Orbital pacing of Eocene climate during the Middle Eocene Climate Optimum and the chron C19r event: Missing link found in the tropical western Atlantic

Abstract

[1] A high-resolution stratigraphy is essential toward deciphering climate variability in detail and understanding causality arguments of events in earth history. Because the middle to late Eocene provides a perfect testing ground for carbon cycle models to reconstruct the transition from a hothouse to an icehouse world, an accurate time scale is needed to decode climate-driving mechanisms. Here we present new results from ODP Site 1260 (Leg 207) which covers a unique expanded middle Eocene section (magnetochrons C18r to C20r, late Lutetian to early Bartonian) of the tropical western Atlantic including the chron C19r transient hyperthermal event and the Middle Eocene Climate Optimum (MECO). To establish a detailed cyclostratigraphy we acquired iron intensity records by XRF scanning Site 1260 cores. We revise the shipboard composite section, establish a cyclostratigraphy and use the exceptional eccentricity modulated precession cycles for orbital tuning. The new astrochronology revises the age of magnetic polarity chrons C19n to C20n, validates the position of very long eccentricity minima at 40.2 and 43.0 Ma in the orbital solutions and extends the Astronomically Tuned Geological Timescale back to 44 Ma. For the first time the new data provide clear evidence for an orbital pacing of the chron C19r event and a likely involvement of the very long (2.4 myr) eccentricity cycle contributing to the evolution of the MECO.

Orbital forcing of the Paleocene and Eocene carbon cycle

“…As mentioned above, Paleocene‐early Eocene (P/E) long‐term records typically show very little or no power in the obliquity band around 41 kyr (cf., Figure ), which is expected, given the absence of significant ice sheets [ Westerhold et al , ; Zachos et al , ; Westerhold and Röhl , ; Littler et al , ; Meyers , ]. Thus, it is also very unlikely that a tilt signal would be expressed at other, say, lower periods such as at 1.2 Myr due to amplitude modulation (AM) of obliquity as identified during the Oligocene‐Miocene when substantial ice sheets were present [ Shackleton et al , ; Pälike et al , ].…”

Orbital-driven environmental changes recorded at ODP Site 959 (eastern equatorial Atlantic) from the Late Miocene to the Early Pleistocene

“…1) were used to build a composite depth scale for the site (e.g. Evans et al 2004;Westerhold et al 2005Westerhold et al , 2012Westerhold and Röhl 2013), which required several steps (supplementary information, Supplementary Tables 1-3). The cyclic patterns in the depth domain were then orbitally tuned in order to develop a high-resolution age model.…”

Astronomical calibration of the Ypresian timescale: implications for seafloor spreading rates and the chaotic behavior of the solar system?

“…Despite the recent progress in construction of astronomically calibrated age models for the Eocene using geochemical records (Cramer et al, 2003;Lourens et al, 2005;Westerhold et al, 2007;Galeotti et al, 2010;Jovane et al, 2010;Westerhold et al, 2012Westerhold et al, , 2014Westerhold et al, , 2015Westerhold and Röhl, 2013;Littler et al, 2014;Lauretano et al, 2016), a fully consistent astrochronology for the Ypresian is not yet available. Two major issues have to be solved to achieve a complete Ypresian astronomical timescale (YATS): (1) the "50 Ma discrepancy" in magnetostratigraphy (Vandenberghe et al, 2012;Westerhold et al, 2015) and (2) the exact number of 405 kyr eccentricity cycles in magnetochron C23 (Lauretano et al, 2016).…”