Comment On: ‘Early Silurian Palaeolatitude of the Springdale Group Redbeds of Central Newfoundland: A Palaeomagnetic Determination With A Remanence Anisotropy Test For Inclination Error’ By J. P. Hodych and K. L. Buchan

摘要

Recent palaeomagnetic results from coeval Silurian sedimentary and volcanic rocks of Newfoundland yield contradictory results, with shallow characteristic directions recorded by the redbeds and steeper characteristic directions recorded by the volcanics. In their recent paper on the Springdale Group redbed, Hodych & Buchan (1994a) argue that the redbed magnetization is more reliable based on a fold test, dual-polarity magnetization, conglomerate test and an IRM acquisition experiment specifically designed to test for compaction or inclination error. Accordingly, these authors dismiss the volcanic results as well as the Silurian reference poles for Laurentia, citing possible remagnetization or other complications. However, we argue that the IRM experiments of Hodych & Buchan (1994a) are flawed and do not necessarily resolve the question of inclination error. Moreover, we point out that the conglomerate test is incomplete and that the proposed tectonic reconstruction based solely on the redbed magnetization implies a unique tectonic scenario that is incompatible with out present understanding of Silurian palaeogeography.