2014 GSA Annual Meeting in Vancouver, British Columbia (19–22 October 2014)

Paper No. 209-5
Presentation Time: 10:00 AM

PLACING STABLE ISOTOPE STRATIGRAPHY IN CONTEXT OF DETAILED SEDIMENTOLOGY: A CASE STUDY OF THE PALEOGENE SAGE CREEK BASIN, MONTANA


SCHWARTZ, Theresa M., Geological & Environmental Sciences, Stanford University, 450 Serra Mall, Building 320, Stanford, CA 94305-2115, CHAMBERLAIN, C. Page, Department of Geological Sciences, Stanford University, 450 Serra Mall, Bldng 320, Stanford, CA 94305 and GRAHAM, Stephan A., Department of Geological Sciences, Stanford University, 450 Serra Mall, Bldg. 320, Stanford, CA 94305-2115

The use of stable isotope stratigraphy in paleoclimate, paleoaltimetry, and paleoenvironmental studies has become increasingly popular and insightful in recent years as lab methods continue to evolve. However, challenges with interpreting vertical and lateral variability, as well as statistical viability, in such data remain. Thus, coupling isotopic data with detailed physical stratigraphy is essential to understanding how and why climate signals may vary spatially and temporally. This study is a detailed comparison between suites of stable isotope data that show well-defined shifts in isotope values and the stratigraphy from which they were collected.

Previous stable isotope studies of Paleogene strata in the Sage Creek Basin of southwestern Montana have revealed a large (7-10‰) and rapid (< 2 Ma) negative isotopic shift in δ18O at ~49-47 Ma (Kent-Corson et al., 2006). This shift has been interpreted to be related to a period of extension and volcanism in the Cordilleran orogenic wedge, accompanied by construction of a high, rugged topography that migrated from British Columbia (initiating ca. 55-45 Ma) to Nevada (initiating ca. 40-30 Ma).

The Sage Creek Basin stratigraphy that encompasses this negative isotopic shift was initially measured at relatively low resolution (e.g., meter-scale). This study revisits these sections, emphasizing resampling for paleoclimate indicators in the context of detailed, bed-scale stratigraphic trends. In addition, similar data were collected from age-equivalent successions exposed in adjacent basins in order to assess lateral variability in isotopic and sedimentary signatures. In all of these areas, trends in stable isotope data are compared with trends in detailed sedimentology and changes in sedimentary provenance. Comparisons such as these reveal the reveal the relative timing of tectonic activity and landscape evolution, their effects on climate and drainage reorganization, and when each is manifested in the sedimentary record.

Session No. 209

T126. Stable and Clumped Isotope Record of Topography, Climate, and Environments: Challenges and Recent Advances (Posters)
Tuesday, 21 October 2014: 9:00 AM-6:30 PM
Exhibition Hall C (Vancouver Convention Centre-West)
Geological Society of America Abstracts with Programs. Vol. 46, No. 6, p.518
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