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Journal articles on the topic 'Eocene'
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1
Hou, Lianhai, and Per G. P. Ericson. "A Middle Eocene Shorebird from China." Condor 104, no. 4 (November 1, 2002): 896–99. http://dx.doi.org/10.1093/condor/104.4.896.
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Abstract We describe a new species of shorebird, tentatively referred to the family Charadriidae, from the Huadian Formation (Middle Eocene) in Jilin Province, China. In general morphology the specimen closely matches that of an extant charadriid, and corresponds in size to the Killdeer (Charadrius vociferus). If correctly identified this is the oldest record of the Charadriidae. The Middle Eocene paleoenvironment of the Huadian region is thought to have resembled a subtropical swamp. Un Ave Playera de China del Eoceno Medio Resumen. Describimos una nueva especie de ave playera, tentativamente clasificada como de la Familia Charadriidae, de la Formación Huadian (Eoceno Medio) en la Provincia de Jilin, China. En términos de morfología general, el ejemplar coincide mayormente con la morfología de un charádrido actual, y se asemeja en tamaño a Charadrius vociferus. Si la identificación es correcta, este representa el registro más antiguo para la Familia Charadriidae. El paleoambiente del Eoceno Medio de la región de Huadian se asemejaba probablemente a un pantano subtropical.
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Trubin, Y. S. "Family Naticidae of the Tavda formation (Eocene, Western Siberia)." Ruthenica, Russian Malacological Journal 28, no. 1 (March 2, 2018): 11–17. http://dx.doi.org/10.35885/10.35885/ruthenica.2018.28(1).2.
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The present work is one of several planned articles on updating information on the biodiversity of malacofauna and palaeogeography of the Middle-Late Eocen Tavda Sea, which existed in the Western Siberia. Paper contains data on fossil species diversity of the family Naticidae of the Middle and Late Eocene West Siberian Sea and on drill holes. The drill holes indicate predator activity, prey of Naticidae and influence of abiotic factors on their behavior. Previously the invertebrate macroauna of the Eocene of Western Siberia was not studied. As a result, the biodiversity, paleogeography and paleoecology remained incompletely studied. This requires additional collecting, generalization and systematization of paleontological material.
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Strougo, Amin. "The Middle Eocene/Upper Eocene transition in Egypt reconsidered." Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen 186, no. 1-2 (November 19, 1992): 71–89. http://dx.doi.org/10.1127/njgpa/186/1992/71.
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Lygina, E. A., N. V. Pravikova, E. R. Chizhova, T. Yu Tveritinova, E. V. Yakovishina, A. M. Nikishin, M. V. Korotaev, et al. "Eocene seismicity and paleogeography of the Central Crimea." Moscow University Bulletin. Series 4. Geology, no. 5 (December 17, 2022): 68–77. http://dx.doi.org/10.33623/0579-9406-2022-5-68-77.
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The article considers the results of a comprehensive study of the Cretaceous-Eocene deposits of the Central Crimea (Ak-Kaya mount.). The temperature and salinity of the formation of Maastrichtian and Eocene rocks have been determined, and a correlation has been made with the global climatic event EЕСO (Early Eocene Climate Optimum). The synchronicity of the formation of steep submeridional fractures and the basal horizon of the Eocene has been proved. Three major stages of deformation have been identified: pre-Eocene, Eocene, and post-Eocene. It is shown that the Eocene stage corresponds to the formation of paleoseismic dislocations during the main phase of tectonic activity in the Pontids (Eastern Turkey).
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Liliegraven, J. A. "Eocene Revelations." Science 264, no. 5161 (May 13, 1994): 1004–5. http://dx.doi.org/10.1126/science.264.5161.1004.
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Huber, Matthew, and Aaron Goldner. "Eocene monsoons." Journal of Asian Earth Sciences 44 (January 2012): 3–23. http://dx.doi.org/10.1016/j.jseaes.2011.09.014.
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Averianov, Alexander O. "Paleogene Sea Snakes from the Eastern Part of Tethys." Russian Journal of Herpetology 4, no. 2 (October 15, 2011): 128–42. http://dx.doi.org/10.30906/1026-2296-1997-4-2-128-142.
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Nessovophis tamdy gen. et sp. nov. (Nigerophiidae, middle Eocene, Bartonian), Nessovophis zhylga sp. nov. (early Eocene, Ypresian), Palaeophis ferganicus sp. nov. (early Eocene, Ypresian), Palaeophis udovichenkoi sp. nov. (middle – ?late Eocene, Bartonian – ?Priabonian), Palaeophis nessovi sp. nov. (late Eocene, Priabonian), Palaeophis sp. (middle Eocene, Bartonian), and Pterosphenus muruntau sp. nov. (middle Eocene, Bartonian) are described and Vialovophis zhylan Nessov, 1984 (?latest Paleocene) is redescribed on the basis of 45 isolated vertebrae from 8 localities in Kazakhstan, Tajikistan, Kirghizia, Uzbekistan, and Ukraine. Phylogenetic analysis of 8 Cretaceous-Paleogene taxa of sea snakes reveals two monophyletic groups: Palaeophiidae (Palaeophis and Pterosphenus) and Nigerophiidae (Nigerophis, Woutersophis, and Nessovophis).
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Avendaño, Gladys Marcela, Luis Felipe Cruz, Luis Enrique Cruz, and Mario Garcia. "Thermal evolution of Los Cuervos formation in the southern area of the Cesar sub-basin (Colombia), based on geochemical and petrophysical data." Earth Sciences Research Journal 25, no. 2 (July 19, 2021): 179–92. http://dx.doi.org/10.15446/esrj.v25n2.86025.
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The tectonic complexity to which the post-Cretaceous Cesar-Ranchería basin has been subjected has generated alterations in the evolution of its oil system, evidence of this is the lack of stratigraphic record in the Cesar sub-basin belonging to ages ranging from the Eocene to the Early Miocene. These units that are no longer present could have been deposited and eroded during this period of time, leaving their mark on the closest overlying units. Previously mentioned hypothesis oriented this research to study how the basin filling was in the time range from the Eocene to the early Miocene based on both organic (24 Tmax and 14 %Ro data) and inorganic (514 data of porosity) paleo-geothermometer data of Paleocene age formations present in two new wells ANH-LA LOMA-2 and ANH-CR-LOS CEREZOS-1X. In addition to the data provided by the wells drilled for this study, 31 published Tmax and 13 %Ro data from Los Cuervos Formation in the Calenturitas and La Jagua Mines were used. The results obtained indicate that the continuous deposition of sedimentary units did occur from the Paleocene to the middle Eocene and it is expected that the Sedimentitas del Eoceno Formation has reached a thickness between 2.5 to 3.5km with characteristics of quartz sandstones (density and compaction). This thickness of rock began to be eroded in the late Eocene to the Miocene according to recent thermo-chronological studies. The evidence obtained allow to improve the thermal evolution models of the oil system, to establish when the greatest advances were made in the transformation ratios and to estimate how the oldest source rocks of the Cesar sub-basin are currently in the studied area.
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Aubry, Marie-Pierre, and Rehab Salem. "The Dababiya Quarry Core: Coccolith biostratigraphy." Stratigraphy 9, no. 3-4 (2012): 241–59. http://dx.doi.org/10.29041/strat.09.3.08.
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We establish the coccolith stratigraphy of the Maastrichtian through lower Eocene section recovered from the Dababiya Core taken ~200 m from the GSSP for the Paleocene/Eocene boundary, and correlate coccolith biozones with lithostratigraphic units in the core. The section extends from Maestrichtian Subzone CC25a to lowermost Eocene Subzone NP9c. The composite Paleocene-lower Eocene Dababiya section recovered in the core and accessible in outcrop in the DababiyaQuarry exhibits an unexpected contrast in thickness between the Lower Eocene succession (~Esna Shales) and the Paleocene one (~Dakhla Shales and Tarawan Chalk).
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Tribe, Selina. "Eocene paleo-physiography and drainage directions, southern Interior Plateau, British Columbia." Canadian Journal of Earth Sciences 42, no. 2 (February 1, 2005): 215–30. http://dx.doi.org/10.1139/e04-062.
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A map of reconstructed Eocene physiography and drainage directions is presented for the southern Interior Plateau region, British Columbia south of 53°N. Eocene landforms are inferred from the distribution and depositional paleoenvironment of Eocene rocks and from crosscutting relationships between regional-scale geomorphology and bedrock geology of known age. Eocene drainage directions are inferred from physiography, relief, and base level elevations of the sub-Eocene unconformity and the documented distribution, provenance, and paleocurrents of early Cenozoic fluvial sediments. The Eocene landscape of the southern Interior Plateau resembled its modern counterpart, with highlands, plains, and deeply incised drainages, except regional drainage was to the north. An anabranching valley system trending west and northwest from Quesnel and Shuswap Highlands, across the Cariboo Plateau to the Fraser River valley, contained north-flowing streams from Eocene to early Quaternary time. Other valleys dating back at least to Middle Eocene time include the North Thompson valley south of Clearwater, Thompson valley from Kamloops to Spences Bridge, the valley containing Nicola Lake, Bridge River valley, and Okanagan Lake valley. During the early Cenozoic, highlands existed where the Coast Mountains are today. Southward drainage along the modern Fraser, Chilcotin, and Thompson River valleys was established after the Late Miocene.
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Squires, Richard L. "Cephalopods from the late Eocene Hoko River Formation, northwestern Washington." Journal of Paleontology 62, no. 01 (January 1988): 76–82. http://dx.doi.org/10.1017/s002233600005890x.
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Rare specimens of the nautiloidsNautilusandAturiaand extremely rare specimens of a sepiamorph sepiid are described from the late Eocene Hoko River Formation, northern Olympic Peninsula, Washington. The well-preserved partial phragmocones are from channel-fill clastics deposited on the inner and middle slopes of a submarine-fan system.TheNautilusspecimen is allied toN. cookanumWhitfield from middle Eocene strata, New Jersey, and is probably conspecific withNautilussp. (Miller) from late Eocene strata, northwestern Oregon, both of which were previously assigned toEutrephoceras.This is the first record ofNautilusin the northeastern Pacific.TheAturiaspecimen is tentatively identified asA.cf.A. alabamensis(Morton), a species previously only known from late Eocene strata in the Atlantic-Gulf Coastal area and northeastern Mexico.Aturia alabamensismay be the same as numerous Eocene North American aturiid species.The two sepiamorph sepiid specimens resembleBelosepiaVoltz but are probably generically distinct. They are only the second record of sepiids in the Eocene of the northeastern Pacific.
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Squires, Richard L. "Cephalopods from the late Eocene Hoko River Formation, northwestern Washington." Journal of Paleontology 62, no. 1 (January 1988): 76–82. http://dx.doi.org/10.1017/s0022336000018023.
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Rare specimens of the nautiloidsNautilusandAturiaand extremely rare specimens of a sepiamorph sepiid are described from the late Eocene Hoko River Formation, northern Olympic Peninsula, Washington. The well-preserved partial phragmocones are from channel-fill clastics deposited on the inner and middle slopes of a submarine-fan system.TheNautilusspecimen is allied toN. cookanumWhitfield from middle Eocene strata, New Jersey, and is probably conspecific withNautilussp. (Miller) from late Eocene strata, northwestern Oregon, both of which were previously assigned toEutrephoceras.This is the first record ofNautilusin the northeastern Pacific.TheAturiaspecimen is tentatively identified asA.cf.A. alabamensis(Morton), a species previously only known from late Eocene strata in the Atlantic-Gulf Coastal area and northeastern Mexico.Aturia alabamensismay be the same as numerous Eocene North American aturiid species.The two sepiamorph sepiid specimens resembleBelosepiaVoltz but are probably generically distinct. They are only the second record of sepiids in the Eocene of the northeastern Pacific.
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Port, U., M. Claussen, and V. Brovkin. "Radiative forcing by forest and subsequent feedbacks in the early Eocene climate." Climate of the Past Discussions 11, no. 2 (March 30, 2015): 997–1029. http://dx.doi.org/10.5194/cpd-11-997-2015.
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Abstract. Using the Max Planck Institute for Meteorology Earth System Model, we investigate the forcing of forests and the feedback triggered by forests in the pre-industrial climate and in the early Eocene climate (about 54 to 52 million years ago). Other than the interglacial, pre-industrial climate, the early Eocene climate was characterised by high temperatures which led to almost ice-free poles. We compare simulations in which all continents are covered either by dense forest or by bare soil. To isolate the effect of soil albedo, we choose either bright soils or dark soils, respectively. Considering bright soil, forests warm in both, the early Eocene climate and the current climate, but the warming differs due to differences in climate feedbacks. The lapse-rate and water-vapour feedback is stronger in early Eocene climate than in current climate, but strong and negative cloud feedbacks and cloud masking in the early Eocene climate outweigh the stronger positive lapse-rate and water-vapour feedback. In the sum, global mean warming is weaker in the early Eocene climate. Sea-ice related feedbacks are weak in the almost ice-free climate of the early Eocene leading to a weak polar amplification. Considering dark soil, our results change. Forests cools stronger in the early Eocene climate than in the current climate because the lapse-rate and water-vapour feedback is stronger in the early Eocene climate while cloud feedbacks and cloud masking are equally strong in both climates. The different temperature change by forest in both climates highlights the state-dependency of vegetation's impact on climate.
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Tierney, Jessica E., Jaap S. Sinninghe Damsté, Richard D. Pancost, Appy Sluijs, and James C. Zachos. "Eocene temperature gradients." Nature Geoscience 10, no. 8 (August 2017): 538–39. http://dx.doi.org/10.1038/ngeo2997.
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Dilcher, David. "Eocene lake messel." Geochimica et Cosmochimica Acta 54, no. 10 (October 1990): 2901–2. http://dx.doi.org/10.1016/0016-7037(90)90033-h.
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Aladžova-Khrischeva, Kina, Lili Nedjalkova, and Tzanko Tzankov. "Lithostratigraphy and deformations in the Palaeogene sediments from the western and middle parts of the Forebalkan and Stara-Pianina range mountains." Geologica Balcanica 21, no. 6 (December 30, 1991): 49–90. http://dx.doi.org/10.52321/geolbalc.21.6.49.
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The following lithostratigraphic units are introduced: the Iztočnik Formation with the Beljane Member (Lower Eocene), the Pavolče Forfnation (Lower Eocene), the Bojnica Formation (Lower Eocene), the Lukovit Formation with the Âglen Member (Lower and Middle Eocene), the Staropatica Formation (Lower and Middle Eocene) and the Ugârčin Formation (Middle Eocene). The uppermost parts of the Kajlaka Formation have probably an Early Palaeocene Age. All the Palaeogene lithologic bodies represent relics of the sediments in the South Margin of the Late Maastrichtian – Early Palaeocene marine basin, of the shallow·water Nordbulgarian Late Palaeocene marine basin and of the Forebalkan subprovince (with a trough sedimentation) and the Stara-Pianina subprovince (with a more littoral sedimentation) of the Early and Middle Eocene Lower Danube basin. In the investigated area relics of the Early Laramian deformatons are not established. Fragments of the Middle Laramian, Late Laramian and lllirian structural plans have been determined. There are considerable differences between the Middle Laramian and the Illirian fold generations. The Early Illirian folding has been followed by the allozonal and autozonal overthrustings. All these tectonic events have taken place on the rear part of the Southern active continental margin of the European continent (in particular Moesian plate).
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Pigg, Kathleen B., Steven R. Manchester, and Melanie L. Devore. "The early Eocene flora of Horsefly, British Columbia, Canada and its phytogeographic significance." Fossil Imprint 79, no. 2 (2023): 126–43. http://dx.doi.org/10.37520/fi.2023.007.
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About forty species, including a bryophyte, ferns, conifers, Ginkgo, and over 35 angiosperms, are recognized based on compression-impression remains from the early Eocene of Horsefly, British Colombia, Canada. This flora is in the north central part of a chain of late early Eocene fossil assemblages known as floras of the “Okanagan Highlands” (= “Okanogan Highlands” in the US). These floras extend from north central British Columbia, Canada southeast to Republic, Washington, USA. The Horsefly flora shows similarities to other Eocene Okanagan Highlands floras, such as McAbee, Falkland, Thomas Ranch and Republic, but with some additional rare taxa. In the broader sense, the Horsefly flora can be compared with early and middle Eocene floras of eastern Asia and midcontinental North America, but shares fewer elements with Europe. Ginkgo, Metasequoia, Pinus, Palaeocarpinus, ulmaceous leaves and Deviacer are shared with northeastern China as well as western North American sites. Fagopsis, Macginitiea, Dipteronia, Florissantia, Sassafras and Lagokarpos also occur in other western North American Eocene floras and Koelreuteria and Jenkinsella with Eocene paleofloras of China. These comparisons demonstrate probable floristic exchange between northwestern North America and northeastern China via a Beringian route during the late early Eocene.
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Molina, Eustoquio, Concepción Gonzalvo, and Gerta Keller. "The Eocene-Oligocene planktic foraminiferal transition: extinctions, impacts and hiatuses." Geological Magazine 130, no. 4 (July 1993): 483–99. http://dx.doi.org/10.1017/s0016756800020550.
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AbstractBiostratigraphic study and re-examination of 22 late Eocene to early Oligocene sections provides data in support of three and possibly a fourth late Eocene impact events in the G. index Zone during a period of about 1 Ma of the middle Priabonian between 34.7 and 35.7 Ma. No major species extinctions or significant species abundance changes directly coincide with these impact events. Species extinctions are gradual and selective, affecting primarily cool-temperature-intolerant surface dwellers. These extinctions began with the onset of global cooling during the early middle Eocene and culminated near the Eocene/Oligocene boundary. The global cooling was associated with the isolation of Antarctica as Australia moved northward, the development of a circum-Antarctic circulation, growth of Antarctic ice sheet beginning by late middle Eocene time and a change from a thermospheric to thermohaline circulation. We find no evidence that the multiple late Eocene impact events directly contributed to the climatic deterioration already in progress.
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Shamrock, Jamie L., and David K. Watkins. "Eocene calcareous nannofossil biostratigraphy and community structure from Exmouth Plateau, Eastern Indian Ocean (ODPSite 762)." Stratigraphy 9, no. 1 (2012): 1–54. http://dx.doi.org/10.29041/strat.09.1.01.
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A relatively complete section of Eocene (∼33.9-55.8 Ma) pelagic chalk from offshore northwestern Australia was used to analyze range and abundance data of ∼250 Eocene species to test the efficacy of the existing CP (Okada and Bukry 1980) and NP (Martini 1971) biostratigraphic zonation schemes. Changes in nannofossil diversity, abundance, and community structure were monitored through several Eocene paleoenvironmental events, as identified by changes in δ 13C and δ 18O data, to examine variations in surface water conditions. Major changes in nannofossil assemblages, as indicated by dominance crossovers, correspond to paleoenvironmental shifts such as the PETM (Paleocene-Eocene thermal maximum) and the EECO (Early Eocene climatic optimum). This research also provides systematic paleontology and range data for one new genus (Hexadelus) and eight new species or variants (Calcidiscus ellipticus, Cruciplacolithus nebulosus, Cruciplacolithus opacus, Cyclicargolithus parvus, Hexadelus archus, Hayella situliformis var. ovata, Markalius latus, Pedinocyclus annulus) and addresses several taxonomic issues in other Eocene species.
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Banerjee, Amit, and George E. Boyajian. "Selectivity of foraminiferal extinction in the late Eocene." Paleobiology 23, no. 3 (1997): 347–57. http://dx.doi.org/10.1017/s0094837300019722.
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Late Eocene foraminiferal extinction shows diverse patterns of selective morphologic and latitudinal extinction. Taxa with discoidal shape, calcareous tests, and narrow and low-latitudinal ranges are at significantly greater risk of extinction. Elevated extinction intensities in calcareous tests are mainly due to the presence of larger benthic foraminifera that evolved in late Paleocene and diversified through the lower to middle Eocene. Selectivity of late Eocene foraminiferal extinction indicates that this extinction event was not a globally uniform event. Although this result does not verify an extraterrestrial impact or any other proposed cause of extinction, it does constrain the causes of late Eocene extinction. Furthermore, the geography of late Eocene foraminiferal extinction, and previously studied Cenomanian/Turonian extinction, demonstrates that mass extinctions exhibit different patterns of selectivity.
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Zachos, Louis G., and Ann Molineux. "Eocene echinoids of Texas." Journal of Paleontology 77, no. 3 (May 2003): 491–508. http://dx.doi.org/10.1017/s0022336000044206.
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Fourteen species of echinoids ranging in age from early to late Eocene, including four new species, are described from Texas. New taxa include Schizaster (Schizaster) caddoensis from the Reklaw and Weches Formations (Claiborne Group, middle Eocene), Schizaster (Schizaster) stenzeli and Eupatagus texanus from the Weches Formation, and Schizaster (Paraster) susana from the Caddell Formation (Jackson Group, upper Eocene). Fibularia meyeri (Aldrich, 1921) and Fibularia alabamensis Cooke, 1959 are synonymized with Fibularia texana (Twitchell, 1915) from the Weches and Cook Mountain Formations (Claiborne Group, middle Eocene). Other reported species are Linthia hollandi Barry, 1942, from the Sabinetown Formation (Wilcox Group, lower Eocene); Gagaria sp., Protoscutella tuomeyi (Twitchell, 1915), Protoscutella mississippiensis mississippiensis (Twitchell, 1915), Maretia arguta (Clark, 1915), and Linthia? sp. from the Weches Formation; Spatangus? sp. and Eupatagus carolinensis? Clark, 1915 from the Cook Mountain Formation, and Periarchus lyelli (Conrad, 1834) from the Cook Mountain and Caddell Formations. These echinoids are sensitive indicators of depositional environment, in particular their distribution serves as a marker for stenohaline (open marine) environments and illustrates the biogeographic variability along the northeast Texas coast during the Eocene.
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West, Christopher K., David R. Greenwood, Tammo Reichgelt, Alexander J. Lowe, Janelle M. Vachon, and James F. Basinger. "Paleobotanical proxies for early Eocene climates and ecosystems in northern North America from middle to high latitudes." Climate of the Past 16, no. 4 (August 4, 2020): 1387–410. http://dx.doi.org/10.5194/cp-16-1387-2020.
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Abstract. Early Eocene climates were globally warm, with ice-free conditions at both poles. Early Eocene polar landmasses supported extensive forest ecosystems of a primarily temperate biota but also with abundant thermophilic elements, such as crocodilians, and mesothermic taxodioid conifers and angiosperms. The globally warm early Eocene was punctuated by geologically brief hyperthermals such as the Paleocene–Eocene Thermal Maximum (PETM), culminating in the Early Eocene Climatic Optimum (EECO), during which the range of thermophilic plants such as palms extended into the Arctic. Climate models have struggled to reproduce early Eocene Arctic warm winters and high precipitation, with models invoking a variety of mechanisms, from atmospheric CO2 levels that are unsupported by proxy evidence to the role of an enhanced hydrological cycle, to reproduce winters that experienced no direct solar energy input yet remained wet and above freezing. Here, we provide new estimates of climate and compile existing paleobotanical proxy data for upland and lowland midlatitude sites in British Columbia, Canada, and northern Washington, USA, and from high-latitude lowland sites in Alaska and the Canadian Arctic to compare climatic regimes between the middle and high latitudes of the early Eocene – spanning the PETM to the EECO – in the northern half of North America. In addition, these data are used to reevaluate the latitudinal temperature gradient in North America during the early Eocene and to provide refined biome interpretations of these ancient forests based on climate and physiognomic data.
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Kessler, Franz L., John Jong, and Mazlan Madon. "Sedimentary Record of Paleogene Sequences in the Penyu and Malay Basins, Offshore Peninsular Malaysia." Berita Sedimentologi 46, no. 1 (August 7, 2021): 6–20. http://dx.doi.org/10.51835/bsed.2020.46.1.57.
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The Eocene to Lower Oligocene deposits of the Penyu and Malay basins are formed by fluvial-lacustrine deposits with marine influence in the latter. The sequence consists mainly of siltstone, with several intercalations of fine-grained sand and volcanic tuff. Based on well data, Mid-Upper Eocene sediments exist in Penyu Basin in the deeper parts of the half grabens and sub-basins. Hence, this implies the age of basin initiation at Mid-Eocene, rather than Oligocene as traditionally and commonly stated in the literature. By correlation, and as seismic evidences show, Eocene sediments also appear to exist in the deeper, undrilled parts of the Malay Basin, again implying that at the latest, a Mid-Eocene age of basin initiation.In the Penyu Basin, aprominent near-Base Oligocene Unconformity can potentially be correlated to the Base-Tertiary Unconformity in the adjacent Malay Basin, however the latter term implies all Tertiary sequences, including potential Paleogene deposits above the unconformity. Besides, we also observe intra-Eocene unconformities, called the Top N and Top O. The presence of Eocene strata is likely associated with an early phase of extensional tectonism, and probably related to the onset of rifting of the South China Sea continental crust.
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Mandal, J., and Madhav Kumar. "Distribution of palynofossils across the Palaeocene-Eocene Boundary in north-east and western India." Journal of Palaeosciences 46, no. (1-2) (December 31, 1997): 171–76. http://dx.doi.org/10.54991/jop.1997.1336.
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Late Palaeocene-Early Eocene palynoassemblages of north-east and western India have been analysed to assess the behaviour of palynotaxa during the transition. More than 50 per cent of the taxa continue from Palaeocene to Eocene while some are restricted only to Palaeocene. A number of palynotaxa appear in the Early Eocene that may be considered markers. A critical study on the distribution pattern of these palynotaxa indicates that there is no sharp or abrupt change during Palaeocene-Eocene instead the majority of taxa are common and differ only in percentage frequency.
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Goedert, James L. "Giant late Eocene marine birds (Pelecaniformes: Pelagornithidae) from northwestern Oregon." Journal of Paleontology 63, no. 6 (November 1989): 939–44. http://dx.doi.org/10.1017/s0022336000036647.
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Fossil bird bones from the late Eocene Keasey Formation and the latest Eocene Pittsburg Bluff Formation in northwestern Oregon are the earliest records of the pelecaniform family Pelagornithidae for the Pacific Basin. These fossils also represent the first late Eocene records of the family from the Northern Hemisphere, the second late Eocene record worldwide, and indicate that these animals were among the largest of flying birds. Unfortunately, the fragmentary condition of these fossils and the currently confused state of pelagornithid systematics prevents the assignment of these specimens to new species at this time.
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Port, U., M. Claussen, and V. Brovkin. "Radiative forcing and feedback by forests in warm climates – a sensitivity study." Earth System Dynamics Discussions 6, no. 2 (December 14, 2015): 2577–615. http://dx.doi.org/10.5194/esdd-6-2577-2015.
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Abstract. The biogeophysical effect of forests in a climate with permanent high-latitude ice cover has already been investigated. We extend this analysis to warm, basically ice-free climates, and we choose the early Eocene, some 54 to 52 million years ago, as paradigm for such type of climate. We use the Max Planck Institute for Meteorology Earth System Model to evaluate the radiative forcing of forests and the feedbacks triggered by forests in early Eocene and pre-industrial climate, respectively. To isolate first-order effects, we compare idealised simulations in which all continents are covered either by dense forests or by deserts with either bright or dark soil. In comparison with desert continents covered by bright soil, forested continents warm the planet in the early Eocene climate and in the pre-industrial climate. The warming can be attributed to different feedback processes, though. The lapse-rate – water-vapour feedback is stronger in early Eocene climate than in pre-industrial climate, but strong and negative cloud-related feedbacks nearly outweigh the positive lapse-rate – water-vapour feedback in the early Eocene climate. Subsequently, global mean warming by forests is weaker in the early Eocene climate than in the pre-industrial climate. Sea-ice related feedbacks are weak in the almost ice-free climate of the early Eocene, thereby leading to a weaker high-latitude warming by forests than in the pre-industrial climate. When the land is covered with dark soils, forests cool the early Eocene climate stronger than the pre-industrial climate because the lapse-rate and water-vapour feedbacks are stronger in the early Eocene climate. Cloud-related feedbacks are equally strong in both climates. We conclude that radiative forcing by forests varies little with the climate state, while most subsequent feedbacks depend on the climate state.
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Baatsen, Michiel, Anna S. von der Heydt, Matthew Huber, Michael A. Kliphuis, Peter K. Bijl, Appy Sluijs, and Henk A. Dijkstra. "The middle to late Eocene greenhouse climate modelled using the CESM 1.0.5." Climate of the Past 16, no. 6 (December 23, 2020): 2573–97. http://dx.doi.org/10.5194/cp-16-2573-2020.
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Abstract. The early and late Eocene have both been the subject of many modelling studies, but few have focused on the middle Eocene. The latter still holds many challenges for climate modellers but is also key to understanding the events leading towards the conditions needed for Antarctic glaciation at the Eocene–Oligocene transition. Here, we present the results of CMIP5-like coupled climate simulations using the Community Earth System Model (CESM) version 1. Using a new detailed 38 Ma geography reconstruction and higher model resolution compared to most previous modelling studies and sufficiently long equilibration times, these simulations will help to further understand the middle to late Eocene climate. At realistic levels of atmospheric greenhouse gases, the model is able to show overall good agreement with proxy records and capture the important aspects of a warm greenhouse climate during the Eocene. With a quadrupling of pre-industrial concentrations of both CO2 and CH4 (i.e. 1120 ppm and ∼2700 ppb, respectively, or 4 × PIC; pre-industrial carbon), sea surface temperatures correspond well to the available late middle Eocene (42–38 Ma; ∼ Bartonian) proxies. Being generally cooler, the simulated climate under 2 × PIC forcing is a good analogue for that of the late Eocene (38–34 Ma; ∼ Priabonian). Terrestrial temperature proxies, although their geographical coverage is sparse, also indicate that the results presented here are in agreement with the available information. Our simulated middle to late Eocene climate has a reduced Equator-to-pole temperature gradient and a more symmetric meridional heat distribution compared to the pre-industrial reference. The collective effects of geography, vegetation, and ice account for a global average 5–7 ∘C difference between pre-industrial and 38 Ma Eocene boundary conditions, with important contributions from cloud and water vapour feedbacks. This helps to explain Eocene warmth in general, without the need for greenhouse gas levels much higher than indicated by proxy estimates (i.e. ∼500–1200 ppm CO2) or low-latitude regions becoming unreasonably warm. High-latitude warmth supports the idea of mostly ice-free polar regions, even at 2 × PIC, with Antarctica experiencing particularly warm summers. An overall wet climate is seen in the simulated Eocene climate, which has a strongly monsoonal character. Equilibrium climate sensitivity is reduced (0.62 ∘C W−1 m2; 3.21 ∘C warming between 38 Ma 2 × PIC and 4 × PIC) compared to that of the present-day climate (0.80 ∘C W−1 m2; 3.17 ∘C per CO2 doubling). While the actual warming is similar, we see mainly a higher radiative forcing from the second PIC doubling. A more detailed analysis of energy fluxes shows that the regional radiative balance is mainly responsible for sustaining a low meridional temperature gradient in the Eocene climate, as well as the polar amplification seen towards even warmer conditions. These model results may be useful to reconsider the drivers of Eocene warmth and the Eocene–Oligocene transition (EOT) but can also be a base for more detailed comparisons to future proxy estimates.
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MAKARKIN, VLADIMIR N., GWEN S. ANTELL, and S. BRUCE ARCHIBALD. "A revision of Chrysopidae (Neuroptera) from the late Eocene Florissant Formation, Colorado, with description of new species." Zootaxa 5133, no. 3 (May 5, 2022): 301–45. http://dx.doi.org/10.11646/zootaxa.5133.3.1.
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The green lacewings (Neuroptera: Chrysopidae) of the late Eocene Florissant Formation (Colorado, USA) are revised. Thirteen species in six genera of Nothochrysinae are recognized, including four new species: Archaeochrysa cockerelli sp. nov., Cimbrochrysa americana sp. nov., C. major sp. nov., and Lithochrysa meyeri sp. nov. The validity of the genus Dyspetochrysa Adams, 1967 is tenuous; it might be a synonym of Archaeochrysa Adams, 1967. Lithochrysa Carpenter, 1935 and L. ferruginea (Cockerell, 1909) are considered a valid genus and species. A lectotype and paralectotype of Tribochrysa firmata Scudder, 1890 are designated. The genus Cimbrochrysa Schlüter, 1982 is recorded from North America for the first time. Eocene chrysopid assemblages are briefly analyzed. The late Eocene Florissant assemblage is less diverse than those of early Eocene North America, and greatly differs from late Eocene European assemblages.
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Hernitz Kučenjak, Morana, Vlasta Premec Fućek, Renata Slavković, and Ivan Mesić. "Planktonic Foraminiferal Biostratigraphy of the Late Eocene and Oligocene in the Palmyride Area, Syria." Geologia Croatica 59, no. 1 (2006): 19–39. http://dx.doi.org/10.4154/gc.2006.02.
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Three deep exploration wells in the Palmyride area (Syria) have beendrilled through Oligocene and Eocene deposits. A detailed micropalaeontological investigation has been performed on the planktonic foraminiferal assemblage from drill cuttings. Standard planktonic foraminiferal zones from P15 to P22 (E15 to O6) have been identified.The test morphology and diversity of the foraminiferal assemblageindicate a general cooling trend during the late Eocene andOligocene. The specialized Eocene forms (K-mode life strategy) suchas turborotaliids, globigerinathekids and hantkeninids become extinctin the uppermost late Eocene. The Oligocene is characterized by thedominance of cooler, opportunistic planktonic foraminifera (r-modelife strategy), such as pseudohastigerinids, chiloguembelinids, globigerinids and tenuitellids. A very low number of benthic foraminiferain late Eocene cuttings implies sedimentation in a deep, open seaenvironment. A gradual increase of the benthic foraminiferal proportionthrough the Oligocene indicates shallowing of the sedimentaryenvironment.
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Steinthorsdottir, Margret, Vivi Vajda, Mike Pole, and Guy Holdgate. "Moderate levels of Eocene pCO2 indicated by Southern Hemisphere fossil plant stomata." Geology 47, no. 10 (August 12, 2019): 914–18. http://dx.doi.org/10.1130/g46274.1.
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Abstract Reducing the uncertainty in predictions of future climate change is one of today’s greatest scientific challenges, with many significant problems unsolved, including the relationship between pCO2 and global temperature. To better constrain these forecasts, it is meaningful to study past time intervals of global warmth, such as the Eocene (56.0–33.9 Ma), serving as climatic analogues for the future. Here we reconstructed pCO2 using the stomatal densities of a large fossil Lauraceae (laurel) leaf database from ten sites across the Eocene of Australia and New Zealand. We show that mostly moderate pCO2 levels of ∼450–600 ppm prevailed throughout the Eocene, levels that are considerably lower than the pCO2 forcing currently needed to recreate Eocene temperatures in climate models. Our data record significantly lower pCO2 than inferred from marine isotopes, but concur with previously published Northern Hemisphere Eocene stomatal proxy pCO2. We argue that the now globally consistent stomatal proxy pCO2 record for the Eocene is robust and that climate sensitivity was elevated and/or that additional climate forcings operated more powerfully than previously assumed.
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Huang, Huasheng, Robert Morley, Alexis Licht, Guillaume Dupont-Nivet, Friðgeir Grímsson, Reinhard Zetter, Jan Westerweel, Zaw Win, Day Wa Aung, and Carina Hoorn. "Eocene palms from central Myanmar in a South-East Asian and global perspective: evidence from the palynological record." Botanical Journal of the Linnean Society 194, no. 2 (July 15, 2020): 177–206. http://dx.doi.org/10.1093/botlinnean/boaa038.
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Abstract In the Palaeogene, pollen assemblages at low and mid latitudes are characterized by abundant palm and palm-like (PPL) taxa. Although these taxa have been widely reported, their occurrence in the Palaeogene of Myanmar remains poorly documented. Here we report on the morphology of PPL pollen along a middle to upper Eocene sedimentary sequence in central Myanmar and discuss their nearest living relatives (NLRs). Principal components analysis (PCA) indicates that Palmaepollenites kutchensis, Dicolpopollis and Longapertites were dispersed from freshwater plants, whereas the parent taxon of Proxapertites operculatus was probably a member of the coastal vegetation in the manner of Spinizonocolpites. This, with sedimentological data, suggests a palaeoenvironmental change from a brackish, tidally influenced environment to a fully freshwater setting through the late Eocene. Additionally, we mapped and compared the geographical distribution of selected Eocene palm taxa and their NLRs, and found that their distributions shrank after the Eocene. Moreover, in the Palaeogene, species diversity of selected PPL taxa seems lower in Myanmar than in the Indian subcontinent and other regions in South-East Asia. We hypothesize that in the Eocene the Indo–Asian collision zone formed a ‘hotspot’ for palm diversity, which is reflected in species-rich palynofloras. However, the local palm diversity declined after the Eocene, whereas, at the global level, palm distribution was distinctly reduced between the Eocene and the present. We propose that the retreat of the palms may have occurred as early as the Eocene – Oligocene Transition (EOT), but this remains to be confirmed by the study of EOT pollen records in tropical regions.
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Jaramillo, Carlos A. "Response of tropical vegetation to Paleogene warming." Paleobiology 28, no. 2 (2002): 222–43. http://dx.doi.org/10.1666/0094-8373(2002)028<0222:rotvtp>2.0.co;2.
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The late Paleocene-early Eocene transition was characterized by a long period of global warming that culminated with the highest temperatures of the Cenozoic. This interval is associated with a significant increase in plant diversity in temperate latitudes. However, data from tropical regions remain largely unknown. The record of pollen and spore diversity across the late Paleocene to the early middle Eocene of eight sections in central and eastern Colombia was analyzed. Several techniques, including range-through method, rarefaction, bootstrap, detrended correspondence analysis, and Shannon index, were used to assess the significance of the observed diversity pattern. The palynofloral record indicates that the lower to middle Eocene contains a significantly higher palynofloral diversity than the underlying upper Paleocene strata. This pattern is maintained after accounting for sample size, number of samples/time unit, lithofacies, and depositional systems. Eocene palynofloras have higher alpha and beta diversities and a higher equitability than Paleocene palynofloras. This increase in diversity is the product of a gradual increase in the rate of first appearances and a gradual decrease in the rate of last appearances. The early to middle Eocene increase in diversity, as well as the increase in spore abundance and diversity, suggests that tropical (equatorial) climate became wetter during the early to middle Eocene. This interpretation favors causes for early Eocene warming that do not involve significant increases in greenhouse gases. Samples from strata associated with the Paleocene/Eocene thermal maximum were barren for palynomorphs, and the effects of this climatic event on tropical vegetation remains uncertain.
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Lyubarsky, G., and E. Perkovsky. "New Species of Stilbus (Coleoptera, Clavicornia, Phalacridae) from the Late Eocene Rovno Amber." Vestnik Zoologii 45, no. 2 (January 1, 2011): e-47-e-50. http://dx.doi.org/10.2478/v10058-011-0012-7.
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New Species ofStilbus(Coleoptera, Clavicornia, Phalacridae) from the Late Eocene Rovno AmberThe first Eocene species ofStilbusSeidlitz, 1872,S. bedovoyiLyubarsky et Perkovsky, sp. n., is described from Late Eocene Rovno amber.S. bedovoyiis most similar toStilbus atomarius(Linnaeus) and differs from it by smaller body size, strong and large punctation of elytra, and broadly oval apex of elytra.
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NGÔ-MULLER, VALERIE, ROMAIN GARROUSTE, and ANDRÉ NEL. "The oldest long-legged fly of the subfamily Medeterinae (Diptera: Dolichopodidae) from the Early Eocene of France." Palaeoentomology 3, no. 2 (April 30, 2020): 173–79. http://dx.doi.org/10.11646/palaeoentomology.3.2.6.
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We describe Paleothrypticus eocenicus gen. et sp. nov., oldest and first Medeterinae from the Early Eocene Oise amber (France). Representatives of the tribes Medeterini and Systenini are recorded in the Middle Eocene Baltic amber and the Miocene amber of Mexico. These fossils show that this subfamily was already well diversified at the beginning of the Eocene.
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NEL, ANDRÉ. "The second genus of the extinct dragonfly family Urolibellulidae from the Eocene Green River Formation (Odonata, Anisoptera: Cavilabiata)." Palaeoentomology 3, no. 1 (February 26, 2020): 050–53. http://dx.doi.org/10.11646/palaeoentomology.3.1.7.
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If the oldest record of the anisopteran ‘libelluloid’ group Anauriculida Bechly, 1996 goes to the Cretaceous (Fleck et al., 1999; Kohli et al., 2016), its extant families are scarce or even absent before the Eocene. Nevertheless, the Anauriculida were already rather diverse during Eocene with a Libellulidae in the earliest Eocene (Fleck et al., 2000), and the extinct monotypic family Urolibellulidae in the middle Eocene Green River Formation (Zeiri et al., 2015). Crown Libellulidae become more and more frequent and diverse during Oligocene, and even dominate the dragonfly fauna in some outcrops (Céreste, Rott, Aix-en-Provence, Bes-Konak) (Nel & Paicheler, 1993). Thus any discovery in the Paleocene–Eocene of a new fossil related to these families is welcome. Here we describe a complete hindwing of this kind from the Green River Formation in Colorado.
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Pascher, K. M., C. J. Hollis, S. M. Bohaty, G. Cortese, and R. M. McKay. "Expansion and diversification of high-latitude radiolarian assemblages in the late Eocene linked to a cooling event in the Southwest Pacific." Climate of the Past Discussions 11, no. 4 (July 9, 2015): 2977–3018. http://dx.doi.org/10.5194/cpd-11-2977-2015.
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Abstract. The Eocene was characterised by "greenhouse" climate conditions that were gradually terminated by a long-term cooling trend through the middle and late Eocene. This long-term trend was determined by several large-scale climate perturbations that culminated in a shift to "ice-house" climates at the Eocene–Oligocene Transition. Geochemical and micropaleontological proxies suggest that tropical-to-subtropical sea-surface temperatures persisted into the late Eocene in the high-latitude Southwest Pacific Ocean. Here, we present radiolarian microfossil assemblage and foraminiferal oxygen and carbon stable isotope data from Deep Sea Drilling Project (DSDP) Sites 277, 280, 281 and 283 from the middle Eocene to early Oligocene (~ 40–33 Ma) to identify oceanographic changes in the Southwest Pacific across this major transition in Earth's climate history. The Middle Eocene Climatic Optimum at ~ 40 Ma is characterised by a negative shift in foraminiferal oxygen isotope values and a radiolarian assemblage consisting of about 5 % of low latitude taxa Amphicraspedum prolixum group and Amphymenium murrayanum. In the early late Eocene at ~ 37 Ma, a positive oxygen isotope shift can be correlated to the Priabonian Oxygen Isotope Maximum (PrOM) event – a short-lived cooling event recognized throughout the Southern Ocean. Radiolarian abundance, diversity, and preservation increase during the middle of this event at Site 277 at the same time as diatoms. The PrOM and latest Eocene radiolarian assemblages are characterised by abundant high-latitude taxa. These high-latitude taxa also increase in abundance during the late Eocene and early Oligocene at DSDP Sites 280, 281 and 283 and are associated with very high diatom abundance. We therefore infer a~northward expansion of high-latitude radiolarian taxa onto the Campbell Plateau towards the end of the late Eocene. In the early Oligocene (~ 33 Ma) there is an overall decrease in radiolarian abundance and diversity at Site 277, and diatoms are absent. These data indicate that, once the Tasman Gateway was fully open in the early Oligocene, a frontal system similar to the present day was established, with nutrient-depleted subantarctic waters bathing the area around DSDP Site 277, resulting in a more oligotrophic siliceous plankton assemblage.
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Lyubarsky, G., and E. Perkovsky. "The First Eocene Species of the Genus Micrambe (Coleoptera, Clavicornia, Cryptophagidae)." Vestnik Zoologii 44, no. 3 (January 1, 2010): e-37-e-40. http://dx.doi.org/10.2478/v10058-010-0017-7.
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The First Eocene Species of the GenusMicrambe(Coleoptera, Clavicornia, Cryptophagidae)Based on a fossil specimen from the Late Eocene Rovno amber (Ukraine),Micrambe sarnensisLyubarsky et Perkovsky, sp. n., the first Eocene species of this genus is described. The new species is similar to the extantMicrambe abietis(Paykull) andM. ulicis(Stephens), differing by having the callosity with an acutangular caudolateral corner.
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Lyubarsky, G., and E. Perkovsky. "The First Eocene Species of the Genus Cryptophagus (Coleoptera, Clavicornia, Cryptophagidae)." Vestnik Zoologii 46, no. 1 (January 1, 2012): e-36-e-40. http://dx.doi.org/10.2478/v10058-012-0007-z.
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The First Eocene Species of the GenusCryptophagus(Coleoptera, Clavicornia, Cryptophagidae)Based on a fossil specimen from the Late Eocene Rovno amber (Ukraine),Cryptophagus harenusLyubarsky et Perkovsky, sp. n., an Eocene species of this genus is described. The new species is similar to the extant desert speciesCryptophagus desertusLyubarsky andC. recticollisSolsky, differing by the large callosity occupying 1/4 length of lateral margin of pronotum.
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Herold, N., J. Buzan, M. Seton, A. Goldner, J. A. M. Green, R. D. Müller, P. Markwick, and M. Huber. "A suite of Early Eocene (~55 Ma) climate model boundary conditions." Geoscientific Model Development Discussions 7, no. 1 (January 17, 2014): 529–62. http://dx.doi.org/10.5194/gmdd-7-529-2014.
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Abstract. We describe a set of Early Eocene (~55 Ma) climate model boundary conditions constructed in a self-consistent reference frame and incorporating recent data and methodologies. Given the growing need for uniform experimental design within the Eocene climate modelling community, we make publically available our datasets of Eocene topography, bathymetry, tidal dissipation, vegetation, aerosol distributions and river runoff. Particularly our Eocene topography and bathymetry has been significantly improved compared to previously utilized boundary conditions. Major improvements include the paleogeography of Antarctica, Australia, Europe, the Drake Passage and the Isthmus of Panama, and our boundary conditions include modelled estimates of Eocene aerosol distributions and tidal dissipation for the first time, both consistent with our paleotopography and paleobathymetry. The resolution of our datasets (1° × 1°) is also unprecedented and will facilitate high resolution climate simulations. In light of the inherent uncertainties involved in reconstructing global boundary conditions for past time periods these datasets should be considered as one interpretation of the available data. This paper marks the beginning of a process for reconstructing a set of accurate, open-access Eocene boundary conditions for use in climate models.
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Yan, Kai, Chunlian Wang, Renyi Chen, Jiuyi Wang, Ruiqin Li, and Lihong Liu. "The Geochemical Characteristics and Environmental Implications of the Paleocene–Eocene in the Jiangling Depression, Southwestern Jianghan Basin." Minerals 14, no. 3 (February 26, 2024): 234. http://dx.doi.org/10.3390/min14030234.
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Various isotopic and palynological indicators have shown interspersed periods of aridity and humidity for the late Paleocene to early Eocene in central China, so the paleoclimate conditions remain unclear. This research investigates the environmental characteristics of a saline lake in the Jiangling depression, southwestern Jianghan Basin, from the Paleocene to the Eocene, using bulk-rock geochemistry in a 1280 m sediment core. The ratios of FeO/MnO, Al2O3/MgO, and C-value indicate a semi-humid to semi-arid climate in the early–middle Paleocene. There was a rapid shift to a humid climate during the late Paleocene to early Eocene, following a short time of intense dryness. The Eocene climate was arid, but experienced intermittent humidity. The variation trend of the CIA, CIW and PIA was similar to that of FeO/MnO, Al2O3/MgO, and the C-value, so chemical weathering of the surrounding rocks was controlled by climate change. The lake redox conditions in the Jiangling depression from the Paleocene to the Eocene were reconstructed using the ratios of U/Th, Ni/Co, and V/Cr. During humidity and alternations of aridity and humidity, the lake water received external water input, resulting in weak stratification, so the sediments were in oxidizing conditions. During aridity, lakes become endorheic, leading to sediments forming in reduced conditions. The salinity of the lake in the Jiangling depression from the Paleocene to the Eocene was determined through analysis of sedimentary sequences and the trend of the Sr/Ba ratio. In the early–middle Paleocene, lake salinity varied greatly. From the late Paleocene to the early Eocene, lake salinity decreased. In the Eocene, lake salinity increased and halite precipitated, but lake salinity finally decreased due to a humid climate. During the late Paleocene–early Eocene, the occurrence of multiple humid climates in the Jiangling depression were not merely regional effects. The most significant humidity was caused by a global hyperthermal (PETM), which caused a huge increase in precipitation in the whole of East Asia and even in low latitudes around the world.
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DROHOJOWSKA, JOWITA, WERONIKA BOGUSIAK, SONIA KURKINA, MARZENA ZMARZŁY, and JACEK SZWEDO. "A new species of Eocene whitefly—Snotra herczeki sp. nov. (Hemiptera, Sternorrhyncha, Aleyrodidae) from Baltic amber." Zootaxa 5382, no. 1 (December 7, 2023): 139–45. http://dx.doi.org/10.11646/zootaxa.5382.1.15.
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The second species of the Aleyrodinae whitefly genus Snotra Szwedo et Drohojowska, 2016 is described based on an inclusion in the Eocene Baltic amber. It is second species of the genus, adding new data to knowledge on disparity and taxonomic diversity of whiteflies in the Eocene Baltic amber. The diversity of the group and its fossil record in the Eocene fossil resins is briefly discussed.
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Port, Ulrike, Martin Claussen, and Victor Brovkin. "Radiative forcing and feedback by forests in warm climates – a sensitivity study." Earth System Dynamics 7, no. 3 (July 6, 2016): 535–47. http://dx.doi.org/10.5194/esd-7-535-2016.
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Abstract. We evaluate the radiative forcing of forests and the feedbacks triggered by forests in a warm, basically ice-free climate and in a cool climate with permanent high-latitude ice cover using the Max Planck Institute for Meteorology Earth System Model. As a paradigm for a warm climate, we choose the early Eocene, some 54 to 52 million years ago, and for the cool climate, the pre-industrial climate, respectively. To isolate first-order effects, we compare idealised simulations in which all continents are covered either by dense forests or by deserts with either bright or dark soil. In comparison with desert continents covered by bright soil, forested continents warm the planet for the early Eocene climate and for pre-industrial conditions. The warming can be attributed to different feedback processes, though. The lapse-rate and water-vapour feedback is stronger for the early Eocene climate than for the pre-industrial climate, but strong and negative cloud-related feedbacks nearly outweigh the positive lapse-rate and water-vapour feedback for the early Eocene climate. Subsequently, global mean warming by forests is weaker for the early Eocene climate than for pre-industrial conditions. Sea-ice related feedbacks are weak for the almost ice-free climate of the early Eocene, thereby leading to a weaker high-latitude warming by forests than for pre-industrial conditions. When the land is covered with dark soils, and hence, albedo differences between forests and soil are small, forests cool the early Eocene climate more than the pre-industrial climate because the lapse-rate and water-vapour feedbacks are stronger for the early Eocene climate. Cloud-related feedbacks are equally strong in both climates. We conclude that radiative forcing by forests varies little with the climate state, while most subsequent feedbacks depend on the climate state.
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Liu, X. Y., Q. Gao, M. Han, and J. H. Jin. "The <i>p</i>CO<sub>2</sub> estimates of the late Eocene in South China based on stomatal density of <i>Nageia</i> Gaertner leaves." Climate of the Past Discussions 11, no. 4 (July 1, 2015): 2615–47. http://dx.doi.org/10.5194/cpd-11-2615-2015.
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Abstract. late Eocene pCO2 concentration is estimated based on the species of Nageia maomingensis Jin et Liu from the late Eocene of Maoming Basin, Guangdong Province. This is the first paleoatmospheric estimates for the late Eocene of South China using stomatal data. Studies of stomatal density (SD) and stomatal index (SI) with N. motleyi (Parl.) De Laub., the nearest living equivalent species of the fossil, indicate that the SD inversely responds to atmospheric CO2 concentration, while SI has almost no relationships with atmospheric CO2 concentration. Therefore, the pCO2 concentration is reconstructed based on the SD of the fossil leaves in comparison with N. motleyi. Results suggest that the mean CO2 concentration was 391.0 ± 41.1 ppmv or 386.5 ± 27.8 ppmv during the late Eocene, which is significantly higher than the CO2 concentrations documented from 1968 to 1955 but similar to the values for current atmosphere indicating that the Carbon Dioxide levels during that the late Eocene at that time may have been similar to today.
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Kapur, Vivesh V., and Sunil Bajpai. "Oldest South Asian tapiromorph (Perissodactyla, Mammalia) from the Cambay Shale Formation, western India, with comments on its phylogenetic position and biogeographic implications." Journal of Palaeosciences 64, no. (1-2) (December 31, 2015): 95–103. http://dx.doi.org/10.54991/jop.2015.104.
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A new tapiromorph perissodactyl (Cambaylophus vastanensis gen. et sp. nov.) from the basal Eocene (~54–55 Ma) Cambay Shale Formation, Vastan Lignite Mine, Gujarat, western India, is described for the first time. The new taxon, which represents the earliest known tapiromorph from South Asia and the second perissodactyl group in the Vastan mammal fauna after cambaytheres, is based on a partial maxilla with molars and deciduous premolars. Cambaylophus differs from Eocene tapiromorphs from the Indian Subcontinent mainly in having relatively narrow and less lophodont upper molars with a small, low and lingually shifted parastyle. Phylogenetic analysis suggests that Cambaylophus forms a clade with the early Eocene tapiromorph Gandheralophus from Pakistan, and that it is closely nested with the early Eocene (Bumbanian) tapiromorph Orientolophus from China. The study points out the importance of Cambaylophus in evaluating the evolutionary relationships of early radiation of tapiromorphs and ascertaining the degree of connectivity/isolation of the Indian Subcontinent around the Palaeocene–Eocene boundary, especially in the context of India–Asia collision.
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Zhu, Jiang, Christopher J. Poulsen, and Jessica E. Tierney. "Simulation of Eocene extreme warmth and high climate sensitivity through cloud feedbacks." Science Advances 5, no. 9 (September 2019): eaax1874. http://dx.doi.org/10.1126/sciadv.aax1874.
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The Early Eocene, a period of elevated atmospheric CO2 (>1000 ppmv), is considered an analog for future climate. Previous modeling attempts have been unable to reproduce major features of Eocene climate indicated by proxy data without substantial modification to the model physics. Here, we present simulations using a state-of-the-art climate model forced by proxy-estimated CO2 levels that capture the extreme surface warmth and reduced latitudinal temperature gradient of the Early Eocene and the warming of the Paleocene-Eocene Thermal Maximum. Our simulations exhibit increasing equilibrium climate sensitivity with warming and suggest an Eocene sensitivity of more than 6.6°C, much greater than the present-day value (4.2°C). This higher climate sensitivity is mainly attributable to the shortwave cloud feedback, which is linked primarily to cloud microphysical processes. Our findings highlight the role of small-scale cloud processes in determining large-scale climate changes and suggest a potential increase in climate sensitivity with future warming.
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England, T. D. J., L. D. Currie, N. W. D. Massey, M. K. Roden-Tice, and D. S. Miller. "Apatite fission-track dating of the Cowichan fold and thrust system, southern Vancouver Island, British Columbia." Canadian Journal of Earth Sciences 34, no. 5 (May 1, 1997): 635–45. http://dx.doi.org/10.1139/e17-050.
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The Cowichan fold and thrust system on southern Vancouver Island comprises a linked system of folds and thrust faults in crystalline and sedimentary rocks of the Wrangellia terrane and its sedimentary cover, the Upper Cretaceous Nanaimo Group, and Upper Paleocene to Lower Eocene sandstones of the Chuckanut Formation. Apatite fission-track analysis indicates that cooling below the closure temperature of fission-track retention in apatite (100 ± 20 °C) for both the Island Plutonic Suite from the Wrangellian basement and the Nanaimo Group occurred at ~ 50–40 Ma (Middle Eocene). Thrusting is interpreted to have occurred immediately prior to this time in the Middle Eocene, but after post-Cretaceous regional burial of the Turonian to Maastrichtian Nanaimo Group and deposition of Upper Paleocene and Lower Eocene sandstones, which are involved in the deformation. These timing constraints support the hypothesized temporal linkage between contraction and uplift of Wrangellia during the Middle Eocene and continued margin-normal contraction of the Pacific Rim terrane (± the Crescent terrane) at ~ 45 Ma.
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Lindow, Bent E. K., and Gareth J. Dyke. "A small galliform bird from the Lower Eocene Fur Formation, north-western Denmark." Bulletin of the Geological Society of Denmark 55 (March 12, 2007): 59–63. http://dx.doi.org/10.37570/bgsd-2007-55-04.
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A pair of fossilized imprints of feet represent the first published galliform (landfowl) specimenfrom the Lower Eocene Fur Formation of northwest Denmark. The specimen is referable to Galliformes due to the presence of a distinctly asymmetric trochlea metatarsi III. The specimen appears distinct from previously described Eocene Galliformes (e.g. Gallinuloididae, Quercymegapodiidae and Paraortygidae) and may represent a new taxon of Galliformes, increasing the diversity of this group in the Lower Eocene.
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Li, Yajun, Shu Jiang, Zhenglong Jiang, Hao Liu, and Bingxi Li. "Reconstruction of the Cenozoic History of Hydrocarbon Fluids from Rifting Stage to Passive Continental Margin Stage in the Huizhou Sag, the Pearl River Mouth Basin." Geofluids 2017 (2017): 1–32. http://dx.doi.org/10.1155/2017/4358985.
Full textAbstract:
The Eocene lacustrine sediments are the primary source rocks in the Huizhou Sag of the Pear River Mouth Basin. This study employs basin modeling for four representative wells and two profiles in the Huizhou Sag to reconstruct the process of generation, expulsion, migration, and accumulation of hydrocarbon fluids. The Eocene source rocks started to generate hydrocarbon at 33.9 Ma and are currently in a mid-mature and postmature stage. Hydrocarbons are mainly expelled from the Eocene Wenchang Fm, and the contribution of the Eocene Enping formation is minor. Under the driving forces of buoyancy and excess pressure, major hydrocarbons sourced from the Eocene source rocks firstly migrated laterally to the adjacent Eocene reservoirs during the postrift stage, then vertically via faults to Oligo-Miocene carrier beds, and finally laterally to the structural highs over a long distance during the Pliocene-Quaternary Neotectonic stage, which is controlled by both structural morphology and heterogeneity of carrier beds. Fault is the most important conduit for hydrocarbon fluid migration during the Neotectonic stage. Reactivation of previous faults and new-formed faults caused by the Dongsha Movement (9.8–4.4 Ma) served as vertical migration pathways after 10.0 Ma, which significantly influenced the timing of hydrocarbon accumulation in the postrift traps.
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Vera, Bárbara. "Patagonian Eocene Archaeopithecidae Ameghino, 1897 (Notoungulata): systematic revision, phylogeny and biostratigraphy." Journal of Paleontology 91, no. 6 (August 24, 2017): 1272–95. http://dx.doi.org/10.1017/jpa.2017.53.
Full textAbstract:
AbstractThe Archaeopithecidae is a very poorly known group of native ungulates from the Eocene of Patagonia (Argentina), whose alpha taxonomy has remained obscure since Ameghino’s times. It is traditionally considered as a family representative of the Casamayoran (middle Eocene) South American Land Mammal Age, and is thought to be morphologically close to the notopithecids. After studying >200 specimens from several institutions, including all the type specimens, a taxonomic overestimation is established. Out of the six species considered originally as archaeopithecids, Archaeopithecus rogeri Ameghino, 1897 is here recognized as the only valid name and species; subsequent synonymies are proposed and previous taxonomic hypotheses discarded. This exhaustive revision has permitted improving the knowledge of A. rogeri and, for the first time, it has revealed many craniodental characters, which allow amending its diagnosis and differentiating this taxon from other Eocene notoungulates. Archaeopithecus rogeri is a small-sized taxon characterized by its complete and rooted dentition, which is relatively higher than that of other contemporaneous short-crowned notoungulates and shows ontogenetic variation in size and morphology. The body mass range of A. rogeri (1.4–2.5 kg) is comparable to those of notopithecids and some small hegetotheriids. The phylogenetic analysis shows A. rogeri is not directly related to any family within Notoungulata, appearing into a polytomy, as a basal taxon of typotherians. The biochronological range of A. rogeri is adjusted to Vacan (middle Eocene) through Barrancan subages (late middle Eocene); older (Riochican, late early Eocene) and younger (Mustersan, late Eocene) records remain to be confirmed.
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Peng, Guangrong, Weitao Chen, Peimeng Jia, Ming Luo, Ye He, Yaoyao Jin, Chuan Xu, and Xuanlong Shan. "Middle-Late Eocene Climate in the Pearl River Mouth Basin: Evidence from a Palynological and Geological Element Record in the Xijiang Main Subsag." Minerals 13, no. 3 (March 8, 2023): 374. http://dx.doi.org/10.3390/min13030374.
Full textAbstract:
The temperature changes in the middle-late Eocene had a profound impact on various ecosystems around the world. This has been confirmed not only in marine sediments but also in lake ecosystems, which have provided more detailed isochronous continental sedimentary records. Based on systematic palynological and element analyses of fine-grained lacustrine sediments from the Xijiang main subsag in the Pearl River Mouth Basin, southern China, we reconstructed the climate evolution of the middle-late Eocene. A total of 73 genera and 115 species of sporopollen fossils were identified from the middle-late Eocene in the study area. Three pollen zones comprising Quercoidites–Polypodiaceaesporites–Pinuspollenites, Pinuspollenites–Ulmipollenites–Cedripites, and Pinuspollenites–Abietineaepollenites–Juglanspollenites were established from bottom to top. The analysis of the vegetation types, climatic zones, and dry–humid types of the sporopollen showed that, in the study area, the Eocene was dominated by a subtropical–warm temperate climate: the early-late Eocene was dominated by a temperate climate, and the late Eocene was characterized by the prevalence of a warm temperate climate, which was consistent with the palaeoclimate reconstruction results for element geochemical indices (Fe/Mn, Sr/Cu, CIA, PIA, etc.). In addition, the comparative study showed that the middle-late Eocene in the study area was characterized by a warm and humid climate, which transitioned to a warm and cool semihumid–semiarid climate and then a warm and cool semihumid climate. These findings demonstrated a good coupling relationship with the trend for the changes in the global palaeotemperature and can be used as an isochronous continental sedimentary response.