Palaegeography of Tropical, Seasonal, Coastal Wetlands

Dave Millward (BGS), Sarah Davies (Leicester), Peter Brand (BGS), Mike Browne (BGS), Carys Bennett (Leicester),
Tim Kearsey (BGS), Janet Sherwin (Leicester), John Marshall (Southampton)

I don't have the sedimentologial knowledge to write a layman's summary of this paper, so this is just the abstract, copied from the paper. In the New Year, Dave Millward (BGS) will do that for me. This is just a placeholder for now.

The Lower Carboniferous Ballagan Formation of northern Britain is one of only two successions worldwide to yield the earliest known tetrapods with terrestrial capability following the end-Devonian mass extinction event. Studies of the sedimentary environments and habitats in which these beasts lived have been an integral part of a major research project into how, why and under what circumstances this profound step in the evolution of life on Earth occurred.

Here, a new palaeogeographic map is constructed from outcrop data integrated with new and archived borehole material. The map shows the extent of a very low-relief coastal wetland developed along the tropical southern continental margin. Coastal floodplains in the Midland Valley and Tweed basins were separated from the marginal marine seaway of the Northumberland–Solway Basin to the south by an archipelago of more elevated areas.

A complex mosaic of sedimentary environments was juxtaposed, and included fresh and brackish to saline and hypersaline lakes, a diverse suite of floodplain palaeosols and a persistent river system in the east of the region. The strongly seasonal climate led to the formation of evaporite deposits alternating with flooding events, both meteoric and marine.

Storm surges drove marine floods from the southwest into both the western Midland Valley and Northumberland–Solway Basin; marine water also flooded into the Tweed Basin and Tayside in the east.

The Ballagan Formation is a rare example in the geological record of a tropical, seasonal coastal wetland that contains abundant, small-scale evaporite deposits. The diverse sedimentary environments and palaeosol types indicate a network of different terrestrial and aquatic habitats in which the tetrapods lived.

Palaeogeographic map of the Ballagan Formation

Palaeogeographic map of the Ballagan Formation
© Copyright 2018 BGS and authors.