The very late Eocene opening of Fram Strait between the Arctic Ocean and the Nordic seas; linkages with the Popigai impact

Author(s): Hillaire-Marcel, C.; Poirier, A.
Author Affiliation(s): Primary:
University of Quebec, Montreal, QC, Canada
Volume Title: AGU 2013 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2013; American Geophysical Union 2013 fall meeting, San Francisco, CA, Dec. 9-13, 2013. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: The transition from the Eocene Arctic Lake to the Arctic Ocean through the opening of Fram Strait, initially dated at ca. 18 Ma based on palynological inferences (Moran et al., 2004, Nature 441, 601-605), has been recently assigned to the very late Eocene (≈ 36 Ma) based on Os-isotope stratigraphy and Re-Os isochron ages of sediments from the IODP-ACEX core (Lomonosov Ridge) (Poirier & Hillaire-Marcel, 2011, GRL 38, L14607). Here, we examine the potential linkages of this event with the Popigai meteoritic impact from northeastern Siberia, which has been dated independently at 35.7±0.2 Ma (Bottomley et al. 1997, Nature 338, 365-368). Noteworthy is the fact that in the earliest marine sediments of the ACEX core, the Os-isotope stratigraphy records an isotopic excursion which we tentatively assigned to the chondritic impactor of Popigai. Sr and Pb isotope signatures of detrital sediments (i.e., following the removal of exchangeable fractions) were thus used to further document the sources of terrigenous sediments deposited before, during, and after the transition episode. Above and below the lacustrine/marine boundary, we note relatively constant source provenances (or mixture of sources), implying that relative contributions from regional detrital sedimentary sources, thus relative erosion rates over surrounding continents, did not change much at a Ma-long time scale. On the other hand, a sharp change highlights the lacustrine/marine transition, with an abrupt shift to low values in 87Sr/88Sr, also marked by a (smaller) excursion in all three 204Pb-normalised lead isotopes values (corrected for in-situ decay of U). This isotopic excursion might also be due to the Popigai chondritic Impactor. The impact-related ejection over basaltic target materials would have produced the particulate matter of suitable composition (Wooden et al. 1993, GCA 57, 3677-3704) to account for the isotopic excursion observed. A first order estimate of the Popigai impact yields a value of ≈ 108 megatons, resulting in a potential seismic event in the Fram Strait area with a magnitude > 10, likely to have resulted in major faulting in the area, thus possibly leading to the opening of the Strait. This very late Eocene opening of Fram Strait, would suggest a potential role of the Arctic basin in the inception of the Atlantic Meridional Overturning Circulation. With this new chronology, the entry of the Earth in the "cold house" system of the Early Oligocene, and the early indices for ice-rafting, might have being nearly synchronous in the Arctic and the circum-Antarctica.
Year of Publication: 2013
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Arctic Coring EXpedition; Arctic Ocean; Cenozoic; Eocene; Fram Strait; Integrated Ocean Drilling Program; Marine sediments; Paleogene; Sediments; Tertiary; Upper Eocene
Record ID: 2015083190
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data supplied by, and/or abstract, Copyright, American Geophysical Union, Washington, DC, United States

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