,. EXCURSION OF THE NEW YORK STATE GEOLOGICAL ASSOCIATION

IN THE NEW YORK C ITY REG I ON May 12th - 13th, 1933

G. MARSHALL KAY COLUMBIA UNIVERSITY

(Note: Much of the region is described in Guidebqok 9, and Vicinity, by c. P. Berkey, G. I. Finlay, R. J. Colony and others, to be issued by the International Geological Congress, Xvith sessiont Washington, 1933. The following guide has made use of the material in that guidebook.J

INTRODUCTION Stop 1. Snake Hill is just southwest of Newburgh along State Highway 32. The locali­ The region to be visited in this excur­ ty has an outlier of resistant Pochuck gneiss sion is one including parts of several geolo­ that is an isolated remnant of a once-conti­ gical and physiographic provinces {see Figure nuous crystalline mass that was overthrust 1). The first stops are to be made adjacent northward from the Highlands upDn the Hudson to the Highlands of the Hudson, where the re­ River beds (see Figure 3). This overthrust sistant crystalline rocks of the Reading prong was cut later by a normal fault that tran­ of the New ·England Upland have been dissected sects the eastern side of the Hill and brings by the superimposed Hudson River. Northwest the Hudson River beds in contact with the of the Highlands, these crystalline rocks are older Wappinger limestone on the east. in faulted contact with the folded Paleozoic sediments of the Hudson Valley extension of the Folded Appalachians. The Catskill Moun­ tains farther northwest are the northern end of the Appalachian Plateau. East of the Hudson River from Peekskill to New York City, the meta-sediments lie in the Manhattan Prong of the New England Upland that terminates on Staten Island, New York City. To the west of the Hudson is the Trias­ sic Lowland margined on the east by the Pali­ sades, the river occupying a subsequent valley ---,oo_.__o_ _..___~lOO---:-:Mc-:'~:::.:··· ( a.ft er CO l O '1.y) in the underlying, gently westward-dipping, relatively non-resistant basal Triassic sedi­ Figure 3. Section through Snake Hill. ments. Thus there are two faults in the s action. The geologic column and history of each The older overthrust might be from the evi­ of theRe parts of the region will be treated dence in this section of Taconic (post-Ordo­ separately as the route traverses each area. vician, pre-Silurian) age; deformation of this age is lmown east of the Catskill Moun­ tains at Kingston. But from the fact that ITINERARY: NEWBURGH TO PEEKSKILL similar faults in the imnediate region affect Devonian sediments, it is inferred that the The first of the route maps (Figure 2) thrust on Snake Hill is post-Devonian. This shows the course of the excursion from New­ faulting may have occurred in the Acadic burgh to New York City. The first stops are disturbance {immediately post-Devonian) or on the northwest border of the Highlands at the Appalachian revolution (post-Permian). Snake Hill and Cornwall. The section in this Inasnmch as there are no sediments younger district includes an older series of crystal­ than Devonian in eastern New York north of line gneisses and Schists, the Pochuck, the Highlands, it is not possible to learn that have been intruded by younger granites with assurance which per iod of deformation is such as· the Storm King and Canada Hill represented; perhaps both affected the region. granites; these rocks are Pre-Cambrian. The faulting is thought to have occurred in In some localities they are un.coni"ormably the Appalachian revolution. overlain by the Cambrian Pough~ag quartzite The fault that cuts the gneiss on the (600 feet thick), the Cambro-Or ovician east side of the hill is believed to have Waapinger limestone (about 1000 feet) and the occurred in the Palisade disturbance (post­ Hu son River phyllite · (a few thousand feet Triassic) because similar normal faults of thick). Along the route of the excursion, the that age occur south of the Highlands. sediments are in fault contact with the Pre­ Cambrian crys~llines Stop 2, southwest of Cornwall-on-Hudson

(1) 40~ is a locality where a thrust fault simi­ lit-·par-lit injections and dike-like and lar to that at Snake Hill brings the sill-like intrusions that commonly 60 per crystalline rocks over the Hudson River cent of it is igneous. The thickness is phyllites. unknown. The overlying Inwood marble is a massive, strongly-bedded, coarsely-crystal­ Between stops 2 and 3, the latter line magnesian limestone, the upper part of at the east end of Bear Mountain Bridge, which is generally impure and micaceous. north of Peekskill, the crystall~ne rocks of It is about 700 feet thick in New York Cit~ the Highlands are passed in many exposures. The formation is locally cut by pegmatite Most are ~of the granites of the Storm King dikes, but as a whole is quite free of ig­ and Canada Hill formations. At stop 3, the neous matter. The contact with the Manhat­ Canada Hill granite has been intruded by tan schist is a transitional one with in­ ~ounger pegmatite dikes. terbeddiruz: of the two sorts of rock. The course of the Hudson River through the Highlands is believed to be that of a stream superimposed on the crystalline rocks from a co­ ver of sedimentary rocks that has been removed. Recent studies sug­ gest that Cretaceous sediments once transgressed tne area, and that the ancient Hudson that flowed conse­ quently on the plain that was ex­ posed with the retreat of the Cre­ taceous sea was "let down" on the "barrier" of crystallines. The less resistant sedlmenta have been removed, but the more resistant granites and gneisses remain as the Highlands of the Hudson. Below the Highlands, the river has become adjusted to the resis­ tance of the belts of rock that it traverses. This subsequent drain­ age will be discussed more fully in connection with the stop on the top of the Palisades at Edgewater (stop 7).

Figure 1. Block Diagram of the region from Newburgh to New York City (by Raisz after Berkey).

From Peekskill to New York City the ~oute travdrses a region underlain by the crystalline Ford­ ham. gneiss, Inwood marble and Man­ hattan schist; the formations will be ~xamined 1n Manhattan and The Bronx, New York City. They are be­ lieved to be of Pre-Cambrian age, though some have thought the younga­ two to be of early Paleozoic age. 0 C f AN The Fordham gneiss is typical­ ly a black and white banded, qua.rtzose and granitic gneiss, in places schistoae, and so thoroughly impregnated with pegmatitic and 5 0 25 MILES granitic matter in the form of ._._....._.~s--=-o--'---..L.--L---2...IS_K_IL_O--JMETERS 11.o..Pu.l.._l... _..___._..a._~-..JI

( 2) ,4,a;s FIGURE 6 FIGURE 2 ROUTE MAP RO UTE MAP EDGEWATER NEvVBURGH TO TO STATEN ISLAl'JD NEW YORK

Scale Mcl es Sea.le Mi le.s The Route~ Th e. Route~ Border of t,e Highlands · · · · · ·· ... Othu Roo.d, --

Ma.rgin of Seep£ntine _.,_ ___s _ _

Ma.rgin of Termin-a.in~ •··········•

Ma.nho.He1n Schist in New Ju~e!I ~

( 3) 492~ The Manhattan schist is a dark, deepened to make it navigable. streaked, strongly micaceous, coarsely crys­ talline, markedly foliated rock, locally Stop 5, at 204th Street and Nagle Ave­ carrying large quantities of quartz, feld­ nue, Manhattan, is an excavation in these apar and garnet, and exceeding 3000 feet in westward dipping Inwood marble beds; a large thickness. It is filled with irregular pegmatite dike cuts across the structure. masses of pegmatitic material and pegmatite From an examination of quartzitic beds above dikes and contains a few layers of horn­ the west face of the excavation, one gains blende schist that are believed to represent an impression of the more con~etent charac­ metamorphosed sills of basic ter of such strata. The surface of the hill intruded prior to the foliation of the rock. is strewn with boulders of glacial drift, and tbe marble has locally disintegrated to This series of crystalline rocks is be­ sand. The varying resistances of the beds lieved to have had the following history. have produced miniature subsequent monoclin­ Fine elastic sediments, shales, were deposi­ al ridges and valleys on the weathered sur­ ted in a sea; the source of the materials faces. and character of the under lying rocks are unknown. These shales were succeeded by Stop 6, along the Harlem Speedway, is limestones and later by more shales, the beneath the same Washington bridge that was three constituting the darker part of . the crossed earlier in the afternoon. The Fordham, the Inwood and the Manhattan. schist is the Manhattan, and in addition to Basic igneous rocks were intruded into these the pegmatitic material permeating the sediments during or after their deposition formation, there are remarkably parallel (and are now represented by the hornblende pegmatite dikes that dip gently to the west. schists). These undisturbed pegmatites reach a thick­ These sediments were buried under a ness of ten feet, and frequently show in the thiclc cover of since-removed sediments, and finer crystalline te~ture of their periphery the region was affected by the intrusion of the effect of having been chilled by cooler large quantities of granitic material that wall rocks. The east end of Figure 5 gives thoroughly permeated the shaly beds; these a section such as that &cross the Harlem include the light-colored injections in the River from stop 6 to stop 4. Fordham. The intrustion was accompanied by or -followed by intense Fegional metamor­ phism that folded incompetent beds and pro­ The buses will return to Dyckman Street. duced a crystalline, foliated lithology. Dinner will be held at the Faculty Club, Subsequent to this deformation, later Columbia University (see inset, Figure 4), igneous rocks were intruded along joints and at 7:00. The University may be reached :Crom planes of weakness; and are now represented Dyclanan Stre&t subway station by taking· the by the undisturbed pegmatites that will be downtown train to 116th street; Times Square seen along Harlem Speedway in Manhattan. and Pennsylvania Station are farther south The time of the deformation cannot be deter­ at 42nd and 32nd streets, respectively·. mined with assurance, but the foliatim pre­ _ Ir 1 t is desired, the cars may be sumably was developed in Pre-Cambrian time, driven west to Riverside Drive, and south­ for similar foliated Pre-Cambrian rock lies ward to the Columbia University district to beneath Cambrian quartzite north of the be garaged; there are a number of garages Highlands. east of Broadway south or 125th street. The rocks had been eroded and pene­ planed prior to the deposition of the late The Faculty Club is at 117th Street and Triassic sediments. The later history of Morningside Drive. the region will be discussed subsequently.

ITINERARY: MANHA'Pl'AN AND THE BRONX ITINERARY: PALISADE DISTRICT On reaching northern Manhattan, the cars will be parked near the Dyckman Street Saturday morning, May 13th, will be de­ station of the Interborough subway system, voted to a study oft.he rocks or the Trias­ and the group will transrer to buses . sic Lowland across the Hudson River in . The cars will leave the University Stop 4, at an excavation southeast or at 9:00 1n the morning, and cross to Edge­ the plaza at the east end of the Washington water on the 125th Street Ferey. Ascend to (181st Street) bridge over the Harlem River THE TOP of the hill and park cars on the in The Bronx, ls an exposure of the charac­ right, then walk down hill to the hairpin teristically lit-par-lit injected and con­ turn on the highway. The group will conv·ene torted Fordham gneiss, the oldest formation at this point, stop 7, at 9:45. Ir it aeema in the city. The route then will pass ex­ advantageous, the cars may be driven dire ct;.. posures of the same formation to the north ly to the Palisades from the garages. as far as 207th Street bridge. The subse­ Be Conscious of the fact that you are quent valley 1n westward-dlpping Inwood on a main travelled road. Don't be careless. marble is an arm of the sea that has been

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FIGURE 4 ROUTE MAP OF ::/.;(:~ " ... ~ 'f .,,,,. .,,. MANHATTAN ~ y ).,. .,."( .,, .,.,

Scale )It .: .,, 0

The Rovt<. ;< . ,. Geologic Bounda.~i.es ...... " Fa.u.lts . A I > fordho.rn Gneiss ... , Inwood Lime:iton~ . )( . .. )< M11nha.1to.n Schist ... }( J\ X A A ,II x. )I; "x A: A ~;•v >< • : )( J( • J( • (~ z 0 X ,I( X .,r}( ._ ;v CZ:: ~ ;c K Jr ll :v cQ ~ ~ .J.. ~ ~ p ~ z ~ 0 t"" ~"' ~ ~ ;; 0 ~ -< ~ ~ 0 ~ «: ct: ~ ! 0 ll) ~ ~ 0 c:: 11 ~ z ~! 0 ~ ~ t u t.r.l V) i u ~ 0 ,-l 0 t.J '-'

I :n' r 1-t ~:~ 3 3 QII.,I Z'Z -.. I 3 I I 1 I II) ( s) 44- Stop 7. Hairpin turn on State Road The Hudson River is a drowned river, ·a long above Edgewater, New Jersey . (See west arm of the sea that occupies this subsequent end of Figure 5). The first concern will valley. The ancient gorge has been filled be with the Palisades . This sill with sediments that may have a depth of as was intruded into the lower part of the much as a thousand f eet at New York City. Triassic Newark sediments in latest 'T rias­ sic or early Jurassic time. It is a bout Following the peneplanation of the 700 feet thick at Edgewater, and overlies a crystalline rocks during early Triassic time, few pundred feet of reddish arkosic sand­ a great series of fluviatil e and lacustrine stones that rest unconformably on tbe sediments, perhaps exceeding 20,000 feet in crystalline rocks such a.s occur in Man­ t b iclmess, was deposited to the east of the hattan, though the contact is beneath the Appalachian mountains that had been folded river. These are the basal sediments of and elevated at the end of t h e Paleozoic. the Stocltton form.a. tion at the base of the Lavas were extruded and buried in these sedi­ Newark series. The sediments and included ments and are represented in the Orange and sill dip gently to the west at an angle of to the west of the region about seven degrees. The river occupies a that we traverse • .And at the same time, in­ subsequent valley along the weak belt of the trusion s such as the and a basal Newark sandstones with the resistant higher sill that will be examined at Granton crystalline rocks on the east and the diabase were intruded into the sediments. During or on the west. following Triassic time, normal faults broke After the intrusion of the magma that the sed:rnients into a series of blocks that was to form the diabase, the first parts to were tilted gently to the west. These block be cooled must have been those adjacent to mountains were reduced and peneplaned before the intruded sediments; at the lower contact, tb3 Late Cretaceous (Gulfian), for sediments not exposed at this stop, the igneous rock of that age mantle the peneplane to the is of extremely fine texture. Later, there south. With the sithdrawal of Cretaceous were certain minerals such as olivine that seas, consequent streams took couraes on the crystallized from the magma while the most of gently sloping plain that had been formed; it was still fluid. These minerals, being the ancient Hudson was one of these. With heavier than the surrounding liquid, settled further uplift of the region, the superim­ toward the bottom and formed a layer in the posed river took a course that is not the sill above the first cooled part adjacent to present one, but one whlch breached the Pali­ the chilled bottom contact. The rest of the sades near Sparkill, New Jersey, and passed magma continued to crystallize until finally southward to the west of the present Pali­ the coarser-textured center of the intrusive sades ridge in the region. body was bordered below by the olivine con­ More recent erosion along the weak lowest centrate and extended upward to the first Newark sediment belt has resulted in the cau­ chilled upper part of the mass. ture of this ancient Hudson's headwaters and Thus there is an olivine zone of varying the diversion of the water through the pre­ thickness that can be recognized along the sent course. face of the Palisades, and this zone being composed of' more rea'dily weathering rock From the top of the Palisades, the route forms a terrace that is evident along the proceeds westward to Ridgef'ield and southward rock. Spheroidal boulders may be seen form­ along the east side of the Hackensack Meadows ing as a result of the Yoeathering along · to Granton. Abmut a half' mile from the top joints that cut the rock. Small nor:-n al of the Palisades, west of where the street faults may also be recognized with downthrown car tracks cross the state road, the route side to the east. The columnar structure of crosses a small subsequent valley along one the diabase is also apparent, and being at of the fault zones that have displacement right angles to the cooling surface, the down to the east. The road then descends the joints tend to dip at an angle of seven de­ long dip slope on the back of the Palisades grees from the vertical and toward the east. sill to the Hackensack River valley eroded in Newark non-resistant shales. South of Ridge­ From the top of the hill, one gains a field, a prominent hill comes in view on the fine view of the city of New York, which is right or the road. bu ilt in its higher parts on a peneplane, the Fall Zone peneplane, that dips gently to the Stop 8. Belmont-Gurnee Stone Quarry, southeast beneath a cover of Cretaceous sedi­ Granton, New Jersey. This hill has been ments on Long Island. The older peneplane on rormed because of the resistance of a sill which the Triassic was deposited is largely intruded into the sedi~ents at a little obscured by the buildings on the east side of higher horizon than that of' the Palisades the Hudson, but as one looks northward be­ sill; this intrusive mass is or small lateral neath the new George Washington Bridge he can extent. project the basal Newark sediments and Pali­ The large quarry on the west face of the sade sill to the level of the top of the Pa­ hill displays the contact of' the igneous rock, lisades and upper Manhattan and conceive of a essentially a , with the underlying belt .of non-resistant rocks that has been re­ sandstones and shales of the Newark series. duced by the river; see Figure 5, west end. The contact can be more readily examined

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.farther to the north in the quarries. The sionally the serpentine contains minerals black' shales contain the only abundant fos­ that have survived from the earlier sils that occur in the New York city region, history. The formation is of pre-Cambrian specimens of the ostracod-like crustacean, age, and is intrusive into the Manhattan Estheria ovata Lea (see Figure 7.), about schist, although none of the schist occurs a third o~inch in length; they abound on on Staten Island. The contact has been some of the bedding planes. From the top of well exposed at Castle Point, in Hoboken, the hill, one can see the Watchung and Orange New Jersey, and there have been exposures mountains far to the west, cuestas of west­ on Manhattan, though all are now obscured. ward dipping Triassic extrusive rocks. To The Staten Island serpentine is thus an the southeast, rising in the meadows, is alteration product of a youngest Pre-Cam­ Snake Hill (another one1), an intrusive, brian formation in the New York City area. stock-like igneous mass. The route follows southward to Hudson This concludes the excursion. We have Boulevard, and continues along this road made rather brief exa~ination of each of through Jersey City and Bayonne to the Kill the geologic formations that comprises any van Kull bridge to Staten Island, New York considerable part of the New York City re­ City. gion.

ITINERARY: STATEN ISLAND From this point, New York City may be reached by continuing northward on Richmond The route follows Forest .Avenue and Road to Baint George; the ferry trip from Manor Road to Todt Hill Road. there to the Battery gives one of the finest views of the skyline of the lower part of Stop 9 is on the top of the terminal the city. A more direct route to points moraine of the Wisconsin glacier of Pleisto­ up-state is to return by way of Kill Van cene age west of Dongan Hills. To the left, Kull bridge to Hudson Boulevard, and con­ the moraine swings eastward a.cross the tinue northward on United States Highw~ narrows at the lower end of New York Harbor 9W from Ridgefield. to f onn the backbone of Long Island. The­ barrier beaches of Coney Island and Rockaway Beach are on the south margin of the island. In the foreground, outwash plains extend into A few of the more important papers that a small drifless area that will be visited deal with the geology of the region are the next. The plain beyond is bordered toward us following: by a sea cliff; it is presum~bly underlain by Cretaceous sediments, for the drift to the Balk, R. Structure and Correlation of the south contains Cretaceous plant fossils; none Metamorphic Rocks of Southeastern New Yorlc: of the Cretaceous is exposed on Staten National Acad. Sci., Proc., Vol. 18, pp. Island. But a cross the lower bay in the 618-630 (1932) distance is Sandy Hook projecting northward Ball<:, R. The Cortland Series: Neues Jahr., from the Cretaceous and Eocene sediments of Beilage Bd, 58~.Abt B, pp. 243-308 (1927) the Atlantic Highlands. The terminal moraine Berkey, c. P. Geology of the New York City continaes southward on the right. (Catskill) Aqueduct: N. Y. s. M., Bull. 146, Berkey, c. P. and Rice, Marion. Geology of Continuing on the road to Grant City, a the West Point Quadrangle: N. Y. s. M., quarry in the Staten Island serpentine will Bull. 225-226. be evident on the right, and farther along, Colony, R. J. Some Problems of the Schune­ the serpentine is exposed on each side o.f the munk Area: N. Y. S. M., Bull. 267, p. 26 ff. road. The route continues to the Richmmnd Fettke, C.R. The Manhattah Schist of Road and turns sharply to the left. Southeastern New York: N. Y. Acad. Sci., Annals, Vol. 23, pp. 193-260 (1914) Stop 10, west of the Richmond Road in Holzwas~er, F. Geology of Newburgh and Vi­ Grant City, gives a good exposure of the dinity: N. Y. S. M., Vull. 270. Staten;Island serpentine. The weathering of Johnson, D. w. Stream Soulpture on the At­ this rock has produced limonite; locally this lantic Slope: Columbia Univ. Press (1931). iron-bearing rock was an important source of Lewis, J.V. Palisade Diabase of New Jersey: iron in earlier days. The serpentine has .... American Jour. Soi.l 4th ser., vol. 26, I been formed as a result of the alteration of pp. 155· - 162 (1908} basic igneous rock, perhaps basalt. Occa- Merrill, F. J. H. and ott~ers. New York City Folio: U. s. G. S., Folio 83 (1902) Sharp, Henry s. A pre-Newark Peneplane and its bearing on the origin of the Lower Hudson Figure 7. Valley: American Jour. Soi., 5th ser., Vol. E• theria ovata Lea 18, p. 509ff (1929). (af'ter Jones) Guidebook 9, International Geological Con­ gress, Washington, 1933 (by c. P. Berkey, R. J. Colony, G. I. Finlay and others).

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