Multiscale Erosion Surfaces of the Organic-Rich Barnett Shale, Fort Worth Basin, USA

Table 2

Characteristic features of erosion surfaces in both the proximal and the distal muddy settings.

Characters	Proximal muddy settings	Distal muddy settings
Boundary nature	Irregular, scoured, cutting down, gradational to irregular	Sharp to irregular
Lithofacies	Calcareous-rich mudstone facies with dolomitic cementation	Clay-rich mudstone facies with pyritic cementation
Reworked concretions	Rounded to subrounded calcareous shale intraclasts	Rounded to subrounded phosphatic pellets
Shelly laminae	Reworked shell fragments	Compacted shelly laminae
Shale ripup clasts	Rarely occurred	Elongated, flaky with sharp edges
Energy levels	High energy enough to include reworked shale intraclasts and other components	Low energy where the shale rip-up clasts are suspended in the sea bed layer