Active faulting in the Beagle Channel (Tierra del Fuego)

Abstract

In Tierra del Fuego, the Magallanes-Fagnano Fault System (MFFS) accommodates a significant portion of the relative motion between the South America and Scotia plates. However, it remains unclear whether some of the deformation is partitioned southwards, along the Beagle Channel Fault System (BCFS). In this paper, high-resolution seismic reflection profiles were used to identify fault-related ruptures in the submerged Quaternary sediments of the Beagle Channel. Some faults reach the seafloor, affecting marine sediments, indicating they are Holocene in age. The correlation with outcrop data and lineaments mapped onshore suggests the post-glacial reactivation of two structures: the E-W striking BCFS and the NW-SE-trending Lapataia Fault Zone (LFZ). Whereas the BCFS displays along-strike variation in throw, the LFZ shows significant normal displacements. These results imply that deformation occurs in a wider and more complex manner than previously thought and highlight the need for a thorough hazard assessment of the area.