Banganapalli Quartzite Fm

Coarse-grained sandstone: Quartz arenite, basal conglomerate. The Banganapalle Quartzite (40-50 m), includes a massive, polymictic, matrix- to clast-supported basal conglomerate intercalated with trough cross-stratified, pebbly to gritty feldspathic sandstone or subarkose. Subangular to subrounded pebble to boulder size clasts of vein quartz, feldspar, chert, quartzite, occasional granite (granite-gneiss), and slate/ phyllite, derived from the underlying basement, are set in variable proportions of sandy to gritty matrix in the basal conglomerate with local crude layering defined by clast alignment. The sheet-like massive conglomerate to pebbly sandstone with wavy upper bounding surface, grade upward to a medium to fine quartz arenite with thin muddy intercalation. Sedimentary structures include profuse wave ripples, interference ripples, flaser bedding, and syneresis/desiccation cracks (Fig. images A and B below).

The upper 30-40 m of the Banganapalle succession around Jaggayapeta in the Paland sub-basin consists of medium- to fine-grained quartz arenite beds with tabular geometry commonly showing wavy planar or hummocky-swaley stratification, locally with intervals of trough cross-stratified beds. The gentle wavy laminae within the wavy planar beds conform to the upper bounding surface and successive beds are separated by several millimeter thick mud partings showing ripple lamination. The wavy bedded to hummocky cross-stratified units grade upward to a plane laminated, heterolithic siltstone-shale, the latter being calcareous in the uppermost part.

[Field photographs showing lithology and sedimentary features in the Kurnool Group. Banganapalle Quartzite Fm – (A) basal conglomerate of overlying granitic basement, and (B) thick matrix supported polymict conglomerate with apparent size grading. Narji Limestone Fm - (C) lower part with thin wavy bedded impure limestone, and (D) glauconitic sandstone interbeds in limestone; note pockets of lime pebble conglomerate. Owk Shale Fm - (E) Thinly laminated ash beds, and (F) transition from Owk Shale (lower half of photo) to Paniam Quartzite Fm. Paniam Quartzite Fm - (G) truncated wavy lamination. Koilkuntla Limestone Fm - (H) thin bedded argillaceous limestone, and (I) impure limestone-shale intercalation within the Koilkuntla Limestone Fm to Nandyal Shale Fm transition. (from Saha et al., 2016)]

Gravelly alluvial fan to braid plane, to lower shoreface. The basal part of the Banganapalle Quartzite with massive to crudely stratified debris-flow conglomerate and interbedded subarkosic coarse to gritty sandstone has been interpreted as gravelly alluvial fan to braid plane deposits at tectonically active semiarid basin margin. The sheet-like geometry of the conglomeratic units and pebbly sandstone beds with wavy upper bounding surface imply wave dominated foreshore to shoreface depositional setting, with wave reworking of relict fluvial sediments in a transgressive sequence. The ripple laminated quartz arenite with thin muddy partings showing profuse wave interference ripple structures, desiccation cracks and flaser bedding indicate deposition in a foreshore environment with intermittent subaerial exposure. The association of low-angle crossstrata, wavy laminations, hummocky-to-swaley cross-strata, and wave ripple cross-lamination in the quartz arenite has been interpreted as intermittent storm deposits in the lower shoreface region under influence of combined flow.