Magnetic Fabrics and Provenance Directions of Mid-Late Jurassic Pyroclastic Flows from the Northern Antarctic Peninsula

Abstract

The paleogeographic evolution of the Antarctic Peninsula during the Gondwana breakup remains poorly constrained. Reconstructing the eruptive sources of the voluminous Jurassic Chon Aike Province is crucial for refining or challenging existing tectonic models. This study presents new Anisotropy of Magnetic Susceptibility (AMS) data from Mid-to-Late Jurassic pyroclastic units in the northern Antarctic Peninsula to address these uncertainties. Bulk magnetic susceptibility values between 30–80 µSI, thermomagnetic curves, and hysteresis cycles indicate a normal (non-inverse) AMS fabric. Lack of evidence of tectonic overprint sustains a primary origin for the AMS fabric. Volcanic paleoflow directions were determined using K3 imbrication and, to a lesser extent, K1 magnetic lineations. Our results for the pirolastic Kenney Glacier Formation reveal a significant shift in volcanic sourcing: a source area located to the NW of Mount Flora in the basal units (Kenney 1 and lower Kenney 2 Members). A systematic change in the source area, coming from the ESE in Kenney 2 and 3 and from the SE in Kenney 4 Member. Integrating these results into a ~ 160 Ma paleoreconstruction, we propose a model for the Kenney Glacier Formation that aligns with current tectonic frameworks for the Graham Land Volcanic Group. In this restored geometry, flows originated from the SE (Kenney 1), shifting to the NNW (Kenney 2 and 3), and finally to the NE (Kenney 4). These findings provide evidence of shifting volcanic centers during the V2 episode of Jurassic magmatism in West Gondwana.