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An upwelling model for the Phosphoria Sea; a Permian, ocean-margin sea in the Northwest United States

David Z. Piper and Paul Karl Link
An upwelling model for the Phosphoria Sea; a Permian, ocean-margin sea in the Northwest United States
AAPG Bulletin (July 2002) 86 (7): 1217-1235

Abstract

The Permian Phosphoria Formation, a petroleum source rock and world-class phosphate deposit, was deposited in an epicratonic successor basin on the western margin of North America. We calculate the seawater circulation in the basin during deposition of the lower ore zone in the Meade Peak Member from the accumulation rates of carbonate fluorapatite and trace elements. The model gives the exchange rate of water between the Phosphoria sea and the open ocean to the west in terms of an upwelling rate (84 m yr (super -1) ) and residence time (4.2 yr) of seawater in the basin. These hydrographic properties supported a mean rate of primary productivity of 0.87 g m (super -2) d (super -1) of carbon in the uppermost few tens of meters of the water column (the photic zone) and denitrifying redox conditions in the bottom water (below approximately 150 m depth). High rain rates, onto the sea floor, of the organic matter that hosted the phosphate and several trace elements contributed to the accumulation of phosphorite, chert, and black shales and mudstones. Evaporation in the Goose Egg basin to the east of the Phosphoria basin ensured the import of surface seawater from the Phosphoria sea. Budgets of water, salt, phosphate, and oxygen, plus the minor accumulation of the biomarker gammacerane, show that exchange of water between the two basins was limited, possibly by the shallow carbonate platform that separated the two basins.


ISSN: 0149-1423
EISSN: 1558-9153
Coden: AABUD2
Serial Title: AAPG Bulletin
Serial Volume: 86
Serial Issue: 7
Title: An upwelling model for the Phosphoria Sea; a Permian, ocean-margin sea in the Northwest United States
Affiliation: U. S. Geological Survey, Menlo Park, CA, United States
Pages: 1217-1235
Published: 200207
Text Language: English
Publisher: American Association of Petroleum Geologists, Tulsa, OK, United States
References: 99
Accession Number: 2002-062568
Categories: Economic geology, geology of energy sourcesStratigraphy
Document Type: Serial
Bibliographic Level: Analytic
Annotation: Includes appendix
Illustration Description: illus. incl. block diag., chart, strat. col., 2 tables, sketch map
N42°00'00" - N49°00'00", W117°15'00" - W111°04'60"
N41°00'00" - N45°00'00", W111°04'60" - W104°04'60"
Secondary Affiliation: Idaho State University, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data supplied by American Association of Petroleum Geologists, Tulsa, OK, United States
Update Code: 200220
Program Name: USGSOPNon-USGS publications with USGS authors
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