Magnetostratigraphy and mid-palaeolatitude VGP dispersion during the Permo-Carboniferous Superchron: results from Parana Basin (Southern Brazil) rhythmites

Autor(es)

Franco, Daniel R. ^{[1, 2]} ; Ernesto, Marcia ^[1] ; Ponte-Neto, Cosme F. ^[2] ; Hinnov, Linda A. ^[3] ; Berquo, Thelma S. ^[4] ; Fabris, Jose D. ^[5] ; Rosiere, Carlos A. ^[6]

Afiliação do(s) autor(es)

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

^[2] Observ Nacl, Coordenacao Geofis, BR-20921400 Rio De Janeiro, RJ - Brazil

^[3] Johns Hopkins Univ, Dept Earth & Planetary Sci, Baltimore, MD 21218 - USA

^[4] Concordia Coll, Dept Phys, Moorhead, MN 56562 - USA

^[5] Univ Fed Minas Gerais, Dept Quim, BR-31270901 Belo Horizonte, MG - Brazil

^[6] Univ Fed Minas Gerais, Inst Geociencias, BR-31270901 Belo Horizonte, MG - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Geophysical Journal International; v. 191, n. 3, p. 993-1014, DEC 2012.
• Citações Web of Science: 7

Resumo

A detailed magnetostratigraphic and rock-magnetism study of two Late Palaeozoic rhythmite exposures (Itu and Rio do Sul) from the Itarare Group (Parana Basin, Brazil) is presented in this paper. After stepwise alterning-field procedures and thermal cleaning were performed, samples from both collections show reversed characteristic magnetization components, which is expected for Late Palaeozoic rocks. However, the Itu rocks presented an odd, flat inclination pattern that could not be corrected with mathematical methods based on the virtual geomagnetic pole (VGP) distributions. Correlation tests between the maximum anisotropy of the magnetic susceptibility axis (K1) and the magnetic declination indicated a possible mechanical influence on the remanence acquisition. The Rio do Sul sequence displayed medium to high inclinations and provided a high-quality palaeomagnetic pole (after shallowing corrections of f = 0.8) of 347.5 degrees E 63.2 degrees S (N = 119; A95 = 3.3; K = 31), which is in accordance with the Palaeozoic apparent wander pole path of South America. The angular dispersion (Sb) for the distribution of the VGPs calculated on the basis of both the 45 degrees cut-off angle and Vandamme method was compared to the best-fit Model G for mid-latitudes. Both of the Sb results are in reasonable agreement with the predicted (palaeo) latitudinal S-? relationship during the Cretaceous Normal Superchron (CNS), although the Sb value after the Vandamme cut-off has been applied is a little lower than expected. This result, in addition to those for low palaeolatitudes during the Permo-Carboniferous Reversed Superchron (PCRS) previously reported, indicates that the low secular variation regime for the geodynamo that has already been discovered in the CNS might have also been predominant during the PCRS. (AU)

• Processo FAPESP: 02/06480-0 - Investigação acerca do caráter anual dos ritmitos permocarboníferos da bacia do Paraná através da magnetoestratigrafia e magnetismo de rochas
• Beneficiário: Daniel Ribeiro Franco
• Modalidade de apoio: Bolsas no Brasil - Doutorado