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Petrography, geochemistry, and depositional setting of the San Pedro and Santo Tomas coal zones: anomalous algae-rich coals in the middle part of the Claiborne Group (Eocene) of Webb County, Texas

International Journal of Coal Geology

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Abstract

Two coal zones, the San Pedro and the overlying Santo Tomas, are presented for nearly 35 km in outcrop, surface and underground mines, and shallow drill holes along the strike of the middle part of the Claiborne Group (Eocene) in Webb County, Texas. A sandstone-dominated interval of 25 to 35 m separates the two coal zones, which range up to 3 m in thickness. The coal-bearing portion of the middle Claiborne Group in the Rio Grande area represents a fining-upward transition from sandstone-dominated, marine-influenced, lower delta plain depositional environments to more inland, mudstone-rich, predominantly freshwater deltaic settings. The less variable nature of the Santo Tomas coal zone reflects its origin in the upper part of an interlobe basin that received only minor clastic influx. Petrographic attributes of the nonbanded coals indicate that they formed subaqueously in fresh to possibly brackish waters. Petrographic study of polished blocks indicates that approximately 10% of the nonbanded coal from both coal zones is composed of green algae fructifications. -from Authors

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Petrography, geochemistry, and depositional setting of the San Pedro and Santo Tomas coal zones: anomalous algae-rich coals in the middle part of the Claiborne Group (Eocene) of Webb County, Texas
Series title:
International Journal of Coal Geology
Volume
28
Issue:
2-4
Year Published:
1995
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
International Journal of Coal Geology
First page:
303
Last page:
342
Number of Pages:
40