Karst Environment

Occurrences of surficial karstic depressions in south-central Georgia are generally attributed to the dissolution within the Floridan aquifer even though it is overlain by a confining unit of varying thickness. This study explores the karst development within the carbonate layers of the confining unit using geophysical investigation techniques, namely electrical resistivity tomography (ERT), and ground penetrating radar (GPR). Surveys at sites of observed surficial depressions reveal shallow karst development which is unrelated to the deeper karst processes within the Floridan aquifer. The overlying unit, generally comprised of impermeable siliciclastic sediments, appears to have lower degrees of confinement at sites of increased karst development where carbonate layers are present. This has important implications not only for structural stability of the area, but also for the environmental sensitivity of the Floridan aquifer.

Numerous palaeoenvironmental and archaeological studies from southern Arabia (Yemen and Oman) have revealed strong relations between phases of human settlements and climate change linked to the Indian monsoon system. Analyses on speleothems, cave fills, lacustrine deposits and palaeo-mangroves have shown that during the Early to Mid-Holocene, a humid Optimum culminated around 9000-8000 cal BP. New results on inland speleothems and cave sediments fromthe Jebel Qara (southern Oman) are crucial in our depiction of Early and Mid-Holocene climatic evolution and cultural dynamics of the region. These aspects are discussed here, based on new archaeological surveys, excavations, geoarchaeological and micromorphological studies, aiming to better understand connections with Terminal Pleistocene and Early Holocene autochthonous cultures of southern Arabia. Our results suggest that the final Pleistocene was marked by strong aridity, which promoted a widespread thermoclastism within rock shelter and deposition of aeolian sand; in contrast, the transition towards the Holocene is marked (since c.12,000 cal BP) by a progressive increasing in environmental humidity, which permitted the formation of thick strata of peridesert loess. After this phase, the environmental humidity of the Jebel increased and permitted the existence of a large community of land snails; the latter were exploited by Early Holocene hunter-gatherers who lived in the rock shelters between c. 10,500e9500 cal BP and left consistent accumulations of land shells (escargotières). The maximum of Holocene humidity was reached between 9000 and 8000 cal BP; regional aquifer were recharged and the deposition of calcareous tufa at the entrance of caves started, lasting up to c. 4500 cal BP. C and O stable isotopes from calcareous tufa highlights, in accordance with several regional records, the progressive decline of the intensity of the Indian Ocean monsoon and the transition towards arid conditions. In this phase, the area was abandoned and archaeological communities possibly relocated along the coast of central and southern Oman, where they exploited the mangrove environment.