Step-wise change of Asian interior climate preceding the Eocene-Oligocene Transition (EOT)

• Published in: Palaeogeography, Palaeoclimatology, Palaeoecology
• Main Authors: Abels, Hemmo A., Dupont-Nivet, Guillaume, Xiao, Guoqiao, Bosboom, Roderic, Krijgsman, Wout
• Other Authors: Abels, HA (reprint author), Univ Utrecht, Dept Earth Sci, Paleomagnet Lab Ft Hoofddijk, Budapestlaan 17, NL-3584 CD Utrecht, Netherlands., Univ Utrecht, Dept Earth Sci, Paleomagnet Lab Ft Hoofddijk, NL-3584 CD Utrecht, Netherlands., Peking Univ, Minist Educ, Key Lab Orogen Belts & Crustal Evolut, Beijing 100871, Peoples R China., Univ Rennes 1, UMR 6118, F-35042 Rennes, France., China Univ Geosci, Minist Educ, Key Lab Biogeol & Environm Geol, Wuhan 430074, Peoples R China., Univ Utrecht, Dept Earth Sci, Paleomagnet Lab Ft Hoofddijk, Budapestlaan 17, NL-3584 CD Utrecht, Netherlands.
• Format: Journal/Newspaper
• Language: English
• Published: palaeogeography palaeoclimatology palaeoecology 2011
• Subjects: Late Eocene; Doubthouse climate; Eocene-Oligocene Transition (EOT); Terrestrial record; Gypsum; Red beds; Cyclostratigraphy; TIBETAN PLATEAU; LACUSTRINE EVAPORITES; MIDDLE EOCENE; PACIFIC-OCEAN; TERUEL BASIN; XINING BASIN; TARIM BASIN; NE SPAIN; CHINA; PALEOGENE; Pacific; Saline Lake; Ice Sheet
• Online Access: https://hdl.handle.net/20.500.11897/243191; https://doi.org/10.1016/j.palaeo.2010.11.028

Understanding the global climate change from greenhouse to icehouse conditions at the Eocene-Oligocene Transition (DOT) 34 million years ago requires climatic records from oceanic as well as continental realms of the key Late Eocene "doubthouse" period preceding this switch. Here, we report integrated stratigraphic results from well-dated Late Eocene continental mudflat to saline lake paleoenvironments of the Xining Basin (northeastern Tibetan Plateau, western China) recording regional and global change. Cyclostratigraphic analysis strongly suggests continuous dominance of the 41-kyr obliquity cycle in the whole late Eocene interval down to the base of polarity chron C18n.2n at 39 Ma with additional input of the similar to 100-kyr eccentricity cycle up to the base of chron C13r at similar to 34.7 Ma. This might imply that high-latitude climates dominated the area long before the EOT, probably related to incipient ice-volume fluctuations. Furthermore, our results reveal two paleoenvironmental deterioration steps preceding the Eocene-Oligocene Transition. The first step occurs in the top of chron C17n.ln at similar to 36.6 Ma. This age closely corresponds to (1) the high-altitude pollen appearance in chron Cl 6.2r at similar to 36.4 Ma in the same section, (2) the recently dated final retreat of the Tarim Sea in western China, and (3) a shift from precession to obliquity dominance in the Atlantic Ocean. This near co-occurrence suggests global change at this time. We hypothesize this change is related to an increase in incipient ice sheet volume leading to passing threshold conditions for the high-altitude pollen appearance and Tarim Sea retreat, finally leading to decreased moisture availability in the Xining Basin. At the second step, in the base of chron C13r at similar to 34.7 Ma. a substantial increase in clastic sedimentation rates is observed. This might relate to increased climate variability preceding the greenhouse to icehouse transition at the EOT that prevented landscapes to attain equilibrium configurations. (c) 2010 Elsevier By. All rights reserved. Geography, Physical Geosciences, Multidisciplinary Paleontology SCI(E) 21 ARTICLE 3-4 399-412 299