Examining the Effect of Glacial-Interglacial Climate Change on Atmospheric Dust Loading and Source Rock Deposition in Equatorial Pangaea

Alice Stagner
University of Oklahoma, School of Geology and Geophysics Norman, Oklahoma
[email protected]

Silt-bearing carbonates of the late Paleozoic Bird Spring Formation are being investigated for links among atmospheric circulation and glacioeustatic-driven sedimentation that is characteristic of the Permo-Carboniferous. We hypothesize there should exist a systematic variation in abundance of eolian silt across glacial-interglacial boundaries, representative of shifts in aridity and temperature that likely accompanied glacial-interglacial cycling.

To test this hypothesis we are using a two-pronged, sedimentologic and stratigraphic approach to investigate the Bird Spring Formation (Arrow Canyon, Nevada) of western equatorial Pangaea. Paleogeographic data indicate the Bird Spring Formation formed in a distally-steepened ramp setting of the Cordilleran Miogeocline. Stratigraphy in the succession is characterized by shallowing-upward, meter-scale cycles likely of glacioeustatic origin. Though sedimentation of Bird Spring Formation was dominantly carbonate, preliminary observations confirm variation in the volume of silt throughout stratigraphic cycles. The silt is inferred to be of eolian origin, owing to lack of a proximal siliciclastic source to the Bird Spring-Ely trough as evidenced with paleogeographic data.

Fieldwork conducted for this study consisted of sampling at high-resolution (cm-scale) two sections of late Desmoinesian and Missourian- to lowermost Virgilian strata. Sequence stratigraphic and facies analyses are being used to assess paleoenvironments and shallowing and deepening trends which may be linked to glacial-interglacial cycles.
Detrital residue extraction and grain size analyses will be conducted to assess intracyclic variation in silt volume and as proxy for wind strength and provenance. Sedimentologic and stratigraphic data will be integrated to constrain atmospheric circulation and evaluate links among atmospheric dust flux and glacioeustatic-driven sedimentation.

 

AAPG Search and Discovery Article #90070 © 2007 AAPG Foundation Grants in Aid