Open AccessA new Silurian palaeolatitude for eastern Avalonia and evidence for crustal rotations in the Avalonian margin of southwestern Ireland
Author(s) -
Mac Niocaill Conall
Publication year - 2000
Publication title -
geophysical journal international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0956-540X
DOI - 10.1046/j.1365-246x.2000.00101.x
Subject(s) - paleozoic , paleomagnetism , carboniferous , geology , paleontology , remanence , component (thermodynamics) , margin (machine learning) , conglomerate , magnetic field , magnetization , structural basin , physics , quantum mechanics , machine learning , computer science , thermodynamics
Palaeomagnetic data are presented from Mid‐Silurian (Homerian, Upper Wenlock, ~425 Ma) sediments from the Dingle Peninsula, SW Ireland, which forms part of the northern margin of the Palaeozoic microcontinent of Avalonia. Three remanence components were recognized. After removal of a low‐temperature component (‘L’), oriented parallel to the present Earth field at the sampling area, two higher‐stability components were isolated: an intermediate‐unblocking‐temperature component (‘I’) with mean in situ D = 196.9°, I = 11.0°, α 95 = 10.8, with a corresponding palaeopole at 330.0°E, 30.6°S ( dp = 5.6, dm = 11.0), and a high‐unblocking‐temperature component (‘H’) with mean tilt‐corrected D = 218.6°, I = 22.1°, α 95 = 7.9, with a corresponding palaeopole at 309.5°E, 18.3°S ( dp = 4.4, dm = 8.4). A primary (Wenlock) age is indicated for the ‘H’‐component by a positive intraformational conglomerate test, whereas the ‘I’‐component is thought to be a secondary mid‐Carboniferous partial remagnetization. These data confirm that the sector of the Iapetus Ocean between Avalonia and Laurentia was essentially closed, within the limits of palaeomagnetic resolution, by the Wenlock. There is still, however, a discrepancy between the declinations recorded by similar‐aged sequences to the north and south of the Iapetus Suture. These point to either an approximately 30° clockwise rotation of the entire Avalonian microcontinent relative to Laurentia during closure, or local vertical axis rotations of the sampling sites in southern Britain.