DESCRIPTION OF THE PATUXENT QUADRANGLE

Prepared under the supervision of William Bullock Clark, geologist in charge.

By George Burbank Shattuck, Benjamin L,eKoy Miller, and Arthur Bibnins.

INTRODUCTION. Belief. Throughout the entire extent of the Piedmont and mud, derived from the waste of older rocks, together In addition to the force which acted in a horizontal Plateau the uplands are smooth and rounded, usually to with the remains of plants and animals that lived while direction, this region has been affected by other forces Location and area of the quadrangle. The a very marked degree. They represent the ancient the strata were being laid down. which acted vertically, and repeatedly raised or depressed Patuxeht quadrangle lies between parallels 38° 30' plain to which the land was worn down during the long- the surface. The compressive forces were tremendous, and 39° north latitude and meridians 76° 30' and 77° ages of decay. The streams near their heads flow Structure. The structures that prevail through most but limited in effect to a relatively narrow zone. Less intense at any point, but broader in their results, the west longitude. It includes one-fourth of a square between low divides in the open, shalloAV valleys of the of the ancient rocks of the Plateau are very complex, ancient plain. In their lower courses, however, they but they present much the same types, even in widely vertical movements extended throughout this and other degree of the earth's surface and contains 931.5 have worn channels deep into the old valley floors and separated districts. In complexity they are strongly con­ provinces. It is likely that these two kinds of move­ square miles. From north to south it measures now flow through narrow gorges and canyons. These trasted with the Juratrias rocks which occupy a small ment were combined during the same epoch of deforma­ 34.5 miles and from east to west the mean distance canyons widen out on the softer rocks and toward the part of the Plateau. These strata are gently tilted and tion. In most cases the movements have resulted in a is 27 miles, the width being 27.1 miles along the east, and their steep walls give place to terraces and to all dip toward the west at angles of from 1° to 30°. The warping of the surface as well as in uplift. One result southern and 26.9 miles along the northern border. lower and smaller plateaus. In a view across the Pied­ crystalline rocks covering most of the Plateau are tilted of this appears in overlaps and unconformities in sedi­ The quadrangle includes parts Of the State mont Plateau from one of its summits the monotonous at high angles, broken by faults, and altered from their mentary formations. level of the uplands is here and there broken by small original condition. Folds are frequent, and the forces Outline of the geography and geology of the of Maryland and of the District of Columbia. ridges and peaks which rise a few hundred feet above of compression have usually so acted as to squeeze the Atlantic Coastal Plain province. In its physio­ In Maryland it embraces the southern portion of the Plateau. These are areas not worn down to the sides of the folds together until the beds dip in the same Anne Arundel County, the northern portion of levrel of the plain and are most common near the union direction. In these cases the existence of the fold is graphic and geologic relations, all of this quadran­ Gal vert' County, the extreme northern end of St. of the Piedmont Plateau and the Appalachian Mountains. detected mainly by the order in which the formations gle except a small area in its northwest corner Marys County, the northeastern portion of Charles The uniform heights of the Piedmont Plateau distin­ occur. Portions of the Plateau in North Carolina and forms a part of the Atlantic Coastal Plain prov­ County, the southeastern portion of Prince Georges guish it from the marked relief of the ridges and valleys South Carolina, however, contain folds of such moderate ince, which borders the entire eastern part of in the Appalachian Mountains. The Plateau as a whole deformation that they are defined by the angle of the dip North America and which in essential particulars County, and about 1 square mile of the southeast­ has a gentle slope toward the east and southeast in that as well as by the sequence of the formations. is distinctly separated from the provinces on either ern part of Montgomery County. The District of portion which drains into the Atlantic, and toward the Faults are not uncommon in the Piedmont region, and Columbia is represented in the northwestern part of south where the streams drain into the Gulf of Mexico. doubtless many more might be traced if the rocks could side. Its eastern limits are marked by the well- the quadrangle by about 24 square miles. Besides In a wide belt adjoining the Coastal Plain the Plateau be divided into small and distinct formations. Two defined edge of the continental shelf, at the summit the land areas a small portion of Chesapeake Bay, summits vary from 300 to 600 feet above sea. This belt types of faults appear: those associated with the Jura­ of an escarpment varying in height from 5000 to with parts of the estuaries of South, West, Patux- comprises almost all of the Plateau north of James River, trias basins normal faults and those connected with 10,000 feet. This scarp edge lies at a general depth in Virginia. Over another wide belt adjoining the Appa­ the folding and metamorphism of the older rocks ent, and Anacostia rivers and Piscataway Creek are of 450 to 500 feet below sea level, but commonly lachian Mountains the Plateau summits are 1000 to 11.00 thrust faults, The former are simple breaks directly the 100-fathom line is regarded as the boundary of embraced within this quadrangle. It includes feet above the sea, while along the immediate western across the sedimentary layers, and their planes usually portions "of two physiographic provinces the borders of the Plateau the summits rise to 1500 feet. dip at high angles from 75° to 90° corresponding the continental shelf. The descent from that line Piedmont Plateau and the Atlantic Coastal Plain. The Plateau surface south of James Eiver and lying in closely to the dip of the schistose planes in the under­ to the greater ocean depths is abrupt; at Cape Outline of the geography and geology of the Pied­ the Atlantic drainage is about evenly divided between lying older rocks. The displacements due to these faults Hatteras there is an increase in depth of 9000 feet mont Plateau Province. This province is repre­ the lower and higher groups of altitudes. The zone of are comparatively slight, being measured by hundreds in 13 miles, a grade as steep as that found iii many descent from higher to lower is relatively narrow, and of feet, and they are noticeable only where the strata sented by small areas of granite gneiss along places along the flanks of the greater mountain in it the Plateau surface falls rather rapidly. This zone dip at small angles and are divided into readily recog­ systems. In striking contrast to this declivity is tributary streams of Anacostia River in the north­ passes from the Appalachian Mountains into the Plateau nized formations. Such faults, therefore, are hard to west corner of the quadrangle. The following a little north of James Eiver, and, as its trend is more trace beyond the Juratrias basin, although undoubtedly the comparatively flat ocean bed, which stretches general description is taken from the Washington nearly south than that of the Plateau, it slowly recedes they exist elsewhere as well. Thrust faults among the away to the east with but slight differences in ele­ folio (No. 70) of the Geologic Atlas of the United from the Mountains toward the Coastal Plain. highly tilted rocks are comparatively little known, and vation. Seen from its base the escarpment would States: Drainage. The system of drainage of the Piedmont their place seems to have been taken by the countless have along the horizon the appearance of a high Plateau is fairly simple. Most of the streams flow minor dislocations of the rock particles. A few have mountain range with a very even sky line. Here The Piedmont Plateau is an upland to which the term southeasterly into the Atlantic. Around the south­ been discovered under conditions especially well adapted and there notches, produced, perhaps, by streams "plateau" is applied because of its elevation and gen­ western end of the Appalachian Mountains, where the to show unusual structures. In these cases the faults eral flat aspect. It constitutes a division of the great Plateau swings toward the west, the streams flow south­ seem to have been produced either during or after the which once flowed across the continental shelf, Appalachian province, and its name. " Piedmont," erly into the Gulf of Mexico. There are two principal later stages of the folding and metamorphism, inasmuch would be seen, but there would be no peaks nor refers to its position at the foot of the Appalachian classes of streams Those which rise near the inland as they cross the formations and the schistose planes serrated ridges. Mountains. From the base of the Blue Ridge in border of the Plateau, and those which rise beyond rather abruptly. Unlike the usual Appalachian thrust The Piedmont Plateau, already described, forms Georgia, North. Carolina, and Virginia, and from it, in the Appalachian Valley. Savannah Eiver, in faults, these rarely have any visible origin in anticlines. the western boundary of the Atlantic Coastal Plain. Catoctin Mountain in Maryland and Pennsylvania, it Georgia, is typical of the first class, and James Eiver, Their planes dip at high angles, and for the most part Most of the larger streams and many of the smaller slopes as a whole southeastward. The summits stand in Virginia, of the second class. North of the Virginia- lie nearly parallel to the adjoining schistose planes. It at nearly the same height over extensive areas, with JSTorth Carolina boundary these two kinds of streams is where the two diverge that the faults become apparent. ones, as they cross the western margin of the gradual changes from district to district. Since its for­ drain nearly equal areas of the Piedmont Plateau, By far the most prominent of the Piedmont structures Coastal Plain, are characterized by falls or rapids, mation the original plain has been uplifted and streams while south of that boundary no large stream rises is schistosity. Formations which retain their original and the name "fall line" is given to this boundary have worn narrow channels down into the old surface. far from rhe border of the Plateau. Most of the larger condition unchanged are extremely rare, and frequently on that account. Below the fall line the streams The rugged slopes thus produced are closely confined to streams of both classes flow directly across the Plateau the alteration has quite obliterated the original charac­ show a marked decrease in the velocity of their the streams and are visible only on near approach. ter of the rock. In most of the sedimentary rocks the at wide angles with the trend of the rock formations. currents. In the middle Atlantic region tide-water Along the northwestern border of the Plateau there are In their general freedom from the control of the rocks, bedding planes have been destroyed by the metainorphlc remnants of the old plain not yet invaded. In passing the Piedmont streams are most unlike those of the Appa­ action, and even where they are distinct they are usually estuaries, the continuations of the large streams, northward through Virginia, one finds the Plateau and lachian Mountains arid Valley. The chief exceptions to less prominent than the schistosity. In the igneous extend inland to the fall line, which thus marks the Mountains gradually merging into each other, so this are in Georgia and Alabama, where the main rocks planes of fracture and motion were developed, the head of navigation. To the south the fall line that the separation of the Piedmont and Mountain streams follow the rock belts for long distances. The which, in a measure, made easier the deformation of the gradually * rises, so that in the Carolinas and Geor­ divisions becomes less prominent. Where the Potoniac small rivers and the tributary creeks show greater rocks. Along these planes of localized motion the orig­ gia, although falls and rapids still mark its location passes out into the Piedmont region the actual plateau inal texture of the rock was largely destroyed by the dependence upon the nature and structure of the and furnish power for mills and factories, the lower extends far into the Appalachian Valley. Many out­ underlying rocks, and occupy many valleys running fractures and the growth of the new minerals, and in liers of the Appalachian Mountains, such as the South northeast or southwest with the rock belts. These many cases this alteration extends through the entire courses of the stream are considerably above tide. Mountains in North Carolina and Southwest Mountain courses become general in some regions for instance, mass of the rock. The extreme development of this The position of the fall line near the head of navi­ in Virginia, interrupt the seaward slope of the Plateau. in central Virginia. Most of the Piedmont streams process is seen in the mica schists and mica gneisses, gation or near the source of water power has been The eastern border of the Piedmont Plateau is much branch uniformly at their heads and occupy basins the original textures of which have been entirely replaced one of the very important factors in determining less clearly defined than its western margin. The Pied­ which are about parallel. This is particularly the case by the schistose structure and parallel flakes of new min­ the location of many of the towns and cities of the mont slope gradually descends toward the east and erals. The planes of fracture and motion are inclined with the smaller rivers which head in the eastern part Atlantic coast, New York, Trenton, Philadelphia, merges into the Coastal Plain. The chief topographic of the Plateau, near the Coastal Plain. toward the southeast through most of the Plateau, difference between the two provinces lies in the contrast although in certain belts, chiefly along its eastern and Wilmington, Baltimore, Washington, Fredericks- presented by the narrow gorges cut in the Plateau and Rocks. The ancient rocks of the Plateau comprise central portions, there is a prevailingly northwest dip. burg, Richmond, Petersburg, Raleigh, Camden, the wide valleys of the Coastal Plain. The crystalline four series, of widely different age and character. The southeasterly dips range from 45° to 90° ; the north­ Columbia, Augusta, Macon, and Columbus being- rocks of the Plateau form a floor on which the sediments These are the igneous and crystalline rocks, includ­ westerly dips, from 30° to 90°. located along it. A line drawn through these places of the Coastal Plain were laid down. At first these ing gneiss, schist, granite, diorite, and similar forma­ The structures above described, except perhaps the would approximately separate the Coastal Plain lapped far over the Piedmont region, but they have tions; the volcanic formations, embracing rhyolite, Juratrias tilting and faulting, are chiefly the result of from the Piedmont Plateau. been removed more and more by erosion until only basalt, and their alteration products; the older sedi­ compression which acted most effectively in a northwest- small remnants are left upon the Plateau. As the mentary strata, including conglomerate, sandstone, southeast direction, at right angles to the general trend The Atlantic Coastal Plain province is divided by streams cut deeper and wider valleys in the loose sedi­ slate, limestone, and their metamorphosed equiva­ of the folds and of the schistose planes. The earliest- the present shore line into two parts a submerged ments than in the hard underlying rocks, a general lents; and the younger sediments, the conglomerates, known period of compression and deformation occurred portion, known as the continental shelf or conti­ difference in topography resulted. Later periods of sandstone, and shale of Juratrias age, with the eruptive during Archean time, and resulted in much of the meta­ nental platform, and a subaerial portion, commonly submergence, during which the Coastal Plain was rocks which accompany them. The relative areas of morphism of the present Carolina gneiss. It is possible called the Coastal Plain. In some places the divi­ beneath the sea, allowed the waters to extend far these groups nearly correspond with their ages, the area that other movements took place in Archean time, pro­ up the larger A^alleys, and in some cases the later of the oldest group being greatest and that of the Jura­ ducing a portion of the metamorphism which appears in sion line is marked by a sea cliff of moderate height, gravels reach across the Piedmont Plateau and into the trias least. the other Archean rocks. In the course of time, com­ but usually the two parts grade into each other Appalachian Mountains. The first three series have been greatly changed since pression became effective again, early in the Paleozoic with scarcely a perceptible change, and the only 1 This quadrangle has been surveyed in cooperation with their formation, both in composition and in attitude, era, and a series of movements took place culminating mark of separation is the shore line. The areas of the Maryland Geological Survey. A fuller discussion of the the alteration being so profound in some of the older soon after the close of the Carboniferous period. The the respective portions have changed frequently Maryland portion of the quadrangle will be found in the gneisses and schists as to destroy their original nature. latest of this series was probably the greatest, and to it during past geologic time owing to the shifting of county reports of the Maryland Survey, which are accompa­ As a result, a schistose character prevails in these areas. is chiefly due the well-known Appalachian folding and nied by geologic ihaps published on the United States Geo­ The Juratrias series shows little change save the hard­ metamorphism. The various deformations combined the shore line eastward or westward caused by local logical Survey topographic base, on the scale of 1: 62,500; also or general depressions or elevations of moderate in the volumes published by the Maryland Survey on the ening into compact stone and a moderate degree of tilt­ have greatly changed the aspects of the rocks so much Eocene (1901), the Miocene (1904), and the Pliocene and Pleis­ ing from its original attitude. The materials of which so, in fact, that the original nature of some of the oldest extent, and even at the present time such changes tocene (1906). the sediments are composed were originally gravel, sand, formations can be at present only surmised. are in progress. Deep channels that are probably old river valleys, the continuations of valleys of Chesapeake Bay and its estuaries to a height of 300 nants. In the western portion of the quadrangle tion is rendered uncertain. The surface of this existing streams, have been traced entirely across feet near the southeastern boundary of the District this plain is well developed in the lower valleys of plain ranges in elevation from about 200 feet in the continental shelf, at the margin of which they of Columbia. With the exception of a few local­ Piscataway and Henson creeks, and occurs in an ! the southern portion of the quadrangle to about have cut deep gorges. The channel opposite the ities, everywhere throughout the area stream ero­ unbroken flat extending up the valley of Anacostia I 300 feet in the hills southeast of Washington. mouth of Hudson River is particularly well sion has destroyed the originally plane surface of River as far as College Park. The Talbot plain I marked and has been shown to extend almost the country and has dissected it into a gently rolling has been dissected by stream action less than any \ DRAINAGE. uninterruptedly to the edge of the shelf, over 100 upland of low relief. The stream systems that have of the other plains described below. The drainage of the Patuxent quadrangle is miles southeast of its present mouth. A similar been most active in the work of erosion are those of Wicomico plain. The Wicomico plain lies at a j comparatively simple, as a result of the simple channel lies opposite the mouth of Chesapeake Bay. Patuxent River, which crosses trie middle of the higher level than the Talbot, from which it is in ! structure of the Coastal Plain formations and the The combined width of the submerged and subaerial quadrangle from north to south, and South and many places separated by an escarpment varying contiguity,of the region to Chesapeake Ba}^. The portions of the Coastal Plain province is nearly West rivers, in the northeast corner. In addi­ in height from a few feet to 10 or 12 feet. At greater part of the land of the area is naturally uniform along the entire eastern border of the con­ tion to these a few short streams flow directly into some places this, escarpment is absent, so that there drained. In some places this is effected principally tinent, being approximately 250 miles. In Georgia Chesapeake Bay along the eastern margin of the seems to be a gradual passage from the Talbot plain through underground drainage, as on the high the subaerial portion is over 150 miles wide, while quadrangle, and Anacostia River and Piscataway, to the Wicomico. It is present, however, at so many divide between Potomac and Patuxent rivers and the submerged portion is narrower and along the Mattawoman, and Zekiah creeks, tributary to Poto­ different places that there is little difficulty in deter­ on the low land lying south of West River, locally eastern shore of the peninsula of Florida is almost mac River, drain the western portion. The coast mining the line of separation between the two plains. known as "the swamp." The remainder of the absent. To the north the submerged portion grad­ line near the eastern margin of the quadrangle The base of the escarpment lies at an elevation of quadrangle is well drained by streams, inasmuch as ually increases in width and the subaerial portion exhibits two strongly contrasted types. In the about 40 feet. From that height the Wicomico the estuaries of Chesapeake Bay extend inland a becomes narrower. Except in the region of Cape northeast corner South and West rivers form two plain extends upward to an elevation of about 100 number of miles and the side tributaries cut back Hatteras, where the submerged belt becomes nar­ reentrants and dissect the coast into a multitude feet, where it is in turn separated from the next to the crests of the divides. Artificial drainage is rower, with a corresponding increase in width of of inlets. Farther south, along the Gal vert Cliffs, | higher plain by an escarpment. seldom employed in this region. the subaerial belt, this gradual change continues as the coast line is much more regular. The streams The Wicomico plain is older than the Talbot and Stream divides. The Patuxent quadrangle, lying, far as the southern part of Massachusetts, beyond which enter the bay in this region are short and has suffered more erosion. The streams which cross as it does, adjacent to Chesapeake Bay and pene­ which the subaerial portion disappears altogether not of sufficient size to modify materially the pre­ it have cut deeper valleys than those in the Talbot trated by the estuary of Patuxent River, both of through the submergence of the entire Coastal Plain vailing unbroken character of the shore. plain and have widened their basins to such an which are at sea level, would naturally be expected province. Off Newfoundland the continental shelf As a whole the coast line is low, monotonous, extent as to destroy, in great measure, the original to show a symmetrical location of divides. Not­ is about 300 miles in width. and extremely irregular. The land bordering the continuity of its level surface. Enough of this withstanding the fact that there is little in. the From the fall line the Coastal Plain has a gentle estuaries of Patuxent River is, in most places, com­ surface remains, however, to indicate the presence character of the materials, position of the beds, or slope to the southeast, generally not exceeding, 5 posed either of marshes or low-lying terraces which of the plain and to permit its identification. comparative proximity to tide water to cause the, feet to the mile, except in the vicinity of the Pied­ pass under the surrounding waters with nothing This plain occurs along Chesapeake Bay and streams entering Patuxent River to cut more mont Plateau, where the slope is in places as great definite to mark where one begins and the other also in the valleys of the principal estuaries. It rapidly than those entering Chesapeake Bay, the as 10 to 15 feet to the mile, or even more. The ends except, here and there, a low cliff which the is well developed in the northeastern portion of divide between the river and the bay is as a whole submerged portion is monotonously flat, as deposi­ waves have cut during seasons of storm or high | the quadrangle in the valley of South River, and considerably nearer the latter, especially in the tion has destroyed most of the irregularities that tide. On the bay shore, however, for a distance j in the central portion of the quadrangle through­ southern portion of the quadrangle. This asym­ were produced by erosion when this portion of 12 miles south of Chesapeake Beach, the char­ out the valley of Patuxent River. It is not well metry of the divide is believed to be due to the rapid formed a part of the land area. The slight ele­ acter of the coast is entirely different. Here the developed along the bay shore south of Herring erosion of the shore line from Herring Bay south­ vation of the subaerial portion, which in few land descends to the water in a sharp, steep cliff, Bay nor in the southwestern portion of the quad­ ward, which has caused the cliffs to recede inland places reaches 400 feet and is for the most part 100 feet or more in height, broken only at intervals rangle. In the valley of Anacostia River, in the and thus cut off the mouth ward portions of the less than half that height, has prevented the by small streams which have cut their valleys to its northwest quarter of the quadrangle, the Wicom­ streams that empty into the bay throughout this streams from cutting valleys of more than mod- base. This is the northern portion of the famous ico plain is represented by scattered remnants. region. The lower courses of many of these crate depth, and throughout the greater portion Calvert Cliffs, which extend southward to a point Capitol Hill, Washington, on which the Capitol streams have been removed so rapidly that stream of the area they flow in open valleys at a level about 25 miles beyond the borders of the quad­ building is located, just outside the quadrangle j erosion has not been able to keep pace with the only slightly lower than that of the broad, flat rangle. boundary, is one of these remnants. wave erosion, so that now the weaker streams cas­ divides. Here and there, however, the country Sunderland plain. The Sunderland plain lies j cade into the bay from the cliffs above. The divide along the stream courses shows noticeable relief, TOPOGRAPHIC FEATURES. at a higher elevation than the Wicomico and between the streams entering the Potomac and though the variations in altitude amount to only a The Patuxent area as a whole exhibits five gen­ extends from about 100 feet to about 200 feet those entering the Patuxent lies well over toward few hundred feet. eral topographic features, which are usually very above sea level. It is usually separated from the the Patuxent valley, but as the tributaries of the The land portion of the Coastal Plain province distinct. These vary greatly in the amount of sur­ Wicomico plain by an escarpment, and in most Patuxent are shorter and more direct than those of that is, the subaerial division is marked by the face that they occupy, but the most noticeable dis­ places another escarpment marks its contact with the Potomac erosion is now more vigorous in the presence of many bays and estuaries representing tinction is that they lie at different elevations. the next plain above. The escarpment separating former basin than the latter, with the result that submerged valleys of streams, carved during a time Tide marshes. The first of these topographic the Wicomico from the Sunderland plain is one of the divide is being pushed rapidly south west ward when the belt stood at a higher level than at present. features to be described consists of the tide marshes the most striking and constant topographic fea­ toward Potomac River. Chesapeake Bay, which is the old valley of Susque- found in the valleys of most of the larger estuaries, tures in the Patuxent quadrangle. The Sunder­ Tide-water estuaries. The lower courses of hanna River; Delaware Bay, the extended valley particularly of Patuxent and Anacostia rivers and land plain is developed extensively throughout almost all the larger streams emptying into Chesa­ of Delaware River; and the tide-water portions of Piscataway and Zekiah creeks. These extend over the eastern half of the quadrangle. It occupies peake Bay have been converted into estuaries Patuxent, Potomac, York, and James rivers are a number of square miles and lie at a level so low the highest portions of the divide between Chesa­ through a submergence which has permitted tide examples of such bays and estuaries, and there are that the tides frequently submerge them in part. peake Bay and Patuxent River and also is well water to pass up the former valleys of the streams. many others of less importance. The streams of The small streams that empty into many of the developed along the western side of Patuxent In the early development of the country these estu­ this area which rise in the Piedmont Plateau or estuaries meander through these marshes, which Valley as far north as the mouth of Western aries were of great value, as they are navigable for farther west are almost invariably turned in a are rapidly encroaching on them. These swamps Branch. In the valleys of Zekiah, Mattawoman, many miles from their mouths and thus afford direction roughly parallel to the strike of the for­ are filled with a growth of sedges and other marsh Piscataway, and Henson creeks and Anacostia means for ready transport of the produce of the mations as they pass out upon the Coastal Plain. plants, which aid in filling up the depressions by River the Sunderland plain, though present, is region to market. Even the advent of railroads has With this exception the structure of the formations serving as obstructions to retain the mud carried represented only by remnants. The surface of not rendered them valueless and much grain and and the character of the materials have had little in by streams and by furnishing a perennial this plain reaches an altitude of about 180 feet fruit are now shipped to market on steamers and effect on stream development, except locally. accumulation of vegetable debris. at Charlotte Hall, just beyond the southern mar­ small sailing vessels which traverse these estuaries. The structure of the Coastal Plain is extremely Talbot plain. The term plain is used in this gin of this quadrangle, and of 200 feet near Ana­ Steamboats from Baltimore pass up the Patuxent as simple, the overlapping beds having almost univer­ folio in a somewhat specialized sense, to include costia. It has suffered more stream erosion than far as Leon, and freight sailing vessels go even sally a southeasterly dip of a few feet to the mile. the terraces along the stream valleys and their con­ the Talbot and Wicomico plains, which lie at lower higher up. the stream. South and West rivers are The materials which are found at the surface of tinuations over the interstream areas, where they levels. similarly navigable for several miles from the bay. the Coastal Plain are bowlders, pebbles, sand, clay, are true plains. Lafayette plain. The Lafayette plain is the Chesapeake Bay and its tributary estuaries also and marl, mostly loose or locally indurated. In age The Talbot plain borders the tide marshes and highest of the plains developed within the Coastal furnish good fishing grounds, and during certain the formations range from Jurassic (?) to Recent. extends from sea level to an altitude of about 45 Plain province. It has a considerable extent in seasons they are frequented by wild waterfowl in Since the oldest formations of the province were feet. This plain is present throughout the quad­ this quadrangle southeast of Anacostia, forming such numbers that they have long been known to laid down there have been many periods of depo­ rangle along the larger streams, and also along the the divide between the valley of Patuxent River sportsmen as among the finest hunting grounds in sition alternating with intervals of erosion. By bay shore. In the northeastern portion of the on the east and the basin of Potomac River on the the country. , reason of local variations in uplift and submergence, quadrangle the Talbot plain is well developed west. Throughout this region the margin of the The channel of the portion of Patuxent River the sea advanced and retreated to different lines in along the lower courses of South and West rivers, Lafayette plain has been extensively removed by included within this quadrangle is about 16 feet in different parts of the region, so that few of the for­ where it extends inland from the bay shore for stream action, but the central portions have been depth in the southern portion and shallows grad­ mations can now be traced by outcropping beds several miles, with a slope hardly sufficient to pro­ practically undisturbed. East of Patuxent River ually to Leon, which is the head of steamboat nav­ throughout the Coastal Plain. Different condi­ duce surface drainage. Along the bay shore south the only remnant of the Lafayette plain caps Mar­ igation. Anacostia River is not navigable above tions therefore prevailed in different areas of the of Fishing Creek the Talbot plain is almost entirely riott Hill, in the southern part of Anne Arundel the bridge between the Navy-Yard and Anacostia. province during each period and great variability absent except for a few remnants situated about a County. The escarpment which separates this South River has a depth of about 16 feet at its in the character and thickness of the deposits has mile north of Parker Creek. In the valley of plain from the Sunderland plain below is well mouth, which increases to 21 feet near Ferry Point, been thus produced. Patuxent River this plain is characteristically defined in the region about Anacostia, where it and then decreases gradually to the upper portion developed. Here it extends in an almost continu­ attains a height of about 50 feet. Near Hughes- of the estuary. The West River channel varies in TOPOGRAPHY. ous belt from the southern margin of the quadran­ ville, Bryantown, and Aquasco, and just beyond depth from 16 feet at its mouth to 11 feet near the gle to Hills Bridge, growing gradually narrower as the southern border of the quadrangle, in the head of the estuary, where navigation ceases. RELIEF. it ascends the streams and broken only by the shal­ vicinity of Charlotte Hall, the escarpment is pres­ The estuaries of South, West, Anacostia, and The Patuxent is the most diversified.of the 30- low valleys of small streams which cut across it in ent, but here it does not exceed 20 feet in height. Patuxent rivers are bordered in many places by minute quadrangles which are located mainly or their course to Patuxent River. North of Hills Throughout the rest of the quadrangle it seems nearly vertical bluffs, 10 to 60 feet in height, or by entirely within the Coastal Plain in Maryland. Bridge and on the western branch of the Patuxent, never to have existed or to have been destroyed or slopes which rise to the height of the broad upland Elevations vary from tide level along the shores of the Talbot plain is present only in scattered rem­ so greatly modified by erosion that its determina­ within half a mile from the river. That the present 3 estuaries alone have not produced the bluffs It has been described by Arthur Keith in the Patapsco and Karitan are considered Lower Creta­ primitive dicotyledons found in the Patuxent as which border them is very evident from the fact Washington folio, as follows: ceous. possibly arising in times prior to the Lower Cre­ that in most places they are now doing little erosive taceous. Until more positive information can be The rock is remarkably uniform-in appearance and PATUXENT FORMATION. work themselves. The small waves which are pro­ has a prevailingly gray color dark bluish gray where obtained they are inclined to refer the Patuxent duced at times of strong winds are the only notable fresh, and yellowish or greenish gray where weathered. Areal distribution. The Patuxent'formation has tentatively to the Jurassic. The formation prob­ agents of erosion. Such waves are frequently able The rock has a rather fine and very uniform texture. a very inconsiderable development at the surface in ably represents a part of the Neocomian-Albian to remove the finer debris which accumulates as It is composed, for the most part, of quartz, orthoclase, the Patuxent quadrangle, although it presumably series of the European geologists. plagioclase, muscovite, and bibtite. With these chief underlies the entire region. Its outcrops are con­ Thickness. The observed thickness ranges from talus at the foot of the cliffs, especially in the early constituents are frequently seen small amounts of garnet, spring, but are not strong enough to do much chlorite, hornblende, tourmaline, and pyrite. The prin­ fined entirely to the northwestern portion of the a few feet to 340 feet, increasing toward the east. undercutting. In general the present cliffs repre­ cipal exceptions to the even texture of the granite gneiss quadrangle, where they occur about Washington On the basis of well data the estimated maximum sent the bluffs that bordered the valleys of streams are the round balls and eyes of quartz aud the knots and and north and west of Anacostia River. In its thickness is about 500 feet. whose flood plains as well as channels are now layers of chlorite and pyrite. These can generally be wider distribution the formation has been recog­ Stratigraphic relations. The Patuxent forma­ covered by the estuarine waters. found in good exposures of the rock, and the quartz is nized in discontinuous outcrops extending from tion in this quadrangle overlies the granite gneiss, conspicuous on weathered surfaces in particular. The water in the estuaries is fresh or very slightly Indian Head, on Potomac River, to Anacostia and of Archean age, and is overlain uncoiiformably by The minerals of the granite gneiss have a marked the Arundel formation, which also is referred ten­ brackish, and ebbs and flows with the tide. There parallel arrangement, in places more, and in places less, Washington and thence northeastward through is seldom any distinct current to be noticed and but always in some degree. This is the result of ineta- Laurel, Relay, Baltimore, Havre de Grace, North­ tatively to the Jurassic. In many places where such as is seen is due to the incoming or outgoing morphism during deformation, the original rock having j east, and Elkton, to the Delaware boundary. Cer­ the Arundel has been removed by erosion the tide and appears to be nearly as strong when mov­ been granite. Where the recrystallization of the miner­ tain deposits in Virginia are also referable to this Patuxent is overlain unconformably by clays, ing upstream as when moving in the opposite als parallel to one another is far advanced, the rock is formation. sands, and gravels belonging to the Columbia a gneiss. Large areas exist, however, in which the direction. Lithologic charactef. The materials composing group. The general strike of the Patuxent for­ schistose planes are not well developed, and even in the mation in this quadrangle is from northeast to Minor streams. The estuaries that form so prom­ most schistose masses portions retain much of their the Patuxent formation are extremely variable, inent a feature in the eastern half of the quadrangle original character in spite of alteration. The formation although prevailingly arenaceous. Buff and light- southwest. Toward the north, however, the strike receive the waters of numerous minor streams. At is therefore termed granite gneiss, as presenting both colored sands, both fine and coarse, predominate, has a progressively more and more pronounced east­ the head of each estuary there is a small stream the original and secondary characters. while beds and lenses of clays and gravels occur ward trend, ranging from north-northeast south of which in almost every case is very much shorter The metamorphosing forces which rendered the granite less commonly. The sandy strata, which usually Washington to east-northeast at the head of schistose were most effective along two belts which coin­ than the estuary itself. Some of the smaller estu­ contain considerable amounts of kaolinized feldspar Chesapeake Bay. A well-defined change in cide with syuclines east of Great Falls and of Washing­ strike is shown at the head of the bay and aries, particularly those in the vicinity of South ton. At similar situations in sedimentary rocks outside and are therefore an arkose, were called by Rogers and West rivers and Herring Bay, continue as of this region close crumpling and schistosity are found, " feldspathic sandstone." The sands are in many another at or near Washington. such almost to the sources of the tribuary streams. and the same phenomena appear in the mica gneiss and places cross-bedded, and with the gravels are here The dip of the Patuxent, as well as of the overly­ Hunting Creek is an example of this type. Parker mica schist near Great Falls. The granite gneiss does and there indurated by oxide of iron to form fer­ ing beds of the Potomac group in Maryland, ranges and Fishing creeks, which enter Chesapeake Bay in not appear immediately along the synclinal axis in that ruginous sandstones. The sands contain small and in direction from east-southeast in its more south­ vicinity, but schistosity becomes more pronounced in the southeastern portion of the quadrangle, are large lenses of clay, which are commonly light in erly exposures to south-southeast farther north. approaching the axis, until even a second system appears, The normal dip of the basal beds of the formation occupied by swamps in their lower portions and cutting through and obscuring the earlier planes. The color, though locally they are highly colored by arc now cut off from free communication with the whole rock mass clearly shows extreme deformation. iron compounds. The drab clays are lignitic in reaches about 60 feet to the mile. In the vicinity waters of the bay by sand bars which have formed Under the tremendous stresses the round balls of quart/ places, and have yielded many impressions of fossil | of the fall line, which is toward the landward mai*- across their mouths. These swamp lands indicate were in places mashed into eyes and lenticular layers. leaves. gin of the Patuxent outcrop, the dip of the basal that the estuaries which formerly occupied the lower The greatest metamorphism resulted in layers which are The following section exposed in the northwest­ beds is considerably greater than this. Southeast now siliceous mica schists. In the latitude of Washing­ courses of these streams have been obliterated by ern part of Washington, just beyond the borders of of Washington it ranges from 50 to 75 feet, but ton the alteration of the granite is greater than anywhere near the fall line it amounts to about 90 feet to the detritus washed in from the surrounding uplands. else in this region, and toward both the north and the this quadrangle, is characteristic of the formation: The same tendency to stream filling is shown along mile. south in this belt the schistosity steadily decreases and Section in northwestern part of Washington, D. C. the margin of the other estuaries mentioned above. the rock has a more and more granitic aspect. Toward ARUNDEL FORMATION. the south the rock also becomes gradually coarser and SUNDERLAND: Feet. Red loam______. 2 DESCRIPTIVE GEOLOGY. less micaceous. These changes are equally clear in the Stratified gravels, sands, and clays ______23 Areal distribution. The outcrops of the^Arundel rock mass and on the smallest scale. Under the micro­ PATUXENT: STRATIGRAPHY. formation within the Patuxent quadrangle are con­ scope the fractures, the dislocation of minerals, and the Coarse white arkosic pebbly sand, some lignitic; fined entirely to its northwestern portion, in and GENERAL DESCRIPTION. growth of new minerals can everywhere be traced. small pellets of white clay, and a lens of light From the fact that the formation was granite, its greenish-drab sandy clay 5 feet in thickness. about Washington, but it is believed to underlie The geologic formations represented in the The strata show both horizontal and cross the greater portion of the quadrangle south and eruptive nature can be inferred. This is also shown in bedding. Amount exposed______15 Patuxent quadrangle range in age from Archean detail by the inclusion of foreign fragments, which east of Anacostia River. In its wider distribution to Recent. Deposition, however, has not been appear in many places near the borders of the mica Paleontologic character. The organic remains of the formation occupies a comparatively narrow, continuous and many gaps occur, that between gneiss, aud also in other situations through the body of the Patuxent formation are neither plentiful nor irregular, and much interrupted belt extending the Archean and Jurassic (?) covering a very long the formation. These inclusions are usually banded and varied. No animal remains have thus far been from Washington to Bush River, near the head identical in appearance with the mica gneiss. Some of interval of time. None of the larger geologic divi­ the inclusions show no banding, but resemble the fine found in deposits of this age within the Patuxent of Chesapeake Bay. There are also outliers of sions since Jurassic (?) time is entirely unrepre­ granitic layers of the mica gneiss. The presence of quadrangle, but a teleost fish has been reported less importance to the north and south of the gen­ sented. Periods when there was deposition over narrow tongues of the granite gneiss in the mica gneiss from beds of apparently the same age on James eral outcrop. At Capitol Hill, Washington, a well part or the whole of the region were separated by points to an eruptive nature for the granite gneiss, but River in Virginia. Plant remains are much more boring, after passing through about 50 feet of other periods of greater or less duration in which the great metamorphism has so obscured the contacts numerous and include thallophytes, equiseta, coni­ Recent and Pleistocene materials, penetrated 131 the entire region was above water and erosion was that they are not conclusive. A somewhat later date fers, monocotyledons, and a few primitive types of feet of exceedingly tough drab and highly colored than the main intrusion is perhaps possible for some of active. The deposits of all the periods except the the granite-gneiss bodies in which the amount of schis­ dicotyledons. Of these remains the more generally lignitic clays which apparently belong to the Arun­ Archean and Pleistocene are similar in many tosity is small. In several places [adjoining the Patux­ observed are the lignitized and silicified trunks of del formation. Beneath these clays the boring respects. With a general northeast-southwest ent quadrangle], for instance west of Annandale and conifers and cycads. During the excavating for passed into the Patuxent sands and gravels. Clays strike and southeast dip, each formation disap­ southwest of Bethesda, the contacts of the massive and the new reservoir in Washington a silicified conifer probably belonging to the Arundel formation were pears by passing under the next later one. In schistose granite are sharp, suggesting that the massive trunk 50 feet in length and several feet in diameter encountered in an excavation for a deep sewer in general also the shore line during each successive granites are intruded into the other. At FourmileEun, was found in beds belonging to the Patuxent for­ the vicinity of Anacostia bridge. above Arlington, also, a massive granite cuts through mation. Another similar trunk about 4 feet in submergence evidently lay a short distance south­ the beds of schistose granite. These more massive bodies Lithologic character. The materials compos­ east of the position it occupied during the previous may be part of the granite gneiss of slightly later age, diameter was found in the vicinity of the Maryland ing the Arundel formation are diverse in litho- submergence. There are a few exceptions to this, or may be of the age of the biotite granite, which is Agricultural College. logic character. The deposit is composed, in great however, that will be noted in the descriptions considerably younger. Name and correlation. The Patuxent formation measure, of large and small lenses of drab and iron- which follow. The traveler passing from north­ The disintegration of the granite gneiss by weathering received its name from Patuxent River, in the basin stained clays which in many places contain concre- west to southeast crosses the outcrops of the forma­ is usually complete at the surface, so that fresh rock can of which the deposits of this horizon were first rec­ .tions, flakes, or ledges of earthy iron carbonate and be found only on the'steeper slopes near the stream cats. ognized as an independent formation and system­ tions in the order of their time of deposition. The After the decomposition of the feldspathic materials the cellular limonite. Iron pyrite and gypsum occur general sequence is shown in the following table: rock becomes a crumbling mass. Complete decomposi­ atically studied. Careful work showed that the less commonly. The clays may be either lami­ deposits formerly included in the Potomac forma­ nated, carrying more or less sand, or massive, Geologic formations in the Patuxent quadrangle. tion results in a stiff red clay mixed with a considera­ ble proportion of sand and mica. The deep road cuts tion were readily separable into four distinct for­ with surfaces exhibiting slickensides. Logs of between Chevy Chase and Washington exhibit this System. Series. Group. Formation. mations on the basis of unconformities and fossil coniferous lignite, usually deposited in a hori­ process finely. Soils of the granite are light and well content (Clark and Bibbins, Jour. Geol., vol. 5, zontal position and greatly compressed, are found drained; on moderate slopes they are fertile, unless fTalbot. embedded within the formation. These logs are exposed to drought, but on the higher Plateau surfaces 1897, pp. 479-506). (.Sunderland. they are leached and poor. The presence of dicotyledonous plants not known in places massed in well-defined beds of such ( Choptank. positively to exist earlier than the Cretaceous has thickness and extent as to be of local use to the \ Calvert. JURASSIC (?) SYSTEM. led paleobotanists to regard the Patuxent as Lower miners for fuel. Occasionally large stumps are 1 ( Nanjemoy. POTOMAC GROUP. 1 Aquia. Cretaceous. Fbntaine, in his study of the Patux­ discovered standing buried in the position in f Monmouth. ( Upper Cretaceous . . The Potomac group of the Coastal Plain consists ent flora, states that there is an " overwhelming which they grew, with the roots and trunks fos­ Cretaceous. .... { [ Magothy. of highly colored gravels, sands, and clays which percentage of Jurassic types," although he refers silized by iron carbonate and iron sulphate. Seeds { Lower Cretaceous . . ( Raritan. outcrop along a sinuous line from New York to the Potomac flora as a whole to the Cretaceous. of plants are found near some of these beds. ] f 1 Patapsco. ! Potomac . . \ ( Arundel. Richmond, passing near the cities of Philadelphia, As will be shown later, the Patuxent formation Locally the clay is charged with comminuted \ ( I Patuxent. Wilmington, Baltimore, and Washington. The lies unconformably beneath the Arundel, in which lignite, when it is termed "charcoal clay" or g Potomac deposits are of great value because of the vertebrate remains of Jurassic types have been dis­ "charcoal ore." Here and there this "charcoal excellent brick clays which they contain. All four covered. It would thus seem that the evidence clay" bears osseous remains. Near Muirkirk, a ARCHEAN ROCKS. of the formations which have been recognized as furnished by vertebrate paleontology and paleo- short distance north of the Patuxent quadrangle, GRANITE GNEISS. composing this group are represented within the botany is not in strict harmony. Clark and Hatcher obtained from it dinosaurian and other Granite gneiss occupies small areas in the vicin­ Patuxent quadrangle. As stated in the descriptions Bibbins are inclined to regard the evidence fur­ organic remains. Where the Arundel formation has ity of Riggs Mills and along SIigo Branch, in the which follow, the two lower formations are here nished by the fossil vertebrates as being perhaps been exposed to the atmosphere the carbonate ores extreme northwestern portion of the quadrangle. tentatively assigned to the Jurassic system; the more reliable for correlation and to regard the have at some places changed to the hydrous oxides Patuxent, of iron to a considerable depth. Where this has LlUiologic character, The Patapsco formation is clays are not so highly colored. White and buff subangular quartz grains which range in color from occurred, clays which were originally drab colored composed chiefly of highly colored and variegated sands; stratified sandy clays, light chocolate in pure white to a dark ferruginous brown. At "many have become red or variegated. Along the western clays, interbedded with sandy clays, sands, and color, in places containing leaf impressions; light- places lenses or bands of brown sand occur within margin of the formation the material becomes are­ gravels, the materials of different kinds grading colored argillaceous sands and sandy clays ("fuller's the lighter colored sands. Normally the deposits naceous and locally consists of lenses of sand. into each other both horizontally and vertically. earth"); and white, yellow, drab, bluish drab, and of sand are loose, yet locally the iron derived from The section exposed at the Muirkirk iron mine, In many places the arenaceous material in the vicin­ variegated clays all occur in deposits of this age. this and adjacent formations has firmly cemented where the best dinosaurian remains thus far obtained ity of clay beds is indurated to a conglomerate or The drab clays are here and there lignitic and pyr- the grains together to form an indurated iron sand­ from this formation were found, is as follows: rough, irregular, pipelike concretionary mass called itiferous, and in places exhibit partings of sand stone or conglomerate. A thin ledge of such a "pipe ore." The variegated clays exhibit a great indurated with mammillary limonite. Ledges of sandstone near the Catholic Church west of Priest Section at iron mine, MuirJcirk, Md. variety of rich and delicate tints in. irregular pat­ sandstone, indurated by iron oxide or silica, are Bridge forms a small waterfall in a tributary of RECENT : Feet. terns. In places they grade downward or horizon­ common. The light-colored sands show in many Patuxent River. Just below Overlook Inn, on Surface wash, consisting of loam and gravel _- 10 PATAPSCO : tally into massive clays of chocolate, drab, and localities large blotches of red ocher, locally desig­ East Washington Heights, there is a ledge of Sands and gravel, indurated in places by iron black tones, locally carrying lignite and pyrite and nated as "paint pots." The Raritan deposits can massive brown sandstone of this character. Less oxide and containing silicifled trunks of con­ ifers and cycads______L__- 10 in some places containing iron ore and leaf impres­ not everywhere be separated with ease from the commonly the Magothy quartz sands are cemented Massive and stratified, mottled and variega­ sions. The sands, which are very commonly cross- underlying Patapsco strata, but there is much less together with silica to form very hard siliceous ted clays and sandy clays with redeposited nodules of iron carbonate and some limon- bedded, here and there carry decomposed grains of difficulty in separating them from those of the over­ sandstones, which from their lithology can scarcely ite, pebbly at base, flanking the subjacent feldspar and pellets of white clay. A red ocher lying Magothy formation, which are much more be distinguished from siliceous sandstones of Pale­ member ______5tol5 that is locally known as "paint rock" or "paint uniform in character and less highly colored. ozoic age that are quite unlike the usual Coastal ARUNDEL: Massive blue clay with flakes and nodules of stone" is not uncommon, and limonite with botry- Paleontologic character. Both animal and plant Plain materials. The very hard white sandstone iron carbonate and containing bones and oidal surfaces is found at various horizons. remains have been found in the Raritan formation, rocks well exposed on either side of the public road teeth of dinosaurs at base..----___------20 to 40 Highly lignitic lens of clay ("charcoal ore"). 2 Paleontologic character. The Patapsco formation but as in the case of other formations of the Poto­ about 1J miles north of Collington represent this Tough blue clay containing iron carbonate.- 15 contains a rich flora of ferns, cycads, conifers, mac group, the known fauna is very scanty both phase. PATUXENT: monocotyledons, and dicotyledons. The dicotyle­ in individuals and species, the flora being much The argillaceous character of the Magothy is White sand; amount exposed___----_-_---___ 10 donous plants still constitute a minor element as more abundant. Logs of lignitized conifers exhib­ very prominent in some localities, although it is Pcdeontologic character. The fossil flora of the compared with the other types of vegetation repre­ iting teredo borings have occasionally been found, usually subsidiary to the arenaceous phase. The Arundel formation includes thallophytes (?), ferns, sented. The range of genera and species is limited, and in New Jersey the formation has yielded some clay commonly occurs as fine laminae alternating cycads, conifers, monocotyledons, and dicotyledons. the grade of organization low, and the number of bones of a plesiosaur. No dinosaurian remains with the sand layers. Drab is the characteristic By far the most common of these are the conifers, individuals scarcely greater than in the preceding have thus far been found in Raritan strata. color of the Magothy clay, but here and there the with whose lignitized trunks the clays are, in places, formation. The fauna of the Patapsco consists of The flora of the formation includes ferns, fronds presence of considerable vegetable remains renders densely packed, forming local beds of lignite. That a few molluscan shells and a single dinosaurian of cycads, conifers, monocotyledons, and dicoty­ it black. The vegetable material may be finely these are largely sequoian trunks is suggested by limb bone. This latter fossil, which was found at ledons, the last-named forms being particularly divided or may occur in the form of large pieces the common association with them of the casts of the surface of the formation, was much worn and conspicuous and relatively modern in aspect. The of lignite. Thus far no bright-colored clays have sequoian cones preserved in iron carbonate. Leaf may have been redeposited from the Arundel. Raritan has yielded no silicified trunks of cycads, been recognized in the Magothy deposits. impressions are also present in the iron ores. Name and correlation. The Patapsco formation so far as is definitely known, and in this respect The Magothy can usually be differentiated from The animal remains, while nowhere abundant, received its name from Patapsco River, in whose its flora is sharply contrasted with that of the the underlying Raritan formation by its lack of represent a wide variety of forms. They include j valley it is typically exposed. Patapsco formation. massive beds of brightly colored variegated clay, worm or insect borings, pelecypods, gasteropods, | The presence of primitive dicotyledonous types Name and correlation. The formation receives and by the greater variability in the character of dinosaurs, turtles, and crocodiles. The Dinosauria, together with other plant remains early led the its name from Raritan River, New Jersey, in the its materials. It can be more easily distinguished of which a number of species have been recognized, paleobotanists to refer the Potomac beds as a whole basin of which it is typically developed. It from the overlying Matawan by the almost com­ greatly predominate. One of them was about 40 to the lower Cretaceous. Later, work by Clark includes the deposits long called the Plastic plete absence of glauconite (although small pockets feet in length. The occurrence of these animals and Bibbins showed that the deposits which had clays by the New Jersey Geological Survey. of green sand have been found in the Magothy at points to the probable Jurassic age of the Arundel been included under the name Potomac consisted On the basis of the plant fossils, which show a a few localities), by its lack of homogeneity, and by formation. in reality of four distinct formations. The lower marked resemblance to forms of Lower Cretaceous its variations in color. Moreover, the Matawan in Name and correlation. The Arundel formation two carry a Jurassic fauna and types of dicotyledons age in Europe, the formation has been regarded as Maryland usually contains considerable amounts received its name from Anne Arundel County, still more archaic than those found in the upper representing in part the Neocomian-Albian series. of mica in small flakes, whereas the Magothy con­ where the deposits of this horizon are typically two formations. This led to the separation of the Thickness. Within this area of outcrop in the tains little mica. developed and well exposed. two lower formations, the Patuxent and the Arun­ Patuxent quadrangle the Raritan formation is Paleontologic character. In this quadrangle the Although dicotyledonous plants have been found del, from the two upper, the Patapsco and the Rari- relatively thin in comparison with its thickness only organic remains thus far recognized in the in the Arundel deposits, yet the presence of saurian tan. The former have been referred tentatively to farther northeast. The estimated maximum thick­ Magothy are leaf impressions in the drab clays remains that seem to belong to undoubted Jurassic the Jurassic; the latter are still referred to the ness toward the extreme eastern margin of the belt that occur in thin laminae alternating with layers types has caused Clark and Bibbins to refer this Lower Cretaceous. of outcrop in this quadrangle is about 100 feet. of sand. Although most of these are fragmentary, formation, together with the Patuxent, which under­ Thickness. The thickness of the Patapsco is The thickness of the formation seems to increase many identifiable forms are present. At Cliffwood lies it, tentatively to the Jurassic, as stated in a somewhat variable, gradually increasing to the toward the southeast beyond the line where it dis­ Point, on the south shore of Raritan Bay, New7 preceding section. southeast. Within this quadrangle the outcrop­ appears beneath later deposits. Jersey, beds of this formation have yielded a con­ Thickness. The maximum thickness of the ping thickness is about 100 feet. In some places, Stratigraphic relations. The Raritan uncon- siderable flora and a marine fauna. The flora Arundel is 125 feet or more and the formation east of its outcrop, the formation is estimated to have formably overlies the Patapsco formation, and studied by Berry (Bull. New York Bot. Gard., vol. thins out and disappears in some areas. At Wash­ a thickness of about 200 feet. is separated from the overlying Magothy by 3, No. 9, 1903, pp. 45-103; Bull. Torr. Bot. Club, ington, as shown in the well boring at Capitol Hill, Stratigraphic relations. The Patapsco formation another marked unconformity. In the region vol. 31, 1904, pp. 67-82; vol. 32, pp. 43-48; Ann. if the reference of this material to the Arundel for­ elsewhere overlies the Patuxent-or the Arundel of its outcrop, Pleistocene deposits of the Tal­ Rept. State Geol. New Jersey for 1905, pp. 135- mation is correct, the thickness is about 130 feet. formation of the Potomac group, and in this region bot, Wicomico, and Sunderland formations over­ 172) is notably varied, over 100 species having Stratigraphic relations. The Arundel formation it probably occupies similar relations, although the lie the edges of the Raritan and generally conceal been described. The flora presents many points of this quadrangle overlies the Patuxent and is few deep-well sections are not complete enough to the deposits from view except where erosion has of similarity to that of the Raritan, yet it contains overlain by the Patapsco, with both of which it is determine certainly the character of the contact removed these later beds. The strike and dip of 49 species that are peculiar to the Magothy in this unconformable. Where the Patapsco has been with the underlying beds. It is overlain uncon- the Raritan formation correspond closely with those country, one or two of the number having been removed by erosion the Arundel is overlain uncon- formably by the Raritan' formation for the most of the Patapsco. The normal dip of the basal beds found in Europe. The most common fossil plants formably by clay, sands, and gravels belonging to part, although here and there in the region of its is about 30 feet to the mile, but this increases of that locality are the imperfectly petrified cones the Lafayette and Columbia deposits. The strike outcrop it is covered by Pleistocene deposits belong­ toward the fall line. of Sequoia gracillima. Other common species 'are and dip of the Arundel formation are approxi­ ing to the Talbot and Wicomico formations. The UPPER CRETACEOUS SERIES. Cunninghamites squamosus, Dammara cliffivood- mately the same as those of the Patuxent, The general strike of the Patapsco corresponds practi­ ensis, and Sequoia Reichenbachi. Berry and Hoi- usual dip is 40 to 50 feet to the mile, but there is a cally to that of the formations which lie beneath it. MAGOTHY FORMATION. lick state that the flora of the "Cliffwood beds" well-marked increase near the fall line, where the The normal dip of the basal beds is southeastward Areal distribution. The Magothy formation out­ shows Cenomanian characteristics. average is about 72 feet to the mile. At Washing­ at the rate of 35 to 40 feet to the mile, but the dip, crops in discontinuous areas in the Patuxent quad­ The animal remains described by Weller (Ann. ton it is 66 feet to the mile. like that of the preceding formations, increases rangle, extending from the Patuxent River valley Rept. State Geol. New Jersey for 1904, pp. 133- toward the fall line. in the vicinity of Priest Bridge south west ward to 144) from the Magothy at Cliffwood Point were CRETACEOUS SYSTEM. the Potomac River valley just beyond Congress found in smooth concretionary nodules in a clay .LOWER CRETACEOUS SERIES. RARITAN FORMATION. Heights. It does not outcropu in a continuous bed or lying loose on the beach, where they were PO TOMA C GROUP Con tin ucd. Areal distribution. In its wider distribution the belt because of an overlap of the Matawan, which left by the erosion of the clay beds that originally PATAPSCO FORMATION. Raritan formation has been recognized from Raritan is in some places sufficient to bring that formation contained them. The fauna is characterized by the Arced distribution. The Patapsco has a more Bay, New Jersey, to the basin of Potomac River, in immediate contact with the Raritan. An occur­ presence of great numbers of crustacean remains. extended development within this quadrangle than having a more extensive distribution than any rence of this kind can be seen about three-fourths Some portion of a crab seems to have been the either of the two preceding formations. Its outcrop other member of the Potomac group. In the north­ of a mile west of Brightseat. The best exposures nucleus about which the nodules were formed in is confined to the northwestern portion of the western portion of the Patuxent quadrangle it is lie from half a mile to 3 miles west of Priest Bridge almost every instance. Pelecypods, gasteropods, quadrangle, extending from Anacostia northeast­ represented by a narrow outcrop which crosses the and along the west slope of Good Hope Hill from and cephalopods also occur. The most abundant ward to the boundary and occurring in narrow area in a sinuous line from northeast to southwest St. Elizabeth's to the junction of Benning and forms are the following pelecypods: Trigonarca sp., bands near the headwaters of a few of the streams and is also present near the headwaters of some of Bowen roads on the District line. Pteria petrosa, Nuculana protexta (/), Yoldia evansi, south of Anacostia. To the southeast of this out­ the creeks along the western margin of the quad­ Lithologic character. The Magothy formation is Isocardia cliffwoodensis, Veleda lintea, Corbula sp., crop it is supposed to extend over the entire quad­ rangle. It dips under the overlying strata and is composed of extremely varied materials and may and among the Crustacea Tetracarcinus subquad- rangle, underlying all the formations of later age. believed to extend over the entire area of the quad­ change abruptly in character both horizontally and ratus. These are of considerable importance, for, In its wider distribution the Patapsco formation has rangle beneath the younger formations. vertically. Loose sands of light color are the most with the exception .of a few forms from the Raritan been recognized in discontinuous outcrops from the Lithologic character. The Raritan consists of prominent constituents. These sands usually show in the same area, they are the earliest marine fossils valley of Schuylkill River, near Philadelphia, to variable materials similar to those composing the fine laminations and locally considerable cross- found in the deposits of the Atlantic Coastal Plain. the valley of the Potomac, in Virginia. Patapsco formation except that, in general, the bedding. The sand consists of coarse, rounded to Weller states that the assemblage of forms consti- tiites a distinct fan mile which more nearly resem- \ some places the deposits consist ahnost entirely of The Monmouth beds of New Jersey, which are attain a thickness of 1 to 2 feet. Several exposures bles tlie faunule of the Matawan formation than black clay; in others, particularly where the upper continuous with those of this region, have been dif­ of the Aquia formation, showing these iron segre­ any other. ! beds are exposed, the arenaceous phase is predomi­ ferentiated into three members. These divisions have gations, are to be seen in the region of Rutland Name and correlation. In 1893 Dartbn (Am. j nant and the beds may consist entirely of sands not been recognized in the Patuxent quadrangle. and Riverview. Near Upper Marlboro there are a Jour. Sci., 3d ser., vol. 45, pp. 407-419) described | varying in color from white to dark-greenish black. Paleontologic character. The Monmouth forma­ few ledges of indurated marl from which numerous certain deposits in northeastern Maryland for which | Where the glauconite decomposes, the iron oxidizes tion is generally very fossiliferous and the forms species of fossils have been obtained. This is one he proposed the name Magothy, because of the ! and the materials are stained reddish brown, and are usually well preserved. They consist of fora- of the earliest and best known localities for fossils excellent exposures of the beds along Magothy j may even become firmly indurated by the iron minifers, pelecypods, gasteropods, and cephalopods. in the Eocene of the Atlantic slope. The follow­ River. Later work in Maryland seemed to indi- | oxide. Iron pyrite is also a common constituent Among the most abundant are Exogyra costata ing section is exposed: cate that these deposits represented merely phases and in places a small layer of gravel lies at the Say, Gryphcea vesicularis Lamarck, Idonearca vul- Section east of bridge at Upper Marlboro, Md. of deposition within the Raritan. On this suppo- | base of the formation. Although the Matawan garis Morton, Cardium perelongatum Whitney, and NANJEMOY: Feet, sition the beds were mainly included in the Rari- j contains varied materials it is much less variable Belemnitella americana Morton. They are typical (iflauconitic clay---______-_-____-_---_---_---- 22 tan, the fossil plants described from them were j than formations of the Potomac group or the Upper Cretaceous species. Pink clay, without glauconite or fossils ______22 AQUIA (Paspotansa substage): called Raritan forms, and the stratigraphic break j Magothy formation, and throughout its extent in Name and correlation. The name of the forma­ Coarse glauconitic sand ______-___-_._--__ 82 between these and the underlying beds was attrib- \ Maryland can generally be readily recognized by tion was first proposed in 1897 by W. B. Clark Shell marl with Gibbula yluitdula, Fissuridta uted to contemporaneous erosion. In New Jersey | the prevailing dark-colored micaceous glauconitic (Bull. Geol. Soc. America, vol. 8, pp. 315-358), marlboroensis, Lucina aguiana, Diplodonta marlboroensis, Venericardia planivosta var. the Magothy deposits in the vicinity of Philadel­ sand of which it is chiefly composed. when it was decided to combine in a single forma­ regia, Pteria limula, Cucullaia gigantea, Leda phia were placed in the Raritan, while those in the Paleontologic character. Although the Matawan tion the deposits formerly included in the Nave- parilis, Ifucula ot5w7a____-_.___--_---_--_---_ 2 Indurated ledge with TurriLeUa mortoni, T. region of Raritan Bay, under the name Cliff wood \ formation as a whole can not be regarded as sink and Redbank formations. This name was hnmerosa, Mesalia obruta, Calyptraphorus beds, were by some geologists included in the | extremely fossiliferous, yet it contains bands in suggested by Monmouth County, N. J., where the jacksoni, Panopea elongata, Meretrix ovata Matawan on account of the presence of glauconite j which organic remains are crowded together in deposits of this horizon are characteristically devel­ var. pyga, Dosiniopsia lenticularis, Veneri­ cardia planicosta var. regia, Crassatellites and the great percentage of post-Raritan plants and great abundance. Such a band occurs in the oped. It was employed for the term Lower Marl alceformis, Astarte marylandica, Qlycimeria marine invertebrates, and by others were placed in cutting where the Chesapeake Beach Railway bed of the earlier workers in New Jersey. On idoneus, Cuculla'a gigantea, Leda parilis, Nucula ovula ______5 the Raritan. Recent studies of the fossils and crosses Central avenue just east of the District the basis of its marine fauna it is correlated with Glauconitic sand (known as Bryozoaii sand) careful stratigraphic work in the field, however, have line. In New Jersey as well as in Maryland the Upper Senonian of Europe. full of fine fragments of shells accompanied shown that the Magothy should be regarded as a the formation has vielded a varied fauna of fora- Thickness.- The maximum thickness of the by Bryozoa, echinoid spines, and Foraminif- *s era; and with Ostrea coinpressirostra, Gry- distinct formation, on both stratigraphic and pale- minifers, pelecypods, gasteropods, scaphopods, and Monmouth formation along its outcrop in the phceostrea vomer, and Platidia ma.rylandica. 5 ontologic grounds, and these transitional beds from ammonites (Bull. Geol. Soc. America, vol. 8, 1897, area of the Patuxeut quadrangle is from 40 to New Jersey southward have been referred by Clark pp. 330-331). 50 feet. In northern New Jersey it is about 200 (Am. Jour. Sci., 4th ser., vol. 18, 1904, pp. 435- Name and correlation. The formation has feet thick, but it steadily decreases in thickness Paleontologic character. A great many fossils 440) to the Magothy formation as defined by Darton received its name from Matawan Creek, a trib­ along the strike southwestward, until it finally are to be seen in the outcrops of the Aquia along- for the Maryland area. Uhler, in several articles utary of Raritan Bay, in the vicinity of which disappears as an outcropping formation in the South and Patuxent rivers and in the valleys of (Trans. Maryland Acad. Sci., vol. 1, 1888-1892), the deposits of this horizon are extensively and north-central part of this quadrangle. Piscataway, Monmouth, and Nanjemoy creeks in named a group of beds the Alternate sand series. typically, developed. It was proposed by W. B. Stratigraphic relations. The Monmouth is con­ Maryland, and of Potomac and Aquia creeks in Most of these are now placed in the Magothy. On Clark in 1894 (Jour. Geol., vol. 2, pp. 161-177), formable with the underlying Matawan and with Virginia. An idea of the variety of fossils that the basis of the flora found in the beds at Cliffwood and replaced the term Clay marls, previously used the Rancoeas, which overlies it on the Eastern occur in these localities may be gained by consult­ the formation is provisionally correlated with the by the New Jersey geologists. The fossils of the Shore of Maryland and in Delaware and New ing the section above. The fossils of this forma­ Cenomanian of Europe. Matawan formation furnish evidence of its Upper Jersey. Within the Patuxent quadrangle it is tion have been described and illustrated in the Thickness. Within the Patuxent quadrangle Cretaceous age and apparently indicate that the overlain unconformably by Eocene and Pleisto­ report on the Eocene issued by the Maryland the maximum thickness of the Magothy formation beds represent a part of the Senonian of Europe. cene deposits. The Monmouth is readily dis­ Geological Survey. is about 40 feet, but in its wider extent the thick­ Thickness. The maximum thickness of the tinguished from the Matawan, as it lacks the Name and correlation. The formation receives ness is extremely variable, reaching a maximum of Matawan occurs along North Run and is about darker colored micaceous sands and marls of that its name from Aquia Creek, a tributary of Potomac about 1.00 feet. This variability is due to greater 45 to 50 feet. From this run the formation grad­ formation. From the Rancocas it is distinguished River in Virginia, where deposits belonging to this deposition in some regions than in others and also ually thins toward the southwest until it is not by the great predominance of reddish-brown sand. horizon are characteristically developed. This to the removal of considerable Magothy material more than 30 feet thick in the exposures along The Aquia contains much more marl. The strike name was proposed by W. B. Clark in 1895 (Johns in certain areas. Henson Creek. Like many other Coastal Plain of the Monmouth formation is from northeast to Hopkins Univ. Circ., p. 3). Stratigraphic relations. The Magothy formation formations, the beds thicken as they dip beneath southwest, and the dip is toward the southeast at The formation is correlated with the lower lies between the Raritan and Matawan formations later, deposits, but the records of wells which the rate of about 25 feet to the mile. division of the Wilcox ("Lignitic") of the Gulf and is separated from each by an unconformity. have penetrated these formations in the eastern region. According to Dall (Eighteenth Ann. Rept. TERTIARY SYSTEM. The line of contact between the Magothy and the part of the quadrangle are too general to permit U. S. Geol. Survey, pt. 2, 1898, pp. 327-348) it Raritan is very irregular, indicating a considerable the determination of the amount of thickening. KOCESTE SERIES. represents a part of the Suessonian of Europe. erosion interval between the times of their deposi- j Stratigraphic relations. In places a marked PAMUNKEY GROUP. Thickness. The Aquia formation is about 100 tion. In many places the Magothy deposits fill unconformity separates the Matawan from the feet thick in this quadrangle and gradually thick­ pockets and old channels in the Raritan. The underlying Magothy formation, but it is conform­ Areal distribution. Within this quadrangle the ens toward the east, beneath the later formations. s unconformity between the Magothy and the Mata­ ably overlain by the Monmouth. The separation Eocene is represented by both the Aquia and Stratigraphic relations. The Aquia formation wan is not so plainly marked; at many places these between the Matawan and Monmouth is made Nanjemoy formations. The Aquia is exposed overlies the Monmouth unconformably and is beds seem to be conformable. Indications of an- chiefly on the basis of change in lithologic char­ throughout a broad belt, 10 miles or more in width, overlain conformably by the Nanjemoy forma­ erosion interval may be seen in some good expo­ acter, but in part on that of the fossil contents. extending from the northeast corner of the quad­ tion. Where the Nanjemoy has been removed sures, however, and in the area of the Patuxent Although some organic forms range through both rangle southwestward as far as Western Branch of by erosion it is covered by Miocene, Lafayette, or quadrangle between Patuxent and Potomac rivers the Matawan and Monmouth, yet each formation Patuxent River. Beyond the latter point the for­ Pleistocene beds. The formation has a northeast- there is a marked unconformity of overlap. A has a few characteristic forms, the assemblage in mation is buried beneath later deposits and outcrops southwest strike and dips to the southeast at the short distance northeast of the District of Columbia each being on the whole fairly distinctive. The only in a thin band near the headwaters of the rate of about 12^ feet to the mile. line the Magothy is entirely lacking, its absence formation strikes from northeast to southwest and creeks along the western margin of the quadrangle. Subdivisions. The Aquia formation has been being due to an overlap of the Matawan, which dips southeastward at about 25 feet to the mile. The Aquia formation dips to the southeast and is subdivided into two members or substages known as rests upon the Raritan. Farther south it again j supposed to underlie the younger Eocene and Mio­ Piscataway and Paspotansa, which are distinguished MOSMOUTH FORMATION. makes its appearance. In the region of its outcrop cene beds throughout the southern portion of the from each other by their contained fossils. the formation is in many places overlain by Pleis­ Areal distribution. Within this* quadrangle the area. In its wider distribution it extends from Vir­ The Piscataway member was named from Pisr- tocene deposits. Monmouth formation has only a slight develop­ ginia northeastward across Maryland to Delaware. cataway Creek, Maryland, where it is typically The strike of the Magothy formation is roughly ment. It outcrops in the vicinity of Collington Lithologic character. This formation consists developed. The member is characterized by two parallel to that of the other Coastal Plain forma­ arid eastward from that place to Patuxent River usually of loose sand in which there is a consider­ well-marked and rather persistent layers of indu­ tions from northeast to southwest. The dip is and thence southward along the banks of the able admixture of glauconite, the latter in places- rated marls. Its thickness somewhat exceeds 50 southeastward, at about 30 to 35 feet to the mile. stream to the vicinity of Governor Bridge. It making up the body of the formation. Where the feet. It is further characterized by a fossil fauna also occurs in the valleys of the headwaters of material is fresh it ranges in color from a light blue among which are the following forms: MATAWAX FORMATION. South River. The Monmouth dips to the south­ to a very dark green, but in regions where it has Thecachampsa serieodon (?) Cope. Area I distribution. In this quadrangle the Mat­ east and is believed to underlie the Eocene and been exposed to weathering for a-considerable time Synechodus clarkii Eastman. awan formation is found in a sinuous line extending Miocene deposits to the southeast of its outcrop. it has assumed a reddish-brown to light-gray color.* Odontaspis elegans (Agassiz). Otodus obliquus (Agassiz). from the head of South River southwestward to In its wider distribution the formation has been The beds are in most places unconsolidated, Pholadomya marylandica Conrad. Henson Creek. Throughout this area it is exposed recognized by outcrops in a zone extending from although locally some have become very firmly Grryphgea vesicularis Lamarck. Terebratula harlani Morton. along the margins of the streams, but is covered up the northeastern portion of this quadrangle to indurated by oxide of iron. Small, well-rounded Textularia subangulata D'Orbigny. by younger material as it passes under the divides. Raritan Bay in New Jersey. pebbles coated with iron oxide occur in a few places The Paspotansa member was named from Pas­ The Matawan resembles the other Cretaceous for­ Lithologic character. The formation is prevail­ near the base of the formation. These gravels are potansa Creek, Virginia. It consists of a bed of mations in having a dip to the southeast which ingly arenaceous in character and unconsolidated typically exposed about a mile northwest of West­ greensand and greensand marl somewhat less than carries it beneath later deposits. It undoubtedly except where locally indurated by the segregation phalia and in numerous places about Collington. 50 feet thick. Among the characteristic fossils of underlies the entire quadrangle to the southeast of of ferruginous material derived from the glauconite. About half a mile southwest of Collington this this member are the following: the line of outcrop. In its broader distribution The sands composing the Monmouth deposits vary pebble layer, which is about 2 feet in thickness, has Bythocypris subsequata Ulrich. through the Coastal Plain, the Matawan formation . in color from reddish brown to dark green or nearly been cemented by ferruginous material into a hard, Pleurotonia harrisi Clark. extends as a continuous series of outcropping black. The fresh material always contains con­ compact rock that has been used for building Cancellaria graciloides xlldrich var. deposits from Raritan Bay to Potomac River. siderable glauconite and this gives to the deposits purposes. Where the Aquia deposits have been Trophon sublevis Harris. Chrysodomus engonatus (Heilprin). Lithologic character.- The Matawan consists their dark color. In their more weathered por­ exposed to the action of the atmosphere, as on the Calyptraphorus jacksoni Clark. chiefly of glauconitic sand intimately mixed with tions the sands generally range in color from rich tops of divides, the iron present in the glauconite Discosparsa varians Ulrich. Membranipora angusta Ulrich. dark-colored clay, while all through the material brown to reddish brown, but at some places they has been segregated to form bands of iron ore. Textularia gramen D'Orbigny. small flakes of mica are commonly found. In are dark gray. These iron bands are very numerous and in places Anomalina ammonoides (Reuss). Patuxent. 6

NANJEMOY FORMATION. Ft. In. to Potomac River. It is characteristically clayey, following fossils: /Siphonalia devexa, thick, is greenish blue when fresh, but weathers Areal distribution. The Nanjemoy formation is especially in its lower portions. It is about 60 to Ecphora tricostata, Turritella plebeia, to a brown or a light-buff to white color on long much less extensively exposed in this quadrangle 65 feet thick and carries the following characteristic T. variabilis, T. variabilis var. cum- exposure to the atmosphere. In the extensive pits berlandia, Polynices Tieros, Corbula than the Aquia. It is well developed in the head­ fossils: incequalis, Phacoides anodonta, Cras- at Lyons Creek, where the material is worked com­ waters of the streams south of South River and I satellites melinus, Astnrte cuneiformiv, mercially, the transition from greenish blue to buff Cyprsea smith! Aldrich. Pecten madisonius, Venus rileyi, Chione extends thence across the quadrangle toward the Solen lisbonensis Aldrich. latilirata, Cytherea staminea, Mtlina is very conspicuous. southwest in a very circuitous and broken outcrop. (?) Lucina astartiformis Aldrich. maxillata, Atrina harrisii, Area siib- The low cliffs which border Chesapeake Bay In its larger relations it extends from Virginia Periploina sp. rostrata, Qlycymerisparilis, etc-__--_-_ 9 0 south of the pier at Fairhaven are composed of Ceiropora micropora G'oldfuss. Bluish-green clayey sand carrying Corbula northwestward through Maryland as far as Chesa­ elevata ____---___...._..__-..._....._.___ 2 0 diatomaceous earth with a capping of Columbia peake Bay. On the Eastern Shore it does not out­ This member is further subdivided into six zones Bluish-green clayey sand carrying imper­ gravel. From Fairhaven the diatomaceous. beds fect casts of Corbula elevata (.)__ -___- 10 0 crop and is so deeply buried by later deposits that which, together with their characteristic fossils, are Bluish-green clayey sand containing large cross southern Maryland in a northeast-southwest it has not yet been recognized with certainty in fully discussed by Clark and Martin in the report numbers of Corbu la elevata ------3 0 direction, following the line of strike, and are well borings. already cited (Eocene, Maryland Geol. Survey, Bluish-green clayey sand containing fossil worked at Lyons Creek on the Patuxent, and at casts of Corbula elevata- ______3 0 Lithologic character. The Nanjemoy formation 1901, pp. 65-66). Pope Creek on the Potomac, a short distance south consists primarily of greensand, which is in most The Woodstock member has been named from 100 0 of this quadrangle. They may also be found at places highly argillaceous and locally calcareous, Woodstock, an old estate situated a short distance Paleontologic character. The diatomaceous earth numerous places between these points, in cuts with certain layers carrying abundant crystals and from Mathias Point on the Virginia side of the and the dark-colored clays represented in the Cal­ made by waterways. Southeast of this diagonal crystalline masses of gypsum. The formation con­ Potomac. This member is characterized by fine vert of this quadrangle contain abundant casts of line they gradually disappear below tide. The tains considerable clay, especially at its base, as homogenous greensands and greensand marls which marine mollusks, almost invariably of small size. Fairhaven diatomaceous earth is further subdi­ shown in the section at Upper Maiiboro already are less argillaceous than the underlying Potapaco The fossils are allied to forms now living in lower vided into three zones that are recognized by the given. The following section is fairly typical and beds. It ranges in thickness from 60 to 65 feet and latitudes, thus indicating that the climate in this materials and fossils which thev«/ contain. characteristic of the glauconitic phase: contains certain characteristic fossils, a few of which region during the deposition of the Calvert mate­ The Plum Point marls constitute the remainder Section in ravine 1 mile south of Thrift, Hd. are the following: rials was somewhat warmer than that of to-day. of the Calvert formation above the Fairhaven dia­ The fossils of this formation have been fully tomaceous earth. At Plum Point, Calvert County, MIOCENE: Ft. in. Pyrula penita Conrad var. » Lead-colored clay with Miocene fossils-^... 40 0 Meretrix lenis (Conrad). described and illustrated in two volumes on the the beds are typically developed, and this fact has EOCENE (Nanjemoy-Potapaco substage): Leda parva (Rogers). Miocene issued by the Maryland Geological Sur­ suggested the name of this member. It consists of Dark argillaceous greensand.-__ ._-__-._-_ 7 0 Spiroplecta clarki Bagg. vey in 1904. a series of sandy clays and marls in which are Argillaceous greensand, packed with Vener­ Nonionina affinis Reuss. icardia potapacoensis- .___-_.-______1 0 Carpolithus marylandicus Hollick. Name and correlation. The formation receives embedded large numbers of organic remains, Dark glauconitic clay..____-..__-... ___--__ 8 0 Layer of Venericardia potapacoensis- _____ 0 8 its name from Calvert County, Md., where, in the including diatoms. The color of the material is Greensand with many scattered specimens The Woodstoek member is further subdivided well-known Calvert Cliffs bordering Chesapeake bluish green to grayish brown and buff. Fossil of Venericardia potapacoensis __...____-_ 3 0 into two zones distinguished by characteristic Bay, its typical characters are well shown. The remains, although abundant through the entire Line of concretions __-_____-_-_,--__---_--- 0 6 Glauconitic clay with Venericardia pota­ fossils. These zones are described in the, above- formation seems to correspond approximately with member, are particularly numerous in two prom­ pacoensis !._.. __.._. ______4 0 mentioned report on the Maryland Eocene, which the horizon at Petersburg, Va. inent beds, from 30 to 35 feet apart, in the Calvert Dark greensand _.....-__._--_i_--_---_--_- 5 0 Layer packed with shells of Venericardia | also contains a full list of the fossils which charac- I Thickness. The full thickness of the Calvert Cliffs. These marls vary in thickness from 4^ to potapacoensis------~------1 6 I terize the member. formation has been nowhere actually observed 13 feet. They may be easily traced along the Cal­ Argillaceous greensand____----__------1 0 along the line of outcrop. The formation has vert Cliffs from Chesapeake Beach to a point 2 Line of concretions---_-._-_--__------0 6 MIOCENE SERIES. been diagonally truncated by the Choptank, so miles below Governor Run. At Chesapeake Beach Argillaceous greensand.-..____ _..._...... ,_ 3 0 CHESAPEAKE GROUP. Greensand with Venericardia potapacoen­ that in the region of Davidsonville it shows a they lie high up in the cliffs and toward the south sis _.._----___._.-_-_-.._--___--..-_----...._- 1 0 CALVERT FORMATION. Dark glauconitic clay ...___._-.._...... _ 3 0 thickness of only about 50 feet. The Choptank they pass gradually downward beneath the surface Layer of shells of Venericardia potapaco- Areal distribution. The Calvert is by far the and younger formations lie above it unconform- of the water. Along Patuxent River the Plum ensis -----.------.-...--...---- 0 4 j most extensive formation in the Patuxent quad- ably. Fortunately, a reliable well record at Cris- Point marls are not exposed so extensively as in Dark clay with much glauconite. | rangle. Although it is largely covered with field, Somerset County, exhibits the entire thick­ the Calvert Cliffs, but they are visible at intervals 74 6 Lafayette and Columbia gravels, yet stream erosion ness of Miocene strata. In this well the Calvert from the cliffs below Lower Marlboro southward Paleontologic character. A great many fossils has cut down to it in so many places that its dis- formation is apparently about 300 feet thick. As to Ben Creek, in Calvert County. On the west are to be seen in the outcrops of the Nanjemoy tribution is very well known. It outcrops in this well is located in the extreme southern portion bank of the river they may be seen here and there formation along South and Patuxent rivers, along nearly every stream-cutting throughout the south­ of the State and far down the dip, the data prob­ from a point opposite Lower Marlboro downstream Piscataway, Mattawoman, and Nanjemoy creeks in ern half of the quadrangle and is represented by ably indicate a rapid thickening of this formation to a point 1^ miles below Forest Wharf, in the Maryland, and along Potomac and Aquia creeks outliers well up on the divides over a large portion as it passes to the southeast toward the ocean. At Nomini quadrangle. in Virginia. An idea of the abundance of these of the northern half. In its larger distribution it Chesapeake Beach, on the bay shore in Calvert West of the Patuxent quadrangle, along Potomac fossils may be obtained by examining the forego­ extends from Virginia northeastward across Mary­ County, a well which begins in the Calvert forma­ River, the banks are usually very low and com­ ing section. The fossils of the Nanjemoy forma­ land and Delaware into New Jersey. It has by tion a little above tide passes out of it and into the posed of Columbia sand and gravel. In conse­ tion have been described and illustrated in the far the most extensive development of all of the Eocene at a depth of 60 feet; at Centerville it is quence of this the Plum Point marls are exposed report on the Eocene issued by the Maryland Geo­ Cretaceous and Tertiary formations in this region. found at a depth of 81 feet and is 65 feet thick; at but few places. On the Maryland side of the logical Survey. This statement might perhaps be extended to at Crisfield the formation lies 465 feet below the river they may be seen in the low cliffs at the Name and correlation. The formation receives apply to the entire Middle Atlantic Coastal Plain, surface. mouth of Chaptico Bay, and on the Virginia side a its name from Nanjemoy Creek, one of the tribu­ although not enough detailed work has been done Straiigraphic relations. Near the Maryland- considerable thickness of the marls is exposed along taries of Potomac River in Maryland, in whose south of Potomac River to show which Miocene Delaware border the Calvert rests unconformably the entire length of the Nomini Cliffs. When fresh, valley deposits belonging to this horizon are char­ members are best developed in Virginia. upon one jof the Cretaceous formations (Rancocas). the Plum Point marls and the Fairhaven diatoma­ acteristically developed. This name was proposed Lithologic character.- The materials constituting Farther southwest it overlies the Aquia forma­ ceous earth do not differ much in appearance. The by Clark and Martin in 1901 (Eocene, Maryland the Calvert formation consist of blue, drab, and tion, and in southern Maryland it lies uncon­ thickness of the marls increases constantly down Geol. Survey, p. 64). In correlating the Nanje­ yellow clay, yellow to gray sand, gray to white formably upon the Nanjemoy, a relationship which the dip. This member is subdivided into 12 zones, moy formation these authors remark as follows diatomaceous earth, and calcareous marl. Between shows the gradual transgression of the Miocene which are distinguished by the lithologic character (op. cit., p. 89): these all gradations exist. , The diatomaceous earth deposits south westward. In this quadrangle it of the materials and by characteristic fossils. gradually passes into fine sand by the increase of lies unconformably upon the Nanjemoy, Aquia, | The only conclusion that can be drawn is that the arenaceous material, or into a clay by the addition CHOPTANK FORMATION. Nanjemoy of Maryland represents such portion of the and Matawan formations and is overlain uncon­ Chickasawan (Wilcox or "Lignitic") as lies above that of argillaceous matter. In a similar way a sand formably by deposits belonging to the Lafayette | Areal distribution. The Choptank formation is represented by the Aquia, while the occurrence of the deposit with little or no clay grades over into a and Pleistocene. The strike of the Calvert for­ confined to the southern portion of the Patuxent highly characteristic species, Ostrea sellceformis, in the deposit of clay in which the presence of sand can mation is from northeast to southwest, and it dips quadrangle. It is exposed along the bay shore IsTanjemoy stage in Maryland, although not so numer­ not be .detected. Notwithstanding this variety toward the southeast at the rate of about 11 feet to south of Plum Point, in the valley of Patuxent ously or typically represented as in the still higher of materials a certain sequence of deposits is com­ the mile. River and its tributaries south of Mill Creek, and strata in central and southern Virginia, points to the monly observed; the basal portions of the forma­ Subdivisions. The Calvert formation has been possible Lower Claibornian age of the highest beds of in the headwaters of Zekiah Swamp. In Calvert the Maryland Eocene. tion consist largely of diatomaceous earth, while divided into two members, known as the Fairhaven County it may be found in a long line of outcrops the upper portions are composed chiefly of sand, diatomaceous earth and the Plum Point marls. extending from the hilltops just west of Herring According to Dall the Nanjemoy represents a clays, and marls. This difference in materials has These are more fully described in the above- Bay to Patuxent River, but west of the Patuxent part of the Suessonian of Europe. led to a subdivision of the formation into two mentioned report on the Miocene of Maryland. it is almost completely obscured by younger depos­ Thickness. The Nanjemoy is about 100 feet members^ which are described below. The Fairhaven diatomaceous earth lies at the its. The boundaries of the Choptank formation thick in the Patuxent quadrangle and thickens Extensive and excellent exposures can be seen base of the formation and is characterized by the in Calvert County are better known than in any gradually toward the east. along the bay shore from Herring Bay southward presence of a large proportion of diatoms embedded other portion of southern Maryland, but west of Stratigraphic relations. The Nanjemoy overlies and also at Hollins Cliff, Lyons Creek, and other in a very finely divided quartz matrix. Calcareous the Patuxent have been determined more by cal­ the Aquia conformably, but is overlain unconform- localities on Patuxent River and its tributaries. material is present in this bed in only very small culation than by observation. They are believed, ably by the Miocene, and in some places along The following section was measured on the bay amounts. Besides diatoms, there are other Mio­ however, to be approximately correct and are fixed the line of outcrop by deposits belonging to the shore 1 mile north of Plum Point: cene fossils, usually in the form of casts, and as accurately as present knowledge warrants. In Lafayette and the Pleistocene. The formation has organic remains reworked from the underlying its broader relations the formation extends from a northeast-southwest strike and dips toward the Section l mile north of Plum Point, Md. Eocene beds. The name for this member is Virginia northwestward across Maryland and Del­ southeast at an average rate of about 12^ feet to PLEISTOCENE: - Ft. in. derived from Fairhaven, Anne Arundel County, aware into New Jersey, where it has an extensive the mile. Yellowish sandy loam .______.__.__._.___ 7 0 MIOCENE (Calvert): where the beds are well developed. development. Subdivisions. This formation, like the Aquia, Yellowish sandy clay..______.__..__._____._ 19 0 The contact of the diatomaceous earth with the Lithologic character. The materials composing is subdivided into two members or substages, known Yellowish sand carrying Isocardia fra- Eocene beds lies about 2 feet beneath a band of the Choptank formation are extremely variable. terna ______7 0 as the Potapaco and Woodstock. Bluish and brownish sandy clay______25 0 sandstone from 4 to 8 inches thick, which carries They consist of fine yellow quartz sand, bluish- The Potapaco member is so called from the early Brownish sand- -____------__-___.______4 6 casts of Pecten humphreysii and other Miocene fos­ green sandy clay, slate-colored clay, and, at some name of Port Tobacco (a corruption of the word Bluish clay grading downward into brown sand.. _...... _...... _ ...... _._ 10 6 sils. Above this sandstone is the diatomaceous places, ledges of indurated rock. In addition to Potapaco) Creek, one of the Maryland tributaries Yellowish-brown sandy clay bearing the earth proper. This bed, which is about 20 feet these materials, abundant fossil remains are dis- 7 seminated throughout the formation. The sandy apeake Bay, the outcrop is very sinuous and the thickness or extent. The sand usually serves as feet. The maximum thickness of the Lafayette in phase is well shown in the Calvert Cliffs from strike appears to change locally. the matrix for the gravels or else is intimately this quadrangle probably does not much exceed 40 Parker Creek southward to Point of Rocks, a The dip does not seem to be constant throughout mixed with the loam. feet. short distance beyond the borders of the Patuxent the extent of the formation. In Calvert County, Throughout the quadrangle the Lafayette is /Stratigraphic relations. A very marked uncon­ quadrangle. The sandy clay and clayey members where the Choptank is best exposed, the northern capped by a deposit of loam varying in thickness formity separates the Lafayette from all underlying may be seen in the same cliffs near Point of Hocks portion of the outcrop, down to Parker Creek, from a few inches to 10 feet or more, with an formations. In one place or another within the and farther south. The formation is best exposed seems to lie almost horizontal; but farther south average of about 5 feet. Near Washington this Coastal Plain province it overlies almost every older alonff. the bav shore south of Parker Creek. The the formation at its base dips southward at the loam contains considerable iron and has here and formation represented in the region, and thin rem­ <-._* V following section is typical: rate of about 10 feet to the mile, so that toward the there a decided orange color. To the east and nants are present in many places on the eastern south it occurs at lower and lower levels until in south this color becomes much less pronounced. borders of the Piedmont Plateau. In the Patuxent Section one-half mile south of Parker Creek, Maryland. the southern portion of its area it is found in river In many places the loam resembles the loess of the quadrangle it rests mostly upon the Calvert and PLEISTOCENE : , Ft. in. upper Mississippi Valley in color and also in texture. Choptank formations and is, in the main, a surface Eeddish sandy loam ______2 0 bottoms and finally disappears beneath tide. The MIOCENE : best place to examine the dip of this formation is On the broad Lafayette plain in the southwestern deposit, although locally it in all probability dips Choptank along the Calvert Cliffs between Parker Creek part of the quadrangle the loam shows a very pro­ beneath beds of Pleistocene age. Reddish sand__--__-_..______-.___ 2 0 and Point of Rocks. Here an almost unbroken nounced mottling of drab and brick-red. This is Reddish sandy clay containing Jialanus QUATEENAEY SYSTEM. concavus, Corbula idonea, Astarte exposure of the Choptank may be seen dipping particularly noticeable when the material is wet. thisphila, Pecten madisonius, Venus gradually toward the southeast. It is seen in numerous road cuts, especially west PLEISTOCENE SERIES. campechiensis var. cuneata, Dosinia COLUMBIA GROUP. acetal)ulum, Cardium laqueatum, Area Subdivisions. The Choptank formation is sub­ of Brandywine. The Lafayette loam is in some staminea, etc. ______14 0 divided into five zones, which are distinguished places highly argillaceous, in others decidedly GENERAL STATEMENT. Yellowish sandy clay containing fossil casts___.______.___ 20 0 from one another by the character of material and arenaceous. As a general rule, it is of very fine The Pleistocene formations of the Atlantic Yellow sand containing Ecpliora quad- the fossils they contain. These zones, together texture. Although the loam capping is relatively Coastal Plain are united under the name Columbia ricostata, Turritella plebeia, Panopea americana, Corbula idonea, C. cune­ with their fossil contents, have been fully described free from bands of gravel, they are not entirely group. They have many characteristics in com­ ata, Metis biplicata, Macrocallista in the State report on the Miocene of Maryland. absent. Single pebbles are not uncommon in the mon, owing to their similar origin. They consist marylandica, Venus mercenaria, V. loam and locally there are well-defined beds of of gravel, sands, and loam which are stratigraphi- campechiensis var cuneata, Dosinia VJLIOC'KXTC (?) SETCIES. acetabulum, Isocardia fraterna, Car­ gravel and sand. The following section, taken 1|- cally younger than the Lafayette formation. The dium laqueatum, Crassatellites, turgi- LAFAYETTE FORMATION. miles southeast of Piscataway, makes these relations Columbia group comprises three formations, the dulus, Astarte thispTiila, Pecten coccy- clearer: melus, P. madisonius, Melina maxil- Areal distribution. The latest Tertiary formation Sunderland, Wicomico, and Talbot, all of which lata, Area staminea, etc.______"6 0 of this portion of the Atlantic Coastal Plain is Section 11 miles southeast of Piscataway, Md. are represented in this region. They appear as the Calvert known as the Lafayette, and is probably of Plio­ facings of different plains or terraces, possessing Bluish clay __-___-_.______9 0 Feet. Brownish sandy clay containing Isocar- cene age. It forms the surface cover over the Pine grayish-yellow loam______5 very definite physiographic relations (see fig. 2), dia fraterna--,..- ______4 0 southwestern portion of the Patuxent quadrangle. Medium-coarse gravel in a matrix of gray sand______4 as described under the heading "Topographic Bluish sandy clay ______10 6 Yellow cross-bedded sand______8 Brownish sandy clay carrying Evplwra At one time, however, it probably formed a mantle Unassorted gravel mixed with gray sand ______5 features" (p. 2). ,. . qnadricostata var. umbilicata, Venus over the entire area, for outliers are found north of On purely lithologic grounds it is impossible to 17 mercenaria, Cytherea staminea- ___. 1 6 Washington and on Marriott Hill east of Patuxent separate the three formations composing the Colum­ Bluish clay ______4 0 River. If such was the case, the Lafayette must Physiographic expression. As described under bia group. The materials of all have been derived 73 0 originally have rested upon the exposed edges of "Topographic features" (p. 2), the deposits of mainly from the older formations which occur in Paleontologic character. Although the Choptank all the earlier formations represented in this region, this formation form a plain of deposition which the immediate vicinity, but include more or less formation is abundantly supplied with fossils, these but erosion has so reduced its area that it is now in is well-developed in many places on the Coastal foreign material brought in by streams from the are for the most part concentrated in two well- contact principally with the Miocene, although in Plain and slopes gradually toward the sea. In the Piedmont Plateau or from the Appalachian region defined beds which seem to be distributed very small areas it rests upon the Patuxent formation vicinity of Anacostia the base of the Lafayette beyond. The deposits of each of these formations extensively through the areas of the deposit. These and the ancient crystalline rocks. The Lafayette plain is at a height of 280 feet and its surface at are extremely varied, their general character chang­ zones, together with many of their characteristic plain is in reality the oldest and highest of a series 300 feet. At Charlotte Hall, 30 miles to the south, ing with that of the underlying formations. Thvis fossils, are shown in the foregoing section. The of five plains which were developed at successively the base is not visible, but the surface lies at an deposits belonging to the same formation may, in fossils are allied to forms now living in lower lati­ lower levels during various epochs ranging in time altitude of about 200 feet. This shows, therefore, different regions, differ far more lithologically than tudes, thus indicating that a somewhat warmer cli­ from Pliocence (?) to Recent. It extends almost a difference of 100 feet in 30 miles, or a surface deposits of two different formations lying in close mate than exists to-day in this region prevailed uninterruptedly from the District of Columbia line slope toward the sea of about 3 feet to the mile. proximity to each other and to the common source during the deposition of the Choptank formation; to the southern boundary of the quadrangle and So slight and gradual a decline in elevation might of most of their material. Cartographic distinc­ it was, however, probably a little cooler than during forms one of the most striking topographic features be attributed to the original attitude of the material tions based on lithologic differences could not fail to the deposition of the Calvert. The fossils of this in this area. It covers the divide between the when it was deposited were it not for the fact that result in hopeless confusion. At some places the formation have recently been fully described and two great river systems and thus becomes the the Sunderland terrace, which wraps about the older Pleistocene deposits are more indurated and illustrated in the two volumes on the Miocene pub­ most conspicuous formation of the region. A base of the Lafayette, has suffered a deformation their pebbles more decomposed than those of the lished by the Maryland Geological Survey. gravel capping on Marriott Hill is the only known of 20 feet, or about 8 inches to the mile, through­ younger formations, but these differences can not Name and correlation. The formation receives outlier of the Lafayette east of Patuxent River in out the same region, and the Wicomico appears be used as criteria for separating the formations, its name from Choptank River, Maryland, because this quadrangle. also to have been affected by a slight tilting. It is inasmuch as loose and indurated, fresh and decom­ of its great development on the northern bank of Lithologic character. The Lafayette formation probable, therefore, that the present slope of the posed materials occur in each of them. that estuary a short distance below Dover Bridge. is composed of gravel, sand, and loam. These Lafayette formation is due both to its original The fossils found in the Pleistocene are far too The formation seems to lie approximately at the materials were so imperfectly sorted by the waves attitude and to subsequent tilting. meager to be of much service in separating the horizon of the James River series of Virginia. of the Lafayette sea that they are now found inter­ Paleontologic character. Fossils are practically deposits in to distinct formations, even though essen­ Thickness. The thickness of the Choptank for­ mingled in varying proportions. Although there lacking in the Lafayette deposits of the Atlantic tial differences between some of them may exist. mation is variable. In the Nomini Cliffs, Virginia, is a rough bipartite division in the deposit as a coast region, none being found in the Patuxent It is the exceptional and not the normal develop­ it is present as a 50-foot bed between the Calvert whole, the gravel occurring in greater abundance area. Pebbles containing Paleozoic fossils are ment of the formations that has rendered the formation below and the St. Marys formation above. at the base and« the sand and loam at the top of the present in the formation at many places throughr preservation of fossils possible. These consist This exposure shows a greater thickness than any formation, yet these elements are mixed together in out the district, but are of importance only because principally of fossil plants that were preserved in other known. In the well section at Crisfield, a confusing manner. No particular kind of mate­ they show the source of the materials. In regions bogs, but in a few places about Chesapeake Bay mentioned in connection with the description of rial is confined to any definite stratum, but all far to the south some fossil plants and animals of local Pleistocene deposits contain great numbers of the Calvert formation, the Choptank is more than kinds may occur anywhere throughout the section. Lafayette age have been reported by McGee, but marine and estuarme mollusks. 100 feet thick, so that, like the Calvert, it thickens Irregular beds or lenses of loam, sand, or gravel very little is known concerning them. The Columbia group, as may be readily seen, is as it passes down the dip. also occur and are exposed in many places through­ Name and correlation. The name Lafayette was not a physiographic unit. The formations occupy Stratigraphic relations. The Choptank forma­ out this quadrangle. The gravels are considerably proposed by Hilgard in 1891 (Am. Geologist, wave-built terraces or plains separated by wave-cut tion lies unconformably upon the Calvert formation. decayed and are usually rather small, but in the vol. 8, pp. 129-131) to replace the term Orange escarpments, their mode of occurrence indicating The unconformity is in the nature of an overlap, vicinity of Washington they become very coarse sand, used in Tennessee and Mississippi, and the different periods of deposition. At the bases of but is not easily discernible even where the contact and are embedded in a coarse, compact sand or term Appomattox, which has been applied to the many of the escarpments the underlying Cretaceous is visible. The best place to observe the uncon­ very stiff, clayey loam. The appearance of the deposits of the Atlantic coast. The name is derived and Tertiary formations are exposed. The highest formity is in the portion of the Calvert Cliffs just gravels also changes from place to place; near from Lafayette County, Miss., a region where the terrace is occupied by the oldest deposit, the Sun­ below the mouth of Parker Creek. Even here it Washington they are almost invariably covered formation is well developed. The exact correlation derland; while the lowest is covered with Talbot can not be seen from the beach, but is visible from with a dark-brown ferruginous coating, but farther of the formation has not been definitely settled, as materials. a boat a short distance from the shore. This south the amount of iron decreases considerably its meager fauna and flora have furnished little At almost every place where good sections of unconformity is also proved by the fact that at the and the coating of iron oxide is practically absent. clue to its age. It overlies Miocene deposits uncon­ Pleistocene materials are exposed the deposit from above-mentioned locality the fossiliferous bed which The heterogeneous character of the material fur­ formably and in turn is overlain by Pleistocene base to top seems to be a unit. At some places, lies lowest in the Choptank formation rests upon nishes evidence of the varied sources from which materials. Its general character, firmly indurated however, certain layers or beds are sharply sepa­ the Calvert, while at Mount Harmony and farther it has been obtained. Pebbles of quartz and crys­ layers, and occasional greatly decomposed pebbles rated from the underlying beds by irregular lines north the upper fossiliferous bed of the Choptank talline rocks indicate the Piedmont as the source; suggest a formation much older than any known of unconformity. Some of these breaks disappear rests upon the Calvert formation. How far this broken iron crusts were derived from the Paleozoic Pleistocence deposit of the province, and hence fur­ within short distances, showing clearly that they unconformity continues down the dip after the beds formations farther west; and finally, decayed blocks nish evidence for a provisional reference to the are only local phenomena in the same formation, disappear from view is not known, as the data from of Newark sandstone are occasionally observed. Pliocene. the result of contemporaneous erosion by shifting well records are too meager to permit any conclu­ While all of these various materials are present, Thickness. The thickness of the Lafayette is shallow-water currents. Whether all these breaks sion to be drawn from them. Above the Choptank the gravels are composed principally of quartz. somewhat variable. In its north westernmost expo­ would thus disappear if sufficient exposures occurred is the St. Marys formation, which is not represented Sand forms a rather unimportant part of the sures the formation shows a thickness of 3 to 10 to permit the determination of their true nature is in this quadrangle. Lafayette deposits. Such as is present seems to feet, the amount increasing somewhat toward the not known. An additional fact which indicates The strike of the Choptank formation is in gen­ have been derived mainly from the Potomac beds. southeast. Over the broad plain in the vicinity of the contemporaneous erosive origin of these uncon­ eral from northeast to southwest; but as a result of Lenses of sand occur at many places in the gravel Brandywine the Calvert, which is the next subja­ formities is that in closely adjoining regions they erosion, particularly on the Western Shore of Ches- deposits, but do not commonly form beds of great cent formation, is reached at a depth of about 28 seern to have no relation to one another. Inasmuch Patuxent. 8 as the Pleistocene formations lie in a nearly hori­ grounds of St. Elizabeth's Asylum was obtained WICOMICO FORMATION. ing these irregularities the formation as a whole zontal plane it would be possible to connect these from beds of consolidated Sunderland deposits. Areal distribution. The next younger formation occupies an approximately horizontal position, with separation lines if they were subaerial unconformi­ Many of the pebbles of the Sunderland are much of the Pleistocene division is the Wicomico. Like a slight southeasterly dip. The average thickness of ties due to an interval of erosion. In the absence decayed, but in general they show less decomposi­ the Sunderland, it was deposited on a terrace or the formation in this quadrangle is about 20 feet. of any definite evidence that these lines are strati- tion than the Lafayette gravels. , plain. It lies topographically lower than the Sun­ Stratigraphic relations. In this quadrangle the graphic breaks separating two formations, they have Physiographic expression. The Sunderland de­ derland, wraps around it like a border, and extends Wicomico overlies unconformably the granite-gneiss v ,- been disregarded. Yet it is not improbable that in posits occupy and form the Sunderland plain up the principal stream estuaries which penetrate it. and the various formations of Jurassic (?), Creta­ some places the waves of the advancing sea in Sun- mentioned in the discussion of topography (p. 2). In the Patuxent quadrangle the Wicomico forma­ ceous, and Tertiary age. It is in many places in deiiand, Wicomico, and Talbot time did not entirely This plain is separated from the Lafayette terrace tion is distributed in the stream valleys through the contact with the Sunderland on the one hand and remove the beds of each preceding "period of depo­ by a well-defined scarp. This scarp has suffered entire area, and is especially well developed in the with the Talbot on the other. It is probable that sition over the area covered by the sea in its next considerable modification since its formation, and basin of Patuxent River. the Sunderland formation extends locally somewhat transgression. Especially would materials laid where it was not prominent it has been transformed Lithologic character. The materials which con­ below the Sunderland-Wicomico scarp and may down in depressions be likely to persist as isolated to a gently rolling surface or has been lost alto­ stitute the Wicomico formation are similar to those run out beneath and underlie the edge of the . remnants which later were covered by the next gether. At Charlotte Hall, just beyond the south­ "Found in the Sunderland in fact, many of them Wicomico formation where the two are in contact. mantle of Pleistocene deposits. If this is the case ern margin of the quadrangle, this scarp is have been derived from that formation. They In such places this contact between the Wicomico each formation from the Lafayette to the Wicomico preserved in nearly its original sharpness. It is consist of clay, peat, sand, gravel, and ice-borne and Sunderland would be an unconformity. is probably represented by fragmentary deposits also visible south of Bryantown and north of bowlders. The distribution of these materials is beneath the later Pleistocene formations. Thus in Aquasco. In all these localities the original scarp similar to that of those in the Sunderland in that TA.LBOT FORMATION. certain sections the lower portions may represent was low, not exceeding 20 feet in height, but at they grade one into another both vertically and Areal distribution. The Talbot formation is an earlier period of deposition than that of the Congress Heights, south : of Anacostia River, the horizontally, the coarser materials preponderating extensively developed within the Patuxent quad- , overlying beds. In regions where pre-Quaternary scarp separating the Lafayette and Sunderland sur­ at the base of the formation and the finer materials rangle. It occurs as a terrace of varying width materials are not exposed at the bases of the escarp­ faces is over 60 feet high and is the finest and best toward the top. In the northeast corner of the extending from the Wicomico-Talbot scarp out to ments each Pleistocene formation near its inner defined of all the ancient escarpments of this por­ quadrangle, in the vicinity of Annapolis, large the edge of the surrounding waters. It is well margin probably rests upon the attenuated edge of tion of the Coastal Plain. At Congress Heights quantities of Eocene materials have been reworked distributed throughout the quadrangle, bordering w" the next younger formation. Inasmuch as litho- the surface of the Lafayette plain lies at an altitude in the Wicomico formation. At some places the the various estuaries and streams. Its most contin­ logic differences' afford insufficient criteria for sepa­ of about 260 feet. From this height a steep slope materials are very much decayed, as in the Sun­ uous and unbroken areas are situated in the north­ rating these late deposits, and as sections are not descends, cutting through the Lafayette and under­ derland. eastern portion of the quadrangle between South , nttmerous enough to furnish distinctions between lying Miocene beds, to the 200-foot contour, where In the Potomac Valley near Washington bowl­ River and Herring Bay, in the valley .of Patuxent lo'cal interformational unconformities and wide­ the broad Sunderland plain abuts against the scarp ders carrying glacial strias have been found in the River from Hollins Cliff southward to the quad­ spread unconformities resulting from an erosion and slopes gently and imperfectly away from it. Wicomico formation. The great size of these rangle boundary, and in the valley of Anacostia interval, the whole mantle of Pleistocene materials The Sunderland formation is also usually separated bowlders, however, and their occurrence with much River. occurring at any one locality is referred to the from the Wicomico formation by a well-pronounced finer materials furnish evidence of their transpor­ Lithologic character. The materials which cQm- same formation. The Sunderland is described as scarp; this is discussed in the section following, tation by floating ice. pose the Talbot formation consist of clay, pe^t, overlying the Jurassic (?), Cretaceous, and Ter­ which is devoted to the Wicomico. The amount of loam present in the Wicomico is sand, gravel, and ice-borne .bowlders. As in t^e tiary deposits and as extending from the base of As already stated, the Sunderland plain stands exceedingly variable. Wherever the loam cap is Sunderland and Wicomiei) deposits, these mate­ the Lafayette-Sunderland escarpment to the base at a height of 200 feet near Anacostia and of 180 well developed the roads are very firm and the land rials grade into each other both vertically and of the Sunderland-Wicomico escarpment. The few feet at Charlotte Hall, 30 miles to the southeast. is.suitable for the production of grass and grain; horizontally, and the formation exhibits the same^ deposits of Lafayette materials which may possibly The surface of this plain thus slopes southeastward but where the loam is present in small quantities tendency toward a bipartite division, with the underlie the Sunderland are disregarded because at the rate of 8 inches to the mile. It also slopes or absent altogether the roads are apt to be sandy. coarser materials beneath and ,the finer materials / they are unrecognizable. Similarly the Wicomico gently toward the larger estuaries. Physiographic expression. The Wicomico forma­ above. There is, on the whole, much less decayed is described as including all the gravels, sands, Paleontologic character. The only locality within tion is developed in a 'terrace which is described in material in the Talbot than in the two preceding and clays overlying the pre-Lafayette deposits this quadrangle at which fossils have been discov­ the section headed ''Topographic features" (p. 2) formations and ,as a result the formation has a> and extending from the base of the Sunderland- ered in the Sunderland formation is along the as the Wicomico plain. This plain is separated much younger appearance than the other .Pleisto­ Wicomico escarpment to the base of the Wicomico- Chesapeake Beach Railroad, in a deep cut between from the Sunderland terrace, which lies above.it, cene deposits. Talbot escarpment. Perhaps, however, materials Wilson and Owings stations. At this place a by a scarp, usually above 20 feet in height, that is In the western portion of the quadrangle, in the of Lafayette and of Sunderland age may underlie plant bed occurs at the base of the deposit. It one of the most constant and striking topographic vicinity of Washington and Anacostia, the Talbot the Wicomico in places. In like manner the Tal­ consists of a stratum of black clay about 3 feet in features in the quadrangle. The Wicomico plain beds contain many large bowlders which have been bot may here and there rest upon deposits of the thickness, in which are numerous small lignitized is in turn in most places separated by an escarp­ carried by icebergs and dropped in deposits of much Lafayette, Sunderland, and Wicomico. stems. No good plant remains have,been found, ment from the Talbot terrace, which wraps around finer material. Some of these bowlders show their yet the presence of vegetable inatter through the it at a lower elevation. From the Sunderland- glacial origin in that they have been planed by ^Kea SUNDERLAjSTD FORMATION. entire thickness of clay is indicated by the Wicomico scarp line the surface of the Wicomico wearing action of the ice and bear glacial strife., Areal distribution. The Sunderland formation black color of the material, due to carbonaceous formation slopes away gently toward tlie surround­ Cross stratification is very common in the Talbot, is developed as a terrace or plain which occupies matter. ing waters in the manner of a wave-built terrace. deposits. One of the best exposures of this struc­ the top of the divide separating Chesapeake Bay Name and correlation. The formation has been In the extreme northern portion of the quadrangle ture can be seen in a shallow cut along the Chesa­ from Patuxent River and the sides of the divide, named from the little village of Sunderland, Cal- the surface of the Wicomico, at the base of this peake Beach Railroad about one-fourth mile from-. below the Lafayette formation, between Patuxent vert County, near which it is typically developed. escarpment, lies at an elevation of about 100 feet, Patuxent River. Another good exposure of cross and Potomac rivers. Since its deposition it has The name'was first applied to the formation by while in the southern portion of the quadrangle stratification in the Talbot occurs just north of suffered more erosion than either of the two G. B. Shattuck in May, 1901 (Johns Hopkins the elevation of the corresponding surface is about Lyons Creek, in Anne Arundel, County. The fol­ younger formations, but enough of it still remains Univ. Circ. No. 152). The Sunderland corresponds 90 or 95 feet, indicating a very gentle slope toward lowing section was taken on the banks of Anacostia. within the area to make its mapping possible and approximately with the Earlier Columbia of McGee the southeast. Since the Wicomico was deposited River, near Washington: to establish its relations to the other deposits. The and with parts of the Bridgeton and Pensauken of it has,'been subjected to considerable erosion and its Section on west side of Anacostia River south of Pennsyl- - surface of the Sunderland plain varies in altitude Salisbury. Its Pleistocene age is indicated by the originally level surface has been transformed, at vania avenue, Washington, D. C. from 200 feet in the northern portion of the modern appearance of its plant remains and by least along the waterways, into a gently rolling one. I Ft. In. - quadrangle to 180 feet in the southern portion. its relation to the next younger formation, the Paleontologic character. About 1 mile southeast Sandy loam, light yellow to brown in color.._ 3 (5 Fine yellow sand with here and there isolated Throughout this tract the Original surface of the Wicomico, in which bowlders bearing glacial striae of Queen Anne (Hardesty) there is a plant bed pebbles or thin lenses of gravel 4 to 6 inches formation was nearly level, but the streams which have been found. within and just at the base of the Wicomico forma­ thick; gravel up to 6 inches in diameter ___ 7 0 Mass of gravel of all sizes, unstratified, some now flow across it have locally produced a gently Thickness. Although the materials of the Sun­ tion. Here, at an elevation of 30 feet above the several feet in'diameter; yellow sandy ma­ rolling surface. derland lie at varying elevations above sea level in stream, there is a deposit of carbonaceous material trix; striae on gravels; materials generally ,' Lithologic character. The materials which com­ the Patuxent quadrangle, the thickness of the for­ about 20 feet thick. About 1^ feet of this is com­ fresh in appearance; a few small lenses of yellow sand free from gravel. In places pose the Sunderland formation consist of clay, mation is not great at any point. That the depos­ posed principally of peat. The leaf impressions iron crusts have formed in the sand and s&nd, gravel, and ice-borne bowlders. As explained its were laid down on a sloping and dissected'plain are mainly of grasses and stems, but some insect gravel, cementing them together. Amount exposed -_--_--___------___---_-_-__-._,___ 11 0 afbove, these materials as a rule do not lie in well- is proved by many well records and observations remains and .beetle-wing covers are also present. defined beds, but grade into each other both verti­ which show that the surface of the underlying for­ Name and correlation. This formation receives 21 6 cally and horizontally. The coarser materials, with mations rises in passing from the stream valleys to its name from Wicomico River, in southern Mary­ Physiographic expression. The Talbot forma­ the exception of the ice-borne bowlders, have in the divides. Consequently, the thickness of the land. The name was proposed by G. B. Shattuck tion is developed as a terrace capping, forming the main a cross-bedded structure, but the clays and Sunderland can not be determined by the elevation in May, 1901 (Johns Hopkins Univ. Circ. No. the Talbot plain described under the heading finer material are either developed in lenses or hor­ of the deposits, but the evidence furnished by 152). The Wicomico represents the upper part of "Topographic features" (p. 2). It wraps around izontally stratified. The erratic ice-borne blocks excavations and well records on the stream divides the Later Columbia of McGee and Darton and a the lower margin of the Wicomico terrace, from are scattered through the formation and may occur shows that the formation probably has an average part of the Pensauken of Salisbury. The presence which it is separated in most 1 places by a, low in the gravel, sand, or loam. The coarser material thickness of about 35 feet. of ice-borne -bowlders furnishes evidence for its escarpment. From the base of the WicomicO- throughout the formation tends to occupy the lower /Stratigraphic relations. Throughout the Coastal contemporaneity with the ice invasion, although Talbot scarp, which is at an elevation of 40 to 45 portions and the finer the upper portions, but the Plain the Sunderland overlies unconformably vari­ the particular drift sheet with which the formation feet, the surface of the Talbot formation slopes transition from one to the other is not marked by ous formations of Jurassic (?), Cretaceous, and should be correlated has not yet been determined. gently toward the surrounding waters. This sur­ an abrupt change, and at many places the coarse Tertiary age. In the Patuxent quadrangle it lies Thickness. The thickness of the Wicomico for­ face has chiefly, if not entirely, the initial slope materials are present in the surface loam and the unconformably upon the Aquia, Nanjemoy, Cal- mation is not at all uniform, owing to the uneven which was imparted to it during its period of finer materials are below, in the gravel. As a vert, and Choptank formations. It is not improb­ surface upon which it was deposited. . It ranges deposition. Usually this terrace is terminated by whole the material is coarser on the western side able that the edges of the Lafayette formation from a few feet to 50 feet or more. The formation a low scarp cut by the waves of Chesapeake Bay of the quadrangle, in the Potomac basin, than extend beneath part of the Sunderland deposits, dips down into the valleys and rises on the divides, or its estuaries, but locally it slopes gently to the elsewhere. In the vicinity of Congress Heights, although this can not be determined because of the so that its thickness is not so great as might be water's edge. The Talbot formation has suffered the gravels of the Sunderland are rather commonly absence of any definite line denoting a stratigraphic supposed from the fact that the base is in many less erosion than either the Sunderland or the cemented by ferruginous material. The ferrugi­ break and because of the similarity of the materials places as low as 40 feet while the surface rises Wicomico. It has been elevated above the water nous conglomerate used in the wall about the of the two formations. locally to 100 feet above sea level. Notwithstand­ for so short a time that such streams as have found 9 their way across its surface have not been able to the granite gneiss, the only crystalline rock of the a much more extensive development in the regions of the Potomac group. This formation, on the change materially its original level character. quadrangle, yielding to deformation took place beyond its borders. If study were confined to the evidence furnished by fossil plants and by its Paleontologic character. In the Maryland por­ along numerous planes cutting the rock. Along area of the quadrangle alone many of the conclu­ position beneath the Arundel, which contains tion of the Coastal Plain there are a number of these there was motion of one part past another sions drawn from such investigations might be vertebrate fossils of doubtful Jurassic age, is localities at which fossil remains of either plants attended by the growth of new minerals out of the unsatisfactory and erroneous. The geologic history questionably referred to that period. It indi­ or animals or both occur in the Talbot deposits. broken materials of the old. The new minerals of the quadrangle, which is here outlined, has been cates a submergence of the Coastal Plain in In this quadrangle the most conspicuous of these crystallized nearly parallel to one another and to the based on work done not only in this area but also this region of sufficient extent to cover the is near Fairhaven, Anne Arundel County, where planes of motion and produced the schistosity which throughout the North Atlantic Coastal Plain from whole area with shallow water. The cross-bed­ the formation contains a lens of drab-colored clay characterizes the granite gneiss of this region. The Raritan Bay to Potomac Kiver and in certain locali­ ded sands and gravels furnish evidence of shift­ bearing plant remains. Near Cornfield Harbor, granite gneiss occurring in the extreme northwest ties in Virginia and the Carolinas. ing currents, as do also the abrupt changes in the at the mouth of Potomac River, the formation corner of the Patuxent quadrangle forms the east­ A study of the geologic history of the Patuxent character of the materials, both horizontally and has yielded a great number of molluscan shells ern part of an anticline whose axis passes through quadrangle 'shows that it has been long and com­ vertically. The presence of numerous land plants representing a varied fauna of marine and brackish- Washington; the axis of the accompanying syncline plicated. This is indicated by the many different in the laminated clays shows the proximity of the water origin. to the east is covered by the Coastal Plain deposits. kinds of strata represented and by the relations land. Name and correlation. Talbot County, Md., The dip of the planes of schistosity is from 60° to which they bear to one another. There are deposits The deposition of the Patuxent formation was where the formation occupies a broad terrace bor­ 90° NW. A fuller statement of the structure of that were formed in fresh or brackish water; others ended by an uplift which brought the region dering numerous estuaries, has furnished the name the Piedmont rocks is given in the Washington that show evidence of their deposition in marine above the water and inaugurated a period of for this formation. It was first given by G. B. folio (No. 70). waters, some in water of shallow depth, others in erosion which persisted long enough to permit Shattuck in 1901 (Johns Hopkins Univ. Circ. No. In striking contrast with the complex structure deep water; while breaks in the conformity of the the removal of a vast amount of material. This 152). The Talbot represents the lower part of the of the Piedmont rocks is the extremely simple different strata indicate that from the time of the was followed by a subsidence in which many of the Later Columbia described by McGee and Darton structure of the Coastal Plain strata. Although formation of the earliest beds down to the present stream valleys, but lately eroded, were occupied and corresponds approximately to the Cape May many unconformities separate the various forma­ day the region has undergone many elevations and for a portion of their courses by bogs and swamps formation of Salisbury. Its Pleistocene age is tions of the Coastal Plain, these are comparatively subsidences. of the Arundel formation. In these marshes there proved by the fossils found at Cornfield Harbor minor unconformities of erosion. Folding of the Pre-Potomac history. In this quadrangle rocks was an extensive development of plant life and in and by its contemporaneity with a part of the ice strata is almost, if not entirely, lacking, and fault­ older than the Jurassic (?) are present only in the them also were deposited iron ores that are now of invasion of the northern portion of the country, ing has not been observed in this quadrangle. The Piedmont Plateau. It is exceedingly difficult to considerable value. After another uplift and inter­ as shown by the numerous ice-borne bowlders numerous uplifts and depressions which the region interpret the past history of the Piedmont region val of erosion the land was again depressed beneath found in its deposits. has experienced have been so uniform over wide for the reason that the whole area has been sub­ sea level. Physical conditions similar to those Thickness. The thickness of the Talbot forma- areas that the only existing evidence of these crustal jected to many great changes which have essen­ which had prevailed during Patuxent time existed tation is extremely variable, ranging from a few movements consists of traces of successive periods tially modified the original materials; yet the during this period of submergence, in which the feet to 40 feet or more. The unevenness of the of erosion and deposition that must have been studies of Williams, Keith, Mathews, Bascom, Patapsco formation was laid down. Dicotyledo­ surface upon which it was deposited has in part produced by alternate uplift and submergence. As and others have revealed many facts concern­ nous plants, which are very rare and primitive in caused this variability. The proximity of certain explained elsewhere, these vertical movements were j ing the original condition of the rocks now structure in the Patuxent deposits, are abundant regions to the mouths of streams during the Talbot sometimes accompanied by tilting, with but slight | occupying this region. Nearly all the rocks in the Patapsco and belong to higher types. This submergence also accounts for the increased thick­ deformation. of the Piedmont are inetamorphic in character. seems to indicate that a long time intervened ness of the formation in such areas. The formations all have a general northeast- j Many of these rocks were originally sedimen­ between the two periods of deposition, during Stratigraphic relations. The Talbot rests uncon- southwest strike and a dip to the southeast. This tary deposits, but in the processes of metamor- which the land flora of the region materially formably, in different portions of the region, upon dip, though variable in amount in the different for­ phism have how lost nearly all traces of their changed. After the deposition of the Patapsco various older formations belonging to the Juras­ mations, agrees in direction with the slope of the original character. Consequently it is scarcely formation the region again became land through sic (?), Cretaceous, or Tertiary systems. It may crystalline floor upon which the Coastal Plain sedi­ possible to explain the conditions under which an upward movement which drained all the pre­ in places rest upon deposits of Lafayette, Simder- ments rest. At some places, particularly in the they were originally deposited. Yet it may be viously existing estuaries and marshes. Erosion land, or Wicomico age, although no positive evi­ Pleistocene formations, the dip is very slight not said that a large portion of the area which the at once became active and the Patapsco surface dence has yet been found to indicate such relations more than a few feet to the mile but in the for- Piedmont metamorphic rocks now occupy was was dissected. A downward land movement again

FIG. 1. Section from "Washington to Patuxent River along line A-A on areal geology map. Qc, Columbia group; Tl, Lafayette formation; Tcv, Calvert formation; Tn, Nanjemoy formation; Ta, Aquia formation; Kmw, Matawan formation; Kma. Magothy formation; Kr, Raritan formation; Kpt, Patapsco formation; Ja, Arundel formation; Jp, Patuxent formation; /Rg, granite gneiss. Horizontal scale, approximately 1 inch = 2 miles. Vertical scale, 10 times horizontal scale. to the older Pleistocene formations. The deposits mations of the Potomac group it is as great as 50 under water at one time, or perhaps many times, submerged the greater portion of the region, leav­ occupy a nearly horizontal position, having only a | to 75 feet to the mile. and received in some places deposits of sand and ing only a very narrow strip of Patapsco deposits slight slope toward Chesapeake Bay and its estuaries..! The pre-Pleistocene formations of the Patuxent mud carried in by streams, while in other places above water. The Raritan formation was next quadrangle constitute a series of overlapping beds beds of limestone were formed. It is not known deposited, under conditions very similar to those KECENT DEPOSITS. with lines of outcrop roughly parallel to the strike. how long this sedimentation continued or how which had existed during the previous submer­ In addition to the four terraces already discussed, j With few exceptions, already described in detail, many breaks took place between successive periods gence. Raritan deposition was terminated by an a fifth is now being formed by the waters of the I each formation dips to the southeast at an angle of deposition. It has been thought by most recent uplift which again converted the entire region into rivers and the waves of the estuaries. This ter­ greater than the slope of the country and disappears workers in the Piedmont region that the rocks there land. A long period elapsed before a resubmer- race is everywhere present along the water's edge, beneath the next younger formation (see fig. 1). include not only representatives of the Archean, to gence, so that the streams were able to effect extending from a few feet above tide to a few feet Thus successively younger beds are encountered which most of the earlier geologists referred them, extensive erosion of the recently formed deposits. below. It is the youngest and topographically the by one who passes from the northwestern to the but of the Cambrian and Ordovician as well. The widespread development of shallow-water lowest of the series. Normally it lies beneath southeastern portion of the quadrangle over the These old rocks have been broken through in deposits, everywhere cross-bedded and extremely and wraps about the margin of the Talbot terrace, upturned edges of the deposits. many different places by sheets and dikes of variable in lithologic character, and the presence from which it is separated by a low scarp that as I The accompanying sketch (fig. 2) shows diagram- igneous material. Thus the Piedmont metamor- throughout these deposits of land plants furnish a rule does not exceed 15 to 20 feet in height. matically the structural and topographic relations phics comprise representatives of both igneous and some evidence that the Potomac sedimentation took Where the Talbot formation is absent, the Recent of the five terrace formations, namely, the Lafay­ sedimentary rocks. The structure of these rocks place not in open ocean waters but in brackish- or terrace may be found at the base of either of the ette, Sunderland, Wicomico, Talbot, and Recent. when first formed was undoubtedly much more ] fresh-water estuaries and marshes that were indi­ other three terraces. In such places, however, the It will be noticed that the four older ones are rep- simple than at present, but they have been repeat- j rectly connected with the ocean, which may have scarp which separates them is higher in proportion j at times locally broken into the area. Some land as the upper terrace is older. Peat, clay, sand, ___ QS _ __., Qw barrier to the east of the present shore line prob­ and gravel make up the formation and these mate­ ably existed and produced these conditions, but its rials are deposited in deltas, flood plains, beaches, position and extent can not be determined. bogs, dunes, bars, spits, and wave-built terraces. FlG. 2. Ideal section showing structure and topographic relations of the several terrace formations. Magothy history. The period during which the Fossils, if the recently buried organic remains can Qr, Recent; Qt, Talbot; Qw, Wicomico; Qs, Sunderland; Tl, Lafayette; Tc, Chesapeake group. Magothy deposits were formed was one of transition be so called, are very common, but consist almost resented as bipartite in character. The landward edly subjected to various processes of metamor- from the estuarine or fresh-water conditions of exclusively of vegetable debris covered by swamp edge of each formation is represented as lapping up phism by which the beds have been folded and Patapsco and Raritan time to the marine condi­ deposits, and of brackish-water animals of living over the seaward edge of the one preceding. This crumpled and the original mineral composition tions under which the Matawan, Monmouth, and species entombed in the muds of Chesapeake Bay sketch indicates the conditions as they would appear has been greatly changed. Rancocas were laid down. The great variability and its estuaries. if typically developed, but here and there the There is no evidence to show a submergence of in the lithologic character of the materials, the lower portions of the scarps are occupied by Mio­ this area during the latter part of the Paleozoic coarseness of the sands and gravels, and the cross- STRUCTURE. cene or older beds, leaving the Pleistocene materials era nor during the Triassic period. It probably bedding all suggest conditions similar to those of The geologic structure of this quadrangle, with confined only to the upper portions of the escarp­ remained as a land mass during most of this time, the preceding periods. On the other hand, the the exception of the small area of crystalline rocks ments. -In such places the next younger terrace furnishing terrigenous materials to the Paleozoic local pockets of glauconitic sand and the presence in its northwest corner, is extremely simple. The deposit does not lap up on the base of the gravels sea to the west and to the Atlantic Ocean far to of marine invertebrates suggest the marine condi­ structure of the crystalline rocks of the Piedmont of the terrace just preceding, but rests unconform- the east. It is of course possible that it may have tions of the late Cretaceous. The probability is Plateau, on the other hand, is very complex. These ably upon the older materials which occupy the been depressed beneath the ocean waters and cov­ that over most of the area where Magothy deposits rocks are tilted at high angles, dislocated by faults, base of the escarpments. ered with sediments many times, but, if so, later are now present Potomac conditions prevailed dur­ and greatly changed from the position in which HISTORICAL GEOLOGY. erosion has removed such deposits from the crys­ ing the greater part of the period and in some they were formed. Folds are abundant, and the talline surface. places perhaps during the whole of it, but that forces of compression have usually so acted as to SEDIMENTARY RECORD. Potomac history. The earliest of the known occasionally, through the breaking down of the squeeze the sides of the folds together until the General statement. Almost all the formations unconsolidated deposits lying upon the floor of land barriers which had kept out the ocean, there beds on each side dip in the same direction. In which occur within the Patuxent quadrangle have crystalline rocks belong to the Patuxent formation were incursions of sea water, bringing in marine Patuxent. 10 forms of life. Thus far there is no evidence that These must have lived in the waters in countless in certain localities. As fast as the waves supplied of the land against which the waves beat. A low such incursions took place anywhere except in New millions, and as they died their siliceous shells fell the material, the shore and bottom currents swept coast line yields a low sea cliff and a high coast Jersey. to the bottom and produced the beds of diatoma- it out to deeper water and deposited it so that the line the reverse, and the one passes into the other At the close of Magothy time the region was ceous or infusorial earth which are so common in basal member of the Sunderland formation, a mix­ as often and as abruptly as the topography changes, uplifted and a period of erosion was inaugurated. the lower part of the Calvert formation. Many ture of clay, sand, and gravel, represents the work so that along the shore of Chesapeake Bay, high During this erosion interval comparatively small Protozoa as well as Mollusca lived in the same of shore currents along the advancing margin of cliffs and low depressions occur in succession. amounts of material were removed. In some places waters and their remains are plentifully distrib­ the Sunderland sea; whereas the upper member, In addition to these features, bars, spits, and it is impossible to establish definitely any strati- uted throughout the deposits. During the Miocene consisting of clay and loam, was deposited by other shore formations of this character are being graphic break between the Magothy and the Mata- epoch the conditions seem to have been favorable quieter currents in deeper water after the shore produced. If the present coast line were elevated wan. This may be because the erosion interval for animal life, as may be inferred from the great line had advanced some distance westward and only slightly, the subaqueous platform which is now in was comparatively short or because the elevation of deposits of shell marl which were then formed. the finer material found its way very far out. Ice- process of building would appear as a well-defined the land above the water was so slight that it did After the deposition of the Calvert formation borne bowlders are also scattered through the for­ terrace of variable width, with a surface either flat not permit the streams to cut channels in the the region was again raised and subjected to erosion mation at all horizons. or gently sloping toward the water. This surface recently formed deposits. for a short period, and then sank once more beneath After the deposition of the Sunderland forma­ would everywhere fringe the shores of the ocean Later Cretaceous history. Not until late Creta­ the sea. The Choptank formation was laid down tion, the country was again elevated above ocean and bay, as well as those of the estuaries. The sea ceous time did a downward movement occur of contemporaneously with the advancing ocean. level and erosion began to tear away the Sunder­ cliff would at first be sharp and easily distinguished, sufficient extent to permit the ocean waters to This formation lies unconformably upon the Cal­ land terrace. This elevation, however, was not of but with the lapse of time the less conspicuous por­ transgress widely over this region. During the vert, and farther north transgresses it. In neigh­ long duration and the country eventually sank tions would gradually yield to the leveling influences Matawan, Monmouth, and Rancocas epochs prob­ boring regions to the south of this quadrangle a below the waves again. At this time the Wicom­ of erosion and might finally disappear altogether. ably all of the quadrangle was depressed beneath third Miocene formation, the St. Marys, was depos­ ico sea repeated the work which had been done by Erosion would also destroy, in large measure, the the ocean waters. The streams from the low-lying ited conformably upon the Choptank at a later the Sunderland sea except that it deposited its continuity of the terrace, but as long as portions of land evidently carried into the ocean at this time period. materials at a lower level and cut its scarp in the it remained intact, the old surface could be recon­ only small amounts of fine sand and mud, which Pliocene (?) history. At the close of the Mio­ Sunderland formation. At this time also there structed and the history of its origin determined. afforded conditions favorable to the production of cene the entire region was uplifted to form land. was a contribution of ice-borne bowlders which PHYSIOGRAPHIC RECORD. glauconite and permitted the accumulation of the Streams at once began to carve valleys on the fea­ were deposited promiscuously over the bottom greensand beds that are so characteristic of the tureless surface. These conditions continued until of the Wicomico sea. These are now found at The history of the development of the topog­ Upper Cretaceous deposits along the Atlantic coast. the country was reduced approximately to a base- many places embedded in the finer material of raphy as it exists to-day is not complicated. The During this time very slight changes took place level, so that the weathered products of the Pied­ the Wicomico formation. topographic features were formed at several differ­ along the continental border, although elevation mont were not carried off by the sluggish streams. At the close of Wicomico time the country was ent periods, during all of which the conditions was probably proceeding slowly, as the Matawan, Then a subsidence occurred which again brought again elevated and eroded, and then lowered to must have been very similar. The physiographic Monmouth, and Rancocas formations are found the region under water. Coincident with the sub­ receive the deposits of the Talbot sea. The geo­ record is merely the history of the development of- outcropping farther and farther to the southeast. sidence there seems to have been a slight elevation logic activities of Talbot time were a repetition of the four plains already described as occupying dif­ After the deposition of the Rancocas formation and tilting of the region west of the shore line. those carried on during Sunderland and Wicomico ferent levels, and of the present drainage channels. upward land movements again caused the shore The heads of the streams were given renewed force, time. The Talbot sea cut its scarp in the Wicom­ The plains of the Patuxent quadrangle are pri­ line to retreat eastward, but to what point is not enabling them to carry down and spread over this ico formation, or in some places removed the marily plains of deposition which, since their for­ definitely known. Farther north, in New Jersey, region large quantities of gravel and sand, derived Wicomico completely and cut into the Sunderland mation, have been more or less modified by the deposition still continued in some places, for the from the Piedmont deposits and the Paleozoic for­ or still older deposits. Deposits were made on its agencies of erosion. Their deposition and subse­ Rancocas is there overlain by another and later mations to the west. terrace, a flat bench at the base of this escarpment. quent elevation to the heights at which they are deposit of Cretaceous age, the Manasquan forma­ The evidence for the source of the material is Ice-borne bowlders are also extremely common in now found indicate merely successive periods of tion. If the Rancocas and Manasquan were ever found in many different pebbles whose origin can the Talbot formation, showing that blocks of ice depression and uplift. The drainage channels formed within the limits of the Patuxent quad­ be traced by their lithologic character or the fossils charged with detritus from the land drifted out and have throughout most of their courses undergone rangle they have either been removed or are con­ they contain. In the vicinity of Washington many deposited their load over the bottom of the Talbot many changes; periods of cutting have been fol­ cealed from view by later formations which have of the gravel deposits contain fossils of Devonian sea. lowed by periods of filling, and the present valleys overlapped them. and Carboniferous age brought from regions beyond Embedded in the Talbot formation at Fairhaven and basins are the results of these opposing forces. Eocene history. At the close of the Cretaceous the Blue Ridge. These fossils show that Potomac there is a lens of drab-colored clay bearing plant Lafayette stage. Within the borders of the period the recently deposited sediments were up­ River had extended its drainage basin westward to remains. The stratigraphic relations of this and Patuxent quadrangle there are evidences of fre­ lifted to form a land mass and sedimentation was those regions. During the submergence beneath similar lenses of clay occurring elsewhere in the quent changes during Cretaceous and early Ter­ succeeded by erosion. In early Tertiary time a the Lafayette sea, conditions were not uniform over Coastal Plain show that they are invariably tiary time which resulted in the deposition of a depression carried most of the region again beneath the entire area, as gravel deposits were forming in unconformable with the underlying formation and succession of formations composed of heterogeneous the waters of the ocean and the Eocene deposits some places at the same time that the clay beds apparently so Avith the overlying sand and loams materials. These changes, however, were to only were formed. The great amount of glauconite pres­ were being deposited in others adjoining. Yet on belonging to the Talbot. This relationship was a very slight extent influential in producing the ent in these formations indicates that the adjacent the whole sedimentation was remarkably uniform very puzzling until it appeared that the apparent present topography, so that in beginning the dis­ land mass must have been low and flat, so that the throughout the area, considering the circumstances unconformity with the Talbot, although in a sense cussion of the physiographic history of the region streams carried in only small amounts of terrige­ under which it took place. Over the former land real, does not, however, represent an appreciable they may be omitted. Toward the close of the nous material. The water in which this was surface a fairly persistent capping of gravel was lapse of time and that, consequently, the clay lenses Tertiary, however, a change in conditions occurred dropped was doubtless only a few hundred fathoms deposited. But land movements were again taking are actually a part of that formation. In brief, the which is clearly shown in the existing topography. deep, as glauconite is not produced at great depths. place slowly. The velocity of the streams was clays carrying plant remains are regarded as lagoon A layer of gravels, sands, and clays was spread The land-derived materials at the beginning of the checked so that gravel could no longer be carried deposits made in ponded stream channels and grad­ over the entire Coastal Plain and along the borders Eocene consisted of small, well-rounded pebbles down except in occasional freshets. Fine sand and ually buried beneath the advancing beach of the of the Piedmont Plateau during the Lafayette sub­ which were deposited in several places in the loam were laid down over the gravel which had Talbot sea. The clays carrying marine and brack­ mergence. These deposits, which, as already stated, region; but later the materials carried consisted been previously deposited. This loam, which is so ish-water organisms are believed to have been at must have been laid down on a rather irregular sur­ of fine sand or clay. Many forms of animal life extensively developed over a large portion of Prince first off-shore deposits made in moderately deep face, formed a thin mantle of materials, ranging existed in these waters and their remains now Georges County, marks the last period of Lafayette water, and later brackish-water deposits, formed from 25 to 50 feet in thickness. When the uplift compose layers of marl several feet in thickness. sedimentation. It marks also the last time that the behind a barrier beach and gradually buried by which terminated Lafayette deposition occurred, a Studies of the fossils found in the Eocene depos­ entire region was submerged beneath the ocean the advance of that beach toward the land. As very even, gently sloping plain extending from the its indicate that there were many changes in the waters. a fuller discussion of this question has been given Piedmont Plateau to the ocean, bordered the conti­ fauna during this time. These changes were prob­ Pleistocene history. At the close of the Pliocene in the St. Marys folio (No. 136) it will not be nent. Across this plain, which was composed of ably influenced to a greater or less extent by varia­ epoch the region was raised again and extensively repeated here. coarse, unconsolidated materials, streams rising in tions in physical environment, yet the character eroded, and was then lowered and received the Recent history. The last event in the geologic the Piedmont gradually extended their courses, of the deposits themselves gives little evidence of deposits which constitute the first member of the history of the region was a downward movement, while new ones confined to the Coastal Plain such changes. Instead it seems that the conditions Columbia group. The Sunderland, Wicomico, which is still in progress. It is this which has were also developed. At this time the shore line under which the Eocene deposits were produced and Talbot formations, which make ,up this group, produced the estuaries and tide-water marshes seems to have been farther east than now, and were lemarkably uniform, considering the great are exposed over a series of terraces lying one that form conspicuous features of the existing the present submerged channels of the continental length of time which elapsed from the beginning above another throughout the North Atlantic topography. At the present time the waves of shelf were probably then eroded. The Coastal to the close of the period. Coastal Plain from Raritan Bay to Potomac the Atlantic Ocean and Chesapeake Bay are at Plain portions of Delaware River, with its exten­ Miocene history. Eocene sedimentation was River, as well as in Virginia and probably still work tearing away the land along their margins sion Delaware Bay; Chesapeake Bay, which is the brought to a close by an uplift by which the shore farther south. The key to the solution of the and depositing it on a subaqueous platform or ter­ continuation of Susquehanna River; and Potomac, line was carried far to the east and probably all of relations existing between the surficial deposits of race. This terrace is everywhere present in a more Patuxent, Rappahannock, James, and other rivers the present State of Maryland became land. This Maryland lies almost exclusively in a correct cor­ or less perfect state of development, and may be date from this post-Lafayette uplift. The attitude was followed by a resubmergence and another cycle relation of these terraces. Much light may be observed not only along the exposed shores, but of the subsequent deposits makes this evident, for was commenced. The deposits of the Miocene were thrown on this problem by a careful study of the also on passing up the estuaries to their heads. the Sunderland, Wicomico, Talbot, and Recent laid down upon the land surface which had just Recent terrace now forming along the shores of The materials which compose it are varied, depend­ terrace formations all slope toward these various been depressed beneath the water. Sluggish streams the Atlantic Ocean and Chesapeake Bay and its ing both on the detritus directly surrendered by waterways. The Lafayette formation was cut brought in fine sand and mud, which the waves and tributaries. A discussion of this terrace is given the land to the sea and on the currents which through by the streams, and valleys were opened ocean currents spread over the sea bottom. Occa­ below. sweep along the shore. On an unbroken coast the in the older deposits. Several of these valleys sionally leaves from land plants were also carried After the close of the post-Lafayette erosion material has a local character, while in the vicinity became many miles wide before the corrasive power out to sea and later dropped to the bottom as they period the Coastal Plain was gradually lowered of a river mouth the terraces are composed of de*bris of the streams was checked by the Sunderland sub­ became saturated with water. and the Sunderland sea advanced over the sinking contributed from the entire river basin. mergence. Near the beginning of Miocene submergence, region. The waves of this sea cut a scarp against Besides building a terrace, the waves of the Sunderland stage. As the Coastal Plain was certain portions of the sea bottom received little or the existing headlands of Lafayette and older rocks. ocean and bay are cutting a sea cliff along their depressed, in early Pleistocene time, the ocean no materials from the land, and the water in those This scarp was prominent in some places and coast line, the height of the cliff depending not so waters gradually extended up the river valleys and places was well suited as a habitat for diatoms. obscure in others, but may be readily recognized much on the force of the breakers as on the relief over the lower lying portions of the stream divides. 11

The waves worked on the Lafayette-covered divides another downward movement began. This last materials at the base of the deposits, with a rather these indurated ledges furnish considerable mate­ and removed the mantle of loose materials, which subsidence is probably still in progress. Before persistent loam cap which marks the last stage of rial for the construction of foundations and walls. were either deposited farther out in the ocean 5or it began South, West, Patuxent, and Potomac deposition during each particular submergence. The best stone of this class is the firmly cemented dropped in the estuaries formed by the drowning rivers, instead of being estuaries, were undoubt­ This surficial loam, which is very similar in all white sandstone occurring in the Magothy forma­ of the lower courses of the streams. Sea cliffs edly streams of varying importance lying above four formations, has been extensively used for the tion about 1 mile north of Collington. The shell produced on points exposed to wave action were tide and emptying into a diminished Chesapeake manufacture of brick at many places in Virginia, beds of the Aquia in the vicinity of Upper Marl­ gradually pushed back as long as the sea continued Bay. Whether this movement will continue much the District of Columbia, Maryland, and southeast­ boro are so firmly consolidated that they furnish to advance. These cliffs are now represented by longer can not, of course, be determined, but with ern Pennsylvania, It is generally not more than 3 building stone, which though of poor grade is the escarpment separating the Sunderland from the respect to Delaware River there is sufficient evidence or 4 feet in thickness, yet, because of its position, nevertheless suitable for rough work. The gravel Lafayette. The materials which the waves gath­ to show that it has been in progress within very many beds no more than 1 or 2 feet thick can be bands of the Lafayette and Pleistocene are, in many ered from the shore, together with other materials recent time and undoubtedly still continues. Many worked with profit. The loam is widely distrib­ places, so firmly cemented by iron oxide as to form brought in by the streams, were spread out in the square miles that had been land before this subsi­ uted throughout the Patuxent quadrangle and, pebble conglomerates of considerable strength. A estuaries and constitute the Sunderland formation. dence commenced are now beneath the waters of though not quite coextensive with the formations portion of the wall about St. Elizabeth's Asylum The tendency of the work done was to destroy all Chesapeake Bay and its estuaries, and are receiv­ of which it forms a part, it is present in almost is constructed of a ferruginous conglomerate of this irregularities produced during the post-Lafayette ing deposits of mud and sand from the adjoining every locality where the Lafayette and Pleistocene character. formations occupy flat divides that have not suf­ erosion interval. In many places old stream courses land. MARLS. were undoubtedly obliterated, but the channels of fered much erosion since their deposition. In the larger streams, although probably in some ECONOMIC GEOLOGY. general the surface loam is adapted only to the Glauconite marls. The Eocene and Upper Cre­ places entirely filled, were in the main left lower manufacture of the common varieties of brick and taceous formations of the Patuxent quadrangle are MINERAL RESOURCES. than the surrounding regions. Thus in the uplift tile, but in some places it is suitable for making rich in deposits of glauconitic marls, which are of following Sunderland deposition the larger streams The mineral resources of this region are neither a fair quality of paving brick. In the Patuxent value as fertilizers. From New Jersey to North reoccupied practically the same channels they had extensive nor especially valuable, but the Patuxent quadrangle the surface loam from the Talbot and Carolina such deposits have been worked spasmod­ carved out in the preceding erosion period. They quadrangle contains some deposits that are of con­ Wicomico formations has been utilized at several ically since the early part of the last century, when at once began to clear their channels and to widen siderable economic importance, although they have different times for the manufacture of brick in the their value was first determined, yet their impor­ their valleys, so that when the next submergence not hitherto been very largely worked. Among eastern part of Washington, near Anacostia River. tance in enriching the soil has never been gen­ occurred the streams were eroding, as before, in the most important are clays, sands, gravels, build­ erally recognized. They consist of quartz sand SANDS. Tertiary and Cretaceous materials. On the divides ing stone, glauconitic and shell marls, diatomaceous with an admixture of many grains of glauconite, also the Sunderland was gradually undermined and earth, and iron ore. In addition the soils con­ Inasmuch as the arenaceous phase predominates a soft green mineral which is essentially a hydrous worn back. tribute much to the value of the region, which is in almost every Coastal Plain formation represented silicate of iron and potassium. On account of the Wicomico stage. When the Coastal Plain had primarily an agricultural one, and abundant sup­ in the region, the Patuxent quadrangle contains an glauconite, the marls are green in color and are been above water for a considerable time after the plies of water, readily obtainable in almost every unlimited supply of sand. The sand of the Pleis­ commonly known as "greensand marls." They close of Sunderland deposition a gradual submer­ portion of the quadrangle, form a further part of tocene and Lafayette formations is used locally for are rich in calcium carbonate derived from the gence again occurred, so that the ocean waters once its mineral wealth. building purposes, but as it is so readily obtainable shells which are abundant in the deposits, and more encroached on the land. This submergence in all parts of the region no large pits have been chemical analyses usually show the presence of seems to have been about equal in amount through­ CLAYS. opened. small amounts of mineral phosphates. The marls out a large portion of the district, showing that the Next to the soils the clays constitute the most In some places the quartz sands of the Miocene thus contain three important plant foods potash, downward movement was without deformation. valuable economic deposits of the Patuxent quad­ seem to be pure enough for glass making, suggest­ lime, and phosphates. Altogether these constitute The sea did not advance upon the land as far as it rangle. As already stated in the discussion of ing the Miocene glass sands so extensively exploited only a small percentage of the entire content of the did during the previous submergence. At many the stratigraphy of the region (p. 3), several of in southern New Jersey, although they have never deposits, yet wherever the marls can be obtained at places along the shore the waves cut cliffs into the the formations contain considerable quantities of been used in that way in this region. Careful low cost, they furnish economical means for increas­ deposits that had been laid down during the pre­ clay. These argillaceous beds are rather generally chemical analyses and physical tests, which have ing soil fertility. Where the glauconite marls have ceding epoch of deposition. Throughout many distributed throughout the quadrangle, but, so far not been made, would be required to determine been used it is claimed that their beneficial effect is portions of the Coastal Plain at the present time as known, have in recent years been worked only their usefulness in this industry. much more lasting than that obtained by means of these old sea cliffs are still preserved as escarpments, in the vicinity of Washington. In colonial days The Magothy sands in the vicinity of Anacostia artificial fertilizers. Within the quadrangle many ranging from 10 to 15 feet in height. Where the bricks were made at a number of points through­ have long been worked and at present the most Eocene and Upper Cretaceous beds rich in glauco­ waves were not sufficiently strong to enable them out the region. The clays are found in each series extensive sand pits of the quadrangle are opened nite outcrop along the sides of the stream valleys, to cut cliffs it is somewhat difficult to locate the old of deposits represented in the region. For con­ in deposits of this age a short distance south of extending in a belt diagonally across the quadrangle shore line. During this time a large portion of venience they may be discussed under the head­ Anacostia. The sand is used for building and from South River to Mattawoman Creek. the Patuxent quadrangle was submerged. The ings Potomac, Eocene and Miocene, and Lafayette filtering purposes. In pertain places the Potomac Shell marls. The shell marls of the Miocene Sunderland deposits were largely destroyed by the and Pleistocene clays. deposits contain molding sand of fair grade, but it and Eocene formations also possess valuable ferti­ advancing waves and redeposited over the floor of Potomac clays. The clays of the Potomac group has not been used to any great extent. lizing properties for soils deficient in lime. In the Wicomico sea, although those portions which are the most valuable within the region under con­ Locally the Lafayette and Pleistocene sands are some places the shells are mixed with so much sand lay above 90 to 100 feet were for the most part sideration. Each formation of the group contains rich in ferruginous matter, which in some places that the lime forms only a small part of the deposit, preserved. Deposition of materials brought down deposits of clay that are suitable for a variety of cements the grains together, forming a ferruginous but in others the amount of lime exceeds 90 per by streams from the adjoining land also took place. uses. Some clays from the Patuxent have been sandstone. Sands of this character possess a dis­ cent. Experiments show that better results have Although the Wicomico submergence permitted employed for the manufacture of common brick, tinct value for road-making purposes, as they pack been obtained by the use of shell marl than by the silting up of the submerged stream channels, fire brick, and terra cotta; the Arundel contains readily and make a firm road bed. Where the that of burned stone lime. The marl acts both yet the deposits were not thick enough to fill them clays adapted to the manufacture of common material can be easily obtained in large quantities, chemically and physically and has a beneficial entirely. Accordingly, in the uplift following brick, terra cotta, sewer pipes, and pottery; the good roads can be very economically constructed effect on both clayey and sandy soils. So far as Wicomico deposition the large streams reoccupied Patapsco with its great variety of clays furnishes with it. known, the shell rnarls of this region have not their former channels, with perhaps only slight material suitable for the manufacture of common been utilized, although they are extensively devel­ GRAVELS. changes. New streams were also developed and brick, fire brick, and other refractory ware, sewer oped in many localities in the southeastern part of the Wicomico plain was more or less dissected along pipes, and pottery; and the somewhat less argilla­ The Pleistocene, Lafayette, and Potomac forma­ the quadrangle. the water courses, the divides being at the same ceous Raritan formation contains clays adapted to tions contain numerous beds of gravel widely dis­ time gradually narrowed. This erosion period was the manufacture of common brick, terra cotta, and tributed throughout the region. Those of the DIATOMACEOUS EARTH. interrupted by the Talbot submergence, which car­ fire brick. Pleistocene and Lafayette deposits are generally The principal diggings for diatomaceous earth ried part of the land beneath the sea and again JSocene and Miocene clays. Although argilla­ rich in iron, which acts as a cementing agent, thus are at Lyons Creek, although a bed of the material drowned the lower courses of the streams. ceous beds occur very commonly in the Eocene and rendering them of considerable value as ballast for occurring at the base of the Calvert formation Talbot stage. The Talbot deposition did not take Miocene strata of the quadrangle, in general they roads. There are numerous gravel pits in the extends from Fairhaveu, on the bay shore, to Pope place over so extensive an area as was covered by are too sandy to be of much economic importance. eastern part of the District of Columbia in deposits Creek, on Potomac River, beyond the quadrangle that of the Wicomico. It was confined to the old Considerable lime, derived from the numerous fos­ belonging to the Sunderland and Lafayette forma­ boundary. Diatomaceous earth, on account of its valleys and to the low stream divides, where the sil shells which are either generally distributed tions, and elsewhere in the vicinity of Washington porosity and compactness, is used in water filters advancing waves destroyed the Wicomico deposits. throughout the sandy clay or concentrated in defi­ there are smaller pits in deposits of Wicomico- and and as an absorbent in the manufacture of dyna­ The sea cliffs were pushed back as long as the nite shell beds within the formations, also renders Talbot age. mite. It is reduced readily to a fine powder and waves advanced, and now stand as an escarpment these clays of less value. They are, however, very makes an excellent base for polishing compounds, that marks the boundaries of the Talbot sea and accessible, being exposed in the cliffs along Chesa­ BUILDING STONE. while its nonconductivity of heat makes it a valu­ estuaries. This is the Talbot-Wicomico escarp­ peake Bay and Patuxent River and in the valleys The Patuxent quadrangle contains few beds of able ingredient in packing for steam boilers and ment, previously described. At some places in of tributary streams, and if a way of utilizing them building stone of much importance, yet in places pipes and in the manufacture of safes, the latter the old stream channels the deposits were so thick should be discovered, they could be obtained in materials occurring within the region have been being the principal use to which it is put. It has that the streams in the succeeding period of eleva­ great quantities at little expense. The pink clay used locally. The granite gneiss is the best build­ been thought that this earth might be of use in tion and erosion found it easier to excavate new at the base of the Nanjemoy formation, known as ing stone of the quadrangle and furnishes good certain branches of pottery manufacture which courses than to follow the old ones. Generally, the Marlboro clay, is the most valuable deposit of material for foundations and other rough work. It require refractory materials that have no color however, the streams reoccupied their former chan­ this group. It is about 25 feet thick and is exposed is schistose and consequently can not be obtained when burned. Heinrich Ries tested a sample of nels and renewed the corrasive work which had at many places in the stream valleys between South in large masses, but for that reason can be very diatomaceous earth from Lyons Creek at cone 27 been interrupted by the Talbot submergence. As River and Upper Marlboro, and at a few places easily quarried. Some of the more massive beds in the Deville furnace and found that the material a result of this erosion the Talbot plain is now in still farther southwest. The clay is fairly plastic furnish stones suitable for building, and in places, fused to a drop of brownish glass. Its nonrefrac- many places rather uneven, yet it is more regular and no doubt could be used for making pressed where the beds are thinner and more micaceous, tory character is thus clearly demonstrated. than the remnants of the Lafayette, Sunderland, brick, but is not plastic enough and is, besides, flagstones can be obtained. and Wicomico plains, which have been subjected rather too sandy for pottery. Although the Coastal Plain formations of the IRON ORE. to denudation for a much longer period. Lafayette and Pleistocene clays. As already region are composed almost entirely of unconsoli- The Arundel formation, in the Potomac belt, is a Recent stage. The land probably did not long stated, the Lafayette, Sunderland, Wicomico, and dated materials, yet locally indurated beds are not famous source of iron ore. It yields iron carbonate, remain stationary with respect to sea level before Talbot formations are generally composed of coarse uncommon. In the absence of any better stone limonite, hematite, Venetian-red ocher, etc. Simi- Patuxent. 12 lar ores are found at other horizons'in the Potomac, along the valley^slopes. From these springs many water rising under artesian pressure above the Ions a minute was obtained at a depth of 140 and although no valuable deposits are known at of the inhabitants obtain their entire supply of point where it enters the well, but not overflow­ feet; at the Reform School water was encoun­ the present time within this quadrangle, yet in water, which is usually of excellent character. The ing. .The somewhat meager data obtained in this tered at a depth of 270 feet; and near Chesapeake contiguous regions the iron ores have been mined spring water, as also that in wells, is in places and adjoining regions indicate the occurrence of Junction a well which formerly flowed but now has to a greater or less extent ever since colonial times. highly charged with mineral matter, particularly water at the horizons described in the following to be pumped obtains its supply of water at a depth They are obtained by open cuts and by shafts. iron, sulphur, and salt, and some such waters have paragraphs. Depths to these water-bearing strata of 350 feet. At Annapolis, on the grounds of the From these ores a very high grade of pig iron is been placed on the market. The most important in the quadrangle are given on the artesian-water United States Naval Academy, a well sunk to the made and the iron, which is noted for its toughness, mineral springs of the quadrangle from which map. depth of 601 feet penetrated eight water-bearing- is in demand at the United States Government waters have been sold are the Bladensburg Spa at Waters of the crystalline rocks. The waters con­ strata within the Potomac beds, from three of arsenals and navy-yards and to some extent in Bladensburg and the Algonquin Springs at Oxon. tained in the crystalline rocks of the Piedmont which water flowed out at the surface, 8 feet above Europe. The only furnace now smelting the ore Plateau are not of especial importance in this tide. At the lowest horizon, between 587 and 601 is located at Muirkirk, not far from the northern SHALLOW WELLS. quadrangle, since these rocks -occur at or near the feet, a flow of water of 75 gallons a minute is border of this quadrangle. This is at present the Nearly all the water supply of the Patuxent surface in a very small area. In the vicinity of obtained. The water contains iron, but is of excel­ most important iron district of the entire Arundel quadrangle is derived from shallow wells, varying Washington some wells obtain water from these lent quality when filtered. belt and mining has been carried on here for over in depth from 15 to 35 feet. The water is con­ rocks, but to the northwest of this quadrangle they Water horizons in the Upper Cretaceous. The fifty years. The slag has been utilized to a consid­ tained in the rather coarse sand or gravel bed so yield an important water supply. In general water sandy strata of the Magothy formation are in many erable extent as road metal. commonly forming the basal stratum of the Pleis­ occurs at less definite horizons in the crystalline places water bearing. The water is apt to be tocene and Lafayette deposits. So generally is this rocks than in the Coastal Plain deposits, and it is strongly impregnated with iron, and locally with SOILS. the case that the depth of the shallow wells is consequently much more difficult to predict the sulphur; consequently it is less desirable than that The soils which the various formations of the usually a very good indication of the thickness of depth to which wells must be sunk to obtain a good obtained from the Potomac deposits. At Upper Patuxent quadrangle yield have been carefully the surficial deposits. The surface water very supply. .Marlboro several flowing wells with an average mapped by J. A. Bonsteel, and his results, with a readily penetrates the rather coarse surface mate­ Crystalline floor horizon. Beneath the unconsoli- depth of about 225 feet obtain a good supply of full discussion, have been published by the United rials until it reaches the less permeable underlying dated sedimentary deposits of the Patuxent quadran­ water from the Magothy. In some of the wells States Department of Agriculture for those portions sedimentary or crystalline rocks. While some of gle crystalline rocks similar to those exposed at the the amount of mineral matter in solution renders of the quadrangle which lie within Prince Georges, it continues its downward course into these harder surface in the northwestern portion of the quad­ the water somewhat undesirable for drinking pur­ Calvert, and St. Marys counties. Those desiring rocks a great deal flows along on their upper sur­ rangle undoubtedly occur. This underlying con­ poses, while in others the mineral matter seems to information on this subject are referred to the face until it finds its way gradually into the streams. solidated rock mass is frequently spoken of as be present only in very small amounts. The Naval publications of that Department (Field Operations Hence wells sunk to this level are practically "bed rock." In general the crystalline rocks are Academy well at Annapolis obtained flowing water of Division of Soils, 1900 and 1901) as well as to assured of a supply of water which, while seldom less permeable than the overlying deposits and from the Magothy at a depth between 180 and 220 forthcoming reports by the Maryland Geological large in flow, is in seasons of average rainfall consequently check the downward passage of the feet, but as the supply was not sufficient the well Survey on these counties. capable of furnishing sufficient water for ordinary percolating soil water, which tends to flow along was sunk deeper. purposes. Such shallow wells are necessarily on their surface or. to collect in depressions. The In New Jersey considerable artesian water has PETROLEUM AND NATURAL GAS. dependent almost entirely on the amount of water surface of these old rocks dips rather uniformly to been obtained from the greensand deposits of the Rumors have been circulated at various times of which percolates through the Columbia and Lafay­ the southeast at an average rate of more than 100 Upper Cretaceous. In this region no artesian wells the discovery of petroleum and natural gas at sev­ ette deposits after rain storms, and are thus apt to feet to the mile. Along this crystalline floor much are known in which the supply of water is obtained eral different places within the Patuxent quadran­ be affected by droughts. After periods of heavy water flows to lower levels, and it therefore marks from the Matawan or Monmouth deposits. These gle. Although many of these rumors have been rainfall the water may rise in the wells within a a good water horizon. Several artesian wells in are in general more porous than those of the Mago­ without foundation, small amounts of oil and gas few feet of the surface and then is very roily. At the Coastal Plain derive an unfailing supply of thy or Potomac formations and contain fewer clay have been observed in some places during the sink­ other times the wells may become dry, yet this does pure water from this level. In Washington and bands, so that the water passes more readily to ing of wells and in the vicinity of streams where not often occur because of the fairly equable distri­ the near vicinity water is obtained at this horizon lower levels. there is seepage from porous beds. The gases gen­ bution of rainfall during the year. The supply is in several wells, of which those at St. Elizabeth's Water horizons in the Eocene. The character of erated by decaying vegetation have been mistaken less variable over the broad divides or on level Asylum are the largest. Five of the six artesian the Eocene beds is in the main similar to that of the in certain cases for natural gas, and the iridescent ground, where water is always nearer the surface, wells that supply the water system of Hyattsville Upper Cretaceous. More clay members are pres­ film of limonite that sometimes appears on the sur­ than in the regions of narrow stream divides, where probably obtain water at this horizon, which is ent, however, and consequently conditions for flow­ face of stagnant water in swamps and bogs has the water finds an easy exit to the streams. In reached at a depth of 250 feet. Though the ing wells are more favorable. The water is almost been supposed to be petroleum. some places on the narrow divides in proximity to water will overflow, the yield is increased by pump­ everywhere heavily charged with iron, and sulphur Borings have been made about 2 miles west of the major streams, it is necessary to sink wells to ing. These five wells, together with another less is also present in places. Nevertheless, more flow­ Annapolis and about 1 mile south of Meadows in the depth of 100 feet or more in order to obtain a than half as deep, are all pumped together and ing wells in the Patuxent quadrangle obtain their the search for oil and gas, but only traces were permanent supply of water. yield 130 gallons a minute. supply of water from the Eocene than from any found. The Meadows well was sunk to a depth of Most of the water of the shallow wells is obtained Throughout the greater portion of the quadran­ other horizon. At Galesville there are several 1511 feet, in all probability nearly to the crystalline at the base of the Lafayette or Sunderland deposits, gle this crystalline floor can never be very impor­ flowing wells ranging in depth from 110 to 150 rocks, thus practically proving the absence in that as each of these formations covers large areas in tant as a water horizon because of its great depth. feet; on the low-lying land to the east of Sudley, place of any considerable amounts of either of which the streams have not yet cut through to the It was not reached in a 1511-foojt boring about 1 locally known as "The Swamp," there are from these materials. It is not probable that either underlying deposits. There are also a number of mile south of Meadows, and it is probable that it twenty-five to thirty flowing wells, ranging in depth petroleum or natural gas in paying quantities will shallow wells in the Patuxent River valley that lies as much as 2000 feet below tide over a large from 120 to 140 feet; and at Leitch Wharf a flow be found within the limits of the quadrangle. derive their water supply from the base of the portion of the quadrangle. of water is obtained at 140 feet. Most of the wells Talbot formation. Water horizons in the Potomac strata. The have a flow of 8 to 12 gallons a minute, but a few WATEE RESOURCES. The water of the shallow wells usually contains Potomac deposits contain many beds of coarse yield only 1 to 2 gallons. The water supply of the Patuxent quadrangle is so little mineral matter in solution that it is known material that constitute good water-bearing strata. At Chesapeake Beach water has been obtained at found in the streams and wells of the district. as soft water. In many wells, no doubt, it does Some of fhese sand and gravel beds lie between a depth of 295 feet from a lower horizon in the Many of the streams have been used at various contain organic matter, yet there is little evidence impervious clay deposits and thus furnish the Eocene, probably near the base of the Aquia. It times to furnish power for small mills, but little to show that the water on this account is unfit for requisite conditions for flowing artesian wells. contains less mineral matter than the water from use has been made of them as sources of water drinking purposes. In many places, particularly Within the District of Columbia the bed$ belong­ the above-mentioned wells, which is derived proba­ supply. Washington, the only city within the in the low-lying region, bordering Chesapeake Bay ing to the Potomac group are the principal water­ bly from near the base of the IsFanjemoy. quadrangle, obtains its water supply at a point between West River and Herring Bay, the old- bearing formations. The water does not seem to Water horizons in the Miocene. In the southern some distance beyond the boundary. Annapolis, fashioned well sweep is used to bring the water to come from any one horizon of wide distribution, half of the quadrangle artesian water is obtainable the main portion of which lies just east of the the surface. as is shown by the varying depths at which it is from the Calvert formation. The Miocene deposits quadrangle, is the only city that draws its supply reached and by the failure to obtain any water in in the Coastal Plain contain, intercalated between ARTESIAN WELLS. of water from this region, the source being Broad these beds at certain places. Wells that were impervious argillaceous strata, numerous sandy beds Creek, a tributary of South River. With the Since water is so readily procured at shallow unsuccessful in finding a satisfactory supply of which furnish good supplies of water, usually of exception of the residents of these two cities, the depths in. almost all sections of this quadrangle water were the 360-foot well at the ice works and excellent quality. At North Chesapeake Beach a inhabitants of the quadrangle derive their water and few establishments in the region require a large the 133-foot well at the Mount Vernon apartment good flow7 of water is obtained from the Miocene supply from springs and wells. The wells are supply, there have not been many attempts to obtain house. On the other hand, at Hyattsville and in at a depth of 85 feet. At Governor Run, just divided into two classes shallow dug wells and artesian water except on the low-lying land adjoin­ the vicinity there are several wells with small flow beyond the southeast corner of this quadrangle, deeper bored wells, the deeper usually furnishing ing Chesapeake Bay, where flowing wells can be that derive their supply of water from Potomac there is a well a little more than 100 feet in depth artesian water. had at small expense. The area in which wells strata at depths between 100 and 112 feet. At that derives a good supply of excellent water from may be driven with the expectation of discovering Bladensburg flowing wells with capacities ranging Miocene strata. This well discharges about 10 feet SPRINGS. a pressure sufficient to force the water to the sur­ from 1 to 15 gallons a minute have been obtained above tide and when it was first sunk had a flow of The gently sloping strata, the alternation of face is restricted to land lying 20 feet or less above at depths between 73 and 100 feet; at the plant about 25 gallons a minute, but at present the flow porous and impervious beds, and the great amount tide. In areas above this altitude pump wells can of the National Capital Brewing Company there is considerably less. of dissection by streams which the region has probably be had from the water-bearing strata is a 103-foot well that yields from 100 to 130 undergone, all contribute to the formation of springs enumerated in the succeeding paragraphs, the gallons a minute; at Langdon a flow of 40 gal- J April, 1907.