Early Silurian paleolatitude for central Newfoundland from paleomagnetism of the Wigwam Formation: Discussion

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.