Abstract: Miocene Transgressions and Regressions of Delaware Coastal Plain

Hardarshan S. Valia, Barry Cameron

The undifferentiated Chesapeake Group (middle? Miocene) of the Delaware coastal plain shows a pattern of shifting loci of deposition indicating a lateral and vertical facies succession divisible into lower and upper transgressive-regressive units.

The lower transgressive-regressive unit is composed successively of (a) sedimentary rock-fragment-bearing, quartz-pebbly sand; (b) light-gray silt; (c) shell-fragment bearing, light-gray, fine-grained, quartz sand; and (d) light-gray, medium-grained, quartz sand. Sediments in the lower part of this unit were deposited in a shallow-marine environment during the transgressive phase. The uppermost sands were deposited in transitional-marine environments during regression.

The upper transgressive-regressive unit is composed of (a) light-gray, medium-grained, quartz sand; (b) gray silt; (c) rock-fragment and shell-fragment-bearing, medium-grained, quartz sand; and (d) two time-equivalent facies (light-gray, fine-grained, quartz sand and lignite-bearing, poorly sorted, dark-gray silt) which indicate the second regression accompanied by the development of contemporaneous lagoonal and barrier-island environments.

The model presented gives information on the environments of deposition, a framework for future stratigraphic subdivision and correlation, and the possibility of stratigraphic traps for oil and gas offshore.

AAPG Search and Discovery Article #90972©1976 AAPG-SEPM Annual Convention and Exhibition, New Orleans, LA