Lower delta plain interdistributary deposits — An example from the Westphalian of the Lancashire Coalfield, northwest England

Abstract

A large quarry at Billinge Beacon in Lancashire, northwest England, has provided an excellent exposure of part of the Lower Westphalian A (Upper Carboniferous) Coal Measures sequence which was deposited in a lower delta plain setting. The main horizon exposed, known as the Dyneley Knoll Flags, is interpreted as the proximal reaches of two crevasse-initiated minor delta complexes, into the lower of which has been incised a sinuous minor distributary channel.The channel, which was approximately 120 m wide, built a 160 m wide channel belt by limited lateral accretion with time; vertical accretion appears to have been the dominant infilling mechanism. This produced a stacked series of epsilon cross-strata, made up of rhythmically interbedded sandstone and silty claystone. The peculiar style of infilling of the channel is ascribed to deep incision of the channel into minor delta deposits, and possibly the influence of a seasonal climate.

Stratigraphic Record of River-Dominated Crevasse Subdeltas With Tidal Influence (Lajas Formation, Argentina)

“…The facies associations and their spatial and relative temporal relationships described herein fit the key attributes of crevasse-subdelta depositional models, similar to the ones proposed by several authors (Elliott 1974;Fielding 1984Fielding , 1987Tye and Coleman 1989). Crevasse subdeltas form in the lower delta plain of major deltas, in the backwater zone, and seaward of the bayline (Posamentier et al 1988;Blum et al 2013).…”

“…Salinity levels were at least brackish in the interdistributary areas, as indicated by Gastrochaenolites borings, Paleophycus, and Thalassinoides (Gérard and Bromley 2008) and by the presence of oysters. Although water depth was shallow, there is no evidence of subaerial exposure, such as paleosols, rooted horizons or coals, as described in other ancient crevasse-subdelta examples (Elliott 1974;Fielding 1987).…”

“…Literature on ancient crevasse-subdelta deposits is almost solely restricted to the Carboniferous of the United Kingdom and Eire (Fielding 1984(Fielding , 1987Pulham 1989) and in modern systems limited to the Mississippi Delta (Coleman and Gagliano 1964;Arndorfer 1973;Tye and Kosters 1986;Tye and Coleman 1989;Roberts 1997). Many terms have been proposed to describe these kinds of systems: interdistributarybay sequences (Elliott 1974;Pulham 1989), crevasse-initiated minor delta systems or complexes (Fielding 1984(Fielding , 1987, crevasse deltas or crevasse delta systems (Fielding 1984(Fielding , 1987Bhattacharya 2006), minor deltas or minor delta systems (Fielding 1984(Fielding , 1987, crevasse subdeltas (Bhattacharya 2006(Bhattacharya , 2010, and subdeltas (Coleman and Gagliano 1964;Roberts 1997).…”

“…Many terms have been proposed to describe these kinds of systems: interdistributarybay sequences (Elliott 1974;Pulham 1989), crevasse-initiated minor delta systems or complexes (Fielding 1984(Fielding , 1987, crevasse deltas or crevasse delta systems (Fielding 1984(Fielding , 1987Bhattacharya 2006), minor deltas or minor delta systems (Fielding 1984(Fielding , 1987, crevasse subdeltas (Bhattacharya 2006(Bhattacharya , 2010, and subdeltas (Coleman and Gagliano 1964;Roberts 1997). Moreover, when these systems flow into fresh-water lakes they are termed lacustrine deltas (Fielding 1984;Tye and Coleman 1989), although not all lacustrine deltas are crevasse-initiated.…”

Late Moscovian terrestrial biotas and palaeoenvironments of Variscan Euramerica

“…Measures are dominated by mudstones with localised sandstone bodies, representing deposits of a lower to upper delta plain environment (Fielding, 1984a(Fielding, , 1984b(Fielding, , 1986(Fielding, , 1987Guion & Fielding, 1988;Guion et al, 1995;Rippon, 1996;Aitkenhead et al, 2002). The main distributary channels were up to 20 m thick and 10 km wide, and carried either micaceous sediment from the north; or greenish grey, weakly micaceous and clay-rich sediment from the west (Chisholm, 1990;Chisholm et al, 1996;Hallsworth and Chisholm, 2000).…”