Table 3 Brief descriptions and interpretations of the facies types within the channel-fill facies association (FA-1)

Facies 1A: Clast-supported conglomerate

Lenticular, clast-supported polymictic conglomerate non-conformably overlying basement rocks; facies thickness upto 90 cm; clasts vary in composition, angular to sub-angular, randomly oriented; sandy matrix.

Deposited as small channel lag or longitudinal braided bars of low-sinuous streams (Miall 2006; Malaza et al. 2013).

Facies 1B: Matrix-supported conglomerate

Sandy-matrix-rich, texturally immature, lenticular conglomerate, locally interbedded with sandstone; clasts of quartz, jasper, basement rock fragments, and few mud clasts; Clasts sub-rounded, 2–10 cm in diameter, randomly oriented.

Debris flow deposit (Miall 1982) with scooping of underlying cohesive, unconsolidated mud (Bhattacharya and Bhattacharya 2012).

Facies 1C: Pebbly sandstone

Persistently developed in all sections; moderately-sorted, subrounded coarse- to medium-grained sandstone with large-scale trough cross-strata (set thickness 50–55 cm) changing to small trough cross-strata (set thickness 20–30 cm) near top of beds; facies thickness upto ~2.5 m; angular to sub-angular, poorly-sorted pebble layers separate the sandstone beds.

Alternate pebble-rich and pebble-poor layers indicate alternate high-energy and relatively low-energy conditions, respectively; migration of bars in low-sinuous high-gradient meandering streams (McGowen and Garner 1970; Miall 1982).

Facies 1D: Trough cross-stratified sandstone

Medium- to coarse-grained, moderately-sorted, angular to subrounded sandstone with trough cross-strata; local pebble concentration common; small-scale asymmetrical ripples preserved on bed tops; abundant in all sections with thicknesses of 5 cm – >50 cm.

Migration of channel bars (Best and Kostaschuk 2002); pebbles indicates fluctuating energy.