Paleoceanographic and paleoclimatic controls on ooid mineralogy of the Smackover Formation, Mississippi salt basin: Implications for Late Jurassic seawater composition
- Louisiana State Univ., Baton Rouge, LA (United States)
The Late Jurassic Smackover Formation in the Mississippi salt basin consists of two 150 m thick shoaling-upward cycles, each capped by ooid grainstones. During deposition of the lower cycle, originally calcite ooids formed on the seaward side of the basin and former aragonite ooids were precipitated on the landward side. In the upper cycle, originally calcite ooids were precipitated on both the seaward and the landward sides of the basin. Because kinetic variables are incapable of totally preventing aragonite formation the authors suggest that Smackover calcite ooids were precipitated from seawater with low carbonate saturation state (possibly undersaturated relative to aragonite). The shift from seaward calcite to landward aragonite ooids in the lower cycle was controlled by a shoreward increase in seawater salinity. The net effect of the salinity gradient was a landward increase in seawater salinity. The net effect of the salinity gradient was a landward increase in the carbonate saturation state in response to decreasing dissolved CO[sub 2] and increasing CO[sub 3][sup 2[minus]], Ca[sup 2+], and temperature. In seawater supersaturated with respect to both aragonite and calcite, kinetic variables favored dominance of aragonite over calcite. The landward increase in seawater salinity reflects extensive evaporation in an arid climate, resulting in antiestuarine circulation. The monomineralogic (calcite) nature of ooids of the upper cycle suggests that the salinity gradient across the basin was not sufficient to alter the seawater saturation state. This is attributed to a less arid climate and/or a less restricted circulation.
- OSTI ID:
- 7296444
- Journal Information:
- Journal of Sedimentary Research - Section A; (United States), Vol. A64:1
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CARBONATE ROCKS
GEOCHEMISTRY
MINERALOGY
PETROLOGY
GEOLOGIC FORMATIONS
PALEOCLIMATOLOGY
MISSISSIPPI
SEAWATER
CHEMICAL COMPOSITION
DEPOSITION
LITHOLOGY
CHEMISTRY
DEVELOPED COUNTRIES
GEOLOGY
HYDROGEN COMPOUNDS
NORTH AMERICA
OXYGEN COMPOUNDS
PALEONTOLOGY
ROCKS
SEDIMENTARY ROCKS
USA
WATER
580000* - Geosciences