James M. Rine¹

(1) University of South Carolina, Columbia, SC

ABSTRACT: An Inclusive Approach To Modern Shelf Analogs

This approach for deciphering the rock record utilizes components from a variety of modern settings to construct composite analogs. The approach rationale is that even rigorous examinations of a single setting are insufficient to adequately understand the breath of processes impacting shelf sequences. Furthermore, one cannot be sure those processes documented during a study will be the significant few that are recorded in the rock record. Applying the composite approach to shelf sands of the Western Interior Seaway, three modern settings are utilized. To better understand shelf sandstone structures, internal characteristics of sands off the NE coast of USA are good analogs. For models of shelf sands reworked from deltaic and fluvial sediments the analog is the shelf off the US Gulf Coast. To understand sediment transport and deposition in a muddy, sediment-rich and energetic shelf setting (e.g., the Western Interior Seaway), the analog chosen is the Guiana Coast of NE South America. The Guiana setting is selected over the "popular" NE USA shelf model because the former is sediment-rich and is influenced by unidirectional currents. Part of the Guiana analog, and features common on NE USA shelf, are km-scale linear ridges or banks that are oriented oblique to the coastline. On the NE USA shelf these are sand ridges but on the Guiana shelf these features are made of mud and migrate approximately 1 km annually. Using an inclusive analog approach, components of these three settings are used to model the origin, transport and preservation of shelf sand bodies.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado