Summary

Thin sections of plastic impregnated cuttings, along with wireline logs, available shallow cores, and quarry exposures are being used to map the lithofacies distribution of the subsurface Paleogene deposits of the Noah Carolina coastal plain and to construct detailed lithologic-based cross sections. Data is being integrated with available biostratigraphic picks (based on forams and ostracods) within the wells, and combined with existing detailed biostratigraphy from thin exposed sections over structural highs (arches). Sedimentary facies are quartz sands, shelly sandstones and terrigenous mudstones (estuarine/lagoon facies); quartz sands and sandy mollusc-fragment grainstones (shoreface and lagoon); phosphatic hardgrounds (mid-shelf current and wave-swept non-depositional surface); bryozoan and echinoderm grainstones/packstones (outer shelf deposits); and fine skeletal wackestones and planktonic marls that are locally dolomitized (slope deposits). The sequence boundaries, defined by biostratigraphic gaps, are characterized by phosphatized hardgrounds, reworked phosphatic pebble conglomerates. The Paleocene to Oligocene supersequence consists of fine siliciclastic-dominated Paleocene sequences, overlain by several carbonate-dominated Eocene sequences with fine grained, pelagic carbonates in the lower part grading up into echinoderm-bryozoan-dominated sequences and then into late Eocene and Oligocene sequences of quartzose shelly grainstone/packstones with interlayered sands and more basinal echinoderm-bryozoan packstone. The facies resemble those formed on temperate water, mixed carbonate-siliciclastic continental shelves (distally steepened ramps). The succession may reflect a complex interplay of regional ocean currents, the swell-wave dominated shelf setting, basin tectonics, and long term climatic cooling coupled with increasing amplitude eustasy.

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