Radiocarbon and Thermoluminescence Studies of the Karst Pipe Systems in Southwest England and South Wales

Abstract

Paleokarst forms in raised beach deposits of Southwest England and South Wales and generally known as "pipes" were dated by 14C and thermoluminescence (TL) methods. Current geological opinion is that these pipes are features that developed under the cover of periglacial-solifluctional deposits due to periglacial conditions prevalent in the Late Devensian. In the present study, TL was used to determine the age of quartz grains forming the raised beaches. 14C ages were obtained from carbonate cements within sandrock and on the pipe walls. TL ages measured for quartz grains separated from sandrock samples are older than 80 ka BP, whereas the corresponding TL dates obtained from the sandy material of pipe infills center around 40 ka BP. All carbonates yielded finite apparent 14C dates that range from ca. 45 ka BP to 27 ka BP for sandrock. The apparent 14C dates obtained on carbonate cements from the pipe walls fall into two groups, one ranging from 30 ka BP to 22 ka BP and the other from 15 ka BP to 7 ka BP. On the basis of geochemical considerations, we conclude that the sandrock cements formed between 35 and 25 ka BP and pipe walls cemented between 30 and 2 ka BP with a break during the climate deterioration caused by last ice sheet advance.