HR: 1340h
AN: PP43C-1533    [Abstracts]
TI: A Rare Early Pliocene Record of Paleoclimate from North-central Indiana, USA
AU: * Shunk, A J
EM: aaron_shunk@baylor.edu
AF: Baylor University, Department of Geology One Bear Place #97354 Waco, TX -7354, Waco, TX 76798, United States
AU: Driese, S G
EM: steven_driese@baylor.edu
AF: Baylor University, Department of Geology One Bear Place #97354 Waco, TX -7354, Waco, TX 76798, United States
AU: Farlow, J O
EM: farlow@ipfw.edu
AF: IUPU Fort Wayne, Dep. of Geosciences 2101 E. Coliseum Blvd., Fort Wayne, IN 46805, United States
AU: Fluegeman, R
EM: rfluegem@bsu.edu
AF: Ball State University, Geology Department Ball State University AR 117, Muncie, IN 47306, United States
AB: The Early Pliocene is a critical period in Earth history, representing warm Earth conditions immediately prior to the development of extensive northern hemisphere glaciation. It thus may provide the best available analog for predicting the climate changes associated with continued global warming. Unfortunately, there are few interior continental records for the early Pliocene from the eastern half of North America and subsequently very little is known about the conditions characterizing climate of this region. The Early Pliocene (4-5 Ma) Pipe Creek Sinkhole (PCS) includes the sediment fill of a complex karst environment that developed in north-central IN (Lat 40° 27' 16", Long 85° 47' 31"). The PCS contains a well-preserved record of sedimentation that includes lacustrine strata with an abundant and diverse fauna and flora that collectively provides a valuable record of paleoclimate from the late Tertiary. Previous research indicates that the floral types are broadly consistent with late Tertiary habitat reconstructions of the US Great Plains. Micromorphologic and stratigraphic analysis of PCS sediments indicate that there are at least three distinct facies present. The underlying red facies is an oxidized silty-clay package that is not fossiliferous. An immature paleosol with root traces represents the pedogenic modification of the red facies and indicates a change in the environment of deposition. The highly fossiliferous lacustrine facies includes abundant quartz sand grains that are not present in the red facies. Geochemical analysis of PCS pond sediment total organic carbon (TOC) derived from vascular land plants sources (based on samples with C/N ratios >20) have δ¹³ C (PDB) isotope values ranging from -15‰ to - 26.2‰ and a mean value of -22.4‰. The red facies averages 0.1% TOC and has δ¹³ C values averaging -20.0‰, whereas the paleosol δ¹³ C values average -24.2‰. These values suggest the presence of a mixture of C3 and C4 plants in the ecosystem. The mean value of PCS fossil wood is - 25.2‰, which is consistent with water-stressed growing conditions. Collectively these records indicate that the region represented by the PCS watershed was substantially dryer during the Early Pliocene than today.
DE: 0473 Paleoclimatology and paleoceanography (3344, 4900)
DE: 0476 Plant ecology (1851)
DE: 0486 Soils/pedology (1865)
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting