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Автор: Grafiati
Опубліковано: 10 грудня 2022
Оновлено: 28 січня 2023

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1

Park, Yuem, Nicholas L. Swanson-Hysell, Scott A. MacLennan, Adam C. Maloof, Mulubrhan Gebreslassie, Marissa M. Tremblay, Blair Schoene, et al. "The lead-up to the Sturtian Snowball Earth: Neoproterozoic chemostratigraphy time-calibrated by the Tambien Group of Ethiopia." GSA Bulletin 132, no. 5-6 (October 17, 2019): 1119–49. http://dx.doi.org/10.1130/b35178.1.

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Abstract The Tonian-Cryogenian Tambien Group of northern Ethiopia is a mixed carbonate-siliciclastic sequence that culminates in glacial deposits associated with the first of the Cryogenian glaciations—the Sturtian “Snowball Earth.” Tambien Group deposition occurred atop arc volcanics and volcaniclastics of the Tsaliet Group. New U-Pb isotope dilution–thermal ionization mass spectrometry (ID-TIMS) dates demonstrate that the transition between the Tsaliet and Tambien Groups occurred at ca. 820 Ma in western exposures and ca. 795 Ma in eastern exposures, which is consistent with west to east arc migration and deposition in an evolving back-arc basin. The presence of intercalated tuffs suitable for high-precision geochronology within the Tambien Group enable temporal constraints on stratigraphic data sets of the interval preceding, and leading into, the Sturtian glaciation. Recently discovered exposures of Sturtian glacial deposits and underlying Tambien Group strata in the Samre Fold-Thrust Belt present the opportunity to further utilize this unique association of tuffs and carbonate lithofacies. U-Pb ID-TIMS ages from zircons indicate that Tambien Group carbonates were deposited from ca. 820 Ma until 0–2 m.y. before the onset of the Sturtian glaciation, making the group host to a relatively complete carbonate stratigraphy leading into this glaciation. New δ13C and 87Sr/86Sr data and U-Pb ID-TIMS ages from the Tambien Group are used in conjunction with previously published isotopic and geochronologic data to construct newly time-calibrated composite Tonian carbon and strontium isotope curves. Tambien Group δ13C data and U-Pb ID-TIMS ages reveal that a pre-Sturtian sharp negative δ13C excursion (referred to as the Islay anomaly in the literature) precedes the Sturtian glaciation by ∼18 m.y., is synchronous in at least two separate basins, and is followed by a prolonged interval of positive δ13C values. The composite Tonian 87Sr/86Sr curve shows that, following an extended interval of low and relatively invariant values, inferred seawater 87Sr/86Sr rose ca. 880–770 Ma, then subsequently decreased leading up to the ca. 717 Ma initiation of the Sturtian glaciation. These data, when combined with a simple global weathering model and analyses of the timing and paleolatitude of large igneous province eruptions and arc accretion events, suggest that the 87Sr/86Sr increase was influenced by increased subaerial weathering of radiogenic lithologies as Rodinia rifted apart at low latitudes. The following 87Sr/86Sr decrease is consistent with enhanced subaerial weathering of arc lithologies accreting in the tropics over tens of millions of years, lowering pCO2 and contributing to the initiation of the Sturtian glaciation.
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2

Rooney, Alan D., Chuan Yang, Daniel J. Condon, Maoyan Zhu, and Francis A. Macdonald. "U-Pb and Re-Os geochronology tracks stratigraphic condensation in the Sturtian snowball Earth aftermath." Geology 48, no. 6 (March 13, 2020): 625–29. http://dx.doi.org/10.1130/g47246.1.

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Abstract The snowball Earth hypothesis predicts a strong hysteresis resulting in discrete multi-million-year glaciations followed by globally synchronous deglaciation. Here we present new U-Pb zircon and Re-Os sedimentary rock geochronology and Os isotope chemostratigraphy from post-Sturtian sequences in south China to test the synchroneity of deglaciation. High-precision chemical abrasion–isotope dilution–thermal ionization mass spectrometry (CA-ID-TIMS) U-Pb zircon dates refine the minimum age of deglaciation to 660.98 ± 0.74 Ma, which is ∼2 m.y. older than previously reported. We also provide a new maximum age constraint on the onset of the Marinoan glaciation of 657.17 ± 0.78 Ma. A global compilation of new Os isotope chemostratigraphy reveals a large and systematic trend to unradiogenic values over <1 m of stratigraphy. Together, these data indicate that the Mn-carbonates in south China are not cap carbonates that formed as a response to post-snowball alkalinity, but are authigenic carbonates that formed millions of years after deglaciation. Sturtian cap carbonates tend to be absent or more condensed than their younger Marinoan counterparts. We suggest that this reflects a combination of enhanced accommodation space in early Cryogenian underfilled rift basins, stronger hysteresis, larger ice volume, and/or higher CO2 levels needed for deglaciation of the longer Sturtian glaciation. Further, our findings indicate that the apparent diachroneity of deglaciation can be explained readily as a consequence of stratigraphic condensation, itself due to the large post-Sturtian glacioeustatic transgressive sequence that outpaced shallow-water carbonate deposition.
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3

Goddéris, Y., Y. Donnadieu, A. Nédélec, B. Dupré, C. Dessert, A. Grard, G. Ramstein, and L. M. François. "The Sturtian ‘snowball’ glaciation: fire and ice." Earth and Planetary Science Letters 211, no. 1-2 (June 2003): 1–12. http://dx.doi.org/10.1016/s0012-821x(03)00197-3.

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4

Isakson, Vincent H., Mark D. Schmitz, Carol M. Dehler, Francis A. Macdonald, and W. Adolph Yonkee. "A robust age model for the Cryogenian Pocatello Formation of southeastern Idaho (northwestern USA) from tandem in situ and isotope dilution U-Pb dating of volcanic tuffs and epiclastic detrital zircons." Geosphere 18, no. 2 (February 18, 2022): 825–49. http://dx.doi.org/10.1130/ges02437.1.

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Abstract Tandem in situ and isotope dilution U-Pb analysis of zircons from pyroclastic volcanic rocks and both glacial and non-glacial sedimentary strata of the Pocatello Formation (Idaho, northwestern USA) provides new age constraints on Cryogenian glaciation in the North American Cordillera. Two dacitic tuffs sampled within glacigenic strata of the lower diamictite interval of the Scout Mountain Member yield high-precision chemical abrasion isotope dilution U-Pb zircon eruption and depositional ages of 696.43 ± 0.21 and 695.17 ± 0.20 Ma. When supplemented by a new high-precision detrital zircon maximum depositional age of ≤670 Ma for shoreface and offshore sandstones unconformably overlying the lower diamictite, these data are consistent with correlation of the lower diamictite to the early Cryogenian (ca. 717–660 Ma) Sturtian glaciation. These 670–675 Ma zircons persist in beds above the upper diamictite and cap dolostone units, up to and including a purported “reworked fallout tuff,” which we instead conclude provides only a maximum depositional age of ≤673 Ma from epiclastic volcanic detritus. Rare detrital zircons as young as 658 Ma provide a maximum depositional age for the upper diamictite and overlying cap dolostone units. This new geochronological framework supports litho- and chemostratigraphic correlations of the lower and upper diamictite intervals of the Scout Mountain Member of the Pocatello Formation with the Sturtian (716–660 Ma) and Marinoan (≤650–635 Ma) low-latitude glaciations, respectively. The Pocatello Formation thus contains a more complete record of Cryogenian glaciations than previously postulated.
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5

MacLennan, Scott A., Michael P. Eddy, Arthur J. Merschat, Akshay K. Mehra, Peter W. Crockford, Adam C. Maloof, C. Scott Southworth, and Blair Schoene. "Geologic evidence for an icehouse Earth before the Sturtian global glaciation." Science Advances 6, no. 24 (June 2020): eaay6647. http://dx.doi.org/10.1126/sciadv.aay6647.

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Snowball Earth episodes, times when the planet was covered in ice, represent the most extreme climate events in Earth’s history. Yet, the mechanisms that drive their initiation remain poorly constrained. Current climate models require a cool Earth to enter a Snowball state. However, existing geologic evidence suggests that Earth had a stable, warm, and ice-free climate before the Neoproterozoic Sturtian global glaciation [ca. 717 million years (Ma) ago]. Here, we present eruption ages for three felsic volcanic units interbedded with glaciolacustrine sedimentary rocks from southwest Virginia, USA, that demonstrate that glacially influenced sedimentation occurred at tropical latitudes ca. 751 Ma ago. Our findings are the first geologic evidence of a cool climate teetering on the edge of global glaciation several million years before the Sturtian Snowball Earth.
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6

Le Heron, Daniel Paul, Nicholas Eyles, and Marie Elen Busfield. "The Laurentian Neoproterozoic Glacial Interval: reappraising the extent and timing of glaciation." Austrian Journal of Earth Sciences 113, no. 1 (January 1, 2020): 59–70. http://dx.doi.org/10.17738/ajes.2020.0004.

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AbstractOne of the major issues in Neoproterozoic geology is the extent to which glaciations in the Cryogenian and Ediacaran periods were global in extent and synchronous or regional in extent and diachronous. A similarly outstanding concern is determining whether deposits are truly glacial, as opposed to gravitationally initiated mass flow deposits in the context of a rifting Rodinia supercontinent. In this paper, we present 115 publically available, quality-filtered chronostratigraphic constraints on the age and duration of Neoproterozoic glacial successions, and compare their palaeocontinental distribution. Depositional ages from North America (Laurentia) clearly support the idea of a substantial glacial epoch between about 720-660 Ma on this palaeocontinent but paradoxically, the majority of Australian glacial strata plot outside the previously proposed global time band for the eponymous Sturtian glaciation, with new dates from China also plotting in a time window previously thought to be an interglacial. For the early Cryogenian, the data permit either a short, sharp 2.4 Ma long global glaciation, or diachronous shifting of ice centres across the Rodinia palaeocontinent, implying regional rather than global ice covers and asynchronous glacial cycles. Thus, based on careful consideration of age constraints, we suggest that strata deposited in the ca. 720-660 Ma window in North America are better described as belonging to a Laurentian Neoproterozoic Glacial Interval (LNGI), given that use of the term Sturtian for a major Neoproterozoic glacial epoch can clearly no longer be justified. This finding is of fundamental importance for reconstructing the Neoproterozoic climate system because chronological constraints do not support the concept of a synchronous panglacial Snowball Earth. Diachroneity of the glacial record reflects underlying palaeotectonic and palaeogeographic controls on the timing of glaciation resulting from the progressive breakup of the Rodinian supercontinent.
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7

Lechte, Maxwell, and Malcolm Wallace. "Sub–ice shelf ironstone deposition during the Neoproterozoic Sturtian glaciation." Geology 44, no. 11 (September 12, 2016): 891–94. http://dx.doi.org/10.1130/g38495.1.

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8

Nagy, Robin M., Susannah M. Porter, Carol M. Dehler, and Yanan Shen. "Biotic turnover driven by eutrophication before the Sturtian low-latitude glaciation." Nature Geoscience 2, no. 6 (May 24, 2009): 415–18. http://dx.doi.org/10.1038/ngeo525.

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9

Lan, Zhongwu, Magdalena H. Huyskens, Kai Lu, Xian-Hua Li, Gangyang Zhang, Dingbiao Lu, and Qing-Zhu Yin. "Toward refining the onset age of Sturtian glaciation in South China." Precambrian Research 338 (March 2020): 105555. http://dx.doi.org/10.1016/j.precamres.2019.105555.

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10

Dzikunoo, Elikplim Abla, Giulio Vignoli, Flemming Jørgensen, Sandow Mark Yidana, and Bruce Banoeng-Yakubo. "New regional stratigraphic insights from a 3D geological model of the Nasia sub-basin, Ghana, developed for hydrogeological purposes and based on reprocessed B-field data originally collected for mineral exploration." Solid Earth 11, no. 2 (March 17, 2020): 349–61. http://dx.doi.org/10.5194/se-11-349-2020.

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Abstract. Reprocessing of regional-scale airborne electromagnetic data is used to build a 3D geological model of the Nasia sub-basin, northern Ghana. The resulting 3D geological model consistently integrates all the prior pieces of information brought by electromagnetic data, lithologic logs, ground-based geophysical surveys, and geological knowledge of the terrain. The geo-modeling process is aimed at defining the lithostratigraphy of the area, chiefly to improve the stratigraphic definition of the area, and for hydrogeological purposes. The airborne electromagnetic measurements, consisting of GEOTEM B-field data, were originally collected for mineral exploration purposes. Thus, those B-field data had to be (re)processed and properly inverted as the original survey and data handling were designed for the detection of potential mineral targets and not for detailed geological mapping. These new geophysical inversion results, compared with the original conductivity–depth images, provided a significantly different picture of the subsurface. The new geophysical model led to new interpretations of the geological settings and to the construction of a comprehensive 3D geo-model of the basin. In this respect, the evidence of a hitherto unexposed system of paleovalleys could be inferred from the airborne data. The stratigraphic position of these paleovalleys suggests a distinctly different glaciation history from the known Marinoan events, commonly associated with the Kodjari formation of the Voltaian sedimentary basin. Indeed, the presence of the paleovalleys within the Panabako may be correlated with mountain glaciation within the Sturtian age, though no unequivocal glaciogenic strata have yet been identified. Pre-Marinoan glaciation is recorded in rocks of the Wassangara group of the Taoudéni Basin. The combination of the Marinoan and, possibly, Sturtian glaciation episodes, both of the Cryogenian period, can be an indication of a Neoproterozoic Snowball Earth. Hence, the occurrence of those geological features not only has important socioeconomic consequences – as the paleovalleys can act as reservoirs for groundwater – but also from a scientific point of view, they could be extremely relevant as their presence would require a revision of the present stratigraphy of the area.
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11

Gumsley, Ashley P., Kevin R. Chamberlain, Wouter Bleeker, Ulf Söderlund, Michiel O. de Kock, Emilie R. Larsson, and Andrey Bekker. "Timing and tempo of the Great Oxidation Event." Proceedings of the National Academy of Sciences 114, no. 8 (February 6, 2017): 1811–16. http://dx.doi.org/10.1073/pnas.1608824114.

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The first significant buildup in atmospheric oxygen, the Great Oxidation Event (GOE), began in the early Paleoproterozoic in association with global glaciations and continued until the end of the Lomagundi carbon isotope excursion ca. 2,060 Ma. The exact timing of and relationships among these events are debated because of poor age constraints and contradictory stratigraphic correlations. Here, we show that the first Paleoproterozoic global glaciation and the onset of the GOE occurred between ca. 2,460 and 2,426 Ma, ∼100 My earlier than previously estimated, based on an age of 2,426 ± 3 Ma for Ongeluk Formation magmatism from the Kaapvaal Craton of southern Africa. This age helps define a key paleomagnetic pole that positions the Kaapvaal Craton at equatorial latitudes of 11° ± 6° at this time. Furthermore, the rise of atmospheric oxygen was not monotonic, but was instead characterized by oscillations, which together with climatic instabilities may have continued over the next ∼200 My until ≤2,250–2,240 Ma. Ongeluk Formation volcanism at ca. 2,426 Ma was part of a large igneous province (LIP) and represents a waning stage in the emplacement of several temporally discrete LIPs across a large low-latitude continental landmass. These LIPs played critical, albeit complex, roles in the rise of oxygen and in both initiating and terminating global glaciations. This series of events invites comparison with the Neoproterozoic oxygen increase and Sturtian Snowball Earth glaciation, which accompanied emplacement of LIPs across supercontinent Rodinia, also positioned at low latitude.
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12

Nelson, Lyle L., Emily F. Smith, Eben B. Hodgin, James L. Crowley, Mark D. Schmitz, and Francis A. Macdonald. "Geochronological constraints on Neoproterozoic rifting and onset of the Marinoan glaciation from the Kingston Peak Formation in Death Valley, California (USA)." Geology 48, no. 11 (July 13, 2020): 1083–87. http://dx.doi.org/10.1130/g47668.1.

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Abstract Death Valley (California, USA) hosts iconic Cryogenian snowball Earth deposits, but the lack of direct geochronological constraints has permitted a variety of correlations and age models. Here, we report two precise zircon U-Pb isotope dilution–thermal ionization mass spectrometry dates for the Kingston Peak Formation: a volcanic eruptive age of 705.44 ± 0.28 Ma from the synglacial Limekiln Spring Member, and a maximum depositional age of 651.69 ± 0.64 Ma from the nonglacial Thorndike submember, which is below the Wildrose diamictite. These dates confirm that the Limekiln Spring and Surprise Members were deposited during the Sturtian glaciation, while the Wildrose submember is a Marinoan glacial deposit, and the overlying Sentinel Peak Member of the Noonday Formation is a Marinoan cap carbonate. Additionally, the age from the Thorndike submember supersedes existing radioisotopic ages from the Datangpo Formation in South China as the youngest constraint on the onset of the Marinoan glaciation, demonstrating that the Cryogenian nonglacial interlude lasted for at least 9 m.y. and the Marinoan glaciation was <17 m.y. long. Cryogenian glaciation in western Laurentia occurred against the backdrop of ∼85 m.y. of episodic rift-related subsidence and magmatism within laterally discontinuous, fault-bound basins.
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13

Zhou, Chuan-Ming, Magdalena H. Huyskens, Shuhai Xiao, and Qing-Zhu Yin. "Refining the termination age of the Cryogenian Sturtian glaciation in South China." Palaeoworld 29, no. 3 (September 2020): 462–68. http://dx.doi.org/10.1016/j.palwor.2020.04.002.

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14

Le Heron, D. P., G. Cox, A. Trundley, and A. Collins. "Sea ice-free conditions during the Sturtian glaciation (early Cryogenian), South Australia." Geology 39, no. 1 (December 3, 2010): 31–34. http://dx.doi.org/10.1130/g31547.1.

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15

Le Hir, G., Y. Goddéris, Y. Donnadieu, and G. Ramstein. "A geochemical modelling study of the evolution of the chemical composition of seawater linked to a "snowball" glaciation." Biogeosciences 5, no. 1 (February 21, 2008): 253–67. http://dx.doi.org/10.5194/bg-5-253-2008.

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Abstract. The Snowball Earth theory initially proposed by Kirschvink (1992) to explain the Neoproterozoic glacial episodes, suggested that the Earth was fully ice-covered at 720 Ma (Sturtian episode) and 640 Ma (Marinoan episode). This succession of extreme climatic crises induced environmental perturbations which are considered as a strong selective pressure on the evolution of life (Hoffman et al., 1998). Using a numerical model of carbon-alkalinity global cycles, we quantify environmental stresses caused by a global glaciation. According to our results, we suggest that during global glaciations, the ocean becomes acidic (pH~6), and undersaturated with respect to carbonate minerals. Moreover the quick transition from ice-house to greenhouse conditions implies an abrupt and large shift of the oceanic surface temperature which causes an extended hypoxia. The intense continental weathering, in the aftermath of the glaciation, deeply affects the seawater composition inducing rapid changes in terms of pH and alkalinity. We also propose a new timing for post glacial perturbations and for the cap carbonates deposition, ~2 Myr instead of 200 kyr as suggested in a previous modelling study. In terms of Precambrian life sustainability, seawater pH modifications appear drastic all along the glaciation, but we suggest that the buffering action of the oceanic crust dissolution avoids a total collapse of biological productivity. But short-lived and large post-glacial perturbations are more critical and may have played the role of an environmental filter proposed in the classic snowball Earth theory. Although the link between environmental changes and life sustainability cannot be modelled accurately, we suggest that only a permissive life (Knoll, 2003) may explain the relative continuity in microfossils diversity observed before, during and after Neoproterozoic glaciation events.
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16

Le Hir, G., Y. Goddéris, Y. Donnadieu, and G. Ramstein. "A geochemical modelling study of the evolution of the chemical composition of seawater linked to a global glaciation: implications for life sustainability." Biogeosciences Discussions 4, no. 3 (June 20, 2007): 1839–76. http://dx.doi.org/10.5194/bgd-4-1839-2007.

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Анотація:
Abstract. The Snowball Earth theory initially proposed by Kirschvink (Kirschvink, 1992) to explain the Neoproterozoic glacial episodes, suggested that the Earth was fully ice-covered at 720 My (Sturtian episode) and 640 My (Marinoan episode). This succession of extreme climatic crises induced a stress which is considered as a strong selective pressure on the evolution of life (Hoffman et al., 1998). However recent biological records (Corsetti, 2006) do not support this theory as little change is observed in the diversity of microfossils outcrops before and after the Marinoan glacial interval. In this contribution we address this apparent paradox. Using a numerical model of carbon-alkalinity global cycles, we quantify several environmental stresses caused by a global glaciation. We suggest that during global glaciations, the ocean becomes acidic (pH~6), and unsaturated with respect to carbonate minerals. Moreover the quick transition from ice-house to greenhouse conditions implies an abrupt and large shift of the oceanic surface temperature which causes an extended hypoxia. The intense continental weathering, in the aftermath of the glaciation, deeply affects the seawater composition inducing rapid changes in terms of pH and alkalinity. We also propose a new timing for post glacial perturbations and for the cap carbonates deposition, ~2 Myr instead of 200 kyr as suggested in a previous modelling study. In terms of Precambrian life sustainability, seawater pH modifications appear drastic all along the glaciation, but we show that the buffering action of the oceanic crust dissolution processes avoids a total collapse of biological productivity. In opposite short-lived and large post-glacial perturbations are more critical and may have played a role of environmental filter suggested in the classic snowball Earth theory. Only a permissive life (prokaryotes or simple eukaryotes) may explain the relative continuity in microfossils diversity observed before, during and after Neoproterozoic glaciation events.
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17

Chew, David M., Nicola Fallon, Christine Kennelly, Quentin Crowley, and Michael Pointon. "Basic volcanism contemporaneous with the Sturtian glacial episode in NE Scotland." Earth and Environmental Science Transactions of the Royal Society of Edinburgh 100, no. 04 (December 2009): 399–415. http://dx.doi.org/10.1017/s1755691009009037.

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ABSTRACTThe Dalradian Supergroup contains three distinct glacigenic units, formerly termed ‘Boulder Beds’, which are correlated with widespread Neoproterozoic glaciations. The oldest and thickest unit, the Port Askaig Formation, marks the Appin–Argyll group boundary of the Dalradian Supergroup and has been correlated with the Middle Cryogenian (Sturtian) glaciation. The Auchnahyle Formation, a diamictite-bearing sequence near Tomintoul in NE Scotland, exhibits strong lithological similarities to the Port Askaig Formation. Both these glacigenic ‘Boulder Bed’ units contain abundant dolomite clasts in their lower parts and more granitic material at higher levels. Both metadiamictite units are overlain by thick shallow-marine quartzite units. C isotope data from Appin Group carbonate strata below the Auchnahyle Formation support this correlation. U–Pb laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) detrital zircon data from the Auchnahyle Formation metadiamictite differ slightly from the Port Askaig Formation, but are similar to detrital zircon spectra obtained from the Macduff Formation, a diamictite unit in the younger Southern Highland Group of the Dalradian Supergroup; both apparently reflect derivation from local basement rocks. No detritus younger than 0·9 Ga is observed, so the data do not constrain significantly the depositional age of the glacial strata. A thin tholeiitic pillow basalt unit in the lower part of the Auchnahyle Formation is geochemically distinct from pre-tectonic metadolerite sills and from basic metavolcanic rocks up-section. A Sturtian (c. 720–700 Ma) age for the Auchnahyle Formation metadiamictite would imply that this basaltic volcanism represents the oldest recorded volcanic activity in the Dalradian Supergroup and is inferred to represent an early, local phase of proto-Iapetan rifting within the Rodinian supercontinent.
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18

Al-Husseini, Moujahed I. "GeoArabia’s Infracambrian Debate: Cryogenian versus Ediacaran Models." GeoArabia 15, no. 2 (April 1, 2010): 209–44. http://dx.doi.org/10.2113/geoarabia1502209.

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ABSTRACT The Middle Eastern Infracambrian Debate offers specific choices between profoundly different tectono-stratigraphic models that have important scientific and petroleum exploration implications worldwide. A crucial first step in the Debate is choosing between the interpretations of zircon geochronology (Cryogenian Model) or regional chrono-stratigraphy based on much younger age-dating by alternative radiometric techniques (e.g. K-Ar, Rb-Sr, Ar/Ar; Ediacaran Model). The interpretation of zircon geochronology implies Oman’s oldest diamictites of the Abu Mahara Group represent the Sturtian (ca. 720–700 Ma) and Miranoan (ca. 663–636 Ma) glaciations of the Cryogenian Period (850–630 Ma) separated by the ca. 50 My Fiq-Ghubrah Hiatus. The Cryogenian Model implies three phases of rifting in the same regions between ca. 723–530 Ma, and another younger but disputed ca. 30–40 My Shuram-Khufai Hiatus occurring in a tectonically quiescent platform setting (post-glacial Nafun Group’s fine clastics and carbonates). This combined essay and book review of Global Neoproterozoic Petroleum Systems disputes the interpretation of zircon geochronology to establish absolute time for Oman’s oldest rocks. It argues for the single-rift-without-hiatus Ediacaran Model based on ages of basement and volcanic rocks using alternative radiometric techniques in Jordan, Oman and Saudi Arabia. Oman’s Hadash Formation and coeval Mirbat Cap Carbonate are believed to provide an important correlative marker that recorded the start of the great sea-level rise of the Nafun Transgression at ca. 572 Ma, not 636 Ma. The Transgression was due to the melt-out of the late Ediacaran Varanginian Glaciation (represented in Oman by the diamictites of the Ayn, combined Fiq-Ghubrah and subsurface Ghadir Manqil formations, all of the Abu Mahara Group, deposited between ca. 585–572 Ma), not the Sturtian and Miranoan glaciations. The deep-marine organic-rich shales and siliciclastics of Oman’s Masirah Bay Formation (coeval Arkahawl Formation of Mirbat Group) are syn-rift and reflect the Nafun Transgression spilling beyond the rift basins and their surrounding lowlands. As proposed in the Middle East Geologic Time Scale 2010 and GeoArabia’s Infracambrian Debate, the time interval ca. 585–530 Ma can best be cast in terms of transgressive-regressive chrono-sequences in a regional tectono-stratigraphic extensional framework.
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Le Ber, Erwan, Daniel P. Le Heron, Gerd Winterleitner, Dan W. J. Bosence, Bernie A. Vining, and Fred Kamona. "Microbialite recovery in the aftermath of the Sturtian glaciation: Insights from the Rasthof Formation, Namibia." Sedimentary Geology 294 (August 2013): 1–12. http://dx.doi.org/10.1016/j.sedgeo.2013.05.003.

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20

Wang, Dan, Xiang-Kun Zhu, Nina Zhao, Bin Yan, Xian-Hua Li, Fuqiang Shi, and Feifei Zhang. "Timing of the termination of Sturtian glaciation: SIMS U-Pb zircon dating from South China." Journal of Asian Earth Sciences 177 (June 2019): 287–94. http://dx.doi.org/10.1016/j.jseaes.2019.03.015.

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21

Xu, Zhiming, Chengquan Wu, Zhengwei Zhang, Jinhong Xu, Xiyao Li, and Ziru Jin. "Separation of Fe from Mn in the Cryogenian Sedimentary Mn Deposit, South China: Insights from Ore Mineral Chemistry and S Isotopes from the Dawu Deposit." Minerals 11, no. 5 (April 23, 2021): 446. http://dx.doi.org/10.3390/min11050446.

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Manganese and Fe have similar geochemical properties in the supergene environment. Separation of Mn and Fe is an important process for the formation of high-grade sedimentary manganese deposits. Large-scale manganese carbonate deposits (total reserves of approximately 700 Mt) were formed during the interglacial of the Sturtian and Marinoan in South China. The orebodies are hosted in the black rock series at the basal Datangpo Formation of the Cryogenian period. The Fe contents in ores range from 1.15 to 7.18 wt.%, with an average of 2.80 wt.%, and the average Mn/Fe ratio is 8.9, indicating a complete separation of Mn and Fe during the formation of manganese ores. Here, we present element data of manganese carbonates and sulfur isotopes of pyrite from the Dawu deposit, Guizhou, China, aiming to investigate the separation mechanism of Mn and Fe and the ore genesis. The Fe in ores mainly occurs as carbonate (FeCO3) and pyrite (FeS2). The Mn, Ca, Mg and Fe exist in the form of isomorphic substitutions in manganese carbonate. The contents of FeCO3 in manganese carbonates are similar in different deposits, with averages of 2.6–2.8 wt.%. The whole-rock Fe and S contents have an obvious positive correlation (R = 0.69), indicating that the difference of whole-rock Fe content mainly comes from the pyrite content. The δ34SV-CDT of pyrite varies from 40.0 to 48.3‰, indicating that the pyrite formed in a restricted basin where sulfate supply was insufficient and the sulfate concentrations were extremely low. Additionally, the whole-rock Fe content is negatively correlated with the δ34S values of the whole-rock and pyrite, with correlation coefficients of −0.78 and −0.83, respectively. Two stages of separations of Mn and Fe might have occurred during the mineralization processes. The reduced seawater became oxidized gradually after the Sturtian glaciation, and Fe2+ was oxidized and precipitated before Mn2+, which resulted in the first-stage separation of Mn and Fe. The residual Mn-rich and Fe-poor seawater flowed into the restricted rift basin. Mn and Fe were then precipitated in sediments as oxyhydroxide as the seawater was oxidized. At the early stage of diagenesis, organic matter was oxidized, and manganese oxyhydroxide was reduced, forming the manganese carbonate. H2S was insufficient in the restricted basin due to the extremely low sulfate concentration. The Fe2+ was re-released due to the lack of H2S, resulting in the second-stage separation of Mn and Fe. Finally, the manganese carbonate deposit with low Fe and very high δ34S was formed in the restricted basin after the Sturtian glaciation.
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22

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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23

Wei, Guang-Yi, Wei Wei, Dan Wang, Tao Li, Xiaoping Yang, Graham A. Shields, Feifei Zhang, et al. "Enhanced chemical weathering triggered an expansion of euxinic seawater in the aftermath of the Sturtian glaciation." Earth and Planetary Science Letters 539 (June 2020): 116244. http://dx.doi.org/10.1016/j.epsl.2020.116244.

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24

Kendall, Brian, Robert A. Creaser, and David Selby. "Re-Os geochronology of postglacial black shales in Australia: Constraints on the timing of “Sturtian” glaciation." Geology 34, no. 9 (2006): 729. http://dx.doi.org/10.1130/g22775.1.

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25

Liu, Hao, Zhengjiang Wang, Qi Deng, Qiuding Du, and Fei Yang. "Constraints on the onset age of the Sturtian glaciation from the Southeast Yangtze Block, South China." International Geology Review 61, no. 15 (January 19, 2019): 1876–86. http://dx.doi.org/10.1080/00206814.2019.1566787.

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26

Qi, Liang, Mingcai Hou, Peter A. Cawood, Xianguo Lang, Shengxian Zhu, and Mingxuan Zhang. "Neoproterozoic storm deposits in western Yangtze: Implications for the sea conditions during the middle Sturtian glaciation." Precambrian Research 384 (January 2023): 106945. http://dx.doi.org/10.1016/j.precamres.2022.106945.

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27

Wei, Wei, Robert Frei, Robert Klaebe, Da Li, Guang-Yi Wei, and Hong-Fei Ling. "Redox condition in the Nanhua Basin during the waning of the Sturtian glaciation: A chromium-isotope perspective." Precambrian Research 319 (December 2018): 198–210. http://dx.doi.org/10.1016/j.precamres.2018.02.009.

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28

Li, Pengbo, Dongjie Tang, Xiaoying Shi, Ganqing Jiang, Xiangkuan Zhao, Xiqiang Zhou, Xinqiang Wang, and Xi Chen. "Sunspot cycles recorded in siliciclastic biolaminites at the dawn of the Neoproterozoic Sturtian glaciation in South China." Precambrian Research 315 (September 2018): 75–91. http://dx.doi.org/10.1016/j.precamres.2018.07.018.

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29

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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30

Liu, Y., W. R. Peltier, J. Yang, and G. Vettoretti. "The initiation of Neoproterozoic "snowball" climates in CCSM3: the influence of paleo-continental configuration." Climate of the Past Discussions 9, no. 4 (July 2, 2013): 3615–62. http://dx.doi.org/10.5194/cpd-9-3615-2013.

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Abstract. We identify the "hard snowball" bifurcation point at which total sea ice cover of the oceans is expected by employing the comprehensive coupled climate model CCSM3 for two realistic Neoproterozoic continental configurations, namely a low-latitude configuration appropriate for the 720 Ma Sturtian glaciation and a higher southern latitude configuration more appropriate for the later 635 Ma Marinoan glaciation. We find that for the same total solar insolation (TSI) and atmospheric CO2 concentration (pCO2), the most recent continental configuration is characterized by colder climate than the 720 Ma continental configuration and enters the hard snowball state more easily on account of the following four factors: the low heat capacity of land in the south polar region, the higher albedo of the snow covered land compared to that of sea ice, the more negative net cloud forcing near the ice front in the Northern Hemisphere (NH), and more importantly, the more efficient sea ice transport towards the equator in the NH due to the absence of blockage by continents. Beside the paleogeography, we also find the optical depth of aerosol to have a significant influence on this important bifurcation point. When the high value (recommended by CCSM3 but demonstrated to be a significant overestimate) is employed, the critical values of pCO2, beyond which a hard snowball will be realized, are between 80–90 ppmv and 140–150 ppmv for the Sturtian and Marinoan continental configurations, respectively. However, if a lower value is employed that enables the model to approximately reproduce the present-day climate, then the critical values of pCO2 become 50–60 ppmv and 100–110 ppmv for the two continental configurations, respectively. All of these values are higher than previously obtained for the present-day geography (17–35 ppmv) using the same model, primarily due to the absence of vegetation, but are much lower than that obtained previously for the 635 Ma continental configuration using the ECHAM5/MPI-OM model in its standard configuration (∼500 ppmv). However, when the sea ice albedo in that model was reduced from 0.75 to a more appropriate value of 0.45, the critical pCO2 becomes ∼204 ppmv, closer to but still higher than the values obtained here. Our results are similar to those obtained with the present-day geography (70–100 ppmv) when the most recent version of the NCAR model, CCSM4, is employed.
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31

Klaebe, R. M., M. P. Smith, I. J. Fairchild, E. J. Fleming та M. J. Kennedy. "Facies-dependent δ13C variation and diagenetic overprinting at the onset of the Sturtian glaciation in North-East Greenland". Precambrian Research 319 (грудень 2018): 96–113. http://dx.doi.org/10.1016/j.precamres.2017.12.008.

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32

Dub, S. A. "Upper Precambrian General Stratigraphic Scale of Russia: Main problems and proposals for improvement." LITHOSPHERE (Russia) 21, no. 4 (August 28, 2021): 449–68. http://dx.doi.org/10.24930/1681-9004-2021-21-4-449-468.

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Research subject. Main problems of the General Stratigraphic Scale (GSS) of the Upper Precambrian including uncertainties in the hierarchy of subdivisions are analyzed.Results. Prospects for detailing the Upper Precambrian GSS are discussed, along with questions of its correlation with International Chronostratigraphic Chart (ICSC) and establishing the lower boundaries of chronostratigraphic subdivisions. The importance of unifying the existing views is emphasized.Conclusions. It is proposed to carry out the following reforms of GSS: to abolish Acrothemes / Acrons; to approve the Proterozoic (as well as the Archean) as an Eonotheme / Eon; to minimize the use of terms “Upper Proterozoic” and “Lower Proterozoic”; to assign the Riphean and Vendian to the rank of Erathem / Era (while preserving the status of the Vendian as a System / Period); to consider Burzyanian, Yurmatinian, Karatavian and Arshinian as Systems / Periods of the Riphean. Attention is focused on the Upper Riphean-Vendian interval. The lower boundary of the Upper Riphean (Karatavian) was proposed to establish according to the first appearance of the Trachyhystrichosphaera sp. microfossils. Then, the Terminal Riphean (Arshinian) lower boundary should be traced to the base of the tillites formed during the global Sturtian glaciation (which approximately corresponds to the base of the Cryogenian in ICSC). Apparently, the Vendian lower boundary may be raised to the level of the top of the Gaskiers tillites, as the deposits of the last major glaciation in the Precambrian. The indicated proposals are substantiated. It is necessary to form work groups to develop solutions.
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33

MacLennan, Scott, Yuem Park, Nicholas Swanson-Hysell, Adam Maloof, Blair Schoene, Mulubrhan Gebreslassie, Eliel Antilla, Tadele Tesema, Mulugeta Alene, and Bereket Haileab. "The arc of the Snowball: U-Pb dates constrain the Islay anomaly and the initiation of the Sturtian glaciation." Geology 46, no. 6 (April 26, 2018): 539–42. http://dx.doi.org/10.1130/g40171.1.

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34

Song, Gaoyuan, Xinqiang Wang, Xiaoying Shi, and Ganqing Jiang. "New U-Pb age constraints on the upper Banxi Group and synchrony of the Sturtian glaciation in South China." Geoscience Frontiers 8, no. 5 (September 2017): 1161–73. http://dx.doi.org/10.1016/j.gsf.2016.11.012.

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35

Liu, Y., W. R. Peltier, J. Yang, and G. Vettoretti. "The initiation of Neoproterozoic "snowball" climates in CCSM3: the influence of paleocontinental configuration." Climate of the Past 9, no. 6 (November 14, 2013): 2555–77. http://dx.doi.org/10.5194/cp-9-2555-2013.

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Abstract. We identify the "hard snowball" bifurcation point at which total sea-ice cover of the oceans is expected by employing the comprehensive coupled climate model CCSM3 (Community Climate System Model version 3) for two realistic Neoproterozoic continental configurations, namely a low-latitude configuration appropriate for the 720 Ma Sturtian glaciation and a higher southern latitude configuration reconstructed for 570 Ma but which has often been employed in the past to study the later 635 Ma Marinoan glaciation. Contrary to previous suggestions, we find that for the same total solar insolation (TSI) and atmospheric CO2 concentration (pCO2), the 570 Ma continental configuration is characterized by colder climate than the 720 Ma continental configuration and enters the hard snowball state more easily on account of the following three factors: the higher effective albedo of the snow-covered land compared to that of sea ice, the more negative net cloud forcing near the ice front in the Northern Hemisphere (NH), and, more importantly, the more efficient sea-ice transport towards the Equator in the NH due to the absence of blockage by continents. Beside the paleogeography, we also find the optical depth of aerosol to have a significant influence on this important bifurcation point. When the high value (recommended by CCSM3 but demonstrated to be a significant overestimate) is employed, the critical values of pCO2, beyond which a hard snowball will be realized, are between 80 and 90 ppmv (sea-ice fraction 55%) and between 140 and 150 ppmv (sea-ice fraction 50%) for the Sturtian and Marinoan continental configurations, respectively. However, if a lower value is employed that enables the model to approximately reproduce the present-day climate, then the critical values of pCO2 become 50–60 ppmv (sea-ice fraction 57%) and 100–110 ppmv (sea-ice fraction 48%) for the two continental configurations, respectively. All of these values are higher than previously obtained for the present-day geography (17–35 ppmv) using the same model, primarily due to the absence of vegetation, which increases the surface albedo, but are much lower than that obtained previously for the Marinoan continental configuration using the ECHAM5/MPI-OM model in its standard configuration (~500 ppmv). However, when the sea-ice albedo in that model was reduced from 0.75 to a more appropriate value of 0.45, the critical pCO2 becomes ~204 ppmv, closer to the values obtained here. Our results are similar to those obtained with the present-day geography (70–100 ppmv) when the most recent version of the NCAR model, CCSM4, was employed.
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36

Park, John K. "Paleomagnetic evidence for low-latitude glaciation during deposition of the Neoproterozoic Rapitan Group, Mackenzie Mountains, N.W.T., Canada." Canadian Journal of Earth Sciences 34, no. 1 (January 1, 1997): 34–49. http://dx.doi.org/10.1139/e17-003.

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The rift-related Rapitan Group of the Mackenzie Mountains of northwestern Canada acquired several magnetizations due to pulses of hydrothermal activity. The first pulse, attributed to initiation of Rapitan rifting, produced a widespread overprint (P2) that may be reflected in the basal Mount Berg Formation. Two later pulses produced overprints similar to components found in an earlier study. Development of iron formation and hematite pigment in the overlying Sayunei Formation is attributed to the second pulse, represented by a paleopole (N = 10 sites; 334°E, 01°S; δp, δm = 4°, 9°) that coincides with poles of the Franklin igneous events of northern Canada. The Franklin episode, suggested on geological grounds to be coeval with Sayunei deposition, dates the Sayunei at ca. 725 Ma. This relation implies that rifting in Mackenzie Mountains could be related to rifting in northern Canada. A third pulse, reflected by a pole at 007°E, 16°N (N = 6 sites; δp, δm = 6°, 12°), is attributed to final rifting during deposition of the Shezal Formation at the top of the Rapitan. Overprints attributed to Sayunei and Shezal times indicate regional latitudes of 6 ± 4° and 4 ± 6° during the Sturtian glaciation. During Mount Berg time, the regional latitude could have exceeded 25°. All directions have been tilt corrected and some have been then rotated, based on comparisons with a P2 reference overprint.
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37

Li, Fangbing, Xianguo Lang, Haoran Ma, Yixin Cui, Haoxiang Pei, and Bing Shen. "Heterogeneous seawater phosphorus concentrations during the Sturtian glaciation: Evidence from P/Fe ratios of Fulu Formation ironstone in South China." Palaeogeography, Palaeoclimatology, Palaeoecology 537 (January 2020): 109409. http://dx.doi.org/10.1016/j.palaeo.2019.109409.

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38

Środoń, Jan, Axel Gerdes, Jan Kramers, and Maciej J. Bojanowski. "Age constraints of the Sturtian glaciation on western Baltica based on U-Pb and Ar-Ar dating of the Lapichi Svita." Precambrian Research 371 (April 2022): 106595. http://dx.doi.org/10.1016/j.precamres.2022.106595.

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39

Hu, Chunlin, and Maoyan Zhu. "Lithofacies and glacio-tectonic deformation structures of the Tiesi'ao/Dongshanfeng Formation on the Yangtze Block, South China: Implications for Sturtian Glaciation dynamics." Palaeogeography, Palaeoclimatology, Palaeoecology 538 (January 2020): 109481. http://dx.doi.org/10.1016/j.palaeo.2019.109481.

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40

Kumar, Gopendra, and P. K. Maithy. "The Ediacaran Period: It's lower and upper boundaries in India." Journal of Palaeosciences 57, no. (1-3) (December 31, 2008): 33–52. http://dx.doi.org/10.54991/jop.2008.226.

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The newly established Ediacaran Period (terminal Proterozoic) 'begins with termination of the last great global glaciation (Marinoan) of the Neoproterozoic Era' and ends with appearance of biologically distinct world characterised by an assemblage of diverse skeletal fossils of bilaterian animals of the Cambrian Period. Significant depletion in C-isotope values is also recorded at both the boundaries. In India, Ediacaran sequences form part of a continuous sequence that rests unconformably over the oldest platform sequences (Meso-Cryogenian) in many parts of the Lesser and Tethys/Higher Himalaya, and grade into Cambrian. Of the various sections studied, the Maldeota section of the Baliana-Krol-Tal succession, Krol Belt, Lesser Himalaya is found to be the best for the study of both the boundaries. The Lower boundary of the Period is marked at the base of red-green shale and pinkish lenticular dolomite (Member G) - the cap carbonate, forming topmost bed of the Blaini Formation, Baliana Group. There is marked change in assemblage of acritarch and cyanobacteria within upper part of the Baliana Group with appearance and extinction of Ediacaran fauna in the overlying Krol. This change is also accompanied with a significant depletion in C-isotope values in the 'cap carbonate'. The upper boundary could not be precisely demarcated in the absence of boundary diagnostic trace fossils. However, a significant depletion in C-isotope values is recorded in the upper part of the Krol Group with appearance of spiny and processed acritarch (acanthomorphs), scaphomorphs and hercomorphs, small shelly fossils, trace fossils and trilobites of Early Cambrian age in the overlying Tal Group, which is considered to mark the boundary. A review of biota recorded from older sequences viz. Vindhyan Supergroup, Bhima, Kurnool, Chhattisgarh, and Indravati Groups, etc. of the peninsular India, suggest them to be of Mesoproterozoic-Cryogenian (pre-Sturtian glaciation) age. The paper discusses in detail both lower and upper boundaries of the Ediacaran Period and attempts at the correlation with GSSP.
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41

Lan, Zhongwu, Xian-Hua Li, Qirui Zhang, and Qiu-Li Li. "Global synchronous initiation of the 2nd episode of Sturtian glaciation: SIMS zircon U–Pb and O isotope evidence from the Jiangkou Group, South China." Precambrian Research 267 (September 2015): 28–38. http://dx.doi.org/10.1016/j.precamres.2015.06.002.

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42

Eyster, Athena E., Roger R. Fu, Justin V. Strauss, Benjamin P. Weiss, Charlie F. Roots, Galen P. Halverson, David A. D. Evans, and Francis A. Macdonald. "Paleomagnetic evidence for a large rotation of the Yukon block relative to Laurentia: Implications for a low-latitude Sturtian glaciation and the breakup of Rodinia." Geological Society of America Bulletin 129, no. 1-2 (September 15, 2016): 38–58. http://dx.doi.org/10.1130/b31425.1.

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43

Flowers, Rebecca M., Francis A. Macdonald, Christine S. Siddoway, and Rachel Havranek. "Diachronous development of Great Unconformities before Neoproterozoic Snowball Earth." Proceedings of the National Academy of Sciences 117, no. 19 (April 27, 2020): 10172–80. http://dx.doi.org/10.1073/pnas.1913131117.

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The Great Unconformity marks a major gap in the continental geological record, separating Precambrian basement from Phanerozoic sedimentary rocks. However, the timing, magnitude, spatial heterogeneity, and causes of the erosional event(s) and/or depositional hiatus that lead to its development are unknown. We present field relationships from the 1.07-Ga Pikes Peak batholith in Colorado that constrain the position of Cryogenian and Cambrian paleosurfaces below the Great Unconformity. Tavakaiv sandstone injectites with an age of ≥676 ± 26 Ma cut Pikes Peak granite. Injection of quartzose sediment in bulbous bodies indicates near-surface conditions during emplacement. Fractured, weathered wall rock around Tavakaiv bodies and intensely altered basement fragments within unweathered injectites imply still earlier regolith development. These observations provide evidence that the granite was exhumed and resided at the surface prior to sand injection, likely before the 717-Ma Sturtian glaciation for the climate appropriate for regolith formation over an extensive region of the paleolandscape. The 510-Ma Sawatch sandstone directly overlies Tavakaiv-injected Pikes granite and drapes over core stones in Pikes regolith, consistent with limited erosion between 717 and 510 Ma. Zircon (U-Th)/He dates for basement below the Great Unconformity are 975 to 46 Ma and are consistent with exhumation by 717 Ma. Our results provide evidence that most erosion below the Great Unconformity in Colorado occurred before the first Neoproterozoic Snowball Earth and therefore cannot be a product of glacial erosion. We propose that multiple Great Unconformities developed diachronously and represent regional tectonic features rather than a synchronous global phenomenon.
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44

Rud`ko, Sergey, Nikolay Kuznetsov, Andrey Shatsillo, Dmitry Rud`ko, Sergey Malyshev, Alexander Dubenskiy, Viktor Sheshukov, Nadezhda Kanygina, and Tatiana Romanyuk. "Sturtian glaciation in Siberia: Evidence of glacial origin and U-Pb dating of the diamictites of the Chivida Formation in the north of the Yenisei Ridge." Precambrian Research 345 (August 2020): 105778. http://dx.doi.org/10.1016/j.precamres.2020.105778.

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45

Zhang, ShiHong, GanQing Jiang, Jin Dong, YiGui Han, and HuaiChun Wu. "New SHRIMP U-Pb age from the Wuqiangxi Formation of Banxi Group: Implications for rifting and stratigraphic erosion associated with the early Cryogenian (Sturtian) glaciation in South China." Science in China Series D: Earth Sciences 51, no. 11 (October 22, 2008): 1537–44. http://dx.doi.org/10.1007/s11430-008-0119-z.

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46

Hohl, Simon V., Shao-Yong Jiang, Sebastian Viehmann, Wei Wei, Qian Liu, Hai-Zhen Wei, and Stephen J. G. Galer. "Trace Metal and Cd Isotope Systematics of the Basal Datangpo Formation, Yangtze Platform (South China) Indicate Restrained (Bio)Geochemical Metal Cycling in Cryogenian Seawater." Geosciences 10, no. 1 (January 19, 2020): 36. http://dx.doi.org/10.3390/geosciences10010036.

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The behaviour of bioavailable trace metals and their stable isotopes in the modern oceans is controlled by uptake into phototrophic organisms and adsorption on and incorporation into marine authigenic minerals. Among other bioessential metals, Cd and its stable isotopes have recently been used in carbonate lithologies as novel tracer for changes in the paleo primary productivity and (bio)geochemical cycling. However, many marine sediments that were deposited during geologically highly relevant episodes and which, thus, urgently require study for a better understanding of the paleo environment are rather composed of a mixture of organic matter (OM), and detrital and authigenic minerals. In this study, we present Cd concentrations and their isotopic compositions as well as trace metal concentrations from sequential leachates of OM-rich shales of the Cryogenian basal Datangpo Formation, Yangtze Platform (South China). Our study shows variable distribution of conservative and bioavailable trace metals as well as Cd isotope compositions between sequential leachates of carbonate, OM, sulphide, and silicate phases. We show that the Cd isotope compositions obtained from OM leachates can be used to calculate the ambient Cryogenian surface seawater of the restricted Nanhua Basin by applying mass balance calculations. By contrast, early diagenetic Mn carbonates and sulphides incorporated the residual Cd from dissolved organic matter that was in isotopic equilibrium with deep/pore waters of the Nanhua Basin. Our model suggests that the Cd isotopic composition of surface seawater at that time reached values of modern oxygenated surface oceans. However, the deep water Cd isotope composition was substantially heavier than that of modern fully oxygenated oceans and rather resembles deep waters with abundant sulphide precipitation typical for modern oxygen minimum zones. This argues for incomplete recycling of Cd and other bioavailable metals shortly after the Sturtian glaciation in the redox stratified Cryogenian Nanhua Basin. Our study highlights the importance of sequential leaching procedures when dealing with impure authigenic sediments such as OM-rich carbonates, mudstones, or shales to achieve reliable trace metal concentrations and Cd isotope compositions as proxies for (bio)geochemical metal cycling in past aquatic systems.
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47

Müller, W. E. G., and H. C. Schröder. "The unique skeleton of siliceous sponges (Porifera; Hexactinellida and Demospongiae) that evolved first from the Urmetazoa during the Proterozoic: a review." Biogeosciences 4, no. 2 (May 3, 2007): 219–32. http://dx.doi.org/10.5194/bg-4-219-2007.

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Abstract. Sponges (phylum Porifera) had been considered as an enigmatic phylum, prior to the analysis of their genetic repertoire/tool kit. Already with the isolation of the first adhesion molecule, galectin, it became clear that the sequences of sponge cell surface receptors and of molecules forming the intracellular signal transduction pathways triggered by them, share high similarity with those identified in other metazoan phyla. These studies demonstrated that all metazoan phyla, including Porifera, originate from one common ancestor, the Urmetazoa. The sponges evolved prior to the Ediacaran-Cambrian boundary (542 million years ago [myr]) during two major "snowball earth events", the Sturtian glaciation (710 to 680 myr) and the Varanger-Marinoan ice ages (605 to 585 myr). During this period the ocean was richer in silica due to the silicate weathering. The oldest sponge fossils (Hexactinellida) have been described from Australia, China and Mongolia and are thought to have existed coeval with the diverse Ediacara fauna. Only little younger are the fossils discovered in the Sansha section in Hunan (Early Cambrian; China). It has been proposed that only the sponges possessed the genetic repertoire to cope with the adverse conditions, e.g. temperature-protection molecules or proteins protecting them against ultraviolet radiation. The skeletal elements of the Hexactinellida (model organisms Monorhaphis chuni and Monorhaphis intermedia or Hyalonema sieboldi) and Demospongiae (models Suberites domuncula and Geodia cydonium), the spicules, are formed enzymatically by the anabolic enzyme silicatein and the catabolic enzyme silicase. Both, the spicules of Hexactinellida and of Demospongiae, comprise a central axial canal and an axial filament which harbors the silicatein. After intracellular formation of the first lamella around the channel and the subsequent extracellular apposition of further lamellae the spicules are completed in a net formed of collagen fibers. The data summarized here substantiate that with the finding of silicatein a new aera in the field of bio/inorganic chemistry started. For the first time strategies could be formulated and experimentally proven that allow the formation/synthesis of inorganic structures by organic molecules. These findings are not only of importance for the further understanding of basic pathways in the body plan formation of sponges but also of eminent importance for applied/commercial processes in a sustainable use of biomolecules for novel bio/inorganic materials.
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48

Müller, W. E. G., J. Li, H. C. Schröder, L. Qiao, and X. Wang. "The unique skeleton of siliceous sponges (Porifera; Hexactinellida and Demospongiae) that evolved first from the Urmetazoa during the Proterozoic: a review." Biogeosciences Discussions 4, no. 1 (February 6, 2007): 385–416. http://dx.doi.org/10.5194/bgd-4-385-2007.

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Анотація:
Abstract. Sponges (phylum Porifera) had been considered as an enigmatic phylum, prior to the analysis of their genetic repertoire/tool kit. Already with the isolation of the first adhesion molecule, galectin, it became clear that the sequences of the sponge cell surface receptors and those of the molecules forming the intracellular signal transduction pathways, triggered by them, share high similarity to those identified in other metazoan phyla. These studies demonstrated that all metazoan phyla, including the Porifera, originate from one common ancestor, the Urmetazoa. The sponges evolved during a time prior to the Ediacaran-Cambrian boundary (542 million years ago (myr)). They appeared during two major "snowball earth events", the Sturtian glaciation (710 to 680 myr) and the Varanger-Marinoan ice ages (605 to 585 myr). During this period the aqueous milieu was silica rich due to the silicate weathering. The oldest sponge fossils (Hexactinellida) have been described from Australia, China and Mongolia and were assessed to have existed coeval with the diverse Ediacara fauna. Only little younger are the fossils discovered in the Sansha section in Hunan (Early Cambrian; China). It has been proposed that only the sponges had the genetic repertoire to cope with the adverse conditions, e.g. temperature-protection molecules or proteins protecting them against ultraviolet radiation. The skeletal elements of the Hexactinellida (model organisms Monorhaphis chuni and Monorhaphis intermedia or Hyalonema sieboldi) and Demospongiae (models Suberites domuncula and Geodia cydonium), the spicules, are formed enzymatically by the anabolic enzyme silicatein and the catabolic enzyme silicase. Both, the spicules of Hexactinellida and of Demospongiae, comprise a central axial canal and an axial filament which harbors the silicatein. After intracellular formation of the first lamella around the channel and the subsequent extracellular apposition of further lamellae the spicules are completed in a net formed of collagen fibers. The data summarized here substantiate that with the finding of silicatein a new aera in the field of bio/inorganic chemistry started. For the first time strategies could be formulated and experimentally proven that allow the formation/synthesis of inorganic structures by organic molecules. These findings are not only of importance for the further understanding of basic pathways in the body plan formation of sponges but also of eminent importance for applied/commercial processes in a sustainable use of biomolecules for novel bio/inorganic materials.
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49

Milton, Jack E., Kenneth A. Hickey, Sarah A. Gleeson, Hendrik Falck, and Julien Allaz. "In Situ Monazite Dating of Sediment-Hosted Stratiform Copper Mineralization in the Redstone Copper Belt, Northwest Territories, Canada: Cupriferous Fluid Flow Late in the Evolution of a Neoproterozoic Sedimentary Basin." Economic Geology 112, no. 7 (November 1, 2017): 1773–806. http://dx.doi.org/10.5382/econgeo.2017.4529.

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Abstract The 300-km-long Redstone copper belt in the Mackenzie Mountains, Northwest Territories, Canada, is composed of a series of sediment-hosted stratiform copper (SSC) deposits hosted in Neoproterozoic fault-bounded intracontinental rift basins. Mineralization at Coates Lake, the largest of these deposits, is concentrated within microbial laminite layers in the transition zone between underlying continental red beds of the Redstone River Formation and overlying marine carbonates of the Coppercap Formation. Disseminated cupriferous sulfides (chalcopyrite, bornite, and chalcocite) form part of a late diagenetic mineral association with dolomite, K-feldspar, albite, quartz, monazite, apatite, and pyrite that partially replaced detrital and early diagenetic minerals, including calcite cements, sulfate, and earlier generations of pyrite. Bornite (± minor chalcopyrite), calcite, dolomite, quartz, K-feldspar, and albite were also deposited in rare bedding-parallel veins adjacent to the lowermost mineralized microbial laminite layer in the transition zone. The absolute timing of mineralization was constrained by in situ U-Th-Pb chemical dating of monazite from four samples hosting disseminated SSC-type mineralization. The monazite have rounded, Th-U-heavy rare earth element-rich, detrital cores surrounded by Th-U-poor, light rare earth element-S-Sr-rich rims. The rim stage of monazite growth is intergrown with and enveloped by cupriferous sulfide and is paragenetically constrained as being part of the disseminated SSC-type mineralizing event. Eleven detrital cores yielded dates between 1843 and 1025 Ma, older than the depositional age of transition zone strata previously constrained to be between 775 and 732 Ma. Ten monazite rims yielded dates between 661 and 607 Ma. A weighted average date of 635 ± 13 Ma provides a maximum estimate, and is our preferred interpretation, for the absolute age of all copper mineralization at the Coates Lake deposit. Mineralization formed approximately 100 m.y. after deposition of the host rocks, during the thermal sag phase of continental rifting. Stratigraphic reconstructions, coupled with estimates of sediment compaction, indicate that at 635 Ma the transition zone was buried by ~4 km of sediments and overlaid another ~1.7 km of sediments that formed the Redstone River and Thundercloud Formations. Mudstone and carbonate-rich units above the transition zone acted as low permeability caps that led to suprahydrostatic fluid pressures in the underlying sediments. The bedding-parallel veins indicate transient supralithostatic fluid pressures. Free convection of pore fluids began within the transition zone and underlying units once they became hydrologically isolated from overlying strata. Mineralization formed as oxidized saline pore fluids circulated through the red beds (± underlying basaltic flows and basal sedimentary detritus), stripping copper and carrying it up into the transition zone. The salinity of the pore fluids may have, at least in part, originated from cryogenic brines generated by the Sturtian (717–662 Ma) global glaciation event.
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50

Feulner, Georg, and Hendrik Kienert. "Climate simulations of Neoproterozoic snowball Earth events: Similar critical carbon dioxide levels for the Sturtian and Marinoan glaciations." Earth and Planetary Science Letters 404 (October 2014): 200–205. http://dx.doi.org/10.1016/j.epsl.2014.08.001.

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