AMS AND PETROFABRIC OF JURASSIC VOLCANIC UNITS FROM HOPE BAY (BAHÍA ESPERANZA), ANTARCTIC PENINSULA

MILANESE, FLORENCIA NIDIA; IACONO, LAILA; FRANCESCHINIS, PABLO REINALDO; PUIGDOMENECH, CARLA; FEO, RODRIGO; GIL, JOAQUÍN; LOZANO, JORGE; GUMINA, MIGUEL; LIRIO, JUAN MANUEL; RAPALINI, AUGUSTO ERNESTO

Pucón

Congreso; XI SCAR Open Science Conference; 2024

We present an Anisotropy of Magnetic Susceptibility (AMS) study carried out on paleomagnetic samples from Hope Bay area, including a total of 453 (n=453) specimens coming from twenty-two sites (N=22). Three sites from the twenty-two (N=3) correspond to two tuff levels intercalated in the fossiliferous Middle-Upper Jurassic Mount Flora Formation. After making the tectonic correction, the lower tuff from Mount Flora Formation presents an excellent grouping of the axes of minimum (k3) and maximum (k1) susceptibility in the vertical and WSW-ENE directions, and an oblate anisotropy ellipsoid. This suggests a sedimentary fabric with a WSW-ENE flow direction. The upper tuff shows a much more chaotic fabric, with both prolate and oblate ellipsoids. Eleven sites (N=11) correspond to the volcanic and volcaniclastic units from Upper Jurassic Kenney Glacier Formation. These units also show very well defined groupings of k3 axis, but these groupings present different directions of ?imbrication depending on the sampling site. Anistropy ellipsoids are equally prolate and oblate and a rough grouping of k1 in the WSW-ESE direction is also observed. The remaining eight sites (N=8) correspond to two Cretaceous intrusive bodies and two dykes that outcrop in the surrounding area of Mount Flora, where Jurassic outcrops are concentrated. These ellipsoids are also oblate and prolate but ASM fabrics do not appear to be very well-defined. Bulk magnetic susceptibilities present a wide variation, being mean values between 15E-6 and 2E-3 SI. Lower values correspond to Jurassic rocks. The parameter of anisotropy P does not exceed 1.16 in most cases.