Abstract: Relative Marine Transgressive and Regressive Rates in Pennsylvanian of Appalachian Basin--Determination by Faunal Criteria
Jack Donahue, Harold B. Rollins, Marshall C. Carothers
Information on relative transgressive and regressive rates is generated mainly through faunal criteria with some independent input from lithic data. Quantitative data for both macrofaunas and microfaunas from marine sequences allowed discrimination of three distinct community structural types: the opportunistic phase with low diversity (and equitability) during transgression, the stable-mature phase with high diversity (and equitability) during stillstand, and the relict-mature phase with intermediate diversity (and equitability) during regression. Comparison of thickness of each phase in sections containing transgressive-regressive sequences gives a good picture of relative rates.
Size analysis of brachiopod and bivalve species within the same sequences is used to generate year-class data. Size-frequency plots show four to five peaks representing size classes generated by yearly spat falls. Sharply defined peaks imply yearly recruitment patterns and higher sedimentation rates.
AAPG Search and Discovery Article #90972©1976 AAPG-SEPM Annual Convention and Exhibition, New Orleans, LA