Discordant Silurian paleolatitudes for central Newfoundland: New paleomagnetic evidence from the Springdale Group

Abstract

Ancient remanences are retained by the Early Silurian (429 + 6/-5 Ma) mafic volcamcs of the Sprmgdale Caldera (five sites) and the overlying red beds (seven sites) Dual polarity magnetizations are obtained by thermal demagnehzation of samples from the red beds, whereas single polarity d~rectlons are observed m the volcamcs High unblockmg temperatures indicate hematite as the remanence carrier m both the volcamcs and sedxments These h~gh-temperature, characteristic remanences are easily ~solated and pass both the tilt and conglomerate tests, they are likely to be of primary Silurian age Characteristic dechnatlons are predominantly northerly and northeasterly, and md~cate s~gmficant structural rotahons on a local scale When the results of the red beds and the voleamcs are combined they show characteristic mchnatlons that are shallower than those of the correlative Botwood Group (ca 36 ° vs 43 °) but not nearly as shallow as those reported from the King George IV Lake area (0 5 °) Mean mchnatlons obtained from the Sprmgdale red beds are, however, slgmficantly shallower than those of the Sprmgdale volcanlcs The same difference can be seen m other previous Silurmn paleomagnehc studies of central Newfoundland We infer that an mcllnat~on error affects the red bed magnetizations of the Sprmgdale Group, Botwood Group (Wigwam Formation) and rocks of the King George IV Lake area Therefore, the results from Sdurlan red beds should not be used to determine paleolahtudes for central Newfoundland The mean paleolatltude of the Sprlngdale Group volcamcs is 30 ° The mean paleolatltudes for both the Sprlngdale volcanlcs and Botwood volcamcs (Lawrenceton Formation) are md~stmgmshable w~thm paleomagnetlc error hm~ts from the predicted paleolatltude of Newfoundland on the northeast-trending North American margin Thus, no detectable post-Silurian displacement ts shown by the volcamcs of the Sprmgdale Group with respect to cratomc North America.

Lithogeochemical and Sm-Nd and U-Pb isotope data from the Silurian–Lower Devonian Arisaig Group clastic rocks, Avalon terrane, Nova Scotia: A record of terrane accretion in the Appalachian-Caledonide orogen

“…Separation between Avalonia and Gondwana gradually increased during the Ordovician. Conversely, paleolatitudinal separation of Avalonia from Baltica and Laurentia disappeared by the Late Ordovician or Early Silurian (Miller and Kent, 1988;Van der Voo, 1988;McKerrow and Scotese, 1990;McKerrow et al, 1991;Soper and Woodcock, 1990;Trench and Torsvik, 1992;Potts et al, 1993;Dalziel et al, 1994;Golonka et al, 1994;Mac Niocaill and Smethurst, 1994;Hodych and Buchan, 1998;Mac Niocaill et al, 1997;Torsvik, and Rehnström, 2003). Paleontological evidence supports faunal linkages of Avalonia with Baltica by the Late Ordovician (e.g., Williams et al, 1995;Fortey and Cocks, 2003), whereas paleomagnetic data suggest that any paleolatitudinal separation between Avalonia and Laurentia had disappeared by the Early Silurian (Miller and Kent, 1988;Trench and Torsvik, 1992;Potts et al, 1993).…”

Laboratory depositional and compaction-caused inclination errors carried by haematite and their implications in identifying inclination error of natural remanence in red beds

“…To avoid this problem, Hodych & Buchan (1994) measured a partial anisotropy of IRM in haematite‐bearing samples by imparting IRM in increasingly greater magnetic fields at 45° to the bedding plane of the Silurian Springdale Group red bed samples from Newfoundland. Palaeomagnetic studies (Hodych & Buchan 1994; Potts et al 1994) indicate that these rocks have anomalously shallow inclinations although the palaeomagnetic direction from volcanic rocks has large errors (Potts et al 1994) probably caused by secular variations. In Hodych & Buchan (1994), reduces to assuming an infinite ‘ a ’ factor for haematite particles, and I IRM,45° as the inclination of IRM acquired in a magnetic field that has a 45° inclination to the bedding plane.…”

A Bayesian Approach to the Paleomagnetic Conglomerate Test

“…The solid black line marks the normalized location at which BF = 1 (corresponding to p ( H A | R ) = p ( H B | R ) = 0.5). Open circles represent published Watson () test results from Irving and Runcorn (), Al‐Khafaji and Vincenz (), Stewart and Irving (), Kluth et al (), Smith and Piper (), Jesinkey et al (), Symons and Wellings (), Symons (), Magnus and Opdyke (), Trench et al (), Buchan and Hodych (), Didenko (), Trench et al (), Allerton et al (), Potts et al (), Hodych and Buchan (), MacConnell et al (), Meert et al (), Huang and Opdyke (), Potts et al (), Bazhenov (), Levashova et al (), Geuna and Vizán (), Huang and Opdyke (), McCausland and Hodych (), Meyers et al (), Wynne et al (), Bazhenov et al (), Levashova et al (), Klootwijk (), Enkin et al (), Levashova et al (), Strik et al (), Villalaìn (), Weaver et al (), Hnat et al (), Levashova et al (), Metelkin et al (), Levashova et al (), Vérand (), Harlan and Morgan (), Levashova et al (), Biggin et al (), Levashova et al (), Abrajevitch et al (), Liu et al (), Çinku et al (), Li et al (), Tarduno and Cottrell (), Wen et al (), Werner et al (), Yi et al (), and Dare et al () (see supporting information for details). Of the 76 tests considered, 26 result in weak support and no test produced greater than positive support for uniformly random directions, according to our classification scheme (i.e., none of the tests achieve strong or very strong support for uniformly random directions).…”