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The Sedimentology, Sequence Stratigraphy, and Isotope Geochemistry of Lower Permian Carbonates, Orogrande Basin, South-Central New Mexico, USA

Jesse Koch
University of Nebraska-Lincoln, Department of Geosciences Lincoln, Nebraska; [email protected]

The late Paleozoic ice age (LPIA) was the longest global icehouse period during the Phanerozoic, and researchers working in Gondwana have made significant progress in characterizing the timing and extent of the LPIA. However, LPIA researchers face the difficult challenge of understanding how ice-proximal and ice-distal stratigraphic sections correspond to one another. This study is in the process of examining the Early Permian (Cisuralian) ice-distal carbonate record from the Orogrande Basin in New Mexico. The goal is to correlate this paleoequatorial record with the well-established eastern Australian ice-proximal record in order to gain a better understanding of global climate change during this icehouse world.

Currently, field studies and isotopic analyses are underway to help create a sequence stratigraphic framework for the Orogrande Basin, which can then be compared to other frameworks from around the globe, including eastern Australia. Preliminary field results from the Franklin and Sacramento Mountain ranges suggest cyclical deposition (3rd and 4th order cycles) of mixed carbonates and clastics during the Early Permian. At least 9 sequence boundaries and numerous flooding surfaces have been identified to this point. Since the LPIA acme was during the Early Permian, these cycles most likely represent changes in eustatic sea level due to glacioeustatic control.

Future work will focus on more field studies and a compilation of isotopic (carbon, oxygen, and strontium) analyses for the study area. The ultimate goal will be to tie cyclical depositional patterns in New Mexico to ice volume changes in Gondwana for the Permian.

AAPG Search and Discovery Article #90083 © 2008 AAPG Foundation Grants in Aid