Iapetus Suture
 | This articleneeds additional citations forverification.(April 2010) |
TheIapetus Sutureis one of several majorgeological faultscaused by the collision of several ancient land masses forming asuture.It represents in part the remains of what was once theIapetus Ocean.Iapetuswas the father ofAtlasin Greek mythology, making his an appropriate name for what used to be called the 'Proto-Atlantic Ocean'. When theAtlantic Oceanopened, in theCretaceousperiod, it took a slightly different line from that of the Iapetus suture, with some originallyLaurentianrocks being left behind in north-westEuropeand other,Avalonian,rocks remaining as part ofNewfoundland.
Background
[edit]TheIapetus Oceanwas an ancient ocean which existed in theSouthern Hemisphereapproximately 600 million years ago and was bordered by several paleocontinents:Laurentia,Ganderia,Carolinia,Avalonia,andBaltica.During a series of geological events, theSalinic orogenyandCaledonian progeny,all three land masses began to converge upon each other, slowly diminishing the ocean by subducting the oceanic crust. By the end of theSilurian period,approximately 420 million years ago, the ocean had disappeared. The geological fault zone resulting from the continental collision is known as the Iapetus Suture, named after the ocean it replaced.
The closure of Iapetus involved a complex and protracted collisional history of numerouscontinental fragments,volcanic arcsandback-arc basinsthat were accreted toLaurentiaand Avalonia between the EarlyOrdovicianand LateSilurian.The notion of a single suture zone in a complex orogen such as the Appalachian/Caledonian is unrealistic as several temporal and spatial distinct suture zones are present.
In Canada
[edit]The Early Ordovician (Taconic)Baie VerteLine inQuebecandNewfoundlandmarks the boundary between the continental margin of Laurentia and Iapetan oceanic rocks, while the Early Ordovician (Penobscot) GRUB Line defines the contact between the vestiges of Iapetus andGanderia.The Middle OrdovicianRed IndianLine is considered the main Iapetan suture zone in that it separates peri-Laurentian and peri-Gondwanan oceanic elements. The Dog Bay Line is a younger feature in the Appalachians and delineates the terminal Iapetan suture in Newfoundland as it marks theEarly Silurian(Salinic) collisional zone between Ganderia and Laurentia.[1]
In the United States
[edit]The suture runs through the north-eastern states of Maine, New Hampshire, Massachusetts and Connecticut. Rhode Island lies entirely to the east of the suture.[2]
In Ireland
[edit]
The estuary of theRiver Shannon(Ireland's largest river) follows the line of the Iapetus suture on the west coast. The suture reaches the east coast atClogherheadinCounty Louth.Ireland's crust (and sedimentary rocks) to the north-west of the suture originally derives from Laurentia (proto-North America), while the crust to the south-east is Avalonian ( "European" ).[4]
On the Isle of Man (Niarbyl Fault)
[edit]
TheNiarbyl Faultis an exposed section of the Iapetus Suture as it crosses through theIrish Sea.It is readily visible in present-dayNiarbylon the southwest coast ofIsle of Man.The fault is manifested by two majorrock groupswhich abut each other, both deposited by their respective, aforementioned continents – theManx Groupto the south-east and theDalby Groupto the north-west.[5]The Niarbyl fault is evidence of two paleocontinents colliding:Avaloniaon which present-dayEnglandis located and Laurentia which contains both present-dayNorth AmericaandScotland.
The fault is visible close to the shoreline downhill from the Niarbyl Cafe and Visitor Centre in Niarbyl.
In Great Britain
[edit]The Caledonian orogeny united the northern and southern portions of present-dayGreat Britain.The Iapetus Suture runs from theSolway FirthtoLindisfarne.[6]TheAnglo-Scottish borderruns near and roughly parallel to the suture.
See also
[edit]- Plate tectonics– Movement of Earth's lithosphere
- Supercontinent cycle– Repeated joining and separation of Earth's continents
- Trans-European Suture Zone– Boundary between the East European Craton and the orogens of South-Western Europe
References
[edit]- ^J. C. Pollock, D. H. C. Wilton, C. R. van Staal, and K. D. Morrissey U-Pb detrital zircon geochronological constraints on the Early Silurian collision of Ganderia and Laurentia along the Dog Bay Line: The terminal Iapetan suture in the Newfoundland Appalachians. Am J Sci, 1 February 2007; 307(2): 399–433
- ^"Map".researchgate.net.Retrieved27 November2020.
- ^Devoy, R., Cummins, V., Brunt, B., Bartlett, D., & Kandrot, S. (2021).The Coastal Atlas of Ireland(Illustrated edition). Cork University Press, page 106.
- ^Baxter, Sadhbh."A Geological Field Guide to Cooley, Gullion, Mourne & Slieve Croob"(PDF).Archived fromthe original(PDF)on 14 November 2017.Retrieved8 November2011.
- ^Burnett, Dave; Guard, Charles; Quirk, Dave (2003)."Dalby Group".Manx Geological Survey.Retrieved15 August2009.
- ^Hill, John (7 February 2007)."Palaeozoic History of the UK – Part 1: Cambrian to Silurian".GeologyRocks.Archived fromthe originalon 23 March 2010.Retrieved16 August2009.