--> Carbonate Platform Emergence and Bauxite Formation, by A. Mindszenty and B. D'Argenio; #90986 (1994).

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Abstract: Carbonate Platform Emergence and Bauxite Formation

A. Mindszenty, B. D'Argenio

Bauxites are humid tropical weathering products, similar to "modern" oxisois, developing at times of long lasting subaerial exposure. When occurring in shallow water carbonate platform sequences, they record the coincidence of a rather particular set of climatic and geodynamic conditions.

As opposed to recurrent ephemeral exposure accompanied by calcretes and weakly developed clay paleosols, the presence of bauxites requires at least a million years of emergence, ample quantities of dust-size detrital clay spread over the exposed carbonate terrain, and not only hot but also humid climate to convert the dust blankets into bauxite. Correlation of platform-related bauxites in the Cretaceous of the Mediterranean convincingly shows that long exposure was brought about here by lithospheric bulge-related tectonic uplift; the source material was provided by episodically increased supply of (volcanogenic?) windborn dust and optimum climate conditions were the results of the general Greenhouse configurations amplified by the East-West orientation of the Tethyan seaway.

It is suggested that the exceptional abundance of bauxites in Cretaceous times (equivalent to the total of non-Cretaceous Phanerozoic bauxites) has to be considered not only as a passive product of the Greenhouse but also as a minor (?) but important feedback mechanism provided by the tropical terrestrial ecosystem to counteract the climate perturbation. This hypothesis is supported by apparent correlation of episodes of bauxite-type weathering on the exposed carbonate platforms with episodes of platform-drowning anoxia in the basins.

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