Record of Relative Sea-Level Changes, Cretaceous of Western Interior, USA
Published:January 01, 1988
Robert J. Weimer, 1988. "Record of Relative Sea-Level Changes, Cretaceous of Western Interior, USA", Sea-Level Changes: An Integrated Approach, Cheryl K. Wilgus, Bruce S. Hastings, Henry Posamentier, John Van Wagoner, Charles A. Ross, Christopher G. St. C. Kendall
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Two types of criteria are used to recognize relative changes in sea level in the Cretaceous of the Western Interior (Fig. 1). The first type is a highstand condition identified by: (1) highstand regression of the shoreline, depositing widespread shallow-marine sandstone and shale and shoreline sandstone, sometimese overlain by a widespread coal layer (Fig. 2); (2) deposits that fill incised drainage, reflecting rising sea level and landward movement of the shoreline (transgression) associated with coastal onlap; the incised valley fill may be zoned-more freshwater environments in the lower part and brackish to marine environments in the upper part (Figs. 3, 4); (3) recognition of one or more of the following in a marine condensed section: missing faunal zones; concentrations of phosphate nodules and/or glauconite; organic-rich shale with high total organic content; recrystallized shell debris forming thin lenticular limestone layers or shell hash in shale; residual concentrations of coarse-grained sand with chert pebbles and/or bone and teeth fragments on a transgressive surface of erosion. The second type is a lowstand condition recognized by: (1) lowstand surface of erosion with incised drainage; paleosols and root zones (causing zones of early cementation) may be preserved in marine shale or other deposits under an erosional surface (Fig. 3); this type of erosional surface is a major sequence boundary in analyses related to sequence stratigraphy; (2) more or less uniform depth of erosion by streams over large areas because of lowered base level; (3) missing shoreline and shallow marine sandstone facies; freshwater deposits rest on marine shales; (4) correlation with relative lowering of sea level and unconformities on other continents. Intrabasin fault block movement, creating topographic relief, may influence location of incised drainages (Figs. 3, 4).
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Sea-Level Changes: An Integrated Approach
Sea-Level Changes: An Integrated Approach - In October 1985, SEPM sponsored a four-day conference entitled ?Sea-Level Changes ? An Integrated Approach.? The purpose of the conference was to provide a forum for an interdisciplinary exchange of ideas on sea-level changes and to provide an opportunity for integrating various types of evidence in approaching unresolved issues. The conference was successful in bringing together scientists from industry, academia, and government, representing all of the major geosciences disciplines. Presentations of many new papers, plus significant releases of data that were previously held proprietary, provided fertile ground for discussion. This much-cited volume represents the best of the material presented at the conference. Includes the early ?Vail? chart.