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.

High‐resolution sedimentary budget quantification – Example from the Cenozoic deposits in the Pelotas Basin, South Atlantic

“…They proposed that two climatic feedbacks causative of stepwise reductions of erosive power and precipitation over the Andean margin occurred during the Andean growth: one during the Mid‐Eocene (ca. ~42 Ma) climatic optimum, that lasted between 400 and 500 kyr (Bohaty et al., 2009; Westerhold & Röhl, 2013); and a second erosive power reduction in the Late Miocene, a cooling period following the Mid‐Miocene (ca. ~17 to 15 Ma) climatic optimum.…”

Massive and permanent decline of symbiont bearing morozovellids and δ<sup>13</sup>C perturbations across the Early Eocene Climatic Optimum at the Possagno section (Southern Alps of northeastern Italy)

“…It is intriguing to note that the second main crisis of the muricate symbiont bearing forms occurred during the MECO (Fig. 5), that is also a warming event of much longer duration (about 400-500 kyr) than the early Paleogene hyperthermals (Bohaty et al, 2009;Westerhold and Röhl, 2013).…”