Unravelling evidence for global climate change in Mississippian carbonate strata from the Derbyshire and North Wales Platforms, UK

Abstract

The Mississippian Derbyshire and North Wales carbonate platforms were formed in similar tectonic settings within the Pennine and East Irish Sea Basin, respectively. The Derbyshire Platform was surrounded by sub-basins to the north, west, and south whilst the North Wales Platform, 130 km west, had a simpler land-attached geometry. Comparison of these age-equivalent platforms allows the controls on sedimentation, at an important juncture in Earth history, to be evaluated. Both platforms are dominated by moderate-to-high-energy, laterally discontinuous facies, with weak evidence for facies cyclicity, suggesting multiple controls on deposition. Influx of siliciclastic mud on the North Wales Platform led to perturbations in carbonate accumulation; along with abundant palaeosols and coal beds this implies a more humid climate, or shallower water depths compared to the Derbyshire Platform. On both platforms, exposure surfaces can rarely be correlated over >500 metres except for a regionally correlative palaeokarstic surface at the Asbian-Brigantian boundary. This exposure event appears to coincide with a significant regional facies change. Given the lack of evidence for ordering and cyclicity within the strata, the Asbian-Brigantian boundary may mark a significant event that could reflect onset of a transitional climate, prior to the second glaciation event in the Late Palaeozoic Ice Age.

Mechanisms controlling the localisation of fault‐controlled hydrothermal dolomitisation, Derbyshire Platform, UK

“…Platform top facies are characterised by a thick succession of skeletal wacke-packstones and grainstones with frequent emergent surfaces within the Asbian succession (Bee Low Limestone Formation), overlain by finer grained, chert-rich Brigantian wacke-packstones (Monsal Dale Limestone and Eyam Limestone formations) (Manifold et al, 2020). The boundary between the Asbian and Brigantian is marked by a karstic surface, identifiable across the platform (Manifold et al, 2021). Emergent surfaces are evidenced by the presence of mamillated surfaces (Vanstone, 1998), palaeosols rich in volcanic ash and lava flows proximal to the igneous centres (Walkden, 1972).…”

Revisiting the upper Visean mud mounds from Derbyshire (UK): the role of brachiopods in their growth

“…2b; Aitkenhead and Chisholm 1982). In the late Visean, the area evolved into a flat-topped carbonate platform, characterised by peritidal deposition at estimated water depths of 0-25 m (Bridges 1982;Walkden 1987;Manifold et al 2020), with skeletal grainstone shoals on the margins and sponge-microbial reefs at the break-in-slope to the north and west (Wolfenden 1958;Stevenson and Gaunt 1971;Broadhurst and Simpson 1973;Harwood 2005;Manifold et al 2021): Bee Low Limestone Formation (Fig. 2b; Aitkenhead and Chisholm 1982).…”

“…Reconstruction based upon regional data provided by Smith et al (1967), Gaunt (1971), andAitkenhead et al (1985), integrated with data on the northern platform margin by Gawthorpe and Gutteridge (1990) and Harwood (2005), on the southern margin by Harwood (2005), on the Ashford Basin by Gutteridge (1987Gutteridge ( , 1989a, and on the area around Monyash by Gutteridge (1990Gutteridge ( , 1991Gutteridge ( , 1995 and Nolan et al (2017). Data about the Asbian (upper Visean) margin of the Derbyshire Carbonate Platform from Harwood (2005) and Manifold et al (2021). In the Monyash area, crinoidal grainstone shoals developed in innerramp settings overlie the mud mounds in the uppermost Monsal Dale Limestone Fm (Nolan et al 2017) and in the Eyam Limestone Fm (Gutteridge 1989b;Nolan et al 2017); they never occur underneath the mud mounds.…”