--> Abstract: Investigating Paleo-Tidality in Upper Carboniferous Epeiric Seas Using the Imperial College Ocean Model, by Martin R. Wells, Peter A. Allison, Gary J. Hampson, Matthew D. Piggott, and Christopher C. Pain; #90039 (2005)

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Investigating Paleo-Tidality in Upper Carboniferous Epeiric Seas Using the Imperial College Ocean Model

Martin R. Wells, Peter A. Allison, Gary J. Hampson, Matthew D. Piggott, and Christopher C. Pain
Imperial College London, London, United Kingdom

The lack of modern analogues to the vast epeiric seas of the past has led to much debate on the extent of tidal influence in these seas. Numerical modelling provides a quantitative means of investigating tidality in the geological record that does not require uniformitarian analogues.

The Imperial College Ocean Model (ICOM) is a new finite element model with a novel unstructured mesh. The ICOM has been tested on several present day basins to determine its accuracy and sensitivity to water depth and the presence of islands in known settings. Model tests on the present day Mediterranean Sea, North Sea and Baltic Sea accurately predict the tidal range given realistic bathymetry. Experiments using ‘simplified' bathymetries have geologically insignificant consequences to tidal range prediction. Islands exert an important control on tidal range in deep water (>1000 m), but are of negligible importance in shallow water (100 m) situations which typify ancient epeiric seas.

Case studies from Upper Carboniferous Eperic seas of Euramerica predict exceedingly low tidal ranges in Northwest Europe and low to moderate ranges in North America. Model outputs are supported by geological evidence in Northwest Europe. The North American basins have been argued as macro-tidal. We follow several lines of evidence to suggest this was not necessarily the case.

Low tidal ranges in ancient epeiric seas may be one mechanism to prevent water-body mixing, enhancing stratification and promoting anoxia. The Upper Carboniferous of Euramerica is punctuated by numerous black shale ‘marine bands' supporting this hypothesis.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005