Coniacian-Campanian magnetostratigraphy of the Marambio Group: The Santonian-Campanian boundary in the Antarctic Peninsula and the complete Upper Cretaceous – Lowermost Paleogene chronostratigraphical framework for the James Ross Basin

MILANESE, FLORENCIA N.; OLIVERO, EDUARDO B.; SLOTZNICK, SARAH P.; TOBIN, THOMAS S.; RAFFI, MARÍA E.; SKINNER, STEVEN M.; KIRSCHVINK, JOSEPH L.; RAPALINI, AUGUSTO E.

PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY

ELSEVIER SCIENCE BV

Año: 2020 vol. 555

0031-0182

Recent magnetostratigraphic works from different areas of the James Ross Basin have expanded on chronostratigraphic studies previously based on ammonite, palynomorph and nanoplankton biostratigraphy, andstrontium isotope stratigraphy. Here we present a new magnetostratigraphy of Coniacian through Campanianmarine sedimentary rocks from Hidden Lake, Santa Marta and Snow Hill Island Formations, on northwest JamesRoss Island. A total of 189 paleomagnetic directions were obtained along more than 1500 m of stratigraphicthickness from Brandy Bay to Santa Marta Cove areas, identifying three polarity chrons of the global polaritytime scale. The local magnetostratigraphic column starts in the upper part of the Cretaceous Normal SuperchronC34N (Coniacian) and ends in Chron C33N (middle Campanian). The correlation between the magnetostratigraphy and the age framework given by ammonite biostratigraphy allowed the assignment of precise ages toparticular horizons of the Santa Marta Formation. The newly identified geomagnetic polarity reversals are theearliest identified in the James Ross Basin and include: a) C34N/C33R (84.2 Ma, late Santonian ? earlyCampanian) in the Alpha Member of the Santa Marta Formation and b) C33R/C33N (79.9 Ma, middleCampanian) in the upper Beta Member (Santa Marta Formation). By integrating this new data with previouswork, we present a complete Upper Cretaceous ? lowermost Paleogene chronostratigraphical framework for thebasin, spanning both proximal to distal sedimentary facies of the Marambio Group.