Petrography and geochemistry of the Middle Jurassic Fort Member Sandstone, Jaisalmer Formation, Western India: Implications for weathering, provenance, and tectonic setting

2022 ◽  
Author(s):  
Faiz Ahmad ◽  
Mohd Amir ◽  
Mohammad Quasim ◽  
Nurul Absar ◽  
Abul Hasnat Ahmad
Keyword(s):  
Middle Jurassic ◽  
Tectonic Setting ◽  
Western India

scholarly journals Magnetostratigraphy of the Middle Jurassic Sediments from Kachchh Basin, Western India

2016 ◽  
Vol 07 (03) ◽  
pp. 301-310 ◽  
Author(s):  
Venkateshwarlu Mamilla ◽  
Bindhyachal Pandey ◽  
Deo Brat Pathak ◽  
Papanna Guguloth ◽  
Jai Krishna
Keyword(s):  
Middle Jurassic ◽  
Western India ◽  
Kachchh Basin

Responses of benthic foraminifera to environmental variability: A case from the Middle Jurassic of the Kachchh Basin (Western India)

2019 ◽  
Vol 151 ◽  
pp. 101749 ◽  
Author(s):  
Sreepat Jain ◽  
Ahmed Awad Abdelhady ◽  
Mohamad Alhussein
Keyword(s):  
Benthic Foraminifera ◽  
Middle Jurassic ◽  
Environmental Variability ◽  
Western India ◽  
Kachchh Basin

Late Mesozoic Paleo-Pacific Plate “scissors-like” subduction: Insight from the magmatism in the Gan-Hang Belt, Southeast China

2020 ◽  
Author(s):  
Liu Boran ◽  
Zhao Xilin ◽  
Yu Shengyao ◽  
Jiang Yang ◽  
Mao Jianren ◽  
...  
Keyword(s):  
Continental Margin ◽  
Middle Jurassic ◽  
Tectonic Setting ◽  
Pacific Plate ◽  
Geochemical Data ◽  
Asian Continent ◽  
Southeast China ◽  
Late Mesozoic ◽  
Extensional Tectonic ◽  
Roll Back

Though it is widely accepted that the Paleo-Pacific Plate has a subducted beneath the eastern Asian continent, controversy still exists regarding the initial timing and geodynamic model of the subduction. In this contribution, we report new geochronology and geochemical data of granitic plutons within the Gan-Hang Belt in Southeast China. The Damaoshan pluton yields zircon U-Pb ages of 139.60 ± 0.69 Ma and 133.90 ± 1.70 Ma, and the Qianshan and Fenglonggu plutons are dated at 135.70 ± 1.30 Ma and 135.33 ± 0.93 Ma, respectively. The Hecun and Huangtuling plutons yield ages of 157.85 ± 0.77 Ma and 167.10 ± 7.50 Ma, respectively. The Damaoshan pluton has an obvious A-type geochemical signature in terms of major and trace element compositions, such as high K2O+Na2O contents (average 8.46 wt%) and FeOT/MgO ratios (average 10.29). The low CaO/Na2O ratios but high Al2O3/TiO2 (average is 110.05), Rb/Ba (average is 9.14), and Rb/Sr (average is 22.53) ratios indicate a derivation from pelite-derived melt. Meanwhile, we also studied the Mesozoic adakites related to magmatic ore formed during a compressive tectonic setting as well as the later bimodal dikes and A-type granitic plutons formed during the extensional tectonic setting in the Gan-Hang Belt. The multiphase qualitative plutons with geochemical characteristics of the adakitic and island arc types (175−150 Ma) related to the northwestward subduction of the Paleo-Pacific Plate, several bimodal dikes, and A-type granitic plutons (135−123 Ma) related to the subducted slab roll-back are found within the Gan-Hang Belt. All of these plutons show a decreasing trend of isotopic ages from the inland area to the coast, from SW to NE. We propose that the distribution pattern of these plutons in Southeast China was controlled by a scissors-like subduction and slab roll-back of the Paleo-Pacific Plate, which occurred roughly from SW to NE along the continental margin approximately during the Middle Jurassic to the Early Cretaceous.

On the Bathonian (Middle Jurassic) ammonites Micromphalites Buckman and Gracilisphinctes Buckman from Kachchh, Western India

1984 ◽  
Vol 121 (4) ◽  
pp. 319-321 ◽  
Author(s):  
A. K. Jaitly ◽  
C. S. P. Singh
Keyword(s):  
Middle Jurassic ◽  
Western India

AbstractSystematic descriptions of specimens collected from Pachchham ‘Island’, Kachchh, Western India, belonging to the genera Micromphalites Buckman and Gracilisphinctes Buckman are given. Their affinities with the different forms belonging to the above genera are discussed and described as Micromphalites aff. hourcqui Collignon and Gracilisphinctes cf. arkelli Collignon respectively. The distribution of these two genera in other regions is also briefly discussed.

Variability in Epistreptophyllum from the middle Jurassic of Kachchh, western India: An open question for the taxonomy of Mesozoic scleractinian corals

1997 ◽  
Vol 71 (4) ◽  
pp. 564-577 ◽  
Author(s):  
D. K. Pandey ◽  
B. Lathuiliere
Keyword(s):  
Middle Jurassic ◽  
Multivariate Analyses ◽  
Great Majority ◽  
Morphological Characters ◽  
Scleractinian Corals ◽  
Western India ◽  
Wide Range ◽  
Surface Ornamentation ◽  
Open Question ◽  
Range Of Variation

Epistreptophyllum cornutiformis Gregory, 1900, is the name assigned to a Middle Jurassic population of scleractinian corals from Kachchh, western India. Measurements of ten variables from 84 specimens of this population have been statistically examined by means of univariate and multivariate analyses. A wide range of variation in corallum shape, septal perforation, lateral septal surface ornamentation, nature of the endotheca, and that of the columella is observed. The great majority of specimens are solitary. The wide range of gradational variation observed in this population corresponds to and includes the morphological characters described for various scleractinian genera such as Protethmos Gregory, Metethmos Gregory, Frechia Gregory, and Epistreptophyllum Milaschewitsch. The assignment of these genera to this later senior synonym genus is supported by the description of a well-preserved topotype from Nattheim. The ornamentation of the septa in Epistreptophyllum is detailed and distances it from typical pennular corals.

Magnetic fabric and tectonic setting of the Early to Middle Jurassic felsic dykes at Pitt Point and Mount Reece, eastern Graham Land, Antarctica

2011 ◽  
Vol 24 (1) ◽  
pp. 45-58 ◽  
Author(s):  
Jiří Žák ◽  
Igor Soejono ◽  
Vojtěch Janoušek ◽  
Zdeněk Venera
Keyword(s):  
Stress Field ◽  
Middle Jurassic ◽  
Large Scale ◽  
Tectonic Setting ◽  
Local Stress ◽  
Weddell Sea ◽  
Magnetic Fabric ◽  
Magma Source ◽  
Magma Flow ◽  
North Eastern

AbstractAt Pitt Point, the east coast of Graham Land (Antarctic Peninsula), the Early to Middle Jurassic (Toarcian–Aalenian) rhyolite dykes form two coevally emplaced NNE–SSW and E–W trending sets. The nearly perpendicular dyke sets define a large-scale chocolate-tablet structure, implying biaxial principal extension in the WNW–ESE and N–S directions. Along the nearby north-eastern slope of Mount Reece, the WNW–ESE set locally dominates suggesting variations in the direction and amount of extension. Magnetic fabric in the dykes, revealed using the anisotropy of magnetic susceptibility (AMS) method, indicates dip-parallel to dip-oblique (?upward) magma flow. The dykes are interpreted as representing sub-volcanic feeder zones above a felsic magma source. The dyke emplacement was synchronous with the initial stages of the Weddell Sea opening during Gondwana break-up, but it remains unclear whether it was driven by regional stress field, local stress field above a larger plutonic body, or by an interaction of both.

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