--> The Role of Tectonism, Eustasy, and Climate in determining the Location and Geometry of Coal Deposits, by P. J. McCabe and K. W. Shanley; #90986 (1994).

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Abstract: The Role of Tectonism, Eustasy, and Climate in determining the Location and Geometry of Coal Deposits

Peter J. McCabe, Keith W. Shanley

Climatic conditions suitable for peat accumulation are common--about 10% of the Earth's land surface is covered by nonsaline wetlands. However, thick peats that could be precursors of coal have accumulated in only a small fraction of this area. Previous studies have emphasized the role of climate in determining the development of peat-forming environments--particularly in the formation of raised mires, which may be the precursors of thick, low ash coals. However, examination of Holocene environments suggests that the type of mire is determined by the rates of peat accumulation relative to the rates of base level rise resulting from the interaction of eustasy and basin subsidence.

During the rapid rise in relative sea level from 14,000 to 8,000 years BP the coastal plain of the Netherlands underwent rapid transgression with only thin peat accumulation. Prom 8000 to 5000 years BP the coastal plain vertically aggraded, as sediment supply kept pace with the creation of accommodation space, but only low-lying mires could develop because sea level rise still outstripped peat accumulation rates. About 5,000 years ago, as the rate of sea level rise decreased, the coastline became regressive and raised mires rapidly developed on the coastal plain. Although the climate was continually favorable, raised mires could only form when the rate of peat accumulation exceeded the rate of base level rise.

The accumulation of coals in coastal plain settings must be viewed, therefore, as part of the sediment budget which, interacting with changes in accommodation space, determines the sedimentary architecture and type of facies development The presence, thickness and geometry of coals allows some quantification of rates of base level rise.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994