Origin of dolomites in a downslope biostrome, Jefferson Formation (Frasnian), central Idaho: evidence from REE patterns, stable isotopes, and petrography

Conference · Sat Aug 01 04:00:00 EDT 1987 · AAPG (Am. Assoc. Pet. Geol.) Bull.; (United States)

OSTI ID:5752645

Dorobek, S L

A completely dolomitized coral-stromatoporoid biostrome occurs at the top of the Dark Dolomite member of the Jefferson Formation (Frasnian) at Grandview Canyon, Lost River Range, central Idaho. The biostrome overlies a thick sequence of dolostones that were deposited in slope to deep ramp settings. The biostrome, therefore, formed in an open marine setting after shallowing of deep water environments. Zoned dolospar cement fills dissolution vugs and tectonic fractures. Stable isotopes for zoned dolospar are -13.1 to -6.5 per thousand delta/sup 18/O (average - 11.5) and -1.5 to -0.1 per thousand delta/sup 13/C (average -0.4). REE patterns for zoned dolospar have positive Ce anomalies, but total REE abundance is similar to REE abundance for replacive dolomites. Stratigraphic occurrence in an open marine setting, stable isotopes, and REE patterns suggest replacive dolomite phases formed during shallow burial diagenesis with significant involvement of nonevaporated sea water. More negative Ce anomalies near the top of the biostrome suggest a diagenetic overprint by oxidizing meteoric waters. Zoned dolospar probably formed from warmer, reducing burial fluids. Carbon for zoned dolospar probably was recycled from preexisting dolomite. These data may be useful for interpreting the origin of other anomalous platform dolostones.

• Research Organization: Washington State Univ., Pullman
• OSTI ID: 5752645
• 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

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