Abstract

Variation in accumulation rate as a function of depositional latitude has been determined for North American limestone, dolostone, sand-stone, gray-black shale, red shale, and evaporite rocks from tabulations by Ronov and co-workers, from data in lexicons of United States and Canadian stratigraphy, and from isopach and lithofacies maps published in 1975 by Cook and Bally. Phanerozoic sediment is similar to that on other continents, consisting of 63% terrigenous elastic facies (23% sandstone; 40% shale), 36% carbonate, and 1% chert, evaporite, and other minor rock types.

Latitudinal variation in accumulation rate is influenced primarily by past positions of foreland and intracratonic basins. Additional variation related to paleoclimate is recorded as strong dependence of limestone, dolostone, red shale, and evaporite deposition on latitudes of accumulation, a relation reflecting the importance of ambient temperature and meteoric precipitation on the formation of various authigenic phases.

Poleward increase in dolostone/total carbonate ratio in both hemispheres implicates the importance of syndepositional diagenesis in the formation of most dolostone sequences. The ratio of sandstone/total terrigenous clastic sediment exhibits little variation with latitude, a constancy indicating that most sand and mud is derived from older sediment rather than from the weathering of crystalline rock. As a result, terrigenous lithofacies record little climatic influence in the proportional delivery of mechanically versus chemically derived weathering products to basins of accumulation.

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