of Mechanicsville as molding materials. The sands beyond the border of the Philadelphia district. It time in full operation. The material is dried and By F. BASCOM. in this small outlier evidently occupy a deep depres also outcrops in a railroad cut near Merchantville, shipped to fertilizer works, as the base for commer SURFACE WATER. sion in the underlying Cretaceous beds, so that though it has not been worked there. cial fertilizers. Considerable marl of the same the amount of material at this point is quite out Woodbury clay. Within the boundaries of the horizon has also been dug a short distance north of , PIEDMOKT PLATEAU. of proportion to its areal extent. Philadelphia district the Woodbury clay is worked Kirkwood for the same purpose. At present no The tributaries of the Delaware which traverse The Cohansey sand is not being commercially at only one place, about a mile south of Collins- marl is used in the natural condition, largely the Piedmont Plateau of the Philadelphia district employed at present within the limits of the Phila wood, where it is dug for the -manufacture of brick. because its value as a fertilizer has been underesti are Penny pack and Tacony creeks, Schuylkill delphia district, but i$ extensively dug as glass sand In this pit the clay is from 12 to 15 feet in thick mated, but also because of the scarcity of labor. River, and Cobbs, Darby, Crum, Ridley, and beyond the district toward the southeast. ness and is easily obtained. When fresh the clay Chester creeks. SOIL. Sands are also found at other horizons, particu is black, but on weathering it changes in color to Pennypaclc and Tacony creeks. These creeks larly at the base of the Patapsco formation in the light chocolate-brown. It contains some small flakes The soils of the Coastal Plain are for the most have drainage basins of approximately 63 and '45 vicinity of Conshohocken, this material being em of mica and is somewhat sandy in certain places. part directly derived from the Quaternary forma square miles respectively. They drain a cultivated ployed for architectural purposes and for electric The clay is considerably jointed. The bricks made tions, since most of the underlying Cretaceous and and populated district, in which woodland has been cars and locomotives. Sand for local uses has been from this clay burn to a good red color, are dense, Tertiary deposits are buried beneath a cover of sacrificed to culture and is found now only on the taken from the Pleistocene deposits in many places. and possess high tensile strength, as shown by tests later origin. The underlying sands, clays, and steep hillsides and bottom lands bordering the made by the New Jersey Geological Survey. marls, have, however, exerted an important influ creeks. There are no natural storage basins along CLAY. Englishtown clay. A thin layer of clay in the ence on the Quaternary materials of the several their courses and the tributaries are fed by surface A great variety of clay occurs among the Coastal Englishtown sand has been worked about three- areas, these later formations having been often springs and rainfall; under these surface conditions Plain deposits, the most important formations that fourths of a mile south of Woodbury for the largely derived from the immediately underlying rainfall is not detained by ground storage. The furnish it belonging to the Potomac, Matawan, and manufacture of brick. The clay is rather sandy beds. In certain localities, for example, they con run-off is proportionately great and carries with it Quaternary formations. and is mixed with surface loam. It makes a grade sist largely of reworked marls which partake of the large quantities of surface soil to the tributaries. of brick that is suitable for foundation purposes. character of the marl bed below. -The main streams become torrential and turbid and POTOMAC CLAYS. The deposits are shallow and not continuous, so The overlying Quaternary is in places spread in transport a heavy load of fine sediment. The same The clays of the Potomac group are contained in that the clay is of no especial significance. so thin a mantle that the basal formations con conditions which diminish ground storage increase the Patapsco and Raritan formations, the only two stitute the subsoil, and along the slopes may even evaporation during the summer months, hence formations of the group represented in the Phila QUATERNARY CLAYS. be the source of the soil itself. In a few restricted there is a marked seasonal fluctuation in the stream delphia district. Clays of Quaternary age have been extensively areas the cover of Quaternary is entirely lacking. flow. The exposed soil is parched and cracked in Patapsco clay. The Patapsco clay is of high worked on both sides of Delaware River in the The United States Department of Agriculture, summer by evaporation. The level of ground grade and is worked at various points in the Con- Philadelphia district. On the Pennsylvania side in its report on the Salem area in "Field Opera water falls below the surface springs and upper Philadelphia. 22 courses of the tributaries; the springs, therefore, dry occurs in March, April, or May, at the close of the Deep wells in the Wissahickon gneiss. pumping 60 gallons per minute. At Newtown up and the streams are reduced. Thus January, storage period, when evaporation and plant absorp Square a well in the Baltimore gneiss 300 feet deep Water supply February, March, and sometimes April are months tion are at a minimum and ground and surficial Depth Diameter (gallons and 8 inches in diameter yields 60 gallons of water Location. (feet). (inches) . per usually of large stream flow, while August, Septem storage at a maximum. minute). per minute. ber, and October are usually months of least stream From Ridley Creek 1,500,000 gallons every There are between 40 and 50 artesian wells in Barrett Ice Plant, Bryn Mawr, flow. The water power of these streams is only twenty-four hours are taken by the water depart 600 feet west of Bryn Mawr and near Philadelphia which have passed through partly utilized. They are not a source of water ment of the borough of Media. From Crum avenue, on the county line J752 10 the Raritan formation and which gain their water road; 2 wells }475 Creek 2,000,000 gallons are taken by the Spring supply from the pre-Paleozoic crystalline rocks. supply, with the exception of Sandy Run, a tribu Bryn Mawr Hospital 135 «5 tary to the Pennypack. field Water Company and distributed to the subur Bryn Mawr Hotel 350 10 50 Data concerning these wells are given below. Schuylkill River. The Schuylkill, with its chief ban towns. It has been asserted that a draft of Springfield Water Company In the Chickies quartzite wells have been suc station at Bryn Mawr; 2 tributaries, the Wissahickon, the Perkiomen, and 1,000,000 gallons per day per square mile of wells ______560 6 83* cessfully bored as follows: watershed could be made upon the tributaries of the Pickering, is an important source both of water Overbrook, 2 wells (F. P. (150 500 Wells in Chickies quartzite. power and of water supply. Observations of the the Delaware. Hayes)______]240 6 10 dally stream flow of the Schuylkill made by the The average rainfall, 1884 to 1897, at 22 Jenkintown _ ' 349 6 75 Water supply Locality. Depth (gallons per J324 75 (feet). minute). Philadelphia Bureau of Water show that the months stations where observations were made by the Jenkintown station. _ J150 of maximum stream flow are December to April, Philadelphia water bureau was about 48.5 inches. Wyncote : b Near Fort Washington _ 64 10 and that the months of minimum stream flow are Of this average rainfall nearly 50 per cent, or 24.1 A 154 97 (J. Conrad) June to September. The maximum daily average inches, was found in the stream flow. B 205 60 Tysori's, Edge HilL______150 stream flow in 1902 occurred during March and Delaware River. As a source of water supply C 212 76 Waverly Heights, Edge HilL______J570 No water. D 188 70 (Winthrop Smith) (500 and water power the Delaware is extremely impor was 5,840,530,000 gallons.0 The minimum stream E 147 78 Near Williams station. 132 5 flow was in June and .was 594,430,000 gallons. tant. It has been utilized for this purpose to a F 235 30 Willow Grove 780 100 Norristown and Philadelphia take their water large degree, but the increasing impurity of its &___.______175 50 supply chiefly from the Schuylkill. From Norris water, like that of the water of the Schuylkill, H 200 C 28 In the Shenandoah limestone there are wells as town to Philadelphia all the sewage and industrial necessitates an elaborate system of filtration, such Cheltenham Academy 352 12 follows: refuse of the towns along the Schuylkill drains into as is now being established at Torresdale by the Chelten Hill station _ 118 3 ( 125 1 Wells in Shenandoah limestone. that river and render the unfiltered water entirely city of Philadelphia. With adequate filtration the )340 8 208 unfit for domestic purposes. This has made neces Delaware can supply the increasing population on Noble station __ 163 1 16 Water supply Locality. Depth (gallons per sary an efficient system of filtration such as is now its banks with abundant water. It now supplies (feet). minute) . operated at Roxboro and JBelmont. in New Jersey 142,636 inhabitants with 17,010,464 a Without head. & Eight wells less than 100 feet apart. These wells furnish water to those Near Flourtown (Kunkle's farm)____ 60 83£ Perkiomen Creek. The Perkiomen drains a gallons of water daily. The estimated supply for parts of Jenkintown not supplied by the North Springfield Water Company. o The best flow is at a depth of 100 feet. The flow increases with use. 98 10 region of which 20 per cent is woodland, 77.5 per Trenton without storage is 601,600,000 gallons. (H. F. Hallman) The analysis of the water of Delaware River at 90 cent cultivated land, 0.5 per cent flats, and 2 per Successful artesian wells have been bored in the (William Thomas) cent roads. Like the other streams of the district, Trenton shows that above the city the river is pre-Paleozoic and Paleozoic formations. The more Near Williams station __ 43 «900 the Perkiomen shows a maximum stream flow in polluted with sewage and industrial refuse to a important wells are as follows: In the pre-Cam (Thomas Phipps) Near Plymouth station _ _ _ _ _ 90 40 January, February, and March, and a minimum dangerous degree. brian Baltimore gneiss and gabbro complex there (Hovenden) stream flow in August, September and October. The water power of the Delaware has been is a well at Wayne 150 feet deep, yielding about The maximum observed flow for one. day in Feb largely left unutilized, probably because of the 200 gallons per minute; at Radnor station there is a- Highly magnesian. ruary, 1902, in round numbers was 27,300,000 difficulty of building dams and the comparative a well on the property of the Pennsylvania Railroad On the southern slope of the South Valley Hills gallons per day per square mile of area drained cheapness of fuel. The number of mills on the Company which furnishes water for locomotives. numerous wells have been bored for private indi above the gaging station, an area of 152 square miles. Delaware above Trenton is only 186, with a net The well is 12 inches in diameter and 1000 feet viduals. Those wells of which record has been The minimum observed flow for one day was in horsepower of 6658. The New Jersey Survey deep, but it is worked only to a depth of 120 feet, obtained have penetrated the Octoraro schist of September, 1885, and was only 21,700 gallons per estimates that 50.7 horsepower per foot at Trenton yielding at this depth by the pneumatic system of these hills. They vary in depth from 60 to 80 is unused. day per square mile. The average daily flow of Deep wells reaching the pre-Paleozoic crystalline rocks. the Perkiomen is found to be 177,900,000 gallons Ponds. The Philadelphia district, lying south Water per day above the gaging station. of the limit of glacial deposits, is quite without supply Depth Location. Depth Diameter (gallons to natural ponds. The ponds that exist are insignifi (feet). (inches) . per rock Comparison of run-off, in inches, of Perkiomen Creek and minute). (feet). Schuylkill River from January to December. cant and occupy artificial basins. The streams thus lack storage basins. Navy-yard, League Island ______- - 906 "260 Year. Perkiomen Creek. Schuylkill River. Do ----- 600 6 270 COASTAL PLAIN. Near Grays Ferry _ _ _ 232 137 1898______- 21.50 24.39 The streams of the Coastal Plain of the Phila 456 208 1899 24.66 22.29 Delair 188 168 delphia district are without exception tributary to 1900______- 15.21 18.23 126 115 1901 17.55 17.80 the Delaware. They are tidal for half or more Caniden, near Front and Elni street _ _ H5i 95 1902______29.01 29. 02 than half their lengths, and flow for a considerable 300 8 120 fraction of their courses upon marls. These Schemm's brewery, Twentieth and Poplar streets _ _ 252 8 C 60 Pickering Creek. This stream appears on the features greatly impair the availability of the 495 6 60 <*50 western edge of the Norristown quadrangle, but streams for water supply or water power. The 2,031 8 Brewery, 1708 North Twelfth street. ______.______-_____--__ 350 8 100 most of its drainage area lies outside the Philadel water supply of the district, therefore, is not taken Seventh and Callowhill streets 452 8 150 phia district. It has a drainage basin of 65.88 from the streams, except in the cases of Haddon- Brewery, 1729 Mervine street _ _ 340 8 75 square miles. This basin lies, for the most part, field and Woodbury, where headwaters unaffected Prospect brewery, Eleventh and Oxford streets 350 8 °75 on pre-Cambrian gneiss, but the last 3 miles of by marls are available. The area of the drainage 1,000 10 100 the creek's course are on the Triassic formations. basins of the chief streams and their daily average Ice works, 23 North Eleventh street 250 8 300 Its minimum annual flow has been estimated at flow are given in the following table: Wall-paper factory, 2228 North Tenth street ______-- _ __ _ 210 8 100 Fifteenth and Market streets __._.. 500 8 100 4,000,000 gallons, and its maximum flow at Area of drainage basins and daily average flow of 272 6 30 4,000,000,000 gallons. chief streams. Carpet works, Eleventh and Cambria streets 200 6 50 Cobbs, Darby, Crum, Ridley, and Chester 335 6 250 Average daily creeks. These creeks flow in roughly parallel Drainage Average daily flow of driest Continental Hotel. Ninth and Chestnut streets - - 240 8 40 Creek. basin. flow at mouth. month at "40 courses and possess drainage basins of approxi mouth. Hotel, Eleventh and Pine streets _ 576 5 mately the same area. For Crum and Ridley Hotel, 108 South Broad street _ _ _ _ 484 8 60 Sq. miles. Gallons. Gallons. 525 8 70 creeks the stream flow has been recorded; the Pensauken 35.4 39, 900, 000 5, 900, 000 , Turkish bath, 1104 Walnut street ______265 8 110 Coopers 40.5 40, 000, 000 6, 800, 900 amount can not be very different for Darby and 100 6 200 Big Timber_ 59.3 55, 400, 000 9, 980, 000 Chester creeks. Morocco works, Frankford and Junction streets. __ 500 6 500 Woodburya Crum Creek has a drainage area of 29.47 square Do _ _ 322 6 500 Mantua, above Hurff- miles, of which about 40 per cent is wooded. Its ville______51.2 2, 180, 000 Do 252 6 500 364 °60 minimum average monthly flow from 1892 to 1901 44.4 8 Angora Cotton factory ______252 8 60 was 5,220,000 gallons in twenty-four hours (Sep Oldmans _ 44.4 1,680,000 30 5 100 tember, 1901); its maximum flow was 138,000,000 "Tidal for more than half its length of 7 miles. G. Taylor, southeastern part of city _ 670 12 250 gallons in twenty-four hours (May, 1894). bTidal for more than half its length. 140 Ridley Creek possesses a drainage basin of 33.6 Laurel and Beech streets _ _ _ .. 308 UNDERGROUND WATER. square miles. Its minimum computed flow between 2,000 1892 and 1901 was 5,940,000 gallons in twenty- PIEDMONT PLATEAU. 525 8 20 125 60 Erosion of the heterogeneous, dipping strata of four hours (September, 1895). Its maximum Franklinville dye works, 3961 North Fifth street _ 314 6 40 observed flow was 157,500,000 gallons in twenty- the Piedmont Plateau produces favorable conditions 400 8 100 125 four hours (May, 1894). Its minimum flow occurs for the emergence of underground water in the form Bedford Company, Frankford ______1,021 8 60 20 in August, September, and October, at the close of of springs. Between the Newark group and the 114 40 15 the growing period and the opening of the replen Paleozoic rocks, brought to the surface by folding 64 8 60 25 ishing period. At this time stream flow has not and erosion, springs emerge on all the hillsides. Mitchell & Pearson, Schuylkill avenue and Reed street _ _ 320 8 150 18 Millbourne Milfs Co., Sixty-third and Market streets. _ _ _ _ 600 50 20 begun to show the effects of the season of replenish The small creeks are fed by springs and every John Wyeth & Bro., Eleventh street and Washington avenue _ - _ 93 8 30 90 ing, and the ground water, at the close of a period of farmhouse is supplied with spring water. A Quaker City Chocolate Co., 2140 Germantown avenue. _ __ 480 8 40 60 maximum vegetable growth and maximum evapo remarkably copious spring in the Paleozoic belt 8 ^240 ration, is at its lowest level. The maximum flow issues from the base of the limestone at Spring a Water at 536 feet. *> "Water at 572 feet. c Flowing wells. "1,000,000 gallons a day=1.55 second-feet. Mill. d Water not good in boilers. e Lime and iron water. 23 feet and supply abundant water. In the shallow this horizon south and east of Camden, and they and Torresdale, with the exception of Tacony and Chester. The water supply for the city of Ches wells the water is soft. From the deeper wells it is vary in depth from 46 feet in Cinnaminson to 117 Holmesburg. Overbrook and West Philadelphia ter is taken from Delaware Eiver. It is pumped a reported to be hard. The thickness of the mica feet in Woodbury. The following are localities are to be supplied from the Belmont plant. The distance of 4 miles from Chester, where it is depos schist is not great on the slope of the hill and prob where water from this horizon has been obtained: Eoxboro district, comprising Eoxboro, Manayunk, ited in two 8,000,000-gallon reservoirs. After it ably the hard water has its source in a limestone Cinnaminson, Collingwood, Gloucester, Westville, Chestnut Hill, Mount Airy, and Germantown (in has passed through a process of sedimentation it is horizon. Woodbury, Wenonah, Sewell, Maple Shade, Thoro- part), are now supplied from the Eoxboro filter put through mechanical filters and thence goes to a The gently northwestward-dipping sandstones fare, Mount Ephraim, Washington Park, Clarks- plant, which is completed and in operation. clear-water basin. interbedded in shales belonging to the Newark boro, Mickleton, and Swedesboro. The combined capacity of the filters is about Media. The water department of the borough group, which occupy the northern third of the (5) In the Matawari above the basal beds are 320,000,000 gallons, or 30,000,000 gallons more of Media obtains its water supply from Eidley Philadelphia district, afford favorable conditions for sandy beds from which many wells derive their than the capacity of the Croton Aqueduct. At Creek. The water is pumped through sand filters bored wells, and the water supply of that area is water supply, although it is generally not very present New York uses 120 gallons per capita daily, to a reservoir and standpipe. largely furnished by such wells. The following abundant. Their depth at Maple Shade is from whereas Philadelphia uses 229 gallons. Norristown. The city of Norristown is supplied are the deep wells of which reports could be 63 to 97 feet, increasing to the south. Wells in Springfield water companies. The Springfield with water by the Norristown Water Company, obtained: these beds are located at Newbold, South West- Water Company and the North Springfield Water which obtains its water supply from the Schuylkill. wells in the rocks of the Newark group. Company, under the control of the American Pipe The water pipes are laid under the river and draw Manufacturing Company, supply with water most their supply from the channel to the southwest of Depth in feet Depth below surface Water supply of the suburban districts of Philadelphia. All the island opposite Norristown. Thus is avoided Locality. (feet). to which Geologic horizon. (gallons per water rises. hour). towns situated on the north bank of the Delaware contamination from Stony Creek, which carries the between Cobbs and Crum creeks, and Eddystone, drainage of the State Insane Asylum. Norristown, Sandy Hill ' _ _ _ 169 74 Sandstone bed in Stockton f ormation_ 900 Norristown, near Stony Creek. _ _ _ _ 102 do 1,008 west of Crum Creek, are supplied by the Spring The water is first pumped into a small sedimen Norristown _ _ 100 16 do 3,000 field Water Company. The towns along the Penn tation basin, where it is coagulated by means of Between Norristown and Jefferson ville (West End 75 do 1, 500 sylvania Eailroad main line as far as Glenlock, 25.3 sulphate of alumina. It then filters by gravity Land Co.). miles from Philadelphia, are supplied by the through a 5,000,000-gallon filter plant and passes Jeffersonville (F. A. Potts) ______._____. 92| Two sandstone horizons in Stockton (est.) 1,200 formation : 35-40, 86-92-J. Springfield and North Springfield water companies, into a clear-water basin, from which it is pumped 70 45 Sandstone bed in Stockton formation. 600 also the towns east of the main line, Conshohocken, to the distributing reservoir located on the hill to Bridgeport (Chas. Meyers) 65 do ___ -_ . 600 do ^ Chestnut Hill (in part), Oreland, Glenside, Jenkin- the north of Norristown. This reservoir has a Sandy Hill schoolhouse, Whiteplain Township _ _ 60 28 120 town (in part), Oak Lane, and the intervening capacity of 11,000,000 gallons. 35 11 do - _ 1,500 Washington Square schoolhouse - - _ 3Si 14 do 600 towns. Chester, Media, Norristown, Lansdale, Lansdale. The water supply of Lansdale is fur Belfrey station, Stony Creek R. R. a _ __ 37 15 ___ __do 30 Tacony, and Holmesburg are the only considerable nished by the Lansdale Water Company, which Ambler(8)_.______.______- 275 Cambro-Ordovician limestone 2,100 towns in the Philadelphia district not supplied by owns two artesian wells and a standpipe with a Shady Grove schoolhouse - _ - - 45 19 Probably sandstone of Lockatong 900 the Philadelphia Bureau of Water or the Spring capacity of 38,000 gallons. formation. Morris road and Skippack pike, North Wales & __ _ Sandstone of Lockatong formation _ field water companies. Ambler. The Ambler Spring Water Company, 159 Sandstone horizons of Brunswick The Springfield Water Company takes its water which supplies Ambler, obtains very pure water formation, from Crum Creek at a point 1^ miles northeast of from a large number of springs issuing from a Do _- -- -- 376 do _ - _-. __ Media, in the township of Springfield. The water sandstone bed of the Stockton formation. These Do _ _ - - 611 140 do 65 15 _____do is first coagulated with sulphate of alumina and springs furnish about 2,000,000 gallons daily. In passed into a 10,000,000-gallon sedimentation addition, a large spring in a quarry in the Stockton a Abandoned. & Water very hard. basin. Thence it passes into a suction well, from formation is used, which yields about 15,000 gal COASTAL PLAIN. ville, Woodbury, Wenonah, Sewell, Maple Shade, which it is pumped through six pressure filters of lons per hour. The chief water-bearing formations of the Coastal Merchantville, Kirkwood, Laurel Springs, Black- 500,000 gallons capacity each, which are thoroughly WATEE, SUPPLY TO CAMDEN AND SUBURBAN TOWNS. Plain are Cretaceous. The earlier discussions of wood, Thorofare, Clarksboro, and Mickleton. washed and rinsed daily. the geology of the Cretaceous have shown that (6) The Mount Laurel sand at the base of the The North Springfield Water Company takes its Camden. For many years (since about 1853) conditions are favorable for artesian wells in these Monmouth group affords a water supply. Many water from Pickering Creek near its mouth. Here the city of Camden had taken its water supply from rocks. Permeable sandy or gravelly beds are of the best wells in southern New Jersey, outside are located a pumping station, a sedimentation Delaware Eiver southeast of Petty Island. The interstratified with impermeable clay beds. At of the Philadelphia district, obtain their supply basin, and filters. There are three filters one pumping station was located at Pavonia, northeast the outcrops of the more porous beds water is from this horizon. There are such wells at Laurel slow sand filter covering one-half acre, with a of the mouth of Cooper Creek. Because of the absorbed and, there being no outlet to the east, Springs, Black wood, and Sewell, which vary in capacity of 1,500,000 gallons, and two gravity increasing impurity .of the water the supply became these beds become saturated by water which is depth from 70 to 100 feet. mechanical filters with a combined capacity of very unsatisfactory, and in 1897 and 1898 there under considerable pressure. When wells pene (7) The Vincentown sand, which constitutes the 2,500,000 gallons. The water is first pumped to a were sunk near Morris station more than a hundred trate such beds the water rises, and if the mouth of upper portion of the Eancocas group, is a highly 10,000,000-gallon sedimentation reservoir located artesian wells. These wells gain their water from the well is lower than the outcrop where the water calcareous green sand composed chiefly of bryozoan close to the pumping- station, but on the opposite two horizons within the Earitan. The deeper wells enters, the well overflows. The principal water earth, and constitutes a water-bearing horizon. side of Pickering Creek. From the sedimentation probably reach the base of the Earitan. All the horizons within the Coastal Plain of the Phila Wells at Laurel Springs gain their supply from basin the water gravitates through a filter plant to wells are furnished with bottom strainers and sup delphia district are as follows: this horizon at a depth of 45 to 50 feet. a 1,500,000-gallon clear-water basin, and thence ply an abundance of pure water. A pumping (1) The pre-Paleozoic crystalline formations (8) The basal member of the Miocene is a the water is pumped to the distributing reservoirs station has been established at this point and more which underlie the Cretaceous, Tertiary, and water-bearing formation. No wells have been by means of the two high-duty fly-wheel pumping than 20,000,000 gallons of water can be obtained Quaternary deposits. This floor is reached by reported to tap this formation in the Philadelphia engines. every twenty-four hours. wells in the Delaware Valley at a depth of 95 to district, though it is an exceedingly important There are under the control of the North Spring Riverton and Palmyra. The Eiverton and Pal 270 feet, and at varying depths below its upper source of water supply in southeastern New Jersey. field Water Company three artesian wells, which myra Water Company, which supplies these two surface yields a large supply of excellent water. act as a reserve supply one at Bryn Mawr, 560 towns, obtains its water from a dug well, 15 feet deep, WATEK SUPPLY TO PHILADELPHIA AND SUBURBAN Such wells have been sunk in Camden, Phila feet deep, good for 120,000 gallons in twenty-four near Delaware Eiver. The well is sunk in gravel TOWNS. delphia, Delair, at Cramer Hill Ferry, near Grays hours, and two at Oak Lane, 340 feet deep, good and intercepts the water on its way to the river. Ferry, and on League Island. A list of these Philadelphia Bureau of Water.. Philadelphia, for 300,000 gallons in twenty-four hours. The From 300,000 to 500,000 gallons of water per day wells is given above. Falls of Schuylkill, Manayunk, Eoxboro, Chest hardness of the water of the Bryn Mawr well is 5.5 are pumped from this well, and it is estimated to (2) The basal Earitan beds. These are heavy nut Hill (in part), Mount Airy, Germantown, degrees in 100,000, and that of the Oak Lane wells have a capacity of 1,000,000 gallons per day. yellowish-white gravel and cobble strata near the Frankford, Bridesburg, Wissinoming, and the 5.29. Gloucester. This town obtains its water from base of the Earitan or plastic clays. They are intervening areas are supplied with water through Analysis of the filtered water of Pickering Creek open wells which supply 1,000,000 gallons of water reached by wells in Camden (Esterbrook Pen the Bureau of Water of Philadelphia. gives the following results: per day. Company, American Nickel Works, power house The water is pumped from the Schuylkill at five Analysis of filtered water of Pickeriug Creek. Newbold and Westville, These towns are sup Parts per plied by the Westville-Newbold Water Company, of Camden Eailroad Company, city hall, United stations (1) Eoxboro or Shawmont, (2) Queen million. States Chemical Works, county prison, Eeeves Lane, (3) Belmont, (4) Spring Garden, (5) Fair- Free ammonia___..______1______'______0.08 which obtains water from three artesian wells 160 Oilcloth Works, foot of Penn street, Cooper mount. Water is also pumped from the Delaware Nitrogen as nitrates______.______1.33 feet deep. Chlorine______._ _ __ _-_ _ 5.0 Hospital well, pumping station wells), Philadelphia at the Frankford station, one-half mile northeast of Alkalinity, in terms of carbonate of iime______37.0 Woodbury. This town is supplied from the (Little Dock street and Moore street wharf), Glou the mouth of Wissinoming Creek. From these sta Hardness, in terms of carbonate of lime______42. 0 headwaters of Mantua Creek. The water is used cester, National Park below Eedbank, Washington tions it is pumped to reservoirs at Eoxboro, Queen Number of bacteria exceedingly low. without filtration. The larger portion of Mantua Park, Stockton, Pavonia, Delair, Eiverton, and Lane, Fairmount Park, and Frankford, whence Analyses of Crum Creek water taken from the Creek lies upon the marls and is therefore unfit for Maple Shade. The supply of water from this hori it has been distributed without filtration. The spigots are even more favorable, showing the water a water supply. zon is fair. The depth of the wells varies from 70 increasing impurity of the Schuylkill and Delaware to be excellent in quality for domestic and manu Redbank and Paulsboro. Eedbank is supplied feet in Camden to 375 feet in Maple Shade. waters, contaminated by the sewage of the numerous facturing uses. from both open and tube wells. Paulsboro obtains (3) Beds in the Earitan above the basal beds. manufacturing towns along their courses, has ren Tacony, Holmesburg, and Torresdale. These its water supply from wells 65 feet deep, from Interstratified with the clays and fine sands of the dered them utterly unfit for household use without towns, in the thirty-fifth and forty-first wards of which 350 gallons per minute are pumped. No Earitan occur local beds of coarse sand or gravel. being filtered. the city of Philadelphia, are supplied with water filter plant is required. The water is clear, color These beds are water bearing. Water has been A new and comprehensive system of plain sand by the Disston Water Company, which leases and less, and odorless, and analysis shows it to be obtained in them at Camden, Gloucester, Pauls- filters is now being introduced. There are three operates the plant of the Holmesburg Water Com remarkably pure. boro, Pavonia, Stockton, Collingswood, Delair, plants, located at Eoxboro, Bala (Belmont and pany, in Holmesburg at the mouth of Sandy Eun. Haddonfield. The water supply of Haddonfield Palmyra, Morris, Eiverton, Pedricktown, Billings- City < Line avenues), and Torresdale. At Torres- This little stream rises near Fox Chase and pursues is taken from a tributary to North Branch of port, Magnolia, Westville, and Maple Shade. The dale water is taken from the Delaware, and after a winding course over a rock and gravel bottom to Coopers Creek. This stream is fed by springs and depth' at which water is reached varies from 67 being passed through sand filters is carried in a Pennypack Creek, into which it empties at a point furnishes about 5,000,000 gallons per day. It is feet in Camden to 260 feet in Maple Shade. The rock tunnel to Eobbins street, Tacony, whence it is about 21 miles above the Delaware. It is fed by collected in a reservoir which is protected from supply is excellent. to be distributed to the Philadelphia district, which springs all along its course. A mechanical system surface water. There is no filtration plant. (4) At the top of the Earitan there are bluish- includes the Queen Lane district (the Falls of of filtration, installed by the New York Continental Wenonah and Merchantville. These towns are white gravel beds which furnish an abundant Schuylkill and Germantown, in part), East Phila Jewell Filtration Company, with a capacity of supplied from springs. supply of fine water. Wells- have been sunk to delphia, and the towns lying between Philadelphia 2,000,000 gallons per day, is in use. March, 1908. Philadelphia.