ICHNO-PEDOLOGICAL FACIES OF THE COLTON AND LOWER-MIDDLE GREEN RIVER FORMATIONS: IMPLICATIONS FOR CONTINENTAL PALEOCLIMATE STUDIES

Vertical and lateral changes in ichno-pedological assemblages of the Colton and Lower-Middle Green River Formations in the Uinta Basin, Utah are examined as part of a multidisciplinary study in conjunction with sedimentological and geochemical analysis. The purpose of this study is to examine climatic controls on deposition during the Paleocene-Eocene Thermal Maximum (PETM) and the following hyperthermal events (H1, H2, I1, I2: Cramer et al., 2003; Lourens et al., 2005; Nicolo, 2007) using the sensitivity of organisms, particularly invertebrates, to climatic changes. This study considers soil formation and biogenic behavior to be interlinked (Hasiotis, 2006) and pedogenic features and preserved ichnofossils of the study interval have been given equal consideration in climatic interpretations. Analysis shows a clear correlation between climatic change and seasonality and ichno-pedological assemblages as supported by δ¹³C_org.data. The PETM and post-PETM hyperthermals are recorded as changes in ichno-pedological facies. Aridity, seasonality, and alluvial discharge are all shown to affect soil formation and subsequent preservation.