CATHERINE L. SCHUUR¹, JOHN A. GOFF², and JAMES A. AUSTIN, JR.^2
1Department of Geological Sciences, The University of Texas at Austin, Austin, TX
²Institute for Geophysics, The University of Texas at Austin, Austin, TX

Abstract: Evidence for the most recent eustatic cycle on the New Jersey shelf: Quaternary analogs for ancient shelf surfaces and deposits

Shallow stratigraphic unit s and seafloor geomorphic elements record a series of depositional systems on the New Jersey continental shelf during the last advance and retreat of the Laurentide ice sheet. We use a 490 km2 middle shelf survey Of ultrahigh resolution (500-3500 Hz) 2D and embedded 3D seismic reflection profiles, acoustic swath maps and vibracores to develop a late Quaternary stratigraphy for this periglacial, clastic shelf.

Within our section we observe: 1) "R", a high-amplitude, inclined reflection separating sediment >45 ky old (by AMS C14) from overlying sediment wedges, 2) the outer shelf wedge, which onlaps "R", 3) "Channels", a discontinuous reflection subparallel to the seafloor that truncates "R", 4) "Channels" fill, 5) "13" a seismically discontinuous surface that truncates channels, 6) the mid-shelf wedge, a 10-15 m thick unit shoreward and stratigraphically above "13" and the outer shelf wedge, and 7) the modern seafloor, which includes both active and inactive bedforms.

A 2D/3D map of the "Channels" surface shows a dendritic network of channels buried <10 m below the seafloor; we identify "Channels" as the subaerial erosion surface formed at the late Wisconsin glacial maximum ~18 kya. We interpret horizon 13" as the diachronous transgressive ravinement surface created during Holocene sea level rise. There is no systematic relationship between seafloor bedforms and the very shallowly buried stratigraphy, implying that transgressive erosion and shelfal reworking created the seafloor geomorphology, a modern flooding surface.

AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas