Diagenesis of deeply buried Eagle Mills sandstones. Implications for paleo-fluid migration and porosity development
- Texaco EPTD, Houston, TX (United States)
Eagle Mills strata (Triassic-Jurassic) unconformably overlie the Paleozoic basement complex and thus, form the basal sedimentary unit within the Gulf Coast basin. Jurassic-aged basaltic dikes and sills have intruded Eagle Mills strata. These sedimentary and igneous rocks are the earliest record of Gulf of Mexico rifting. Deeply buried (15,000 to 18,000 ft.) Eagle Mills sandstone have subarkosic and sublithic modal compositions. These sandstones exhibit evidence of a complex and prolonged diagnetic history, including: early chlorite cementation; early quartz and feldspar overgrowths; early calcite and dolomite cementation; dissolution of framework grains and early carbonate cements; kaolinite precipitation; late ferroan carbonate cementation; albitization; late chlorite and anhydrite replacement; saddle dolomite cementation; and pyritization. Pyrobitumens coat early chlorite rim cements indicating that most diagenesis post-dated hydrocarbon migration. Secondary porosity development coincided with a later burial dissolution event. The Eagle Mills paragenetic sequence records progressive burial into a high-temperature diagenetic regime where thermochemical sulfate reduction was the dominant process. Marked shifts in paleo-water chemistry are recorded by the Eagle Mills diagenetic sequence. Pervasive dissolution of detrital feldspars in some Eagle Mills sandstones provides unequivocal petrographic evidence for deep-seated sourcing of diagenetic fluids, which migrated along faults, and contributed to the diagenesis of overlying Mesozoic strata. These petrographic analyses support interpretations of geochemical/fluid-flux data for the Mesozoic Gulf Coast basin.
- OSTI ID:
- 150545
- Report Number(s):
- CONF-9510222--
- Journal Information:
- AAPG Bulletin, Journal Name: AAPG Bulletin Journal Issue: 10 Vol. 79; ISSN 0149-1423; ISSN AABUD2
- Country of Publication:
- United States
- Language:
- English
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