British travertines: a review

Abstract

A review of British Quaternary travertines is provided, including details of 159 sites presented as a cross-referenced coded list with a full bibliography. Almost all of these travertines were formed by the degassing of calcium bicarbonate waters. The ‘carrier’ CO2 originated from the soil and epigean atmospheres. At most sites, the travertine is composed of calcite as micrite or microspar, but aragonite occurs in the thermal waters of Bath Spa. The chemical composition of 20 samples gave an average CaCO3 content of 94.2% for active sites and 91.6% for inactive sites. Levels of Fe, Mg, Mn, P and Sr are also reported. Stable carbon and oxygen isotope compositions gave values consistent with the degassing of limestone waters in contact with a soil atmosphere. Some evidence indicated that photo-synthetic activity could also influence travertine deposition. Bryophytes and algae in particular, can influence travertine fabrics through the trapping and binding of calcite. The median δ13CPDB was −11.5‰. The British travertines have been classified into seven fairly broad categories: (1) paludal deposits; (2) cascades; (3) barrages; (4) stream/spring crusts; (5) lake crusts; (6) cemented rudites; and (7) clastic deposits. Spring/stream crusts and paludal deposits are the most common types of active and inactive travertines, respectively. Further statistics on deposit size, relation to solid geology and age are presented. Most sites are Holocene in age but the available dates do not point to a specific period of high travertine deposition, even though the Atlantic period (6000–7000 bp) is considered to represent such a time. Only a handful of travertines are known from the Pleistocene.