Publication Date:
2019
Description:
〈span〉Despite extensive outcrop and previous sedimentologic study, the role of tidal processes
along sandy, wave- and river-dominated shorelines of the North American Cretaceous Western
Interior Seaway remains uncertain, particularly for the extensive mid-Campanian (ca.
75–77.5 Ma) tidal deposits of Utah and Colorado, USA. Herein, paleotidal modeling, paleogeographic reconstructions, and interpretations of depositional process regimes are combined
to evaluate the regional-scale (hundreds to thousands of kilometers) basin physiographic
controls on tidal range and currents along these regressive shorelines in the “Utah Bight”,
southwestern Western Interior Seaway. Paleotidal modeling using a global and astronomically
forced tidal model, combined with paleobathymetric sensitivity tests, indicates the
location of stratigraphic units preserving pronounced tidal influence only when the seaway
had a deep center (~400 m) and southern entrance (〉100 m). Maximum tidal velocity vectors
under these conditions suggest a dominant southeasterly ebb tide within the Utah Bight,
consistent with the location and orientation of paleocurrent measurements in regressive, tide-influenced deltaic units. The modeled deep paleobathymetry increased tidal inflow into the
basin and enhanced local-scale (tens to hundreds of kilometers) resonance effects in the Utah
Bight, where an amphidromic cell was located. However, the preservation of bidirectional,
mudstone-draped cross-stratification in fine- to medium-grained sandstones requires tides in
combination with fluvial currents and/or local tidal amplification below the maximum resolution
of model meshes (~10 km). These findings suggest that while regional-scale controls
govern tidal potential within basins, localized physiography exerts an important control on
the preservation of tidal signatures in the geologic record.〈/span〉
Print ISSN:
0091-7613
Electronic ISSN:
1943-2682
Topics:
Geosciences
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