Relationship between faulting and fluid migration in and around Leirdjupet Fault Complex

Abstract

This study investigates the spatial relationship between ice-flow direction (inferred from Mega-Scale Glacial Lineations, MSGLs) and subvertical amplitude anomalies in the southwestern Barents Sea. The focus area is in and around the Leirdjupet Fault Complex, a tectonic boundary separating the Bjørnøya Basin from the Fingerdjupet Subbasin. Interpretation of a 3,757 km² 3D seismic cube, complemented by high-resolution 2D seismic lines from the CAGE17-3 cruise, is used to map subvertical amplitude anomalies, seafloor pockmarks, and related features interpreted as fluid migration pathways. The anomalies are commonly associated with faults, including both large fault complexes and smaller-scale faulting that in several cases breach the Fuglen Formation, a regionally important seal. Observations such as vertically stacked pockmarks, buried depressions, and reversed polarity reflections suggest repeated or long-lived fluid flow. The spatial relationship between MSGLs and the underlying anomalies is evaluated, and while their orientations differ, glacial cycles, particularly post-glacial rebound, stress changes, and possible gas hydrate dissociation, may have played a role in triggering fluid expulsion. The results indicate that fluid migration in the area is influenced by a combination of tectonic structures and glacial processes, involving both thermogenic and biogenic fluid sources.