Tempo and scale of late Paleocene and early Eocene carbon isotope cycles; implications for the origin of hyperthermals

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doi: 10.1016/j.epsl.2010.09.004
Author(s): Zachos, James C.; McCarren, Heather; Murphy, Brandon; Rohl, Ursula; Westerhold, Thomas
Author Affiliation(s): Primary:
University of California at Santa Cruz, Earth and Planetary Sciences Department, Santa Cruz, CA, United States
University of Bremen, Germany
Volume Title: Earth and Planetary Science Letters
Source: Earth and Planetary Science Letters, 299(1-2), p.242-249. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0012-821X CODEN: EPSLA2
Note: In English. Supplemental information/data is available in the online version of this article. 60 refs.; illus., incl. sketch map
Summary: The upper Paleocene and lower Eocene are marked by several prominent (>1 ppm) carbon isotope (δ13C) excursions (CIE) that coincide with transient global warmings, or thermal maxima, including the Paleocene-Eocene Thermal Maximum (PETM). The CIE, which are recorded mainly in marine sedimentary sequences, have also been identified in continental sequences, occurred episodically, and yet appear to be paced or triggered by orbital forcing. To constrain the timing and scale of the CIE relative to long-term baseline variability, we have constructed a 4.52 million year (myr) long, high-resolution (∼3 kyr) bulk sediment carbon isotope record spanning the lower Eocene to upper Paleocene (C25r-C24n) from a pelagic sediment section recovered at ODP Site 1262 in the southeast Atlantic. This section, which was orbitally-tuned utilizing high-resolution core log physical property and geochemical records, is the most stratigraphically complete upper Paleocene to lower Eocene sequence recovered to date. Time-series analysis of the carbon isotope record along with a high-resolution Fe intensity record obtained by XRF core scanner reveal cyclicity with variance concentrated primarily in the precession (21 kyr) and eccentricity bands (100 and 400-kyr) throughout the upper Paleocene-lower Eocene. In general, minima in δ13C correspond with peaks in Fe (i.e., carbonate dissolution), both of which appear to be in phase with maxima in eccentricity. This covariance is consistent with excess oceanic uptake of isotopically depleted carbon resulting in lower carbonate saturation during periods of high eccentricity. This relationship includes all late Paleocene and early Eocene CIE confirming pacing by orbital forcing. The lone exception is the PETM, which appears to be out of phase with the 400-kyr cycle, though possibly in phase with the 100-kyr cycle, reinforcing the notion that a mechanism other than orbital forcing and/or an additional source of carbon is required to account for the occurrence and unusual scale of this event. Abstract Copyright (2010) Elsevier, B.V.
Year of Publication: 2010
Research Program: ODP Ocean Drilling Program
Key Words: 02 Geochemistry; 12 Stratigraphy, Historical Geology and Paleoecology; Atlantic Ocean; C-13/C-12; Carbon; Carbon cycle; Cenozoic; Climate change; Climate forcing; Cyclic processes; Eccentricity; Eocene; Geochemical cycle; Global change; Global warming; Isotope ratios; Isotopes; Leg 208; Lower Eocene; ODP Site 1262; Ocean Drilling Program; Orbital forcing; Oscillations; Paleocene; Paleocene-Eocene Thermal Maximum; Paleogene; Precession; South Atlantic; Stable isotopes; Statistical analysis; Tertiary; Time series analysis; Upper Paleocene; Walvis Ridge
Coordinates: S271100 S271100 E0013500 E0013400
Record ID: 2011034349
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands