30. LATE CRETACEOUS AND CENOZOIC EVOLUTION OF THE NEW JERSEY CONTINENTAL SLOPE AND UPPER RISE: AN INTEGRATION OF BOREHOLE DATA WITH SEISMIC REFLECTION PROFILES1 C. Wylie Poag, U.S. Geological Survey, Woods Hole and Gregory S. Mountain, Lamont-Doherty Geological Observatory2 ABSTRACT Fifteen intersecting single-channel seismic reflection profiles and fifteen multichannel profiles are integrated with coring and downhole logging data from DSDP Sites 604, 605, 612, and 613 to interpret the stratigraphic framework and depositional history of the Campanian to Pleistocene deposits of the New Jersey Transect (Continental slope and rise). Twelve seismic and depositional sequences, each bounded by erosional unconformities, are recognized within the upper rise prism and 13 are recognized on the slope. All the slope sequences have been documented by drilling, but four on the rise have not been drilled, and their precise ages are unknown. Isopach maps delineate the distribution patterns and de- positional-erosional fabric of each sequence. The study area has been the locus of repeated episodes of massive down- slope sediment transport that have created extensive systems of erosional channels and have produced a downslope "ribbed" geometry for each sequence mapped. Our results show that most depositional and erosional features in the study area are equivalent to deposits and stratigraphic gaps previously documented on the adjacent shelf and coastal plain. Our interpretation of the sedimentary history is compatible with the Vail model of global sea-level change. INTRODUCTION This chapter presents refined interpretations of the multichannel seismic reflection lines (Fig. 1) and incor- Four nearly continuously cored boreholes on the New porates an additional series of high-resolution single- Jersey Continental Slope and Upper Rise, drilled by the channel seismic reflection profiles (Fig. 2), which in- Deep Sea Drilling Project (Sites 604, 605, 612, and 613; cludes crossings of (or near) the principal boreholes of Legs 93 and 95) permit us to interpret the detailed stra- the slope and rise. tigraphy of a grid of intersecting high-resolution single- The stratigraphic framework and facies relationships channel and multichannel seismic reflection profiles. Here- presented by Poag (1985b) apply to this study, although tofore, a few intermittently cored boreholes had been with some important modifications. Poag recognized 12 drilled on the continental slope (Poag, 1985a), but no depositional sequences on the upper rise. We have reas- boreholes had penetrated the upper rise. sessed those sequences, combining Poag's Sequence 5 On the basis of sparse previous data and a few surfi- (?lower Miocene?) with Sequence 4 (?middle Miocene), cial cores and grab samples, several authors have ana- and dividing Sequence 12 (Maestrichtian/Campanian) lyzed the seismostratigraphy and morphology of Neo- into two separate sequences. Renumbering from top to gene and Quaternary strata of the New Jersey Slope (Robb bottom still yields 12 sequences (Fig. 3), but below Se- et al., 1981; Prior et al., 1984; Poag, 1978, 1979, 1984, quence 4, the numbers are one digit smaller than Poag's 1985a; Hampson and Robb, 1984). Without benefit of (e.g., Poag's 8 is our 7). We also have treated the four boreholes on the upper rise, Tucholke and Mountain undrilled sequences (4, 5, 6, 7) more conservatively, gen- (1979), and Klitgord and Grow (1980), attempted to in- erally referring to them by number rather than by their terpret the general stratigraphic section there by long presumed (but undocumented) chronostratigraphic po- range correlations from distant deep-sea boreholes (e.g., sitions. DSDP Sites 105, 106, 388; Fig. 1). The Pleistocene sequence of the upper rise prism is Four studies have been carried out since the drilling subdivided into Unit A (upper) and Unit B (lower). Unit A by Legs 93 and 95 (van Hinte, J., Wise, S. W, Jr., et al., can be further subdivided into subunits A! (upper) and in press). Robb and Hampson (1983) surveyed the surfi- A2 (lower). cial geology of the upper rise. Poag (1985b) and Moun- tain and Tucholke (1985) presented divergent interpreta- DATA BASE AND ANALYTICAL METHODS tions of the deeper upper-rise stratigraphy, although they Many multichannel and single-channel seismic pro- and Farre (1985) agree rather closely on the the histori- files have been obtained over various parts of the study cal development of the continental slope. area by various institutions. Two relatively closely spaced, overlapping grids of intersecting lines constitute the chief Poag, C. W., Watts, A. B., et al., Init. Repts., DSDP, 95: Washington (U.S. Govt. components of this analysis. The first seismic grid con- Printing Office). tains 15 intersecting multichannel lines covering a 48- × 2 Addresses: (Poag) U.S. Geological Survey, Woods Hole, MA, 02543; (Mountain) La- mont-Doherty Geological Observatory, Palisades, NY, 10964. 140-km area at ca. 15- to 20-km spacings (Fig. 1). Ten of 673 C. W. POAG, G. S. MOUNTAIN USGS U.S. Geological Survey DSDP Deep Sea Drilling Project AMCOR Atlantic Margin Coring Project (Poag. 1985a BGR Bundesanstalt für Geowissenschalteπ und Rohstofl (German Geological Survey) MCS Multichannel Seismic Line KNORR Woods Hole Oceaπographic Institution Line / CONRAD Lamont-Doherty Geological Observatory Line _,/ ASP Atlantic Slope Project (Poag, 1985a) (_ Selected coastal wells Core holes Industry wells Fire Island Slaten Is. Rockaway Beach 40 60 80 100 kilo 20 30 40 50 πautica USGS Is. B AMCOR 6011 Maryland ESSO ®AMC0R 6008 Figure 1. Location of boreholes and grid of multichannel seismic profiles in the vicinity of the New Jersey Transect. these lines are unpublished, part of a joint U.S.G.S.- lected 15 of these single-channel lines (9 strike lines; 6 BGR (Bundesanstalt für Geowissenschaften und Roh- dip lines) for detailed analysis, including those that cross stoffe) program carried out in 1979 by Prakla Seismos or nearly cross the principal boreholes. (see Schlee and Fritsch, 1981, for collection and pro- The borehole control for this study is chiefly that de- cessing information). Three of the lines (25, 34, and 35) rived from DSDP Sites 604, 605, 612, and 613 (Figs. 1, are published U.S.G.S. lines that have been used as stan- 2; Poag, 1985b; Poag and Low, this volume). These are dard references for this area (Poag, 1985a, b). The re- supplemented by intermittently cored sites (ASP 14, 15; maining two lines, 2 and 6, are also published U.S.G.S. AMCOR 6021; Poag, 1985a), and by rotary cuttings from lines (see Schlee, 1981). A second grid consists of single- the COST B-3 well (Figs. 1, 2; Poag, 1980, 1985a). channel profiles obtained by the U.S.G.S. in 1978-1979 Thickness of strata on seismic lines (where not drilled) (Fig. 2). It covers a 40- × 35-km area with approximately was estimated using sonic velocity values from down- 900- to 1,700-m line spacing (Robb et al., 1981). We se- hole geophysical logs obtained at Sites 612 and 613 (see 674 EVOLUTION OF THE N. J. CONTINENTAL SLOPE 39°00' 38°55' 38°50 38°45' 38°40 38°35' 0 5 1 i i i i i km 38°30'N 72°50'W 72°45' 72°40' 72°35' 72°30' 72°25' 72°20' Figure 2. Location of boreholes and selected grid of single-channel seismic profiles (solid lines with ticks) in the vicinity of the New Jersey Transect. Four-digit numbers by ticks indicate hourly navigation marks and correspond to hour marks on the interpreted profiles. Key multichannel lines shown by dashed lines. Multichannel Line 34 (not shown) is nearly coincident with Line 89. Dotted Line CP3-B is a single-channel line recorded on Glomar Challenger during Leg 95 (see Site 612 chapter, this volume). ASP = Atlantic Slope Project; AMCOR = Atlantic Margin Coring Project; COST = Continental Offshore Stratigraphic Test (Poag, 1985a). 675 C. W. POAG, G. S. MOUNTAIN Upper-rise equivalents Characteristics of upper-rise sequences (Mountain & Tucholke) Widespread; chiefly terrigenous; displaced shelf faunas; reworked Eocene clasts, slope-front, onlap- and chaotic-fill; sampled at DSDP 604, 605, 612, 613; ASP 14, Pleistocene 1 5, AMCOR 6021; COST B-3. Widespread; chiefly terrigenous; reworked Eocene microfossils; upper surface channeled; -Blue- fills upper Miocene channels; onlap- and chaotic-fill; sampled at DSDP 604, 605, 612, 613. Widespread; chiefly terrigenous; reworked Eocene clasts, mildly channelled; fills channels on several older surfaces; slope-front, onlap-, and chaotic-fill, sampled at DSDP 604, 612, 613. Limited to NE study area; chiefly terrigenous ?; fills channels on several underlying sequences; severely eroded; onlap- and chaotic-fill; includes submarine fan facies; not sampled in upper rise DSDP sites, and possible updip equivalent (upper Miocene) not late Miocene? Limited to SW study area; chiefly terrigenous ?; thin sequence; severely eroded; slope- front fill, onlap-fill and submarine fan facies; not sampled in upper rise DSDP sites, but possible updip equivalent (middle Miocene) sampled at COST B-3, ASP 14, 15. Limited to SW study area; chiefly terrigenous ?; fills Eocene channels; severely eroded; on lap-, mounded onlap-, chaotic-fill and submarine fan facies; not sampled in upper rise DSDP sites, but possible updip equivalent (middle Miocene) sampled at COST B-3; .Ayjll^,.,^, ,,.-- ,.,,,,.,_. .^.--– Limited to SW study area; patchy distribution; chiefly terrigenous ? severely eroded; -Merlin- fills middle Eocene channels; onlap-and chaotic-fill; not sampled in upper rise DSDP sites, but possible updip equivalent (middle Miocene) sampled at COST B-3; ASP 14, 15. middle and early Miocene? Continuous from slope to rise; chiefly biogenous; broad seafloor exposure; channeled, very thick downdip; onlapped by several younger sequences; chiefly onlap-fill; subordinate slope-front and chaotic-fill; sampled at DSDP 605, 612, 613; COST B-3; ASP 15. late Oligocene ? Continuous from slope to rise; chiefly biogenous; porcellanite and very deep channels associated with upper surface; onlap-and chaotic-fill; slumps observed in cores; sampled at DSDP 605, 612, 613; COST B-3.