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Table 1
Sedimentary facies of the Eocene − lowermost Oligocene (?) siliciclastics and their interpretation. Reference for the interpretations: 1: Renaut and Gierlowski-Kordesch (2010); 2: Leeder (2016); 3: Bhattacharya (2010); 4: Miall (2010).
| Facies | Grain size | Bed thickness | Description | Pedogenic features | Interpretation | |
|---|---|---|---|---|---|---|
| Gyp | clay to medium sand | 5 cm to 80 m | Beds of cm-thick continuous laminations of grain-supported, sand-sized gypsum clasts or lenticular crystals. They sometimes alternate with thin (<5 cm) beds of finely laminated green clay. Two other types of thin beds are rarely observed, interfingered within gypsum laminations: (1) <1mm-thick laminations of micritic carbonate with algal filament casts; (2) massive, fine-grained (clayey to silty) beds of micritic carbonate. The beds often display soft-deformation features (undulated bedding). Vertical burrows cross-cutting the different beds are sometimes observed, as well as fossil mammal footprints. | none | Cumulate evaporites on a low-energy, marl dominated ramp1 | |
| Gym | clay to medium sand | 5 cm to 1 m | Beds of grain-supported gypsum clasts and crystals with a green clayey matrix (or more rarely: a carbonated silty matrix). Matrix content varies but gypsum remains dominant. Limestone intraclasts are sometimes present. Gypsum clasts are commonly sand-sized (sub-)angular grains, but bigger, euhedral prismatic or lenticular gypsum crystals are also present (see Supplementary Fig. S1c). Structure is commonly massive, rarely laminated (and deformed). They sometimes include smaller, discontinuous beds of green clays that are deformed by soft-sediment deformation. | none | Cumulate evaporites on a high-energy, marl-dominated ramp1 | |
| Fl | clay | 1 to 5 cm | Organic-rich mudstones, with mm-thick planar laminations and rare gastropod and bivalve clasts. Sometimes rich in plant debris. | none | Lacustrine laminites1 | |
| Clm | mudstone to wackestone | 1 to 10 cm | Sets of carbonated siltstones to silty carbonates that are either bioturbated and massive or display mm-thick laminations. Limestone intraclasts, bioclasts of gastropods and bivalves (including Limnae) are common, as well as plant debris. Beds are sometimes separated by thin laminations of lignite or organic-rich mud; Layers of <1 mm-thick laminations typical of microbialites are sometimes present. | rare (root traces) | Mixed marls and bioclastic deposits on a high-energy ramp1 | |
| Fmr | Clay to very fine sand | 5 cm to 1 m | Sets of greenish/greyish (more rarely reddish) mudstones to very fine sands with a clayey matrix. Structure: commonly massive, with rare, 1-5 mm-thick laminations. Limestone intraclasts, bioclasts of bivalves and gastropods and/or bioturbation (in the form of sand pockets and vertical burrows, <1 cm in length) are sometimes present. Isolated prismatic gypsum crystals or sandy gypsum in pockets are sometimes present. | rare (fractures, mottles, root traces, and pedogenic nodules) | Mixed siliciclastics on a low energy, marl-dominated ramp1 | |
| L | Clay | 0.2 to 0.5 cm | Lignite with <1 mm-thick laminations in thin, laterally continuous (100+ m) tabular sets. | none | peat deposits1 | |
| Sp | fine to medium sand | 10 to 50 cm thick, in cosets of 1-5 sets | Thick, laterally continuous (100+ m) of yellowish to greenish well-sorted sandstones, sometimes glauconitic. Structure consists in low-angle, 10-50 cm thick sets of massive or cm-thick planar laminations, with rarer sets of trough cross-laminations. Lenses of coarser material (coarse sand mixed with gravels or isolated boulders) occasionally occur. | Occasional presence of mottles, root traces & rhizoliths | Delta mouth bar sands2 | |
| St | Very fine sand to coarse sand | 20 to 90 cm thick, organized in cosets of 1-5 sets | Thick, laterally continuous (100+ m) of yellowish to greenish sandstones, sometimes glauconitic. Sands are less sorted than in facies Sp. The base of the sets is sharp, often erosive, with coarser material and/or mudclasts. Structure is either massive or consists in small-scale trough cross laminations, with a coarser base. Gravels and isolated boulders occasionally occur. | Occasional presence of mottles, root traces & rhizoliths | Sand bars in delta distributary channels and mouth bar back2 | |
| Smp | Clay to very fine sand | Sets from 5 cm to 1 m | Dark brown to reddish grey mudstones to sandstones with clayey matrix and abundant pedogenic traces. Sets can be laterally continuous (100+ m) but sometimes thin out and disappear. Base of the sets commonly grades into underlying sandstones. Sedimentary structures come into two types: massive structure (most common), or with 1-5 mm-thick laminations and small (< 3 cm) cross-laminations that are bioturbated and discontinuous. | Common: mottles, root traces, slickensides, pedogenic nodules | channel levees2 | |
| Fmp | Clay to silt | 5 cm to 1 m | Laterally continuous (100+ m) sets of brownish to reddish mudstones with abundant pedogenic traces. Structure is commonly massive, with rare, discontinuous 1-5 mm-thick laminations. | common: mottles, root traces, slickensides, pedogenic nodules | Overbank sheet flows in floodplain / delta plain environment2 | |
| Spl | fine to medium sand | 20 cm to 1 m | Well sorted, (cross-)laminated sands (3-10 mm thick) with rarer, slightly wavy layers of reddish mudstones (1-10 mm thick). Structure includes planar laminations, small troughs of wave-ripple and trough cross laminations, as well as rarer troughs of Urgonian limestone gravels. | Occasional presence of mottles and root traces | Sandy deltaic shoreface3 | |
| Spi | fine to coarse sand | 50 cm to 2 m | Well-sorted sands organized in slightly inclined, discontinuous planar laminations (3-10 mm thick). Rare troughs filled with gravels and pebbles of Urgonian limestone clasts. | Occasional presence of mottles and root traces | Wave swash deposits in a beach / backshore environment3 | |
| Gt | Gravel to Conglomerate | 50-70 cm thick, organised in cosets of 1-5 sets | Moderately sorted, clast-supported conglomerates with sandy matrix. Structure includes sets of trough cross-bedding and low angle planar stratifications, organized in fining upward cosets. The Base of each coset is sharp and erosional. Clasts are dominated by Urgonian limestones, with subordinate weathered chert, sandstone, and iron crust. | Occasional presence of mottles and root traces | Gravel bars4 | |
| Gmm | Conglomerate | 1 to 2 m | Massive, matrix-supported conglomerates. Poorly sorted. Matrix is made of pink to red mudstones, sands, and Microcodium. bigger clasts are dominated by Urgonian limestone debris, with rare blocks of weathered chert. | Root traces, mottles, carbonate nodules and rhizoliths | Debris flow deposits4 | |
| Gmc | Conglomerate | 50 cm to 5 m | Massive, clast-supported conglomerates. Faint normal grading. Clast content is similar to those of facies Gmm, though clasts are commonly bigger. The muddy to sandy matrix has a high carbonate content. | Root traces, mottles, carbonate nodules and rhizoliths | Sheet flood deposits4 |
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