Journal articles: 'Late Proterozoic'

1

Chumakov, N. M. "Late Proterozoic African glacial era." Stratigraphy and Geological Correlation 19, no. 1 (February 2011): 1–20. http://dx.doi.org/10.1134/s0869593810061012.

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Hambrey, M. J., and W. B. Harland. "The late proterozoic glacial era." Palaeogeography, Palaeoclimatology, Palaeoecology 51, no. 1-4 (October 1985): 255–72. http://dx.doi.org/10.1016/0031-0182(85)90088-4.

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Halverson, Galen P., Susannah M. Porter, and Timothy M. Gibson. "Dating the late Proterozoic stratigraphic record." Emerging Topics in Life Sciences 2, no. 2 (July 13, 2018): 137–47. http://dx.doi.org/10.1042/etls20170167.

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The Tonian and Cryogenian periods (ca. 1000–635.5 Ma) witnessed important biological and climatic events, including diversification of eukaryotes, the rise of algae as primary producers, the origin of Metazoa, and a pair of Snowball Earth glaciations. The Tonian and Cryogenian will also be the next periods in the geological time scale to be formally defined. Time-calibrating this interval is essential for properly ordering and interpreting these events and establishing and testing hypotheses for paleoenvironmental change. Here, we briefly review the methods by which the Proterozoic time scale is dated and provide an up-to-date compilation of age constraints on key fossil first and last appearances, geological events, and horizons during the Tonian and Cryogenian periods. We also develop a new age model for a ca. 819–740 Ma composite section in Svalbard, which is unusually complete and contains a rich Tonian fossil archive. This model provides useful preliminary age estimates for the Tonian succession in Svalbard and distinct carbon isotope anomalies that can be globally correlated and used as an indirect dating tool.

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Brookfield, M. E. "Lithostratigraphic correlation of Blaini Formation (late Proterozoic, Lesser Himalaya, India) with other late Proterozoic tillite sequences." Geologische Rundschau 76, no. 2 (June 1987): 477–84. http://dx.doi.org/10.1007/bf01821087.

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Jepsen, H. F., J. C. Escher, J. D. Friderichsen, and A. K. Higgins. "The geology of the north-eastern corner of Greenland - photogeological studies and 1993 field work." Rapport Grønlands Geologiske Undersøgelse 161 (January 1, 1994): 21–33. http://dx.doi.org/10.34194/rapggu.v161.8240.

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Late Archaean and Early Proterozoic crust-forming events in North-East and eastern North Greenland were succeeded by Middle Proterozoic sedimentation and volcanic activity; Late Proterozoic through Tertiary sedimentation was interrupted by several periods of tectonic activity, including the Caledonian orogeny in East Greenland and the Mesozoic deformation of the Wandel Hav mobile belt. Photogeological studies helped pinpoint areas of special interest which were investigated during the short 1993 field season. Insights gained during field work include: the nature of the crystalline basement terrain in the Caledonian fold belt, redefinition of the upper boundary of the Upper Proterozoic Rivieradal sandstones, revision of Caledonian nappe terminology, and the northern extension of the Caledonian Storstrømmen shear zone.

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Carver, J. H., and I. M. Vardavas. "Precambrian glaciations and the evolution of the atmosphere." Annales Geophysicae 12, no. 7 (June 30, 1994): 674–82. http://dx.doi.org/10.1007/s00585-994-0674-3.

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Abstract. Precambrian glaciations appear to be confined to two periods, one in the early Proterozoic between 2.5 and 2 Gyears BP (Before Present) and the other in the late Proterozoic between 1 and 0.57 Gyear BP. Possible reasons for these broad features of the Precambrian climate have been investigated using a simple model for the mean surface temperature of the Earth that partially compensates for the evolution of the Sun by variations in the atmospheric CO2 content caused by outgassing, the formation of continents and the weathering of the Earth's land surface. It is shown that the model can explain the main changes in the Precambrian climate if the early Proterozoic glaciations were caused by a major episode of continental land building commencing about 3 Gyears BP while the late Proterozoic glaciations resulted from biologicallyenhanced weathering of the land surface due to the proliferation of life forms in the transition from the Proterozoic to the Phanerozoic that began about 1 Gyear BP.

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Serezhnikova, E. A. "Skeletogenesis in problematic Late Proterozoic Lower Metazoa." Paleontological Journal 48, no. 14 (December 2014): 1457–72. http://dx.doi.org/10.1134/s0031030114140123.

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8

Al-Fugha, Hassan. "Petrology and petrogenesis of a Late Proterozoic dyke swarm in South-Jordan." Neues Jahrbuch für Geologie und Paläontologie - Monatshefte 2002, no. 4 (April 25, 2002): 201–19. http://dx.doi.org/10.1127/njgpm/2002/2002/201.

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9

Clark, G. S., and D. C. P. Schledewitz. "Rubidium–strontium ages of Archean and Proterozoic rocks in the Nejanilini and Great Island domains, Churchill Province, northern Manitoba, Canada." Canadian Journal of Earth Sciences 25, no. 2 (February 1, 1988): 246–54. http://dx.doi.org/10.1139/e88-027.

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Rubidium–strontium whole-rock ages are reported from the Nejanilini – Great Island area in northeastern Manitoba. This area is part of an extensive zone of Archean basement that was metamorphosed and intruded by granitic magma during the Proterozoic; it extends into Saskatchewan and southern District of Keewatin, Northwest Tertitories. An age of 2577 ± 42 Ma (1σ error) for the extensive Nejanilini granulite massif (Nejanilini domain), considered one of the oldest rock units in the area, is interpreted as a minimum age for late Archean granulite-facies metamorphism. A minimum age of 2052 ± 41 Ma (initial ratio 0.7150) for quartz–feldspar porphyry that intrudes the Seal River volcanic suite constrains the age of these volcanics and could represent a partially reset Archean age. Early Proterozoic quartzite and metagreywacke of the Great Island Group unconformably overlies the quartz–feldspar porphyry. These metasedimentary rocks, which are probably correlative with the Daly Lake Group (Saskatchewan) or the Hurwitz Group (southern District of Keewatin), give an age of 1885 ± 85 Ma, with an initial ratio of 0.7093. The age records the time of closure of the Rb–Sr isotopic system subsequent to early Proterozoic metamorphism. The age and initial ratio are consistent with published results for other, possibly correlative, metasedimentary rocks in this zone. Modelling the Rb–Sr isotopic data constrains the time of sedimentation to between ca. 2100 and 2000 Ma ago. Syn- to late-kinematic, early Proterozoic granite to granodiorite batholiths, which intruded metasedimentary rocks of the Great Island Group, may largely be the product of melting of Archean basement, based on field evidence and high initial 87Sr/86Sr ratios. The Caribou Lake porphyritic quartz monzonite gives an age of 1795 ± 35 Ma, with an initial 87Sr/86Sr ratio of 0.7084. High initial ratios seem to typify early Proterozoic granitic rocks in this remobilized craton.

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10

Bertrand, Jean Michel, and Emmanuel Ferraz Jardim de Sá. "Where are the Eburnian–Transamazonian collisional belts?" Canadian Journal of Earth Sciences 27, no. 10 (October 1, 1990): 1382–93. http://dx.doi.org/10.1139/e90-148.

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The reconstruction of Early Proterozoic crustal evolution and geodynamic environments, in Africa and South America, is incomplete if cratonic areas alone are studied. If the presence of high-grade gneisses is considered as a first clue to past collisional behaviour, 2 Ga high-grade gneisses are more abundant within the Pan-African–Brasiliano mobile belts than in the intervening pre-Late Proterozoic cratons. The West African craton and the Guiana–Amazonia craton consist of relatively small Archaean nuclei and widespread low- to medium-grade volcanic and volcanoclastic formations intruded by Early Proterozoic granites. By contrast, 2 Ga granulitic assemblages and (or) nappes and syntectonic granites are known in several areas within the Pan-African–Brasiliano belts of Hoggar–Iforas–Air, Nigeria, Cameroon, and northeast Brazil. Nappe tectonics have been also described in the Congo–Chaillu craton, and Early Proterozoic reworking of older granulites may have occurred in the São Francisco craton. The location of the Pan-African–Brasiliano orogenic belts is probably controlled by preexisting major structures inherited from the Early Proterozoic. High-grade, lower crustal assemblages 2 Ga old have been uplifted or overthrust and now form polycyclic domains in these younger orogenic belts, though rarely in the cratons themselves. The Congo–Chaillu and perhaps the São Francisco craton are exceptional in showing controversial evidence of collisional Eburnian–Transamazonian assemblages undisturbed during Late Proterozoic time.

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11

Park, John K., Donald K. Norris, and André Larochelle. "Paleomagnetism and the origin of the Mackenzie Arc of northwestern Canada." Canadian Journal of Earth Sciences 26, no. 11 (November 1, 1989): 2194–203. http://dx.doi.org/10.1139/e89-186.

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Analysis of paleomagnetic data obtained from 1966 alternating-field treatment and from recent thermal demagnetization of the same samples of Late Proterozoic (770 Ma) diabase sills and dykes distributed about the Mackenzie Arc from northeastern British Columbia to the Alaskan border has revealed a primary magnetization in seven sites that is similar to existing data from 10 sites confined to the central Mackenzie Mountains region (N = 17 site poles; 222.2°W, 01.6°N; R = 16.73; K = 60; A95 = 5°). The diabases are confined to the dominantly clastic Late Proterozoic Tsezotene Formation and Katherine Group of the Mackenzie Mountains Supergroup. Tests of Carey's orocline hypothesis for the arc using linear regression and a plan-view application of the fold test suggest, in line with earlier structural studies, that the arc is largely nonrotational and that it is not an orocline resulting from the Cretaceous and early Tertiary Laramide Orogeny. Rather, it conforms to the arcuate foreland margin predating deposition of the Late Proterozoic Mackenzie Mountains Supergroup.

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12

Clemmensen, L. B., and H. F. Jepsen. "Lithostratigraphy and geological setting of Upper Proterozoic shoreline-shelf deposits, Hagen Fjord Group, eastern North Greenland." Rapport Grønlands Geologiske Undersøgelse 157 (January 1, 1992): 1–27. http://dx.doi.org/10.34194/rapggu.v157.8195.

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During the Late Proterozoic a more than 1000 m thick succession of sediments was deposited on the shelf fringing the north-eastern corner of the Greenland craton. These sediments were classified together with an underlying turbidite sequence in the Hagen Fjord Group (Haller, 1961), which is here redefined to contain only Upper Proterozoic, mainly shallow marine shelf deposits outcropping between Independence Fjord and Kronprins Christian Land in eastern North Greenland. Both siliciclastic and carbonate sedimentation occurred during the Late Proterozoic, and the changing tectonic environment along the northern and eastern shelf-margin of Greenland at that time is well recorded within the sediment sequence. Correlation of the Hagen Fjord Group with similar shelf deposits elsewhere along the eastern and northern margin of the Canadian-Greenlandian Shield is discussed.

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13

Dostal, J., and C. Dupuy. "Gold in late Proterozoic andesites from northwestern Africa." Economic Geology 82, no. 3 (May 1, 1987): 762–66. http://dx.doi.org/10.2113/gsecongeo.82.3.762.

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14

Dang, D. H., W. Wang, T. M. Gibson, M. Kunzmann, M. B. Andersen, G. P. Halverson, and R. D. Evans. "Authigenic uranium isotopes of late Proterozoic black shale." Chemical Geology 588 (January 2022): 120644. http://dx.doi.org/10.1016/j.chemgeo.2021.120644.

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15

Aitken, J. D. "Two Late Proterozoic glaciations, Mackenzie Mountains, northwestern Canada." Geology 19, no. 5 (1991): 445. http://dx.doi.org/10.1130/0091-7613(1991)019<0445:tlpgmm>2.3.co;2.

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16

Young, Grant M. "Late Proterozoic stratigraphy and the Canada-Australia connection." Geology 20, no. 3 (1992): 215. http://dx.doi.org/10.1130/0091-7613(1992)020<0215:lpsatc>2.3.co;2.

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17

Kaz'min, V. G., and Yu T. Sukhorukov. "THE LATE PROTEROZOIC ACTIVE MARGIN IN EAST AFRICA." International Geology Review 30, no. 11 (November 1988): 1162–71. http://dx.doi.org/10.1080/00206818809466098.

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18

Pallister, John S., John S. Stacey, Lynn B. Fischer, and Wayne R. Premo. "Arabian Shield ophiolites and Late Proterozoic microplate accretion." Geology 15, no. 4 (1987): 320. http://dx.doi.org/10.1130/0091-7613(1987)15<320:asoalp>2.0.co;2.

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19

Kim, Yongin, and Yong Il Lee. "A new Late Proterozoic stratum in South Korea." Geosciences Journal 7, no. 1 (March 2003): 47–52. http://dx.doi.org/10.1007/bf02910264.

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20

ABDELSALAM, M. G., and R. J. STERN. "Structure of the late Proterozoic Nakasib suture, Sudan." Journal of the Geological Society 150, no. 6 (November 1993): 1065–74. http://dx.doi.org/10.1144/gsjgs.150.6.1065.

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21

Vidal, Gonzalo. "The late Proterozoic acritarch Chuaria circularis (Walcott) Vidal and Ford." Journal of Paleontology 64, no. 3 (May 1990): 488. http://dx.doi.org/10.1017/s0022336000018825.

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Vidal and Ford (1985) described a rich, well-preserved acritarch biota from the late Proterozoic Chuar Group in northern Arizona. The biota includes Chuaria circularis (Walcott) Vidal and Ford, whose diagnosis was emended. A SEM micrograph of a specimen supposedly deriving from the Kwagunt Formation of the Chuar Group was included (Vidal and Ford, 1985, p. 357). However, the figured specimen derives from the Late Proterozoic Eleonore Bay Group in east Greenland (Vidal, 1979, Pl. 4, a, b) and was erroneously included as a consequence of an inadvertent replacement of films during the preparation of paper prints for publication. The author of this note alone bears responsibility for this regrettable mistake.

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22

Bluck, B. J., W. Gibbons, and J. K. Ingham. "Terranes." Geological Society, London, Memoirs 13, no. 1 (1992): 1–4. http://dx.doi.org/10.1144/gsl.mem.1992.013.01.03.

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AbstractThe Precambrian and Lower Palaeozoic foundations of the British Isles may be viewed as a series of suspect terranes whose exposed boundaries are prominent fault systems of various kinds, each with an unproven amount of displacement. There are indications that they accreted to their present configuration between late Precambrian and Carboniferous times. From north to south they are as follows.In northwest Scotland the Hebridean terrane (Laurentian craton in the foreland of the Caledonian Orogen) comprises an Archaean and Lower Proterozoic gneissose basement (Lewisian) overlain by an undeformed cover of Upper Proterozoic red beds and Cambrian to early mid Ordovician shallow marine sediments. The terrane is cut by the Outer Isles Thrust, a rejuvenated Proterozoic structure, and is bounded to the southeast by the Moine Thrust zone, within the hanging wall of which lies a Proterozoic metamorphic complex (Moine Supergroup) which constitutes the Northern Highlands terrane. The Moine Thrust zone represents an essentially orthogonal closure of perhaps 100 km which took place during Ordovician-Silurian times (Elliott & Johnson 1980). The Northern Highlands terrane records both Precambrian and late Ordovician to Silurian tectonometamorphic events (Dewey & Pankhurst 1970) and linkage with the Hebridean terrane is provided by slices of reworked Lewisian basement within the Moine Supergroup (Watson 1983).To the southwest of the Great Glen-Walls Boundary Fault system lies the Central Highlands (Grampian) terrane, an area dominated by the late Proterozoic Dalradian Supergroup which is underlain by a gneissic complex (Central Highland Granulites) that has been variously interpreted as either older

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23

Baadsgaard, H., A. P. Nutman, M. Rosing, and D. Bridgwater. "A late Archaean pegmatite dyke swarm from the Isukasia area, southern West Greenland." Rapport Grønlands Geologiske Undersøgelse 125 (December 31, 1985): 48–51. http://dx.doi.org/10.34194/rapggu.v125.7889.

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The Isukasia area is dominated by early Archaean rocks that have been discussed extensively in the geological literature (Nutman et al., 1983). These rocks were deformed and recrystallised under amphibolite facies conditions during the late Archaean regional duetile deformation (Bridgwater et al., 1976; Nutman et al., 1983). The pegmatite dykes discussed here post-date this event but were succeeded by Proterozoic basic dykes, rare granitic sheets (Kalsbeek et al., 1980; Kalsbeek & Taylor, 1983), and then by Proterozoic faulting.

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24

Zhang, Huimin. "Preliminary Proterozoic apparent polar wander paths for the South China Block and their tectonic implications." Canadian Journal of Earth Sciences 35, no. 3 (March 1, 1998): 302–20. http://dx.doi.org/10.1139/e97-117.

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Results of a regional paleomagnetic study of Precambrian rocks in central-east China are summarized and interpreted. The study is a partial outcome of a geoscience transect incorporating three terranes, namely the Yangzi, Jiangnan, and Huaxia blocks. Paleomagnetic poles derived from a range of metamorphic, igneous, and sedimentary rocks define a northeast to southwest swath crossing the present Pacific Ocean and interpreted to embrace Early to Late Proterozoic times. All three terranes define segments of the same swath and correlate with a similar apparent polar wander path previously defined from the North China Block. The results imply that the constituent blocks of eastern China formed a united block during Early to Middle Proterozoic times. Later relatively large fragmentation is confirmed by Late Proterozoic apparent polar wander path records of the North China and South China Blocks.

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25

Friderichsen, J. D., N. Henriksen, and R. A. Strachan. "Basement-cover relationships and regional structure in the Grandjean Fjord - Bessel Fjord region (75°–76°N), North-East Greenland." Rapport Grønlands Geologiske Undersøgelse 162 (January 1, 1994): 17–33. http://dx.doi.org/10.34194/rapggu.v162.8246.

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Geological mapping and isotopic investigations demonstrate that the Grandjean Fjord – Bessel Fjord region can be divided into three rock groups: (1) a Lower Proterozoic basement gneiss complex; (2) a Middle Proterozoic supracrustal cover (Smallefjord sequence); and (3) Upper Proterozoic metasediments (Eleonore Bay Supergroup). The basement gneiss complex largely comprises c. 2.0–1.7 Ga calc-alkaline granitoid orthogneisses with intercalated migmatitic supracrustal rocks. The complex is deformed by at least two sets of approximately coaxial folds which may be either Proterozoic or Caledonian in age. The Smallefjord sequence is comprised mostly of migmatitic schists and gneisses which underwent high-grade metamorphism during the late Middle Proterozoic. The dominant deformation structures within the Smallefjord sequence are associated with the development of ductile shear zones along the boundaries of all the major tectonostratigraphic units and are thought to be Caledonian in age.

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Parrish, R. R., and I. Reichenbach. "Age of xenocrystic zircon from diatremes of western Canada." Canadian Journal of Earth Sciences 28, no. 8 (August 1, 1991): 1232–38. http://dx.doi.org/10.1139/e91-110.

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Numerous diatremes of middle and late Paleozoic age intrude miogeoclinal middle and lower Paleozoic strata in the Canadian Cordillera. In addition to abundant crustal xenoliths and conspicuous mantle-derived mineral xenocrysts, rare zircon grains are present. U–Pb dating of single zircon crystals from many of these diatremes has failed to identify the presence of cogenetic (magmatic) zircons. All dated zircon grains are interpreted as xenocrysts derived from the crust. Their morphologies range from euhedral to very rounded, and their ages range from early Paleozoic to Archean. Most ages fall between 1.8 and 2.1 Ga, with subordinate age groupings in the late Archean (ca. 2.6 Ga), Middle Proterozoic (1.0–1.1 Ga), and early Paleozoic (ca. 470 Ma, 530 Ma). The Proterozoic and Archean zircons could have been derived from either the crystalline basement or its overlying sedimentary cover of Late Proterozoic to early Paleozoic age. Paleozoic zircons were probably derived from either intrusions within the basement or sills that intrude the early Paleozoic sedimentary cover, and they signify magmatic activity possibly related to rifting of the continental margin.

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27

Taylor, Ian E., and Gerard V. Middleton. "Aeolian sandstones in the Copper Harbor Formation, Late Proterozoic, Lake Superior basin." Canadian Journal of Earth Sciences 27, no. 10 (October 1, 1990): 1339–47. http://dx.doi.org/10.1139/e90-144.

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Sandstones with cross-sets up to 1.5 m thick occur within the Copper Harbor Formation, most prominently at Five Mile Point. In contrast to intercalated sandstones with smaller scale cross-stratification or horizontal lamination, pebbles are very scarce in the large-scale cross-stratified sandstones and, where present, are restricted to set bases. The large-scale cross-stratified sandstones are better sorted than intercalated sandstones and show a mean palaeocurrent direction at 90° to the mean for the interbedded sandstones.The large-scale cross-stratified sandstones are interpreted as the product of fields of small transverse aeolian dunes that formed on dry parts of alluvial fans bordering the Keweenawan rift. The aeolian palaeocurrent mean is along the rift valley, and tentatively may be interpreted as the result of topographically constrained palaeo-tradewinds.

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Seranne, Michel, Olivier Bruguier, and Mathieu Moussavou. "U-Pb single zircon grain dating of Present fluvial and Cenozoic aeolian sediments from Gabon: consequences on sediment provenance, reworking, and erosion processes on the equatorial West African margin." Bulletin de la Société Géologique de France 179, no. 1 (January 1, 2008): 29–40. http://dx.doi.org/10.2113/gssgfbull.179.1.29.

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Abstract U-Pb ages obtained from detrital zircon from terrigenous sediments are used to determine the sources. Present fluvial sand-bars of the Ogooué river yield age spectra of detrital zircons in agreement with Archean and Early Proterozoic sources found in the drainage. The large proportion of Late Proterozoic zircons cannot be derived from primary erosion of the watershed basement rocks, since there is no formation of that age in the area. This later group of zircons is in good agreement with reworking of the aeolian Paleogene Batéké Sands, by regressive erosion in the upper reaches of the Ogooué river, as they contain a majority of Late Proterozoic age zircons. The sources of Late Proterozoic zircons in the Batéké Sand are very distant, and transported and reworked – at least in part – by aeolian processes. Our results, together with the widely distributed Paleogene sediments over continental Africa, suggests that Paleogene was a time of subdued erosion of the cratonic areas and extensive reworking, transport and deposition within continental Africa. In contrast, our results from the Ogooué river indicate active present incision of the cratonic area, erosion of the previous continental sediments, and export of the river bed-load to the continental margin. This temporal evolution of erosion-transport-deposition is correlated with the drastic climate change that occurred during the Cenozoic, leading to a more efficient mechanical erosion, and it correlates with the increase of terrigenous flux to the margin, observed during the Neogene.

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Xiping, Dong, Andrew H. Knoll, and Jere H. Lipps. "Late Cambrian Radiolaria from Hunan, China." Journal of Paleontology 71, no. 5 (September 1997): 753–58. http://dx.doi.org/10.1017/s002233600003571x.

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Well-preserved polycystine radiolarians, representing a new species in the family Entactiniidae, were recovered from subtidal micrites and bioclastic micrites of the Upper Cambrian (Glyptagnostus reticulatustrilobite zone) Bitiao Formation, western Hunan, China. Confirming earlier, questionable reports of Cambrian Radiolaria, these fossils place the first appearance of the group somewhat before its Ordovician emergence as a principal constituent of the oceanic silica cycle, but long after the Proterozoic diversification of protists.

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Raeside, Robert P., and Sandra M. Barr. "Geology and tectonic development of the Bras d'Or suspect terrane, Cape Breton Island, Nova Scotia." Canadian Journal of Earth Sciences 27, no. 10 (October 1, 1990): 1371–81. http://dx.doi.org/10.1139/e90-147.

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The Bras d'Or Terrane is defined in Cape Breton Island and consists of four distinctive components, (i) Low-pressure, regionally metamorphosed aluminous and calcareous gneiss of the Proterozoic Bras d'Or metamorphic suite is restricted to the southeastern part of the terrane. (ii) Late Proterozoic clastic-volcanic-carbonate units (Blues Brook, Malagawatch, McMillan Flowage, and Benacadie Brook formations, and Barachois River and Bateman Brook metamorphic suites) occur throughout the terrane and are generally at low metamorphic grades, although sillimanite grade has locally been achieved, (iii) A suite of 555–565 Ma calc-alkalic dioritic to granitic plutons was emplaced at pressures ranging from about 900 to less than 100 MPa. (iv) Early Ordovician granitic plutonism and Ordovician 40Ar/39Ar ages record regional heating.The Bras d'Or Terrane docked with the Mira Terrane to the southeast no earlier than the Ordovician. Cambro-Ordovician sedimentary rocks of the Mira Terrane appear locally to be thrust over the Bras d'Or Terrane. Mississippian sedimentary rocks overlap both terranes. The present boundary, the Macintosh Brook Fault, is mainly a Carboniferous feature. Docking with the Aspy Terrane to the northwest occurred along the Eastern Highlands shear zone and is constrained by a 375 Ma stitching pluton, the Black Brook Granitic Suite. Docking may have been initiated as early as 415 Ma, as indicated by reset 40Ar/39Ar ages near the boundary. The three Proterozoic components of the Bras d'Or Terrane have been recognized in the Brookville Terrane of southern New Brunswick, and Late Proterozoic gneiss, Late Proterozoic – early Cambrian calc-alkalic plutons and Ordovician granitic plutons have been reported in parts of the Hermitage Flexure of southern Newfoundland. The Bras d'Or Terrane may therefore be a regionally significant component of the northern Appalachian Orogen.

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Doughty, P. T., R. A. Price, and R. R. Parrish. "Geology and U-Pb geochronology of Archean basement and Proterozoic cover in the Priest River complex, northwestern United States, and their implications for Cordilleran structure and Precambrian continent reconstructions." Canadian Journal of Earth Sciences 35, no. 1 (January 1, 1998): 39–54. http://dx.doi.org/10.1139/e97-083.

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Precambrian basement rocks exposed within tectonic windows in the North American Cordillera help to define the Precambrian crustal structure of western North America and possible reconstructions of the Late Proterozoic supercontinent Rodinia. New geologic mapping and U-Pb dating in the infrastructure of the Priest River metamorphic complex, northern Idaho, documents the first Archean basement (2651 ± 20 Ma) north of the Snake River Plain in the North American Cordillera. The Archean rocks are exposed in the core of an antiform and mantled by a metaquartzite that may represent the nonconformity between basement and the overlying Hauser Lake gneiss, which is correlated with the Prichard Formation of the Belt Supergroup. A structurally higher sheet of augen gneiss interleaved with the Hauser Lake gneiss yields a U-Pb zircon crystallization age somewhat greater than 1577 Ma. The slivers of augen gneiss were tectonically interleaved with the surrounding Hauser Lake gneiss near the base of the Spokane dome mylonite zone, which arches across this part of the Priest River complex. We conclude that the Spokane dome mylonite zone lies above the Archean basement-cover contact and that it was, in part, equivalent to the basal décollement of the Rocky Mountain fold and thrust belt. New U-Pb dates on metamorphic monazite and xenotime reveal peak metamorphism at ca. 72 Ma, compatible with movement along the Spokane dome mylonite zone at that time. The Archean basement could be interpreted as the western extension of the Hearne province, or a new Archean basement terrane separated from the Hearne province by an Early Proterozoic suture. The unique assemblage of 2.65 Ga basement, ~1.58 Ga felsic intrusive rocks, and the Middle Proterozoic Belt Supergroup can be used as a piercing point for the identification of the conjugate margin to Laurentia. Our new dating supports previous correlations of Australia's Gawler craton (2.55-2.65 Ga) and its 1590 Ma plutons with the Priest River complex basement gneisses. The Priest River complex basement may be a piece of eastern Australia stranded during rifting of the supercontinent Rodina in the Late Proterozoic.

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Elicki, Olaf, Ulf Linnemann, Mandy Hofmann, Johannes Zieger, Andreas Gärtner, Daniel Klein, and Tim Meischner. "Zircon geochronology and provenance of the late Proterozoic and early Palaeozoic of southwestern Jordan." Zeitschrift der Deutschen Gesellschaft für Geowissenschaften 171, no. 2 (July 2, 2020): 105–20. http://dx.doi.org/10.1127/zdgg/2020/0217.

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Armstrong, Richard Lee, Randall R. Parrish, Peter van der Heyden, Krista Scott, Dita Runkle, and Richard L. Brown. "Early Proterozoic basement exposures in the southern Canadian Cordillera: core gneiss of Frenchman Cap, Unit I of the Grand Forks Gneiss, and the Vaseaux Formation." Canadian Journal of Earth Sciences 28, no. 8 (August 1, 1991): 1169–201. http://dx.doi.org/10.1139/e91-107.

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The protolith age of high-grade metamorphic rocks exposed in structurally deep parts of the Omineca Crystalline Belt has been the subject of investigation and controversy for decades. We have applied multiple isotopic dating techniques to rocks of three structural culminations: the Monashee complex (which includes the Frenchman Cap and Thor–Odin gneiss domes), the Grand Forks horst, and the Vaseaux Formation, which lies in the footwall of the Okanagan Valley fault.Frenchman Cap core gneisses contain highly radiogenic Sr that scatters about a 2206 ± 117 Ma (1σ) Rb–Sr isochron with 87Sr/86Sr initial ratio of 0.700 ± 0.002. Monazite and zircon dates for the same rocks are 1851 ± 7 to 2103 ± 16 Ma (only U–Pb dates are given with 2σ errors), with lower intercepts from about 100 to 300 Ma. Sm–Nd whole-rock and crustal-residence (TDM) dates are 2.3 ± 0.2 Ga. Mafic–felsic layering in the core gneiss is also of Early Proterozoic age. There is no geochronometric evidence for Late Proterozoic or Mesozoic migmatization.Frenchman Cap mantling gneisses, including samples from above the Monashee décollement, have radiogenic Sr and unradiogenic Nd compositions that are not consistent with current inferences of a Late Proterozoic to Paleozoic depositional age. Two intrusive granitic rocks, which cut mantling gneiss, are either Early Proterozoic or Mesozoic–Cenozoic with a Proterozoic Sr isotopic signature acquired by assimilation of core gneiss. One other intrusive studied is probably Paleocene Ladybird granite. The age of the mantling gneiss is not yet consistently resolved.Grand Forks Gneiss Unit I paragneiss gives radiogenic whole-rock Sr, zircon U–Pb upper intercept, and Sm–Nd whole-rock crustal-residence dates of 1.7 ± 0.4 Ga, 1681 ± 3 Ma (2σ, but the apparent high precision is very dependent on the assumption made about the time of Pb loss), and 1.9 ± 0.3 Ga, respectively. Unit II and younger Grand Forks Gneiss units are Late Proterozoic or Phanerozoic. All isotope systems have been considerably reset on a centimetre to metre scale by Mesozoic–Cenozoic regional metamorphism. Grand Forks Sr, Pb, and Nd isotope data are much like those for Spokane area pre-Purcell basement.Vaseaux Formation micaceous schist and gneiss give radiogenic whole-rock Sr, zircon U–Pb upper intercept, and Sm–Nd crustal-residence dates of 2.1 ± 0.6 Ga, 1899 ± 49 Ma (2σ), and 2.2 ± 0.1 Ga, respectively. Hornblende-bearing schist and gneiss contain much less radiogenic Sr and more radiogenic Nd. The latter are either tectonic intercalations of Late Proterozoic to Paleozoic eugeosynclinal rocks or Mesozoic–Cenozoic mixtures of mantle-derived magma and older crustal rock. The Vaseaux Formation paragneiss is similar isotopically to paragneiss in the Frenchman Cap core gneiss. This may indicate a similar age, or that Vaseaux sedimentary rocks could be much younger and isochemically derived from a basement of Frenchman Cap character. The first alternative is favored because the three isotope systems are usually not preserved in unison through sedimentary processes. Sr isotopes, in particular, do not usually preserve a provenance age.In all three areas, late Mesozoic to early Cenozoic metamorphic monazite, hornblende, muscovite, and biotite dates provide a record of cooling from a Cretaceous to Paleocene culmination of regional metamorphism, with particularly rapid cooling during Paleocene to Eocene crustal extension and tectonic unroofing.The localities studied are tectonic windows on structural culminations that expose basement that we infer to be part of North America. Their ages fit the pattern of basement ages established for the stable craton. Their extent is consistent with the reconstruction of compressed miogeoclinal rocks. The eastern half of the Cordilleran region on both sides of the United States – Canada border is underlain by Early Proterozoic basement that was attenuated in Late Proterozoic time, compressed during Mesozoic–Cenozoic orogeny, and finally extended in early Cenozoic collapse of the thickened crust. During Mesozoic–Cenozoic orogeny the sedimentary cover of that basement was pushed approximately 200 km eastward and replaced by allochthonous terranes. The tectonic displacements documented in the southern Canadian Cordillera are truly exceptional.

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34

Belperio, A. P. "Geological note: Hydrocarbon potential of Late Proterozoic graben sediments." Australian Journal of Earth Sciences 34, no. 3 (September 1987): 403–4. http://dx.doi.org/10.1080/08120098708729420.

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35

Ding, P., P. R. James, and M. Sandiford. "Late proterozoic deformation in the Amadeus Basin, Central Australia." Australian Journal of Earth Sciences 39, no. 4 (September 1992): 495–500. http://dx.doi.org/10.1080/08120099208728041.

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36

Bjørnerud, M., C. Craddock, and C. J. Wills. "A major late Proterozoic tectonic event in southwestern Spitsbergen." Precambrian Research 48, no. 1-2 (August 1990): 157–65. http://dx.doi.org/10.1016/0301-9268(90)90060-4.

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de Brito Neves, Benjamin Bley, and Umberto G. Cordani. "Tectonic evolution of South America during the Late Proterozoic." Precambrian Research 53, no. 1-2 (October 1991): 23–40. http://dx.doi.org/10.1016/0301-9268(91)90004-t.

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38

Van der Voo, Rob, and Joseph G. Meert. "Late Proterozoic paleomagnetism and tectonic models: a critical appraisal." Precambrian Research 53, no. 1-2 (October 1991): 149–63. http://dx.doi.org/10.1016/0301-9268(91)90009-y.

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39

Shimron, A. E. "The Red Sea line — a Late Proterozoic transcurrent fault." Journal of African Earth Sciences (and the Middle East) 11, no. 1-2 (January 1990): 95–112. http://dx.doi.org/10.1016/0899-5362(90)90080-x.

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40

VIDAL, GONZALO. "Are late Proterozoic carbonaceous megafossils metaphytic algae or bacteria?" Lethaia 22, no. 4 (October 1989): 375–79. http://dx.doi.org/10.1111/j.1502-3931.1989.tb01437.x.

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41

Chumakov, Nicolai M., and Donald P. Elston. "The Paradox of Late Proterozoic Glaciations at Low Latitudes." Episodes 12, no. 2 (June 1, 1989): 115–20. http://dx.doi.org/10.18814/epiiugs/1989/v12i2/015.

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42

BLASBAND, B., S. WHITE, P. BROOIJMANS, H. DE BOORDER, and W. VISSER. "Late Proterozoic extensional collapse in the Arabian–Nubian Shield." Journal of the Geological Society 157, no. 3 (May 2000): 615–28. http://dx.doi.org/10.1144/jgs.157.3.615.

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43

Streepey, M. M., B. A. van der Pluijm, E. J. Essene, C. M. Hall, and J. F. Magloughlin. "Late Proterozoic (ca. 930 Ma) extension in eastern Laurentia." Geological Society of America Bulletin 112, no. 10 (October 2000): 1522–30. http://dx.doi.org/10.1130/0016-7606(2000)112<1522:lpcmei>2.0.co;2.

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44

Fitches, W. R., A. C. Ajibade, I. G. Egbuniwe, R. W. Holt, and J. B. Wright. "Late Proterozoic schist belts and plutonism in NW Nigeria." Journal of the Geological Society 142, no. 2 (March 1985): 319–37. http://dx.doi.org/10.1144/gsjgs.142.2.0319.

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45

Tianfeng, Wan, and Zhu Hong. "Tectonic events of Late Proterozoic-Triassic in South China." Journal of Southeast Asian Earth Sciences 6, no. 2 (January 1991): 147–57. http://dx.doi.org/10.1016/0743-9547(91)90107-9.

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46

ANDERS, B., T. REISCHMANN, D. KOSTOPOULOS, and U. POLLER. "The oldest rocks of Greece: first evidence for a Precambrian terrane within the Pelagonian Zone." Geological Magazine 143, no. 1 (October 20, 2005): 41–58. http://dx.doi.org/10.1017/s0016756805001111.

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The Pelagonian Zone in Greece represents the westernmost belt of the Hellenide hinterland (Internal Hellenides). Previous geochronological studies of basement rocks from the Pelagonian Zone have systematically yielded Permo-Carboniferous ages. In this study we demonstrate, for the first time, the existence of a Precambrian crustal unit within the crystalline basement of the Pelagonian Zone. The U–Pb single-zircon and SHRIMP ages of these orthogneisses vary from 699 ± 7 Ma to 713 ± 18 Ma, which identify them as the oldest rocks in Greece. These Late Proterozoic rocks, which today occupy an area of c. 20 × 100 km, are significantly different from the neighbouring rocks of the Pelagonian Zone. They are therefore interpreted as delineating a terrane, named here the Florina Terrane. During the Permo-Carboniferous, Florina was incorporated into an active continental margin, where it formed part of the basement for the Pelagonian magmatic arc. The activity of this arc was dated in this study by single-zircon Pb/Pb ages as having taken place at 292 ± 5 Ma and 298 ± 7 Ma. During the Alpine orogeny, Florina, together with the Pelagonian Zone, eventually became a constituent of the Hellenides. Geochemically, the Florina orthogneisses represent granites formed at an active continental margin. Because of the Late Proterozoic ages, this Late Proterozoic active continental margin can be correlated to a Pan-African or Cadomian arc. As the gneisses contain inherited zircons of Late to Middle Proterozoic age, the original location of Florina was probably at the northwestern margin of Gondwana. Similar to other Gondwana-derived terranes, such as East Avalonia, Florina approached the southern margin of Eurasia during Palaeozoic times, where it became part of an active continental margin above the subducting Palaeotethys. These interpretations further indicate that terrane accretion was already playing an important role in the early pre-alpine evolution of the Hellenides.

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Stewart, A. D. "Late Proterozoic and Late Palaeozoic movement on the Coigach fault in NW Scotland." Scottish Journal of Geology 29, no. 1 (May 1993): 21–28. http://dx.doi.org/10.1144/sjg29010021.

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48

Doig, Ronald, J. Brendan Murphy, and R. Damian Nance. "Tectonic significance of the Late Proterozoic Economy River gneiss, Cobequid Highlands, Avalon Composite Terrane, Nova Scotia." Canadian Journal of Earth Sciences 30, no. 3 (March 1, 1993): 474–79. http://dx.doi.org/10.1139/e93-035.

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A 734 ± 2 Ma U–Pb (zircon) age for the Economy River orthogneiss, Coboquid Highlands, Nova Scotia, is interpreted as being representative of a regionally extensive ca. 820–660 Ma event that is recorded in many parts of the Late Proterozoic – Early Cambrian Avalon Composite Terrane and the Gondwanan margin. The geochemistry of the gneiss is consistent with an arc environment. Although the gneiss may represent part of the sialic basement to the terrane, field relationships indicate that some of the basement is significantly older. The date may provide a minimum age for the platformal sedimentary rocks (Gamble Brook Formation) that the orthogneiss intruded and thus help constrain the Late Proterozoic paleogeographic position of Avalon relative to Gondwanaland.

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Hanmer, Simon, Michael Williams, and Chris Kopf. "Striding-Athabasca mylonite zone: implications for the Archean and Early Proterozoic tectonics of the western Canadian Shield." Canadian Journal of Earth Sciences 32, no. 2 (February 1, 1995): 178–96. http://dx.doi.org/10.1139/e95-015.

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Study of the northern Saskatchewan–District of Mackenzie segment of the Snowbird tectonic zone suggests that fragments of relatively stiff mid-Archean crust, possibly arc related, have controlled the localization, shape, and complex kinematics of the multistage Striding–Athabasca mylonite zone during the Archean, as well as the geometry of the Early Proterozoic rifted margin of the western Churchill continent. By the late Archean, the Striding–Athabasca mylonite zone was located in the interior of the western Churchill continent, well removed from the contemporaneous plate margins. Except for the Alberta segment, the Snowbird tectonic zone was not the site of an Early Proterozoic plate margin. We suggest that the geometry of the Archean–Early Proterozoic boundary in the western Canadian Shield represents a jagged continental margin, composed of a pair of reentrants defined by rifted and transform segments. These segments were inherited from Early Proterozoic breakup and controlled by the Archean structure of the interior of the western Churchill continent. The geometry of this margin appears to have strongly influenced the Early Proterozoic tectono-magmatic evolution of the western Canadian Shield.

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Dawes, P. R. "Etah meta-igneous complex and the Wulff structure: Proterozoic magmatism and deformation in Inglefield Land, North-West Greenland." Rapport Grønlands Geologiske Undersøgelse 139 (December 31, 1988): 1–24. http://dx.doi.org/10.34194/rapggu.v139.8021.

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A hitherto uninvestigated collection of crystalline rocks from north-eastem Inglefield Land (c. 79°N) allowanew interpretation of the Precambrian geology of the region. The majority of the samples - high-grade basic, intermediate and granitoid rocks - are referred to the Etah meta-igneous complex, which has been shown to be mid-Proterozoic in age in the type area in south-western Inglefield Land. In areas of high deformation there is a gradation from massive rocks of igneous aspect into folded and variably migmatised gneisses. Thus the magmatic complex provides a gauge of the nature and intensity of Proterozoic (Hudsonian) deformation and metamorphism. In Inglefield Land Proterozoic deformation produced different structural styles; thus in the north-east the Wulff structure - a large-scale refolded isoclinal structure - characterises a region that lacks an obvious preferred regional foliation direction, while in the south-west, linear E-W trending belts with steep dips dominate the structural pattem. The Proterozoic evolution is outlined from the formation of the Etah Group, a supracrustal sequence that pre-dates the Etah meta-igneous complex, to uplift, peneplanation, deposition and magmatism in the late Proterozoic. Inglefield Land is not part of the Rinkian mobile belt of West Greenland, and it is stressed that the obvious continuation of the Proterozoic geology is into Ellesmere Island.

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Journal articles on the topic 'Late Proterozoic'

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