Ichnofabrics from muddy shallow-water bottom current deposits, Upper Jurassic to Lower Cretaceous Vaca Muerta Formation, Argentina

Bottom currents induced by thermohaline-, wind-, or tide-driven circulation may occur in shallow waters (50-300 m water depths), such as in outer shelves, upper slopes and shallow sills. The Upper Jurassic-Lower Cretaceous Vaca Muerta Formation in Argentina shows drift deposits located in bottomsets and foresets of a mixed carbonate-siliciclastic, shelf-margin, subaqueous clinoform system that can be analyzed to enhance understanding of ichnofabrics associated with shallow-water bottom current sedimentation. In addition, this formation represents one of the most important unconventional reservoirs in the world, displaying high TOC levels. The drift deposits were recorded in cores from five wells (660.5 m total) located in areas that are currently explored and developed by oil and gas companies. These deposits are composed of massive, cross-bedded and parallel, low angle-and wavy-laminated crinoidal mudstone; crinoid-rich lenses; coarse mudstone laminae encased in fine mudstone; massive, parallel-, low-angle and current-ripple cross-laminated, fine to coarse mudstone; and massive, normal-graded and composite beds of calcareous, fine to coarse mudstone.