Evolution of the Lower Mississippian Mission Canyon Platform and Antler Foredeep, Montana and Idaho /
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| Other Authors: | , , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1991.
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| Subjects: | |
| Online Access: | ProQuest, Abstract Link to OAKTrust copy |
| Abstract: | The Mission Canyon Formation and stratigraphic equivalents were deposited on a ramp-like carbonate platform which developed on the foreland side of the Mississippian Antler foredeep in southwestern Montana and east-central Idaho. In individual outcrops, these strata can be subdivided into 20 to 60 m thick shallowing-upward units which are the local expressions of depositional sequences. Regional biostratigraphic and lithostratigraphic correlations of these units has allowed reconstruction of facies relationships within individual sequences. Twelve, and perhaps up to fourteen, third- to fourth-order depositional sequences have been recognized. Sequences in southwesternmost Montana can be correlated with subintervals of the Mission Canyon and Charles Formations in the central Williston Basin. Sequences in southwesternmost Montana and subintervals in the Williston Basin have very similar stacking patterns. Sets of stacked sequences and subintervals are bounded by correlative major marine flooding surfaces. These similarities suggest that the same mechanisms influenced evolution of the Mission Canyon Formation and stratigraphic equivalents in both areas. Correlation of sequences with subintervals in the Williston Basin, deposition of sequences during relative quiescence in the Antler thrust belt and the presence of an Early Carboniferous ice cap suggest that third- and fourth-order glacioeustatic sea level fluctuations probably controlled sequence development A lack of evidence for drowning of the Mission Canyon platform suggests that the rates and magnitudes of sea level oscillations were on the order of 10 to, at most, a few 10's of meters. Results of this study should be compared to other detailed studies of Lower Mississippian strata around the world in order to construct a more accurate sea level curve for the Early Mississippian. Third- to fourth-order eustatic sea level oscillations, combined with slow foredeep subsidence, allowed aggradation and progradation of the Mission Canyon platform... |
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| Item Description: | Typescript (photocopy). Vita. "Major subject: Geology." Contains 2 folded plates in back pocket. |
| Physical Description: | x, 105 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references. |