T120 Using Buried Soils to Reconstruct Past Climates: Opportunities and Considerations

Monday, 5 November 2012
1:30 PM - 5:30 PM
207BC

LATE QUATERNARY ALLUVIAL HISTORY OF THE OWL CREEK DRAINAGE BASIN: A GEOMORPHIC RESPONSE TO ENVIRONMENTAL CHANGE

Paper number: T120-3
Program: Technical Sessions
Time: 2:05 PM – 2:20 PM

Authors

Abstract

Fluvial systems have proven to be sensitive to climate change, documented by sediment erosion, deposition, and stability, followed by soil development. Owl Creek, a low-order stream, in central Texas provides an exceptional fluvial archive of alternating periods of late Quaternary environmental stability and flux. Eight allostratigraphic units were identified based on bounding erosional unconformities and associated buried soils that range in age from ~120 ka to present based on superposition, cross cutting relationships, and optically stimulated luminescence (OSL) dating. Environment of deposition of the Pleistocene units (Q1to Q6) includes coarse-grained alluvial fan and fluvial channel and bar deposits, with minor periods of pedogenesis. These deposits contrast markedly with finer-grained Holocene fluvial deposits (Q7 and Q8) containing buried soils, which are primarly Inceptisols and Entisols with some vertic properties and stage II pedogenic carbonates. The identified facies are dominantly massive fines with gravel and sand inputs. Pedogenesis has altered the fines with the identification of six buried soils and two active soils. The buried soils range in maturity based on degree of horizon development and pedogenic carbonate morphology, with stage IV laminar cap indicating the most mature soil.

Comparison of the Owl Creek fluvial and buried soil record with regional speleothem, pollen, magnetic susceptibility, and other late Quaternary sedimentary records suggest that climate was a driving factor at Owl Creek, with deposits dominated by coarse-grained deposits during the cooler/wetter Pleistocene and fine-grained warmer/drier Holocene. This study expands the central Texas fluvial chronology and evaluates the effects of landscape changes and associated climate and vegetation changes through the late Quaternary, with the preserved sequence of alluvial fan, fluvial and overbank deposits evidence of an evolving sedimentary record at Owl Creek.