--> ABSTRACT: Stratigraphic Architecture of Modern Shelf Sand Ridges, New Jersey Shelf, USA, by John W. Snedden, Ronald D. Kreisa, Roderick W. Tillman, Robert D. Winn Jr., William J. Schweller, S. J. Culver; #91020 (1995).

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Stratigraphic Architecture of Modern Shelf Sand Ridges, New Jersey Shelf, USA

John W. Snedden, Ronald D. Kreisa, Roderick W. Tillman, Robert D. Winn Jr., William J. Schweller, S. J. Culver

The ridge and swale topography of the modern Atlantic Shelf has long been recognized in bathymetric surveys, sidescan sonar, and surficial sediment studies. However, as the sub-bottom stratigraphy and architecture of these large (> 1 × 6 km) but enigmatic features is less well-understood, an integrated investigation of ridges in four separate areas of the New Jersey shelf was undertaken, with emphasis upon acquisition of relatively undeformed deep vibracore samples.

Vibracore cross-sections demonstrate that ridges found in present water depths ranging from 4 m (shoreface-attached ridge) to 45 m (detached ridge) share significant similarities in stratigraphic architecture. Units common to all four ridges include Holocene upper and lower ridge sand, swale/inlet-fill, back-barrier/lagoon, and Pleistocene gravels. Radiocarbon dating and stratigraphic interrelationships imply that these ridges originated initially from ebb-tidal delta precursors, developing then into shoreface-attached features, eventually detaching during continued relative sealevel rise and landward retreat of the shoreline. Contemporaneous barrier island/shoreface facies are apparently removed by ravinement processes.

Obvious differences between ridges, especially in bathymetric profile, microfaunal content, and absolute age, may be attributed to post-detachment evolution during the Holocene transgression (0 to 10 ka). These ridges are not moribund features but actively (and slowly) migrating large-scale bedforms under the influence of the present shelf hydrodynamic regime. Comparison of ridges in the four study areas illustrates processes occurring during transgressive periods on low subsidence, microtidal, storm-dominated settings and may be related to ancient marine sand bodies in transgressive systems tracts.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995