Reply to Comment By Stamatakos Et Al. On ‘Early Silurian Palaeolatitude of the Springdale Group Redbeds of Central Newfoundland: A Palaeomagnetic Determination With A Remanence Anisotropy Test For Inclination Error’

Stamatakos et al. raise several objections to our recent palaeomagnetic study of the Springdale Group redbeds of Newfoundland. We discuss their comments below. In their summary, Stamatakos et al. comment that ‘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’. However, the Newfoundland volcanics that give steeper magnetic inclinations lie stratigraphically beneath and, hence, are not coeval with the redbeds (the few volcanic sites within the redbed stratigraphy have shallow inclinations). In the case of the Botwood Group, a portion of the redbeds of the Wigwam Formation are likely to be of Ludlow age according to new fossil evidence (Boyce & Ash 1994) and U-Pb ages of about 423 Ma (Dunning et al. 1990) for igneous rocks that are thought to intrude or overlie the Wigwam Formation. On the other hand, the volcanic rocks of the underlying tawrenceton Formation are older, with Colman-Sadd (1994) proposing a probable Llandovery C3 age for the base of the Formation. Therefore, any difference in magnetic inclination could be due, at least in part, to drift of central Newfoundland to lower palaeolatitudes between the time of emplacement of the volcanic rocks and the deposition of the redbeds. Stamatakos ef al. also imply that our ‘tectonic reconstruction (is) based solely on the redbed magnetization’. In fact, we utilize results from redbeds and minor intercollated volcanic rocks of Newfoundland and both redbeds and volcanic rocks of Britain (see our Table 3 and Fig. 10).