Deltaic sedimentation in an unstable tectonic environment – the Lower Limestone Group (Lower Carboniferous) of East Fife, Scotland

Abstract

The Lower Limestone Group, which outcrops extensively on the east coast of Fife, southeast Scotland, consists of interbedded sandstones, siltstones and claystones with occasional coal seams, and limestone beds. Several of the coals have been mined economically in the past.The sequence was deposited in a shallow-water, deltaic setting. Three facies associations have been distinguished; (1) laminated claystones, and marine bioclastic limestones, which were deposited in prodelta and marine shelf environments, (2) crudely coarsening-upward sandstone units, interpreted as delta front deposits of fluvially-dominated though wave-influenced, shallow-water deltas, and (3) interbedded clastic sedimentary rocks and coals, deposited in delta plain environments. The sequence as a whole accumulated by repeated progradation and abandonment of deltaic complexes.Palaeosol profiles of four types are superbly preserved within the delta plain facies association. These are (1) organic soils (peats), now coal seams, (2) gley palaeosols, which formed in persistently waterlogged conditions, (3) freely drained soils which formed on a quartz sand-rich substrate, and (4) similar profiles formed by free drainage through variable substrates and involving B horizon accumulation of concretionary iron oxides. Compound palaeosols are common.Deposition of the Lower Limestone Group was influenced by the tectonic and volcanic instability of the Fife area during Visean times. Frequent seismic events centred on active fault lines caused local uplift of parts of the normally waterlogged delta plain environment, allowing the formation of well-drained soils. Peats (coals) were best developed and least affected by oxidation in an elongate, fault bounded zone of enhanced subsidence.

Onset of the glacioeustatic signal recording late Palaeozoic Gondwanan ice growth: New data from palaeotropical East Fife, Scotland

“…Subsequent studies by Belt (1975Belt ( , 1984 emphasized the cyclical nature of the succession and sought to develop models for the so-called "cyclothems" based on statistical analysis of facies successions. In the modern era, Burn (1990) conducted a stratigraphic and sedimentological analysis of the Strathclyde Group in the study area, while Fielding et al (1988) carried out a sedimentological study of the overlying Lower Limestone Group (now Formation), and Kassi et al (2004) carried out a sequence stratigraphic evaluation of the same succession. The body of research on the succession as a whole was summarized by Read et al (2002).…”

“…3). The account given here represents a modification and condensation of the facies scheme for the Lower Limestone Formation presented by Fielding et al (1988).…”

“…6A, B). One such unit, the St Monans Brecciated Limestone which marks the base of the Lower Limestone Formation, has a floatstone texture (Fielding et al, 1988;Searl and Fallick, 1990), whereas the others are mainly wackestones to locally grainstones. Some beds, notably the St Monans White Limestone near the top of the Pathhead Formation (343-347 m on Fig.…”

“…A tidal influence on sediment dispersal is indicated by the northeast palaeocurrent mode. Pervasive softsediment deformation in some bodies was interpreted as a record of synsedimentary seismic activity by Fielding et al (1988). The presence of trace fossils and the evidence for tidal backflow indicates that distributary channels were located on the lower delta plain of the ancient landscape, within the reach of marine processes.…”

“…6F). Plant roots and detrital plant remains are abundant, as are pedogenic modifications of the original sediment fabric (Fielding et al, 1988).…”