At House Creek, cores of the producing Sussex zone reveal a coarsening-upward marine sequence beginning with silty shale and ending with a conglomeratic sandstone. Producing sandstone, 36 mi (58 km) in length, rarely exceeds 1 mi (1.6 km) in width and has an outward "shoestring" appearance. However, distribution of producing and nonproducing sand shows that the thickest part of the complex is immediately southwest of the producing trend and that the sand complex is geometrically asymmetrical--about 17 mi (27 km) across.

The sand zone appears asymmetrical also with respect to sand facies. On the steeper northeast side, the sand complex maintains a sanding-upward profile. In contrast, on the gentler sloping side the facies sequence merges into a single widespread facies. This asymmetry has made possible development of an E-log model for the sand zone.

Deposition of Sussex sand in the House Creek area may have been 50 to 100 mi (80 to 161 km) from the general shoreline in water depths of 50 ft (15 m) or greater. The Sussex zone forms the marine "topsets" of a major basin-filling wedge of fine clastic sediments which prograded from the northwest.

We have difficulty in explaining how sands and gravels in this depositional setting were transported great distances offshore by shelf processes alone. A suggested analog, the Atlantic shelf ridges formed during post-Pleistocene transgression by shoreface erosion and being restructured by the shelf hydrologic regime, is unacceptable because regression and shoreface retreat cannot be documented for the Sussex at House Creek. A model proposed here combines up-coast regression, shoreline retreat, and along-shelf transport. The model emphasizes wave-generated unidirectional currents transporting sediment southerly along or oblique to shelf isobaths.

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