Date of Award

Spring 1995

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Ocean & Earth Sciences

Program/Concentration

Geology

Committee Director

Stephen J. Culver

Committee Member

Diane L. Kamola

Committee Member

Carl F. Koch

Call Number for Print

Special Collections LD4331.G4 S65

Abstract

Foraminiferal assemblages were described from three different depositional settings within the Upper Cretaceous (Campanian) Blackhawk Formation of Utah (known marginal marine environments, known marine environments, and along a suspected sequence boundary). Assemblages from the known marginal marine setting (as defined by sedimentologic-stratigraphic criteria) consisted of entirely agglutinated taxa dominated by Textularia sp. A. Assemblages from the known marine environment consisted of a mix of calcareous and agglutinated species, dominated by calcareous species (e.g., Gavelinella talaria). The foraminiferal assemblages from these known environments provide independent evidence that these sampled areas are characterized by marginal marine and fully marine deposits.

The foraminiferal data from the known environments were used to aid paleoenvironmental interpretation of the foraminiferal assemblages in samples associated with a suspected sequence boundary. Samples were taken from a 1 to 1.5 meter thick unit along 13km of continuous outcrop. This unit lies directly above delta front and lower shoreface deposits, and immediately above a surface suspected to be a sequence boundary. Foraminiferal assemblages from the unit above the suspected sequence boundary consist of entirely agglutinated assemblages in the landward direction to a mixed calcareous-agglutinated (agglutinated dominant) assemblage in the seaward direction. Based on data collected from the known environments, the entire 13km extent of this unit is interpreted as marginal marine, and provides unequivocal evidence that the suspected sequence boundary does, indeed, represent a surface of sea-level fall with a concomitant basinward shift of facies. Thus, the sampled unit immediately above the surface of sea-level fall is interpreted as a transgressive systems tract which formed during the subsequent sea-level rise.

Foraminiferal data can provide valuable information for the identification of a sequence boundary under similar conditions outlined in this study. This micropaleontologic approach may be most useful for high-frequency sequences where systems tracts are thin, and where sedimentologic-stratigraphic data prove to be equivocal.

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DOI

10.25777/eb9s-na97

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