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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 65 (1981)

Issue: 5. (May)

First Page: 969

Last Page: 969

Title: Upwelling and Phosphorites in Paleozoic: ABSTRACT

Author(s): Judith Totman Parrish, Roger G. Humphreville

Article Type: Meeting abstract


The prevailing hypothesis concerning the origin of some major phosphorite deposits is that they were deposited in upwelling zones. To date, tests of this hypothesis have used criteria effective on a local scale rather than a global one, partly because reliable paleogeographic maps have not been available until recently. Good paleogeographic maps are essential because one must be able to model global atmospheric circulation patterns to predict the locations of upwelling currents, which are wind-driven. We know that today upwelling occurs primarily on west-facing coasts at about 30° latitude. Insofar as we have been able to identify such coasts in the past, attempts at predicting phosphorite localities have been successful. However, several other types of upwelling zon s, unimportant to phosphorite deposition in the present world, were more important in the past when the continents were distributed differently. These other upwelling zones include zonal coastal upwelling, equatorial and high-latitude symmetrical divergence, and radial divergence. We will present atmospheric circulation and upwelling models for the Paleozoic constructed on global paleogeographic maps. The correspondence between the predicted upwelling zones and the locations of the major Paleozoic phosphorite deposits is highly significant (p ^Lt .005) for the Paleozoic as a whole, as well as for individual Paleozoic time periods, particularly the Cambrian and Lower Carboniferous.

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Copyright 1997 American Association of Petroleum Geologists