Orbital climate forcing of δ¹³C excursions in the late Paleocene–early Eocene (chrons C24n–C25n)

Abstract

[1] High-resolution stable carbon isotope records for upper Paleocene-lower Eocene sections at Ocean Drilling Program Sites 1051 and 690 and Deep Sea Drilling Project Sites 550 and 577 show numerous rapid (40-60 kyr duration) negative excursions of up to 1%. We demonstrate that these transient decreases are the expected result of nonlinear insolation forcing of the carbon cycle in the context of a long carbon residence time. The transients occur at maxima in Earth's orbital eccentricity, which result in high-amplitude variations in insolation due to forcing by climatic precession. The construction of accurate orbital chronologies for geologic sections older than $35 Ma relies on identifying a high-fidelity recorder of variations in Earth's orbital eccentricity. We use the carbon isotope records as such a recorder, establishing a robust orbitally tuned chronology for latest Paleoceneearliest Eocene events. Moreover, the transient decreases provide a means of precise correlation among the four sites that is independent of magnetostratigraphic and biostratigraphic data at the <10 5 -year scale. While the eccentricity-controlled transient decreases bear some resemblance to the much larger-amplitude carbon isotope excursion (CIE) that marks the Paleocene/Eocene boundary, the latter event is found to occur near a minimum in the $400-kyr eccentricity cycle. Thus the CIE occurred during a time of minimal variability in insolation, the dominant mechanism for forcing climate change on 10 4 -year scales. We argue that this is inconsistent with mechanisms that rely on a threshold climate event to trigger the Paleocene/Eocene thermal maximum since any threshold would more likely be crossed during a period of high-amplitude climate variations.

Eustatic variations during the Paleocene‐Eocene greenhouse world

“…High-resolution dinocystbased sea level records across hyperthermals, however, have been limited to New Zealand [Crouch and Brinkhuis, 2005], and the North Sea [Powell et al, 1996]. These studies did not examine other independent proxies to confirm results.…”

“…Increase in terrigenous sediment supply for Bass River and Wilson Lake is from Sluijs et al [2007b] and John et al [2008]. Numbers refer to the following sites: site 1, Lomonosov Ridge, Arctic Ocean (SL, TS ); site 2, Doel, North Sea (SL [Steurbaut et al, 2003]); site 3, Basque Region, Bay of Biscay (SL, TS Pujalte and Schmitz, 2006]); site 4, Forada, Central Northern Tethys (TS [Giusberti et al, 2007]); site 5, Turgay Straight (SL [Iakovleva et al, 2001]); site 6, Lodo Formation, California (SL [John et al, 2008]); site 7, Gebel Duwi, Central Southern Tethys (SL [Speijer and Morsi, 2002]); site 8, Tawanui, Southwestern Pacific (TS [Crouch et al, 2003b], SL [Crouch and Brinkhuis, 2005]); and site 9, Clarence River Valley, Southwestern Pacific (TS PETM [Hollis et al, 2005], TS other presumed hyperthermals [Nicolo et al, 2007]). …”

“…2004; Pross and Brinkhuis, 2005;Sluijs et al, 2005;Torricelli et al, 2006], including the late Paleocene and early Eocene [Powell et al, 1996;Bujak and Brinkhuis, 1998;Crouch and Brinkhuis, 2005]. High-resolution dinocystbased sea level records across hyperthermals, however, have been limited to New Zealand [Crouch and Brinkhuis, 2005], and the North Sea [Powell et al, 1996].…”

“…However, high abundances of terrestrial components indicate the site must have been proximal to the coastline [Kaiho et al, 1996;Crouch et al, 2003b]. The Tawanui section yields rich palynological assemblages, which include marine and terrestrial palynomorphs [Crouch et al, 2003b;Crouch and Brinkhuis, 2005]. Dinocysts characteristic of neritic settings are present, but these were likely transported off the shelf [Crouch et al, 2003b].…”

“…[41] The PETM is marked by a prominent CIE in multiple carbon-bearing phases [Kaiho et al, 1996;Crouch et al, 2001;Crouch and Visscher, 2003] (Figure 8). This interval has a significant increase in the amounts of terrestrial palynomorphs, terrestrial organic carbon, and terrigenous minerals [Crouch et al, 2001[Crouch et al, , 2003b.…”