T51C-2896
Surface uplift history of southern Alaska: Insight from stable isotopes
Friday, 18 December 2015
Poster Hall (Moscone South)
Nicholas Steven Bill1, Peter U Clark1, Hari Mix2, Steven W Hostetler3 and Sean P Reilly2, (1)Oregon State University, College of Earth, Ocean, and Atmospheric Sciences, Corvallis, OR, United States, (2)Santa Clara University, Santa Clara, CA, United States, (3)Oregon State University, US Geological Survey, College of Earth, Ocean and Atmospheric Sciences, Corvallis, OR, United States
Abstract:
Understanding of surface uplift complements existing thermochronology efforts to gain a better understanding of the tectonics and regional structure of Alaska. In southern Alaska, several lines of evidence suggest increased rates of exhumation and rock uplift during the late Miocene and early Pliocene, but whether this was accompanied by surface uplift remains uncertain. Here, we measured the hydrogen isotope composition of clay minerals that weathered rapidly from volcanic ash deposited in the interior of Alaska during the time period from the late Miocene to Holocene. This stable isotope record documents an increase of >60‰ in δD since the late Miocene. This is of opposite sign to the expected depletion signal associated with surface uplift. While not consistent with surface uplift, the enrichment presented here could be consistent with changes in seasonality, moisture source and/or vapor recycling through evapotranspiration. We use climate model output as an evaluative tool to understood the controls that may have influenced this isotopic signal, including feedbacks between surface uplift, climate, the hydrologic cycle and the environment.
