Sedimentology of the Sundance Formation, northern Wyoming Uhlir, David
dc.contributor.department Geological and Atmospheric Sciences 2018-08-22T21:58:32.000 2020-06-30T07:14:39Z 2020-06-30T07:14:39Z Thu Jan 01 00:00:00 UTC 1987 1987
dc.description.abstract <p>The glauconitic sublitharenites and arenaceous biosparites of the upper 20 meters of the Sundance Formation are the deposits of a regressive shoreline that existed in northern Wyoming during the Late Jurassic. This regressive shoreline was characterized by discontinous barrier islands, with associated inter-barrier tidal inlets, back-barrier shoals and sandy tidal flats. In north-central Wyoming, this shoreline trended generally east-west, with the regression progressing from south to north. Within the sublitharenites of the uppermost Sundance Formation, tidal bundles, sigmoidal reactivation surfaces, herringbone cross-lamination and abundant mud drapes are a record of the influence of tidal currents during the deposition of the unit. The neap-spring cyclicity of the tidal bundles implies that they were developed in a diurnal tidal setting. The tidal range along the Late Jurassic shoreline is estimated to have been at least mesotidal (2-4 m) in north-central Wyoming. The lateral migration of inter-barrier tidal inlets along the regressive shoreline caused the sublitharenites and biosparites of the uppermost Sundance Formation to be deposited as tabular, laterally-extensive units. Earlier models, which attach an offshore environment of deposition to these units, do not explain their tabular geometries and conformable stratigraphic relationship with the overlying non-marine sediments of the Morrison Formation;The Late Jurassic seaway was a foreland basin, formed by downbowing of the North American craton in response to the load of the Cordilleran thrust belt. The areal distribution of dark chert clasts (of probably upper Paleozoic derivation) in the fragmental biosparites of the uppermost Sundance Formation suggests that areas of positive relief existed within the Late Jurassic seaway. The proximal, most obvious evidence (e.g., conglomerates overlying an unconformity) of these Late Jurassic structures is only rarely preserved. This proximal evidence exists only where the Jurassic highs have not been overwhelmed by the later development of Laramide structures.</p>
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dc.identifier.articleid 12653
dc.identifier.contextkey 6458350
dc.identifier.s3bucket isulib-bepress-aws-west
dc.identifier.submissionpath rtd/11654
dc.language.iso en
dc.source.bitstream archive/|||Fri Jan 14 18:55:08 UTC 2022
dc.subject.disciplines Geology
dc.subject.keywords Earth sciences
dc.subject.keywords Geology
dc.title Sedimentology of the Sundance Formation, northern Wyoming
dc.type article
dc.type.genre dissertation
dspace.entity.type Publication
relation.isOrgUnitOfPublication 29272786-4c4a-4d63-98d6-e7b6d6730c45 dissertation Doctor of Philosophy
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