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Ioah Guyot

Summary

Ioah Guyot is a seamount in the Pacific Ocean, close to the Marshall Islands.[2] Part of the Magellan Seamounts, it is a shield volcano that has erupted alkali basalt and hawaiite 87 million years ago, but may have continued erupting into the Miocene. During the Cretaceous, reefs developed on the guyot.

Ioah Guyot
Ioah is located in Oceania
Ioah
Ioah
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Location in the Pacific Ocean

Geography and geomorphology edit

The guyot belongs to the Magellan Seamounts[3] which stretch from the Mariana Trench to Ita Mai Tai seamount.[4] It is also known as Fedorov and Ioan/[1] IOAN, which stands for "Institute of Oceanology of the Academy of Sciences of the USSR".[5] Ita Mai Tai guyot lies south-southeast of Ioah and Pallada guyot north-northwest,[6] other seamounts in the area east of Ioah are Changpogo, Gramberg, Zatonskii and Arirang.[7] There are about 1000 seamounts in the central western Pacific.[4]

Ioah Guyot is a shield volcano[8][9] with an arcuate shape; the two halves that make it up have dimensions of 110 by 66 kilometres (68 mi × 41 mi) and 83 by 65 kilometres (52 mi × 40 mi).[2] The guyot rises 4.5 kilometres (2.8 mi) from the seafloor to 1,420 metres (4,660 ft)[5]–1,380 metres (4,530 ft) depth, forming a summit plateau with a surface area of 1,380 square kilometres (530 sq mi)[10] that is covered by 25–75-metre (82–246 ft) high hills.[2] The rim of the summit plateau is formed by volcanic rocks on the eastern part of the seamount and by reefal limestones on the western;[11] the reef deposits form a sometimes 5 kilometres (3.1 mi) wide[12] and in total about 200 kilometres (120 mi) long ring around the summit platform of Ioah Guyot[13] and cover an area of about 315 square kilometres (122 sq mi), making it the largest limestone outcrop of the Magellan Seamounts.[14] The lower slopes are gentle but steepen between 1,700–2,000-metre (5,600–6,600 ft) depth. Only the lower slopes are covered with thick sediment layers; the upper slopes have sediment accumulations only in sheltered areas[5] and also feature step-like structures.[2] A number of volcanic cones grew on Ioah and form morphostructures, with a density of about 11.1 vents per 1,000 square kilometres (390 sq mi).[15][16] Some of these vents form alignments and Ioah lies at the intersection of two strike-slip faults.[17][9] The seamount rises from the East Mariana Basin over Jurassic seafloor, between the two Ogasawara Fracture Zones.[18][19][20]

Composition edit

Volcanic rocks found on Ioah Guyot include alkali basalt, tholeiite and hawaiite, plus ankaramite, phonolite and trachybasalt;[21][22][23] as well as zeolites formed by hydrothermal processes.[21] Breccia and sandstones cover the exposed rocks[5] and formed through the breakup of basaltic rocks.[24] Reef limestones and other carbonates were emplaced on the seamount, followed during the Eocene-Pleistocene by pelagic sediments.[25] Clay deposits on the slopes and turbidites have also been reported.[26]

Ferromanganese crusts on the seamount contain apatite, asbolane, buserite, calcite, clay, feldspar, ferrihydrite, feroxyhyte, goethite, hematite, quartz and todorokite[27] and reach thicknesses of 10 centimetres (3.9 in),[5] although they only cover small sectors of Ioah Guyot.[28] Phosphate-containing minerals were deposited over time on Ioah; presently the guyot contains about 150,000,000–200,000,000 tonnes (150,000,000–200,000,000 long tons; 170,000,000–220,000,000 short tons) of phosphorite ore.[29] Some of these ferromanganese deposits form nodules encased within limestones.[30] Spherules of cosmic origin have been found.[31]

History edit

The seamount developed about 87 million years ago on the Pacific Plate and is now extinct;[1] its estimated age is placed in a range between 88.5 and 86.2 million years. It was located in the Southern Hemisphere as it formed.[19][8] Some secondary volcanic cones may be much younger, of Miocene age.[32] The formation of Ioah and the other Magellan Seamounts has been explained by a hotspot that would now be located close to the Rarotonga hotspot, Samoa hotspot and Society hotspot were it still active.[22][33][34] Compositionally, volcanic rocks from Ioah resemble these of the Rarotonga hotspot.[35]

During the Aptian-Cenomanian, limestones and volcanic rocks formed sediments on Ioah Guyot which developed a reef system.[36] A secondary reefal phase occurred during Santonian to Maastrichtian times[21] and a third one during the Eocene.[37] Ioah developed the largest reefs of the Magellan Seamounts,[3] with coral material accumulating to thicknesses of 200–300 metres (660–980 ft).[23] During the Eocene, tuffs were emplaced on the seamount.[38] Ferromanganese crusts developed later during the Paleogene[39] and Miocene-Pleistocene,[40] and up to 150 metres (490 ft) sediments accumulated on the summit plateau.[11]

Biology edit

Species that lived on Ioah Guyot during the Cretaceous include ammonoids, belemnites,[41] bivalves, bryozoans, cephalopods, corals, crinoids, foraminifera, gastropods, rudists, sea pens,[23] [42][43] sea urchins[5] and sponges.[23] Presently, a rich fauna has been identified on Ioah Guyot, including scleractinian corals without zooxanthelles such as Fungiacyathus pliciseptus and Peponocyathus australiensis which is usually found in much shallower waters.[18][25][44]

See also edit

References edit

  1. ^ a b c "Ioah Seamount". Seamount Catalog. Retrieved 13 September 2018.
  2. ^ a b c d Mel'nikov, Pletnev & Basov 2006, p. 4.
  3. ^ a b Mel'nikov, Tugolesov & Pletnev 2010, p. 589.
  4. ^ a b Mel'nikov, Pletnev & Basov 2006, p. 3.
  5. ^ a b c d e f Bogdanov et al. 1987, p. 971.
  6. ^ Asavin, A. M.; Kubrakova, I. V.; Mel’nikov, M. E.; Tyutyunnik, O. A.; Chesalova, E. I. (May 2010). "Geochemical zoning in ferromanganese crusts of Ita-MaiTai guyot". Geochemistry International. 48 (5): 425. doi:10.1134/s0016702910050010. ISSN 0016-7029. S2CID 129118428.
  7. ^ Mel'nikov et al. 2016, p. 4.
  8. ^ a b Glasby et al. 2007, p. 317.
  9. ^ a b Utkin, V. P. (June 2006). "Role of strike-slip faulting of the oceanic lithosphere in the formation of pacific volcanic belts". Doklady Earth Sciences. 409 (1): 693. Bibcode:2006DokES.409..692U. doi:10.1134/S1028334X06050023. S2CID 128625849.
  10. ^ Okamoto, Nobuyuki; Usui, Akira (4 March 2014). "Regional Distribution of Co-Rich Ferromanganese Crusts and Evolution of the Seamounts in the Northwestern Pacific". Marine Georesources & Geotechnology. 32 (3): 194. doi:10.1080/1064119x.2013.877110. ISSN 1064-119X. S2CID 128677808.
  11. ^ a b Mel'nikov, Pletnev & Basov 2006, p. 5.
  12. ^ Pletnev 2021, p. 75.
  13. ^ Pletnev 2019, p. 438.
  14. ^ Pletnev 2021, p. 72.
  15. ^ Mel'nikov, Tugolesov & Pletnev 2010, p. 586.
  16. ^ Mel'nikov et al. 2016, p. 437.
  17. ^ Mel'nikov et al. 2016, p. 441.
  18. ^ a b Keller & Shcherba 2006, p. 240.
  19. ^ a b Glasby et al. 2007, p. 316.
  20. ^ Koppers et al. 1998, p. 56.
  21. ^ a b c Zakharov et al. 2012, p. 147.
  22. ^ a b Koppers et al. 1998, p. 55.
  23. ^ a b c d Mel'nikov, Pletnev & Basov 2006, p. 6.
  24. ^ Bogdanov et al. 1987, p. 977.
  25. ^ a b Keller & Shcherba 2006, p. 238.
  26. ^ Pletnev 2019, p. 443.
  27. ^ Glasby et al. 2007, p. 320.
  28. ^ Bogdanov et al. 1987, p. 976.
  29. ^ Glasby et al. 2007, p. 319.
  30. ^ Mel'nikov et al. 2016, p. 5.
  31. ^ Savelyev, D. P.; Khanchuk, A. I.; Savelyeva, O. L.; Moskaleva, S. V.; Mikhailik, P. E. (1 April 2020). "First Find of Platinum in Cosmogenic Spherules of Ferromanganese Crusts (Fedorov Guyot, Magellan Seamounts, Pacific Ocean)". Doklady Earth Sciences. 491 (2): 199. Bibcode:2020DokES.491..199S. doi:10.1134/S1028334X20040157. ISSN 1531-8354. S2CID 219638248.
  32. ^ Mel'nikov et al. 2016, p. 439.
  33. ^ Koppers et al. 2003, p. 19.
  34. ^ Koppers et al. 1998, p. 66.
  35. ^ Koppers et al. 2003, p. 25.
  36. ^ Zakharov et al. 2012, p. 146.
  37. ^ Pletnev 2021, p. 81.
  38. ^ Pletnev 2021, p. 80.
  39. ^ Bogdanov et al. 1987, p. 982.
  40. ^ Bogdanov et al. 1987, p. 981.
  41. ^ Zakharov et al. 2012, p. 145.
  42. ^ Zakharov et al. 2012, pp. 146–147.
  43. ^ Reich, Mike; Kutscher, Manfred (2015). "Sea pens (Octocorallia: Pennatulacea) from the Late Cretaceous of northern Germany". Journal of Paleontology. 85 (6): 1043. doi:10.1666/10-109.1. ISSN 0022-3360. S2CID 130123892.
  44. ^ Keller & Shcherba 2006, p. 239.

Sources edit

  • Bogdanov, Yu. A.; Zonenshayn, L. P.; Lisitsyn, A. P.; Podrazhanskiy, A. M.; Sagalevich, A. M.; Sorokhtin, O. G. (August 1987). "Ferromanganese Ores on Seamounts". International Geology Review. 29 (8): 968–984. Bibcode:1987IGRv...29..968B. doi:10.1080/00206818709466192. ISSN 0020-6814.
  • Glasby, Geoffrey P.; Ren, Xiangwen; Shi, Xuefa; Pulyaeva, Irina A. (2 February 2007). "Co–rich Mn crusts from the Magellan Seamount cluster: the long journey through time". Geo-Marine Letters. 27 (5): 315–323. Bibcode:2007GML....27..315G. doi:10.1007/s00367-007-0055-5. S2CID 128543708.
  • Keller, N. B.; Shcherba, I. G. (March 2006). "Features of the distribution of azooxanthellata scleractinia (Anthozoa) on mid-pacific guyots". Oceanology. 46 (2): 238–241. Bibcode:2006Ocgy...46..238K. doi:10.1134/s000143700602010x. ISSN 0001-4370. S2CID 128414450.
  • Koppers, Anthony A.P.; Staudigel, Hubert; Wijbrans, Jan R.; Pringle, Malcolm S. (November 1998). "The Magellan seamount trail: implications for Cretaceous hotspot volcanism and absolute Pacific plate motion". Earth and Planetary Science Letters. 163 (1–4): 53–68. Bibcode:1998E&PSL.163...53K. doi:10.1016/S0012-821X(98)00175-7. ISSN 0012-821X.
  • Koppers, Anthony A. P.; Staudigel, Hubert; Pringle, Malcolm S.; Wijbrans, Jan R. (October 2003). "Short-lived and discontinuous intraplate volcanism in the South Pacific: Hot spots or extensional volcanism?". Geochemistry, Geophysics, Geosystems. 4 (10): 1089. Bibcode:2003GGG.....4.1089K. doi:10.1029/2003GC000533. S2CID 131213793.
  • Mel'nikov, M. E.; Avdonin, V. V.; Pletnev, S. P.; Sedysheva, T. E. (January 2016). "Buried ferromanganese nodules of the Magellan Seamounts". Lithology and Mineral Resources. 51 (1): 1–12. doi:10.1134/s0024490215060073. ISSN 0024-4902. S2CID 129963490.
  • Mel'nikov, M. E.; Pletnev, S. P.; Basov, I. A. (2006). "New Geological and Paleontological Data on Fedorov Guyot, Magellan Seamounts, Pacific". Tikhookean. Geol. (in Russian). 25 (1): 3–13.
  • Mel'nikov, M. E.; Pletnev, S. P.; Anokhin, V. M.; Sedysheva, T. E.; Ivanov, V. V. (November 2016). "Volcanic edifices on guyots of the Magellan Seamounts (Pacific Ocean)". Russian Journal of Pacific Geology. 10 (6): 435–442. doi:10.1134/s1819714016060038. ISSN 1819-7140. S2CID 132364693.
  • Mel'nikov, M. E.; Tugolesov, D. D.; Pletnev, S. P. (August 2010). "The structure of the incoherent sediments in the Ita Mai Tai Guyot (Pacific Ocean) based on geoacoustic profiling data". Oceanology. 50 (4): 582–590. Bibcode:2010Ocgy...50..582M. doi:10.1134/s0001437010040144. ISSN 0001-4370. S2CID 128475565.
  • Pletnev, S. P. (1 September 2019). "Main Types of Aptian–Cenomanian Sedimentary Rocks on Guyots of the Magellan Mountains, Pacific Ocean". Russian Journal of Pacific Geology. 13 (5): 436–445. doi:10.1134/S1819714019050087. ISSN 1819-7159. S2CID 203654288.
  • Pletnev, S. P. (1 January 2021). "The Main Types of Paleogene Sedimentary Rocks and Conditions of their Formation on the Guyots of the Magellan Seamounts (Pacific Ocean)". Russian Journal of Pacific Geology. 15 (1): 72–83. doi:10.1134/S1819714021010061. ISSN 1819-7159. S2CID 232042072.
  • Zakharov, Yuri D.; Melnikov, Mikhael E.; Popov, Alexander M.; Pletnev, Sergej P.; Khudik, Vladimir D.; Punina, Tatiana A. (January 2012). "Cephalopod and brachiopod fossils from the Pacific: Evidence from the Upper Cretaceous of the Magellan Seamounts". Geobios. 45 (1): 145–156. doi:10.1016/j.geobios.2011.11.011. ISSN 0016-6995.

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