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Entophysalis in the Rhynie chert (Lower Devonian, Scotland): implications for cyanobacterial evolution Geological Mag. (IF 2.3) Pub Date : 2024-02-26 Sean McMahon, Corentin C. Loron, Laura M. Cooper, Alexander J. Hetherington, Michael Krings
The ∼407-myr-old Rhynie chert of Scotland contains exquisite body fossils of land plants, animals and microorganisms, which provide our earliest reasonably complete snapshot of a Phanerozoic terrestrial ecosystem. These fossils have been instrumental to our understanding of the ‘greening of the land’, a major transition in the history of the Earth–life system. Among the primary producers preserved
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Chinese stalagmite δ18O records reveal the diverse moisture trajectories during the middle to late last glacial period Geological Mag. (IF 2.3) Pub Date : 2024-02-19 Huihui Yang, Yu-Min Chou, Xiuyang Jiang, Wei Zheng, Yaoqi He, Yogaraj Banerjee, Chuan-Chou Shen, Tsai-Luen Yu, Yi Zhong, Fabien Humbert, Qingsong Liu
Based on 30 high-resolution U-Th dating controls, we reconstruct stalagmite δ18O records from 45 to 15 thousand years ago (ka B.P., before AD 1950) from the Shizhu Cave, which is located in southwestern China under the influence of both the Indian Summer Monsoon (ISM) and the East Asian Summer Monsoon (EASM). By integrating with the other stalagmite δ18O records in Asia during the middle to late last
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Structural, lithostratigraphic and thermal features of a Permian lower crust from the Western Italian Alps (Valpelline Series, Valle d’Aosta) Geological Mag. (IF 2.3) Pub Date : 2024-02-06 Fabiola Caso, Antonella Strambini, Michele Zucali
The Valpelline Series (Dent-Blanche Tectonic System, Western Italian Alps) is a sector of lower continental crust, which consists of Permian migmatitic metapelite with different mineral assemblages (i.e., garnet-, cordierite- and orthopyroxene-bearing), minor amphibolite and marble, intruded by aplite and pegmatite. Widespread melt production in metapelite and locally in amphibolite occurred during
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The origin of the ultrahigh-pressure Tso Morari complex, NW Himalaya: implication for early Paleozoic rifting Geological Mag. (IF 2.3) Pub Date : 2024-01-25 Takeshi Imayama, Dripta Dutta, Keewook Yi
The origins and age distribution of the Himalayan high-pressure (HP) and ultrahigh-pressure (UHP) metamorphic rocks are critical for understanding the pre-Himalayan history. Although the protoliths to the UHP Tso Morari eclogites in Ladakh, NW Himalaya are believed to be the Permian Panjal volcanics, the geochronological evidence is absent. Here, we demonstrate that the protoliths of the UHP Tso Morari
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Fluctuation in redox conditions and the evolution of early Cambrian life constrained by nitrogen isotopes in the middle Yangtze Block, South China Geological Mag. (IF 2.3) Pub Date : 2024-01-18 Kai Wei, Hansheng Cao, Fajin Chen, Zaiyun Wang, Zhihui An, Hanli Huang, Chunqing Chen
The Ediacaran–Cambrian (E-C) transition (∼542–517 Ma) witnessed the rapid evolution of Cambrian animals, which was accompanied by carbon cycling anomalies and a significant increase in the concentration of oxygen in Earth’s atmosphere. The mechanisms stimulating the evolution of complex eukaryotes, however, remain problematic, especially concerning the link between biological evolution and contemporaneous
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Contextual relationship between mechanical heterogeneity and dyking: constraints from magma emplacement dynamics of the ca. 2.21 Ga Anantapur–Kunigal mafic dyke swarm, Dharwar Craton, India Geological Mag. (IF 2.3) Pub Date : 2024-01-10 Srinjoy Datta, Amiya K. Samal, Sayandeep Banerjee, Rajesh K. Srivastava
Mafic dykes are typically emplaced through primary hydraulic fracturing of undeformed crust or may make use of pre-existing crustal inhomogeneities, representing the plumbing systems of a large igneous province. The Eastern Dharwar Craton has dense exposures of several generations of Paleoproterozoic mafic dyke swarms ranging from ca. 2.37 Ga to ca. 1.79 Ga. Herein, using anisotropy of magnetic susceptibility
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Tectonic evolution of the Middle-Late Permian orogenic belt in the eastern part of the CAOB: Implications from the magmatism in the Changchun-Kaiyuan area Geological Mag. (IF 2.3) Pub Date : 2024-01-10 Nuo Zhang, Zhenghong Liu, Zhongyuan Xu, Gang Li, Xiaojie Dong, Jin Liu, Wenqing Li
Various magmatisms during the subduction-collision process are crucial to reveal the long-term tectonic evolution of the eastern Central Asian Orogenic Belt. In this paper, we present major and trace elements of whole-rock, zircon U-Pb dating and Hf isotope of the Shanmen pluton. Results imply that the Shanmen pluton consists of quartz diorite and mylonitic granite, with zircon U-Pb ages of 263.7–259
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Linking the impact of seismicity on palaeogeographic evolution and sedimentary architecture: A case study from Middle Jurassic succession of Spiti Himalaya Geological Mag. (IF 2.3) Pub Date : 2024-01-03 Sabyasachi Mandal, Abha Singh, Santanu Banerjee, Premraj Uddandam, Ranveer Singh Negi
The traces left by earthquakes in the unlithified sediments, recorded as soft-sediment deformation structures (SSDS), are well reconstructed as palaeo-seismic signals, while the origin of SSDS, seismic vs. Aseismic, is challenging. The present study discusses the origin of SSDS and its implications on palaeoceanography and sediment architecture. In the Middle Jurassic succession of Spiti Himalayan
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Cryogenian-Ediacaran crustal growth and evolution of the active margin of the Dahomeyide belt, Ghana Geological Mag. (IF 2.3) Pub Date : 2024-01-02 Daniel Kwayisi, Emmanuel Nyavor, Elikplim Abla Dzikunoo, Iris Ekua Mensimah Fynn, Jacob Kutu, Prosper M Nude
The study presents detailed petrographical, geophysical, structural and geochemical data of the internal nappes zone to establish the deformational history, origin and tectonic setting and constrain the crustal growth and evolution of the active margin of the Dahomeyide belt. Two main lithological units, (i) deformed meta-granitoids (migmatites and gneisses) and (ii) undeformed granitoids, dominate
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Ordovician sedimentation and basin development in the North Armorican Massif, NW France: Field evidence from the northern Cotentin Peninsula Geological Mag. (IF 2.3) Pub Date : 2023-12-14 David J. Went
Field evidence from the northern Cotentin Peninsula and regional data are used to construct a tectono-stratigraphic model for the Ordovician which characterizes basin development in the North Armorican Massif. In La Hague, 15 m of transgressive marine sandstone belongs to the Dapingian age Grès Armoricain Formation which onlaps lower Cambrian, rift-fill deposits via an unconformity. Approximately 450 m
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Revisiting the Phanerozoic rock–diversity relationship Geological Mag. (IF 2.3) Pub Date : 2023-12-12 Lin Na, Qijian Li, Cristina Krause, Minghang Zhu, Wolfgang Kiessling
The congruence between rock quantity and biodiversity through the Phanerozoic has long been acknowledged. Rock record bias and common cause are the most discussed hypotheses: the former emphasizes that the changes in diversity through time fully reflect rock availability; the latter posits that the correlation between rock and fossil records is driven by a common cause, such as sea-level changes. Here
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Zircon U-Pb chronology, geochemistry and geological significance of the Tongjiang-Fuyuan Mesozoic magmatic rocks, NE China Geological Mag. (IF 2.3) Pub Date : 2023-12-11 Tao Chen, Weimin Li, Yongjiang Liu, Zhiqiang Feng, Yingli Zhao, Tongjun Liu, Jinhui Gao, Shigang Zheng, Junfeng Zhao
Typical ophiolitic rock assemblages such as siliciclastic rocks, basalts and gabbros, together with the subduction-related intermediate-acidic intrusive rocks, are newly discovered in the Tongjiang-Fuyuan area of the Heilongjiang Provence, NE China. To determine the formation age and genesis of the mafic rocks (basalts and gabbros) and intermediate-acidic intrusive rocks (granodiorites) in the area
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Superposed fracture networks Geological Mag. (IF 2.3) Pub Date : 2023-12-04 D.C.P. Peacock, D.J. Sanderson, M. Magán
The concept of superposed fracture networks consisting of different generations, and often types, of fractures that have developed sequentially is discussed. Superposed networks can consist of different types of extension or shear fractures, and each fracture may abut, cross or follow (reactivate) earlier fractures. An example of a superposed fracture network in Liassic limestones in Somerset, UK,
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U-Pb zircon dates from North American and British Avalonia bracket the Lower–Middle Cambrian boundary interval, with evaluation of the Miaolingian Series as a global unit Geological Mag. (IF 2.3) Pub Date : 2023-12-04 Ed Landing, Mark D. Schmitz, Stephen R. Westrop, Gerd Geyer
High-precision U-Pb zircon ages on SE Newfoundland tuffs now bracket the Avalonian Lower–Middle Cambrian boundary. Upper Lower Cambrian Brigus Formation tuffs yield depositional ages of 507.91 ± 0.07 Ma (Callavia broeggeri Zone) and 507.67 ± 0.08 Ma and 507.21 ± 0.13 Ma (Morocconus-Condylopyge eli Assemblage interval). Lower Middle Cambrian Chamberlain’s Brook Formation tuffs have depositional ages
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How old is the Ordovician–Silurian boundary at Dob’s Linn, Scotland? Integrating LA-ICP-MS and CA-ID-TIMS U-Pb zircon dates Geological Mag. (IF 2.3) Pub Date : 2023-11-22 Hector K. Garza, Elizabeth J. Catlos, Kevin R. Chamberlain, Stephanie E. Suarez, Michael E. Brookfield, Daniel F. Stockli, Richard A. Batchelor
Sedimentary rocks exposed at Dob’s Linn, Scotland, have significantly influenced our understanding of how life evolved over the Ordovician to Early Silurian. The current interpreted chronostratigraphic boundary between the Ordovician and Silurian periods is a Global Boundary Stratotype Section and Point (GSSP), calibrated to 443.8 ± 1.5 Ma (Hirnatian–Rhuddanian age), based on biostratigraphic markers
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Genesis of the Jinying gold deposit, southern Jilin Province, NE China: Constraints from geochronology and isotope geochemistry Geological Mag. (IF 2.3) Pub Date : 2023-11-16 Yong Zhang, Yushi Wu, Huali Li, Jilong Han, Quanheng Song
The Jinying gold deposit is located in southern Jilin Province in northeast China and is representative of the large Early Cretaceous gold deposits in this area. To better understand ore genesis of this deposit, a multi-isotope integrated analysis of U–Pb–Rb–Sr–He–Ar–S has been carried out. Laser ablation inductively coupled plasma–mass spectrometry (LA–ICP–MS) dating of zircons from the granodiorite
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Subducted oceanic slab break-off in a post-collisional setting: Constraints from petrogenesis of Late Carboniferous dykes in central West Junggar, Xinjiang, NW China Geological Mag. (IF 2.3) Pub Date : 2023-11-15 Rui Gao, Jinke Li, Andrew C. Kerr, Tao Wu, Long Xiao, Guocan Wang, Xinxing He
Numerous Late Carboniferous – Early Permian dykes are found in West Junggar and represent an important part of the Central Asian Orogenic Belt. In this contribution, we use these dykes to assess the tectonic regime and stress state in the Late Carboniferous – Early Permian. The West Junggar dykes are mainly diorite/dioritic porphyrite with minor diabase and were formed in 324–310 Ma. They have been
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Multiple sediment source infill in a low-accommodation basin: implications for the late Paleozoic sediment routing system in the southeastern Ordos Basin Geological Mag. (IF 2.3) Pub Date : 2023-10-31 Chao Fu, Xinghe Yu, Shunli Li
Late Paleozoic strata in the southeastern Ordos Basin comprise targeted reservoirs for tight gas exploration. As a typical intracratonic basin, the Ordos Basin is characterized by low-accommodation space and a complex sediment infilling process, which attracts much attention. During the early Permian, the southeast area was fed by sediments from multiple sediment sources, which makes it difficult to
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The prevalence of invertebrate bioerosion on Mesozoic marine reptile bone from the Jurassic and Cretaceous of the United Kingdom: new data and implications for taphonomy and environment Geological Mag. (IF 2.3) Pub Date : 2023-10-31 Sarah Jamison-Todd, Paul Upchurch, Philip D. Mannion
Invertebrate bioerosion on fossil bone can contribute to reconstructions of benthic taxonomic assemblages and inform us about oxygenation levels, water depth and exposure time on the seafloor prior to burial. However, these traces are not commonly described in the fossil record. To date, there have been only 13 published studies describing a total of 15 instances of invertebrate bioerosion on marine
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Phosphorous concentration in iron-rich rocks of the Chilpi Group, Bastar Craton, India: implications on late Palaeoproterozoic seawater palaeo-productivity Geological Mag. (IF 2.3) Pub Date : 2023-10-27 Prasanta Kumar Mishra, Sarada Prasad Mohanty, Debadutta Mohanty, Mrinal Kanti Mukherjee
The concentration of the bio-limiting nutrient element, phosphorus (P), in seawater is important for primary marine productivity and the evolution of life on geological time scales. The molar percentage of P/Fe in banded iron formations (BIF) and iron oxide-rich chemical sediments is a good proxy for the first-order approximation of seawater P concentration. Bio-available concentration of phosphorus
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New Ediacaran biota from the oldest Nama Group, Namibia (Tsaus Mountains), and re-definition of the Nama Assemblage Geological Mag. (IF 2.3) Pub Date : 2023-10-23 Rachel Wood, Fred. T. Bowyer, Ruaridh Alexander, Mariana Yilales, Collen-Issia Uahengo, Kavevaza Kaputuaza, Junias Ndeunyema, Andrew Curtis
The Nama Group, Namibia (≥550.5 to <538 million years ago, Ma), preserves one of the most diverse metazoan fossil records of the terminal Ediacaran Period. We report numerous features that may be biological in origin from the shallow marine, siliciclastic, lowermost Mara Member (older than ca. 550.5 Ma) from the Tsaus Mountains. These include forms that potentially represent body fossils, Beltanelliformis
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First confident evidence of moulting in eodiscid trilobites from the Cambrian Stage 3 of South China Geological Mag. (IF 2.3) Pub Date : 2023-10-19 Yifan Wang, Jorge Esteve, Xinglian Yang, Rongxing Yu, Dezhi Wang
Trilobite moulting behaviour has been extensively investigated. However, exuviae in eodiscid trilobites are poorly known. Here, we report two eodiscid trilobite specimens, Tsunyidiscus niutitangensis and Tsunyidiscus sp., showing Somersault configuration from the Niutitang Formation and Mingxinsi Formation of South China, respectively (Cambrian Series 2, Stage 3). The arrangements of the exoskeletons
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High primary productivity in an Ediacaran shallow marine basin influenced by strong seasonal to perennial upwelling Geological Mag. (IF 2.3) Pub Date : 2023-10-19 A.H. Ansari, S.K. Pandey, Shamim Ahmad, Mukund Sharma, Pawan Govil, Amritpal Singh Chaddha, Anupam Sharma
A significant area of late Neoproterozoic–early Cambrian seafloor hosted a ferruginous to euxinic condition as a result of expanded primary productivity-driven pumping of organic matter into subsurface water column and weak water column mixing in the concomitant sea. However, the cause and extent of increased marine primary productivity during this time interval remain unknown. To estimate the primary
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High-pressure metamorphism of Precambrian continental crust in the southwestern part of the Central Asian Orogenic Belt (South Kazakhstan and North Tien Shan) and tectonic implications for the evolution of the Palaeo-Asian Ocean Geological Mag. (IF 2.3) Pub Date : 2023-10-19 Anfisa V. Skoblenko (Pilitsyna), Nadezhda A. Kanygina, Alexander S. Dubenskiy, Valentina G. Batanova, Yildirim Dilek, Victor S. Sheshukov, Pavel A. Serov
In this study, we investigated the high-pressure (HP) metamorphism of the Precambrian continental crust exposed in the Zheltau terrane in South Kazakhstan (Koyandy complex) and the Chu-Kendyktas terrane in the North Tien Shan of Kyrgyzstan (Aktyuz, Kemin and Kokdzhon complexes) within the SW part of the Central Asian Orogenic Belt. HP quartz–feldspar lithologies of the Koyandy complex consist of migmatized
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The jadeitites from Syros and Tinos, Cycladic Blueschist Unit, Greece: field observations, mineralogical, geochemical and geochronological characteristics Geological Mag. (IF 2.3) Pub Date : 2023-10-16 Michael Bröcker
This study illustrates the field relationships of jadeitite-bearing block-in-matrix sequences on Syros and Tinos, Cycladic Blueschist Unit, and adds additional U–Pb zircon ages for jadeitites to the geochronological database. The results confirm the importance of Cretaceous (c. 80 Ma) and Eocene (c. 50 Ma) processes in their geological evolution. Interpretations suggesting that the jadeitites were
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The latest encrinurid trilobites from the Lower Devonian of Xinjiang, Northwest China Geological Mag. (IF 2.3) Pub Date : 2023-10-09 Juan Ma, Jiayi Yin, Yilong Liu, Xiaoqi Du, Shibo Liu, Ruiwen Zong
Encrinurids are common in Ordovician and Silurian strata but whether they survived into the Early Devonian is still controversial. This paper documents the encrinurid Batocara sp. near the Silurian–Devonian boundary in western Junggar, Xinjiang. The highest horizon of Batocara sp. is located above the first appearance datum of the Devonian conodont Caudicriodus, confirming that encrinurids may cross
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Lattice preferred orientation of quartz in granitic gneisses from Tso Morari Crystalline Complex, Eastern Ladakh, trans-Himalaya: evaluating effect of Dauphiné twin in dynamic recrystallization during exhumation Geological Mag. (IF 2.3) Pub Date : 2023-10-04 Alosree Dey, Koushik Sen, Manish A. Mamtani
The Tso Morari Crystalline complex (TMCC) of eastern Ladakh, India, is part of the north Indian continental margin and is characterized by eclogitic enclaves embedded within ortho- and paragneisses known as the Puga Gneiss. Two fault zones bound the TMCC: the Karzok fault to the southwest and the Zildat fault to the northeast. In the present study, we carried out Electron Backscatter Diffraction study
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Provenance of the early Palaeozoic volcano-sedimentary successions from eastern part of the Central Sudetes: implications for the tectonic evolution of the NE Bohemian Massif Geological Mag. (IF 2.3) Pub Date : 2023-10-02 Jacek Szczepański, Gabriela Kaszuba, Robert Anczkiewicz, Sławomir Ilnicki
The Kamieniec Metamorphic Belt (KMB) and the Doboszowice Metamorphic Complex (DMC) expose a fragment of the pre-Variscan volcano-sedimentary cover preserved in the Fore-Sudetic Block in the NE part of the Bohemian Massif. We present the age of detrital and magmatic zircon grains and the bulk rock chemical composition of rock samples from the KMB and the DMC to better understand the evolution of the
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Provenance of a Late Permian retroarc foreland basin along the eastern Gondwanan margin: northern Sydney Basin, eastern Australia Geological Mag. (IF 2.3) Pub Date : 2023-09-26 Angelos G. Maravelis, Robin Offler, Chrysanthos Botziolis, George Pantopoulos, Alexandra Scott, Bill Landenberger, William J. Collins
The Upper Permian sedimentary successions in the northern Sydney Basin have been the subject of several stratigraphic, sedimentological and coal petrographic studies, and recently, extensive U-Pb zircon dating has been carried out on tuffs in the Newcastle Coal Measures. However, detailed petrographic and geochemical studies of these successions are lacking. These are important because a major change
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The genesis of calcite and dolomite carbonatite-forming magma by liquid immiscibility: a critical appraisal Geological Mag. (IF 2.3) Pub Date : 2023-09-15 John Gittins, Roger H. Mitchell
Liquid immiscibility has become the preferred mode of genesis for the carbonatite rocks, which commonly, but not exclusively, accompany silicate rocks in alkaline-rock complexes. This concept has been universally based on the presumption that nephelinitic and phonolitic magmas can evolve to a stage where two conjugate immiscible liquids separate. It is assumed that these two liquids separate quickly
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Structure of the Assynt window, Moine Thrust Zone and relationship of thrusts to alkaline igneous complexes, Caledonian orogeny, NW Scotland Geological Mag. (IF 2.3) Pub Date : 2023-09-12 Michael P. Searle
The Moine Thrust Zone forms the Caledonian orogenic thrust front where the Moine Supergroup metamorphic rocks have been thrust westward across the Laurentia plate stable foreland, comprising Archean-Proterozoic granulite and amphibolite facies rocks (Lewisian gneisses), with unconformably overlying Mesoproterozoic and Neoproterozoic Torridonian clastic sediments and Cambrian-Ordovician passive margin
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Chemotrophy-based phosphatic microstromatolites from the Mississippian at Drewer, Rhenish Massif, Germany Geological Mag. (IF 2.3) Pub Date : 2023-08-24 Jennifer Zwicker, Daniel Smrzka, Matthias Gothieu, Eugen Libowitzky, Michael M. Joachimski, Michael Ernst Böttcher, Jörn Peckmann
The Drewer quarry located in the Rhenish Massif is a well-studied outcrop that comprises Upper Devonian (Famennian) to Lower Carboniferous (Viséan) strata. Within the Drewer deposits two black shale intervals have been described that are linked to two global oceanic anoxic events, the Hangenberg Event and the Lower Alum Shale Event. The black shales associated with the Middle Tournaisian Lower Alum
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Multi-phase ecological change on Indian subcontinent from the late Miocene to Pleistocene recorded in the Nicobar Fan Geological Mag. (IF 2.3) Pub Date : 2023-08-14 Brian House, Kevin T. Pickering, Richard Norris
Modern grasslands on the Indian subcontinent, North and South America, and East Africa expanded widely during the late Miocene – earliest Pleistocene, likely in response to increasing aridity. Grasses utilizing the C4 photosynthetic pathway are more tolerant of high temperatures and dry conditions, and because they induce less C isotope fractionation than plants using the C3 pathway, the expansion
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Geochemistry, zircon U–Pb geochronology and Hf isotope of the early Permian gabbro and high-Mg diorites from the Zhusileng–Hangwula Belt in the northern Alxa area: Petrogenesis and tectonic implications Geological Mag. (IF 2.3) Pub Date : 2023-08-11 Wen Bing Deng, Zhao Gang Shao, Hai Jin Xu, Xuan Hua Chen, Jin Jun Yi, Su Jiang Zhang
As the southernmost part of the central segment of the Central Asian Orogenic Belt, the northern Alxa area is characterized by abundant Permian magmatism and records key information on the geological evolution of the Palaeo-Asian Ocean. This study reports new zircon U–Pb and Lu–Hf isotopic and whole-rock geochemical data of the early Permian (285–286 Ma) Huisentala gabbro and Huodonghaer diorites from
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The genesis of metamorphosed Paleoproterozoic massive sulphide occurrences in central Colorado: geological, mineralogical and sulphur isotope constraints Geological Mag. (IF 2.3) Pub Date : 2023-08-07 Edward H. Berke, Paul G. Spry, Adriana Heimann, Graham S. Teale, Benjamin Johnson, Anette von der Handt, Brian Alers, John M. Shallow
Paleoproterozoic massive Cu-Zn±Pb±Au±Ag sulphide deposits metamorphosed to the middle-upper amphibolite facies in central-south Colorado formed in a volcanic arc setting on the edge of the Yavapai crustal province. Previously published U-Pb ages on spatially related granitoids range from ∼1.9 to ∼1.1 Ga, while Pb isotope studies on galena from massive sulphides suggest mineralization formed at around
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Metamorphic and intrusive history of the Hindu Raj region, northern Pakistan Geological Mag. (IF 2.3) Pub Date : 2023-08-04 Kyle P. Larson, Brendan Dyck, Shah Faisal, John M. Cottle, Mike Searle
The Hindu Raj region of northern Pakistan is situated between the Karakoram to the east and the Hindu Kush to the west. Both the Karakoram and the Hindu Kush are better studied and have well-documented, distinct geological histories. Investigation of the Hindu Raj region has been mainly limited to reconnaissance exploration and as such little is known about its tectonometamorphic history and whether
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Rapid exhumation of young granites in an extensional domain: the example of the Giglio Island pluton (Tuscany) Geological Mag. (IF 2.3) Pub Date : 2023-08-03 Chinedu Uduma Ibe, Antonio Langone, Finlay M. Stuart, Andrea Brogi, Alfredo Caggianelli, Domenico Liotta, Fabrizio Tursi
The presence of recently intruded granites at Earth’s surface suggests that their exhumation may have occurred rapidly. The Neogene granites of the Tuscan Magmatic Province (Italy) were emplaced during a period of extensional tectonics and are ideal for determining and quantifying the exhumation process. The peraluminous monzogranite of Giglio Island in the northern Tyrrhenian Sea is characterized
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The physical volcanology of large-scale effusive and explosive silicic eruptions in southeastern Saurashtra, Deccan Traps Geological Mag. (IF 2.3) Pub Date : 2023-07-31 Anmol Naik, Hetu Sheth, Alok Kumar, Janisar M. Sheikh
Silicic magmatism, minor overall in the ∼65.5 Ma Deccan Traps continental flood basalt (CFB) province of India, was widespread in the Saurashtra region. We describe the physical volcanology of silicic volcanics and dykes exposed around Rajula–Savarkundla–Gariyadhar–Talaja towns in southeastern Saurashtra. The silicic volcanics conformably overlie basaltic lavas, suggesting rapid subaerial volcanism
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Death by ammonite: fatal ingestion of an ammonoid shell by an Early Jurassic bony fish Geological Mag. (IF 2.3) Pub Date : 2023-07-24 Samuel L. A. Cooper, Erin E. Maxwell
A remarkable specimen of the actinopterygian fish Pachycormus macropterus from the Early Jurassic (Toarcian) Posidonienschiefer Formation of Germany exceptionally preserves an unusually large ammonite inside its gut. The ammonite was swallowed by the fish, likely by accident, and represents the first direct evidence for an actinopterygian fish consuming an ammonoid. Exceptional aragonite preservation
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Cenozoic evolution of the Tripolitza carbonate platform in the Tethyan realm: new age constraints on deposition, diagenesis, metamorphism and nappe emplacement based on U-Pb and Rb-Sr dating (External Hellenides, Crete) Geological Mag. (IF 2.3) Pub Date : 2023-07-20 T. Klein, G. Zulauf, D. Evans, A. Gerdes, J. Glodny, F. Heidelbach, F. Kirst, J. Linckens, W. Müller, E. Özcan, R. Petschick, P. Xypolias
We present kinematic, radiometric, geochemical and PT data, which help to constrain the tectonometamorphic evolution of the Tripolitza Unit (TPU). The age of both the metamorphic peak (P = 0.4 ±0.2 GPa, T = ca. 310 °C) and top-to-the WNW mylonitic thrusting, attributed to the emplacement of the hanging Pindos nappe, has been constrained at 19 ±2.5 Ma using Rb-Sr on synkinematic white mica of a basal
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Geochronology and formal stratigraphy of the Sturtian Glaciation in the Adelaide Superbasin Geological Mag. (IF 2.3) Pub Date : 2023-07-20 Jarred C. Lloyd, Wolfgang V. Preiss, Alan S. Collins, Georgina M. Virgo, Morgan L. Blades, Sarah E. Gilbert, Darwinaji Subarkah, Carmen B.E. Krapf, Kathryn J. Amos
The glaciogenic nature of the Yudnamutana Subgroup was first recognized over a century ago, and its global significance was recognized shortly after, with the eventual postulation of a global Sturtian Glaciation and Snowball Earth theory. Much debate on the origin and timing of these rocks, locally and globally, has ensued in the years since. A significant corpus of research on the lithology, sedimentology
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“Geochronology and geochemistry of pelitic granulite from the South Delhi Terrane of the Aravalli Delhi Mobile Belt, NW India: implications for petrogenesis and geodynamic model” Geological Mag. (IF 2.3) Pub Date : 2023-07-12 M. Kumar, D. Prakash, C. K. Singh, S. Singh, R. K. Pandey, Pradip K. Singh, B. Mahanta
An attempt has been made to illustrate the evolution of pelitic granulite from south of the Balaram-Abu road, which lies in the South Delhi Terrane (SDT) of the Aravalli-Delhi Mobile Belt (ADMB), using geochemistry and geochronology. The current work offers a plausible explanation for the protolith of pelitic granulite, nature of the sediments and its provenance. The elemental geochemistry of the pelitic
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Constraining the evolution of shear zones in the Himalayan mid crust in Central–Western Nepal: implications for the tectonic evolution of the Himalayan metamorphic core Geological Mag. (IF 2.3) Pub Date : 2023-07-05 Rodolfo Carosi, Chiara Montomoli, Salvatore Iaccarino, John M. Cottle, Hans-Joachim Massonne, Laura Nania, Matteo Simonetti
Structural analysis, petrochronology and metamorphic petrology enable identification and bracketing of the timing of a newly mapped high-temperature ductile shear zone (Jagat Shear Zone (JSZ)) in the Himalayan metamorphic core in Central-Western Nepal. In situ U-Th-Pb monazite petrochronology constrains the timing of top-to-the-S/SW shearing between 28–27 Ma and 17 Ma. Burial and prograde metamorphisms
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Glacial sedimentation in Northern Gondwana: insights from the Talchir formation, Manendragarh, India Geological Mag. (IF 2.3) Pub Date : 2023-06-26 Adrita Choudhuri, Sabyasachi Mandal, Adam Bumby, S. Suresh Kumar Pillai
Among the vast swathes of Gondwanan sedimentary rocks in India, exposures of the Lower Permian Talchir Formation at Manendragarh in India are exceptional for their cold marine faunal assemblage and muddy conglomerates of possible glacial origin. They may represent a record of the late Palaeozoic glaciation that affected Gondwana in the Permo-Carboniferous. Although the fossil record is relatively well
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Granitic magmatism associated with gold mineralization: evidence from the Baizhangzi gold deposit, in the northern North China Craton Geological Mag. (IF 2.3) Pub Date : 2023-06-21 Zhi-xiong Zhao, Wei-jun Xu, Guo-chen Dong, M Santosh, Hong-bin Li, Ze-guang Chang
The relationship between magmatism and gold mineralization has been a topic of interest in understanding the formation of ore deposits. The Baizhangzi gold deposit, located in the northern margin of the North China Craton, is hosted by the Baizhangzi granite (BZG) and provides a case to evaluate the relation between granite and gold mineralization in Late Triassic. In this study, we present petrography
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The Sr, Nd, Pb and Hf isotopes and crystallization conditions of the middle Eocene Dağdibi Pluton in the eastern Sakarya Zone, Turkey Geological Mag. (IF 2.3) Pub Date : 2023-06-07 Ferkan Sipahi, Mehmet Ali Gücer, Abdurrahman Dokuz, Keewook Yi, Abdullah Kaygusuz, Enver Akaryalı, Çiğdem Saydam Eker, Cüneyt Doruk
Magmatic activity in the Sakarya Zone, an important segment of the Alpine orogenic belt, continues intermittently from the middle Carboniferous to Miocene. In this study, we provide geochronological and geochemical data from the Dağdibi Pluton in the eastern Sakarya Zone to present some inferences on the source region and petrogenesis of the middle Eocene magmatism. U–Pb zircon geochronology from two
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Lower Permian (Late Kungurian) conodonts from the Sibumasu Terrane, Malaysia: paleoecological, paleobiogeographical and tectonic implications Geological Mag. (IF 2.3) Pub Date : 2023-05-23 I. Metcalfe
Late Kungurian (Lower Permian) conodonts are described from the Kanthan Limestone, Perak, Peninsular Malaysia and for the first time from the Sibumasu Terrane of the Malay Peninsula. The co-occurrence of Gullodus duani, Gullodus hemicircularis, Gullodus sicilianus, Mesogondolella lamberti and Mesogondolella siciliensis represent the Mesogondolella lamberti International Conodont Zone and the broadly
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Paleo-trade wind directions over the Yangtze Carbonate Platform during the Cambrian–Ordovician, Southern China Geological Mag. (IF 2.3) Pub Date : 2023-05-17 Chenlin Hu, Tianyou Qin, Jinghui Ma, Changcheng Han, Xuliang Wang
The Sichuan Basin was a part of the Yangtze Carbonate Platform (YCP) during the Cambrian–Ordovician, and marine carbonates were deposited in the basin during this interval. Although previous studies have evaluated the paleogeography, paleoclimate and paleoecology of this basin, they have primarily focused on the paleoecology and biological evolution in the basin; however, analysis of paleogeography
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Early Precambrian mafic dykes in western Shandong province, North China Craton: constraints on the chronology, genetic model and tectonic significance Geological Mag. (IF 2.3) Pub Date : 2023-05-02 Shen Liu, Caixia Feng, Guangying Feng, Yan Fan, Zhuang Guo
In the Late Neoarchaean, the lithosphere of the North China Craton (NCC) experienced a strong extensional event, which is of great significance for understanding the evolution of the continental crust in the Precambrian. In this study, a suite of mafic dykes from Shandong province in the northeastern NCC were investigated to determine the nature, timing and source of rift-related magma activities using
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Petrogenesis of Early Cretaceous volcanic rocks from the Rena-Co area in the southern Qiangtang Terrane, central Tibet: evidence from zircon U-Pb geochronology, petrochemistry and Sr-Nd-Pb–Hf isotope characteristics Geological Mag. (IF 2.3) Pub Date : 2023-05-02 Shaogang Wei, Juxing Tang, Yang Song, Baolong Li, Yujie Dong
The subduction of the Bangong–Nujiang Ocean is important in the geological evolution of the Tibetan Plateau. In this paper, we report new zircon U-Pb age and Lu-Hf isotopic data and whole-rock elemental and Sr-Nd-Pb isotopic data for Early Cretaceous dacites from the Rena-Co area (RCA) in the southern Qiangtang Terrane (QT), central Tibet and use these data to better understand the tectonic evolution
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Foraminifers and conodonts in the Danlu section, South China: implications for the Viséan–Serpukhovian boundary (Mississippian) Geological Mag. (IF 2.3) Pub Date : 2023-04-28 Chao Liu, Pedro Cózar, Ismael Coronado, Tian Liang, Xiaoxiao Liu, Hao Chen, Xin Li, Haihua An, Fukai Zhang
The Viséan–Serpukhovian boundary is poorly defined in South China, hampering regional and global stratigraphical correlations. The foraminiferal and conodont distribution of the Baping Formation in the carbonate-slope Danlu section permits the recognition of an interval from the middle Viséan to the uppermost Serpukhovian in a continuous succession. The base of the Serpukhovian in Danlu is recognized
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Geochemical constraints on the petrogenesis of mafic rocks (metadolerites) from the Proterozoic Shillong Basin, Northeast India: implications for growth of the Greater Indian Landmass Geological Mag. (IF 2.3) Pub Date : 2023-04-27 Pallabi Basumatary, Ashima Saikia, Tribujjal Prakash, Bibhuti Gogoi
The Paleo-Mesoproterozoic Shillong Basin of the Assam-Meghalaya Gneissic Complex is exposed in parts of Northeast India. The studied metadolerites are from the volcano-sedimentary sequence of Shillong Basin from the Borjuri area in the Mikir Massif. This episode of mafic magmatism can be correlated with the Columbia supercontinent formation and bears significance to its reconstruction. The present
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Geochemical characterization, U–Pb apatite geochronology, and geodynamic significance of olivine minette dykes from the Julian Alps, NE Italy Geological Mag. (IF 2.3) Pub Date : 2023-04-11 Francesco Narduzzi, Maurizio Ponton, Michele Marello, Marco Paulo de Castro, Gláucia Queiroga, Angelo De Min
We investigated olivine minette dykes from the Rio Colan Valley of the Julian Alps (NE Italy) to provide new constraints on the mantle geochemistry underneath this extreme sector of the Italian Southern Alps. Petrographic observations, high Mg#s, high Cr and Ni contents, low Dy/YbCN ratios and flat heavy rare earth element (REE) profiles imply these are primary magmas derived from a depleted peridotite
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Isotopic decoupling of K from Sr and Nd in the Saima alkaline complex, NE China: interactions of cratonic roots and asthenosphere Geological Mag. (IF 2.3) Pub Date : 2023-04-05 Nan Gao, Yingkui Xu, Dan Zhu, Yang Li, Xiongyao Li, Jianzhong Liu, Jin-Cheng Luo
We report high-precision K isotopes, apatite U–Pb ages, whole-rock elements and Sr–Nd isotopes for the Saima nephelite syenite in the North China Craton. Trace-element and Sr–Nd–Hf–O isotope data indicate the presence of subducting sediments in the source region, while K isotopic compositions show a narrow range between –0.54 ‰ and –0.28 ‰, with an average of –0.41 ± 0.06 ‰, identical to the value
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Petrogenesis and tectonic implications of the Early Carboniferous shoshonitic to calc-alkaline magmatic rocks of the southern Yili terrane, western Tianshan Geological Mag. (IF 2.3) Pub Date : 2023-04-04 Hao Xing, Chunji Xue, Xiaobo Zhao, DTA Symons, Pengqiao Niu
In the Yili terrane at Awulale mountain, most shoshonitic lavas are related to post-collision extension and were extruded during the Late Carboniferous to Early Permian (310–280 Ma). Herein, we evaluate a small-volume occurrence of shoshonitic magmas in the southern Yili terrane formed c. 346 Ma ago. The high MgO (Mg#) and positive Hf isotope values of the shoshonitic magmas indicate the input of juvenile
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Geochemistry and Sr–Nd isotopic characteristics of ferroan-magnesian metaluminous granites of the NW Sanandaj–Sirjan zone, Iran: granite formation in a compressional–extensional setting during Late Jurassic time Geological Mag. (IF 2.3) Pub Date : 2023-04-03 Majid Shirmohammadi, Ali Asghar Sepahi, José Francisco Santos, Mohammad Maanijou, Ashraf Torkian, Hamed Vahidpour
The Almogholagh–Dehgolan region is in the North Sanandaj–Sirjan zone of NW Iran. The granites of the region are metaluminous and display geochemical and textural characteristics of transitional granites between ferroan (A-type) and I-type granites. In geotectonic discrimination diagrams, the Almogholagh–Dehgolan granites plot mainly in the fields of within-plate granites and volcanic arc granites.
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Nature of the Shyok (Northern) Suture Zone between India and Asia: petrology, geochemistry and origin of the Tirit granitoids and associated dykes (Nubra Valley Ladakh Himalaya, NW India) Geological Mag. (IF 2.3) Pub Date : 2023-04-03 Rakesh Chandra, Nazia Kowser, Michael E Brookfield, Manavalan Satyanarayanan, Daniel Stöckli
The Shyok Suture Zone is an oceanic remnant of the Neo-Tethyan ocean sandwiched between the Ladakh Batholiths to the south and Karakoram Batholith to the north. The Tirit granitoids in this suture are dark-coloured, relatively rich in ferromagnesian minerals and range from granodiorite–tonalite to gabbro–diorite in composition. Mafic igneous enclaves are quite common and they are intruded by NW–SE
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New Cretaceous crickets of the subfamilies Nemobiinae and Podoscirtinae (Orthoptera, Grylloidea: Trigonidiidae, Oecanthidae) attest the antiquity of these clades Geological Mag. (IF 2.3) Pub Date : 2023-04-03 Laure Desutter-Grandcolas, Hugo Josse, Marie Laurent, Lucas Denadai de Campos, Sylvain Hugel, Carmen Soriano, André Nel, Vincent Perrichot
Fossils are more and more used in phylogenetic evolutionary studies either for clade calibration, or as terminals in a dataset including morphological characters. The strength of these methodological advances relies however on the quality and completeness of the fossil record. For crickets (Insecta, Orthoptera, Gryllidea), few ancient (pre-Cenozoic) well-preserved fossils are known, except for isolated
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Age and petrogenesis of mafic granulites from central Madurai block, south India: implications on regional tectonics Geological Mag. (IF 2.3) Pub Date : 2023-03-22 J Amal Dev, JK Tomson, T Vijaya Kumar, Nilanjana Sorcar
The Precambrian Southern Granulite Terrane (SGT) of south India is well-known for the preservation of high- to ultrahigh-temperature (HT-UHT) granulites, prominently exposed in its central part forming a linear belt referred to as the Kambam UHT belt. This belt also hosts widespread occurrences of mafic granulites that are observed in close spatial association with the HT-UHT granulites. This study
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Uranium–lead geochronology applied to pyrope garnet with very low concentrations of uranium Geological Mag. (IF 2.3) Pub Date : 2023-03-21 Gary J O’Sullivan, Brendan C Hoare, Chris Mark, Foteini Drakou, Emma L Tomlinson
We present U–Pb dates from peridotitic pyrope-rich garnet from four mantle xenoliths entrained in a kimberlite from Bultfontein, South Africa. Garnet dates magmatic emplacement due to the high mantle residence temperatures of the source material prior to eruption, which were most likely above the closure temperature for the pyrope U–Pb system. We determine a U–Pb date of 84.0 ± 8.1 Ma for the emplacement