John Bershaw

High altitude dentistry; using fossil teeth to understand how and when the Andes formed

John Bershaw

Chevron Deepwater Group

Thursday, March 20th, 2014
CSL 422 – 11:00am

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The Altiplano and Andes Cordillera of South America are one of the most significant topographic features on Earth. Though basic models exist to explain how they formed, the details are not well understood. Recent paleoelevation constraints from fossil leaves and stable isotopes of sedimentary carbonates suggest that significant surface uplift may have occurred over a relatively short period of time, shedding light on the geodynamic mechanisms responsible for the topography seen today. Here, I will present teeth from modern and extinct mammals spanning the late Oligocene (~29 Ma) to present. These teeth preserve a record of surface water isotopes that animals ingested while their teeth were mineralizing. I will show that there is a predictable relationship between tooth isotopes and elevation across the Andes. Tooth data show substantially more positive isotopic compositions (δ18O) for the late Oligocene compared to mid-late Miocene teeth. This suggests that the Andean plateau was at a very low elevation during the late Oligocene and had risen to present-day elevation by the late Miocene. In addition, these data suggest modern climate variations across the Andean plateau have persisted since the late Miocene. Lastly, I will introduce ongoing research on how complexity in modern climate affects environmental isotopes across the Altiplano.