Palaeoenvironments in the central White Peak District (Derbyshire, UK): evidence from Water Icicle Close Cavern

Both the distribution of mapped glacial landforms and ice sheet modelling point to an absence of ice over the White Peak during the last glacial period, but intermittent permafrost conditions are expected. Water Icicle Close Cavern is an ancient cave system in the central White Peak that is thought to have been drained for several hundred thousand years and in which the main level of development is around 100m above the present base level of drainage. In 2009 a newly entered section of passage in the cave was found to contain extensive broken speleothem, together with sediments that included possible solifluction deposits and lag gravels. Ice that formed in the cave is considered to be the most likely cause of speleothem breakage and must have completely filled cave passages for shearing of stalactites to have occurred. Melting of ice is thought to have resulted in the removal of some fine sediment, leaving the lag gravel. Uranium-series dating demonstrates a record of speleothem growth in the 96-49ka interval interrupted by a speleothem breakage event between 87 and 83ka. This is interpreted as being related to in-cave ice growth that was associated with wet periglacial conditions. Oxygen and carbon isotope data show a rising trend consistent with cooling and drying before the breakage event, with breakage following a dense, slowly growing lamina. Post-breakage the δ18O values were-3 to-4 per mil and the δ13C values were-8 to-10 per mil , which compare with cool-climate speleothem data in Yorkshire. Textures suggest that the speleothem grew intermittently during this time of cool hemispheric conditions from MIS (Marine Isotope Stage) 4 to the beginning of MIS 3.