Discovery of an active crater-like mud volcano at ∼42°S on the Chilean margin: structural controls and gas hydrate associations

Abstract

Submarine mud volcanoes (MVs) are seafloor features commonly found in tectonically active margins with high sedimentation and compressional regimes. This study reports the first discovery of a prominent crater-like mud volcano on the Chilean margin, named the Cucao Mud Volcano (CMV), located ∼86 km offshore Chiloé Island (∼42°S) at a depth of 1800 m. Multichannel seismic data reveal that the CMV is structurally emplaced along the crest of a faulted anticline within a transpressional setting, indicating that tectonic deformation governs both its morphology and fluid pathways. A strong, continuous Bottom Simulating Reflector (BSR), seismic blanking, bright spots, and chaotic facies in the shallow subsurface suggest the presence of gas hydrates, free gas, and active fluid migration. High-resolution multibeam bathymetry and backscatter mosaics show a caldera-like edifice with a central crater, dome-shaped flanks, and surrounding depressions. Comparative data from 2012 to 2018 indicate reduced surface activity, possibly reflecting a transition to a quiescent phase. Additionally, dome-shaped reflectors above the BSR suggest diapir-like intrusions and vertical conduits associated with gas hydrate dissociation and overpressure. These findings underscore the complex interplay between tectonics, gas hydrate systems, and mud volcanism, positioning the CMV as a key site for understanding fluid dynamics along convergent continental margins.