Geochemical indicators of depositional environment and soruce-rock potential for the Upper Ordovician Maquoketa Group, Illinois basin

Journal Article · Sun May 01 00:00:00 EDT 1994 · AAPG Bulletin (American Association of Petroleum Geologists); (United States)

OSTI ID:6997788

Guthrie, J M; Pratt, L M ^[1]

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1. Indiana Univ., Bloomington, IN (United States)

Two depositional cycles are recognized within the Upper Ordovician Maquoketa Group of the Illinois basin in a core from the New Jersey Zinc 1 Parrish well of Fulton County, Illinois. Organic carbon (C[sub org]), total sulfur, [sup 13]C content of the organic carbon ([delta][sup 13]C[sub org]), hydrogen and oxygen indices (HI and OI) from Rock-Eval pyrolysis and yields of extractable organic matter (EOM) vary through the cycles. Dark-brown to black, laminated shales are present in the lower portion of each cycle and have high values of C[sub org] (1.0-3.0%), HI (500-1000 mg hydrocarbon [HC]/g total organic carbon[TOC]), and EOM (500-2500 ppm), and more negative [delta][sup 13]C[sub org] values ([delta][sup 13]C[sub org] = -30 to -30.5%). Gray to greenish-gray, bioturbated shales are present in the upper portion of each cycle and have low values of C[sub org] (<1.0%), HI (<500 mg HC/g TOC), and EOM (<500 ppm), and more positive [delta][sup 13]C[sub org] values (-28.5 to 29.5%) compared to the laminated shales. Although thermally immature or marginally mature in this core, the laminated shales represent potential source rock s for petroleum because they contain good to excellent quantities of oil-prone organic matter and are more deeply buried in other areas of the basin. Kerogen elemental data and Rock-Eval data suggest that the source of organic matter in the Maquoketa was uniform, with the notable exception of graptolite-rich layers. Distributions of saturated hydrocarbons for Maquoketa samples resemble those derived from amorphous organic matter. Variations in bulk geochemical data and carbon isotopic compositions within the Maquoketa Group indicate substantial reworking and degradation of organic matter associated with bioturbation and oxygenated depositional conditions. 64 refs., 10 figs., 1 tab.

• OSTI ID: 6997788
• Journal Information: AAPG Bulletin (American Association of Petroleum Geologists); (United States), Vol. 78:5; ISSN 0149-1423
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
HYDROCARBONS
DISTRIBUTION
ORGANIC MATTER
DEPOSITION
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GEOCHEMISTRY
GEOLOGIC STRATA
ILLINOIS
ILLINOIS BASIN
KEROGEN
PRODUCTIVITY
RESERVOIR ROCK
SEDIMENTARY BASINS
SHALES
SOURCE ROCKS
BITUMINOUS MATERIALS
CARBONACEOUS MATERIALS
CHEMISTRY
DEVELOPED COUNTRIES
GEOLOGIC DEPOSITS
GEOLOGIC STRUCTURES
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MATTER
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NORTH AMERICA
ORGANIC COMPOUNDS
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SEDIMENTARY ROCKS
USA
020200* - Petroleum- Reserves
Geology
&amp; Exploration