North Atlantic evidence for a unipolar icehouse Climate State at the Eocene-Oligocene transition
North Atlantic evidence for a unipolar icehouse Climate State at the Eocene-Oligocene transition
Earth's climate transitioned from a warm unglaciated state to a colder glaciated “icehouse” state during the Cenozoic. Extensive ice sheets were first sustained on Antarctica at the Eocene-Oligocene Transition (EOT, ~34 Ma), but there is intense debate over whether Northern Hemisphere ice sheets developed simultaneously at this time or tens of millions of years later. Here we report on EOT-age sediments that contain detrital sand from Integrated Ocean Drilling Program Sites U1406 and U1411 on the Newfoundland margin. These sites are ideally located to test competing hypotheses of the extent of Arctic glaciation, being situated in the North Atlantic's “iceberg alley” where icebergs, calved from both the Greenland Ice Sheet today, and the Laurentide Ice Sheet during the Pleistocene, are concentrated by the Labrador Current and deposit continentally derived detritus. Here we show that detrital sand grains present in these EOT-aged sediments from the Newfoundland margin, initially interpreted to represent ice rafting, were sourced from the midlatitudes of North America. We find that these grains were transported to the western North Atlantic by fluvial and downslope processes, not icebergs, and were subsequently reworked and deposited by deep-water contour currents on the Newfoundland margin. Our findings are inconsistent with the presence of extensive ice sheets on southern and western Greenland and the northeastern Canadian Arctic. This contradicts extensive bipolar glaciation at the EOT. The unipolar icehouse arose because of contrasting latitudinal continental configurations at the poles, requiring more intense Cenozoic climatic deterioration to trigger extensive Northern Hemisphere glaciation.
deep-sea currents, Eocene-Oligocene Transition, glaciation, ice-rafted debris, Southeast Newfoundland Ridge
Spray, James F.
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Bohaty, Steven M.
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Davies, Andrew
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Bailey, Ian
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Romans, Brian W.
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Cooper, Matthew J.
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Milton, James A.
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Wilson, Paul A.
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Spray, James F.
436dadc1-f291-4559-ad9a-472c6c5f5bdf
Bohaty, Steven M.
af9dbe78-8b9f-44f2-ba1d-20795837d2d1
Davies, Andrew
df07a781-52d1-4726-98c0-4d522503efc9
Bailey, Ian
e659068f-e591-4185-afd1-5e19a5794bda
Romans, Brian W.
bc69b853-71aa-4e04-bb8c-5eae692129a8
Cooper, Matthew J.
54f7bff0-1f8c-4835-8358-71eef8529e7a
Milton, James A.
9e183221-d0d4-4ddb-aeba-0fdde9d31230
Wilson, Paul A.
f940a9f0-fa5a-4a64-9061-f0794bfbf7c6
Spray, James F., Bohaty, Steven M., Davies, Andrew, Bailey, Ian, Romans, Brian W., Cooper, Matthew J., Milton, James A. and Wilson, Paul A.
(2019)
North Atlantic evidence for a unipolar icehouse Climate State at the Eocene-Oligocene transition.
Paleoceanography and Paleoclimatology.
(doi:10.1029/2019PA003563).
Abstract
Earth's climate transitioned from a warm unglaciated state to a colder glaciated “icehouse” state during the Cenozoic. Extensive ice sheets were first sustained on Antarctica at the Eocene-Oligocene Transition (EOT, ~34 Ma), but there is intense debate over whether Northern Hemisphere ice sheets developed simultaneously at this time or tens of millions of years later. Here we report on EOT-age sediments that contain detrital sand from Integrated Ocean Drilling Program Sites U1406 and U1411 on the Newfoundland margin. These sites are ideally located to test competing hypotheses of the extent of Arctic glaciation, being situated in the North Atlantic's “iceberg alley” where icebergs, calved from both the Greenland Ice Sheet today, and the Laurentide Ice Sheet during the Pleistocene, are concentrated by the Labrador Current and deposit continentally derived detritus. Here we show that detrital sand grains present in these EOT-aged sediments from the Newfoundland margin, initially interpreted to represent ice rafting, were sourced from the midlatitudes of North America. We find that these grains were transported to the western North Atlantic by fluvial and downslope processes, not icebergs, and were subsequently reworked and deposited by deep-water contour currents on the Newfoundland margin. Our findings are inconsistent with the presence of extensive ice sheets on southern and western Greenland and the northeastern Canadian Arctic. This contradicts extensive bipolar glaciation at the EOT. The unipolar icehouse arose because of contrasting latitudinal continental configurations at the poles, requiring more intense Cenozoic climatic deterioration to trigger extensive Northern Hemisphere glaciation.
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Spray_et_al-2019-Paleoceanography_and_Paleoclimatology
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Accepted/In Press date: 20 May 2019
e-pub ahead of print date: 5 June 2019
Keywords:
deep-sea currents, Eocene-Oligocene Transition, glaciation, ice-rafted debris, Southeast Newfoundland Ridge
Identifiers
Local EPrints ID: 432862
URI: http://eprints.soton.ac.uk/id/eprint/432862
ISSN: 2572-4517
PURE UUID: 302a67dd-6c1b-4169-bd25-8d5e2253df48
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Date deposited: 31 Jul 2019 16:30
Last modified: 17 Mar 2024 02:43
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Author:
James F. Spray
Author:
Andrew Davies
Author:
Ian Bailey
Author:
Brian W. Romans
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