DISCORDANT SILURIAN PALEOLATITUDES FOR CENTRAL NEWFOUNDLAND - NEW PALEOMAGNETIC EVIDENCE FROM THE SPRINGDALE GROUP

Ancient remanences are retained by the Early Silurian (429 + 6/ - 5 Ma ) mafic volcanics of the Springdale Caldera (five sites) and the overl ying red beds (seven sites). Dual polarity magnetizations are obtained by thermal demagnetization of samples from the red beds, whereas sing le polarity directions are observed in the volcanics. High unblocking temperatures indicate hematite as the remanence carrier in both the vo lcanics and sediments. These high-temperature, characteristic remanenc es are easily isolated and pass both the tilt and conglomerate tests; they are likely to be of primary Silurian age. Characteristic declinat ions are predominantly northerly and northeasterly, and indicate signi ficant structural rotations on a local scale. When the results of the red beds and the volcanics are combined they show characteristic incli nations that are shallower than those of the correlative Botwood Group (ca. 36-degrees vs. 43-degrees) but not nearly as shallow as those re ported from the King George IV Lake area (0.5-degrees). Mean inclinati ons obtained from the Springdale red beds are, however, significantly shallower than those of the Springdale volcanics. The same difference can be seen in other previous Silurian paleomagnetic studies of centra l Newfoundland. We infer that an inclination error affects the red bed magnetizations of the Springdale Group, Botwood Group (Wigwam Formati on) and rocks of the King George IV Lake area. Therefore, the results from Silurian red beds should not be used to deter-mine paleolatitudes for central Newfoundland. The mean paleolatitude of the Springdale Gr oup volcanics is 30-degrees. The mean paleolatitudes for both the Spri ngdale volcanics and Botwood volcanics (Lawrenceton Formation) are ind istinguishable within paleomagnetic error limits from the predicted pa leolatitude of Newfoundland on the northeast-trending North American m argin. Thus, no detectable post-Silurian displacement is shown by the volcanics of the Springdale Group with respect to cratonic North Ameri ca.