Palaeoclimate reconstructions of periods with warm climates and high atmospheric CO
concentrations are crucial for developing better projections of future climate change. Deep-ocean
and high-latitude
...palaeotemperature proxies demonstrate that the Eocene epoch (56 to 34 million years ago) encompasses the warmest interval of the past 66 million years, followed by cooling towards the eventual establishment of ice caps on Antarctica. Eocene polar warmth is well established, so the main obstacle in quantifying the evolution of key climate parameters, such as global average temperature change and its polar amplification, is the lack of continuous high-quality tropical temperature reconstructions. Here we present a continuous Eocene equatorial sea surface temperature record, based on biomarker palaeothermometry applied on Atlantic Ocean sediments. We combine this record with the sparse existing data
to construct a 26-million-year multi-proxy, multi-site stack of Eocene tropical climate evolution. We find that tropical and deep-ocean temperatures changed in parallel, under the influence of both long-term climate trends and short-lived events. This is consistent with the hypothesis that greenhouse gas forcing
, rather than changes in ocean circulation
, was the main driver of Eocene climate. Moreover, we observe a strong linear relationship between tropical and deep-ocean temperatures, which implies a constant polar amplification factor throughout the generally ice-free Eocene. Quantitative comparison with fully coupled climate model simulations indicates that global average temperatures were about 29, 26, 23 and 19 degrees Celsius in the early, early middle, late middle and late Eocene, respectively, compared to the preindustrial temperature of 14.4 degrees Celsius. Finally, combining proxy- and model-based temperature estimates with available CO
reconstructions
yields estimates of an Eocene Earth system sensitivity of 0.9 to 2.3 kelvin per watt per square metre at 68 per cent probability, consistent with the high end of previous estimates
.
Intriguing latest Eocene land-faunal dispersals between South America and the Greater Antilles (northern Caribbean) has inspired the hypothesis of the GAARlandia (Greater Antilles Aves Ridge) land ...bridge. This landbridge, however, should have crossed the Caribbean oceanic plate, and the geological evolution of its rise and demise, or its geodynamic forcing, remain unknown. Here we present the results of a land-sea survey from the northeast Caribbean plate, combined with chronostratigraphic data, revealing a regional episode of mid to late Eocene, trench-normal, E-W shortening and crustal thickening by ∼25%. This shortening led to a regional late Eocene-early Oligocene hiatus in the sedimentary record revealing the location of an emerged land (the Greater Antilles-Northern Lesser Antilles, or GrANoLA, landmass), consistent with the GAARlandia hypothesis. Subsequent submergence is explained by combined trench-parallel extension and thermal relaxation following a shift of arc magmatism, expressed by a regional early Miocene transgression. We tentatively link the NE Caribbean intra-plate shortening to a well-known absolute and relative North American and Caribbean plate motion change, which may provide focus for the search of the remaining connection between 'GrANoLA' land and South America, through the Aves Ridge or Lesser Antilles island arc. Our study highlights the how regional geodynamic evolution may have driven paleogeographic change that is still reflected in current biology.
Paleocene–Eocene epoch was the turning point when the Indian subcontinent experienced maximum isolation before it collided with Eurasia. Intense sedimentation occurred in late Paleocene in the ...foreland basins of young Himalaya, marking the beginning of a major transgression on the Indian subcontinent. In central Himalaya (Nepal), the synorogenic stratigraphy recorded the depositional environment changes from salt-water to brackish-water and even to fresh-water condition, indicating slight and gradual regressive phase. We report petrography, U–Pb detrital zircons ages, whole-rock geochemistry data from sandstone in Cretaceous–Paleocene, Eocene, and lower Miocene of the Lesser Himalaya, central Nepal. The Eocene and Miocene sequences have small Neoproterozoic to Cambrian age zircon populations indicating multiple source terrains. The whole-rock geochemistry supports the unroofing history documented by U–Pb zircon ages, the succession belongs to foreland basin, an area between the active and passive continental margins tectonic setting. Petrography data indicates a recycled orogenic provenance.
For the first time, we identify the Eocene coal was deposited in tropical and humid conditions based on fauna and flora, geochemistry, fission-track, and Zircon-Helium (ZHe) age. The organic geochemical and organic petrological data suggests the depositional environment of Jhadewa coal of central Nepal in anoxic terrestrial condition signifying a peat-swamp flood basin environment. Therefore, we suggest that the studied coal is formed from ancient submerged peat forests in swampy environments subjected to the geological forces of heat and pressure over millions of years and the tectonic collision might have played an essential role for burial and formation of lignite to bituminous coal.
•Eocene and Miocene sequences show similar detrital zircon U–Pb ages and petrography.•Geochemical data indicates active and passive continental margin tectonic setting.•Eocene coal supposedly deposited in tropical and humid condition.•Peat-swamp flood basin environment showing an oxic terrestrial condition.•Burial of swampy forests to thick coal layer, result of India-Asia collision.
Rapid global warming of 5° to 10°C during the Paleocene-Eocene Thermal Maximum (PETM) coincided with major turnover in vertebrate faunas, but previous studies have found little floral change. Plant ...fossils discovered in Wyoming, United States, show that PETM floras were a mixture of native and migrant lineages and that plant range shifts were large and rapid (occurring within 10,000 years). Floral composition and leaf shape and size suggest that climate warmed by approximately5°C during the PETM and that precipitation was low early in the event and increased later. Floral response to warming and/or increased atmospheric CO₂ during the PETM was comparable in rate and magnitude to that seen in postglacial floras and to the predicted effects of anthropogenic carbon release and climate change on future vegetation.
Specimens of a new fruit genus and species, Alatonucula ignis, from the early Eocene Laguna del Hunco flora of Chubut, Patagonia, Argentina, have characteristics consistent with assignment to ...Juglandaceae. Each fossil fruit consists of a nutlet with an attached wing that varies from unlobed to trilobed. One specimen clearly shows that the nutlet has a single locule partially subdivided into four chambers; its counterpart contains a four-lobed locule cast. The basally partitioned locule with lobed seed indicates that Alatonucula can be placed within Juglandaceae; the overall structure of the fruits suggests affinities to subfamily Engelhardioideae, which typically have fruits consisting of a nutlet attached to a trilobed wing. Parsimony analyses of a morphological matrix for extant and fossil Juglandaceae revised from a previously published study demonstrate that 1) Alatonucula groups with Engelhardioideae; and 2) Paleooreomunnea, an Eocene North American taxon that includes a fruit type with a trilobed wing, is within crown-group Engelhardioideae. Alatonucula, along with fossil juglandaceous pollen from the Paleogene of Patagonia, indicates that Juglandaceae may have had an unexpectedly early presence in South America. Furthermore, these fruits represent a Laurasian biogeographic signal in the Laguna del Hunco flora, which contrasts with the predominantly Australasian signal highlighted in previous studies.
Sakhalotettix eocenicus
gen. & sp. nov.
, the first leafhopper reported from middle Eocene Sakhalinian amber, is described and illustrated. The fossil cicadellid resembles modern Xestocephalini and ...Bathysmatophorini in some respects but, because of its unique combination of traits, cannot be placed with certainty in either group, or in any other modern cicadellid subfamily. It is, therefore, considered to be
incertae sedis
within Cicadellidae.
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