ORGANIC MOLECULAR BIOMARKER RECORDS OF PALEOENVIRONMENTAL CHANGE: PITFALLS, UNCERTAINTY AND APPLICATION TO THE SE TIBETAN PLATEAU MARGIN

Organic molecular biomarkers are an important tool for understanding past climate, ecosystems, and environment. In particular, the hydrogen and carbon isotopic compositions of organic biomarkers record the isotopic composition of precipitation or factors that influence stomatal regulation such as moisture and carbon dioxide availability. Organic compounds such as glycerol dialkyl glycerol tetraethers are frequently produced in saturated soils, providing a record of paleotemperature and soil pH. Together, these biomarkers provide valuable records of past environments and may be utilized in depositional settings where there are few other applicable proxies. Furthermore, biomarkers complement inorganic proxy data and enable robust multi-proxy records of past change. Despite the utility of organic biomarkers as a paleoenvironmental proxy, factors such as variations in ecosystems with space or time, uncertainties in the hypsometry of organic matter production and transport and changes in moisture availability and the timing of production of plant waxes can impact the uncertainties associated with biomarker isotopes or soil tetraether temperature reconstruction. This talk will examine the controls of C and H isotope discrimination in modern plant materials, how these relate to environmental factors and uncertainty associated with organic molecular paleoenvironmental reconstruction. Modern calibrations will be applied to paleoenvironmental reconstructions of the Southeastern Tibetan Plateau margin to discuss the Cenozoic evolution of paleoclimate and paleotopography in this region.