Microstructural study of natural fractures in Cape Roberts Project 3 core, Western Ross Sea, Antarctica

Microstructures in natural fractures in core recovered offshore from Cape Roberts, Ross Sea, Antarctica,
provide new constraints on the relative timing of faulting and sedimentation in the Victoria Land Basin along the
Transantarctic Mountain rift flank. This study characterizes the textures, fabrics and grain-scale structures from thin
section analysis of samples of microfaults, veins, and clastic dikes. Microfaults are abundant and display two different
types of textures, interpreted to record two different deformation modes: pre-lithification shearing and brittle faulting of
cohesive sediment. Both clastic dikes and calcite veins commonly follow fault planes, indicating that injections of
liquefied sediment and circulating fluids used pre-existing faults as conduits. The close association of clastic injections,
diagenetic mineralization, and faulting indicates that faulting was synchronous with deposition in the rift basin