[First Hit]

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ELLIOTT, TREVOR, Department of Earth Sciences, Univ. of Liverpool, Liverpool, England; and ANDREW J. PULHAM, British Petroleum, Colombia

ABSTRACT: High Resolution Sequence Stratigraphy of Upper Carboniferous Shelf-Margin Delta Previous HitSystemsNext Hit: Analogues for Gulf Coast Delta Previous HitSystemsNext Hit

Upper Carboniferous strata exposed in western Ireland include fine-grained, fluvial-dominated, unstable delta Previous HitsystemsNext Hit which exhibit slumps, growth faults and mud diapirs. Shelf- and shelf-edge deltas can be distinguished, both closely resembling Tertiary deltas in the sub-surface Gulf of Mexico. High resolution sequence stratigraphic analysis of a regional scale depositional strike section (400 m thick, 40 km wide) through the delta Previous HitsystemsNext Hit reveals a complex range and hierarchy of key stratigraphic surfaces. Surfaces formed during periods of falling Previous HitseaNext Hit Previous HitlevelNext Hit include down-dip sequence boundaries represented by widespread syn-sedimentary deformation horizons in the prodelta region, up-dip sequence boundaries represented by erosional unconformities at the base of incised valley Previous HitsystemsNext Hit nd forced regression surfaces. Transgressive surfaces include thin, faunal concentrate horizons interpreted as initial and maximum flooding surfaces and intensely bioturbated surfaces which bound parasequences and parasequence sets. Recognition of this hierarchy of surfaces permits the effects of two superimposed orders of fluctuation in relative Previous HitseaNext Hit Previous HitlevelNext Hit to be discriminated within the delta Previous HitsystemsNext Hit. Assessment of the relative importance of Previous HitsystemsNext Hit Previous HittractsNext Hit preserved in the strike section reveals that lowstand Previous HittractsNext Hit (prograding lowstand wedge and incised valley fills) and, to a lesser extent, transgressive Previous HitsystemsNext Hit Previous HittractsNext Hit predominate. In contrast, highstand Previous HitsystemsNext Hit Previous HittractsNext Hit are poorly represented. The down-dip, shelf-margin location of the strike section and the high frequency/high magnitud , glacially forced character of the Previous HitseaNext Hit Previous HitlevelTop curve are felt to be the dominant factors in explaining this bias.

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