Revision of the middle Eocene astronomical time scale; new high-resolution stable isotope records between 38 and 49 Ma

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Author(s): Westerhold, Thomas; Röhl, Ursula; Bohaty, Steven; Florindo, Fabio; Frederichs, Thomas; Zachos, James; Agnini, Claudia
Author Affiliation(s): Primary:
University of Bremen, Marum-Center for Marine Environmental Sciences, Bremen, Germany
University of Southampton, United Kingdom
Istituto Nazionale di Geofisica e Vulcanologia, Italy
University of California at Santa Cruz, United States
Universita degli Studi di Padova, Italy
Volume Title: European Geosciences Union general assembly 2019
Source: Geophysical Research Abstracts, Vol.21; European Geosciences Union general assembly 2019, Vienna, Austria, April 7-12, 2019. Publisher: Copernicus GmbH on behalf of the European Geosciences Union (EGU), Katlenburg-Lindau, Germany. ISSN: 1029-7006
Note: In English
Summary: Exploring and understanding causal relationships of climate change during the past 100 million years is strongly dependent on assembling accurate age models of geological archives. Astronomical age models are key to climatic reconstructions, in particular, because they provide high resolution and outstanding accuracy. Establishing a robust astronomical time scale for the middle Eocene between 38 and 48 million years ago has previously proved difficult due to a lack of records of sufficient quality. The middle Eocene has thus remained a 'gap' in the coverage of the Paleogene astronomical timescale. Astronomical tuning of bulk stable isotope and XRF core scanning data from ODP Sites 702 and 1263 spanning the middle Eocene gap was recently challenged by interpretation XRF core scan and magneto-stratigraphic records from IODP Sites U1408 and U1410 (IODP Exp. 342, Paleogene Newfoundland Sediment Drifts, Northwest Atlantic). Notably, the duration of magnetic polarity Chron C20r estimated from the Exp. 342 records is almost 500 kyr shorter in duration than in the 2012 Geomagnetic Polarity Time Scale (GPTS) and more than 600-kyr shorter than astronomically calibrated GPTS estimates derived from the interpretation of data from Sites 702 and 1263. Here we present new magnetostratigraphic as well as high-resolution bulk and benthic stable isotope records from ODP Sites 1051 (Blake Nose, western North Atlantic) and 1263 (Walvis Ridge, South Atlantic) covering the key middle Eocene interval (38-49 Ma, Chrons 18n to 22n). Our new high-resolution benthic stable isotope record from Site 1263 has an average resolution of 5 kyr encompassing the cooling after the Early Eocene Climate Optimum, the Late Lutetian Thermal Maximum, and the Middle Eocene Climate Optimum in unprecedented detail. These records allow further fine tuning of the astronomical time scale for the middle Eocene. Both bulk and benthic carbon isotope data from Sites 1051 and 1263 document overall dominance of eccentricity cycles in global carbon cycle dynamics that allow construction of new astronomical age models. For example, we can now demonstrate that the composite Exp. 342 records (from Sites U1408 and U1410) are erroneous resulting partly in incorrect orbital cycle interpretations as well as revealing extensive gaps and disturbed intervals especially for magnetic polarity Chrons C18r and C20r. [Copyright Author(s) 2019. CC Attribution 4.0 License:]
Year of Publication: 2019
Research Program: IODP Integrated Ocean Drilling Program
ODP Ocean Drilling Program
Key Words: 03 Geochronology; 12 Stratigraphy, Historical Geology and Paleoecology; Absolute age; Atlantic Ocean; Blake Nose; Blake Plateau; Carbon; Cenozoic; Chemostratigraphy; Eocene; Expedition 342; IODP Site U1408; IODP Site U1410; Integrated Ocean Drilling Program; Isotopes; Leg 114; Leg 171B; Leg 208; Magnetostratigraphy; Middle Eocene; North Atlantic; ODP Site 1051; ODP Site 1263; ODP Site 702; Ocean Drilling Program; Paleogene; South Atlantic; Stable isotopes; Tertiary; Time factor; Walvis Ridge
Coordinates: S505648 S505647 W0262207 W0262207
S283200 S283200 E0024700 E0024700
N412617 N412618 W0494708 W0494709
N411941 N411942 W0491011 W0491012
N300311 N300311 W0762128 W0762128
Record ID: 2019050534
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from European Geosciences Union, Munich, Germany