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Effects of ancient porosity and permeability on formation of sedimentary dolomites: Devonian Jefferson Formation (Frasnian), south-central Montana

Conference · · AAPG (Am. Assoc. Pet. Geol.) Bull.; (United States)
OSTI ID:5696426
Petrographic and geochemical evidence indicates that multiple dolomitization and dolomite stabilization events affected the Devonian Jefferson Formation (Frasnian) in south-central Montana. Several types of dolomite occur, defined by cathodoluminescence: nonzoned, dully luminescent subhedral-anhedral mosaics (most common), euhedral nonzoned and zoned dolomites, zoned dolomite cements, and irregularly luminescent dolomites (dully luminescent with irregularly luminescent regions). The irregularly luminescent fabrics probably represent partial replacement of early dolomite phases with later dolomite phases. Nonzoned, Ca-enriched, euhedral dolomites occur in calcite-cemented, coarse-grained limestone layers. These permeable layers probably were conduits for early meteoric waters, that occluded porosity in the limestones and prevented later dolomite stabilization. Irregularly luminescent dolomites are interpreted as intermediate fabrics in the dolomite stabilization process. Later calcite cements which occlude intercrystalline porosity prevented further dolomite replacement. Total recrystallization of remaining dolomites and formation of final dully luminescent mosaics occurred prior to brecciation and stylolitization.
Research Organization:
Washington State Univ., Pullman
OSTI ID:
5696426
Report Number(s):
CONF-870915-
Conference Information:
Journal Name: AAPG (Am. Assoc. Pet. Geol.) Bull.; (United States) Journal Volume: 71:8
Country of Publication:
United States
Language:
English