Publisher's copyright statement: NOTICE: this is the author's version of a work that was accepted for publication in Palaeogeography, palaeoclimatology, palaeoecology. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reected in this document. Changes may have been made to this work since it was submitted for publication. A denitive version was subsequently published in Palaeogeography, palaeoclimatology, palaeoecology, 265/1-2, 2008Palaeogeography, palaeoclimatology, palaeoecology, 265/1-2, , 10.1016Palaeogeography, palaeoclimatology, palaeoecology, 265/1-2, /j.palaeo.2008 Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. The end of the Eocene greenhouse world was the most dramatic phase in the 9 long-term cooling trend of the Cenozoic Era. Here we show that the Arabia-Eurasia 10 collision and the closure of the Tethys ocean gateway began in the Late Eocene at ~35 11 Ma, up to 25 million years earlier than in many reconstructions. We suggest that 12 global cooling was forced by processes associated with the initial collision that 13 reduced atmospheric CO 2 . These are: 1) waning volcanism across southwest Asia; 2) 14 increased organic carbon storage in Paratethyan basins (e.g. Black Sea and South 15 Caspian); 3) increased silicate weathering in the collision zone and, 4) a shift towards 16 modern patterns of ocean currents, associated with increased vigour in circulation and 17 organic productivity. 18 A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT

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Our new data address the paradox of Late Ordovician glaciation under supposedly high p CO 2 (8 to 22× PAL: preindustrial atmospheric level). The paleobiogeographical distribution of chitinozoan (“mixed layer”) marine zooplankton biotopes for the Hirnantian glacial maximum (440 Ma) are reconstructed and compared to those from the Sandbian (460 Ma): They demonstrate a steeper latitudinal temperature gradient and an equatorwards shift of the Polar Front through time from 55°–70° S to ∼40° S. These changes are comparable to those during Pleistocene interglacial-glacial cycles. In comparison with the Pleistocene, we hypothesize a significant decline in mean global temperature from the Sandbian to Hirnantian, proportional with a fall in p CO 2 from a modeled Sandbian level of ∼8× PAL to ∼5× PAL during the Hirnantian. Our data suggest that a compression of midlatitudinal biotopes and ecospace in response to the developing glaciation was a likely cause of the end-Ordovician mass extinction.

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