Late Jurassic paleoceanography, salinity crises, and anoxia as determined from sedimentology and geochemistry of Lower Smackover mudstones, Mississippi Salt Basin

Conference · Wed Jan 01 04:00:00 EST 1992 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5770260

Heydari, E; Wade, W J ^[1]

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1. Louisiana State Univ., Baton Rouge, LA (United States). Dept. of Geology

Three lithofacies of the lower Smackover Formation--laminated mudstone, thin-bedded mudstone, and burrowed mudstone--exhibit distinct vertical [partial derivative]O-18 and [partial derivative]C-13 trends. For example, within the laminated mudstone lithofacies, [partial derivative] O-18 compositions increase from [minus]4 per mil (PDB) at the base to +1 per mil at the top; [partial derivative] C-13 compositions increase by 2 per mil from the base to the middle, and then decrease by 2 per mil from the middle to the top. Based on lithology, sedimentary structures, and isotopic trends, three stages of paleoceanographic circulations corresponding to climate/sea-level fluctuations are inferred. During a steady rise in relative sea-level, the laminated mudstone lithofacies was deposited from a stable, stratified water column consisting of a warm, hypersaline, and anoxic bottom water separated by pycnocline and halocline from a less saline and oxygenated surface water. The thin-bedded mudstone lithofacies was deposited during subsequent sea-level highstand with higher order fluctuations. Laminated beds were deposited during warmer climate and pulses of sea-level rise from a stratified water column with a surface water of low salinity and high productivity; bioturbated beds formed during cooler climate and sea-level standstill when the basin became uniformly hypersaline with low productivity. The burrowed mudstone lithofacies was deposited during continued sea-level highstand when basin oxygenation allowed through mixing of sediments by organisms.

• OSTI ID: 5770260
• Report Number(s): CONF-921058--
• Conference Information: Journal Name: Geological Society of America, Abstracts with Programs; (United States) Journal Volume: 24:7
• Country of Publication: United States
• Language: English

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