Open AccessPalaeomagnetism of the Cretaceous El Way and Coloso Formations From the Northern Chilean Andes
Author(s) -
Tanaka H.,
Tsunakawa H.,
Amano K.
Publication year - 1988
Publication title -
geophysical journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0952-4592
DOI - 10.1111/j.1365-246x.1988.tb00460.x
Subject(s) - geology , paleomagnetism , cretaceous , dike , clockwise , paleontology , apparent polar wander , rotation (mathematics) , geometry , mathematics
Summary A palaeomagnetic study mainly of limestones of the El Way Formation and fine sandstone of the Coloso Formation near Antofagasta, northern Chile (23.83°S, 70.38°W), gives an early Cretaceous palaeomagnetic pole (76.4°S, 150.7°E, A 95 = 6.4°) for the Chilean Andes. Comparison of this pole with the SAKl pole of Valencio et al. (1983) for cratonic South America suggests a relative clockwise rotation of 12°±9°. Considered in isolation, little confidence can be placed in this possible rotation because of its large error and non‐small flattening of ‐10°± 10°. However, if the pole is combined with all available late Jurassic and Cretaceous palaeomagnetic poles from the Andes, it is very clear that the poles group according to the geographical location of their sampling areas: Peruvian Andes, hinge part of the Andes and Chilean Andes. the rotation angle between the two blocks calculated from the Peruvian Andes mean pole and the Chilean Andes mean pole amounts to a significant 41°± 18°, assuming the rotation centre is located at the hinge of the coast. A Jurassic sandstone of the Arica Group from Cuya in northernmost Chile seems to have been completely thermally remagnetized by Cretaceous dike swarms which intrude the sandstone. the site mean direction of the sandstone is indistinguishable from that of the dike swarms whose palaeomagnetism has been studied by Nomura et al. (1983).