Publication Date

2008-12-09

Availability

Open access

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PHD)

Department

Marine Geology and Geophysics (Marine)

Date of Defense

2005-12-06

First Committee Member

Gregor Eberli - Committee Chair

Second Committee Member

Harold Wanless - Committee Member

Third Committee Member

Christopher Harrison - Committee Member

Fourth Committee Member

Langhorne Smith - Outside Committee Member

Abstract

The aims of this study are to extend the established high-resolution sequence stratigraphic framework of the Madison Formation of Wyoming and southern central Montana to the correlative and genetically-related Mississippian carbonate ramp, ramp margin, and basin strata of the central Montana trough and Antler foreland basin in order to examine and discriminate the controls on depositional processes and the resulting stratigraphic architecture through space and time in tectonically-active settings. An outcrop-based, high-resolution sequence stratigraphic study of two ramp-to-basin transects, one in central Montana and the other in southwestern Montana and east-central Idaho, is conducted in order to examine these deposits across two coeval margins with differing subsidence, hydrodynamic, and physiographic configurations and histories. Independent measurements of system response to global and local forcings allows disentanglement of primary controls on deposition and allows us to gain understanding of the roles and interplay of these controls, in particular eustasy and tectonics, on the system's architectural development. Conversely, insight into the geodynamic evolution of western North America, glacioeustatic changes, and variations in global climate and oceanographic systems during the greenhouse-to-icehouse transition is gained. A series of high-resolution sequence stratigraphic cross-sections and time-slices are produced incorporating outcrop measured sections and measured sections previously collected by members of the Comparative Sedimentology Laboratory in a series of transects across the Madison ramp system. A new chronostratigraphic framework for Madison carbonates is developed by using Lower Carboniferous delta C-13 isotope excursions as isochronous tie points between ramp-top, margin, and basinal sections. These delta C-13 excursion events have been documented to be time-invariant globally due to global changes in ocean chemistry. The results of the study include resolution and discrimination of sequential foreland basin subsidence, carbonate sediment production and progradation, subsidence and uplift of foreland basin structures along a carbonate shelf edge, diachronous subsidence of discrete depocenters, and eustasy.

Keywords

Carbonate Sedimentary Response

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