Paleocene–Eocene climatic variation in western North America: Evidence from the δ18O of pedogenic hematite

Abstract

Research Article| September 01, 1999 Paleocene–Eocene climatic variation in western North America: Evidence from the δ18O of pedogenic hematite Huiming Bao; Huiming Bao 1Department of Geosciences, Princeton University, Princeton, New Jersey 08544 Search for other works by this author on: GSW Google Scholar Paul L. Koch; Paul L. Koch 2Department of Earth Sciences, University of California, Santa Cruz, California 95064 Search for other works by this author on: GSW Google Scholar Douglas Rumble, III Douglas Rumble, III 3Geophysical Laboratory, Carnegie Institution, Washington, D.C. 20015 Search for other works by this author on: GSW Google Scholar Author and Article Information Huiming Bao 1Department of Geosciences, Princeton University, Princeton, New Jersey 08544 Paul L. Koch 2Department of Earth Sciences, University of California, Santa Cruz, California 95064 Douglas Rumble, III 3Geophysical Laboratory, Carnegie Institution, Washington, D.C. 20015 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1999) 111 (9): 1405–1415. https://doi.org/10.1130/0016-7606(1999)111<1405:PECVIW>2.3.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Huiming Bao, Paul L. Koch, Douglas Rumble; Paleocene–Eocene climatic variation in western North America: Evidence from the δ18O of pedogenic hematite. GSA Bulletin 1999;; 111 (9): 1405–1415. doi: https://doi.org/10.1130/0016-7606(1999)111<1405:PECVIW>2.3.CO;2 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 Reconstruction of the pre-Pleistocene climate of continental interiors has been hampered by a lack of climatic proxies and limited temporal resolution. We developed a new approach based on the oxygen isotope composition (δ18O) of hematite, which occurs as a coating on fossil vertebrates, and used this method to study climatic change across the Paleocene-Eocene boundary in the Bighorn basin, Wyoming. Hematite coatings form in soils or shallow sediments, and therefore may be used to monitor near-surface conditions.Hematite δ18O values are measured by combining selective leaching, laser fluorination, and mass-balance calculation. These values, in conjunction with δ18O values for co-occurring carbonates, are used to assess the plausibility of published hematite-water oxygen isotope fractionation relations. Though uncertainty remains as to the appropriate fractionation, all are relatively insensitive to temperature variations. Thus, differences in hematite δ18O values most likely reflect shifts in surface-water δ18O values.Analysis of hematites spanning the Paleocene-Eocene transition reveals a roughly 4‰ decrease in the δ18O of surface water in very early Eocene time. This episode probably reflects a cooling event (perhaps as great as 6 °C) that started 0.7 m.y. after the terminal Paleocene δ13C excursion, which corresponds to a pulse of extreme marine warming. Following the cooling, which lasted ∼0.6 m.y., temperatures rebounded to values close to those for late Paleocene time. The cooling episode coincides remarkably well with other indicators of environmental and climatic change from the basin, such as mammalian turnover events and mean annual temperatures estimated from leaf physiognomy. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.