Ichnology of fine-grained mixed carbonate-siliciclastic turbidites, Wood River Formation, Pennsylvanian-Permian south-central Idaho
- Norcen Energy Resources Ltd., Calgary, Alberta (Canada)
- Idaho State Univ., Pocatello (United States)
In south-central Idaho, the Wood River Formation (Pennsylvanian-Permian) contains a stratigraphic megacycle over 2,000 m thick that is composed of fine-grained mixed carbonate-siliciclastic turbidites. Complete and partial (Bouma) turbidite structural sequences in these rocks are arranged in upward thinning cycles 15 to 30 m thick in which top-cut-out (Ta-c) turbidite facies in the lower part grade vertically into base-cut-out (Td-f) turbidites in the upper part. These cycles are interpreted to represent the autocyclic lateral migration of turbidite lobes. A mixed trace fossil assemblage of pascichnia and fordinichnia are present in these rocks and can be separated into pre-depositional and post-turbidite ichnocoenoses. Quiet-water, pre-turbidite deposits are dark-colored, laminated, and carbonaceous, and represent anoxic to dysoxic inter-turbidite basinal conditions; they contain only Chondrites traces. Turbidity currents introduced oxygenated bottom water which fostered the temporary development of a post-turbidite ichnocoenose of pascichnia which is best developed in the medial portion of turbidite beds and lobes. Trace fossil tiering shows that a post-turbidite ichnocoenose of fodinichnia also developed, and persisted after the disappearance of pascichnia. Animals that produced the fodinichnial traces probably were part of an autochthonous benthic fauna rather than a short-lived allochthonous fauna. They may have migrated with the slowly avulsing turbidite lobes and exploited allochthonous oxygen and the carbonaceous food supply.
- OSTI ID:
- 6140488
- Journal Information:
- Palaois; (United States), Vol. 6:3
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GEOLOGIC FORMATIONS
PALEONTOLOGY
IDAHO
CARBONATE ROCKS
CARBONIFEROUS PERIOD
FOSSILS
GEOLOGIC HISTORY
GEOLOGY
PERMIAN PERIOD
SEDIMENTARY BASINS
STRATIGRAPHY
THICKNESS
DEVELOPED COUNTRIES
DIMENSIONS
FEDERAL REGION X
GEOLOGIC AGES
GEOLOGIC STRUCTURES
NORTH AMERICA
PALEOZOIC ERA
ROCKS
SEDIMENTARY ROCKS
USA
580000* - Geosciences