Journal articles on the topic 'Late Neoproterozoic'
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VIZAN, HAROLDO, JOHN N. CARNEY, PETER TURNER, ROBERT A. IXER, MARK TOMASSO, ROBERT P. MULLEN, and PAUL CLARKE. "Late Neoproterozoic to Early Palaeozoic palaeogeography of Avalonia: some palaeomagnetic constraints from Nuneaton, central England." Geological Magazine 140, no. 6 (November 2003): 685–705. http://dx.doi.org/10.1017/s001675680300832x.
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Palaeomagnetic studies have been carried out on Neoproterozoic, Cambrian and Ordovician rocks in the Nuneaton inlier, England (52.5° N, 1.5° W). Three magnetic components were recognized, which provide a consistent structural and magnetic history of the inlier. Neoproterozoic volcaniclastic and intrusive rocks acquired a characteristic remanent magnetization (ChRM) dated at 603Ma. Late Ordovician rocks are represented by lamprophyre and diorite intrusions and their ChRMs were probably imprinted during their emplacement, at about 442 Ma. The Lower Cambrian sedimentary sequence of the Hartshill Sandstone Formation, which unconformably overlies the Neoproterozoic rocks and hosts the Ordovician intrusions, does not preserve a primary magnetization but shows the imprints of the Late Ordovician (442 Ma) remagnetization, as well as a probable end-Carboniferous remagnetization. Palaeolatitudes calculated for the late Neoproterozoic rocks and Ordovician intrusions are in good agreement with other palaeolatitudes calculated for Avalonia during those times. Both the late Neoproterozoic and Late Ordovician rocks additionally show ChRMs with declination anomalies indicating a large tectonic rotation of the Nuneaton area, possibly during one of the Caledonian phases of deformation affecting southern Britain.
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Yarmolyuk, V. V., and K. E. Degtyarev. "Precambrian terrains of Central Asian orogenic belt: comparative characteristics, types and peculiarities of the tectonic evolution." Геотектоника, no. 1 (April 1, 2019): 3–43. http://dx.doi.org/10.31857/s0016-853x201913-43.
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The structure and peculiarities of the tectonic evolution of Precambrian terraines included into the structure of Paleozoids in different parts of the Central Asian orogenic belt are reviewed, types and comparative characteristics of Precambrian terraines are provided. We throw light on two types of Precambrian terrains structure: essentially juvenile Neoproterozoic crust (1); Mezo- and Early Neoproterozoic crust formed due to reworking of Early Precambrian formations (2). Terrains with juvenile Neoproterozioc crust, located in the Central and Eastern parts of the Central Asian orogenic belt, were generated in the oceanic sector of the Earth. Their formation was connected to the Early- and Late Neoproterozoic cycles of tectogenesis up to 200 Ma each cycle. Terrains with Mezo- and Early Neoproterozoic crust, found mainly in the West of the Central Asian orogenic belt, generated in the continental sector of the Earth during the Neoproterozoic, their evolution occurred mainly in the intracontinental environments. In the evolution all of considered terrains in the interval 800–700 Ma, an event associated with rift zones formation and intraplate magmatism was revealed, it coincided with the supercontinent Rodinia split. The conducted research allow to connect formation history of the Precambrian terrains of the Central Asian orogenic belt with the processes took place in the edge of the Syberia-Tarim part of the supercontinent Rodinia and the adjacent sector of the paleo-ocean.
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Rudnev, S. N., O. M. Turkina, V. G. Mal’kovets, E. A. Belousova, P. A. Serov, and V. Yu Kiseleva. "Intrusive Complexes of the Late Neoproterozoic Island Arc Structure of the Lake Zone (Mongolia): Isotope Systematics and Sources of Melts." Russian Geology and Geophysics 63, no. 1 (January 1, 2022): 23–38. http://dx.doi.org/10.2113/rgg20204252.
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Abstract –We present data on the geochemical and Sr–Nd isotope compositions of rocks and on the Lu–Hf isotope composition of magmatic and xenogenic zircons from granitoids and gabbroids of the late Neoproterozoic island arc structure of the Lake Zone. Plagiogranitoids, gabbroids, and quartz diorites (559–542 Ma) formed at the late Neoproterozoic subduction stage of magmatism, and two-feldspathic granites (~483 Ma) mark Cambrian–Ordovician accretion–collision processes. We have established that the volcanic rocks of the late Neoproterozoic island arc and/or its oceanic base, which formed from the depleted mantle, were the mafic source of plagiogranitoids. This is proved by the overlapping positive εNd values of plagiogranitoids and the host volcanic rocks and by the commensurate εHf values of magmatic zircons from the plagiogranitoids and depleted mantle. The lower εNd values of gabbro and quartz diorites from the Tavan Hayrhan and Shuthuyn plutons, the lower εHf values of zircons from these rocks, and the high (87Sr/86Sr)0 ratios and K2O, Rb, and Th contents point to the generation of these rocks from a less depleted mantle source, namely, mantle wedge peridotites. The isotope composition of the latter changed at the previous subduction stage under the impact of fluids and with the contribution of subducted sediments. The least radiogenic Hf isotope composition of magmatic and xenogenic zircons from Ordovician accretion–collisional two-feldspathic granites of the Ih Zamiin pluton suggests their formation through the melting of the late Neoproterozoic–Cambrian island arc crust with the contribution of more differentiated crustal sources enriched in Th, Nb, and LREE and characterized by low εNd values. The age of xenogenic zircons (≤716 Ma) in the studied granitoids and gabbroids and their similarity in Hf isotope composition to magmatic zircons from the same rocks confirm the formation of the late Neoproterozoic island arc of the Lake Zone in an intraoceanic setting far from ancient continental sources similar to the Dzavhan microcontinent.
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Powell, C. McA, and S. A. Pisarevsky. "Late Neoproterozoic assembly of East Gondwana." Geology 30, no. 1 (2002): 3. http://dx.doi.org/10.1130/0091-7613(2002)030<0003:lnaoeg>2.0.co;2.
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WU, LONG, DONG JIA, HAIBIN LI, FEI DENG, and YIQUAN LI. "Provenance of detrital zircons from the late Neoproterozoic to Ordovician sandstones of South China: implications for its continental affinity." Geological Magazine 147, no. 6 (September 7, 2010): 974–80. http://dx.doi.org/10.1017/s0016756810000725.
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AbstractThe U–Pb geochronology of 687 detrital zircons from the voluminous Upper Neoproterozoic–Ordovician succession in the Wuyishan Fold Belt of South China reveals a common dominant c. 1200–950 Ma group, indicative of an outboard provenance terrane with a Grenville-age province to the southeast during the late Neoproterozoic–Early Palaeozoic. Compared with coeval samples from the Gondwanan and eastern Laurentian margins, our data show a scarcity of distinctive Gondwanan provenances (c. 650–500 Ma) and reveal some Laurentian signatures. These results argue against the peri-Gondwanan setting for South China during the late Neoproterozoic–Ordovician, instead implying a Laurentian affinity.
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Lipps, Jere H., and James W. Valentine. "Late Neoproterozoic Metazoa: Weird, Wonderful and Ghostly." Paleontological Society Papers 10 (November 2004): 51–66. http://dx.doi.org/10.1017/s1089332600002333.
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The Late Neoproterozoic or Ediacaran biota contains a variety of enigmatic fossils of uncertain, but likely metazoan, affinities. The protistan group Choanoflagellata and Metazoa share a common ancestor predating the first fossils by perhaps 100's of millions of years. Sponge choanocytes closely resemble choanoflagellates, establishing a morphologic similarity as well. Fossils in the late Neoproterozoic may represent stem or early groups of cnidarians, while others resemble eumetazoans and bilaterians. These organisms occurred on all continents except Antarctica, and occupied four major habitats from prodeltaic to deep slope environments in each area. Their paleoecology was complex but similar to modern soft-bodied slope organisms. Ediacaran trophic structures were complex as well and included a wide variety of feeding types from detritovores, herbivores on microbial mats, filter-feeders, and predators. Ediacaran assemblages thus constitute the evolutionary and ecological precursors of later Phanerozoic and modern biotas.
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Grazhdankin, D. "Late Neoproterozoic sedimentation in the Timan foreland." Geological Society, London, Memoirs 30, no. 1 (2004): 37–46. http://dx.doi.org/10.1144/gsl.mem.2004.030.01.04.
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Pisarevsky, S. A., and C. McA Powell. "The Late Neoproterozoic Assembly of East Gondwanaland." Gondwana Research 4, no. 4 (October 2001): 735–36. http://dx.doi.org/10.1016/s1342-937x(05)70527-x.
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NAZIR, Nusrat, Liu YANG, and Zhang CHENGJUN. "Tectonic evolution of the Qinling Orogenic Belt, Central China – new evidence from geochemical, zircon (U-pb) geochronology and HF isotopes." Nova Geodesia 2, no. 3 (September 30, 2022): 54. http://dx.doi.org/10.55779/ng2354.
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The paper deals with a review of tectonic evolution in different regions of China with the help of different techniques and models. Tectonic evolution shows that in the shallow layers of China the structural impact is not solid, and huge structural zones are deficient within the list and incline zones where the principal wretchedness and delicate slant zones framed. The Qinling Orogenic Belt (QOB) situated between the North China Craton (NCC) and the Yangtze Craton (YZC) is made from the Northern Qinling Belt (NQB) and the Southern Qinling Belt (SQB). The Hf isotopic creations of zircons from the different rocks recommend that the NQB most likely created on the cellar of the southern NCC. The stones in the SQB show zircon age spectra and Hf-isotope structures like those in the northern YZC, recommending a nearby proclivity. We thusly decipher the SQB to have created on the cellar of the northern YZC. Incorporating the new information in this investigation with those from past works, we propose another structural model for the development and advancement of the QOB during late Mesoproterozoic to early Paleozoic including the accompanying significant occasions: (1) Late Mesoproterozoic to early Neoproterozoic (Grenvillian) toward the north subduction of the Songshugou Ocean; Early-center Neoproterozoic (870-800 Ma) bidirectional subduction and impact; Middle Neoproterozoic (∼800-710 Ma) post-crash expansion; Middle-late Neoproterozoic (710-600 Ma) inside plate augmentation; Late Neoproterozoic-early Paleozoic (600-520 Ma) opening of the Shangdan Ocean; and Early Paleozoic (520-420 Ma) subduction-crash. We accordingly follow in any event two unmistakable Wilson cycles in the QOB.
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Khanchuk, A. I., A. A. Alenicheva, V. V. Golozubov, A. T. Kandaurov, Y. Y. Yurchenko, and S. A. Sergeev. "THE KHANKA MASSIF: HETEROGENEITY OF ITS BASEMENT AND REGIONAL CORRELATIONS." Tikhookeanskaya Geologiya 41, no. 4 (2022): 3–22. http://dx.doi.org/10.30911/0207-4028-2022-41-4-3-22.
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The results of geochronology studies on metagranitoids (U-Pb SIMS) and ophiolites (Sm-Nb) from the Khanka massif are considered. New and published data define the Early Neoproterozoic Matveevka-Nakhimov terrane with early suprasubduction magmatism of 935 and 915 Ma, intraplate and Pacific-type transform margin magmatism of 850-880 and 757 Ma, and the Late Neoproterozoic-Early Cambrian Dvoryan and Tafuin terranes with suprasubduction magmatism of 543, 520, 517 and 513 Ma. Between these two parts of the massif there is a suture (Voznesenka and Spassk terranes) formed by Ediacaran-Cambrian shelf deposits and a Cambrian accretionary prism with ophiolites older than 514 Ma. The greater part of the Khanka massif formed late in the Cambrian with the Kordonka island arc terrane accreted at the end of the Silurian. The Sergeevka terrane of the Ordovician island arc joined it through Early Cretaceous strike-slip movements. Heterogeneous structures of the main part of the Khanka massif can be traced to the north by the analogous stages of magmatism and metamorphism, where the Jiamusi massif (including the East Bureya terrane) is an Early Neoproterozoic block and the eastern Songnen massif (including the West Bureya terrane) is a Late Neoproterozoic-Cambrian block. Between these two blocks is the Spassk-Wuxingzhen-Melgin suture formed by their collision late in the Cambrian. The Bureya-Songnen-Jiamusi-Khanka superterrane formed as a part of the Gondwana supercontinent about 500 Ma ago through orogeny and accretion of the Rodinia supercontinent fragments.
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PRAVE, A. R. "The Neoproterozoic Dalradian Supergroup of Scotland: an alternative hypothesis." Geological Magazine 136, no. 6 (November 1999): 609–17. http://dx.doi.org/10.1017/s0016756899003155.
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The Dalradian Supergroup is interpreted traditionally as recording c. 300 m.y. of ‘episodic’ Neoproterozoic rifting. However, lower Dalradian (pre-Easdale Subgroup) facies architecture is incompatible with rift-basin fill, and no unambiguous Neoproterozoic extensional structures are present in those rocks. Consequently, no objective evidence exists to infer that Dalradian sedimentation was initiated during extensional tectonism. That, combined with the accumulating data for contractile deformation in Scotland at c. 870–800 Ma, the Knoydartian orogeny, permits the proposal of an alternative tectonostratigraphic evolution for the Dalradian. I propose that Dalradian basin genesis was initiated as a foredeep in response to Knoydartian orogenesis. The coarsening- and shallowing-upward, 6–8 km-thick Grampian Group–lower Lochaber Subgroup succession arguably represents a flysch to molasse Knoydartian foredeep overlain by a moderately stable post-orogenic shelfal sequence recorded by the relatively uniform thinner (c. 4 km) and compositionally more mature rocks of the upper Lochaber through Islay subgroups. Lithospheric-scale extensional tectonism and rifting did not occur until the late Neoproterozoic, as marked by the laterally variable, volcanic- and igneous-bearing Easdale Subgroup, and was followed by the late Neoproterozoic–early Palaeozoic Iapetan rift-to-drift transition through the Southern Highland Group.
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SANTOSH, M., A. S. COLLINS, T. MORIMOTO, and K. YOKOYAMA. "Depositional constraints and age of metamorphism in southern India: U–Pb chemical (EMPA) and isotopic (SIMS) ages from the Trivandrum Block." Geological Magazine 142, no. 3 (May 2005): 255–68. http://dx.doi.org/10.1017/s0016756805000506.
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We report U–Pb electron microprobe (zircon and monazite) and Secondary Ion Mass Spectrometry (SIMS) U–Pb (zircon) ages from a granulite-facies metapelite and a garnet–biotite gniess from Chittikara, a classic locality within the Trivandrum Block of southern India. The majority of the electron-microprobe data on zircons from the metapelite define apparent ages between 1500 and 2500 Ma with a prominent peak at 2109±22 Ma, although some of the cores are as old as 3070 Ma. Zircon grains with multiple age zoning are also detected with 2500–3700 Ma cores, 1380–1520 mantles and 530–600 Ma outer rims. Some homogeneous and rounded zircon cores yielded late Neoproterozoic ages that suggest that deposition within the Trivandrum Block belt was younger than 610 Ma. The outermost rims of these grains are characterized by early Cambrian ages suggesting metamorphic overgrowth at this time. The apparent ages of monazite grains from this locality reveal multiple provenance and polyphase metamorphic history, similar to those of the zircons. In a typical case, Palaeoproterozoic cores (1759–1967 Ma) are enveloped by late Neoproterozoic rims (562–563 Ma), which in turn are mantled by an outermost thin Cambrian rim (∼515 Ma). PbO v. ThO*2 plots for monazites define broad isochrons, with cores indicating a rather imprecise age of 1913±260 Ma (MSWD=0.80) and late Neoproterozoic/Cambrian cores as well as thin rims yielding a well-defined isochron with an age of 557±19 Ma (MSWD=0.82). SIMS U–Pb isotopic data on zircons from the garnet–biotite gneiss yield a combined core/rim imprecise discordia line between 2106±37 Ma and 524±150 Ma. The data indicate Palaeoproterozoic zircon formation with later partial or non-uniform Pb loss during the late Neoproterozoic/Cambrian tectonothermal event. The combined electron probe and SIMS data from the metapelite and garnet–biotite gneiss at Chittikara indicate that the older zircons preserved in the finer-grained metapelite protolith have heterogeneous detrital sources, whereas the more arenaceous protolith of the garnet–biotite gniess was sourced from a single-aged terrane. Our data suggest that the metasedimentary belts in southern India may have formed part of an extensive late Neoproterozoic sedimentary basin during the final amalgamation of the Gondwana supercontinent.
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Kozlov, P. S., I. I. Likhanov, K. S. Ivanov, A. D. Nozhkin, and S. V. Zinoviev. "New data on age of the Neoproterozoic volcanic rocks of Isakovka Terrain from the Sayan-Yenisei accretion belt (U-Pb, zircon)." Доклады Академии наук 488, no. 5 (October 20, 2019): 521–25. http://dx.doi.org/10.31857/s0869-56524885521-525.
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The Late Neoproterozoic U-Pb age for zircon of island-arc metadacites (691 8.8 million years) and basalts (572 6.5 million years) of the Kiselikhinskaya Formation of the Kutukasskaya Group was established for the first time. The manifestation of basaltic volcanism is associated with rift-related processes. The studies clarify the Late Precambrian stratigraphy of the Yenisei Ridge and the features of the evolution of the Sayan-Yenisei accretionary belt at the Neoproterozoic stage of its history. Folded-thrust structures of the junction zone of the Yenisei Ridge with the West Siberian Plate may be favorable in relation to the search for unconventional oil and gas traps.
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MAJKA, JAROSŁAW, YARON BE’ERI-SHLEVIN, DAVID G. GEE, JERZY CZERNY, DIRK FREI, and ANNA LADENBERGER. "Torellian (c. 640 Ma) metamorphic overprint of Tonian (c. 950 Ma) basement in the Caledonides of southwestern Svalbard." Geological Magazine 151, no. 4 (November 13, 2013): 732–48. http://dx.doi.org/10.1017/s0016756813000794.
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AbstractIon microprobe dating in Wedel Jarlsberg Land, southwestern Spitsbergen, provides new evidence of early Neoproterozoic (c. 950 Ma) meta-igneous rocks, the Berzeliuseggene Igneous Suite, and late Neoproterozoic (c. 640 Ma) amphibolite-facies metamorphism. The older ages are similar to those obtained previously in northwestern Spitsbergen and Nordaustlandet where they are related to the Tonian age Nordaustlandet Orogeny. The younger ages complement those obtained recently from elsewhere in Wedel Jarlsberg Land of Torellian deformation and metamorphism at 640 Ma. The Berzeliuseggene Igneous Suite occurs in gently N-dipping, top-to-the-S-directed thrust sheets on the eastern and western sides of Antoniabreen where it is tectonically intercalated with younger Neoproterozoic sedimentary formations, suggesting that it provided a lower Tonian basement on which upper Tonian to Cryogenian sediments (Deilegga Group) were deposited. They were deformed together during the Torellian Orogeny, prior to deposition of Ediacaran successions (Sofiebogen Group) and overlying Cambro-Ordovician shelf carbonates, and subsequent Caledonian and Cenozoic deformation. The regional importance of the late Neoproterozoic Torellian Orogeny in Svalbard's Southwestern Province and its correlation in time with the Timanian Orogeny in the northern Urals as well as tectonostratigraphic similarities between the Timanides and Pearya (northwestern Ellesmere Island) favour connection of these terranes prior to the opening of the Iapetus Ocean and Caledonian Orogeny.
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Degtyarev, K. E., A. A. Tretyakov, E. B. Salnikova, and A. B. Kotov. "Kumystin granosyenites complex of the late Cryogenian in Bolshoi Karatau (South Kazakhstan), age substantiation." Доклады Академии наук 484, no. 5 (May 16, 2019): 579–83. http://dx.doi.org/10.31857/s0869-56524845579-583.
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The results of U–Pb geochronological studies of quartz syenites of the Kumystin complex of the Bolshoi Karatau ridge in southern Kazakhstan are presented and their late Neoproterozoic (717 ± 4 Ma) age is substantiated. Kumystin syenites complex together with rhyolites and basalts of the Kainar Formation are the youngest formations taking part in the basement of Karatau-Dzhebagly precambrian massif and formed in the second half of Cryogenian. The data set about the ages of the youngest complexes taking part in the basement of precambrian massifs of the Western part of the Central Asian belt indicates that the ending of magmatic activity within various massifs occurred asynchronously during the Neoproterozoic.
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Luo, Liang, Lianbo Zeng, Kai Wang, Xiaoxia Yu, Yihang Li, Chenxi Zhu, and Shuning Liu. "Provenance investigation for the Cambrian–Ordovician strata from the northern margin of the western Yangtze Block: implications for locating the South China Block in Gondwana." Geological Magazine 157, no. 4 (October 25, 2019): 551–72. http://dx.doi.org/10.1017/s0016756819001110.
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AbstractWe report new U–Pb isotopic data for detrital zircons from Cambrian–Ordovician strata on the northern margin of the western Yangtze Block, which together with published U–Pb isotopic data for coeval strata in the South China Block, provide critical constraints on the provenance of these sediments and further shed light on the early Palaeozoic position of the South China Block in the context of Gondwana. Detrital zircons in this study yield four major age peaks in the early Palaeoproterozoic, early Neoproterozoic, middle Neoproterozoic and late Neoproterozoic – early Palaeozoic. The dominant age population of 900–700 Ma matches well with magmatic ages from the nearby Panxi–Hannan Belt, which indicates that Cambrian–Ordovician sedimentary rocks in the western Yangtze Block were mainly of local derivation. However, compilations of detrital zircon ages for the Cambrian–Ordovician strata from the Cathaysia Block and the eastern Yangtze Block show that both blocks are dominated by late Mesoproterozoic- and early Neoproterozoic-aged detrital zircons, which suggests a remarkable exotic input with typical Gondwana signatures. According to the integrated detrital zircon age spectra of the Cambrian–Ordovician sedimentary rocks from the entire South China Block and palaeocurrent data, the South China Block should have been linked with North India and Western Australia within East Gondwana. Specifically, the Cathaysia Block was located adjacent to Western Australia, while the Yangtze Block was connected with North India.
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Liivamägi, Sirle, Peeter Somelar, William C. Mahaney, Juho Kirs, Ilze Vircava, and Kalle Kirsimäe. "Late Neoproterozoic Baltic paleosol: Intense weathering at high latitude?" Geology 42, no. 4 (April 2014): 323–26. http://dx.doi.org/10.1130/g35209.1.
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Pisarevsky, S. A., J. B. Murphy, P. A. Cawood, and A. S. Collins. "Late Neoproterozoic and Early Cambrian palaeogeography: models and problems." Geological Society, London, Special Publications 294, no. 1 (2008): 9–31. http://dx.doi.org/10.1144/sp294.2.
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Lubnina, Natalia V., Sergei A. Pisarevsky, Victor N. Puchkov, Vjacheslav I. Kozlov, and Nina D. Sergeeva. "New paleomagnetic data from Late Neoproterozoic sedimentary successions in Southern Urals, Russia: implications for the Late Neoproterozoic paleogeography of the Iapetan realm." International Journal of Earth Sciences 103, no. 5 (April 9, 2014): 1317–34. http://dx.doi.org/10.1007/s00531-014-1013-x.
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Hartley, Adrian, Bartosz Kurjanski, Jessica Pugsley, and Joseph Armstrong. "Ice-rafting in lakes in the early Neoproterozoic: dropstones in the Diabaig Formation, Torridon Group, NW Scotland." Scottish Journal of Geology 56, no. 1 (December 18, 2019): 47–53. http://dx.doi.org/10.1144/sjg2019-017.
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A dropstone horizon is described from lake deposits in a palaeo-valley from the c. 1000 Ma Diabaig Formation, Torridon Group, NW Scotland. Dropstones occur in wave-rippled, fine-grained sandstones and siltstones that contain desiccation and syneresis cracks indicative of fluctuating lake levels. Five locally derived dropstones occur at the same horizon over lateral distance of 250 m and display clear evidence of deflection and penetration of laminae at the base, with thinning, onlap and draping of laminae on to clast margins and tops. Mechanisms of dropstone formation are discussed, with ice-rafting considered the most likely explanation. It is suggested that rafting was promoted by cold winters at 35° S in the early Neoproterozoic, possibly in an upland setting. Interpretation of the dropstones as ice-rafted debris provides the first physical record of evidence for ice at the Earth's surface during the late Mesoproterozoic to early Neoproterozoic.
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Andrew, Joseph E. "Geologic map of central Panamint Range, California, USA." Geosphere 18, no. 2 (March 10, 2022): 730–31. http://dx.doi.org/10.1130/ges02344.1.
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Abstract This detailed geologic map and supplemental digital data set1 examine and demonstrate the complex deformational history and reactivation relationships of the Panamint Range (California, USA), from active transtension of the Walker Lane belt, Miocene extension of the Basin and Range, to multiple Mesozoic events related to subduction, and Neoproterozoic extension. This collection of map data focuses on the geometry, kinematics, and relative timing of deformation to understand the deformation history and effects of structural reactivation. A minor portion of this geologic mapping data was presented in the analysis and figures of Andrew and Walker (2009). The Neogene extension and subsequent dextral transtension deformation has created a complex network of faults via partial reactivation of Mesozoic and Neoproterozoic structures. Structural data show oblique normal slip overprinting earlier normal slip along the western range flank fault of the western Panamint Range. Jurassic and Cretaceous deformation is localized along the western range on the Goldbug fault. The hanging wall of this fault preserves migmatitic fabrics and intense deformation due to Jurassic contraction. The Goldbug fault places Paleoproterozoic to Mesoproterozoic rocks over Neoproterozoic rocks. The Jurassic contraction has top-to-the-northeast relative transport and the more discrete Cretaceous thrust faulting has top-to-the-east transport. A set of Late Cretaceous plutonic rocks and mylonitic gneisses derived from them, occur along the Goldbug fault and demonstrate the reactivated nature of this fault in the Late Cretaceous. New data for the Butte Valley fault show that this fault cuts Late Jurassic plutonic rocks and has normal slip. The Butte Valley fault ends northward at the linked sinistral slip Warm Spring Canyon fault, which was previously interpreted to be an intrusive contact. A previously unrecognized rim syncline structure occurs along the boundary of the Late Jurassic Manly Peak quartz monzonite. Neoproterozoic deformation is difficult to discern due to the overprinting deformations. Numerous Neoproterozoic deformation-related mass wasting deposits can be seen within this formation, including a set of conspicuous allochthonous deposits and clasts of older Beck Spring Dolomite that appear to be frozen in the process of breaking away from intact, normal thickness beds in the Surprise–Happy Canyons divide. This detailed geologic mapping and collection of structural data for the rocks in the central Panamint Range were created using digital in-the-field geographic information systems software running on a field-hardened laptop computer combined with an earlier set of field data that were digitized into the digital georeferenced database. This map is a simplification of detailed geologic mapping data collected at 1:2000–1:6000 scales and reduced to 1:20000 scale. Structural data include kinematic and relative timing of deformation information.
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Hu, Chenlin, Changcheng Han, Jinghui Ma, Li Deng, and Lingfeng Zhao. "Paleowind Directions over the Tarim Block during the Mesoproterozoic, Northwestern China." Minerals 12, no. 11 (November 12, 2022): 1435. http://dx.doi.org/10.3390/min12111435.
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The Tarim Block is an ancient plate with a basement of ancient continental crust, which has been separated from the Rodinia supercontinent since the Neoproterozoic. During the Neoproterozoic, which lasted nearly 500 Myr, this block experienced significant evolutionary processes, such as proliferation, radioactive decay of elements, and gradual cooling and solidification. The investigation of Neoproterozoic paleogeography may shed light on the evolution of these geological events. In order to realize this potential, this study aimed to infer paleowind directions over the Tarim Block during each epoch of the Cryogenian–Ediacaran and to constrain the paleogeographic location of the Tarim Block. To this end, outcrop magnetic fabric data were employed to analyze the anisotropy of magnetic susceptibility within the Tarim Block. The anisotropy of magnetic susceptibility measurements yielded mean paleowind directions of 308° ± 69°, 277° ± 78°, and 256° ± 76° from the present north for the Early, Middle, and Late Cryogenian, respectively; the corresponding values for the Early and Late Ediacaran were 237° ± 77° and 254° ± 73° from the present north, respectively. Considering the rotation relationship of the Tarim Block from the Neoproterozoic to the present, the paleowind directions during the Early, Middle, and Late Cryogenian were ~55°, ~35°, and ~35° from the paleo-north, respectively. The paleowind directions during the Early and Late Ediacaran were ~35° and ~60° from paleo-north, respectively. By referring to the correspondence between the paleowind directions over the Tarim Block and trade winds in the Northern Hemisphere, this study provides evidence for the location of the Tarim Block during the Cryogenian–Ediacaran. The main contributions of this study can be summarized as follows: (1) paleowind patterns are established through the analysis of the anisotropy of magnetic susceptibility; (2) the paleogeographic location of the Tarim Block during the Cryogenian–Ediacaran is constrained; and (3) a reference for further study of the paleogeography of the Tarim Block during the Cryogenian–Ediacaran is provided.
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Koehl, Jean-Baptiste P., Steffen G. Bergh, and Klaus Wemmer. "Neoproterozoic and post-Caledonian exhumation and shallow faulting in NW Finnmark from K–Ar dating and <i>p</i>∕<i>T</i> analysis of fault rocks." Solid Earth 9, no. 4 (July 20, 2018): 923–51. http://dx.doi.org/10.5194/se-9-923-2018.
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Abstract. Well-preserved fault gouge along brittle faults in Paleoproterozoic, volcano-sedimentary rocks of the Raipas Supergroup exposed in the Alta–Kvænangen tectonic window in northern Norway yielded latest Mesoproterozoic (approximately 1050 ± 15 Ma) to mid-Neoproterozoic (approximately 825–810 ± 18 Ma) K–Ar ages. Pressure–temperature estimates from microtextural and mineralogy analyses of fault rocks indicate that brittle faulting may have initiated at a depth of 5–10 km during the opening of the Asgard Sea in the latest Mesoproterozoic–early Neoproterozoic (approximately 1050–945 Ma) and continued with a phase of shallow faulting to the opening of the Iapetus Ocean–Ægir Sea and the initial breakup of Rodinia in the mid-Neoproterozoic (approximately 825–810 Ma). The predominance and preservation of synkinematic smectite and subsidiary illite in cohesive and non-cohesive fault rocks indicate that Paleoproterozoic basement rocks of the Alta–Kvænangen tectonic window remained at shallow crustal levels (< 3.5 km) and were not reactivated since mid-Neoproterozoic times. Slow exhumation rate estimates for the early–mid-Neoproterozoic (approximately 10–75 m Myr−1) suggest a period of tectonic quiescence between the opening of the Asgard Sea and the breakup of Rodinia. In the Paleozoic, basement rocks in NW Finnmark were overthrusted by Caledonian nappes along low-angle thrust detachments during the closing of the Iapetus Ocean–Ægir Sea. K–Ar dating of non-cohesive fault rocks and microtexture mineralogy of cohesive fault rock truncating Caledonian nappe units show that brittle (reverse) faulting potentially initiated along low-angle Caledonian thrusts during the latest stages of the Caledonian Orogeny in the Silurian (approximately 425 Ma) and was accompanied by epidote–chlorite-rich, stilpnomelane-bearing cataclasite (type 1) indicative of a faulting depth of 10–16 km. Caledonian thrusts were inverted (e.g., Talvik fault) and later truncated by high-angle normal faults (e.g., Langfjorden–Vargsundet fault) during subsequent, late Paleozoic, collapse-related widespread extension in the Late Devonian–early Carboniferous (approximately 375–325 Ma). This faulting period was accompanied by quartz- (type 2), calcite- (type 3) and laumontite-rich cataclasites (type 4), whose cross-cutting relationships indicate a progressive exhumation of Caledonian rocks to zeolite-facies conditions (i.e., depth of 2–8 km). An ultimate period of minor faulting occurred in the late Carboniferous–mid-Permian (315–265 Ma) and exhumed Caledonian rocks to shallow depth at 1–3.5 km. Alternatively, late Carboniferous (?) to early–mid-Permian K–Ar ages may reflect late Paleozoic weathering of the margin. Exhumation rates estimates indicate rapid Silurian–early Carboniferous exhumation and slow exhumation in the late Carboniferous–mid-Permian, supporting decreasing faulting activity from the mid-Carboniferous. NW Finnmark remained tectonically quiet in the Mesozoic–Cenozoic.
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CRIMES, T. P., and D. McILROY. "A biota of Ediacaran aspect from lower Cambrian strata on the Digermul Peninsula, Arctic Norway." Geological Magazine 136, no. 6 (November 1999): 633–42. http://dx.doi.org/10.1017/s0016756899003179.
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Three elements of the ‘Ediacara fauna’ are described from lower Cambrian strata on the Digermul Peninsula, Norway. Nimbia occlusa Fedonkin, 1980 and Tirasiana sp. occur approximately 80 m above the base of the Lower Breivik Member, which approximately coincides with the Neoproterozoic–Cambrian boundary. A specimen of Cyclomedusa sp. has also been found in the Lower Duolbasgaissa Member about 600 m above the boundary, in rocks of trilobite-bearing age.These discoveries add to a growing body of evidence that some elements of the dominantly Neoproterozoic Ediacara fauna continue into the Phanerozoic, thereby diminishing the scope of a possible late Neoproterozoic mass-extinction event.The taxa described here, particularly Nimbia and Cyclomedusa, also occur at many other localities within Neoproterozoic strata and, in common with other elements of the Ediacara fauna, display remarkable morphological variation. Some of this diversity in form is probably caused by environmental and preservational factors. The possibility that it may, at least in part, reflect an inability of these early life forms to replicate faithfully their genes during reproduction should, however, not be overlooked.
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MA, XIAO, KUNGUANG YANG, and ALI POLAT. "U–Pb ages and Hf isotopes of detrital zircons from pre-Devonian sequences along the southeast Yangtze: a link to the final assembly of East Gondwana." Geological Magazine 156, no. 06 (August 22, 2018): 950–68. http://dx.doi.org/10.1017/s0016756818000511.
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AbstractThe Early Palaeozoic geology of the South China Craton (SCC) is characterized by an Early Palaeozoic intracontinental orogen with folded pre-Devonian strata and migmatites, MP/MT metamorphic rocks and Silurian post-orogenic peraluminous magmatic rocks in both the Yangtze and the Cathaysia blocks. In this contribution, we present new zircon U–Pb ages and Hf isotope data for detrital zircons from the Neoproterozoic to Silurian sedimentary sequences in the southeastern Yangtze Block. Samples from Neoproterozoic rocks generally display a major peak at 900–560 Ma, whereas samples from Lower Palaeozoic rocks are characterized by several broader peaks within the age ranges 600–410 Ma, 1100–780 Ma, 1.6–1.2 Ga and 2.8–2.5 Ga. Provenance analysis indicates that the 900–630 Ma detritus in Cryogenian to Ediacaran samples was derived from the Late Neoproterozoic igneous rocks in South China that acted as an internal source. The occurrence of 620–560 Ma detritus indicates the SE Yangtze was associated with Late Neoproterozoic arc volcanism along the north margin of East Gondwana. The change of provenance resulted in the deposition of 550–520 Ma and 1.1–0.9 Ga detrital zircons in the Cambrian–Ordovician sedimentary rocks. The εHf(t) values of these detrital zircons are similar to those of zircons from NW Australia–Antarctica and South India. This change of provenance in the Cambrian can be attributed to the intracontinental subduction between South China and South Qiangtang, and the convergence of India and Australia when East Gondwana finally amalgamated.
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Moussavi-Harami, R., and D. I. Gravestock. "BURIAL HISTORY OF THE EASTERN OFFICER BASIN, SOUTH AUSTRALIA." APPEA Journal 35, no. 1 (1995): 307. http://dx.doi.org/10.1071/aj94019.
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The intracratonic Officer Basin of central Australia was formed during the Neoproterozoic, approximately 820 m.y. ago. The eastern third of the Officer Basin is in South Australia and contains nine unconformity-bounded sequence sets (super-sequences), from Neoproterozoic to Tertiary in age. Burial history is interpreted from a series of diagrams generated from well data in structurally diverse settings. These enable comparison between the stable shelf and co-existing deep troughs. During the Neoproterozoic, subsidence in the north (Munyarai Trough) was much higher than in either the south (Giles area) or northeast (Manya Trough). This subsidence was related to tectonic as well as sediment loading. During the Cambrian, subsidence was much higher in the northeast and was probably due to tectonic and sediment loading (carbonates over siliciclastics). During the Early Ordovician, subsidence in the north created more accommodation space for the last marine transgression from the northeast. The high subsidence rate of Late Devonian rocks in the Munyarai Trough was probably related to rapid deposition of fine-grained siliciclastic sediments prior to the Alice Springs Orogeny. Rates of subsidence were very low during the Early Permian and Late Jurassic to Early Cretaceous, probably due to sediment loading rather than tectonic sinking. Potential Neoproterozoic source rocks were buried enough to reach initial maturity at the time of the terminal Proterozoic Petermann Ranges Orogeny. Early Cambrian potential source rocks in the Manya Trough were initially mature prior to the Delamerian Orogeny (Middle Cambrian) and fully mature on the Murnaroo Platform at the culmination of the Alice Springs Orogeny (Devonian).
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Dalziel, Ian W. D. "A global perspective on the Scottish Caledonides." Earth and Environmental Science Transactions of the Royal Society of Edinburgh 91, no. 3-4 (2000): 405–20. http://dx.doi.org/10.1017/s0263593300008269.
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ABSTRACTThe Scottish Caledonides constitute less than 10% of the length of the Caledonian-Appalachian orogen, the rocks of which define one major margin of the Laurentian craton in Neoproterozoic-Palaeozoic times. Scotland was located, however, in a critical position at the tip of a major cratonic promontory bounded by the Caledonian and Appalachian segments of that margin. Isotopic dates from minerals and rocks collected in the Scottish Highlands have been regarded for 40 years as indicating a Neoproterozoic history of compressive orogenesis that is absent in N America and Greenland. They have therefore been taken by some authors to indicate an origin exotic to Laurentia for rocks of the Northern and Grampian Highlands S and E of the Moine thrust belt. An alternative explanation is that the Neoproterozoic rocks in the Scottish Highlands are all related to the two-stage ‘breakout’ of a discrete rift-bounded Laurentian continent from the core of the Rodinian supercontinent, believed to have assembled at the end of the Mesoproterozoic.Traditional reconstructions of the late Neoproterozoic–Early Palaeozoic Earth oppose the proto-Caledonian/Appalachian margin of Laurentia and the W African craton of the newly assembled Gondwanaland. However, consideration of the global inventory of late Precambrian rifted margins, their relation to Grenvillian orogenic belts and of scale, leads to the hypothesis that the conjugate was the proto-Andean margin of S America. Recent recognition that the Cambrian and Lower Ordovician strata of the northwestern Argentine Precordillera and their underlying Grenvillian basement are unquestionably of Laurentian derivation, while not definitive, does point in this direction. If correct, this means that even the presence of Neoproterozoic orogenesis need not imply an exotic origin, as Neoproterozoic orogens are widespread in S America.Traditional models show an Early Ordovician lapetus ocean basin approximately 4500 km wide, but the remarkably synchronous Ordovician collision of arcs and other terranes with the Laurentian and Gondwanan cratons from Argentina to the British Isles, suggests that this premise may be incorrect. The Appalachian–Caledonian orogen may rather have resulted from close and complex tectonic interaction between Laurentia and Gondwana, involving intervening volcanic arcs and other terranes. The interaction may have taken place during a clockwise transit of Laurentia around the proto-Andean margin to its late Caledonian–Scandian collision with Baltica, and the final suturing of Pangaea at the close of the Palaeozoic era. A modern analogue may be the interaction between Australia and Asia, involving intervening volcanic arcs and other terranes of the western Pacific Ocean basin, from ~ 50 Ma through the Present, and into the future.
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Williams, G. E. "Late Neoproterozoic periglacial aeolian sand sheet, Stuart Shelf, South Australia*." Australian Journal of Earth Sciences 45, no. 5 (October 1998): 733–41. http://dx.doi.org/10.1080/08120099808728429.
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Bjerrum, C. J., and D. E. Canfield. "Towards a quantitative understanding of the late Neoproterozoic carbon cycle." Proceedings of the National Academy of Sciences 108, no. 14 (March 21, 2011): 5542–47. http://dx.doi.org/10.1073/pnas.1101755108.
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Haines, Peter W. "Problematic fossils in the late Neoproterozoic Wonoka Formation, South Australia." Precambrian Research 100, no. 1-3 (March 2000): 97–108. http://dx.doi.org/10.1016/s0301-9268(99)00070-4.
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Cox, Grant M., John Foden, and Alan S. Collins. "Late Neoproterozoic adakitic magmatism of the eastern Arabian Nubian Shield." Geoscience Frontiers 10, no. 6 (November 2019): 1981–92. http://dx.doi.org/10.1016/j.gsf.2017.12.006.
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Potter, Joanna, Frederick J. Longstaffe, Sandra M. Barr, Margaret D. Thompson, and Chris E. White. "Altering Avalonia: oxygen isotopes and terrane distinction in the Appalachian peri-Gondwanan realmLaboratory for Stable Isotope Science (LSIS), The University of Western Ontario, Contribution 236." Canadian Journal of Earth Sciences 45, no. 7 (July 2008): 815–25. http://dx.doi.org/10.1139/e08-024.
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Distinct 18O depletion is characteristic of a large majority of the 620–550 Ma felsic igneous rocks of Avalonia in the northern Appalachian orogen. Neoproterozoic rocks in the Boston Avalon terrane have the lowest δ18OWR values (≥–3.1‰), followed by the Mira terrane in Cape Breton Island and the Caledonia terrane in New Brunswick (≥–1.2‰), the Avalon terrane in Newfoundland (≥+2.8‰), and the Antigonish Highlands in Nova Scotia (≥+5.3‰). In contrast, this depletion of 18O is observed in very few of the Paleozoic felsic igneous rocks from these Avalonian terranes, and also in very few of the Neoproterozoic and Paleozoic felsic igneous rocks from the inboard Ganderian terranes. The low-18O character of the Neoproterozoic igneous rocks is related to regional pervasive, post-magmatic alteration by predominantly meteoric-hydrothermal fluids (δ18OH2O ∼–6‰ to –4‰) at 200–450 °C. The alteration likely occurred during late Neoproterozoic transtensional extension of Avalonia. Large-scale fluid infiltration and circulation within the Avalonian crust accompanied this extension with development of pull-apart sedimentary basins and extension-related magmatism that were the prelude to Cambrian submergence of Avalonia. This regional 18O depletion provides a geochemical fingerprint by which Avalonia can be distinguished from other peri-Gondwanan terranes. These data suggest that Avalonia existed as a composite terrane on the Gondwanan margin in the Neoproterozoic, separate from Ganderia.
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Gutiérrez-Alonso, G., J. Fernández-Suárez, Alan S. Collins, I. Abad, and F. Nieto. "Amazonian Mesoproterozoic basement in the core of the Ibero-Armorican Arc: 40Ar/39Ar detrital mica ages complement the zircon's tale." Geology 33, no. 8 (August 1, 2005): 637–40. http://dx.doi.org/10.1130/g21485ar.1.
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Abstract The 40Ar/39Ar age data on single detrital muscovite grains complement U-Pb zircon ages in provenance studies, as micas are mostly derived from proximal sources and record low-temperature processes. Ediacaran and Cambrian sedimentary rocks from northwest Iberia contain unmetamorphosed detrital micas whose 40Ar/39Ar age spectra suggest an Amazonian–Middle American provenance. The Ediacaran sample contained only Neoproterozoic micas (590–783 Ma), whereas the Cambrian sample contained three age groups: Neoproterozoic (550–640 Ma, Avalonian–Cadomian–Pan African), Mesoproterozoic- Neoproterozoic boundary (ca. 920–1060 Ma, Grenvillian-Sunsas), and late Paleoproterozoic (ca. 1580–1780 Ma, Rio Negro). Comparison of 40Ar/39Ar muscovite ages with published detrital zircon age data from the same formations supports the hypothesis that the Neoproterozoic basins of northwest Iberia were located in a peri-Amazonian realm, where the sedimentary input was dominated by local periarc sources. Tectonic slivering and strike-slip transport along the northern Gondwanan margin affected both the basins and fragments of basement that were transferred from Amazonian to northern African realms during the latest Neoproterozoic–earliest Cambrian. Exhumation and erosion of these basement sources caused shedding of detritus to the Cambrian basins, in addition to detritus sourced in the continental mainland. The apparent dominance of Rio Negro–aged micas in the Cambrian sandstone suggests the presence of unexposed basement of that age beneath the core of the Ibero-Armorican Arc.
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Valentine, James W. "How were vendobiont bodies patterned?" Paleobiology 27, no. 3 (2001): 425–28. http://dx.doi.org/10.1666/0094-8373(2001)027<0425:hwvbp>2.0.co;2.
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It is difficult to assign the animal-like body fossils of the late Neoproterozoic to crown metazoan phyla. Many Neoproterozoic fossils appear to share an architectural theme, which was characterized by Seilacher (1984, 1989) as modular; he noted that the modules, named pneus, could be arranged in a series of distinctive geometries to produce many of the Neoproterozoic fossil morphologies. The assemblages of pneus formed “quilted” constructions. Seilacher further suggested that these fossils might represent a multicellular clade that evolved independently of Metazoa–in effect, that they represented a kingdom of their own, which he named the Vendozoa. In later contributions, Seilacher (1992) renamed putatively quilted forms as the Vendobionta, and Buss and Seilacher (1994) considered Vendobionta to be a possible sister to Eumetazoa. The affinities suggested for vendobionts by various workers form a long list, ranging from protistans through fungi to several animal groups. Many vendobionts appear to be at the tissue grade of construction, and in this respect resemble cnidarians, to which they are most often compared. Neoproterozoic fossil assemblages also contain numbers of forms that are unlikely to be vendobionts, including a variety of “medusoids,” tentaculate fossils such as Hiemolora and Ediacaria (see Fedonkin 1992) that somewhat resemble sea anemones and may well be stem anthozoans. Additionally, numbers of Neoproterozoic forms have been suggested to be bilaterians, most notably the sluglike Kimberella (Fedonkin and Waggoner 1997). The contents and morphological limits of Vendobionta, and of some other higher taxa proposed for Neoproterozoic forms, are uncertain.
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Tostevin, Rosalie, and Benjamin J. W. Mills. "Reconciling proxy records and models of Earth's oxygenation during the Neoproterozoic and Palaeozoic." Interface Focus 10, no. 4 (June 12, 2020): 20190137. http://dx.doi.org/10.1098/rsfs.2019.0137.
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A hypothesized rise in oxygen levels in the Neoproterozoic, dubbed the Neoproterozoic Oxygenation Event, has been repeatedly linked to the origin and rise of animal life. However, a new body of work has emerged over the past decade that questions this narrative. We explore available proxy records of atmospheric and marine oxygenation and, considering the unique systematics of each geochemical system, attempt to reconcile the data. We also present new results from a comprehensive COPSE biogeochemical model that combines several recent additions, to create a continuous model record from 850 to 250 Ma. We conclude that oxygen levels were intermediate across the Ediacaran and early Palaeozoic, and highly dynamic. Stable, modern-like conditions were not reached until the Late Palaeozoic. We therefore propose that the terms Neoproterozoic Oxygenation Window and Palaeozoic Oxygenation Event are more appropriate descriptors of the rise of oxygen in Earth's atmosphere and oceans.
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Colpron, Maurice, James M. Logan, and James K. Mortensen. "U-Pb zircon age constraint for late Neoproterozoic rifting and initiation of the lower Paleozoic passive margin of western Laurentia." Canadian Journal of Earth Sciences 39, no. 2 (February 1, 2002): 133–43. http://dx.doi.org/10.1139/e01-069.
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A concordant UPb zircon age of 569.6 ± 5.3 Ma from synrift volcanic rocks of the Hamill Group, southeastern Canadian Cordillera, provides the first direct UPb geochronologic constraint on timing of latest Neoproterozoic rifting along western Laurentia. This age confirms a previous estimate of 575 ± 25 Ma for timing of continental breakup, as derived from the analysis of tectonic subsidence in lower Paleozoic miogeoclinal strata of the North American Cordillera. It also corresponds to the timing of passive margin deposition in the "underlying" Windermere Supergroup of the northern Cordillera, as determined by chemostratigraphic correlations. These timing relationships imply a different breakup history for the northern, as compared to the southern, Cordillera. We propose a model that attempts to explain this paradox of Cordilleran geology. The earlier Neoproterozoic (Windermere-age) rifting event probably records breakup of a continental mass from northern Laurentia followed by development of a passive margin. Accordingly, the Windermere Supergroup of the southern Canadian Cordillera was deposited in an intracontinental rift. The second Neoproterozoic rifting (HamillGog) is interpreted to indicate continental breakup and establishment of a passive margin along western Laurentia.
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Djerossem, Félix, Julien Berger, Olivier Vanderhaeghe, Moussa Isseini, Jérôme Ganne, and Armin Zeh. "Neoproterozoic magmatic evolution of the southern Ouaddaï Massif (Chad)." BSGF - Earth Sciences Bulletin 191 (2020): 34. http://dx.doi.org/10.1051/bsgf/2020032.
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This paper presents new petrological, geochemical, isotopic (Nd) and geochronological data on magmatic rocks from the poorly known southern Ouaddaï massif, located at the southern edge of the so-called Saharan metacraton. This area is made of greenschist to amphibolite facies metasediments intruded by large pre- to syn-tectonic batholiths of leucogranites and an association of monzonite, granodiorite and biotite granite forming a late tectonic high-K calc-alkaline suite. U-Pb zircon dating yields ages of 635 ± 3 Ma and 613 ± 8 Ma on a peraluminous biotite-leucogranite (containing numerous inherited Archean and Paleoproterozoic zircon cores) and a muscovite-leucogranite, respectively. Geochemical fingerprints are very similar to some evolved Himalayan leucogranites suggesting their parental magmas were formed after muscovite and biotite dehydration melting of metasedimentary rocks. A biotite-granite sample belonging to the late tectonic high-K to shoshonitic suite contains zircon rims that yield an age of 540 ± 5 Ma with concordant inherited cores crystallized around 1050 Ma. Given the high-Mg# (59) andesitic composition of the intermediate pyroxene-monzonite, the very similar trace-element signature between the different rock types and the unradiogenic isotopic signature for Nd, the late-kinematic high-K to shoshonitic rocks formed after melting of the enriched mantle and further differentiation in the crust. These data indicate that the southern Ouaddaï was part of the Pan-African belt. It is proposed that it represents a continental back-arc basin characterized by a high-geothermal gradient during Early Ediacaran leading to anatexis of middle to lower crustal levels. After tectonic inversion during the main Pan-African phase, late kinematic high-K to shoshonitic plutons emplaced during the final post-collisional stage.
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Meng, Xianghong, Yu Zhang, Duoyun Wang, and Xue Zhang. "Provenance analysis of the Late Triassic Yichuan Basin: constraints from zircon U-Pb geochronology." Open Geosciences 10, no. 1 (March 21, 2018): 34–44. http://dx.doi.org/10.1515/geo-2018-0003.
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AbstractLaser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U-Pb dating has been performed on detrital zircons from the Chunshuyao Formation sandstone of Yichuan Basin. The ages of 85 detrital zircon grains are divided into three groups: 252-290 Ma, 1740-2000 Ma, and 2400-2600 Ma. The lack of Early Paleozoic and Neoproterozoic U-Pb ages indicates that there is no input from the Qinling Orogen, because the Qinling Orogen is characterized by Paleozoic and Neoproterozoic material. In combination with previous research, we suggest that the source of the Chunshuyao Formation is most likely recycled from previous sedimentary rocks from the North China Craton. In the Late Triassic, the Funiu ancient land was uplifted which prevented source material from the Qinling Orogen. Owing to the Indosinian orogeny, the strata to the east of the North China Craton were uplifted and eroded. The Yichuan Basin received detrital material from the North China Craton.
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Scharf, Andreas, Frank Mattern, Mohammed Al-Wardi, Gianluca Frijia, Daniel Moraetis, Bernhard Pracejus, Wilfried Bauer, and Ivan Callegari. "Chapter 6 Conclusions, differences between the Jabal Akhdar and Saih Hatat domes and unanswered questions." Geological Society, London, Memoirs 54, no. 1 (2021): 105–11. http://dx.doi.org/10.1144/m54.6.
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AbstractThis chapter provides the conclusions/outlines of the tectonics, affecting the Southeastern Oman Mountains, including the Jabal Akhdar and Saih Hatat domes. The main tectonic events include amongst others (1) Neoproterozoic rifting, (2) two distinct early Paleozoic compressive events, (3) large-scale open ‘Hercynian’ folding and formation of a pronounced unconformity during the late Paleozoic, (4) rifting preceding the opening of the Neo-Tethys Ocean during the late Paleozoic, (5) late Cretaceous obduction of the Semail Ophiolite and the response of the Arabian lithosphere as well as (6) post-obductional tectonics. Also of major geological significance are the three major glaciations (Sturtian, Marinoan and Late Paleozoic Gondwana glaciation) which have been recorded in the rocks of northern Oman. Moreover, major lithological, structural and metamorphic differences exist between the Jabal Akhdar and Saih Hatat domes. It appears likely that a major fault, striking parallel to the eastern margin of the Jabal Akhdar Dome, probably originating during Neoproterozoic terrain accretion, acted as a divide between both domes until present. This fault was multiple times reactivated and could explain the differences between the two domes. A catalogue of unanswered questions is included in chronological order to express that many geological aspects need further investigation and future research projects.
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ŽÁČKOVÁ, ELIŠKA, JIŘÍ KONOPÁSEK, JAN KOŠLER, and PETR JEŘÁBEK. "Detrital zircon populations in quartzites of the Krkonoše–Jizera Massif: implications for pre-collisional history of the Saxothuringian Domain in the Bohemian Massif." Geological Magazine 149, no. 3 (September 13, 2011): 443–58. http://dx.doi.org/10.1017/s0016756811000744.
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AbstractAge spectra of detrital zircons from metamorphosed quartzites of the Krkonoše–Jizera Massif in the northeastern part of the Saxothuringian Domain were obtained by U–Pb laser ablation inductively coupled plasma mass spectrometry dating. The zircon ages cluster in the intervals of 450–530 Ma and 550–670 Ma, and show individual data between 1.6 and 3.1 Ga. Zircons in the analysed samples are predominantly of Cambrian–Ordovician and Neoproterozoic age, and the marked peak at c. 525–500 Ma suggests a late Cambrian maximum age for the sedimentary protolith. Detritus of the quartzites probably originated from the erosion of Cambrian–Ordovician granitoids and their Neoproterozoic (meta)sedimentary or magmatic country rocks. The lack of Neoproterozoic (meta)sedimentary rocks in the central and eastern part of the Krkonoše–Jizera Massif suggests that the country rocks to voluminous Cambrian–Ordovician magmatic bodies were largely eroded during the formation of early Palaeozoic rift basins along the southeast passive margin of the Saxothuringian Domain. The detrital zircon age spectra confirm the previous interpretation that the exposed basement, dominated by Neoproterozoic to Cambrian–Ordovician granitoids, was overthrust during Devonian–Carboniferous subduction–collision processes by nappes composed of metamorphosed equivalents of the uppermost Cambrian–Devonian passive margin sedimentary formations. Only a negligible number of Mesoproterozoic ages, typically from the Grenvillian event, supports the interpretation that the Saxothuringian Neoproterozoic basement has an affinity to the West African Craton of the northwestern margin of Gondwana.
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Lemieux, Yvon, Thomas Hadlari, and Antonio Simonetti. "Detrital zircon geochronology and provenance of Devono-Mississippian strata in the northern Canadian Cordilleran miogeoclineThis article is one of a series of papers published in this Special Issue on the theme of Geochronology in honour of Tom Krogh.Northwest Territories Geoscience Office Contribution 0047. Geological Survey of Canada Contribution 20100432." Canadian Journal of Earth Sciences 48, no. 2 (February 2011): 515–41. http://dx.doi.org/10.1139/e10-056.
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U–Pb ages have been determined on detrital zircons from the Upper Devonian Imperial Formation and Upper Devonian – Lower Carboniferous Tuttle Formation of the northern Canadian Cordilleran miogeocline using laser ablation – multicollector – inductively coupled plasma – mass spectrometry. The results provide insights into mid-Paleozoic sediment dispersal in, and paleogeography of, the northern Canadian Cordillera. The Imperial Formation yielded a wide range of detrital zircon dates; one sample yielded dominant peaks at 1130, 1660, and 1860 Ma, with smaller mid-Paleozoic (∼430 Ma), Neoproterozoic, and Archean populations. The easternmost Imperial Formation sample yielded predominantly late Neoproterozoic – Cambrian zircons between 500 and 700 Ma, with lesser Mesoproterozoic and older populations. The age spectra suggest that the samples were largely derived from an extensive region of northwestern Laurentia, including the Canadian Shield, igneous and sedimentary provinces of Canada’s Arctic Islands, and possibly the northern Yukon. The presence of late Neoproterozoic – Cambrian zircon, absent from the Laurentian magmatic record, indicate that a number of grains were likely derived from an exotic source region, possibly including Baltica, Siberia, or Arctic Alaska – Chukotka. In contrast, zircon grains from the Tuttle Formation show a well-defined middle Paleoproterozoic population with dominant relative probability peaks between 1850 and 1950 Ma. Additional populations in the Tuttle Formation are mid-Paleozoic (∼430 Ma), Mesoproterozoic (1000–1600 Ma), and earlier Paleoproterozoic and Archean ages (>2000 Ma). These data lend support to the hypothesis that the influx of sediments of northerly derivation that supplied the northern miogeocline in Late Devonian time underwent an abrupt shift to a source of predominantly Laurentian affinity by the Mississippian.
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Fyffe, Leslie R. "The Grand Manan Terrane of New Brunswick: Tectonostratigraphy and Relationship to the Gondwanan Margin of the Iapetus Ocean." Geoscience Canada 41, no. 4 (December 3, 2014): 483. http://dx.doi.org/10.12789/geocanj.2014.41.051.
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Recently gathered stratigraphic and U–Pb geochronological data indicate that the pre-Triassic rocks of the Grand Manan Terrane on the eastern side of Grand Manan Island can be divided into: (1) Middle Neoproterozoic (late Cryogenian) quartzose and carbonate sedimentary sequences (The Thoroughfare and Kent Island formations); (2) a Late Neoproterozoic (early Ediacaran) volcanic-arc sequence (Ingalls Head Formation); and (3) Late Neoproterozioc (mid- Ediacaran) to earliest Cambrian (early Terreneuvian) sedimentary and volcanic-arc sequences (Great Duck Island, Flagg Cove, Ross Island, North Head, Priest Cove, and Long Pond Bay formations). A comparison to Precambrian terranes on the New Brunswick mainland (Brookville and New River terranes) and in adjacent Maine (Islesboro Terrane) suggests that the sedimentary and volcanic sequences of the Grand Manan Terrane were deposited on the continental margin of a Precambrian ocean basin that opened during the breakup of Rodinia in the Middle Neoproterozoic (Cryogenian) and closed by the Early Cambrian (Terreneuvian) with the final assembling of Gondwana. Rifting associated with the initial opening of the Paleozoic Iapetus Ocean began in the Late Neoproterozoic (late Ediacaran) and so overlapped in time with the closing of the Precambrian Gondwanan ocean. The southeastern margin of the Iapetus Ocean is defined by thick sequences of quartz-rich Cambrian sediments (within the St. Croix and Miramichi terranes of New Brunswick) that were largely derived from recycling of Precambrian passive-margin sedimentary rocks preserved in the Grand Manan and Brookville terranes of New Brunswick and in the Islesboro Terrane of Maine. These Precambrian terranes are interpreted to represent dextrally displaced basement remnants of the Gondwanan continental margin of Iapetus, consistent with the model of a two-sided Appalachian system proposed by Hank Williams in 1964 based on his work in Newfoundland.SOMMAIREDes données stratigraphiques et géochronologiques U–Pb obtenues récemment indiquent que les roches prétriasiques du terrane de Grand Manan du côté est de l’île Grand Manan peuvent être répartis en: 1) séquences sédimentaires quartzeuses et carbonatées du Néoprotérozoïque moyen (Cryogénien tardif) (formations de Thoroughfare et de Kent Island); 2) séquence d’arc volcanique du Néoprotérozoïque tardif (Édiacarien précoce) (formation d’Ingalls Head); 3) séquences sédimentaires et d’arc volcanique du Néoprotérozoïque tardif (milieu de l’Édiacarien) au tout début du Cambrien (Terreneuvien précoce) (formations de Great Duck Island, Flagg Cove, Ross Island, North Head, Priest Cove et Long Pond Bay). Une comparaison avec des terranes du Précambrien dans la partie continentale du Nouveau-Brunswick (terranes de Brookville et New River) et dans le Maine adjacent (terrane d’Islesboro) semble indiquer que les séquences sédimentaires et volcaniques du terrane de Grand Manan se sont déposées sur la marge continentale d’un bassin océanique précambrien qui s’est ouvert durant la fracturation de la Rodinia au Néoprotérozoïque moyen (Cryogénien) et s’est fermé au Cambrien précoce (Terreneuvien) avec l’assemblage final du Gondwana. La distension continentale associée à l’ouverture initiale de l’océan Iapetus au Paléozoïque a commencé au Néoprotérozoïque tardif (Édiacarien tardif) et a donc partiellement coïncidé avec la fermeture de l’océan précambrien du Gondwana. La marge sud-est de l’océan Iapetus est définie par d’épaisses séquences de sédiments cambriens riches en quartz (dans les terranes de St. Croix et de Miramichi du Nouveau-Brunswick) issus en grande partie du recyclage de roches sédimentaires de la marge continentale passive du Précambrien préservées dans les terranes de Grand Manan et de Brookville au Nouveau-Brunswick et dans le terrane d’Islesboro dans le Maine. Ces terranes précambriens sont interprétés comme la représentation de vestiges, ayant subi un déplacement dextre, du socle de la marge continentale gondwanienne de l’océan Iapetus, ce qui concorde avec le modèle d’un système appalachien à deux côtés proposé par Hank Williams en 1964 sur la base de ses travaux à Terre-Neuve.
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Qiaofan, Hu, Feng Zuohai, Mo Jiangping, and Fang Ke. "Fluid inclusions, H-O-S isotopic characteristics and genesis of the Chambishi copper deposit, Zambia." E3S Web of Conferences 290 (2021): 03016. http://dx.doi.org/10.1051/e3sconf/202129003016.
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In this paper, fluid inclusions and H-O-S isotope geochemistry of the Chambishi copper deposit in Zambia are studied. According to the fluid inclusion in quartz and H-O-S isotope characteristics, it is concluded that ore-forming hydrothermal fluid is derived from mantle source and crust source magma mingling, the cause of copper precipitation, sedimentary type sulfur layered mineralization are mainly from diagenetic sulfides and seawater sulfate. Sulfate is mainly reduced by thermochemical method. The hydrothermal vein mineralization of Chambishi copper deposit is closely related to the magmatic activity in the middle Neoproterozoic, and the sedimentary stratified mineralization is mainly related to the large-scale orogeny and regional metamorphism in the late Neoproterozoic.
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Saleh, Ahmed. "Paleomagnetism of Late Neoproterozoic African Dike Swarms from the South Eastern Desert and the Paleo-Neoproterozoic Dataset from Egypt." Pure and Applied Geophysics 177, no. 11 (September 3, 2020): 5251–62. http://dx.doi.org/10.1007/s00024-020-02562-5.
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Anttila, Eliel, Francis Macdonald, and Uyanga Bold. "Stratigraphy of the Khuvsgul Group, Mongolia." Mongolian Geoscientist 26, no. 52 (June 23, 2021): 2–15. http://dx.doi.org/10.5564/mgs.v26i52.1516.
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The Khuvsgul Group (Khuvsgul Province, Mongolia) is a Late Neoproterozoic to Cambrian carbonate-dominated succession that includes minor glacial diamictite and one of the largest known ore-grade phosphate deposits in the world. These strata, which have experienced low-grade metamorphism, are exposed in the Khoridol-Saridag Range on the western margin of Lake Khuvsgul. Since 2017, new geologic mapping and field studies have been conducted in the Khuvsgul region. During the course of this work, it has become necessary to restructure the stratigraphic framework of the Khuvsgul Group in order to better facilitate geologic mapping, stratigraphic observations, and regional correlations. We have divided the lower Khuvsgul Group into four distinct formations spanning the Cryogenian and Ediacaran, each of which encompass strata associated with the Sturtian glaciation, Cryogenian non-glacial interlude, Marinoan glaciation, and basal Ediacaran transgression respectively. The phosphorites of the Khuvsgul Group are now included within a new distinct formation, while the overlying Cambrian carbonates and siliciclastic rocks have been further subdivided to streamline mapping and correlation efforts. The stratigraphic framework outlined below will simplify identification and differentiation of Khuvsgul Group rocks in the field and provide a foundation for the interpretation of Khuvsgul Group strata within the context of the changing climatic, tectonic, and paleoenvironmental conditions of the late Neoproterozoic and early Cambrian.
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Piper, David JW, and Georgia Pe-Piper. "Tectonic deformation and magmatism along the southern flank of the Maritimes Basin: the northeastern Cobequid Highlands, Nova Scotia." Canadian Journal of Earth Sciences 38, no. 1 (January 1, 2001): 43–58. http://dx.doi.org/10.1139/e00-075.
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Distributed crustal-scale faulting in the Cobequid Highlands in the Middle Devonian to Carboniferous resulted from the oblique convergence of the Meguma and Avalon terranes. In the northeastern Cobequid Highlands, seismic reflection profiles show Neoproterozoic and lower Paleozoic rocks, together with enigmatic foliated rocks, overlying the Early Carboniferous Fountain Lake Group. The foliated rocks form the hanging wall of a north-vergent thrust fault. Their protolith is inferred from petrography and geochemistry to be principally Neoproterozoic rhyodacitic tuff and late Paleozoic hypabyssal intrusions. The age of thrusting is stratigraphically constrained to the late Tournaisian mid-Viséan, and sericite from mylonite yielded a Tournaisian KAr age of 352 ± 8 Ma. The thrusting occurs at the base of a tectonic escape sheet and resulted from a restraining bend in the Rockland Brook master fault. Farther west, where the Rockland Brook fault trends almost eastwest, Tournaisian extensional features include the Nuttby basin and widespread gabbro dykes, sills, and stocks. At deeper structural levels, granite plutons were intruded in a similar tectonic regime of thrusting and local extension by lateral movement of basement blocks. The emplacement process resulted from progressive widening of initial dykes, analogous to the dykes deformed in the thrust hanging wall. Regionally, in the Tournaisian of the southern Maritimes Basin half-graben formation was synchronous with pluton emplacement and thrusting in adjacent horsts.
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Prasad, Bijai, S. N. Uniyal, and Ramson Asher. "Organic-walled microfossils from the Proterozoic Vindhyan Supergroup of Son Valley, Madhya Pradesh, India." Journal of Palaeosciences 54, no. (1-3) (December 31, 2005): 13–60. http://dx.doi.org/10.54991/jop.2005.68.
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Well-preserved and diversified organic-walled microfossil assemblages are recorded from the Vindhyan sediments of Son Valley and DMH-A well, in Madhya Pradesh. The microfossils include acritarchs, coccoid and filamentous taxa that suggest a Meso-Neoproterozoic age for the Vindhyan Supergroup which, hitherto, was assigned a Late Paleoproterozoic to Early Paleozoic age, based on fossil evidences and radiometric datings.
The Kajrahat Limestone, within the basal Semri Group, recorded abundant filamentous microfossils, viz. Polythrichoides, Karamia, Arctacellularia and Siphonophycus along with simple unornamented sphaeromorph acritarchs (Leiosphaeridia spp.), suggesting ca. 1500-1450 Ma age of Early Mesoproterozoic. The microfossil assemblage of Deonar Formation also includes the above taxa; however, Satka, Eomicrocystis and acanthomorph acritarchs, Tappania spp., appear within this formation along with abundant polygonomorph acritarchs referable to Octoedryxium. The Deonar microfossil assemblage resembles the assemblage of Roper Group (northern Australia) and suggests ca. 1450-1350 Ma age of Early to Middle Mesoproterozoic.
The sediments of Kheinjua Subgroup are marked by the appearance of various species of Navifusa, Simia and Pterospermopsimorpha in the Koldaha Shale with overall abundance of Tappania, Satka, Eomicrocystis, Kildinosphaera and Leiosphaeridia. The presence of Middle to Late Mesoproterozoic marker taxa, viz. Tappania plana, T. tubata and Navifusa segmentata helps to correlate the Koldaha Shale and Salkhan Limestone assemblages with the assemblage of the Ruyang Group (China), suggesting an Ectasian-Stenian (ca.1350-1050 Ma) age. In additon to the above taxa, the appearance of Early Neoproterozoic marker taxa, such as, Vandalosphaeridium, Bavlinella, Melanocyrillium and budding leiosphaerids in the Rampur Formation indicates a Late Stenian-Tonian age (ca. 1050-850 Ma) for this formation.
The microfossil assemblage of the Rohtas Subgroup is quite distinct as the marker taxa of the Kheinjua Subgroup, viz. Tappania spp.and Navifusa spp. disappear. The presence of Trachysphaeridium laufeldi, Vandalosphaeridium reticulatum, Bavlinella faveolata and Stictosphaeridium spp., and the disappearance of Eomicrocystis, Satka and budding leiosphaerids within this formation allow its correlation with Middle Neoproterozoic Miroyedikha (Siberia) and Husar-Kanpa (central Australia) assemblages, suggesting an Early Cryogenian (ca.850-750 Ma) age for the Rohtas Subgroup.
The microfossil assemblages from the Kaimur and Rewa groups are represented by the species of Symplassosphaeridium, Synsphaeridium and Leiosphaeridia. The occurrence of B. faveolata, T laufeldi and Octoedryxium truncatum in their assemblages suggest a Middle to Late Neoproterozoic (Late Cryogenian; ca.750-650 Ma) age. The sediments of the Bhander Group also include the above taxa. However, the appearance of Ediacaran (Vendian) marker species of Obruchevella, viz. O. parva and O. valdaica in the Ganurgarh Shale, and their abundance in the overlying Nagod Limestone and Sirbu Shale, suggests a Late Cryogenian-Early Ediacaran (ca. 650-570 Ma) age for the Bhander Group. Yet, the appearance of Obruchevella delicata, Lophosphaeridium tentativum and Cymatiosphaera sp. in the Nagod Limestone, and Obruchevella parvissima, Cristallinium sp. and Dictyotidium sp. in the Sirbu Shale suggest that the age of the Bhander Group extends into the Late Ediacaran (ca.570-544 Ma).
The record of Calymmian (ca. 1500 Ma) to Late Ediacaran (ca. 544 Ma) organic-walled microfossil assemblages categorically suggests an Early Mesoproterozoic to Terminal Proterozoic age-range for the Vindhyan Supergroup. The occurrence of well-developed Middle and Late Mesoproterozoic microfossil assemblages in the Deonar Formation and Kheinjua Subgroup negates the Late Paleoproterozoic (ca. 1630 Ma) age assignment to them, based on radiometric datings. The presence of Ediacaran (Vendian) marker species of Obruchevella and the absence of distinctive Early Cambrian acritarchs in the Bhander Group brackets the upper age limits of Vindhyan Supergroup to the Late Ediacaran, and does not encompass the Lower Paleozoic.
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Lane, L. S., and G. E. Gehrels. "Detrital zircon lineages of late Neoproterozoic and Cambrian strata, NW Laurentia." Geological Society of America Bulletin 126, no. 3-4 (January 24, 2014): 398–414. http://dx.doi.org/10.1130/b30848.1.
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Hill, A. C., K. Grey, V. A. Gostin, and L. J. Webster. "New records of Late Neoproterozoic Acraman ejecta in the Officer Basin." Australian Journal of Earth Sciences 51, no. 1 (February 2004): 47–51. http://dx.doi.org/10.1046/j.1400-0952.2003.01044.x.
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Canfield, D. E., S. W. Poulton, and G. M. Narbonne. "Late-Neoproterozoic Deep-Ocean Oxygenation and the Rise of Animal Life." Science 315, no. 5808 (January 5, 2007): 92–95. http://dx.doi.org/10.1126/science.1135013.
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