Paleogeographic and tectonic evolution of the Pampia Terrane in the Cambrian: New paleomagnetic constraints

ESCAYOLA, MÓNICA P.; RAPALINI, AUGUSTO E.; FRANCESCHINIS, PABLO R.; RODRÍGUEZ PICEDA, CONSTANZA; ESCAYOLA, MÓNICA P.; RAPALINI, AUGUSTO E.; FRANCESCHINIS, PABLO R.; RODRÍGUEZ PICEDA, CONSTANZA

TECTONOPHYSICS

ELSEVIER SCIENCE BV

Año: 2020 vol. 779

0040-1951

Paleomagnetic, magnetic fabric and rock magnetic studies were carried out in the late Middle to early LateCambrian Campanario Formation exposed in NW Argentina. The study also presents preliminary results from theEarly Cambrian metasediments of the Puncoviscana Formation and from Mojotoro intrusive. A new paleomagneticpole, C2, was computed for the Campanario Formation (23.6°N, 346.5°E, A95, 7.0°, N: 11 sites) fromthe localities of Tilcara (T), Terma de Reyes (R) and El Perchel (EP), including previous data from Santa VictoriaOeste (M), in northernmost Argentina. A positive fold test was obtained for Tilcara locality while a positiveregional tilt test was obtained for mean site directions for the four localities. This pole can be considered as therepresentative pole position for the Pampia terrane for the late Middle to Late Cambrian. Previous paleomagneticdata for the same formation from the Iruya-Matancillas locality show an in situ clockwise rotation of about 30°around a vertical axis when compared with the mean Pampia pole. The same is observed when comparing theearly Ordovician pole for the Santa Rosita Formation at those localities with the recently obtained coeval pole ofthe La Pedrera Formation, indicating that local tectonic rotations, affected that area. These results suggest thatprevious paleomagnetic interpretations for these Late Cambrian and Early Ordovician rocks in the region asrecording displacement of the Pampia terrane in Cambrian times are probably incorrect. Additionally, twovirtual geomagnetic poles were computed for the Puncoviscana Formation (TP1: 34.5°N, 52.3°E, A95: 5.0°, n: 22specimens and TP2: 38.3°N, 33.6°E, A95: 5.7°, n: 14 specimens) and one for the Mojotoro Intrusive (MO: 9.1°N,345.6°E, A95: 16.4°, n: 11 specimens). These and previous Early Cambrian paleomagnetic data from the Pampiaterrane differ from Gondwana coeval reference directions in inclination and/or declination, lacking a simplepattern.