Palaeomagnetism of the Itajai, Castro and Bom Jardim groups from southern Brazil

Abstract

Palaeomagnetic results corresponding to geological units associated with the Brasiliano (Pan‐African) cycle (Late Pre‐Cambrian ‐ Early Palaeozoic), are presented. A total of 160 hand samples from the Itajaí, Castro and Bom Jardim Groups from southern Brazil were submitted to laboratory treatment. 46 acid volcanic samples from the Campo Alegre Formation (Itajaí Group) yielded two magnetic components labelled A1 (Dm= 36d̀, Im= ‐40d̀, A95= 10d̀) and A2 (Dm= 44d̀, Im= ‐8d̀, A95= 4d̀) with respective palaeomagnetic poles CA (223d̀E, 57d̀S, A95= 9d̀) and SV (200d̀E, 43d̀S). 20 acid volcanic samples from the Castro Group yielded a single stable direction of magnetization (Dm= 347d̀, Im= ‐52d̀, A95= 12d̀) with palaeopole CT (4d̀E, 76d̀S, A95= 15d̀). 12 acid samples from the Acampamento Velho Formation (Bom Jardim Group) yielded two magnetic components labelled B1 (Dm= 156d̀, Im= 69d̀, A95= 17d̀) and B2 (Dm= 207d̀, Im= ‐15d̀, A95= 42d̀) with respective palaeopoles AV1 (338d̀E, 61d̀S, A95= 28d̀) and AV2 (345d̀E, 44d̀N A95= 37d̀). Seven sedimentary samples from the Vargas Formation (Bom Jardim Group) yielded a magnetic component (Dm= 110d̀, Im= 81d̀, A95= 17d̀) with palaeopole VA (322d̀E, 34d̀S, A95= 30d̀). Finally, 11 andesitic volcanic samples yielded a magnetic component (Dm= 108d̀, Im= ‐4d̀, A95= 12d̀) with palaeopole Hi (228d̀E, 14d̀N, A95= 9d̀). These results are compared with APWP's constructed for the Gondwana Continents. Copyright © 1988, Wiley Blackwell. All rights reserved