--> --> Abstract: Geochemical Characterization and Correlation of the Cathedral Bluffs Tongue, Southwestern Wyoming, by Luke P. McHugh, John-Paul Zonneveld, Gregg F. Gunnell, and William S. Bartels; #90124 (2011)

Datapages, Inc.Print this page

Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA

Geochemical Characterization and Correlation of the Cathedral Bluffs Tongue, Southwestern Wyoming

Luke P. McHugh1; John-Paul Zonneveld1; Gregg F. Gunnell2; William S. Bartels3

(1) Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, AB, Canada.

(2) Museum of Paleontology, University of Michigan, Ann Arbor, MI.

(3) Department of Geological Sciences, Albion College, Albion, MI.

The Green River Basin of southwestern Wyoming preserves a continental succession of fluvial and lacustrine deposits. Extensive outcrop exposures of the Early Eocene Cathedral Bluffs Tongue of the Wasatch Formation occur at the northern margin of the basin near South Pass, Wyoming. The succession is dominated by fluvial floodplain and channel deposits with subordinate lacustrine interbeds. Coarser fluvial sediments occur proximal to the Wind River mountain range, with the proportion of lacustrine interbeds increasing to the south. Climatic and tectonic influences resulted in a regression of Paleolake Gosuite and consequently fluvial deposition dominated during the study interval. Episodic movement along the thrust fault resulted in fluctuations in lake-level resulting in several lacustrine interbeds.

Utilization of traditional methodologies such as detailed facies analysis and spectral gamma are insufficient for lateral correlation within this succession. This is due, in part, to the lithological complexity of the succession, wherein abrupt lateral facies changes and unconformities on several scales render regional correlations difficult. As a result, alternative methods have been utilized to correlate the units. Detailed whole-rock geochemistry has been used to identify elemental changes and trends throughout the Cathedral Bluffs Tongue. Samples were taken at one-meter intervals and analyzed for 61 elements using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Chemostratigraphy has proven to be remarkably effective for characterizing and correlating units within the study interval.

Specific horizons exhibit distinct chemical characteristics, which have assisted in subdividing the study interval into chemostratigraphic zones. Each zone has a distinct geochemical signature that has been identified and correlated throughout the study area. The chemical characteristics for each facies change vertically through the section and demarcate important stratigraphic intervals. Changes in elemental concentrations are linked to subtle changes in sediment provenance, caused primarily by syndepositional tectonic activity. Post-depositional factors such as weathering and diagenesis may have affected the primary geochemical signature of the succession. Thus, the use of immobile elements (such as Zr, Cr, Nb) for determining sediment provenance has proven to be most successful, as geologic processes do not affect these elements after deposition.