Hydrogeological Significance of Secondary Terrestrial Carbonate Deposition in Karst Environments

Abstract

proportion of the dissolved calcium carbonate derived from limestone dissolution. The\rstudy of such secondary deposits is important because they provide information on the\rpalaeohydrogeology of the unsaturated zone at the time of precipitation. They also offer the\rpotential to provide information with respect to climatic conditions through the study of\rstable isotopes and dating through the study of radiogenic isotopes. This chapter introduces\rthe formational processes, depositional environments (hydrogeological, hydrogeochemical,\rbiological and geomorphological) and post depositional history of secondary terrestrial\rcarbonate deposits. Consideration is given to the associated research themes and techniques,\rin particular to the current research focus on the role of microbial communities in present\rday sediment-water interface processes (Pedley and Rogerson, 2010) and the implications\rfor furthering the understanding of climate change and landscape evolution. These deposits\rhave a world-wide distribution (Ford and Pedley, 1996; Viles and Goudie, 1990) and include\rspeleothems, travertines, tufas, calcareous nodules, calcretes and carbonate cements, such\rthat speleothems and tufa represent two end members of a continuum of freshwater\rcarbonate (Pedley and Rogerson, 2010). They form in a range of climatic conditions, but are\rbest developed in warm humid climates. Examples cited in the text include case studies\rfrom the White Peak, Derbyshire UK, which currently experiences a temperate humid\rclimate and hosts a range of deposits as a consequence of its recent geological history. The\rWhite Peak was not subjected to glacial erosion during the most recent (Devensian, MIS 2-4)\rglaciation, therefore there is a potential for an extensive record of Quaternary palaeoclimatic\rconditions to be preserved in the secondary carbonate deposits.