Project Details
Projekt
The Mid Pleistocene transition: did marine biological productivity lead to pCO2 changes?"
Applicant
Professorin Dr. Liselotte Diester-Haass
Subject Area
Palaeontology
Term
from 2014 to 2018
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 260765479
The Mid Pleistocene transition (MPT) marks a transition from 41 kyr to 100 kyr cycles in climate and ice volume changes without change in the mode of orbital forcing. Atmospheric pCO2 decreased by about 30 ppm (Wolff et al. 2010, Hönisch et al., 2009). Foraminiferal carbon isotopes display a marked minimum at around 0.9 Ma, the time of emergence of the first major 100 kyr cycles (Raymo et al., 1998).We plan to test the hypothesis whether or not enhanced marine biological productivity played a role in the climatic events of the MPT. It has been shown that enhanced dust input in high latitudes (Martinez-Garcia et al., 2011) during a period of increase in terrestrial aridity (de Menocal, 1995, Dupont et al., 2001) has led to an increase productivity at ODP Site 1090 in the subantarctic South Atlantic. Here we test the global extent of enhanced productivity. Specifically, we ask: 1) Do sites from different climatic and hydrographic regions show concomitant productivity increases during the period of pCO2atm. decrease (~0.9 Ma)? 2) Can transfer of 12C from the continents to the ocean explain the lower marine d13C values? (comparable to findings in the late Miocene (Diester-Haass et al., 2006).We (i.e. my cooperation partners K.Billups (USA) and C. Lear (GB) and I) propose a multiproxy approach to assess changes in paleoproductivity during the MPT and their relation to cold-warm stages and to variations in benthic foraminiferal d13C values. To estimate paleoproductivity, we will measure benthic foraminiferal accumulation rates (BFARs) and derive values in gC/cm² x ky as pioneered by Herguera (2000) and applied by, for example, Diester-Haass et al. (2013 and references herein). We will also employ a relatively new proxy, planktonic foraminiferal U/Ca ratios as an indicator of the sediment redox state of the sediments and paleoproductivity (Mawbey and Lear, 2013). We will also construct parallel records of benthic foraminiferal d13C values from these same samples in order to monitor the d13C of dissolved inorganic carbon of the deep waters, to assess the degree to which the in situ respiration in deep waters can be linked to organic carbon inputs. Benthic foraminiferal d18O values will provide a record of large-scale climate change to which the productivity proxies will be coupled. Together these proxies will allow us to determine the role of export productivity on climate change during this interval of time.We will augment these reconstructions with literature based information about terrestrial input (especially Fe input as a driver of productivity) from XRF data (and new measurements at Marum-Bremen) and from paleobotanical studies (e.g. Dupont et al., 2001; Schefuß et al., 2005; Clarke et al., 2006 ).
DFG Programme
Infrastructure Priority Programmes
International Connection
United Kingdom, USA
Participating Persons
Professorin Dr. Katharina Billups; Professorin Dr. Caroline Lear
