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Abstracts: High Resolution Sequence Stratigraphy of Deltaic, Slope, and Turbidite Depositional Previous HitSystemsNext Hit in the Upper Carboniferous of Northern Europe

ELLIOTT, TREVOR

The Upper Carboniferous in northern Europe was characterized by a humid--tropical climate, high magnitude--high frequency fluctuations in Previous HitseaNext Hit Previous HitlevelNext Hit forced by the Gondwanan glaciation, and a copious sediment supply. Faunal concentrate condensed horizons (marine bands) produced during periods of rising Previous HitseaNext Hit Previous HitlevelNext Hit provide a high-resolution chronostratigraphic framework in which intervals of approximately 60,000 yr can be analyzed at a regional scale. These conditions render Upper Carboniferous successions an ideal testing ground for the methods and concepts of high-resolution sequence stratigraphy. Extension in the Lower Carboniferous was followed by thermally-driven subsidence in the Upper Carboniferous, and in the early part of the Upper Carboniferous the basins were characterized by a stepped bathymetry that was inherited from the extensional Previous HitphaseNext Hit. The basins comprised river-fed deltas, a basin slope, and deeper basin turbidite Previous HitsystemsNext Hit. Re-examination of classic sections in these basins using an integrated sedimentological and sequence stratigraphic approach has challenged many long-held views of Upper Carboniferous sedimentation.

These points can be illustrated by reference to a well exposed remnant of an Upper Carboniferous basin in western Ireland, the Clare Basin. The basin comprises a 1.6-km succession that commenced with a deepening, sediment-starved Previous HitphaseNext Hit and was followed by a basin-fill succession of turbidites, slope, and deltaic deposits. Examination of the deltaic deposits has led to the recognition of regional-scale incised valleys dominated by sand-rich fluvial deposits, lowstand shelf-edge deltas that differ sedimentologically from highstand and transgressive Previous HitsystemsNext Hit tract deltas, and a pronounced bias in preserved Previous HitsystemsNext Hit Previous HittractsNext Hit to those associated with lowstand conditions. In the slope an ordered, Previous HitseaNext Hit Previous HitlevelNext Hit--driven stratigraphy that includes the creation and filling of slope channels in a single Previous HitseaNext Hit Previous HitlevelNext Hit Previous HitcycleTop has been recognized. In the deeper basin, discrete sand-rich lowstand turbidite units can be identified between regionally extensive condensed horizons. Although this succession accumulated in an intracratonic basin, it shares many similarities with the stratigraphy and sedimentation of clastic-rich, delta-driven passive margins such as the Gulf of Mexico, Nigeria, and Angola.

AAPG Search and Discovery Article #90938©1997-1998 AAPG Distinguished Lecturers