Time constraints on sulfate-related diagenesis, Capitan Reef Complex, west Texas and New Mexico

Conference · Tue May 01 04:00:00 EDT 1990 · AAPG Bulletin (American Association of Petroleum Geologists); (USA)

OSTI ID:6713562

Darke, G ^[1]; Harwood, G ^[2]

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1. Univ. of Newcastle upon Tyne (England)
2. Univ. of East Anglia, Norwich (England)

Petrographic, paleomagnetic, and outcrop studies of the middle Capitan Reef Complex in the Guadalupe Mountains have provided time constraints on diagenetic events and demonstrated the crucial role of calcium sulfate. Sulfate emplacement occurred at an early stage. The sulfate emplacement post-dated and replaced syndepositional marine margins and lath forms demonstrate replacement was by anhydrite rather then gypsum. Fabric-selective dolomitization and kaolinite precipitation derived from reworking shelf evaporite sequences moving downdip during early stages of drawdown within the Delaware basin. A second period of brine migration causing sulfate emplacement and dolomitization, occurred as the Delaware basin gradually filled with the Castile evaporites, when all remaining porosity within the Capitan shelf margin became indurated by calcium sulfate-laden fluids. This caused pervasive dolomitization, particularly in the lower foreslope, with formation of dolomite rhombs and overgrowths on earlier dolomitized marine cements, coeval with replacive clusters of anhydrite. Most porosity was plugged, some with syndepositional marine cements, but the greater proportion with evaporites until uplift in the Tertiary. Then a meteoric groundwater system became established with subsequent sulfate dissolution. Minor sulfate reduction formed iron sulfides. This oxidized to hematite, which was enclosed within a first generation of zoned calcite spar along some pore margins. Most hematite has a paleomagnetic age of 20 Ma, although minor hematite formation continues to the present. A second, also zoned, coarser calcite spar generation was followed by the latest nonluminescent calcite spar. These calcite spars form the vast bulk of that visible at outcrop.

• OSTI ID: 6713562
• Report Number(s): CONF-900605--
• Conference Information: Journal Name: AAPG Bulletin (American Association of Petroleum Geologists); (USA) Journal Volume: 74:5
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
ALKALINE EARTH METAL COMPOUNDS
ANHYDRITE
CALCITE
CALCIUM CARBONATES
CALCIUM COMPOUNDS
CALCIUM SULFATES
CARBON COMPOUNDS
CARBONATE MINERALS
CARBONATE ROCKS
CARBONATES
CENOZOIC ERA
DIAGENESIS
DISSOLUTION
DOLOMITE
EVAPORITES
FEDERAL REGION VI
GEOLOGIC AGES
GEOLOGIC STRUCTURES
GYPSUM
MAGNESIUM CARBONATES
MAGNESIUM COMPOUNDS
MINERALS
NEW MEXICO
NORTH AMERICA
OXYGEN COMPOUNDS
ROCKS
SEDIMENTARY BASINS
SEDIMENTARY ROCKS
SULFATE MINERALS
SULFATES
SULFUR COMPOUNDS
TERTIARY PERIOD
TEXAS
USA