15 Building Comprehensive Models of Epicratonic Paleoenvironments from Integrated, Basin-Scale, Lithostratigraphic and Chemostratigraphic Datasets

Thursday, 4 April 2013
1:30 PM - 5:30 PM
Classroom 102

DETRITAL ZIRCON GEOCHRONOLOGY OF PERMIAN STRATA FROM WESTERN KANSAS: IMPLICATIONS FOR PERMIAN PALEOGEOGRAPHY AND PALEOCLIMATE

Paper number: 15-8
Program: Theme Sessions
Time: 3:50 PM – 4:10 PM

Authors

Abstract

The Permian marks a time of substantial change in the Late Paleozoic climate. Aridification affected the equatorial region, and monsoonal conditions began and intensified. Although Permian redbeds, found throughout the mid-continent, have the potential to reveal this tectonic and climatic history, the exact ages, paleodispersal systems, depositional environments, and provenance of the sediment remain poorly constrained. Here, we report on detrital zircon geochronology from seven discrete samples spaced throughout a continuous whole core from Greeley County, KS which spans the late Pennsylvanian through likely lower Guadalupian, and is unconformably overlain by Jurassic strata. This geochronological data will be supplemented with geochemical and facies analysis. The goal is to begin to assess temporal changes in facies and provenance of sediments throughout this core in order to better interpret paleodispersal processes of these redbeds.

LA-ICPMS dating of U-Pb ages of zircons (n= 86-105) indicate changes in zircon populations, and therefore temporal changes in source areas. Dominant zircon age groupings that vary through the core include 1) Grenville basement ages; 2) early to mid Paleozoic grains; and 3) Neoproterozoic grains. The Grenville- and Paleozoic-aged grains increase in lower to upper samples from the Permian strata present in Kansas. In contrast, the Neoproterozoic grains decrease in abundance upward through the core. This provenance shift is likely coeval with the establishment of continental deposition across the mid-continent and provenance and transport of sediment that switched from north and eastern sources to southerly and southeasterly sources, although exact transport mechanisms and directions are uncertain. Further work on combining the provenance results with facies analysis will allow us to better constrain paleoclimatic- and paleotectonic-induced changes in paleodispersal systems for the Permian of the mid-continent.