Age constraints on the Cambrian Mesón Group (NW Argentina) based on detrital zircons U–Pb geochronology and magnetic polarity bias

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

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2020 vol. 104

0895-9811

The Cambrian Mes´on Group represents the first infill stages of the NW Argentina Paleozoic basin, given after themajor orogenic event represented by the Tilcaric orogenic phase. This unit extends for several hundred kilometersalong the Eastern Cordillera in the provinces of Salta and Jujuy, but its age is poorly constrained due tothe paucity of fossil evidence and scarce geochronological data. U?Pb LA-ICP-MS geochronological studies werecarried out on detrital zircons from the Lizoite, Campanario and Chalhualmayoc formations, that make up theMes´on Group, in outcrops in the Santa Victoria sub-basin in northernmost Argentina. Maximum depositionalages of 524.8 ± 4.1, 519.7 ± 2.4 and 508.6 ± 1.7 Ma were obtained for these formations, respectively. These newdata, together with previous detrital zircon ages from southernmost outcrops of this Group, points to a possiblediachronism in deposition, with younger ages towards the south. In our studied units, a dominant peak ofCambrian to late Ediacaran zircons is characteristic for the three formations, although a somewhat largercontribution from older crystals is observed in the Campanario and Chalhualmayoc formations. This pattern issimilar to most other reported detrital zircon age spectra for the Mes´on Group along the basin. Publishedpaleomagnetic data for the Campanario Formation indicates a very strong reverse magnetic polarity bias, whichallows us to infer three more likely intervals for the deposition of this formation (roughly 512?510, 509?505 and497-493 Ma). These three alternatives are analyzed with respect to either major diachronous or roughly synchronousdeposition of the Mes´on Group sediments across the whole basin. Published magnetic fabric data forthe Campanario Formation at three distant localities suggest possible paleocurrent directions from W to E.