Table 5.3.

Description and interpretation of sedimentary facies of Bajno Dolomite in the Moli Subgroup of Bijawar Group

Facies typeDescriptionInterpretationFacies thickness
Facies A: Algal laminite/Stromatolite
A.1.Stratiform or with low synoptic relief
 (a) Algal laminate
(i) Irregular, wavy/crinkly parallel laminations with occasional upward growth. (ii) Dolomitized, occasionally chertified. (iii) Upturned laminae resembling ‘teppe’ structureHorizontal crinkly laminated carbonates with occasional up-curving are identified as algal laminite (Beukes & Lowe 1989; Tucker 1982).
Occurrence of ‘tepee’ structure indicates intertidal to peritidal palaeo-environmental domain (Davies 1970)
2.3–7.5 m
 (b) Microdigitate stromatoliteHead diameter 0.7–2.5 cm and column height 2–7 cm; absence of wall structure. Series of interconnected columns look like a layerCommonly referred to as ‘tufa’ stromatolite (Grotzinger 1989) and assigned very shallow water intertidal to supratidal palaeogeography (Knoll et al. 1993)
A.2. Domal Stromatolite
 (a) Cabbage-headed
(i) Columns with symmetrical growth (inclination amount 30–40°). (ii) Large width: height ratio (2.5–3.2) with shallow and narrow intercolumn, giving cabbage-like shape to the columnsLow-energy condition, possibly at the back of any barrier (Sarkar et al. 1996), less wave or current action (Chakraborty 2004)1–1.20 m
 (b) Columns with high lateral and vertical extent(i) Tall, slender columns with very high height: width ratio. Individual columns often found growing from algal laminite, upwardly branched or unbranched and increase in diameter. Upward increase in the diameter of the column gives this stromatolite an inverted cone shape. Laterally these stromatolites show intercalation with facies A1(a) and A1(b)Such non-elongate, domal or linked domal stromatolites are commonly related to low-energy coastlines in protected peritidal setting or as deeper subtidal facies. The linked, clustered character suggests biohermal structure, possibly in the form of patch-reef0.50–0.70 m
 (c) Slender columns with deep inter columnsObserved, as lensoidal bodies, in association with subfacies types A2(a) and A2(b). Columns are either vertical or marginally curved. On bedding plane the columns show circular intersection. Narrow, deep intercolumns filled with coarse-grained granular calcareniteComparatively agitated environmental condition in shallow-water domain0.80–1 m
Facies B: Cross-stratified limestoneCosets of cross-stratification, planar tabular to planar-curved in geometry. Occasionally, cross-stratifications show downcurrent lateral transition to low-angle planar laminationProduct of curved crested bedform migration. High suspension load allowed down-current transformation of angular bedform to planar bedformAv. Coset thickness 0.45 m
Facies C: Intraclastic lime clast conglomerate
 (a) Pebbly, matrix-supported, massive, ungraded
(i) Wackestone-packstone (micrite content>85%) conglomerate beds composed of chaotic pebble/cobble-sized lime clast. (ii) Clasts are angular, show wide size variation (long axis varying between 0.5 and 5 cm), and generally with negligible grading or internal layer structuresHigh-viscosity debris flow, capable of transporting large-sized clasts (Middleton & Hampton 1976). Lack of grain sieving or basal erosion reflect deposition from high-density laminar flow (Lowe 1982; Mulder & Alexander 2001)0.35–0.045 m
 (b) Clast-supported massive or normal graded(i) Massive or with normal coarse-tail size grading. (ii) The large tabular clasts (28 cm) are characteristically bed-parallel. (iii) The base of the beds is often erosional with frequently present scoops. (iv) Amalgamated beds without any ordering in terms of bed thickness or clast-size variationGrading indicates deposition from turbulent suspension whereas bed-parallel orientation of clasts suggest operation of laminar flow (Enos 1977). Clasts derived locally and did not travel for long distance (Chakraborty et al. 2010). Strong basal shear. Recurrent turbidite emplacement in an area proximal to source area0.50–0.60 m
 (c) Matrix-supported conglomerate; reverse to normal graded(i) Centimetre to decimetre-thick tabular, parallel-sided beds with basal calcirudite and overlying mudstone; clast-supported fabric within the carbonate subdivision resulted from high concentration of pebble-sized clasts. (ii) Sparse clasts concentration within the mudstone interval, contact between the two subdivisions erosional; at times, diffused. Clasts, in general, are bed parallel; only at the transition to mudstone subdivisionHigh-density turbidity current with a laminar near-bed layer and a turbulent rider (Einsele 2000). A flow separation resulted in a viscous, non-turbulent, inertia-flow layer below and a turbulent layer above, the interface between the two being a physical discontinuity (Felix & Peakall 2006)0.40–0.60 m
Facies D: Alternate thick- and thin- bedded limestone(i) Alternation of decimetre-thick mud-free tabular bedded dolosiltite with thin (7–12 cm thick) bedded calcilutite. Internally, the thick beds are massive; their upper and lower contacts with the thin-bedded units are sharp, planar and non-erosional. (ii) The thin-bedded limestones are with thin (2–3 mm thick) mud partings; often the mud stringers give stylolitic appearanceHigh-density turbidity current (Branney & Kokellar 1992; Kneller & Branney 1995). Deposition in interludes of turbidite deposition12–14 m
Facies E: ShaleCentimetre- to decimetre-thick dark coloured compact shale alternating with centimetre-thick calcisiltite interbedsRelatively deeper water setup, dominantly below storm wave base (Chakraborty & Paul 2008)5.5 m