Table 2 Description and interpretation of sedimentary facies (lithofacies codes modified after Miall 1985, 2006; supplemented and modified after Salehi et al. 2014a)
| Â | Facie code | Characteristic | Petrofacies | Sedimentary processes; environmental interpretation | Occurrence |
|---|---|---|---|---|---|
1 | Gcm | Clast-supported polymictic conglomerates, pebble to granule with rare boulder grain-size, low roundness (subangular) and sphericity, very poor sorting, immature conglomerate, with reddish brown sandy matrix, common clast includes sedimentary rocks (red sandstone or siltstone and milky chert), massive or crudely stratified, marked by erosional and sharp base and upper contact is usually gradational with Sh and St, thickness ranging from 0.5 to1 m | Polymictic conglomerates | Deposition by rapidly waning flow regime, with sediment transport occurring via traction currents and marked by high sediment supply from the land. Deposition in fluvial channels | Sections A–B (Fig. 7a) |
2 | St | Trough cross-bedded sandstone, medium—to coarse-grained sand, rounded and high sphericity, good sorting, mature sandstone, set thickness generally 3–5 m, lenticular or wedge-shaped bodies, gradational with facies Gt and is erosional with facies Fm | Litharenite (chertarenite, phyllarenite, sedarenite) | Deposited as dunes or bars in response to unidirectional currents (e.g. Miall 2006); Deposition in fluvial channel; delta plain and front; upper shoreface | Sections A–C (Fig. 7b) |
3 | Se | Erosional scours with intraclasts, medium—to coarse-grained sand sometimes pebbly at base, solitary or grouped sets; set thickness generally 5–20 cm, associated with St | Litharenite (chertarenite, phyllarenite, sedarenite) | Dunes and scour fills in fluvial and delta plain | Sections A–B |
4 | Sp | Planar cross-bedded sandstone, fine—to medium-grained sand, sub-rounded and low sphericity, moderate sorting, sub-mature sandstone, set thickness generally 0.5–1 m, white, gray to yellowish brown, lenticular to tabular geometry, with erosional base and comonly grading to facies (Sh) | Litharenite (chertarenite, phyllarenite, sedarenite) | Migration of 2D dunes in response to unidirectional currents on fluvial bedforms, mostly close to river banks (Harms et al. 1975); also deposition in shoreface of a shallow marine siliciclastic shelf | Section A (Fig. 8d) |
5 | Sr | Current and sometimes wave-rippled, cross-laminated sandstone, very fine—to medium-grained sand, well-rounded with high sphericity, well sorted grains, mature to super-mature sandstone, thin sheets-like geometry, set thickness generally 0.1–0.3 m, associated with Sh and Fl | Sublitharenite to chertarenite | Deposition under subaqueous traction conditions by low flow regime (Harms et al. 1975); current ripple in fluvial flood plains and wavy ripple in upper shoreface | Sections A–C (Fig. 7c, d) |
6 | Sh | Horizontally laminated sandstone, fine—to coarse grained sand, sheet or tabular, well-rounded and high sphericity, well sorted graing, mature sandstone, set thickness generally 1–5 m, lower contact is gradational with facies St and its upper contact is with facies Sr, Fl and Fm | Litharenite (chertarenite, phyllarenite, sedarenite) | Deposited under the condition of either upper or lower flow regime by unidirectional currents (Miall 2006); on shallow marine siliciclastic shelf | |
7 | Shc | Hummocky cross-bedded sandstone, fine—to medium-grained sand, well-rounded with high sphericity, well sorted grains, mature to super-mature sandstone, set thickness 0.1–0.3 m, associated with Sl | Litharenite (chertarenite, phyllarenite, sedarenite) | Oscillatory and/or combined flow deposits produced by storm on shallow marine siliciclastic shelf (e.g. Myrow and Southard 1996) | Section C (Fig. 9d) |
8 | Sl | Low-angle (<10°) cross-bedded sandstone, fine—to medium-grained sand, well-rounded with high sphericity, well sorted grains, mature to super-mature sandstone, large wedge-shaped sets; set thickness 0.2–1 m, associated with Shc and Sr | Litharenite (chertarenite, phyllarenite, sedarenite) | Accretionary migration of 2D and 3D dunes in response to unidirectional currents in lower to upper flow regime transition (Cant and Walker 1976); oscillation of wave on shallow marine siliciclastic shelf | Section C (Fig. 9b) |
9 | Fl | Horizontally laminated claystone and siltstone, light green to gray with little organic matter, clay and silt size, plant fossil debris, sheet-like bodies, set thickness generally 10–20 m, gradational contact with facies Sh or Sr in lower part and with facies Fm in upper part | Siltstone; claystone | Deposition from suspension across low relief, abandoned flood plains and/or deposition in distal part of prodelta (e.g. Wright 1985) | |
10 | Fm | Massive claystone to siltstone, clay size, gray to green colours with little organic matter, set thickness generally 5–25 m, lower contact is typically gradational, whereas the upper contact is usually sharply truncated | Siltstone; claystone | Suspension deposition with little or no current activity in overbank settings or abandoned channel in fluvial and delta plains (Miall 1985) | Section B (Fig. 8a) |
11 | Fc | Weakly horizontally laminated carbonaceous claystone to siltstone, clay size, black to dark gray colour with high organic content, wood and plant debris, set thickness generally 5–10 m, associated with Fl, C and Sr/Fl | Siltstone; claystone | Deposition from suspension in vegetated coastal swamp or flood plain | Sections A − B (Fig. 8b) |
12 | Sr/Fl | Interbedded rippled sandstones and mudstones, with wavy bedding and planar laminations, plant debris, set thickness generally 5–10 cm, associated with Fm and C | Sublitharenite–siltstone | Alternating strong and weak flows in coastal plain and inner shelf setting | Sections A, C (Fig. 9a) |
13 | C | Carbonaceous claystone grading to coal, clay and silt size, plant debris, set thickness generally 0.3–0.9 m, lower contact of this facies is ussally gradational with Fm and upper contact is erosional with facies St | Coal | Deposited most likely in vegetated depressions on coastal swamp or flood plain under clastic-sediment starvation condition (e.g. McCabe 1987) | Sections A–B (Fig. 8b) |