AITKEN, JOHN F. and STEPHEN S. FLINT, University of Liverpool, U.K., L69 3BX

ABSTRACT: High Frequency Sequences within the Pennsylvanian, Breathitt Group, Appalachian Basin, Eastern Kentucky

The Pennsylvanian, Breathitt Group in eastern Kentucky is well exposed in large highway cuts which provide depositional dip and strike sections of up to 125 km and 100 km respectively. Parasequences and parasequence sets, with notable exceptions, are generally not identifiable. Nonetheless, it is possible to identify systems tracts on the basis of sequential position, facies associations and systematic changes in architectural style and sediment body geometries. The studied portion of the Breathitt Group represents three superimposed 3rd order composite sequences, each comprising stacked aggradational, progradational or retrogradational 4th order sequences. Stacking patterns indicate that the 4th order sequences occur in lowstand, transgressive and highstand sequence sets related to t e development of the 3rd order sequences.

In the lowstand sequence set, incision associated with successive 4th order sequence boundaries has commonly removed all the highstand and transgressive systems tracts of the underlying sequences, such that succeeding 4th order incised valleys are amalgamated. Within the transgressive sequence set, incision is at a minimum and incised valleys tend to stack discretely with the maximum amount of finegrained transgressive and highstand deposits between them. Highstand sequence sets are transitional in net: gross ratio between the lowstand and transgressive sequence sets.

Volumetrically, the majority of preserved sediment is represented by incised valley fills which offer the best potential reservoir rocks. The proliferation of individual sandstone beds within 4th order sequences offers multiple stacked reservoir targets. The lowstand sequence set is the most favourable, having the best reservoir potential owing to the greatest proportion of sandstone.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.