Baratal limestone
| Baratal limestone | |
|---|---|
Geologic formation | |
| Thickness | 8km |
| Lithology | |
| Primary | Limestone |
| Location | |
| Coordinates | 50°15′N 87°53′E / 50.250°N 87.883°E[1] |
| Region | Siberia |
| Country |  Russia |
  Baratal limestone (Russia) | |
Baratal limestone, also known as the Baratal Formation, is a
formation in the Altai Republic of Russia that formed during the Cambrian and Ediacaran, presumably on top of an ancient seamount that was later accreted to a continent. It may constitute the oldest known atoll
in the world.
Geography and geology
The formation crops out west and northwest of Chagan-Uzun in the Altai Republic, Russia, in particular around Kurai and Akkaya[2] in the Kosh-Agach region.[3] It is also known as the Baratal Formation.[4]
The Baratal limestone of
glacial deposits.[10]
Interpretation
The limestone probably formed on a volcanic
mass movement took place around the carbonate platforms, traces of this instability are found in the Baratal limestone[12] which contains parts from both the original carbonate platform and debris from landslides off of it.[13] The seamount was located in an ocean between the Siberian and Kazakhstan continents[14] and is known as the Baratal or Kurai palaeoseamount.[15]
The limestone is largely lacking in
stromatoliths have been recovered.[7] They appear in the form of 40 centimetres (16 in) high and 40 centimetres (16 in)[2] wide domes in numerous layers of the limestone,[9] and probably grew in waters less than 50 metres (160 ft) deep.[16] Unidentified fossils are found within the limestone[2] and ooid units. Because of their relatively simple shapes they cannot be confidently identified,[17] but they appear to be of Cambrian age[18] and may be correlative with the Cambrian small shelly fauna and would indicate that it diversified not only in continental shelf areas but also in the open ocean.[19] The stromatolites were probably constructed by microbial reefs that trapped sediments.[12] Proper Cambrian fossils do not occur in the Baratal limestone.[6]
Age
isotope ratios indicate that the basal limestone was emplaced[21] immediately after the end of Snowball Earth, consistent with the lead-lead isotope dates.[12]
The platform on which the Baratal limestone had formed would have eventually ended up in the Siberian
plate tectonics and was amalgamated[12] onto the Kuznetsk-Altai[14] or Uimen-Lebed' island arc.[1] Faulting also took place,[3] and some faults in the region are active to this day.[10] Groundwater flow through the limestone is leaching elements that later precipitate as tufas in the region.[22]
Geological context
The Baratal limestone is found within the 1,500 kilometres (930 mi) wide and 5,000 kilometres (3,100 mi) long Altai-Sayan
accretionary complex called the Kurai accretionary complex.[6]
The
accretionary complexes in continents. Such outcrops, which allow the investigation of older seafloor, have been encountered in Japan (Paleozoic to Mesozoic) and Siberia (Cambrian).[5]
References
- ^ a b Buslov et al. 2001, p. 217.
- ^ a b c d e Uchio et al. 2004, p. 424.
- ^ a b Uchio et al. 2008, p. 184.
- ^ Safonova 2009, p. 140.
- ^ a b Uchio et al. 2004, p. 422.
- ^ a b c d Nohda et al. 2013, p. 67.
- ^ a b c d e f Uchio et al. 2004, p. 423.
- ^ a b Uchio et al. 2008, p. 186.
- ^ a b Nohda et al. 2013, p. 69.
- ^ a b Kokh et al. 2017, p. 2.
- ^ a b Uchio et al. 2004, p. 425.
- ^ a b c d Uchio et al. 2004, p. 426.
- ^ Uchio et al. 2004, p. 427.
- ^ a b Nohda et al. 2013, p. 72.
- ^ Safonova 2008, p. 494.
- ^ a b Nohda et al. 2013, p. 70.
- ^ Uchio et al. 2008, p. 188.
- ^ Uchio et al. 2008, p. 191.
- ^ Uchio et al. 2008, p. 190.
- ^ Uchio et al. 2008, p. 185.
- ^ Nohda et al. 2013, p. 74.
- ^ Kokh et al. 2017, p. 16.
- ^ Uchio et al. 2008, p. 183.
Sources
- Buslov, M. M.; Saphonova, I. Yu.; Watanabe, T.; Obut, O. T.; Fujiwara, Y.; Iwata, K.; Semakov, N. N.; Sugai, Y.; Smirnova, L. V.; Kazansky, A. Yu. (September 2001). "Evolution of the Paleo-Asian Ocean (Altai-Sayan Region, Central Asia) and collision of possible Gondwana-derived terranes with the southern marginal part of the Siberian continent". Geosciences Journal. 5 (3): 203–224. S2CID 128751598.
- Kokh, Svetlana N.; Sokol, Ella V.; Deev, Evgeny V.; Ryapolova, Yuliya M.; Rusanov, Gennady G.; Tomilenko, Anatoliy A.; Bul'bak, Taras A. (15 June 2017). "Post-Late Glacial calcareous tufas from the Kurai fault zone (Southeastern Gorny Altai, Russia)". Sedimentary Geology. 355: 1–19. ISSN 0037-0738.
- Nohda, Susumu; Wang, Bo-Shian; You, Chen-Feng; Isozaki, Yukio; Uchio, Yuko; Buslov, Michael M.; Maruyama, Shigenori (15 November 2013). "The oldest (Early Ediacaran) Sr isotope record of mid-ocean surface seawater: Chemostratigraphic correlation of a paleo-atoll limestone in southern Siberia". Journal of Asian Earth Sciences. 77: 66–76. ISSN 1367-9120.
- Safonova, I. Yu. (September 2008). "Geochemical evolution of intraplate magmatism in the Paleo-Asian Ocean from the Late Neoproterozoic to the Early Cambrian". Petrology. 16 (5): 492–511. S2CID 54668897.
- Safonova, I. Yu. (1 April 2009). "Intraplate magmatism and oceanic plate stratigraphy of the Paleo-Asian and Paleo-Pacific Oceans from 600 to 140 Ma". Ore Geology Reviews. 35 (2): 137–154. ISSN 0169-1368.
- Uchio, Yuko; Isozaki, Yukio; Ota, Tsutomu; Utsunomiya, Atsushi; Buslov, Mikhail M.; Maruyama, Shigenori (2004). "The oldest mid-oceanic carbonate buildup complex: Setting and lithofacies of the Vendian (Late Neoproterozoic) Baratal limestone in the Gorny Altai Mountains, Siberia". Proceedings of the Japan Academy, Series B. 80 (9): 422–428. S2CID 55987965.
- Uchio, Yuko; Isozaki, Yukio; Buslov, Michael M.; Maruyama, Shigenori (1 August 2008). "Occurrence of phosphatic microfossils in an Ediacaran–Cambrian mid-oceanic paleo-atoll limestone of southern Siberia". Gondwana Research. 14 (1): 183–192. ISSN 1342-937X.