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

Table 3

Characteristic features of multi-scale erosional surfaces.

Characters	Sequence-scale erosion surface	Parasequence-scale erosion surface	Event-scale erosion surface
Relief	More than 25 mm	Range between 8 and 20 mm	<5 mm
Surface nature	Irregular, scoured, cutting down	Sharp, irregular to gradational	Sharp
Lithofacies	siliceous non calcareous mudstone and Siliceous calcareous mudstone	Siliceous non calcareous mudstone and Siliceous calcareous mudstone	Clay-rich mudstone facies
Reworked concretions	Rounded to subrounded shale intraclasts	Subrounded phosphatic pellets	Calcareous concretions
Shelly laminae	Highly compacted and horizontally oriented shell fragments	Traces of thin disconnected shelly laminae	Rarely occurred
Shale rip-up clasts	Rarely occurred	Common	Rarely occurred
Spectral gamma ray pattern	Abrupt change (decreasing and increasing)	Marking the end of upward increasing or decreasing spectral Gamma Ray pattern	Does not Apply
Energy levels	High energy enough to reworked shale intraclasts and other components	Low energy where the shale rip-up clasts suspended in the sea bed layer	Low bottom energy levels