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Zircon in mantle eclogite xenoliths: a review Geological Mag. (IF 2.365) Pub Date : 2021-01-21 Aleksey E. Melnik; Nester M. Korolev; Sergey G. Skublov; Dirk Müller; Qiu-Li Li; Xian-Hua Li
Very few zircon-bearing, kimberlite-hosted mantle eclogite xenoliths have been identified to date; however, the zircon they contain is crucial for our understanding of subcratonic lithospheric mantle evolution and eclogite genesis. In this study, we constrain the characteristics of zircon from mantle eclogite xenoliths based on existing mineralogical and geochemical data from zircons from different
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Disaster microconchids from the uppermost Permian and Lower Triassic lacustrine strata of the Cis-Urals and the Tunguska and Kuznetsk basins (Russia) Geological Mag. (IF 2.365) Pub Date : 2021-01-13 Dmitry E. Shcherbakov; Olev Vinn; Andrey Yu. Zhuravlev
We describe aggregative microconchid (Lophophorata) tubes from the uppermost Permian (upper Changhsingian) and Lower Triassic (Olenekian) lacustrine and fluvial strata of the Tunguska and Kuznetsk basins and the southern Cis-Urals, Russia. These attach to clam shrimp carapaces, bivalve shells, terrestrial plant fragments and a horseshoe crab head shield, and also form their own monospecific agglomerations
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Geology of the recently discovered massive and stockwork sulphide mineralization at Semblana, Rosa Magra and Monte Branco, Neves–Corvo mine region, Iberian Pyrite Belt, Portugal Geological Mag. (IF 2.365) Pub Date : 2021-01-11 Zélia Pereira; João X. Matos; A. Rita Solá; Maria João Batista; Rute Salgueiro; Carlos Rosa; Luís Albardeiro; Márcia Mendes; Igor Morais; Daniel de Oliveira; Nelson Pacheco; Vitor Araújo; José M. Castelo Branco; Rodrigo Neto; João Lains Amaral; Carlos Inverno; José T. Oliveira
The recently discovered massive and stockwork sulphide mineralization of Semblana-Rosa Magra and Monte Branco, situated ESE of the Neves–Corvo volcanogenic massive sulphide (VMS) deposit in the Iberian Pyrite Belt (IPB) is presented. Geological setting and tectonic model is discussed based on proxies such as palynostratigraphy and U–Pb zircon geochronology. The mineralization is found within the IPB
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U–Pb geochronology and trace-element composition of zircons from the Jinchang Au–Ni deposit, SW China, and their implications for tectonics Geological Mag. (IF 2.365) Pub Date : 2021-01-11 Lingang Xu; Zhigang Kong; Jianfei Qu; Zhiyin Qiu; Jianfeng Gao
Situated between the South China Block and the Simao Block, the Ailaoshan Belt is a significant component of the Jinshajiang–Ailaoshan tectonic-magmatic-metallogenic belt of southwestern China. The formation of the Ailaoshan Belt is closely related to the evolution of the Palaeo-Tethys Ocean. In this study, we constrain ages of sedimentation in the Jinchang Au–Ni deposit in the Ailaoshan Belt, using
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Subduction zone processes and crustal growth mechanisms at Pacific Rim convergent margins: modern and ancient analogues Geological Mag. (IF 2.365) Pub Date : 2020-12-11 Yildirim Dilek; Yujiro Ogawa
Continents grow mainly through magmatism, relamination, accretionary prism development, sediment underplating, tectonic accretion of seamounts, oceanic plateaus and oceanic lithosphere, and collisions of island arcs at convergent margins. The modern Pacific–Rim subduction zone environments present a natural laboratory to examine the nature of these processes. The papers in this special issue focus
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Magmatic record of the Mesozoic geology of Hainan Island and its implications for the Mesozoic tectonomagmatic evolution of SE China: effects of slab geometry and dynamics in continental tectonics Geological Mag. (IF 2.365) Pub Date : 2020-12-10 Yildirim Dilek; Limei Tang
Our field-based geochemical studies of the Triassic, Jurassic and Cretaceous granitoids on Hainan Island indicate that their magmas had different geochemical affinities, changing from alkaline in the Triassic through ocean island basalt (OIB) in the Jurassic, to calc-alkaline in the Cretaceous. We show that these changes in the geochemical affinities of the Mesozoic granitoids on Hainan and in SE China
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Early Jurassic palaeopolar marine reptiles of Siberia Geological Mag. (IF 2.365) Pub Date : 2020-12-28 Nikolay G. Zverkov; Dmitry V. Grigoriev; Igor G. Danilov
Marine reptile occurrences are rare in the Lower Jurassic Series outside of Europe. Here we describe diverse marine reptile faunas from the Lower Jurassic Series (Pliensbachian and Toarcian stages, including the Toarcian–Aalenian boundary interval) of Eastern Siberia. The taxonomic composition of Toarcian marine reptile assemblages of Siberia highlight their cosmopolitan nature, with the presence of
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On the oxygenation of the Archaean and Proterozoic oceans Geological Mag. (IF 2.365) Pub Date : 2020-12-23 Amlan Banerjee; Mirosław Słowakiewicz; Dilip Saha
Modern-day ocean circulation behaves as a complex forced convective system that is characterized by the decrease in water temperature but increase in water density with depth. The dissolved oxygen content – which initially decreases due to biological oxygen demand – also increases with depth. In contrast to the present-day scenario, we propose that during the Archaean and Proterozoic eons inverted
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Probable deinonychosaur tracks from the Upper Cretaceous Wapiti Formation (upper Campanian) of Alberta, Canada Geological Mag. (IF 2.365) Pub Date : 2020-12-23 Nathan J. Enriquez; Nicolás E. Campione; Corwin Sullivan; Matthew Vavrek; Robin L. Sissons; Matt A. White; Phil R. Bell
Late Cretaceous tracks attributable to deinonychosaurs in North America are rare, with only one occurrence of Menglongipus from Alaska and two possible, but indeterminate, occurrences reported from Mexico. Here we describe the first probable deinonychosaur tracks from Canada: a possible trackway and one isolated track on a single horizon from the Upper Cretaceous Wapiti Formation (upper Campanian)
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Tectonic controls on sedimentary provenance and basin geography of the Mesoproterozoic Wilton package, McArthur Basin, northern Australia Geological Mag. (IF 2.365) Pub Date : 2020-12-23 Bo Yang; Alan S. Collins; Morgan L. Blades; Tim J. Munson; Justin L. Payne; Stijn Glorie; Juraj Farkaš
The c. 1.5–1.3 Ga Wilton package, the upper succession of the greater McArthur Basin, preserves detailed tectono-sedimentary evidence for the Mesoproterozoic evolution of the North Australian Craton (NAC). In addition, it is a valuable global sedimentary repository for the poorly explored Mesoproterozoic. New detrital zircon U–Pb age and Lu–Hf isotope data, collected from multiple, geographically separated
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Zircon U–Pb ages, geochemistry and Sr–Nd isotopes of the Golshekanan granitoid, Urumieh–Dokhtar magmatic arc, Iran: evidence for partial melting of juvenile crust Geological Mag. (IF 2.365) Pub Date : 2020-12-15 Fatemeh Sarjoughian; Bahareh Zahedi; Hossein Azizi; Wenli Ling; David R. Lentz; Yoshihiro Asahara
The Golshekanan granitoid body is situated in the central part of the Urumieh–Dokhtar magmatic arc (UDMA) in central Iran, and includes granite and granodiorite with minor monzonite and diorite. Zircon U–Pb dating yields a late Eocene (Priabonian) crystallization age of 37.6 ± 0.2 Ma. The body is calc-alkaline and metaluminous to weakly peraluminous (A/CNK ≤ 1.10) with SiO2 ranging from 61.1 to 71
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Sedimentology and integrated chronostratigraphy of the lower Heatherdale Shale (Cambrian, stages 2–3), Stansbury Basin, South Australia Geological Mag. (IF 2.365) Pub Date : 2020-12-11 Feiyang Chen; Glenn A. Brock; Marissa J. Betts; Zhiliang Zhang; Hao Yun; Robert Matthew Klaebe; Brittany Laing; Zhifei Zhang
Major progress has recently been made regarding the biostratigraphy, lithostratigraphy and isotope chemostratigraphy of the lower Cambrian successions in South Australia, in particular of the Arrowie Basin, which has facilitated robust global stratigraphic correlations. However, lack of faunal and sedimentological data from the lower Cambrian Normanville Group in the eastern Stansbury Basin, South
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Petrogenesis of Silurian ultramafic–mafic plutons in southern Jiangxi: implications for the Wuyi–Yunkai orogen, South China Geological Mag. (IF 2.365) Pub Date : 2020-12-04 Jie Yang; Wei Liu; Zuozhen Han; Zuoxun Zeng; Le Wan; Adil S. Mohammed
The South China Block is one of the largest continental blocks located on the East Asian continent. The early Palaeozoic Wuyi–Yunkai orogen of the South China Block (known as the Caledonian orogen in Europe) is a major orogenic belt in East Asia and represents the first episode of extensive crustal reworking since Neoproterozoic time. Although this orogen is key to deciphering the formation and evolution
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A large pteranodontid pterosaur from the Late Cretaceous of Eastern Europe Geological Mag. (IF 2.365) Pub Date : 2020-12-03 Alexander O Averianov; Maxim S Arkhangelsky
The Campanian Beloe Ozero locality within the Rybushka Formation in Saratov Province, Russia, is one of the richest and most diverse Upper Cretaceous pterosaur localities in Europe. It produces identifiable remains of Pteranodontidae indet. and Azhdarchidae indet., as well as bones which can be attributed to either of these groups. The pteranodontid specimens from the Beloe Ozero locality described
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Detrital zircon age and biostratigraphic and chemostratigraphic constraints on the Ediacaran–Cambrian transitional interval in the Irkutsk Cis–Sayans Uplift, southwestern Siberian Platform Geological Mag. (IF 2.365) Pub Date : 2020-12-02 Vasiliy V. Marusin; Alena A. Kolesnikova; Boris B. Kochnev; Nikolay B. Kuznetsov; Boris G. Pokrovsky; Tatiana V. Romanyuk; Galina A. Karlova; Sergey V. Rud’ko; Andrey V. Shatsillo; Alexander S. Dubenskiy; Victor S. Sheshukov; Sergey M. Lyapunov
A number of ecological and geochemical transformations occurred during late Ediacaran and early Cambrian time, the effects of which are difficult to overestimate. However, the strong linkage of biostratigraphic and chemostratigraphic methods with lithofacies makes the localization of the Precambrian–Cambrian boundary and its correlation with lithologically contrasting sections highly debatable. We
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Ontogeny of the trilobite Redlichia from the lower Cambrian (Series 2, Stage 4) Ramsay Limestone of South Australia Geological Mag. (IF 2.365) Pub Date : 2020-12-02 James D. Holmes; John R. Paterson; James B. Jago; Diego C. García-Bellido
Studies that reveal detailed information about trilobite growth, particularly early developmental stages, are crucial for improving our understanding of the phylogenetic relationships within this iconic group of fossil arthropods. Here we document an essentially complete ontogeny of the trilobite Redlichia cf. versabunda from the Cambrian Series 2 (late Stage 4) Ramsay Limestone of Yorke Peninsula
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Tectonic transition from subduction to retreat of the palaeo-Pacific plate: new geochemical constraints from the late Mesozoic volcanic sequence in eastern Fujian Province, SE China Geological Mag. (IF 2.365) Pub Date : 2020-11-24 Mingxuan Cao; Xilin Zhao; Guangfu Xing; Feipeng Fan; Minggang Yu; Zheng Duan; Pingli Chu; Rong Chen
The widespread occurrence of late Mesozoic volcanic rocks in SE China is associated with widespread mineralization. Most geologists have accepted the model of Pacific plate subduction beneath the eastern Asian continent, but there are still controversies, especially the initial timing of the tectonic transition. In order to understand the tectonic evolution of the palaeo-Pacific plate subduction, an
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Shales of Palaeo-Mesoproterozoic Vindhyan Basin, central India: insight into sedimentation dynamics of Proterozoic shelf Geological Mag. (IF 2.365) Pub Date : 2020-11-23 Arvind K. Singh; Partha Pratim Chakraborty
The Vindhyan Supergroup represents the largest Proterozoic sedimentary basin fill in the Indian shield. In addition to some significant palaeobiological discoveries, the sedimentary sequence of the Vindhyan, particularly its argillaceous intervals, holds crucial information for our understanding of sedimentation dynamics in Proterozoic clastic shelves. Here we attempt an extensive, although not exhaustive
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Early Jurassic (Toarcian) warming identified from lacustrine sediments of eastern Liaoning, China Geological Mag. (IF 2.365) Pub Date : 2020-11-20 Qian Zhang; Enpu Gong; Yongli Zhang; Changqing Guan
This study focuses on the Tianshifu Basin, eastern Liaoning, China, which is filled with Lower–Middle Jurassic fluviolacustrine sediments rich in macroplants. Our aim is to explore the continental climate features of the late Early Jurassic period. The composition of the Early–Middle Jurassic flora and the carbon isotopic ratios of organic matter, total organic carbon, total organic nitrogen and sulphur
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Early Silurian granitic rocks and associated enclaves as evidence of rapid cooling in a cognate magma system: the case of the Xuehuading–Panshanchong pluton, South China Block Geological Mag. (IF 2.365) Pub Date : 2020-11-19 Quan Ou; Jian-Qing Lai; Bruna B. Carvalho; Feng Zi; Zi-Qi Jiang; Kun Wang; Yi-Zhi Liu
The study of enclaves in granitic plutons provides fundamental information on the petrogenesis of their host rocks. Here we combine U–Pb zircon ages, petrography, geochemistry and Nd–Hf isotope composition to investigate the origin of dioritic–granodioritic enclaves and their host granodiorites and biotite granites in the Xuehuading–Panshanchong area, which is a pivotal site to study the Palaeozoic
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Palaeomagnetism of the uppermost carbonate units of the Purana basins in southern India: new demagnetization results from the Kaladgi and Bhima basins, Karnataka Geological Mag. (IF 2.365) Pub Date : 2020-11-19 Herve Wabo; Michiel Olivier De Kock; Nicolas Johannes Beukes; Venkatraman Seetaram Hegde
Four unconformity-bound sequences can be identified in the Purana successions in southern India, of which the third sequence (Sequence III) has the widest distribution. Sequence III contains deep-water carbonate units with consistent sedimentological characteristics across the subcontinent. The current extent of field relationships and existing ages has not allowed the correlation and chronology of
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Fieldwork and disability: an overview for an inclusive experience Geological Mag. (IF 2.365) Pub Date : 2020-09-04 Domenico Chiarella; Grazia Vurro
Fieldwork forms the basis of geoscience studies. However, field activities present limitations for people with mental or physical impairments. This aspect can preclude participation in field trips by certain groups of students or limit their experience. In recent years, new types of supporting material and the development of accessible field trips have been a step forward towards the reduction of barriers
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Duobagou Permian–Triassic granites from the Dunhuang orogenic belt, NW China: implications for the tectonic evolution of the southernmost Central Asian Orogenic Belt Geological Mag. (IF 2.365) Pub Date : 2020-10-28 Zhendong Wang; Yuanyuan Zhang; Xiangjiang Yu; Zhaojie Guo
The Duobagou Permian–Triassic granites of the Dunhuang orogenic belt are of great importance in understanding the tectonic evolution of the southernmost Central Asian Orogenic Belt. LA-ICP-MS U–Pb zircon ages indicate that Permian–Triassic granitic intrusions from the Duobagou area formed at 276–274 Ma and 246 ± 1 Ma. These granites have high SiO2, Na2O and K2O, but low Al2O3, CaO and MgO contents
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Middle Ordovician (Darriwilian) conodonts from southern Tibet, the Indian passive margin: implications for the age and correlation of the roof of the world Geological Mag. (IF 2.365) Pub Date : 2020-10-28 Svend Stouge; David A. T. Harper; Renbin Zhan; Jianbo Liu; Lars Stemmerik
New occurrences of middle–late Darriwilian (Middle Ordovician) conodonts are reported from the Nyalam region, southern Tibet. The conodont-yielding strata, referred to the Chiatsun Group, accumulated on the north Indian continental margin of northern Gondwana. These Middle Ordovician conodonts include the informal species Histiodella sp. A in the middle part of the Lower Formation of the Chiatsun Group
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Bimodal magmatism produced by delamination: geochemical evidence from late Palaeozoic volcanic rocks from the Yili Block, Western Tianshan, Northwestern China Geological Mag. (IF 2.365) Pub Date : 2020-10-27 Genwen Chen; Rui Liu; Teng Deng; Lixing Wang
The Western Tianshan orogenic belt is essential for understanding the evolution of the Central Asian orogenic belt. However, no agreement exists among geologists about its tectonic environment during the Late Palaeozoic. The volcanic rocks of the Yishijilike and Wulang Formation in the Yili Block, Western Tianshan, formed in the Late Carboniferous to Early Permian, mainly consist of a bimodal suite
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Sedimentology and palaeontology of the Upper Karoo Group in the Mid-Zambezi Basin, Zimbabwe: new localities and their implications for interbasinal correlation Geological Mag. (IF 2.365) Pub Date : 2020-10-26 Lara Sciscio; Pia A. Viglietti; Paul M. Barrett; Timothy J. Broderick; Darlington Munyikwa; Kimberley E.J. Chapelle; Kathleen N. Dollman; Steve F. Edwards; Michel Zondo; Jonah N. Choiniere
The Triassic–Jurassic Upper Karoo Group of the Mid-Zambezi Basin (MZB; Zimbabwe) includes a thick succession of terrestrial sediments with high palaeontological potential that has been neglected since the 1970s. Here, we review the Upper Karoo Group stratigraphy, present detailed sedimentological work and identify new vertebrate-bearing sites at several measured sections along the southern shore of
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Hidden diversity of small predators: new thorny lacewings from mid-Cretaceous amber from northern Myanmar (Neuroptera: Rhachiberothidae: Paraberothinae) – CORRIGENDUM Geological Mag. (IF 2.365) Pub Date : 2020-10-20 Hiroshi Nakamine; Shûhei Yamamoto; Yui Takahashi
Thorny lacewings (Rhachiberothidae) are currently distributed only within Africa, whereas they are prevalent in the fossil record of various Cretaceous ambers across the Northern Hemisphere, with a handful of the fossil records from some Eocene European ambers. Four rhachiberothid species in four extinct genera are known from the mid-Cretaceous amber of northern Myanmar. Here, we report further examples
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Quantitative author inputs to Earth science research publications: survey results, insights and potential applications Geological Mag. (IF 2.365) Pub Date : 2020-10-20 Jason R. Ali
Results are reported of what is believed to be the first survey of the quantitative contributions Earth scientists make to their research publications. Based on a return of 26 (from 45; 254 total documents), two key patterns are observed. For most articles, there is a steady decrease in the roles of the first through fifth authors. The former fall from 65 ± 14% for two-author outputs, to 52 ± 9% for
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A new ammonite from the Penarth Group, South Wales and the base of the Jurassic System in SW Britain Geological Mag. (IF 2.365) Pub Date : 2020-10-16 Peter Hodges
Two ammonites have been found in porcelaneous limestones of the White Lias Formation traditionally considered to be of Rhaetian (Late Triassic) age at Lavernock Point, south Wales (ST 181 681). These ammonites, named here Neophyllites lavernockensis. sp. nov, are the earliest recorded from the UK. This horizon is located directly above a major negative δ13C isotope anomaly (CIE1) in the Upper Cotham
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Depositional processes and environmental settings in rock shelters: the case of the prehistoric Oscurusciuto site (Southern Italy) Geological Mag. (IF 2.365) Pub Date : 2020-10-15 Ivan Martini; Andrea Baucon; Francesco Boschin
Clastic successions in rock shelters commonly host important archaeological findings, especially of prehistoric and protostoric times. The understanding of depositional and post-depositional processes in these environments is crucial to understand the lifestyle settings of humans, as well as the reliability of archaeological data obtained during excavations. Rock shelters are genetically related to
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Formation, diagenesis and fauna of cold seep carbonates from the Miocene Taishu Group of Tsushima (Japan) Geological Mag. (IF 2.365) Pub Date : 2020-10-14 Krzysztof Hryniewicz; Yusuke Miyajima; Kazutaka Amano; Magdalena N Georgieva; Michał Jakubowicz; Robert G Jenkins; Andrzej Kaim
The studied seep carbonates from Tsushima, Japan, are embedded within marine siliciclastics of the lower Miocene Taishu Group and represent the earliest evidence of hydrocarbon seepage in the Sea of Japan. In contrast to Miocene and Pliocene examples from Honshu, which are often found above anticlines, the seeps from Tsushima formed within a pull-apart basin before major anticlines had formed. The
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Genesis of high-Ni olivine phenocrysts of the Dali picrites in the Central Emeishan large igneous province Geological Mag. (IF 2.365) Pub Date : 2020-10-14 Wen-Chang Cai; Zhao-Chong Zhang; Jiang Zhu; M. Santosh; Rong-Hao Pan
The Emeishan large igneous province (ELIP) in SW China is considered to be a typical mantle-plume-derived LIP. The picrites formed at relatively high temperatures in the ELIP, providing one of the important lines of argument for the role of mantle plume. Here we report trace-element data on olivine phenocrysts in the Dali picrites from the ELIP. The olivines are Ni-rich, and characterized by high (>1
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Reply to ‘Uppermost Cambrian carbon chemostratigraphy: the HERB and undocumented TOCE events are not synonymous’ Geological Mag. (IF 2.365) Pub Date : 2020-10-12 Maoyan Zhu; Loren E. Babcock; Shanchi Peng; Per Ahlberg
In a recent communication on carbon isotope chemostratigraphy of the uppermost Cambrian strata, it was claimed that the Top of Cambrian Excursion (TOCE) is (1) an undocumented negative δ13Ccarb excursion; (2) ambiguously defined; (3) deliberately fictitious or, in the authors’ words, a ‘nihilartikel’; and (4) not synonymous with the Hellnmaria–Red Tops Boundary (HERB) Event. As the authors who have
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The granite porphyry hidden in the Shuangjianzishan deposit, southern Great Xing’an Range, NE China: geochronology, isotope geochemistry and tectonic implications Geological Mag. (IF 2.365) Pub Date : 2020-10-08 Wei Wei; Xin-Biao Lv; Xiang-Dong Wang
The Shuangjianzishan vein-type Ag-Pb-Zn deposit in the southern Great Xing’an Range (GXR), NE China, is hosted in the slate of the Lower Permian Dashizhai Formation intruded by granite porphyry. In this paper, U–Pb zircon ages and bulk-rock and isotope (Sr, Nd, Pb and Hf) compositions are reported to investigate the derivation, evolution and geodynamic setting of this granite porphyry. It is closely
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Late Jurassic – earliest Cretaceous prolonged shelf dysoxic–anoxic event and its possible causes Geological Mag. (IF 2.365) Pub Date : 2020-08-19 MA Rogov; EV Shchepetova; VA Zakharov
The Late Jurassic – earliest Cretaceous time interval was characterized by a widespread distribution of dysoxiс–anoxiс environments in temperate- and high-latitude epicontinental seas, which could be defined as a shelf dysoxic–anoxic event (SDAE). In contrast to black shales related to oceanic anoxic events, deposits generated by the SDAE were especially common in shelf sites in the Northern Hemisphere
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Occurrence of the eudemersal radiodont Cambroraster in the early Cambrian Chengjiang Lagerstätte and the diversity of hurdiid ecomorphotypes – ERRATUM Geological Mag. (IF 2.365) Pub Date : 2020-10-02 Yu Liu; Rudy Lerosey-Aubril; Denis Audo; Dayou Zhai; Huijuan Mai; Javier Ortega-Hernández
Radiodonts are a diverse clade of Lower Palaeozoic stem-group euarthropods that played a key role in the emergence of complex marine trophic webs. The latest addition to the group, Cambroraster falcatus, was recently described from the Wuliuan Burgess Shale, and is characterized by a unique horseshoe-shaped central carapace element. Here we report the discovery of Cambroraster sp. nov. A, a new species
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Geochemical and metamorphic record of the amphibolites from the Tuting–Tidding Suture Zone ophiolites, Eastern Himalaya, India: implications for the presence of a dismembered metamorphic sole Geological Mag. (IF 2.365) Pub Date : 2020-09-29 Amrita Dutt; A Krishnakanta Singh; Rajesh K Srivastava; Govind Oinam; RK Bikramaditya
The Tuting–Tidding Suture Zone (TTSZ), exposed along Dibang and Lohit river valleys in Arunachal Himalaya, NE India, is the easternmost continuation of the Indus–Tsangpo Suture Zone (ITSZ) and consists of ophiolites associated with metabasics and carbonates. Amphibolites, existing at the base of the ophiolite complex, were studied using whole-rock, mineral chemical analyses and pressure–temperature
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Middle–Late Triassic evolution of the Jameson Land Basin, East Greenland Geological Mag. (IF 2.365) Pub Date : 2020-09-29 Steven D. Andrews; Andrew Morton; Audrey Decou
The Jameson Land Basin lies within the Greenland–Norway rift, to the south of Triassic basins on the Halten Bank and East Greenland shelf, and can therefore offer insights into the development of these less-well-documented offshore basins and the wider North Atlantic. This study focuses on the stratigraphic development of the Jameson Land Basin. Broad-scale stratigraphic logging is augmented with heavy
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Revisiting the tectonic evolution of the Triassic Palaeo-Tethys convergence zone in northern Thailand inferred from detrital zircon U–Pb ages Geological Mag. (IF 2.365) Pub Date : 2020-09-25 Hidetoshi Hara; Tetsuya Tokiwa; Toshiyuki Kurihara; Thasinee Charoentitirat; Apsorn Sardsud
Detrital zircon U–Pb ages for sediments in and around the Palaeo-Tethyan convergence zone in northern Thailand provide constraints for tectonic interpretations of the Indochina Block, the Sibumasu Block, the Inthanon Zone accretionary complex and the Nan Back-arc Basin during the Triassic. In sedimentary rocks of the Indochina Block, almost all of the Palaeozoic and Triassic zircons were sourced from
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Palaeobiology of the reclining rangeomorph Beothukis from the Ediacaran Mistaken Point Formation of southeastern Newfoundland Geological Mag. (IF 2.365) Pub Date : 2020-09-24 Duncan McIlroy; Jessica Hawco; Christopher McKean; Robert Nicholls; Giovanni Pasinetti; Rod Taylor
Beothukis mistakensis from the Ediacaran System of Newfoundland, Canada demonstrates complex fractal-like morphology through the development of primary-, secondary- and tertiary-order Rangea-like units. The primary-order rangeomorph units observed in B. mistakensis are tightly juxtaposed, show no evidence of being independent of one another and are made up of chamber-like secondary-order – probably
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Cerro del Hierro, Spain: the largest exposed early Cambrian palaeokarst Geological Mag. (IF 2.365) Pub Date : 2020-09-22 Eduardo Mayoral; María Eugenia Dies Álvarez; José Antonio Gámez Vintaned; Rodolfo Gozalo; Eladio Liñán; José Miguel Molina
We study the largest exposed example of an early Cambrian palaeokarst, associated with laterites and developed during rifting of the Ossa–Morena Zone. The lithostratigraphy, biostratigraphy, facies and the genesis reflect episodes of sea-level fall (Cerro del Hierro Regression) related to tectonic events and palaeoclimate. This palaeokarst can be primarily considered as the result of early Cambrian
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The Kamusite A2-type granites in the Karamaili tectonic belt, Xinjiang (NW China): tracing staged postcollisional delamination in the eastern Junggar Geological Mag. (IF 2.365) Pub Date : 2020-09-22 Bowen Zhang; Chuan Chen; Xiaoping Gong; Yaxiaer Yalikun; Kadeliya Kaheman
The Kamusite pluton is located in the eastern Junggar area, the westernmost segment of the Karamaili structural belt, and is predominantly composed of medium granite and microgranite with an exposure area of 30 km2. The U–Pb zircon geochronology of the Kamusite granites indicates that they crystallized in the late Carboniferous period (328–321 Ma). These granites exhibit high contents of SiO2 (76.09–77
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Detrital zircon U–Pb–Hf isotopes for the Permo-Carboniferous sediments in the northern Alxa area, NW China: provenance and tectonic implications for the middle segment of the Central Asian Orogenic Belt Geological Mag. (IF 2.365) Pub Date : 2020-09-14 Yan Chen; Tairan Wu; Zhicheng Zhang
The northern Alxa orogenic belt, located in the middle segment of the Central Asian Orogenic Belt, is a junction between the North China Craton, Tarim Craton and Mongolian microcontinents. However, its Permo-Carboniferous tectono-palaeogeographic evolution has not been well established. In this study, new zircon U–Pb–Hf isotopic data for the Permo-Carboniferous clastic rocks were used to address the
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40Ar/39Ar age constraints for an early Alpine metamorphism of the Sakar unit, Sakar–Strandzha zone, Bulgaria Geological Mag. (IF 2.365) Pub Date : 2020-09-14 Nikolay Bonev; Richard Spikings; Robert Moritz
We investigated the Sakar unit metamorphic rocks of the Sakar–Strandzha zone in Bulgaria, using 40Ar/39Ar dating of amphibole from the polymetamorphic basement and white mica in the overlying upper Permian metasedimentary rocks of the Paleokastro Formation. The amphibole and white mica revealed plateau ages of 140.50 ± 1.75 Ma and 126.19 ± 1.29 Ma, respectively, indicating an Early Cretaceous cooling
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Neoproterozoic active margin in the northwestern Yangtze Block, South China: new clues from detrital zircon U–Pb geochronology and geochemistry of sedimentary rocks from the Hengdan Group Geological Mag. (IF 2.365) Pub Date : 2020-09-10 Bo Hui; Yunpeng Dong; Feifei Zhang; Shengsi Sun; Shuai He
The Yangtze Block in South China constitutes an important Precambrian landmass in the present East Asian continent. The Neoproterozoic sedimentary successions of the Hengdan Group in the NW Yangtze Block record essential information for deciphering the Neoproterozoic tectonics along the NW margin. However, its depositional age, provenance and tectonic properties remain uncertain. Here, a combined analysis
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Late Mississippian limestone sedimentary environment in southern Pembrokeshire (Bullslaughter Bay, Wales): evidence of meteoric diagenesis and hypersaline features Geological Mag. (IF 2.365) Pub Date : 2020-09-09 Yvonne Battiau-Queney; Alain Préat; Alain Trentesaux; Philippe Recourt; Viviane Bout-Roumazeilles
Bullslaughter Bay in southern Pembrokeshire, UK, exposes sections of Upper Mississippian limestone strata. In many places, the rock suffered an isovolumetric alteration during a period of sea-level oscillations. We used multiple approaches to study the weathered rocks, combining sedimentological, petrographic and isotopic compositions (δ18O and δ13C values). Two main microfacies are recognized: (i)
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The response of water column and sedimentary environments to the advent of the Messinian salinity crisis: insights from an onshore deep-water section (Govone, NW Italy) Geological Mag. (IF 2.365) Pub Date : 2020-09-07 Mathia Sabino; Francesco Dela Pierre; Marcello Natalicchio; Daniel Birgel; Susanne Gier; Jörn Peckmann
During Messinian time, the Mediterranean underwent hydrological modifications culminating 5.97 Ma ago with the Messinian salinity crisis (MSC). Evaporite deposition and alleged annihilation of most marine eukaryotes were taken as evidence of the establishment of basin-wide hypersalinity followed by desiccation. However, the palaeoenvironmental conditions during the MSC are still a matter of debate
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In situ rare earth element analysis of a lower Cambrian phosphate nodule by LA-ICP-MS Geological Mag. (IF 2.365) Pub Date : 2020-09-04 Yun-Tao Ye; Hua-Jian Wang; Xiao-Mei Wang; Li-Na Zhai; Chao-Dong Wu; Shui-Chang Zhang
Rare earth elements (REE) in marine minerals have been widely used as proxies for the redox status of depositional and/or diagenetic environments. Phosphate nodules, which are thought to grow within decimetres below the sediment–water interface and to be able to scavenge REE from the ambient pore water, are potential archives of subtle changes in REE compositions. Whether their REE signals represent
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U–Pb detrital zircon ages from Gorgoglione Flysch sandstones in Southern Apennines (Italy) as provenance indicators Geological Mag. (IF 2.365) Pub Date : 2020-09-04 Annamaria Fornelli; Salvatore Gallicchio; Francesca Micheletti; Antonio Langone
Twenty-one sandstone samples belonging to the intermediate part of Gorgoglione Flysch (GF) dated Middle-Miocene, cropping out in the Southern Apennines (Italy), have been studied to highlight the detritus provenance. Petrographic and chemical composition indicates that the successions consist of feldspatho-quartzose and litho-feldspatho-quartzose arenites interbedded with pelitic and calciclastic layers
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A fossil dreamer of the genus Oneirodes (Lophiiformes: Ceratioidei) from the Miocene of Sakhalin Island, Russia Geological Mag. (IF 2.365) Pub Date : 2020-06-22 Mikhail V. Nazarkin; Theodore W. Pietsch
The almost complete skeleton of a fossil dreamer, identified as Oneirodes sp., is described from the middle–upper Miocene Kurasi Formation of southern Sakhalin Island, Russia. This is the second fossil skeletal record of oneirodid anglerfishes following those described from the Puente Formation of California, USA. The new specimen possesses morphological features very similar to those of the recent
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Forsterite reprecipitation and carbon dioxide entrapment in the lithospheric mantle during its interaction with carbonatitic melt: a case study from the Sung Valley ultramafic–alkaline–carbonatite complex, Meghalaya, NE India Geological Mag. (IF 2.365) Pub Date : 2020-08-20 Shubham Choudhary; Koushik Sen; Santosh Kumar; Shruti Rana; Swakangkha Ghosh
Carbonatite melts derived from the mantle are enriched in CO2- and H2O-bearing fluids. This melt can metasomatize the peridotitic lithosphere and liberate a considerable amount of CO2. Experimental studies have also shown that a CO2–H2O-rich fluid can form Fe- and Mg-rich carbonate by reacting with olivine. The Sung Valley carbonatite of NE India is related to the Kerguelen plume and is characterized
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Influence of differential structural deformation on shale reservoirs: a case study of the lower Silurian Longmaxi Shale in north Guizhou, Southern China Geological Mag. (IF 2.365) Pub Date : 2020-08-20 Yang Gu; Jianhua He; Sheng Xu; Qianning Tian; Wei Zhang; Shuai Yin
Southern China is affected by multi-stage tectonic activities, with strong fold deformation, complex fault systems and poor shale gas preservation conditions. Here, we used shale samples from the lower Silurian Longmaxi shale in the complex tectonic area of Southern China, to study the relationship between differential structural deformation, and pore structure and adsorption capacity. According to
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Petrogenesis of the post-collisional porphyritic granitoids from Jhalida, Chhotanagpur Gneissic Complex, eastern India Geological Mag. (IF 2.365) Pub Date : 2020-08-20 Poulami Roy; Bapi Goswami; Sukanya Dutta; Chittaranjan Bhattacharyya
The Jhalida porphyritic granitoid pluton is exposed in a regional shear zone belonging to the Chhotanagpur Gneissic Complex of the Satpura Orogen (c. 1.0 Ga), regarded as the collisional suture between the South and North Indian blocks. The pluton intruded the migmatitic gneisses, metapelites, calc-silicate rocks and amphibolites belonging to the amphibolite facies. The mineral assemblage indicates
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The Central Sudetic Ophiolite (European Variscan Belt): precise U–Pb zircon dating and geotectonic implications Geological Mag. (IF 2.365) Pub Date : 2020-08-19 Marek Awdankiewicz; Ryszard Kryza; Krzysztof Turniak; Maria Ovtcharova; Urs Schaltegger
Precise U–Pb zircon dating using the chemical abrasion – isotope dilution – thermal ionization mass spectrometry (CA-ID-TIMS) method constrains the age of the Central Sudetic Ophiolite (CSO) in the Variscan Belt of Europe. A felsic gabbro from the Ślęża Massif contains zircon xenocrysts dated at 404.8 ± 0.3 Ma and younger crystals dated at 402.6 ± 0.2 Ma that determine the final crystallization age
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Geochemistry and zircon ages of the Yushigou diabase in the Longshoushan area, Alxa Block: implications for crust–mantle interaction and tectonic evolution Geological Mag. (IF 2.365) Pub Date : 2020-08-19 Ren-Yu Zeng; Jian-Qing Lai; Xian-Cheng Mao; Jie Yan; Chen-Guang Zhang; Wen-Zhou Xiao
The North Qilian orogenic belt in North China has been defined as a subduction–collision zone between the Alxa Block and the Qilian Block. We present petrography, zircon U–Pb geochronology, major- and trace-element geochemistry, and Sr–Nd–Pb–Hf isotope analysis for the Yushigou diabase from the Longshoushan area, which is located SW of the Alxa Block, aiming to understand its petrogenetic link to subduction
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Nd isotope composition of the Ediacaran and earliest Cambrian phosphorite nodules and Fe sulphide from the East European Platform Geological Mag. (IF 2.365) Pub Date : 2020-08-19 Sergey B Felitsyn; Eugeny S. Bogomolov
An enhanced concentration of phosphorus has been found at the stratigraphic level of the disappearance of Ediacaran taxa in two areas, the Cis-Dniester region and the Moscow syneclise, on the East European Platform (EEP). The isotope composition of neodymium was determined in Fe sulphide and phosphorite in the same beds. Measured ε Nd(t) values in diagenetic phosphate nodules are similar to those in
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Thermal maturation of a complete magmatic plumbing system at the Sierra de Velasco, Northwestern Argentina Geological Mag. (IF 2.365) Pub Date : 2020-08-14 Marcos Macchioli Grande; Pablo Alasino; Juan Dahlquist; Matías Morales Cámera; Carmen Galindo; Miguel Basei
The formation of magmatic plumbing systems in the crust involves mass and heat transfer from deep to shallow levels. This process modifies the local geotherm and increases the thermal maturation of the crust, affecting the rheological state of the host rock and the composition of magma. Here, we report a petrological, geochemical, isotopic and geochronological integrated study of the Huaco (~354 Ma)
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Active deformation and Plio-Pleistocene fluvial reorganization of the western Kura fold–thrust belt, Georgia: implications for the evolution of the Greater Caucasus Mountains Geological Mag. (IF 2.365) Pub Date : 2020-08-13 Lasha Sukhishvili; Adam M. Forte; Giorgi Merebashvili; Joel Leonard; Kelin X. Whipple; Zurab Javakhishvili; Arjun Heimsath; Tea Godoladze
Since Plio-Pleistocene time, southward migration of shortening in the eastern part of the Greater Caucasus into the Kura foreland basin has progressively formed the Kura fold–thrust belt and Alazani piggyback basin, which separates the Kura fold–thrust belt from the Greater Caucasus. Previous work argued for an eastward propagation of the Kura fold–thrust belt, but this hypothesis was based on coarse
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Petrogenesis of a rare Ediacaran tonalite–trondhjemite–granodiorite suite, Egypt, and implications for Neoproterozoic Gondwana assembly Geological Mag. (IF 2.365) Pub Date : 2020-08-13 Abdel-Fattah M Abdel-Rahman
Most tonalite–trondhjemite–granodiorite (TTG) suites are Archean–Palaeoproterozoic in age, but those of Neoproterozoic–Phanerozoic age are scarce. A rare Ediacaran high-Al TTG suite has been identified at the Fannani Igneous Complex (FIC) in the northern Arabian–Nubian Shield, which is essentially composed of amalgamated Neoproterozoic island-arc Pan-African composite terranes that contain several
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Protracted late Neoproterozic – early Palaeozoic deformation and cooling history of Sør Rondane, East Antarctica, from 40Ar/39Ar and U–Pb geochronology Geological Mag. (IF 2.365) Pub Date : 2020-08-04 Antonia S Ruppel; Joachim Jacobs; Andreas Läufer; Lothar Ratschbacher; Jörg A Pfänder; Benita-Lisette Sonntag; Katarzyna Krasniqi; Marlina Elburg; Nicole Krohne; Detlef Damaske; Frank Lisker
40Ar/39Ar and U–Pb data from five structural domains constrain the late Neoproterozoic – early Palaeozoic tectonothermal history of the eastern part of the East African–Antarctic Orogen in Sør Rondane. A total of 27 new Ar/Ar ages span 570–474 Ma, roughly corresponding to the age range of three generations of syn- to post-tectonic granitoids. The ages are distinct for the five structural domains. The
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