23 May 2023
 | 23 May 2023
Status: this preprint is currently under review for the journal CP.

Nonlinear increase in seawater 87Sr/86Sr in the Oligocene to early Miocene and implications for climate-sensitive weathering

Heather M. Stoll, Leopoldo D. Pena, Ivan Hernandez-Almeida, José Guitián, Thomas Tanner, and Heiko Paelike

Abstract. The 87Sr/86Sr of marine carbonates provides a key constraint on the balance of continental weathering and hydrothermal Sr fluxes to the ocean, and mid-Oligocene to mid-Miocene features the most rapid rates of increase in the 87Sr/86Sr of the Cenozoic. Because previous records of the 87Sr/86Sr increase with time were based on biostratigraphically defined age models in diverse locations, it was difficult to unambigiously distinguish m.y. scale variations in the rate of 87Sr/86Sr change from variations in sedimentation rate. In this study, we produce the first 87Sr/86Sr results from an Oligocene to early Miocene site with a precise age model derived orbital tuning of high resolution benthic δ18O, at the Equatorial Pacific Ocean Drilling Program (ODP) Site 1218. Our new dataset resolves transient decreases in 87Sr/86Sr, as well as periods of relative stasis. These changes can be directly compared with the high resolution benthic δ18O in the same site. We find slowing of the rate of 87Sr/86Sr increase coincides with the onset of Antarctic ice expansion at the beginning of the Mid-Oligocene Glacial Interval, and a rapid steeping in the 87Sr/86Sr increase coincides with the benthic δ18O evidence for rapid ice retreat. This pattern may reflect either northward shifts in the Intertropical Convergence Zone precipitation to areas of nonradiogenic bedrock, and/or lowered weathering fluxes from highly radiogenic glacial flours on Antarctic. We additionally generate the first 87Sr/86Sr data from ODP Site 1168 and International Ocean Discovery Program (IODP) Site 1406 during the Oligocene to early Miocene to improve the precision of age correlation of these Northern Hemisphere and Southern Hemisphere mid-latitude sites, and to better estimate the duration of early Miocene hiatus and condensed sedimentation.

Heather M. Stoll et al.

Status: open (until 18 Jul 2023)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Heather M. Stoll et al.

Heather M. Stoll et al.


Total article views: 154 (including HTML, PDF, and XML)
HTML PDF XML Total BibTeX EndNote
110 39 5 154 1 1
  • HTML: 110
  • PDF: 39
  • XML: 5
  • Total: 154
  • BibTeX: 1
  • EndNote: 1
Views and downloads (calculated since 23 May 2023)
Cumulative views and downloads (calculated since 23 May 2023)

Viewed (geographical distribution)

Total article views: 163 (including HTML, PDF, and XML) Thereof 163 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
Latest update: 03 Jun 2023
Short summary
The Oligocene and Early Miocene periods featured dynamic glacial cycles on Antarctica. In this paper, we use Sr isotopes in marine carbonate sediments to document a change in the location and intensity of continental weathering during short periods of very intense Antartic glaciation. Potentially, the weathering intensity of old continental rocks on Antarctica was reduced during glaciation. We also show improved age models for correlation of Southern ocean and North Atlantic sediments.