Diagenetic history of Missourian (Upper Pennsylvanian) Chanute Shale, Cherokee Shelf, midcontinent U. S. A

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

OSTI ID:6106281

Fernandez, S; Brenner, R L ^[1]

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1. Univ. of Iowa, Iowa City, IA (United States). Dept. of Geology

The Chanute (Ch) Shale consists of two sandstone bodies deposited in fluvial deltaic complexes separated by a shale unit and a coal. The lower Ch is characterized by very fine-to-medium-grained sandstone that fill channels at its base, while the upper Ch includes silt-to-fine-grained sandstone bodies. Petrographic analyses of both units show that they consist of quartz arenites, subarkose, sublitharenite, feldspathic litharenites, litharenites and wackes of the same compositions. Silica-supersaturated waters in the meteoric regime cemented the Ch sands creating thin and discontinuous overgrowths on detrital quartz grains. Early calcite cement precipitated afterwards, inhibiting further silica cementation and shielding feldspars and other liable grains from extensive dissolution. A change in the composition of the meteoric waters caused calcite dissolution leaving patches of cement. As Ch sands entered the compactional regime, saline and alkaline waters dissolved quartz grains and overgrowths as well as other liable grains no longer shielded by the early carbonate cement. The absence of cements and continued compaction resulted in concave-convex and sutured contacts. Dissolution and alteration of feldspars, alteration of micas to clays, and chloritization of biotite and clays continued in the compactional regime. Acidified waters released from organic matter and coal altered micas and feldspars to kaolinite and other clays, releasing Fe, Mg, and Ca necessary for late precipitation of ankerite, dolomite, and calcite cements. Extensive clay and Fe oxide coatings formed, filling embayments on the etched grains. During subsequent Pennsylvanian low sea level stands, ground water dissolved most carbonate cements, creating secondary porosity. Porosity was further enhanced on the outcrop belt during weathering, leaving higher total Fe oxide content on surface samples compared to core samples.

• OSTI ID: 6106281
• Report Number(s): CONF-921058-; CODEN: GAAPBC
• Journal Information: Geological Society of America, Abstracts with Programs; (United States), Vol. 24:7; Conference: 1992 annual meeting of the Geological Society of America (GSA), Cincinnati, OH (United States), 26-29 Oct 1992; ISSN 0016-7592
• Country of Publication: United States
• Language: English

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PETROGRAPHY
POROSITY
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