scholarly journals The History of Transgressions during the Late Paleocene-Early Eocene in the Kuqa Depression, Tarim Basin: Constraints from C-O-S-Sr Isotopic Geochemistry

Minerals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 834
Author(s):  
Yang Xu ◽  
Yangtong Cao ◽  
Chenglin Liu ◽  
Hua Zhang ◽  
Xiao Nie
Keyword(s):  
Late Eocene ◽  
Early Eocene ◽  
Carbon And Oxygen Isotopes ◽  
Lower Eocene ◽  
Kuqa Depression ◽  
Tethys Sea ◽  
Late Paleocene ◽  
History Of ◽  
Research Objects ◽  
Upper Paleocene

The Tethys Sea extended into the Kuqa Depression from the Paleocene to the late Eocene and provided an abundant provenance for the deposition of evaporite sequences. Until now, detailed research on the history of transgressions during the late Paleocene-early Eocene in the Kuqa Depression has been limited. Therefore, in this study, we took the upper Paleocene Talak section and the lower Eocene Xiaokuzibai section in the western part of the Depression as the research objects and analyzed the petrology, the carbon and oxygen isotopes of carbonate rocks, and the sulfur and strontium isotopes of gypsum rocks to systematically study the above issues. The δ13C, δ18O and δ34S values of the upper Paleocene evaporite sequences were determined to be between 4.2‰ and 5.7‰, between −5.2‰ and 2.4‰, and between 16.5‰ and 17.9‰, respectively. The δ13C, δ18O, δ34S, and 87Sr/86Sr values of the lower Eocene evaporite sequences were determined to be between −6.9‰ and −2.0‰, between −9.0‰ and −4.5‰, between 10.5‰ and 17.0‰, and between 0.708642 and 0.709883, respectively. The analysis results show that the evaporite sequence of the upper Paleocene was formed by transgression. The deposition of the evaporite sequence changed from continental to marine deposition, and then gradually transitioned to continental during the Early Eocene. This paper is of great significance for reconstructing the history of transgressions in the Tethys tectonic realm during this period.

scholarly journals Late Paleocene event chronology; unconformities, not diachrony

2000 ◽  
Vol 171 (3) ◽  
pp. 367-378 ◽  
Author(s):  
Marie-Pierre Aubry ◽  
Benjamin S. Cramer ◽  
Kenneth G. Miller ◽  
James D. Wright ◽  
Dennis V. Kent ◽  
...  
Keyword(s):  
Planktonic Foraminifera ◽  
Calcareous Nannoplankton ◽  
Lower Eocene ◽  
Late Paleocene ◽  
Relative Chronology ◽  
Carbon Isotope Excursion ◽  
Thermal Maximum ◽  
Unequivocal Identification ◽  
Upper Paleocene ◽  
Reference Section

Abstract The chronology of the events associated with the late Paleocene thermal maximum (LPTM, Chron C24r) has been established through the construction of a composite reference section that involved chemomagnetobiostratigraphic correlations and assumed minimum diachrony of biostratigraphic events. On this basis, discrepancies between correlations in different sections were explained by inferred unconformities. However, diachrony between distant sections cannot be ruled out. We report here on two geographically close sections drilled onshore New Jersey that yield different records of chemomagnetobiostratigraphic correlations in the interval representing Chron C24r. Because of their proximity ( approximately 40 km apart), diachrony of biostratigraphic events between the two sections can be ruled out. In contrast, the marked lithologic disconformities in the sections explain well the different records of events. We thus conclude that the current relative chronology for Chron C24r is firmly based and that the upper Paleocene-lower Eocene stratigraphic record yields multiple unconformities, with Subzone NP9b rarely sampled. We examine the implications that undeciphered unconformities may have on the identification of proxies for paleoceanographic reconstruction, in particular with regard to the identification of the carbon isotope excursion (CIE) that reflects a dramatic latest Paleocene disturbance of the carbon cycle. We propose biostratigraphic means (short-lived calcareous nannoplankton and planktonic foraminifera taxa) that permit the unequivocal identification of the CIE not only in the oceanic realm but also in neritic settings.

A new glyptosaurine lizard from the earliest Eocene of Dormaal, Belgium

2012 ◽  
Vol 183 (6) ◽  
pp. 627-633 ◽  
Author(s):  
Robert M. Sullivan ◽  
Marc Augé ◽  
Eric Wille ◽  
Richard Smith
Keyword(s):  
North America ◽  
Western Europe ◽  
Reference Level ◽  
New Taxon ◽  
Early Eocene ◽  
Lower Eocene ◽  
Lower Tooth ◽  
Late Paleocene ◽  
Sudden Appearance ◽  
Tooth Count

Abstract A new glyptosaurine lizard ?Placosaurus ragei, n. sp., is recognized as being distinct from Paraplacosauriops quercyi in having a lightly built dentary, incipient heterodont teeth, lower tooth count (19), and teeth that are more gracile compared to other European glyptosaurine lizards. ?Placosaurus ragei also differs from “Placosaurus” europaeus, which has a prominent homodont dentition and is more massive. A second specimen, an isolated, nearly complete parietal, partly covered with hexagonal and polygonal osteoderms, is referable to the European glyptosaurin Placosaurus and is provisionally referred to the species ?Placosaurus ragei. A third specimen, an incomplete right frontal fragment of an indeterminate “melanosaurin,” may represent a new taxon, or may be referable to the well-known Western European taxon Placosauriops. Taxa pertaining to both tribes (Glyptosaurini and “Melanosaurini”) of glyptosaurine lizards have been recovered from the lower Eocene deposits of Dormaal, Belgium. Their apparent sudden appearance is interpreted as marking entry into western Europe. The Dormaal locality has been correlated to reference level MP7 and thus is considered to be of early Eocene age. Glyptosaurine lizards probably dispersed into western Europe, from North America, through the Greenland bridge during late Paleocene/early Eocene time.

scholarly journals North Atlantic marine biogenic silica accumulation through the early to middle Paleogene: implications for ocean circulation and silicate weathering feedback

2021 ◽  
Vol 17 (5) ◽  
pp. 1937-1954
Author(s):  
Jakub Witkowski ◽  
Karolina Bryłka ◽  
Steven M. Bohaty ◽  
Elżbieta Mydłowska ◽  
Donald E. Penman ◽  
...  
Keyword(s):  
North Atlantic ◽  
Biogenic Silica ◽  
Middle Eocene ◽  
Nutrient Supply ◽  
Late Eocene ◽  
Silicate Weathering ◽  
Early Eocene ◽  
The North ◽  
History Of ◽  
The North Atlantic

Abstract. The Paleogene history of biogenic opal accumulation in the North Atlantic provides insight into both the evolution of deepwater circulation in the Atlantic basin and weathering responses to major climate shifts. However, existing records are compromised by low temporal resolution and/or stratigraphic discontinuities. In order to address this problem, we present a multi-site, high-resolution record of biogenic silica (bioSiO2) accumulation from Blake Nose (ODP Leg 171B, western North Atlantic) spanning the early Paleocene to late Eocene time interval (∼65–34 Ma). This record represents the longest single-locality history of marine bioSiO2 burial compiled to date and offers a unique perspective into changes in bioSiO2 fluxes through the early to middle Paleogene extreme greenhouse interval and the subsequent period of long-term cooling. Blake Nose bioSiO2 fluxes display prominent fluctuations that we attribute to variations in sub-thermocline nutrient supply via cyclonic eddies associated with the Gulf Stream. Following elevated and pulsed bioSiO2 accumulation through the Paleocene to early Eocene greenhouse interval, a prolonged interval of markedly elevated bioSiO2 flux in the middle Eocene between ∼46 and 42 Ma is proposed to reflect nutrient enrichment at Blake Nose due to invigorated overturning circulation following an early onset of Northern Component Water export from the Norwegian–Greenland Sea at ∼49 Ma. Reduced bioSiO2 flux in the North Atlantic, in combination with increased bioSiO2 flux documented in existing records from the equatorial Pacific between ∼42 and 38 Ma, is interpreted to indicate diminished nutrient supply and reduced biosiliceous productivity at Blake Nose in response to weakening of the overturning circulation. Subsequently, in the late Eocene, a deepwater circulation regime favoring limited bioSiO2 burial in the Atlantic and enhanced bioSiO2 burial in the Pacific was established after ∼38 Ma, likely in conjunction with re-invigoration of deepwater export from the North Atlantic. We also observe that Blake Nose bioSiO2 fluxes through the middle Eocene cooling interval (∼48 to 34 Ma) are similar to or higher than background fluxes throughout the late Paleocene–early Eocene interval (∼65 to 48 Ma) of intense greenhouse warmth. This observation is consistent with a temporally variable rather than constant silicate weathering feedback strength model for the Paleogene, which would instead predict that marine bioSiO2 burial should peak during periods of extreme warming.

scholarly journals Short note on the first record of fossil shark teeth in the Chehel-Kaman formation, Iran

2020 ◽  
Vol 81 (1) ◽  
pp. 31-39
Author(s):  
Nicolae Trif ◽  
Farrokh Ghaemi ◽  
Jafar Taheri ◽  
Morteza Taherpour-Khalil-Abad
Keyword(s):  
Short Note ◽  
First Record ◽  
Early Eocene ◽  
Tethys Sea ◽  
Shark Teeth ◽  
Late Paleocene ◽  
Fossil Fish ◽  
Marine Vertebrates ◽  
Ne Iran

Shark teeth discovered in the late Paleocene-early Eocene Chehel-Kaman Formation in NE Iran bring new data on the fossil fish record from this country. Two genera from the location are described and figured. The present record is one of the very few reports of fossil shark teeth from the Cenozoic of Iran and the first one from this formation and region. The marine vertebrates known from this region of the Tethys Sea are very scarce.

scholarly journals Burial and exhumation history of the Jameson Land Basin, East Greenland, estimated from thermochronological data from the Blokelv-1 core

2018 ◽  
pp. 133-147
Author(s):  
Paul F. Green ◽  
Peter Japsen
Keyword(s):  
Middle Eocene ◽  
Vitrinite Reflectance ◽  
Upper Jurassic ◽  
Late Eocene ◽  
Early Eocene ◽  
Ocean Drilling Program ◽  
East Greenland ◽  
Ocean Drilling ◽  
History Of ◽  
Intrusive Activity

Apatite fission-track analysis (AFTA) data in two Upper Jurassic core samples from the 231 m deep Blokelv-1 borehole, Jameson Land, East Greenland, combined with vitrinite reflectance data and regional AFTA data, define three palaeo-thermal episodes. We interpret localised early Eocene (55– 50 Ma) palaeotemperatures as representing localised early Eocene heating related to intrusive activity whereas we interpret late Eocene (40–35 Ma) and late Miocene (c. 10 Ma) palaeotemperatures as representing deeper burial followed by successive episodes of exhumation. For a palaeogeothermal gradient of 30°C/km and likely palaeo-surface temperatures, the late Eocene palaeotemperatures require that the Upper Jurassic marine section in the borehole was buried below a 2750 m thick cover of Upper Jurassic – Eocene rocks prior to the onset of late Eocene exhumation. As these sediments are now near outcrop at c. 200 m above sea level, they have been uplifted by at least 3 km since maximum burial during post-rift thermal subsidence. The results are consistent with estimates of rock uplift on Milne Land since the late Eocene and with interpretation of Ocean Drilling Program (ODP) data off South-East Greenland suggesting that mid-Cenozoic uplift of the margin triggered the marked influx of coarse clastic turbidites during the late Oligocene above a middle Eocene to upper Oligocene hiatus.

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