Palaeomagnetism of the Permo-Triassic Araguainha impact structure (Central Brazil) and implications for Pangean reconstructions

Autor(es)

Yokoyama, Elder ^[1] ; Brandt, Daniele ^[1] ; Tohver, Eric ^[2] ; Trindade, Ricardo I. F. ^[1]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Inst Astron Geofis & Ciencias Atmosfer, BR-05508090 Sao Paulo - Brazil

^[2] Univ Western Australia, Sch Earth & Environm, Crawley, WA 6009 - Australia

• Tipo de documento: Artigo Científico
• Fonte: Geophysical Journal International; v. 198, n. 1, p. 154-163, JUL 2014.
• Citações Web of Science: 4

Resumo

The configuration of the Pangea supercontinent has been a topic of intense debate for almost half a century, a controversy that stems from discrepancies between the geology-based Pangea-A and the palaeomagnetically based Pangea-B. Recent palaeomagnetic compilations aimed at resolving this controversy have identified the poor quality of palaeomagnetic data from Gondwana for Permian times as a major obstacle. Specifically, the vast majority of Gondwanan poles come from sedimentary rocks that are prone to biases from compaction or are poorly dated. Here, we present a new palaeomagnetic pole for cratonic South America based on impact melts from the 254.7 +/- 2.5 Ma Araguainha impact structure (AIS). The granite basement, the impact-generated melt sheet and veins were sampled at 28 sites (169 specimens) and provided a reliable palaeomagnetic record similar to that of volcanic rocks. Alternating field and thermal demagnetization indicate a stable characteristic remanent magnetization carried by both magnetite and haematite. All sites but one show a single palaeomagnetic direction of normal polarity with a mean direction of Dec = 357.4 degrees; Inc = -38.9 degrees; N = 28; k = 62.35; alpha(95) = 3.5 degrees, yielding a palaeomagnetic pole (AIS) at Lat = -84.2; Lon = 326.6; K = 83.5; A(95) = 3.6 degrees.; S-B = 9.6 degrees. The new pole provides a firm constraint on the position of Gondwana which is consistent with the Pangea A configuration. (AU)

• Processo FAPESP: 05/51530-3 - Caracterização geofísica e petrofisica da estrutura de impacto de Araguainha (MT/GO)
• Beneficiário: Yára Regina Marangoni
• Modalidade de apoio: Auxílio à Pesquisa - Regular