--> Abstract: Evolution of an Upper Carboniferous Non-Marine Succession in a High Accommodation Setting, Maritimes Basin, Canada, by S. J. Davies and M. Gibling; #90937 (1998)

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Abstract: Evolution of an Upper Carboniferous Non-Marine Succession in a High Accommodation Setting, Maritimes Basin, Canada.

DAVIES, SURAH J., Department of Geology and Geophysics, The University of Edinburgh, Grant Institute, West Mains Road, Edinburgh, UK, EH9 3JW; MARTIN GIBLING, Department of Earth Sciences, Dalhousie University, Halifax, Nova Scotia, Canada, B3H 3J5 (sarah.davies{@} glg.ed.ac.uk)

High magnitude, high frequency sea-level fluctuations have been demonstrated to be an important driving force in Carboniferous basins from North America and Europe when coeval falls produced fluvial incision in tectonically diverse basins. Evidence from the Cumberland Basin, the largest onshore coal depocentre within the Maritimes Basin, eastern Canada, differs significantly from this pattern since a hierarchy of numerous flooding events can be identified but there is no evidence for significant falls in base level.

The basin contains an 8 km Carboniferous succession of predominantly non-marine sediments. Detailed examination of a 700 in interval reveals three facies assemblages: poorly drained floodplain, well drained floodplain and open shelf settings. Predominantly green, rooted siltstones, coals, ostracod limestones and lagoonal sand rich intervals with standing vegetation distinguish the poorly drained floodplain setting. Fluvial channels, 4-5 in thick and less than 150 in wide, are an integral floodplain component with no change in architecture, grainsize or provenance across the basal surface. The open shelf facies assemblage comprises distinctive sharp-based, commonly hummocky cross stratified sandstone units above thick fauna-bearing limestones. These sandstones are commonly organised in flat-based domal forms deposited in an offshore setting. Trace fossils (Arenicolites, Kouphichnum, Cochlichnus and Treptichnus) associated exclusively with this facies assemblage imply at least brackish conditions existed during restricted periods.

The conclusion drawn from this basin is that accommodation space creation in a high subsidence regime outpaced base level falls despite a potential marine connection. The results have significance for sequence stratigraphic interpretations in other basins which have experienced high rates of subsidence.

AAPG Search and Discovery Article #90937©1998 AAPG Annual Convention and Exhibition, Salt Lake City, Utah