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ABSTRACT: Balancing of Stratigraphic Cross Sections of the Delaware Basin and the New Jersey Continental Shelf to Determine Tectonic and Eustatic Controls

Scott A. Bowman, Karen S. Glaser, John E. Jordan, Thierry Jacquin, P. R. Vail

Balancing of stratigraphic cross sections from offshore New Jersey and the Delaware basin of New Mexico results in an improved understanding of the stratigraphic and structural elements that controlled their development. Cross section balancing is accomplished in three stages: interpretation of the sequence stratigraphy, backstripping, and simulation of the history of the section with a forward model. Interpretations of lithostratigraphic and biostratigraphic data from outcrops, seismic data, and well-log cross sections define the distribution in time and space of stratal surfaces, slope angles on depositional interfaces, and sediment flux. Backstripping coupled with biostratigraphic data defines the subsidence history in time and space. The simulation incorporates rules overning the behavior of sequences in response to the distribution of accommodation space. The simulation also incorporates rules such as deltaic sediments that prograde basinward filling the available space below a predefined depositional profile, and sediment bypassing that occurs when the coastline falls below the shelf slope break of the previous highstand and relative sea level is falling. The quantitative model constrains the interpretation by limiting process variables to values consistent with observed rates. The two-dimensional model assumes that progradation occurs in the plane of the cross section, and lithospheric flexure can be approximated by the convolution of point loads on an elastic plate.

The stratal patterns in the two stratigraphic cross sections can be reproduced by third-order (1.0-3.0 Ma) changes of eustasy. The Delaware basin is characterized by 5-10 Ma flexure loading cycles that are driven by tectonically induced variations in subsidence and clastic sediment delivered to the depocenter. Offshore New Jersey is characterized by exponentially declining thermal subsidence punctuated by a period of volcanism and uplift.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990