Molecular and carbon isotopic analysis of specific biological markers: Evidence for distinguishing between marine and lacustrine depositional environments in sedimentary basins of Brazil

Conference · Mon Jan 01 04:00:00 EST 1996 · AAPG Bulletin

OSTI ID:6858289

Guthrie, J M; Trindade, L A.F.; Eckardt, C B; Takaki, T ^[1]

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1. Petrobras Research and Development Center, Rio de Janeiro (Brazil)

A suite of organic-rich, immature shales (TOC's ranging between 0.7 to 28.4 %) from various basins throughout Brazil were selected for carbon isotopic ([delta][sup 13]C) analysis of individual biological compounds in order to characterize marine and lacustrine depositional environments. Carbon isotopic compositions of pristane, phytane, n-heptadecane; 28, 30-bisnorhopane; 17[alpha](H), 21[beta](H)-hopane, and gammacerane, together with other commonly used biomarker parameters show variations that are related to sources of organic matter and to depositional processes in the paleoenvironment. Plots relating hopane/sterane ratios to the [delta][sup 13]C compositions pristane, phytane, n-heptadecane; 28, 30-bisnorhopane, and 17[alpha](H), 21[beta](H)-hopane show that these compounds in lacustrine shales are consistently more depleted in [sup 13]C than in marine shales. For example, the [delta][sup 13]C values of pristane and phytane in lacustrine shales vary from -28 to -32 %. and in marine shales from -22 to -24 [per thousand]. The correlation between high abundance of hopanes relative to steranes with depleted [sup 13]C compositions in these compounds is supporting evidence for a more abundant input of methanogenic bacteria in these lacustrine shales.

• OSTI ID: 6858289
• Report Number(s): CONF-960527--
• Conference Information: Journal Name: AAPG Bulletin Journal Volume: 5
• Country of Publication: United States
• Language: English

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02 PETROLEUM
020200* -- Petroleum-- Reserves
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58 GEOSCIENCES
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BACTERIA
BITUMINOUS MATERIALS
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CARBON ISOTOPES
CARBONACEOUS MATERIALS
CHEMISTRY
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