THE HISTORY OF TETHYS IN THE LATE PALEOZOIC-EARLY MESOZOIC AND THE RECONSTRUCTION OF PANGEA

1989 ◽  
Vol 31 (7) ◽  
pp. 649-661 ◽  
Author(s):  
V. G. Kaz'min ◽  
I. M. Sborshchikov
Keyword(s):  
Late Paleozoic ◽  
Early Mesozoic ◽  
History Of

Late Paleozoic- Early Mesozoic tectonics of Hainan Island: Key to understanding Paleotethyan geology

2020 ◽  
Author(s):  
Huiying He ◽  
Peter Cawood ◽  
Yuejun Wang
Keyword(s):  
South China ◽  
Tectonic Evolution ◽  
Hainan Island ◽  
Igneous Rocks ◽  
Late Paleozoic ◽  
Calc Alkaline ◽  
Early Mesozoic ◽  
History Of ◽  
Back Arc ◽  
T Values

<p>In Southeast Asia, establishing the origin and associated tectonic setting of Late Paleozoic-Early Mesozoic igneous rocks is complicated by structural overprinting and the complex tectonic evolution of the Paleotethyan regime. Hainan Island, located at the south-eastern margin of the Paleotethys, and lacking significant tectonic overprints is a key to understand amalgamation history of the Indochina and South China blocks and to constraining the tectonic evolution of Paleotethys ocean in southeast Asia.</p><p>The Late Paleozoic-Early Mesozoic record of igneous rocks on Hainan Island includes the following. 1) ca. 350 Ma island arc andesites and ca. 330 Ma metabasites, the latter with both MORB- and arc-like geochemical affinities, positive ε<sub>Nd</sub>(t) values of +5.86 – +9.85 and rare inherited zircons with a zircon age of 1400 Ma inferred to be derived from a MORB source with the input of a slab-derived component. Together with the ~350 Ma island arc andesites, the Carboniferous tectonic environment is supposed to be a continental back-arc basin setting. 2) Late Permian gneiss granitoids (272-252 Ma) characterized by a gneissic foliation and calc-alkaline I-type geochemical affinities with negative Nb-Ta and Ti anomalies, related to metasomatized mantle wedge modified by the sediment-derived component in a continental arc setting. 3) ca. 257 Ma arc-like andesites, which further validate a subduction-related setting. 4) Peraluminious Early-Middle Triassic massive granitoids (251–243 Ma) with slightly high A/CNK ratios, δ<sup>18</sup>O values (up to 11.75 ‰) and Sr/Y ratios, inferred to have formed in a compressive regime from a mixed source of greywacke and metabasite. 5) Middle-Late Triassic (242–225 Ma) high-K calc-alkaline granitoids with high zircon temperatures (842–867°C) and geochemical signatures of A-type granites. They show slightly low whole-rock ε<sub>Nd</sub>(t) and zircon ε<sub>Hf</sub>(t) values, suggestive of the derivation from a metabasite–greywacke source in an extensional setting. 6) ca. 240 Ma gabbro-dolerites showing enrichment in LILEs, depletion in HFSEs, negative ε<sub>Nd</sub> (t)-ε<sub>Hf</sub> (t) values (−8.45 to −1.05 and −5.9 to −2.7, respectively) and crustal-like δ<sup>18</sup>O values (7.26–8.70‰), it is implied that the Hainan Island entered into post-collisional environment in response to the asthenosphere upwelling shortly after the closure of back-arc basin.</p><p>Thus, Hainan Island provides a record of Carboniferous back-arc basin opening, followed by an extended Permian–Triassic history of subduction-related consumption leading to orogenic assembly and extensional collapse between the South China and Indochina blocks. Such a tempo-spatial pattern is consistent with that along the Song Ma–Ailaoshan suture zone rather than the magmatic history of eastern South China and indicates that the Paleotethys extended west to at least Hainan Island in the Late Paleozoic-Early Mesozoic.</p>

scholarly journals Investigating the Paleozoic–Mesozoic low-temperature thermal history of the southwestern Canadian Arctic: insights from (U–Th)/He thermochronology

2017 ◽  
Vol 54 (4) ◽  
pp. 430-444 ◽  
Author(s):  
D. Midwinter ◽  
J. Powell ◽  
D.A. Schneider ◽  
K. Dewing
Keyword(s):  
Low Temperature ◽  
Vitrinite Reflectance ◽  
Canadian Arctic ◽  
The Arctic ◽  
Late Paleozoic ◽  
Marked Contrast ◽  
Early Mesozoic ◽  
Arctic Alaska ◽  
Thermal Maximum ◽  
History Of

The Arctic Amerasia Basin, located between the Canadian margin and Alaska, formed by purported Jurassic–Cretaceous rifting related to the rotation of the Arctic Alaska – Chukotka microcontinent from northern Laurentia. Rifting may have been accompanied by rift shoulder uplift and cooling that is recorded in low-temperature thermochronometers. Furthermore, the southwestern Canadian Arctic has a widespread Devonian–Cretaceous unconformity with a poorly understood burial-unroofing history. We evaluate new zircon (U–Th)/He thermochronology (ZHe) and organic maturity (vitrinite reflectance (VRo)) data from Neoproterozoic strata of the Amundsen Basin, Cambrian strata of the Arctic Platform, and Devonian strata of the Franklinian Basin to help resolve the sedimentary thickness deposited and eroded during the time represented by the regional unconformity. ZHe and VRo models identify the thermal maximum occurring between the late Paleozoic – Mesozoic interval. Proximal to the rifted Canadian margin, models estimate 3.7–4.5 km of deposition between the Devonian–Cretaceous, in marked contrast to <1 km towards the craton. Jurassic–Cretaceous exhumation is estimated at 2.3–3.5 km and is more uniform across the region. Although the magnitude of burial and erosion can be resolved by modelling, the timing of these events cannot be elucidated with confidence. The thermochronology models can be satisfied by either (1) late Paleozoic – early Mesozoic burial with a thermal maximum prior to Jurassic rifting, followed by cooling; or (2) Late Devonian maximum burial, with gradual unroofing until Cretaceous sedimentation. Although continued deposition into the Mesozoic towards the craton interior seems unlikely, it remains possible that there was continued deposition proximal to the rifted Canadian margin.

scholarly journals Crinoids from Svalbard in the aftermath of the end−Permian mass extinction

2015 ◽  
Vol 36 (3) ◽  
pp. 225-238 ◽  
Author(s):  
Mariusz A. Salamon ◽  
Przemysław Gorzelak ◽  
Nils−Martin Hanken ◽  
Henrik Erevik Riise ◽  
Bruno Ferré
Keyword(s):  
Mass Extinction ◽  
Lower Triassic ◽  
Late Paleozoic ◽  
Early Triassic ◽  
Major Event ◽  
Early Mesozoic ◽  
History Of ◽  
Permian Extinction ◽  
Stratigraphic Ranges ◽  
Permian Mass Extinction

AbstractThe end-Permian mass extinction constituted a major event in the history of crinoids. It led to the demise of the major Paleozoic crinoid groups including cladids, disparids, flexibles and camerates. It is widely accepted that a single lineage, derived from a late Paleozoic cladid ancestor (Ampelocrinidae), survived this mass extinction. Holocrinid crinoids (Holocrinus, Holocrinida) along with recently described genus Baudicrinus (Encrinida), the only crinoid groups known from the Early Triassic, are considered the stem groups for the post-Paleozoic monophyletic subclass Articulata. Here, we report preliminary data on unexpectedly diverse crinoid faunas comprising at least four orders from the Lower Triassic (Induan and Olenekian) of Svalbard, extending their stratigraphic ranges deeper into the early Mesozoic. These findings strongly imply that the recovery of crinoids in the aftermath of the end-Permian extinction began much earlier at higher palaeolatitudes than in the central Tethys.

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