Biomarker reconstruction of the early Eocene paleotopography and paleoclimate of the northern Sierra Nevada

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 (Delta delta D-precip) and mean annual temperature (Delta T-GDGT) (glycerol dialkyl glycerol tetraethers) 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 (delta Dn-alkane) and channel (T-GDGT) paleoelevation estimates that show the northern Sierra Nevada was a warm (>6-8 degrees C warmer than modern), high-elevation (>2 km), 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.