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THE NEW JERSEY COASTAL PLAIN AND ITS RELATIONSHIP WITH THE BALTIMORE CANYON TROUGH RICHARD K. OLSSON Department of Geological Sciences Rutgers University, New Brunswick, New Jersey Introduction The coastal plain of New Jersey lies along the western the trough and does not extend beneath New Jersey, edge of the Baltimore Canyon Trough, a large sedimen­ tary basin which extends along the United States Middle Overlying the limestone sequence (Figs. 2,3) are upper Atlantic states (Fig. 1), Tne Baltimore Canyon Trough 1 urassic and lower Cretaceous nonmarine and shallow extends seaward beneath the continental shelf to the up­ marine sandstones and shales (Poag, 1979). These per continental slope. A westward extension of tHe sediments thin beneath New Jersey and lie upon trough forms the Salisbury Embayment of New Jersey, crystalline basement rock. Where penetrated in wells Delaware~ Maryland and eastern Virginia. The Raritan they appear to be nonmarine in character although they Embayment of northern New Jersey and Long Island is a shallow embayment. The South Jersey High separates these two embayments of the trough. The Baltimore Canyon Trough is composed of a seaward-thickening wedge of Mesozoic and Cenozoic sedimentary rocks which overlie a warped and faulted crystalline base­ ment. The sediments that lie within the New Jersey Coastal Plain were deposited west of the main hinge line of deposition. Seaward of the hinge line the sedimentary rocks of the Baltimore Canyon Trough thicken to at least 14 km (Poag, 1979). In contrast the maximum thickness of sediments in the New Jersey Coastal Plain is less than 2 km in tHe Salisbury Embayment. The sediments in the Baltimore Canyon Trough were initially deposited when North America and Africa separated during early Mesozoic time. The sediments (Figs. 2,3) that accumulated in the Baltimore Canyon Trough consist of limestones, sandstones, sands, shales, and clays (Poag, 1979). Diapir structures noted in geophysical profiles (Grow, 1980; Schlee and Grow, 1980) along the continental slope suggest evaporite ATLANTIC OCEAN deposition occurred in the early phases of continental separation. A deeply buried thick sequence of limestone of Jurassic and Early Cretaceous age is identified in NC multi-channel seismic reflection profiles of the trough o 30 60 and a carbonate bank or reef thought to represent the ! ! ! lower Cretaceous shelf edge is postulated to lie beneath miles the present day upper continental slope. Limestones of late Jurassic and early Cretaceous age were penetrated Fig. 1 Outline map of the Baltimore Canyon Trough and its rela­ in the basal portion of the COST B~3 weB which was tionship to the New Jersey Coastal Plain. Location of drilled on the continental slope off New Jersey. The COST B-2 and B-3 wells is shown. The hatchered mark limestone sequence is confined to the deeper portions of shows location of natural gas discoveries. PERIODS COASTAL PLAIN COASTAL PLAIN MA COST COST STAGES OUTCROP SUBSURFACE B-2 WELL B-3 WELL 10 MIOCENE 20 30 OL IGOCENE 40 SOCEOCENE ______ _ 60 PALEOCENE MAASTRICHTIAN ~~~~~~ 70 CAMPANIAN 80 SANTONIAN CONIACIAN 90 TURONIAN CENOMANIAN ALBIAN APTIAN BARREMANIAN OXFORDIAN r{{{:l CONTINENTAL a ....... ~SHELF COASTAL MARINE 1....:------1 SLOPE Fig. 2 Diagram showing distribution of the continental, coastal marine, shelf, and slope facies in time. Data on COST B-3 well is taken from Poag, 1980, FIELD STUDIES OF NEW JERSEY GEOLOGY AND GUIDE TO FIELD TRIPS 118 TERTIARY CRETACEOUS JURASSIC TRIASSIC REDBEDS S VOLCANICS CONTINENTAL CRUST 100 km R. K. OLSSON. 1980 Fig. 3 Cross-section through Coastal Plain and Baltimore Canyon Trough modified after Schlee and Grow, 1980. have not been thoroughly studied. The upper tion of faulted basins in which continental sediments ac­ Cretaceous and Tertiary marine sequence that forms the cumulated. As continental separation began and the in­ major part of the New Jersey coastal plain belongs to a itial opening of the Atlantic occurred evaporite en­ marine cycle that began during Aptian time and trans­ vironments formed during the Late Triassic and Early gressed over the Atlantic margin, bringing sea level over Jurassic. Some of the rifted basins continued to receive the New Jersey area for the first time since the Atlantic continental sediments during Early Jurassic time. This began to open. early stage of development was accompanied by exten­ sive volcanism consisting of intrusive and extrusive The sediments that were deposited in the coastal plain placement of basaltic and dioritic rocks, of New Jersey consist of fluvial sands, gravels, and varigated clays; coastal deposits of beach~ lagoon, As circulation within the developing Atlantic Ocean marsh~ and related deposits; inner shelf sediments con­ became less restricted during Jurassic time carbonate sisting of shoreface sands with characteristic environments developed with bank and reef growth. Ophiomorpha trace fossil assemblages and offshore Fluvial sediments were deposited over the Triassic rifted micaceous clay and silty thinly bedded fine sands; mid basins landward of the carbonates. During Jurassic to and outer shelf clay glauconite sands and glauconitic Early Cretaceous time as the Atlantic continued to clays, often extensively burrowed; and slope deposits widen the carbonate bank and reef complex prograded composed of calcareous clays and silts. The formations seaward over the oceanic basement (Fig.3). In the of these various facies were deposited during major coastal plain area extensions of the Baltimore Canyon cycles of sea level change and are genetically related to Trough developed as embayments. These embayments, sedimentary units that have been penetrated in the the Salisbury and Rflritan embayments, which are prob­ COST B-2 and B-3 wells in the Baltimore Canyon ably fault bounded, received thicker sequences of Trough. The relationship of the New Jersey formations Jurassic and Lower Cretaceous fluvial sediments. In to the units penetrated in these wells will be discussed in Late Jurassic and Early Cretaceous time shallow marine the section on lithologic units. incursions began to extend landward of the carbonate complex (Fig. 3). Geological History of Coastal Plain and Baltimore Canyon Trougb A major cycle of sea level rise began during Albian time and in the Cenomanian seas spread into the coastal A general sequence of events based upon subsurface plain area for the first time (Fig. 3). This cycle of sea studies (Figs. 2,3) in the New Jersey coastal plain, data level rise ended the deposition of carbonate sediments from the COST B-2 and B-3 wells, .seismic reflection along the Lower Cretaceous shelf edge. The carbonates profiles, and seismic refraction studies can be con­ now lie beneath the present upper continental slope. The structed for the Baltimore Canyon Trough and the adja­ rise of sea level which began during Albian time lasted cent New Jersey coastal plain (Grow, 1980; Poag, 1979, until the Turonian before being interrupted by a 1980; Schlee and Grow, 1~80; Sheridan, 1979). moderate faU in sea level. Nevertheless~ renewed rise in sea level continued during the latter part of Late The separation of North America and Africa began Cretaceous time. The Late Cretaceous stratigraphy of during the Triassic yvith extensive drifting and forma- the coastal plain was controlled by individua.l cycles 119 COASTAL PLAIN AND THE BALTIMORE CANYON TROUGH within this major .rise of sea level. The deposition of environmental analysis. As such the Vail curve should marine sandt silt, and clay sifted with each sea level cy­ be regarded as a first approximation in achieving a cle. universal curve of sea level change in the geologic record. Changes in sea level continued to influence deposition . during the Paleocene and Eocene. During tne Late Figures 4,5, and 6 show the record of sea level change in Cretaceous and Paleocene sediments accumulated in the coastal plain and the Baltimore Canyon Trough. shelf environments of aeposition in the coastal plain The magnitude of sea level rise and fall is estimated on and for the most part in the Baltimore Canyon Trough paleontologic criteria, chiefly foraminifera. It can be except in its most distal part. During the Early Eocene, observed that in many places there is general agreement however t bathyal environments of deposition extended with the timing of sea level cycles shown on the Vail into the coastal plain (Fig. 3). The Eocene shelf and curve but not necessarily with the magnitude or slope profile appears to have been very gradual with no character of each cycle. Of note (Fig. 6) is the record of distinct shelf edge. Shelf deposition was reestablished in the upper Eocene and Oligocene which differs the coastal plain during the middle Eocene time and significantly from that of Vail and others in that the rna· bathyal conditions retreated further out, in the jor lowering of sea level occurs in the lower Oligocene Baltimore Canyon Trough. Late Eocene shelf deposi­ where they show a major rise in sea level. tion occurred over most of the Baltimore Canyon Trough and may have extended into the coastal plain, Lithologic Units although upper Eocene sediments are missing there. Jurassic At the end of Eocene time a major lowering of sea level occurred and the entire Baltimore Canyon Trough Nonmarine coarse sandstone and red and green shale was subjected to erosion. Sea level rose during Late of probable Jurassic age lie upon crystalline basement Oligocene time and the sea transgressed across an erod­ beneath New Jersey. Similar rocks intercalated with ed and beveled surface into the coastal plain area. marine shale were penetrated in the COST B-2 well where a thick Jurassic section is present. Carbonate During. Miocene time clastics prograded over the sediments are present further to the east in the COST Baltimore Canyon Trough and constructed the present B-3 well and in lower intervals in the Baltimore Canyon shelf and edge profile (Fig.

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