Paleoaltimetry

Leaf wax stable isotopes from Northern Tibetan Plateau: Implications for uplift and climate since 15 Ma

Guangsheng Zhuang, Mark T. Brandon, Mark Pagani, Srinath Krishnan

The growth of Tibetan Plateau is considered to have played a key role during the evolution of Asian climate. Our understanding of the relationship between the plateau growth and Asian climate changes is limited, however, due to the scarcity of well-dated sedimentary sequences that could provide parallel information of the evolution of elevation and climate. Here, we report a high-resolution time series record of the stable hydrogen isotopic composition of leaf-wax n-alkanes from a continuous Neogene stratigraphic sequence (15–1.8Ma) from the Qaidam basin on the northern Tibetan Plateau. These data are used to reconstruct the isotopic composition of meteoric waters (δDm) and subsequently applied to interpret the history of paleotopography and climate in Qaidam.

Biomarker Reconstruction of the Early Eocene Paleotopography and Paleoclimate of the Northern Sierra Nevada

Michael T. Hren, Mark Pagani, Diane M. Erwin, and Mark Brandon

We reconstruct ancient temperature and elevation gradients across the early Eocene (52-49 Ma) northern Sierra Nevada (California, United States) using organic molecular proxies that record atmospheric and ground-level effects of topography. Paleoelevation was determined by reconstructing the change in the hydrogen isotopic composition of precipitation and mean annual temperature from the isotopic composition of fossil angiosperm leaf n-alkanes and the distribution of microbially produced soil tetraethers preserved in leaf-bearing sediments. Organic molecular data produce equivalent range-scale and channel paleoelevation estimates that show the northern Sierra Nevada was a warm (6 to 8 degrees C warmer than modern), high-elevation (>2km), and moderate- to low-relief landscape at the Eocene Climatic Optimum. Modern northern Sierra Nevada topography likely reflects post-Paleocene reduction of mean surface elevation and late Cenozoic increases in relief.