Impacts of Cenozoic global cooling, surface uplift, and an inland seaway on South American paleoclimate and precipitation 18O

Abstract

Research Article| March 01, 2012 Impacts of Cenozoic global cooling, surface uplift, and an inland seaway on South American paleoclimate and precipitation δ18O M. Louise Jeffery; M. Louise Jeffery † 1Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, Michigan 48109, USA †E-mail: louisej@umich.edu Search for other works by this author on: GSW Google Scholar Christopher J. Poulsen; Christopher J. Poulsen 1Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, Michigan 48109, USA Search for other works by this author on: GSW Google Scholar Todd A. Ehlers Todd A. Ehlers 1Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, Michigan 48109, USA2Department of Geosciences, Universität Tübingen, 72074 Tübingen, Germany Search for other works by this author on: GSW Google Scholar GSA Bulletin (2012) 124 (3-4): 335–351. https://doi.org/10.1130/B30480.1 Article history received: 06 Jan 2011 rev-recd: 06 Jun 2011 accepted: 14 Jun 2011 first online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation M. Louise Jeffery, Christopher J. Poulsen, Todd A. Ehlers; Impacts of Cenozoic global cooling, surface uplift, and an inland seaway on South American paleoclimate and precipitation δ18O. GSA Bulletin 2012;; 124 (3-4): 335–351. doi: https://doi.org/10.1130/B30480.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Stable isotope records of precipitation δ18O (δ18Oprec) have been used as paleoclimate and paleoelevation archives of orogens. However, interpretation of these records is limited by knowledge of how δ18Oprec responds to changes in global and regional climate during mountain-building events. In this study the influence of atmospheric CO2 levels, the extent of the Antarctic ice sheet, changes in Andean surface elevation, and the presence of the South American inland seaway on climate and δ18Oprec in South America are quantified using the GENESIS v3 atmospheric general circulation model with isotope-tracking capabilities. Results are presented in the context of Cenozoic South American climate and δ18Oprec changes. More specifically, we find: (1) Precipitation rates in the Andes are sensitive to Andean surface elevation, the seaway and, to a lesser extent, CO2 levels. Increasing Andean elevations and the presence of a seaway both cause large increases in precipitation, but in different parts of the Andes. The growth of the Antarctic ice sheet is found to have a small influence on South American precipitation. (2) The stable isotopic composition of precipitation is sensitive to all of the parameters investigated. An increase in δ18Oprec of up to 8‰ is found in simulations with higher atmospheric CO2. In agreement with previous studies, δ18Oprec decreases with increasing Andean elevation by an amount greater than that predicted by the modern adiabatic lapse rate. Furthermore, the presence of an inland seaway causes a decrease in δ18Oprec of 1–8‰ in the northern and central Andes. The amount of depletion is dependent on the isotopic composition of the seaway. Simulations without the Antarctic ice sheet result in δ18Oprec that is 0–3‰ lower than the modern. Finally, time-specific simulations for the Miocene and Eocene show that δ18Oprec has decreased during the Cenozoic and that local geographical gradients of δ18Oprec have increased, particularly in regions of high modern elevation. We demonstrate that in addition to Andean uplift and associated climate change, CO2 levels and an inland seaway are likely to have influenced δ18Ocarb records from South America. Consideration of these global and paleogeographic changes is necessary when interpreting paleoclimate or paleoelevation from stable isotope records of δ18Oprec. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.