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The Eocene–Oligocene extinction event, also called the Eocene-Oligocene transition (EOT) or Grande Coupure (French for "great cut"), is the transition between the end of the Eocene and the beginning of the Oligocene, an extinction event and faunal turnover occurring between 33.9 and 33.4 million years ago. [1]
Following the maximum was a descent into an icehouse climate from the Eocene Optimum to the Eocene–Oligocene transition at 34 Ma. During this decrease, ice began to reappear at the poles, and the Eocene–Oligocene transition is the period of time when the Antarctic ice sheet began to rapidly expand. [52]
The Eocene-Oligocene Boundary 33.9 million years ago was the transition from the last greenhouse period to the present icehouse climate. [17] [18] [10] At this point, when ~25% more of Antarctica's surface was above sea level and able to support land-based ice sheets relative to today, [19] CO 2 levels had dropped to 750 ppm. [20]
The Eocene-Oligocene transition was a major cooling event and reorganization of the biosphere, [33] [34] being part of a broader trend of global cooling lasting from the Bartonian to the Rupelian. [ 35 ] [ 36 ] The transition is marked by the Oi1 event, an oxygen isotope excursion occurring approximately 33.55 million years ago, [ 37 ] during ...
Entering the Eocene, the tectonic setting shifted back to a collision one, but the mechanisms are not well understood. [45] One of the explanations is the reactivation of the former backarc spreading ridge into a trench by the convection current, causing subduction of the Australian Plate from 55 Ma.
[56] [57] [58] The Grande Coupure is often dated directly to the Eocene-Oligocene boundary at 33.9 Ma, although some estimate that the event began slightly later, at 33.6–33.4 mya. [ 59 ] [ 60 ] The event occurred during or after the Eocene-Oligocene transition , an abrupt shift from a hot greenhouse world that characterised much of the ...
The Priabonian is, in the ICS's geologic timescale, the latest age or the upper stage of the Eocene Epoch or Series. It spans the time between 37.71 and 33.9 Ma . The Priabonian is preceded by the Bartonian and is followed by the Rupelian , the lowest stage of the Oligocene .
TEX 86 has been extensively used to reconstruct Eocene (55-34Ma) SST. During the early Eocene, TEX 86 values indicate warm high southern hemisphere latitude SSTs (20-25 °C) in agreement with other, independently derived proxies (e.g. alkenones, CLAMP, Mg/Ca). During the middle and late Eocene, high southern latitude sites cooled while the ...