Detrital zircon U-Pb ages of Paleogene deposits in the southwestern Sichuan foreland basin, China: Constraints on basin-mountain evolution along the southeastern margin of the Tibetan Plateau

2019 ◽  
Vol 132 (3-4) ◽  
pp. 668-686 ◽  
Author(s):  
Hanyu Huang ◽  
Dengfa He ◽  
Di Li ◽  
Yingqiang Li

Abstract The tectonic setting of the southwestern Sichuan foreland basin, China, changed rapidly during the Paleogene period, and records from this period may provide crucial information about the formation and tectonic processes that affected the Sichuan Basin. To constrain the provenance and to reconstruct the paleogeography of the Paleogene successions, we conducted a detailed analysis of the petrology, geochronology, and sedimentary facies of rocks from the southwestern Sichuan foreland basin. The detrital components of the three analyzed sandstone samples indicate moderately to highly mature sediment that was primarily derived from a recycled orogen provenance. Five major age populations were identified in the U-Pb age spectra: Neoarchean to Siderian (2524–2469 Ma and 2019–1703 Ma), Neoproterozoic (Tonian to Cryogenian, 946–653 Ma), Ordovician to Carboniferous (Katian to lower Pennsylvanian, 448–321 Ma), and Carboniferous to Triassic (306–201 Ma). Each of these age populations corresponds to one or several potential sources around the southwestern Sichuan foreland basin. A multidimensional scaling analysis indicated that the Paleogene zircons were mainly derived from recycled sediments of the Songpan-Ganzi terrane and the Sichuan Basin, with minor input from the Yidun terrane, Kangdian terrane, Qinling orogenic belt, and Jiangnan-Xuefeng orogenic belt. More specifically, the sediment supply from the Songpan-Ganzi terrane to the foreland basin decreased significantly from the Mingshan stage to the Lushan stage, and the Sichuan Basin simultaneously became the most important source area. In addition, there is a high correlation between the detrital zircon U-Pb age spectrum of the southwestern Sichuan Basin and that of the Xichang Basin, which may suggest that a wider and unified Paleo-Yangtze Basin existed during the Late Cretaceous-early Paleogene.




2021 ◽  
Author(s):  
Anas Abbassi ◽  
Paola Cipollari ◽  
Maria Giuditta Fellin ◽  
Mohamed Najib Zaghloul ◽  
Marcel Guillong ◽  
...  

<p>During the Tertiary evolution of the Western Mediterranean subduction system, the orogenic accretion at the Maghrebian margin let the stacking of three main tectonic zones of the Rif fold-and-thrust belt: 1) the Internal Zone; 2) the “Maghrebian Flysch” Nappes; and 3) the  External Zone. In this context, a migrating foreland basin system developed between the Maghrebian orogenic belt and the adjacent African Craton. </p><p>A comprehensive reconstruction of the foreland basin system of the Rif Chain for each phase of its accretional history is still missing. In this work, by integrating field observations with quantitative biostratigraphic data from calcareous nannofossils assemblages, sandstone composition, and detrital zircon U-Pb geochronology from selected stratigraphic successions, we reconstruct the foreland basin system that in the early Miocene developed in front of the growing Rif orogen. The analyzed successions are representative of (1) the “Beliounis Facies”, made of quartz-arenites and litharenites (Numidian-like “mixed succession”), from the Predorsalian Unit; (2) the “Mérinides Facies”, made of a Numidian-like “mixed succession”, from the “Maghrebian Flysch Basin”; and (3) the classical “Numidian Facies”, exclusively made of quartzarenites, from the Intrarifian Tanger Unit.</p><p>The petrographic analyses and the detrital zircon U-Pb ages show the provenance of the quartzarenites of the “Numidian Facies” from the African Craton, whereas the sublitharenites and feldspathic litharenites, of both the “Mérinides Facies” and “Beliounis Facies”, show provenance from a cratonic area and the growing and unroofing Rif Chain, respectively. </p><p>The Alpine signature of the detrital grains sedimented into the foredeep deposits of the early Miocene orogenic system of the Rif Chain is from the feldspathic litharenites of both the Mérinides Facies and the Beni Ider Flysch. Both show Mesozoic and Cenozoic U-Pb zircon populations, with a large population of zircons centered at ca. 32 Ma. The U and Th concentration, the Th/U ratio, and the REE pattern of this population of zircons suggest a possible source area from Oligocene doleritic rock intrusions, similar to the magmatic dyke swarms (diorite) cropping out in the Malaga region ( SE Spain).</p><p>The biostratigraphic analyses pinpoint the same age for the arrival of the quartz grains in the Numidian, Mérinides, and Beliounis deposits, indicating about 1 Myr for their sedimentation (ca. 20-19 Ma, early Burdigalian). Together with field evidence, the biostratigraphic results point to an autochthonous deposition of the Numidian Sandstones on top of the Tanger Unit, allowing to delineate the early Burdigalian foreland basin system of the Rif Chain. The foreland depozone involved the Tanger Unit and received the “Numidian Facies” deposits ; the foredeep depozone hosted about 2000 m of the “Mérinides Facies” and the Beni Ider Flysch, and developed on the so-called “Flysch Basin Domain”; and, finally, the wedge-top depozone, characterized by the “Beliounis Facies”, developed on top of the Predorsalian Unit.</p><p>The Numidian Sandstones and the Numidian-like deposits analyzed in Morocco show the same age of similar deposits from Algeria, Tunisia, and Sicily, suggesting a comparable early Burdigalian tectono-sedimentary evolution along the southern branch of the Western Mediterranean subduction-related orogen.</p>



2021 ◽  
Author(s):  
Renas I. Koshnaw ◽  
Fritz Schlunegger ◽  
Daniel F. Stockli

Abstract. Recognition of new angular unconformity and synthesizing of new detrital zircon U-Pb and (U-Th)/He provenance records, including zircon (U-Th)/(He-Pb) double dating, from the NW Zagros elucidate the basin dynamics of the foreland wedge-top and intermontane units, as well as the tectonic processes in the source terranes in response to different geodynamic phases. In this contribution, we present field observations and detrital zircon provenance data from hinterland basins to reconstruct the basin dynamics and the underlying tectonic controls in the NW Zagros in the Kurdistan region of Iraq. Results reveal that the deposition of the suture zone units of the Red Beds Series (RBS; Suwais Group, Govanda Formation, Merga Group) occurred in an intermontane basin on top of folded Upper Cretaceous units with an angular unconformity. The RBS provenance data point at the Paleogene Walash-Naopurdan-Kamyaran (WNK) arc-related complex as a source area and show substantial decrease of magmatism by ~ 36 Ma, as reflected by the youngest ages peaks. New detrital zircon provenance data from the hinterland wedge-top units of the proto-Zagros foreland basin (the Tanjero, Kolosh, and Gercus Formations) exhibit exclusive derivation from the Upper Cretaceous Neotethys ophiolitic terranes, different from the provenance of the older Lower Cretaceous and Paleozoic units that are dominated by the Paleozoic and Neoproterozoic age spectra. These shifts in provenance between different tectonostratigraphic units argue for sediment route reversal from E to W in response to ophiolite obduction, arrival of the WNK complex and commencement of the continental collision during the late Eocene, followed by deposition of the RBS in the hinterland of the proto-Zagros fold-thrust belt, and paleodrainage connection with the post-collisional Neogene foreland basin.





2020 ◽  
Author(s):  
Shuyu Zhao ◽  
Tian Feng ◽  
Xuexi Tie ◽  
Zebin Wang

Abstract. Impacts of global climate change on the occurrence and development of air pollution have attracted more attentions. This study investigates impacts of the warming Tibetan Plateau on air quality in the Sichuan Basin. Meteorological observations and ERA-interim reanalysis data reveal that the Tibetan Plateau has been rapidly warming during the last 40 years (1979–2017), particularly in winter when the warming rate is approximately twice as much as the annual warming rate. Since 2013, the winter temperature over the plateau has even risen by 2 °C. Here, we use the WRF-CHEM model to assess the impact of the 2 °C warming on air quality in the Sichuan Basin. The model results show that the 2 °C warming causes an increase in the Planetary Boundary Layer (PBL) height and a decrease in the relative humidity (RH) in the basin. The elevated PBL height strengthens vertical diffusion of PM2.5, while the decreased RH significantly reduces secondary aerosol formation. Overall, PM2.5 concentration is reduced by 17.5 % (~ 25.1 μg m−3), of which the reduction in primary and secondary aerosols is 5.4 μg m−3 and 19.7 μg m−3, respectively. These results reveal that the recent warming plateau has improved air quality in the basin, to some certain extent, mitigating the air pollution therein. Nevertheless, climate system is particularly complicated, and more studies are needed to demonstrate the impact of climate change on air quality in the downstream regions as the plateau is likely to continue warming.



2017 ◽  
Vol 29 (2) ◽  
pp. 307-325 ◽  
Author(s):  
Shugen Liu ◽  
Bin Deng ◽  
Luba Jansa ◽  
Zhiwu Li ◽  
Wei Sun ◽  
...  




2010 ◽  
Vol 495 (3-4) ◽  
pp. 337-347 ◽  
Author(s):  
Yajun Xu ◽  
Yuansheng Du ◽  
Peter A. Cawood ◽  
Jianghai Yang


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