Physiographic diagram showing the major geological ... · PDF filePhysiographic diagram showing the major geological provinces in ... during the opening of the Iapetus Ocean, ... NJ.1

Geology of New Yorkand New JerseyJ Bret Bennington and Charles MerguerianHofstra University

View of the tiltedand eroded edge ofthe Palisades intru-sive sheet in NewJersey as seen fromInwood Hill Park onthe east bank ofthe Hudson River,New York City.

New York–New Jersey

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Over one-and-a-half billion years of geologic history are recorded in the landformsand rocks found within 100 kilometers of New York City, revealing multiple episodesof plate collision and orogeny, continental rifting, volcanism, and an ever-changingtableau of environments from tropical seas to glaciated landscapes. This bookletexplains the geologic events that have shaped the eastern continental margin ofNorth America, and also discusses the economic resources and geohazards of theNew York–New Jersey metropolitan region.

Coverage extends from western Connecticut to southern New Jersey and spans theAtlantic Coastal Plain westward across the metamorphic Piedmont provinces, NewarkBasin, Proterozoic Highlands, Appalachian Fold Belt, and Paleozoic Plateau regions.

Written to illustrate basic concepts of plate tectonics and rock formation presented inintroductory geology and physical geography courses, the Geology of New York andNew Jersey is appropriate for courses aimed at both majors and non-majors wherediscussion of the geologic history of the northeast will make the course content moreregionally relevant for the students. Incorporate this content with any Thomson EarthScience text, including Physical Geology: Exploring the Earth, 6th edition, by Monroe,Wicander and Hazlett. To learn more please visit: www.thomsonedu.com/earthscience.

Also AvailablePeople often decide on their residence or business location based on a desire to liveor work in scenic environments without understanding the hazards around them.Thus, a series of reprinted chapters from Donald and David Hyndman’s NaturalHazards and Disasters has been carefully selected to provide students with theopportunity to see how specific natural hazards are relevant to their regional area.

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To learn more about Natural Hazards and Disasters by Donald and DavidHyndman, please visit: http://earthscience.brookscole.com/hyndman.

90630_Geo_NY_NJ_Cover.qxd 9/4/06 5:15 PM Page 1

Physiographic diagram showing the major geological provinces in southeastern New York, northern New Jersey, and adjoining states.Numbers correspond to figure numbers in the text and show approximate geographic locations of photos.

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ESSENTIAL QUESTIONS TO ASKNew York–New Jersey.1 Introduction

� What duration of time and what geological eras are recorded in rocks of the New York–New Jersey region?

� What are the names of convergent orogenic events that took place during this time interval?

New York–New Jersey.2 Ancient Roots of the Grenville Orogeny� The Grenville Orogeny was part of the assembly of a Proterozoic supercontinent. What is

the name of the supercontinent?� Name five places within 100 miles of New York City where geologists and students can

study rocks of the Grenville Orogeny.

New York–New Jersey.3 Carbonate Seas and the Taconic Orogeny� What types of sedimentary layers were deposited during the opening of the Iapetus Ocean,

before the start of the Taconic Orogeny?� Identify at least five rock types formed during the Taconic Orogeny.� Which geological province contains the metamorphic roots of the ancient Taconic

Mountains? Which geological province preserves the sediments eroded off of the risingTaconic Mountains?

New York–New Jersey.4 Assembly of a Supercontinent� The assembly of supercontinent Pangaea took roughly 250 million years and involved a

collision between North America and what two other landmasses?� What tectonic environment and what life-forms existed during deposition of the

Helderberg Group of formations in the Early Devonian Period?� After the deposition of the Helderberg limestones, what change took place in the sediments

being deposited in the New York–New Jersey region and to what tectonic event can they beattributed?

New York–New Jersey.5 Breakup of Pangaea� During early Mesozoic time, the split up of Pangaea resulted in the formation of elongate

rift basins along the eastern margin of North America. Name a place on Earth todaywhere modern rift valleys are forming.

� In the New York–New Jersey–Connecticut region, name three Mesozoic basins and thetypical rock types you might find in them.

New York–New Jersey.6 Creation of the Atlantic Coastal Plain� Creation of the Atlantic Coastal Plain mirrors conditions that existed in eastern North

America at other times in the past. Name at least two earlier intervals of time whenpassive margin conditions existed along the coast of North America.

� What ages and types of sediments are common in coastal plain strata, and what kinds offossils are found in them?

New York–New Jersey.7 Ice Age Landscapes� Global cooling and the formation of glaciers took place during the Pleistocene Epoch.

Name three features each of glacial erosion and glacial deposition found in the New York–New Jersey region.

� Glacial deposits have produced major landforms and topographic features in the New York–New Jersey area. Name at least three examples of these.

New York–New Jersey.8 Economic Mineral Resources� Name a dozen economic mineral resources that have been mined for hundreds of years in

the New York–New Jersey–Connecticut region.� The Franklin Furnace District of northwestern New Jersey has been a rich source of metals.

Name the main ore minerals from this area and the metals that are extracted from them.

New York–New Jersey.9 Geological Hazards of the Region� Name three types of geological hazards associated with the New York–New Jersey area.� Why are moderate earthquakes, which cause little damage in West Coast cities such as

Los Angeles, such a potential danger for East Coast cities such as New York and Newark?

© 2007 Thomson Brooks/Cole, a part of the Thomson Corporation. Thomson, the Star logo, and Brooks/Cole are trademarks used hereinunder license. ALL RIGHTS RESERVED. No part of this work covered by the copyright hereon may be reproduced or used in any form or byany means—graphic, electronic, or mechanical, including photocopying, recording, taping, Web distribution or information storage andretrieval systems—without the written permission of the publisher. The Adaptable Courseware Program consists of products and additions toexisting Brooks/Cole products that are produced from camera-ready copy. Peer review, class testing, and accuracy are primarily the responsibilityof the author(s). The Geology of New York Tri-State Area /Charles Merguerian and J Bret Bennington - First Edition ISBN 0-759-39063-0.Printed in the United States of America.

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New York–New Jersey.1IntroductionVolcanoes, high mountains, earthquakes, and other indicatorsof active geological upheaval are currently associated with thewestern United States. By contrast, the eastern margin of thecontinent seems relatively quiet, but this was not always thecase. The New York–New Jersey metropolitan region lies onthe edge of the North American continent and has experi-enced a long history of geological activity as eastern NorthAmerica collided with other tectonic plates and then riftedapart again. The products of these tectonic interactions—geological structures and rock formations—are exposed inthe landscape beneath our feet. Geologists reconstruct thehistory of the Earth by mapping, collecting, and analyzing therocks, minerals, fossils, and geological structures preserved indifferent geological provinces. What is remarkable aboutNew York and New Jersey is that, within a 100-kilometer(60-mile) radius of New York City, eight major geologicalprovinces are present (Figure NY-NJ.1) that display morethan 1 billion years of geological history (Figure NY-NJ.2).The remnants of tropical seas, volcanic eruptions, deepmagma intrusion, rising mountains, shifting faults, andadvancing glaciers are all on display and ready to be appreci-ated by anyone with a basic knowledge of geology and a littleimagination. This chapter reviews the geological featuresthat are found in the New York–New Jersey metropolitanregion and relates the geological features of the present land-scape to the events that formed them in the past. We also dis-cuss the economic benefits, as well as the hazards, affordedby the geology of this region.

All rocks have a story to tell. One of the greatest scientificachievements of the twentieth century was the discoverythat there is a unifying theme to the stories found in rocks—the theory of plate tectonics. The lithosphere of the Earthis broken up into discrete plates that are created at mid-ocean ridges and move across the surface of the planet untilthey are consumed along deep ocean trenches. Because ofplate tectonics, continents and ocean basins are not staticfeatures of the Earth; rather, they are constantly moving andchanging through time. As tectonic plates separate, a conti-nent may be rifted apart and a new ocean basin can growbetween the diverging plates. Where plates converge, oceanbasins shrink as seafloor is subducted and recycled back intoEarth’s mantle. Plate convergence eventually brings conti-nental landmasses into collision, resulting in orogeny—theuplift and formation of a mountain range. This sequence of

2 New York–New Jersey Geology of New York and New Jersey

Proterozoic

Cambrian

Ordovician

Silurian

Devonian

Mississippian

Pennsylvanian

Permian

Triassic

Cretaceous

540

510

439

408

360

290

146

65

323

245

205

Ma

Grenville Orogeny1.1-1.0 Ga

Taconic Orogeny

Acadian Orogeny

Alleghenian Orogeny

Rifting of Pangea

Rifting of Rodinia Supercontinent

Opening of the Iapetus Ocean

Iapetus Oceanbegins to close

Opening of the Atlantic Ocean

Pangea Supercontinent

Tectonic Setting Geologic Event

Closing of thenorthern Iapetus

Closing of thesouthern Iapetus

2Quaternary Pleistocene Epoch

(Ice Age)

NY-NJ.2GrenvilleHighlands

NY-NJ.3ManhattanProng / TaconicAllochthon / GreatValley

NY-NJ.4

NY-NJ.5NewarkBasin

NY-NJ.6Atlantic CoastalPlain

NY-NJ.7

Rifting Divergence Convergence Collision

Province

Tertiary

Jurassic

Pal

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esoz

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Cen

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ManhattanProng /Allegheny-CatskillPlateau

Valley andRidge

Valley andRidge

� Figure NY-NJ.2 Geological timescale showing the sequence oftectonic settings and geological events that can be interpreted fromthe rocks found in different geological provinces in New York andNew Jersey.

� Figure NY-NJ.1 Physiographic diagram showing the major geo-logical provinces in southern New York, northern New Jersey, andadjoining states.


tectonic events—rifting, divergence, convergence, andorogeny—forms a repeating geotectonic cycle of thebreakup and re-formation of supercontinents (this makessense: on a finite Earth, continents can only diverge so muchbefore they begin to converge on the opposite side of theglobe). In New York and New Jersey, rocks preserve evi-dence for four major tectonic collisions and resulting oroge-nies, as well as one major rifting event (see Figure NY-NJ.2).The oldest of these collisions, the Grenville Orogeny, waspart of an older geotectonic cycle that culminated in theassembly of an ancient supercontinent named Rodinia dur-ing the Proterozoic Eon (see Figure NY-NJ.2). Later, afterRodinia rifted apart, an ocean basin called the Iapetusformed adjacent to eastern North America as tectonic platesdiverged. Eventually, this ocean basin began to close as plateconvergence commenced during the Appalachian geotec-tonic cycle. The three younger collisions (the Taconic,Acadian, and Alleghenian Orogenies) were part of the clos-ing of the Iapetus Ocean basin and the formation of themost recent supercontinent, called Pangaea, during thePaleozoic Era (see Figure NY-NJ.2). During the MesozoicEra (the so-called Age of Reptiles), Pangaea rifted apart anda new ocean basin, the Atlantic, formed along the easternmargin of North America. The Atlantic Ocean basin contin-ued to widen through the rest of the Mesozoic andCenozoic Eras as seafloor spreading along the mid-AtlanticRidge moved Africa and Europe progressively farther awayfrom the Americas.

The high mountains pushed up during past orogenies arenow long gone, worn down to their roots by tens to hun-dreds of millions of years of uplift, weathering, and erosion.The modern mountains of the region, such as the Ramapo-Hudson Highlands, the Taconic Range, the AdirondackMountains, and the Catskill Mountains, have been carved byerosion into the ancient rock (Figure NY-NJ.3). Many of themodern topographic features of northern New Jersey and

New York were created during the last ice age, less than100,000 years ago, as kilometer-thick continental ice sheetsflowed over the region, sculpting the bedrock and depositingmassive quantities of gravel, sand, and mud. The rock for-mations in New York and New Jersey produced by ancienttectonic events include historically important mineraldeposits of iron, zinc, and copper. Also present are thousandsof faults that crisscross the bedrock of the region, some ofwhich remain active and capable of generating the occasionalmoderate earthquake. Finally, as a coastal region, metropoli-tan New York–New Jersey is vulnerable to the destructiveeffects of wind, waves, and storm surge generated by hurri-canes and nor’easters.

New York–New Jersey.2 Ancient Roots of the Grenville Orogeny 3

� Figure NY-NJ.3 High up in the Catskill Mountains, rock layers arehorizontal, showing that the Catskill Mountains have been carved intothe bedrock, which is relatively undisturbed. Road cut along NY Route23A, near Palenville, New York.

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New York–New Jersey.2Ancient Roots of the GrenvilleOrogenyThe oldest bedrock found in New York and New Jersey ispart of an elongate belt of high-grade metamorphic rockcalled the Grenville Province buried beneath the easternmargin of North America (Figure NY-NJ.4). Radiometricdating of minerals within these rocks yields an age of meta-morphism of around 1.1 billion years ago (Ga) and sourcematerial ages that reach back to greater than 1.8 Ga. Largeregions of high-grade metamorphic rock, such as schist,gneiss, marble, and amphibolite, are produced when tectonicplates converge, bringing continental crust into collision toproduce a high mountain range. As the crust compresses andthickens in the collision zone, rock beneath the rising peakssubsides to great depth and is subjected to intense heatand directed pressure (stress) over millions of years. TheGrenville Province represents the roots of a high mountainrange that formed along the eastern margin of NorthAmerica as an older geotectonic cycle drew to a close, bring-ing another continent into collision with North America.The identity of the other continent is uncertain, but recentgeological research suggests that a fragment of SouthAmerica called Amazonia is the most likely candidate.

Although buried beneath much younger rock and sedi-ment in most places, Grenville rock can be studied becauseyounger plate tectonic collisions have folded and faulted theolder bedrock, bringing it to the surface in several regions.

Section New York–New Jersey.1 Summary● A long record of geological events impacting the easternmargin of North America, from the Proterozoic to the lastPleistocene ice age, is preserved in the rock formations ofthe New York–New Jersey metropolitan region.

● Four discrete episodes of tectonic collision resulting inorogeny and one episode of tectonic rifting are preservedin the rocks of this region.


The geology within the Grenville Highlands is a com-plex mixture of metasedimentary and metaigneous rocktypes, all highly deformed and cut by numerous faults.These rocks record a 300-million-year history of plate con-vergence and collision associated with the GrenvilleOrogeny (see Figure NY-NJ.2). The high grade of meta-morphism and extreme structural complexity of the rocks,combined with a relative lack of exposure in the humidnortheast (indeed, rocks are easier to study in arid environ-ments where soils are thin and plants are scarce), have


� Figure NY-NJ.4 Map showing the extent of both buried andexposed Grenville metamorphic rock in eastern North America, includ-ing named Grenville massifs.

� Figure NY-NJ.5 Folded and faulted Fordham Gneiss exposed inthe wall of the excavation for the Queens Water Tunnel, New YorkCity Water Tunnel #3. Note the folded gneissic layers and the dis-tinct brittle fault running diagonally across the center of the image.

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The Fordham Gneiss is folded within younger, EarlyPaleozoic age metamorphic rock of the Manhattan ProngProvince and can be seen exposed in the Bronx in New YorkCity and along I-287 in Westchester County. Tunneling forNew York City’s water supply has also revealed the FordhamGneiss in the subsurface of Brooklyn and Queens, beneathwestern Long Island (Figure NY-NJ.5). The largest region ofGrenville rock in the Tri-State area (northern New Jersey,southern New York, and western Connecticut) forms a north-east trending terrain called the Reading-Ramapo-Hudsonmassif, or simply the Grenville Highlands. This province isan extension of the Blue Ridge province to the south and theBerkshire and Green Mountain provinces to the north (seeFigure NY-NJ.4). Isolated regions of Grenville Highlandscalled the Housatonic massif and the Athens and Chesterdomes can be found in northwestern Connecticut andVermont. In New York State, the Adirondack Mountains areetched into a roughly circular region of Grenville-agebedrock that is currently being pushed upward by tectonicforces. Erosion has stripped away the younger layers of sedi-mentary rock to reveal the older metamorphic rock in theAdirondack region. Some of the rock of the high peaks regionof the Adirondack Mountains is composed of metamorphosedanorthosite, a peculiar igneous rock formed almost exclu-sively of plagioclase feldspar (Figure NY-NJ.6).

� Figure NY-NJ.6 Outcrop of anorthosite in the AdirondackMountains, NY Route 3 near Saranac Lake, New York. Note thelarge, elongate crystals of bluish gray twinned plagioclase feldspar.

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New York–New Jersey.3 Carbonate Seas and the Taconic Orogeny 5

� Figure NY–NJ.7 Strike-slip fault valley, Harriman State Park, Hudson Highlands, New York. The ridge in the foreground on the right is the sameas the ridge in the background on the left, but both ridge segments have been displaced by horizontal movement along a fault. Grenville rocks aretypically glacially sculpted, as shown by the rounded ridge profiles in this view.

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presented a challenge to geologists trying to decipher thedetails of the Grenville orogenic event. Recent geologicalmapping in the Hudson Highlands has found evidence forthe development of a subduction zone off the east coast ofNorth America at about 1.2 Ga, leading to collisions with avolcanic island arc and another continent by 1.02 Ga.This was followed by episodes of igneous intrusion, andfinally by strike-slip faulting (Figure NY-NJ.7) and rapiderosion to produce the Grenville Province, the ancestralroots of the Appalachian Mountains.

Section New York–New Jersey.2 Summary● The metamorphic bedrock of the Grenville HighlandsProvince in New York, New Jersey, and New England wasformed during a plate tectonic collision between NorthAmerica and Amazonia, more than 1 Ga ago. Grenville-agerock underlies much of eastern North America.

● The Grenville Orogeny took place during the assem-bly of supercontinent Rodinia, near the end of theProterozoic Eon.

New York–New Jersey.3Carbonate Seas and theTaconic OrogenyAlthough recognized only locally in the New York–NewJersey area, geological evidence for rifting and the breakupof Rodinia hundreds of millions of years after the uplift of

the Grenville Mountains can be seen in the Blue Ridgeregion of Maryland, Virginia, and North Carolina. In theNortheastern United States the eroded roots of theGrenville Mountains are directly overlain by formationssuch as the Potsdam Sandstone and the Lowerre andPoughquag Quartzite, composed of layers of shoreline sandsand gravels deposited as sea level rose and flooded easternNorth America near the beginning of the Paleozoic Era.Five hundred million years of time go unrecorded, markedonly by a nonconformity between the older metamorphicrock and the younger strata. During the Cambrian Period,shallow seas covered much of the North American conti-nent, then situated astride the equator. Initially, as plate tec-tonic motions opened up the Iapetus Ocean basin, uplift andtectonic activity were absent from eastern North America,resulting in a passive continental margin. A warm, tropicalclimate and the absence of eroding mountains created idealconditions for the growth of the marine organisms that pro-duce limestone, allowing an enormous thickness of carbon-ate rock (Figure NY-NJ.8) to accumulate in a broadcarbonate platform (a modern example would be the GreatBarrier Reef in Australia). Farther offshore, away from thecarbonate platform, terrigenous muds accumulated in thedeeper water away from the margin of the continent. By theend of the Cambrian Period, a dislocation in the seafloor offthe coast of North America created a subduction zone. TheIapetus Ocean basin stopped widening and began to close asthe continent and the oceanic plate began to converge bythe process of subduction. Volcanism associated with thesubduction zone formed a volcanic island archipelago, simi-lar to modern-day Indonesia. As subduction continued, thisvolcanic landmass was brought into collision with NorthAmerica beginning in the Middle Ordovician, causing theTaconic Orogeny (Figure NY-NJ.9).


Evidence for the Taconic Orogeny can be seen in the rocksexposed in the Manhattan Prong, Great Valley, and TaconicAllochthon geological provinces (see Figure NY-NJ.1). Infact, the Taconic Orogeny is more completely representedthan any other in the Tri-State region. In the vicinity of NewYork City and western Connecticut, much of the bedrock ismedium- to high-grade metamorphic rock, produced in thecrustal roots of the Taconic Range, where sedimentary layers

deposited earlier were caught between the colliding land-masses. Sandstones and limestones of the carbonate platformwere metamorphosed into quartzite and marble (for example,the Lowerre Quartzite and Inwood Marble of New York City,the Woodville Marble of Connecticut, and the StockbridgeMarble of Massachusetts), whereas offshore mudstones weretransformed into schist (the Manhattan Formation exposedin parts of New York City) and the sedimentary layers ofmudstone and graywacke associated with the volcanic islandarc were changed into schist, granofels, and amphibolite ofthe Hartland Formation of Manhattan, the Bronx, and west-ern Connecticut (Figure NY-NJ.10). A major geologicalboundary called Cameron’s Line, mapped through the mid-dle of the Manhattan Prong, separates metamorphic rocksassociated with the North American continent from thoseassociated with the colliding volcanic island arc. Cameron’sLine is a ductile shear fault within an accreted subductionzone (suture)—an illustration of how continents grow overtime as tectonic collisions weld new segments of crust totheir margins.

In addition to metamorphism, convergent orogenies haveother important geological effects. Adjacent to the axis ofmountain building, sedimentary layers are shoved, causingthem to fold and move along thrust faults. In some cases,large regions of existing rock may be displaced by many kilo-meters, forming an allochthon. During the TaconicOrogeny, offshore shales deposited adjacent to NorthAmerica were pushed westward on top of the rocks of thecarbonate platform, resulting in the Taconic Allochthon.The modern Taconic Mountains along the east side of

the Hudson River in New York arecomposed of slates, phyllites, andschists that were displaced as muchas 100 kilometers and metamor-phosed in a former subduction zone(see Figure NY-NJ.10). The crustalthickening associated with the for-mation of a mountain range canalso cause the formation of a fore-land basin on the continent as theweight of the orogen (mountain belt)depresses the adjacent crust. (A use-ful analogy is to imagine a bowlingball placed on a mattress—the bowl-ing ball protrudes above the mattresswhile at the same time depressingthe mattress around it.) As the risingmountains weather and erode, thegravel, sand, and mud producedbecome deposited in the adjacentforeland basin. During the earlystages of the Taconic Orogeny, enor-mous quantities of sediment weretransported westward, accumulatingas thick deposits of sandstone, silt-stone, graywacke, and shale, now


� Figure NY-NJ.8 Shallow-water platform carbonates exposedin the Cambro-Ordovician Wappinger limestone, Wappinger Falls,New York.

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� Figure NY-NJ.9 Diagram illustrating the change in the continental margin of eastern NorthAmerica from a passive margin to a converging plate boundary, leading to a collision with a vol-canic island arc during the Taconic Orogeny.


exposed as the Martinsburg (Pennsylvania and New Jersey)and Normanskill Formations (New York) in the Great ValleyProvince (see Figure NY-NJ.10). Toward the end of theTaconic Orogeny, these strata were also shoved by tectonicforces, causing folding, uplift, and erosion of the layers to theeast and even metamorphism of some of the strata closer tothe orogen.

New York–New Jersey.4 Assembly of a Supercontinent 7

� Figure NY-NJ.10 Three examples of Ordovician rocks deformedduring the Taconic Orogeny.

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Section New York–New Jersey.3 Summary● Passive margin conditions at the beginning of thePaleozoic Era led to the deposition of nearshore sandsand gravels and shallow-water carbonates in New Yorkand New Jersey. Deposition of carbonates ended with theinitiation of the Taconic Orogeny, a collision betweeneastern North America and a volcanic island arc.

● Evidence for the Taconic Orogeny can be found in themetamorphic rock of the Manhattan Prong and TaconicAllochthon, and in the sedimentary rock of the GreatValley Province.

New York–New Jersey.4Assembly of a SupercontinentThe Taconic Orogeny marks the first of three collisions thatimpacted eastern North America during the closing of theIapetus Ocean basin, culminating in the assembly of super-continent Pangaea. Evidence for the later two orogenies inthe Tri-State region can be seen in the rocks of theManhattan Prong, Valley and Ridge, and Allegheny-CatskillPlateau provinces (Figure NY-NJ.11). Following the TaconicOrogeny, weathering and erosion leveled the mountains,creating a surface of unconformity across the region (Fig-ure NY-NJ.12). In the Late Silurian Period, rising sea levelagain flooded the eroded eastern margin of North America.Coastal river systems draining now-vanished uplands to theeast carried vast quantities of quartz gravel and sand, deposit-ing them along the shoreline to form the extensive conglom-erate and sandstone layers of the Shawangunk-KittatinnyFormation. Today, these formations underlie a prominentridge (Figure NY-NJ.13) marking the eastern edge of theValley and Ridge Province that extends from southeasternNew York (the Shawangunk Ridge) south through NewJersey (Kittatinny Mountain) and Pennsylvania (BlueMountain). By the Late Silurian Period and into the EarlyDevonian Period, deposition of sand gave way to limestoneformation as tropical marine waters covered much of NorthAmerica. This temporary return to passive margin conditionsallowed the development of another carbonate platformacross eastern North America, leading to the deposition ofthe Helderberg Group of carbonate formations. Helderberglimestones outcrop along the western edge of the Valley and

Refolded folds of foliation in schist and granofels of the HartlandFormation, Central Park, New York City.

Refolded slaty cleavage in greenish slate and siltstone of the Taconicsequence exposed along Dutchess County Road 21, Noxon, New York.

Inclined blackish gray shale and graywacke of the NormanskillFormation exposed in Johnson-Iorio Park, Highland, New York.

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Ridge and along the margin of theAllegheny-Catskill Plateau. Fossilsof brachiopods, crinoids, stromato-poroids, and corals are abundant inthese Devonian limestones. Anabrupt shift from passive margin tocollisional tectonics in the MiddleDevonian is shown by a changefrom shallow-water carbonate rocksto deep-water shales, marking theonset of the Acadian Orogeny.Closure of the northern IapetusOcean in the Devonian broughtnorthern Europe, Greenland, andNorth America into collision. In theNew England region, a small conti-nental landmass named Avaloniacollided, pushing up high moun-tains. As the Acadian mountainsweathered and eroded, vast quanti-ties of terrigenous sediments were

transported southwestward by rivers and deposited into aforeland basin across New York, New Jersey, andPennsylvania. Today, the thick sequence of layers of con-glomerate, sandstone, and mudstone produced from thesesediments is exposed in the Allegheny-Catskill Plateau.Middle Devonian marine strata changed over to LateDevonian terrestrial red beds (see Figure NY-NJ.3) as theforeland basin filled to sea level with sediment. Even if geolo-gists had no evidence of Acadian metamorphism from NewEngland, they would still recognize the Acadian Orogenyfrom the enormous pile of eroded sediment shed from theseancient mountains. Tectonic activity associated with theAcadian Orogeny continued into the Mississippian Period.Although there are few Mississippian-age strata present in theNew York–New Jersey region (they are present inPennsylvania and farther south), Devonian- to Permian-ageigneous intrusives are found in the Manhattan Prong.

The final closure of the southern Iapetus Ocean occurredduring the Pennsylvanian and Permian Periods, when west-ern Africa and eastern North America collided during theAlleghenian Orogeny. This is primarily a southern event,shown by metamorphism, folding, thrust faulting, and thedeposition of enormous quantities of eroded terrigenous sed-iment in Pennsylvania, Maryland, Virginia, West Virginia,and farther south. In the New York–New Jersey region,the only apparent evidence for the Alleghenian Orogeny isthe folding of the older rock layers seen in the Valley andRidge and evidence for deep burial of the Devonian strata inthe Appalachian-Catskill Plateau. Although Pennsylvanian-age sediments shed from the rising Alleghenian Mountainsprobably did once cover New York State, they subsequentlyeroded away. Also missing from the Tri-State region are anyrocks deposited during the Permian Period. By this time,supercontinent Pangaea was formed and seafloor spreadingslowed, which led to a drop in global sea level and emergenceand erosion across much of eastern North America.


� Figure NY-NJ.11 Illustration showing the rock types and record of tectonic events preservedin a cross section of the Hudson Valley region. Compare with Figure NY-NJ.12.

� Figure NY-NJ.12 Taconic angular unconformity exposed at NewYork State Thruway approach road, NY Route 23, Leeds, New York.Note the vertically inclined Ordovician shale and greywacke truncatedby dipping Silurian and Devonian carbonate strata. Late in the TaconicOrogeny, sediments shed from the Taconic Mountains were upliftedand eroded down to a flat surface. After submergence during theLate Silurian and Early Devonian Periods, carbonate sediments weredeposited above the Taconic erosion surface. Eventually, during theAlleghenian Orogeny, the entire sequence was uplifted and tilted tothe west. Compare with Figure NY-NJ.11.

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New York–New Jersey.5 Breakup of Pangaea 9

� Figure NY-NJ.13 Prominent topographic ridge formed by Silurian Shawangunk Conglomerate.

Section New York–New Jersey.4 Summary● After the Taconic Orogeny, passive margin conditionsreturned to eastern North America, resulting in reneweddeposition of limestone. Subsequently, two other tectoniccollisions occurred as the Iapetus Ocean fully closed dur-ing the assembly of supercontinent Pangaea.

● Evidence for the Acadian Orogeny is seen in the thickpile of eroded terrigenous sediments preserved in therocks of the Appalachian-Catskill Plateau. Evidence forthe Alleghenian Orogeny is found in the folding of olderrock layers seen in the Valley and Ridge Province.

New York–New Jersey.5Breakup of PangaeaAt the close of the Paleozoic Era, the Earth’s continentswere assembled into a single supercontinent called Pangaea.Starting early in the Mesozoic Era, Pangaea began to frag-ment as upwelling mantle heat initiated rifting along thesutures formed between the original continents. By theLate Triassic Period, Africa was in the process of riftingaway from eastern North America and the opening of themodern Atlantic Ocean basin had begun. Extension of thecrust near and along the suture between the two continentscaused the formation of a series of elongate rift valleys(Figure NY-NJ.14) similar to those that are forming inEast Africa today. These rift valleys filled with sedimentdistributed by vast river systems and with basaltic lavaflows. At depth, mantle-derived mafic intrusives were

invading the rift basin fill. As the basins formed, they spreadaway from the active (mid-Atlantic) ridge and are nowpreserved as discrete geological regions along the marginof eastern North America from South Carolina toNewfoundland. Mesozoic rift basins in the Tri-State regioninclude the Newark Basin in northern New Jersey and theHartford Basin extending through central Connecticut and

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� Figure NY-NJ.14 Map showing locations of Triassic-Jurassic riftbasins along the eastern margin of North America.

AAddaapptteedd FFrroomm:: Figure 2.17a from Monroe-Wicander-Hazlet, Physical Geology, Sixth Ed. (2007).

a View of Shawangunk Ridge looking south from Lake Mohonk,New York.

b View south across the Delaware Water Gap, New Jersey.



Massachusetts. These two basinshave similar geological features andmay once have been continuousacross the Manhattan Prong, an ideasupported by the presence of thesmall Pomperaug Basin in westernConnecticut. The Ramapo-HudsonHighlands border the Newark Basinto the east along the Ramapo borderfault (Figure NY-NJ.15). Duringthe Triassic and Jurassic Periods, themetamorphic bedrock beneath theNewark Basin tilted downwardalong this fault, creating an elongaterift valley to the east. Rivers drain-ing the bordering highlands fed intothe basin, depositing conglomeratesand sandstones as huge fans and aslandslide deposits. Because the basinwas a closed depression, large riftlakes filled the center of the basinduring times of wet climate, onlyto dry up during intervals of aridclimate. Sediments deposited in therift lakes included shoreline silt-stones and deep-lake black shales.Dinosaurs roamed the lakeshores,leaving behind a copious fossilrecord of footprints and trackways.Fossils of freshwater fish and aquaticreptiles are also found in Mesozoicbasin shales. Deposition of sedi-mentary rock in both the Newarkand Hartford Basins continued wellinto the Early Jurassic Period,when both basins also experiencedprotracted volcanic and intrusiveigneous activity. Mantle-derivedmagma rising within the rift zoneintruded the previously depositedsedimentary layers, cooling withinthe strata to form sheets of diabaserock. The Palisades Cliffs bordering the east side of theNewark Basin along the Hudson River (see cover photo)are formed from the eroding edge of a large intrusive sheetof diabase (the West Rock diabase in Connecticut is a simi-lar feature). Some magma also reached the surface of thebasin to erupt, forming extensive flood basalt flows. Theprominent Watchung Hills in northern New Jersey areelongate ridges formed of tilted, erosion-resistant basalticlava (Figure NY-NJ.16). Three time-separated episodes oferuption produced the three Watchung lava flows withinthe Newark Basin. The cooled flows were subsequentlyburied beneath younger sedimentary layers, and the entiresequence of rock was gradually tilted to the west by contin-ued subsidence along the Ramapo fault. (Except for the factthat the rocks dip eastward, a mirror image of this sequence

� Figure NY-NJ.15 Geological cross section of the Newark Basin from the Ramapo fault border-ing the Ramapo Highlands eastward to the nonconformity above metamorphic rocks of theManhattan Prong.

� Figure NY-NJ.16 Stacked Early Jurassic lava flows of the Orange Mountain Basalt exposed atthe Great Falls of Paterson, New Jersey. Here, at the Paterson Gap, the Passaic River has exploiteda fault in the basalt to erode a short canyon, creating the waterfall. Locate the position of thisphoto on the diagram in Figure NY-NJ.20.

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Section New York–New Jersey.5 Summary● Rifting and separation of Africa from eastern NorthAmerica began in the Triassic Period as the superconti-nent of Pangaea began to break up. Rift basins preservedfrom this event are exposed along the margin of NorthAmerica, including the Newark Basin in New Jersey andthe Hartford Basin in Connecticut.

● Rift basin geology includes sedimentary rocks depositedby rivers and lakes, fossil dinosaur trackways, and diabaseintrusive sheets and basalt lava flows.

of sedimentary and volcanic strata exists within the HartfordBasin.)


New York–New Jersey.6Creation of the AtlanticCoastal PlainContinued rifting of North America from Africa in theJurassic Period culminated in the development of a new mid-ocean ridge system and the eruption of new seafloor crustbetween the previously joined continents. Deep in the subsur-face of the eastern continental margin are buried rift valleys,evaporite deposits, and marine reefs that record the gradualopening of the modern Atlantic Ocean basin. As it was at thebeginning of the Paleozoic, eastern North America became adeeply eroded, tectonically quiescent passive margin. As theAtlantic Ocean basin grew wider, the seafloor lithosphereattached to the edge of the continentcooled and contracted into the man-tle, which induced down-warping ofthe margin of North America toform a broad continental shelf. Themodern coastal plain is essentiallythe inner region of the continentalshelf that is currently exposed abovesea level. The history of the AtlanticCoastal Plain is one of depositionand the accumulation of sedimentduring times of high global sea leveland exposure and erosion duringtimes of low global sea level. Assediments are carried by rivers tothe coast, gravels, sands, and mudsare deposited in nearshore to off-shore environments on the conti-nental shelf. Continuing tectonicsubsidence lowers the surface of theshelf, creating space for new sedi-mentary layers. Thus, over the past150 million years, a thick pile of sed-imentary strata has accumulatedalong the margin of eastern NorthAmerica. These strata are tilted sea-ward because subsidence of theouter continental shelf occurs at ahigher rate than the inner continental shelf. During times oflow global sea level, such as the present, the coastal plain isexposed to erosion, with older Cretaceous deposits exposedalong the northwest side of the coastal plain and progressivelyyounger Tertiary deposits exposed to the southeast side(Figure NY-NJ.17). The topography of the coastal plain isgenerally flat, and most exposures of strata are found alongstream banks and coastal cliffs. Also, because the sediments ofthe coastal plain were never deeply buried beneath overlyinglayers, they are compacted, but they have not been cementedinto solid rock (Figure NY-NJ.18).

During the Late Cretaceous Period, global sea level wasunusually high and eastern North America was flooded by theAtlantic Ocean well inland of the present shoreline. A lack of

red-colored minerals in dominantly light-colored Cretaceousstrata indicates no derivation from the erosion of NewarkBasin rocks and suggests that the shoreline during the LateCretaceous Period was located at least as far westward as theRamapo Fault. Cretaceous and Early Tertiary deposits of themodern inner coastal plain, such as the Navesinkand Hornerstown Formations, contain marine fossils (Fig-ure NY-NJ.19) and abundant glauconite, a mineral that iscurrently found forming in deep-water outer continental shelfenvironments. This also implies a Cretaceous shoreline manykilometers inland of its present position. As global sea leveldropped after the Miocene Epoch, the coastal plain wasexposed above sea level and began to erode. Moderately

New York–New Jersey.6 Creation of the Atlantic Coastal Plain 11

� Figure NY-NJ.17 Geological map and cross section showingthe age and succession of offshore-dipping sedimentary deposits ofthe Atlantic Coastal Plain. The younger strata rest above the Fall Zoneplanation surface, a nonconformity above crystalline bedrock.

� Figure NY-NJ.18 Late Cretaceous glauconite sands of the Navesink Formation exposed in thestream bank of Big Brook, near Marlboro, New Jersey. Note the compacted but unlithified natureof these 70-million-year-old sediments; shelly fossils, such as the ammonite in the center of thephoto, can easily be excavated with a trowel.

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erosion-resistant Cretaceous strataformed a low, tilted ridge called a cuestaalong the inner coastal plain. This cuestacontrolled the drainage pattern of riversflowing toward the coast. For example,the present course of the Hudson Riverwas blocked by the coastal plain cuesta,causing the Hudson to flow inlandacross the Newark Basin and to emptyinto Raritan Bay south of Staten Island(Figure NY-NJ.20). During the PlioceneEpoch, uplift and erosion removedmuch of the coastal plain strata north ofNew Jersey, allowing the Hudson Riverto shift to its modern drainage pathalong the nonconformity between theNewark Basin fill and the ManhattanProng (see Figure NY-NJ.1). TheSparkill Gap, a prominent wind gapthat follows a fault through the northernpart of the Palisades sheet, marks theplace where the Hudson once flowedbefore the shift took place. Although

covered by Quaternary glacial deposits, coastal plain strataextend northward beneath Long Island, where the thickCretaceous sands of the Magothy and Raritan Formations holdtrillions of gallons of fresh groundwater, providing irreplace-able drinking water aquifers for a large urban and suburbanpopulation.


� Figure NY-NJ.20 Block diagram showing blockage of the ancestral Hudson River by theinner coastal plain cuesta and the former path of the river through the Sparkill, Paterson, andMillburn Gaps across the Newark Basin to Raritan Bay. (Figure has been colorized from an origi-nal drawing of Johnson, 1931.) Johnson, D. W., 1931, Stream sculpture on the Atlantic slope, astudy in the evolution of Appalachian Rivers: New York, NY, Columbia University Press, 142 p.

� Figure NY-NJ.19 Fossil mosasaur tooth embedded in jawbonefragment from the Big Brook locality near Boundary Road, New Jersey.Mosasaurs were large marine lizards that hunted fish and other rep-tiles in the seas of the Late Cretaceous Period. Atlantic Coastal Plaindeposits often contain shelly marine fossils and the bones and teethof both marine and terrestrial animals.

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Section New York–New Jersey.6 Summary● The Atlantic Coastal Plain developed as the AtlanticOcean basin began to widen during the Mesozoic andthe edge of the North American continent subsided toform a continental shelf.

● During times of high global sea level, marine sandsand muds were deposited far inland of the present shore-line during the Cretaceous and Tertiary Periods. Thesedeposits are now being exposed by erosion in stream val-leys along the New Jersey Coastal Plain.

New York–New Jersey.7Ice Age LandscapesAlthough the bedrock of the New York–New Jersey region isancient, the modern features of the topographic landscapeare not. The mountains of the Grenville Highlands, theTaconics, the Catskills, and the Adirondacks are Quaternary-age features, etched by streams into landscapes rejuvenatedby mild tectonic uplift. In northern New Jersey, New York,and New England, the land has also been extensively modi-fied by glacial ice. During the Pleistocene Epoch of the


Quaternary Period, beginning about 2 million years ago,global cooling fostered a series of glaciations, each of whichsent immense continental ice sheets flowing southward fromCanada into the United States, only to melt back duringwarmer interglacial periods. Each glacial advance and retreatsculpted the landscape, modifying or erasing the features leftfrom the previous glaciation. The modern northern land-scape is largely a product of the Wisconsinan glaciation,which began about 100,000 years ago, peaked at 20,000 yearsago, and ended 10,000 years ago (although glacial depositsand landscape features from at least as many as two olderglaciations are preserved in some places). Advancing conti-nental glaciers flowed approximately from north to south andmodified the landscape by carving, polishing, and pluckingthe soil and bedrock they passed over. The thickness of theWisconsinan ice sheet was likely more than a kilometer overcentral New York and at least half a kilometer over northernNew Jersey, and the great weight of the glacier fractured therock below as the ice completely covered the region, fillingthe valleys and completely burying the mountain peaks.Evidence for glaciers overwhelming the Pleistocene topogra-phy can be seen on the bedrock surfaces at the top of theAdirondack Mountains in New York and at High Point innorthwestern New Jersey. Exposed rock surfaces aresmoothed and polished, giving outcrops a rounded look thatgeologists refer to as roche moutonée (French meaning“fleecelike rock”). Linear grooves and striations carved byice-embedded rock fragments being dragged beneath theglacier are common features on outcrop surfaces, as arechattermarks, crescentic fractures caused by the weight ofthe ice on the bedrock (Figure NY-NJ.21). Flowing glacialice carved deeply into preexisting stream valleys, wideningtheir profiles into a distinctive U-shape. Glacially excavatedvalleys and land surfaces also contain a multitude of depres-sions that form natural lakes and ponds. New York andnorthern New Jersey, which were completely glaciated, havethousands of natural lakes. By comparison, Virginia, whichwas not glaciated, has only two natural lakes.

Glaciers are also significant agents of deposition. Meltingglacial ice releases enormous quantities of sediment excavatedfrom the land, from huge boulders to minute particles ofclay and rock flour. Erratics, large boulders transported byglaciers, are common features of northern landscapes.Glacial deposits (drift) can be divided into two main types(Figure NY-NJ.22). Till is an unsorted mix of particle sizescombining boulders, sand, and clay that is released directlyin contact with melting ice. Stratified drift or outwash issorted and layered sediment that is transported away fromthe ice by flowing meltwater. Glaciated landscapes are typi-cally mantled with a combination of till and outwash thatoften fills glacially carved valleys. The Finger Lakes of cen-tral New York are north-south trending, U-shaped, glacialvalleys that are dammed at their southern ends by glacialsediments. The lower reach of the Hudson River is a fiord, aglacially carved valley that is flooded by the sea. However,the river itself is only a fraction of the depth of the HudsonValley, most of which is filled in with glacial drift. Till thataccumulated beneath the flowing glacier was sculpted into

New York–New Jersey.7 Ice Age Landscapes 13

� Figure NY-NJ.21 Features associated with recently glaciatedlandscapes.

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a Bedrock at the top of Bear Mountain, New York, rounded into rochemoutonée form. Also visible are chattermarks, faint striations, anda small erratic boulder of Silurian Green Pond Conglomerate, whichindicates that the ice flowed from the northwest.

b Glacially striated bedrock surface in Central Park, New York City,New York.

c Large erratic boulder of igneous bedrock plucked from the floor ofLong Island Sound and deposited on the north shore of LongIsland near Sound Beach, New York.


Moraine continues along the southeastern coast of StatenIsland and joins with the Bangor Moraine in northern NewJersey. Erosion of the moraines by waves has stranded thou-sands of erratic boulders along the north shore of Long Island.North of the Harbor Hill Moraine, the landscape is cut by aseries of short, steep-sided valleys that terminate along themargin of the moraine. Most of these are tunnel valleys,carved beneath the ice sheet by flowing streams of subglacialmeltwater. Several large tunnel valleys form harbors betweenthe necks of land on the western north shore of Long Island.South of the moraines on Long Island are flat, gently slopingoutwash plains composed of stratified deposits of outwashsand and gravel. The moraines themselves are composed of acombination of till, stratified drift, and in the Harbor HillMoraine, large blocks of the underlying Cretaceous coastalplain strata that were bulldozed in front of the advancing ice.The landscape of the moraines is an irregular mix of knobbyhills and depressions called kame and kettle topography,formed as pockets of rock debris within the glacier were

released alongside blocks of iceburied in drift as the ice front wastedaway. Kettle ponds are also commonfeatures in valleys of northern NewJersey and New York that hostdeposits of glacial drift. An interest-ing feature of kettle ponds is thatthey sometimes contain the bones ofextinct ice-age mammals. Skeletonsof mammoths and mastodons, twospecies of extinct North Americanelephant, continue to be found onoccasion in New York and NewJersey. Despite almost a billion yearsof geological history, the ultimate


streamlined, tear drop–shaped hills called drumlins. Swarmsof north-south–oriented drumlins are present in the HudsonValley and south of Lake Ontario in western New York.

Glacial sediments accumulated at the southern margin ofthe ice sheet, where rock and sediment were delivered by flow-ing ice and then released by melting, piling up to form a linearhill called a moraine. The moraine that marks the farthestextent of ice advance is the terminal moraine, and morainesthat form during pauses in the retreat of an ice sheet are reces-sional moraines. Long Island is a large glacial deposit made upof a combination of till and outwash deposited as a series ofmoraines resting on top of older coastal plain sediments. Thetwin forks at the eastern end of Long Island are formed fromtwo of the moraines, the Roanoke Point Moraine and theRonkonkoma Moraine (Figure NY-NJ.23). A third moraine,the Harbor Hill Moraine, truncates the RonkonkomaMoraine and extends along the northwestern third of LongIsland and may or may not be an extension of the RoanokePoint Moraine to the east. To the west, the Harbor Hill

� Figure NY-NJ.22 Comparison of two major types of glacial drift.

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� Figure NY-NJ.23 Digital elevation model of Long Island showing the three major moraines,outwash plains, and tunnel valleys.

a b Stratified drift (outwash)—poorly to well sorted layered pebbles and sandexposed at the west end of Caumsett State Park, Long Island, New York.

Till—an unsorted mixture of boulders, gravel, sand, and mud exposedat the east end of Caumsett State Park, Long Island, New York.


New York–New Jersey.8 Economic Mineral Resources 15

Section New York–New Jersey.7 Summary● The landscape of northern New Jersey, New York, andNew England was modified extensively by glacial ice dur-ing the Wisconsinan glaciation. Glaciers carve and erodethe landscape as they advance and also create distinctivelandforms by depositing sediment when they melt.

● Glacial striations, roche moutonée, and erratics arecommon glacial features in the region. Long Island iscomposed of several glacial moraines and outwash plains.

New York–New Jersey.8Economic Mineral ResourcesMany types of economic mineral deposits, including iron,zinc, cement, building stone, and aggregate (crushed rock,gravel, and sand), have been mined and quarried in the NewYork–New Jersey region going back to colonial times. On asmaller scale, emery, copper, cobalt, mica, clay, and feldsparwere also mined. Except for limestone, trap rock, sand, andgravel, mining has ceased in this region because of the discov-ery of richer, more economic sources of ore elsewhere, orbecause of environmental considerations. Iron mining inConnecticut began in 1658 by exploiting deposits associatedwith igneous rock in the Hartford Basin near East Haven.The large-scale extraction of iron ore in northwesternConnecticut began in 1762. Starting by 1710 in Whippany,New Jersey, iron was mined in the metamorphic rock of theGrenville Highlands, exploiting ores of limonite, magnetite,and hematite. Hundreds of small pits and prospects line thehills of the Ramapo-Hudson Highlands through New Yorkand New Jersey (Figure NY-NJ.24). In the late 1700s, manyof these mines supplied iron for the Continental Army.The Colonial forges were situated in valleys underlain byfolded Paleozoic carbonate rocks in the highlands or in theGreat Valley and Valley and Ridge provinces northwest of thehighlands, where access to abundant wood, running water, andlimestone (for flux) made it possible to smelt the highland oresinto pig iron. During the Revolutionary War, the Americansplaced iron chains and booms across the Hudson River to pre-vent the British Navy from using the river to divide the north-ern and southern colonies. One of these was the great ironchain strung across the river at Fort Montgomery in NewYork. The remains of the Fort Montgomery chain can be seenat the Bear Mountain Lodge, located at the base of BearMountain in the Hudson Highlands.

Nestled among the hilly areas of northwest New Jerseyare the globally unique Franklin (Mine Hill) andOgdensburg (Sterling Hill mine) zinc-iron-manganese oredeposits. These deposits have yielded nearly 300 different

� Figure NY-NJ.24 The Black Ash Iron prospect in the ProterozoicHudson Highlands in New York is typical of the hundreds of small mag-netite prospect pits found throughout the Ramapo-Hudson Highlands.

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minerals, roughly 10% of all known minerals and a numbervastly greater than from any other single region in theworld. Amazingly, more than 60 of these minerals exhibitfluorescence or phosphorescence when illuminated byultraviolet light (Figure NY-NJ.25). Four minerals consti-tute the primary ore group: franklinite (a spinel-type oxidemineral of zinc, manganese, and iron), willemite (a zinc sili-cate), zincite (a zinc-manganese oxide), and calcite, much ofwhich contains manganese. Franklinite and zincite, abun-dant in the Franklin area, have been found in only traceamounts elsewhere. Both of these famous zinc mines arenow closed. The last ore was lifted from the Franklin Minein 1954 and at Sterling Hill in 1987. Fortunately, the site ofthe Franklin Mine now hosts the Franklin MineralMuseum, and the nearby Sterling Hill Mine has been pre-served as it was when mining ended. At Sterling Hill, inaddition to seeing one of the world’s largest collections offluorescent minerals, visitors can tour the mine buildingsand walk through the upper level of the mine itself to expe-rience mining an ore body from inside of the Earth.

Concrete is composed of sand and gravel held togetherby cement. In Rosendale, New York, located in the Valleyand Ridge Province north of Poughkeepsie, a cementindustry sprang to life in 1825, when deposits of Siluriandolostone and limestone were found to offer a source ofnatural cement (Figure NY-NJ.26). These cement stoneswere quarried because the dolomitic layers contain just theright amount of quartz silt to make cement when roasted.Rosendale cement provided much of the cement for con-struction in New York City in the late 1800s and was usedin many famous public structures, including the founda-tions and piers of the Brooklyn Bridge, the base of theStatue of Liberty, the Treasury Building in Washington,DC, and the Kensico and Ashokan Reservoir dams of theNew York City water supply system. By 1910, theRosendale cement industry was made obsolete by the devel-opment of the Portland cement process, which can use

development of our northern landscape is largely the resultof glacial erosion, deposition, and the work of running waterliberated in the end stages of Pleistocene glaciation.


roads and making concrete. Specific examples of regionalsources of building stone and aggregate are as follows:

● Pleistocene Glacial Drift: construction fill and sandfor concrete

● Mesozoic arkose sandstone (Newark, Pomperaug, andHartford Basins): building stone (“brownstones”) usedextensively in Philadelphia, New York, and New Haven

● Mesozoic diabase: crushed aggregate (trap rock) forroads and railway beds

● Paleozoic shales: construction fill and road metal● Paleozoic marble and limestone: building stone● Proterozoic and Paleozoic granites: building stone


� Figure NY-NJ.25 Extraction of the Sterling Hill ore was aided by using ultraviolet light in the mining process to sort the different mineral phases.Manganiferous calcite, one of the associated gangue minerals, fluoresces bright orange. Willemite, a valuable ore mineral, fluoresces bright green.

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� Figure NY-NJ.26 Rosendale cement was mined using the roomand pillar method wherein the roof of the mine is supported by pil-lars of unmined rock. Abandoned mines such as the one picturedhere are common in the Rosendale-Tillson area of New York. Severalmines are now used as underground storage facilities for corporatedocument archives and for mushroom farms.

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more common and voluminous Devonian limestones. Eventoday, barges loaded with Portland cement travel up anddown the Hudson River from cement mines near Kingston,Catskill, Hudson, and Ravena, New York.

Although unglamorous, the single most economicallyvaluable type of rock is building stone and aggregate.Quarried rock is used for building stone and decorative fac-ing (for example, polished marble or granite), and crushedrock, gravel, and sand (aggregate) are used for building

Section New York–New Jersey.8 Summary● Although most mining has now ceased in the Tri-Stateregion, historically important deposits of iron, zinc, cop-per, and manganese were mined beginning in the 1600s.

● Quarrying of rock and sediment for cement, concrete,aggregate, and building stone continues to be an impor-tant economic activity in the region.

New York–New Jersey.9Geological Hazards of the RegionThe New York–New Jersey metropolitan region is locatedalong a passive continental margin with low mountains and nomajor forms of active tectonism. Unlike the West Coast, the

a bOre body viewed in white light. Ore body fluorescing in ultraviolet light.


East Coast does not experience frequent, large earthquakes orsubduction-induced volcanism. But this does not mean thatthe East Coast is free of geological hazards. The historicalrecord of seismicity in the East does show that significantearthquakes do occur, they just do not occur very often relativeto the span of human experience. The crystalline bedrock thatunderlies the eastern margin of North America is cut bynumerous brittle faults, most of which are potentially active.Some of these faults have had a discernible impact on themodern topography. For example, New York City is cut by amultitude of steep north-northeast–trending faults of probableMesozoic age and a set of younger northwest-trending brittlefaults. The Manhattanville fault at 125th Street underlies abroad U-shaped valley, and another one of the northwest-trending faults, the 14th Street fault, has lowered the bedrocksurface, creating a subsurface valley filled with glacial drift.Because of the expense of anchoring tall buildings in uncon-solidated sediments, the average height of the buildings islower in the area of Manhattan between 23rd and Canalstreets, creating the familiar dip in the Manhattan skylinebetween Midtown and the Financial District (Figure NY-NJ.27). Although earthquakes generated by movement alongthese faults are rare events, the historical record shows thatthey do happen. The New York metropolitan region experi-enced three earthquakes of approximately magnitude 5 on theRichter scale in the 1700s and 1800s (Figure NY-NJ.28).More recently, in 2001, two earthquakes with magnitudes near2.5 occurred in Midtown and upper Manhattan. Althoughsmall relative to seismic events in California, an earthquake ofmagnitude 5 occurring in present-day Manhattan would havepotentially catastrophic effects, particularly for older buildings,

New York–New Jersey.9 Geological Hazards of the Region 17

� Figure NY-NJ.27 Aerial view of the Manhattan skyline showing how building height is controlled by the subsurface geology. In the FinancialDistrict (left center) and Midtown (right of center), buildings are taller because they can be anchored in bedrock that is nearer the surface. Inbetween, the buildings are shorter because the bedrock surface drops along faults, creating a valley that has been glaciated and filled with uncon-solidated glacial sediments, which are not good for supporting tall buildings.

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� Figure NY-NJ.28 Map of historical seismicity in the New YorkCity region. All earthquakes greater than 3.0 on the Richter magnitudescale are plotted. Locations for older earthquakes are approximate.The three largest earthquakes recorded are estimated to have been5.2 (1884), 5.2 (1737), and 4.9 (1783), and all are reported to havegenerated enough shaking to knock over chimneys and open largecracks in the ground. Equivalent shaking today would likely shatterglass windows in skyscrapers, rupture water mains as soils liquefied,and cause some failure of older masonry walls.


Hurricanes are notorious for bearing destructive winds, butless appreciated (at least before the impact of Katrina onNew Orleans) is the devastating flooding that hurricanesoften cause. Storm surge generated by winds piling waterup against the coastline causes coastal flooding, and high-volume rainfall produces inland flooding. The damage doneby coastal flooding is magnified by the fact that the coast-lines and barrier islands of the Northeast have experienced ahuge surge in population and infrastructure over the pasthalf century. Barrier island communities such as Long Beachin New York and Atlantic City in New Jersey are also partic-ularly vulnerable because of rising sea level. Recent globalsea level rise has been estimated to be about 15 cm (6 inches)per 100 years, whereas sea level rise at Atlantic City has beenmeasured to be 38 cm (15 inches) per 100 years. The higherrate of sea level rise in the New York–New Jersey region islikely due to sinking of the coastline caused by tectonic sub-sidence or the compaction of sediments beneath the coastalplain. In any case, rising sea level makes barrier islandsand coastlines more vulnerable to storm waves and coastal


� Figure NY-NJ.29 Map showing tracks of hurricanes that have impacted the coast of New York and New Jersey from 1900 to 2005. The mostdestructive storm was the so-called Long Island Express, which struck eastern Long Island and New England in 1938. This storm was a Category 3with 121 mph sustained winds and a northward velocity of 70 mph when it crossed Long Island. Parts of eastern Long Island, western Connecticut,and Rhode Island were devastated, with 700 people killed and more than 8,000 homes destroyed. (Base map courtesy of National Oceanic andAtmospheric Administration)

which lack modern reinforcement. Another potential prob-lem during a moderate earthquake is the liquefaction of soilsand unconsolidated sedimentary fill. Many buildings alongthe shoreline of Manhattan Island are constructed on fill andmay experience amplified shaking during a moderate earth-quake. The infrastructure of cities in the Northeast is notengineered to withstand earthquake motion as it is on theWest Coast, because most people do not recognize earth-quakes as a hazard. However, it is sobering to consider thatthe Charleston, South Carolina earthquake of 1886 was mag-nitude 7.2 and completely destroyed that city, which is locatedin a geological setting (passive continental margin withancient, deformed crystalline rocks beveled beneath coastalplain strata) very similar to that of New York City.

The same warning given for earthquakes can also beapplied to hurricanes. Although the Northeast coast is notimpacted by hurricanes as much as the Florida or Gulfcoasts, the historical record shows that the New York–New Jersey metropolitan region has experienced significant,destructive hurricanes in the recent past (Figure NY-NJ.29).


flooding. This was dramatically illustrated on Long Island in1992–1993, when winter storms caused a quarter-milebreach in the barrier island at Westhampton, opening achannel between Moriches Bay and the Atlantic Ocean anddestroying more than 80 homes (Figure NY-NJ.30).Repairing the breach and restoring the sand to allow thehomeowners to rebuild cost the taxpayers of New Yorkalmost $50,000,000. This cost, however, would pale incomparison with the expense and destruction of a major hur-ricane strike on the New York–New Jersey coast, an eventthat has happened in the past and will happen again. Similarto earthquake hazard, it is only a matter of time.

Review Workbook 19

� Figure NY-NJ.30 Photos of the breach in the Fire Island barrier beach at Westhampton, New York, caused by winter storms in 1992–1993.U.

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Section New York–New Jersey.9 Summary● The New York–New Jersey region has an historicalrecord of moderate earthquake events and thus shouldbe considered a seismically active area. A damagingearthquake will eventually occur in this area.

● This region also has a history of damaging hurricanesand other coastal storms. The combination of a surgingcoastal population and rising sea level will amplify thedamage and loss of life during the next significant hurri-cane event.

b View of the final quarter-mile breach with Moriches Bay and thesouth shore of Long Island in the background.

a Although still standing in the photo, these homes were quicklyclaimed by the sea as waves eroded the sand supporting them.

Review WorkbookESSENTIAL QUESTIONS SUMMARYNew York–New Jersey.1 Introduction� What duration of time and what geological eras are recorded in rocks ofthe New York–New Jersey region?More than a billion years of geological time are recorded in theregion, representing the Proterozoic Eon and Paleozoic, Mesozoic,and Cenozoic Eras.

� What are the names of convergent orogenic events that took placeduring this time interval?The Grenville, Taconic, Acadian, and Alleghenian Orogenies.

New York–New Jersey.2 Ancient Roots of the Grenville Orogeny� The Grenville orogeny was part of the assembly of a Proterozoic super-continent. What is the name of the supercontinent?The supercontinent was Rodinia.

� Name five places within 100 miles of New York City where geologistsand students can study rocks of the Grenville Orogeny.The Bronx, New York City water tunnels, Westchester, HudsonHighlands, Ramapo Mountains, and Housatonic massif.

New York–New Jersey.3 Carbonate Seas and the Taconic Orogeny� What types of sedimentary layers were deposited during the opening of theIapetus Ocean, before the start of the Taconic Orogeny?Initially, shoreline sands and gravels, then a thick accumulation ofcarbonates developed on the continental margin while offshore fine-textured terrigenous muds formed.

� Identify at least five rock types formed during the Taconic Orogeny.The rock types formed during the Taconic Orogeny included shale,graywacke, slate, phyllite, schist, gneiss, granofels, marble, andamphibolite.

� Which geological province contains the metamorphic roots of theancient Taconic Mountains? Which geological province preserves thesediments eroded off of the rising Taconic Mountains?The metamorphic rock of the Manhattan Prong includes the roots ofthe Taconic Mountains, whereas the Great Valley contains the sedi-mentary layers derived from the erosion of the Taconic Mountains.

New York–New Jersey.4 Assembly of a Supercontinent� The assembly of supercontinent Pangaea took roughly 250 million years andinvolved a collision between North America and what two other landmasses?The landmasses were Avalonia and Africa.


� What tectonic environment and what life-forms existed during deposi-tion of the Helderberg Group of formations in the Early Devonian Period?During Helderbergian time, a return to passive margin conditionsand warm tropical seas resulted in thick limestones bearing evidencefor brachiopods, crinoids, stromatoporoids, and corals, among otherancient life-forms.

� After the deposition of the Helderberg limestones, what change tookplace in the sediments being deposited in the New York–New Jerseyregion and to what tectonic event can they be attributed?Shallow-water carbonates were replaced by an accumulation of deep-water marine shale, then by conglomerate, sandstone, and shale of theAllegheny-Catskill Plateau in response to the Acadian Orogeny.

New York–New Jersey.5 Breakup of Pangaea� During early Mesozoic time, the split up of Pangaea resulted in the forma-tion of elongate rift basins along the eastern margin of North America. Namea place on Earth today where modern rift valleys are forming.Rift valleys are forming in the East Africa and the Afar-Red Sea area.

� In the New York–New Jersey–Connecticut region, name threeMesozoic basins and the typical rock types you might find in them.The Newark, Pomperaug, and Hartford Basins all contain arkosesandstone, siltstone, shale, and mafic igneous rocks of both intrusiveand extrusive origin.

New York–New Jersey.6 Creation of the Atlantic Coastal Plain� Creation of the Atlantic Coastal Plain mirrors conditions that existed ineastern North America at other times in the past. Name at least two earlierintervals of time when passive margin conditions existed along the coast ofNorth America.Passive margin shallow-water conditions existed during the LateCambrian to Early Ordovician and during the Early Devonian Periods.

� What ages and types of sediments are common in coastal plain strata,and what kinds of fossils are found in them?The Atlantic Coastal Plain strata consist of unconsolidated gravel, sand,glauconite, and mud from the Cretaceous, Tertiary, and QuaternaryPeriods. These strata contain the fossils of marine vertebrates andinvertebrates.

New York–New Jersey.7 Ice Age Landscapes� Global cooling and the formation of glaciers took place during thePleistocene Epoch. Name three features each of glacial erosion and glacialdeposition found in this region.Features of glacial erosion include glacial polish of rock outcrops,chattermarks, striations, and roche moutonée. Features of glacialdeposition include till, outwash, drumlins, and erratics.

� Glacial deposits have produced major landforms and topographic fea-tures in the New York-New Jersey area. Name at least three examplesof these.These major landforms and topography include Harbor HillMoraine, Ronkonkoma Moraine, Roanoke Point Moraine, BangorMoraine, tunnel valleys, and kame and kettle topography.

New York–New Jersey.8 Economic Mineral Resources� Name a dozen economic mineral resources found in the New York–New Jersey–Connecticut region that have been mined for hundreds of years.These mineral resources are iron, zinc, cement, building stone,aggregate, emery, copper, cobalt, mica, clay, feldspar, and gem-stones.

� The Franklin Furnace District of northwestern New Jersey has beena rich source of metals. Name the main ore minerals from this area andthe metals that are extracted from them.Franklinite, willemite, and zincite are the main ore minerals that haveyielded zinc, iron, and manganese.

New York–New Jersey.9 Geological Hazards of the Region� Name three types of geological hazards associated with the New York–New Jersey area.Hazards in the New York–New Jersey area include earthquakes,liquefaction, hurricanes, and coastal erosion.

� Why are moderate earthquakes, which cause little damage in WestCoast cities such as Los Angeles, such a potential danger for East Coastcities such as New York and Newark?The buildings and infrastructure of the East Coast have not beenengineered to withstand ground motion because a moderate earth-quake has not occurred in more than 100 years.


ESSENTIAL TERMS TO KNOWAggregate – loose geological material such as sand, gravel, orcrushed rock used as filler in concrete, asphalt, and other buildingmaterials, or as material for road and rail beds.

Allochthon – a mass of rock that has been moved from its place oforigin by tectonic forces.

Amazonia – a Paleozoic continental landmass that combined withother landmasses to form modern South America.

Anorthosite – a coarse-textured plutonic igneous rock composedalmost entirely of calcic plagioclase feldspar.

Aquifers – a body of rock or unconsolidated sediment capable ofholding and transmitting useful quantities of fresh groundwater.

Cameron’s Line – the boundary in the Manhattan Prong betweenthe Manhattan and Hartland Formations, interpreted as a deep-seatedshear zone formed at great depth during the Taconic Orogeny.

Chattermarks – crescent-shaped fractures found on the surface ofglacially polished bedrock that formed by point-load compressive fractur-ing of the bedrock by rock fragments carried within the base of a glacier.

Cuesta – a ridge with a gentle slope on one side and a steep slope onthe other.

Diabase – an intrusive igneous rock with the mafic mineral composi-tion of basalt, but with an interlocking texture intermediate to basaltand gabbro.

Dolostone – a sedimentary rock similar to limestone, but with thechemical composition CaMgCO3.

Drift – any sedimentary material transported and deposited by a glacier.

Erratic – a rock boulder plucked by glacial ice from bedrock andtransported to a different location.

Flood basalt – a large outpouring of basaltic lava covering hundredsto thousands of square kilometers, erupted over a relatively short spanof geological time.

Geological provinces – large regions with distinctive landscapesunderlain by rock units with similar formational, structural character-istics, or both, that relate to a common sequence of geological events.

Geotectonic cycle – a cycle of rifting, plate divergence, plate con-vergence, and collision during which a supercontinent breaks up, con-tinents drift apart, continents converge, and a new supercontinentre-forms on a timescale of 500 million years or longer.

Glauconite – an iron-rich micaceous mineral that forms light to darkgreen, sand-sized grains in sediment-starved marine environments.

Liquefaction – the temporary transformation of loose solid materialsuch as sand into a liquid mass due to seismic shaking.

Lithosphere – the outermost tectonic layer of the Earth consistingof the crust and the rigid upper mantle above the asthenosphere andcorresponding to the plates of plate tectonics.


Review Workbook 21

Massif – a massive topographic and structural feature commonlyformed of rocks more resistant to erosion than the surrounding area.

Nonconformity – a contact between metamorphic or igneous(crystalline) rock and overlying sedimentary rock that indicates a sig-nificant interval of time before deposition of the sedimentary rock,during which the crystalline rock was undergoing uplift and erosion.

Orogeny – the geological process of forming mountains.

Pangaea – the supercontinent that formed during the Late PaleozoicEra and that rifted apart during the Mesozoic Era.

Passive continental margin – a continental margin leading intoan ocean lacking plate boundary interactions and characterized by lowrelief and either carbonate sedimentation or low rates of accumulationof terrigenous sediments.

Red beds – sedimentary layers characterized by a distinct reddishcolor imparted by the presence of oxidized iron minerals, indicatingdeposition in an environment exposed to the atmosphere (such as afloodplain or perennial stream channel).

Rifting – the process of rupturing the lithosphere to create a newdivergent plate boundary.

Roche moutonée – a distinctive curled or fleecy shape imparted toexposures of bedrock that have been scoured and plucked by glacial flow.

Rock flour – finely pulverized rock that has not been extensivelychemically weathered, produced by abrasion at the base of a glacier.Deposits of wind-blown rock flour are called loess.

Rodinia – the supercontinent that formed during the MiddleProterozoic Eon and that rifted apart before the start of thePaleozoic Era.

Seismicity – the phenomena of earth movements and earthquakes.

Storm surge – a sudden, temporary rise in local sea level caused bystrong winds blowing water against the coast combined with thedecrease in atmospheric pressure associated with large hurricanes.

Striations – linear scratches that are oriented in the direction of iceflow, formed on the surface of glaciated bedrock as rock fragments aredragged at the base of the glacier.

Stromatoporoid – moundlike fossil organism common in shallow-water Paleozoic limestones. These were most likely a relative of livingsclerosponges, a group of sponges that form a mineral foundation fortheir living tissue.

Subduction zone – a convergent tectonic plate boundary wherethe oceanic lithosphere of one plate bends downward and sinks intothe mantle beneath the lithosphere of another plate.

Supercontinent – an agglomeration of several large continentallandmasses that result from plate tectonic convergence causing conti-nents to mass together on one side of the globe.

Terrigenous sediment – sediment such as gravel, sand, silt, andclay derived from the weathering and erosion of rock on a continent.

Thrust fault – low-angle fault produced during compressive tecton-ics that displaces one mass of crust physically above another.

Tunnel valley – steep-sided, anastomosing valley eroded intounlithified sediments at the base of a glacier by meltwater flowingthrough tunnels beneath the ice.

Volcanic island arc – a generally curved, linear volcanic landmassproduced by the generation and emplacement of magma above anactive subduction zone.

Wind gap – a gap in a mountain ridge originally eroded by a stream,but now elevated and dry.

Review Questions1. Why is the New York–New Jersey region a particularly good placefor geologists and students of geology to study the history of the Earth?

2. What are the four major collisional tectonic events that are recordedin the rocks of the New York–New Jersey region? Which geologicalprovinces contain the geological products of each event?

3. Which geological province in the region formed during a tectonicrifting event? What important geological features are produced dur-ing rifting?

4. What is a passive margin? What is the geological evidence for apassive margin, and which geological provinces in New York andNew Jersey contain evidence for passive margin conditions?

5. Where in the New York–New Jersey region can you find volcanicfeatures? What are these features and how did they form?

6. Which geological provinces are likely to contain fossils, and whichgeological ages are represented by fossils in each province?

7. What are the most common glacial features that can be observed inthe New York–New Jersey region? How did these features form?

8. What is the origin of Long Island? What are the major topographicfeatures of the landscape of Long Island?

9. What are the important economic mineral resources of theNew York–New Jersey region?

10. What are the two major geological hazards facing residents of theNew York–New Jersey metropolitan area?

1. Compile a sorted list of historic earthquakes of magnitude 2 orgreater in the New York–New Jersey area, with the largest earth-quakes listed first. List the date, location, and Richter scale magnitudefor each event. Use the Internet to find this information(http://www.ldeo.columbia.edu/LCSN/big-ny-eq.html).

2. How does the topography of the New York–New Jersey regiondepend on the underlying lithology (rock type) and geologicstructure?

Apply Your Knowledge Questions


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Physiographic diagram showing the major geological ... · PDF filePhysiographic diagram showing the major geological provinces in ... during the opening of the Iapetus Ocean, ... NJ.1