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User:Gwood3710/Islay C-isotope anomaly

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The Islay C-Isotope anomaly or Islay excursion is the name of a subglacial Neoproterozoic carbon Isotope excursion (CIE) after the Islay Limestones in SW Scotland that were first documented by Brasier and Shields in 2000.[1] The Islay excursion occurs in the late Tonian to early Cryogenian period, but is under debate among scientists as to the exact time range, and how best to define it as a precursor to the sturtian glaciations.[2] The anomaly itself represents a δ13Ccarb excursion that precedes glaciation events in each excursion else where.[3]

Location

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This anomaly can be seen globally as confirmed by correlating studies done on glacial deposits found in Namibia,[4] NE Svalbard and East Greenland, Scottish and Irish Caledonides, NW Canada, NW Tasmania, SW United States,[5] Northern Ethiopia, Southern China, and Australia.[6]

Age

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Currently, the age is under debate among scientists based on various isotope age dating techniques such as 87Sr/86Sr,[7] U-Pb,[8] (δ44/40Ca, δ26Mg),[9] Re-Os and initial Os[10] that all correlate to the Islay anomaly. However, Rooney et al. seems to have the developed the best methods using Re-Os dating, and the most recent published results from Millikin et al, using Re-Os suggest an age of 737.5 +/- 9.6 Ma.[2]

The Islay Anomaly is still relatively understudied and under debate among scientists with different perspectives on how it relates to Pre-Sturtian glaciations. It is rare to find stratigraphic sections that record paleoenvironment conditions leading up to a glaciation, but, deposits associated with them can be found globally in glacigenic formations in the form of cap dolostones,[11] and in erosional contacts with overlying diamictites[12]. Among the various studied locations, the unit thicknesses vary from 100m-7000m. The thinnest being in the Coppercap formation in Canada,[13] and the thickest being in the Mackenzie Mountains of Canada,[14] both are part of the Windermere super group. The δ13Ccarb anomaly ranges from -10‰[11] to ~5‰[12] representing a significant magnitude of change in Carbon during this period and is consistent across all studies where they can directly correlate their results with these values.[15]

Controversies

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Proposed Mechanisms

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Against other anomalies

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References

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  1. ^ Hoffman, Paul F.; Halverson, Galen P.; Domack, Eugene W.; Maloof, Adam C.; Swanson-Hysell, Nicholas L.; Cox, Grant M. (2012-06-01). "Cryogenian glaciations on the southern tropical paleomargin of Laurentia (NE Svalbard and East Greenland), and a primary origin for the upper Russøya (Islay) carbon isotope excursion". Precambrian Research. 206–207: 137–158. doi:10.1016/j.precamres.2012.02.018. ISSN 0301-9268.
  2. ^ a b Rooney, Alan D.; Macdonald, Francis A.; Strauss, Justin V.; Dudás, Francis Ö.; Hallmann, Christian; Selby, David (2014-01-07). "Re-Os geochronology and coupled Os-Sr isotope constraints on the Sturtian snowball Earth". Proceedings of the National Academy of Sciences. 111 (1): 51–56. doi:10.1073/pnas.1317266110. ISSN 0027-8424. PMC 3890860. PMID 24344274.{{cite journal}}: CS1 maint: PMC format (link)
  3. ^ Hoffman, Paul F.; Halverson, Galen P.; Domack, Eugene W.; Maloof, Adam C.; Swanson-Hysell, Nicholas L.; Cox, Grant M. (2012-06-01). "Cryogenian glaciations on the southern tropical paleomargin of Laurentia (NE Svalbard and East Greenland), and a primary origin for the upper Russøya (Islay) carbon isotope excursion". Precambrian Research. 206–207: 137–158. doi:10.1016/j.precamres.2012.02.018. ISSN 0301-9268.
  4. ^ Hoffman, Paul F.; Kaufman, Alan J.; Halverson, Galen P.; Schrag, Daniel P. (1998-08-28). "A Neoproterozoic Snowball Earth". Science. 281 (5381): 1342–1346. doi:10.1126/science.281.5381.1342. ISSN 0036-8075.
  5. ^ Hoffman, Paul F.; Halverson, Galen P.; Domack, Eugene W.; Maloof, Adam C.; Swanson-Hysell, Nicholas L.; Cox, Grant M. (2012-06-01). "Cryogenian glaciations on the southern tropical paleomargin of Laurentia (NE Svalbard and East Greenland), and a primary origin for the upper Russøya (Islay) carbon isotope excursion". Precambrian Research. 206–207: 137–158. doi:10.1016/j.precamres.2012.02.018. ISSN 0301-9268.
  6. ^ Millikin, Alexie E.G.; Strauss, Justin V.; Halverson, Galen P.; Bergmann, Kristin D.; Tosca, Nicholas J.; Rooney, Alan D. (2022-04-01). "Calibrating the Russøya excursion in Svalbard, Norway, and implications for Neoproterozoic chronology". Geology. 50 (4): 506–510. doi:10.1130/G49593.1. ISSN 0091-7613.
  7. ^ Cite error: The named reference :22 was invoked but never defined (see the help page).
  8. ^ MacLennan, Scott; Park, Yuem; Swanson-Hysell, Nicholas; Maloof, Adam; Schoene, Blair; Gebreslassie, Mulubrhan; Antilla, Eliel; Tesema, Tadele; Alene, Mulugeta; Haileab, Bereket (2018-06-01). "The arc of the Snowball: U-Pb dates constrain the Islay anomaly and the initiation of the Sturtian glaciation". Geology. 46 (6): 539–542. doi:10.1130/G40171.1. ISSN 0091-7613.
  9. ^ Crockford, Peter W.; Kunzmann, Marcus; Blättler, Clara L.; Kalderon-Asael, Boriana; Murphy, Jack G.; Ahm, Anne-Sofie; Sharoni, Shlomit; Halverson, Galen P.; Planavsky, Noah J.; Halevy, Itay; Higgins, John A. (2021-04-01). "Reconstructing Neoproterozoic seawater chemistry from early diagenetic dolomite". Geology. 49 (4): 442–446. doi:10.1130/G48213.1. ISSN 0091-7613.
  10. ^ Cite error: The named reference :32 was invoked but never defined (see the help page).
  11. ^ a b Cite error: The named reference :02 was invoked but never defined (see the help page).
  12. ^ a b Cite error: The named reference :42 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference :52 was invoked but never defined (see the help page).
  14. ^ Cite error: The named reference :12 was invoked but never defined (see the help page).
  15. ^ Halverson, G.; Porter, S.; Shields, G. (2020), "The Tonian and Cryogenian Periods", Geologic Time Scale 2020, Elsevier, pp. 495–519, doi:10.1016/b978-0-12-824360-2.00017-6, ISBN 978-0-12-824360-2, retrieved 2024-02-27
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