Paleomagnetism of the Ediacaran Avellaneda Formation (Argentina), Part II: Magnetic and chemical stratigraphy constraints on the onset of the Shuram carbon excursion

Magnetostratigraphy is a powerful technique for high-resolution stratigraphic correlation and accurate dating of the polarity history of the magnetic field. Up to now, magnetostratigraphic studies have been underutilized in Ediacaran successions. Here, we present a magnetostratigraphy coupled with a carbon isotope study in Ediacaran Avellaneda Formation (similar to 570 Ma), a sedimentary cover sequence in the Tandilia orogenic belt, of the Rio de la Plata craton. Paleomagnetic results and delta C-13 profiles were obtained from three drill cores that cut across the sedimentary record of the Avellaneda Formation. Paleomagnetic results plotted stratigraphically allowed the identification of a prevalent reverse polarity separated by normal polarity interval. Our findings show a coincident correlative polarity transition at each drill core analyzed. delta C-13 values demonstrate that the magnetostratigraphic polarity pattern is laterally consistent. Furthermore, C-isotope curves show a transition from positive to negative values near the top of the Avellaneda Formation. This excursion is likely correlative with the onset of the Shuram excursion (ca. 570 Ma). Our findings suggest that the onset of Shuram excursion took place during a reverse polarity chron. Comparison with other coeval sequences validate this correlation. Geomagnetic polarity reversals pattern in the Avellaneda Formation and its correlative pattern, validates a magnetostratigraphy as a potential method to correlate Precambrian strata. Our new findings shed further light on the possible use of magnetic polarity reversals to correlate Ediacaran successions.

Automated summary

This study presents a magnetostratigraphy coupled with a carbon isotope study in the Ediacaran Avellaneda Formation, which reveals a correlation between magnetic polarity pattern and carbon isotope changes associated with the Shuram excursion. The findings show the potential use of magnetostratigraphy for Precambrian stratigraphic correlation and shed further light on Ediacaran succession correlations.