The Pleistocene terrestrial carbonate mantle on the southeastern margin of the St Vincent Basin, South Australia

Nature of sedimentary deposits in the western Makgadikgadi basin, Botswana

“…Both micro-organisms and plant material have been described as being conducive for CaCO precipitation (e.g. Phillips et al, 1987;Beier, 1987;Phillips & Milnes, 1988;Platt, 1989;Ringrose, 1996). However, the physical or biophysical origin of many calcareous deposits remains speculative because of the numerous inter-related biogeochemical parameters involved in calcium carbonate precipitation (e.g.…”

Multi-stage Holocene evolution of the River Murray Estuary, South Australia

“…The indurated calcrete nodules observed within Unit 6 are characteristic of carbonate sediments that have experienced pedogenic alteration. This involves the in situ dissolution of surficial carbonates, followed by the illuviation of dissolved carbonate down the profile, and re-precipitation as calcite at deeper, chemically favourable sites (Phillips and Milnes, 1988; Warren, 1983). This typically results in soil profiles being capped by an indurated calcrete horizon, with a graded mixture of calcrete nodules and calcareous fines that decreases in nodule abundance and increases in dolomite (CaMg(CO 3 ) 2 ) concentration with depth (Hutton and Dixon, 1981).…”

“…This typically results in soil profiles being capped by an indurated calcrete horizon, with a graded mixture of calcrete nodules and calcareous fines that decreases in nodule abundance and increases in dolomite (CaMg(CO 3 ) 2 ) concentration with depth (Hutton and Dixon, 1981). Pedogenically altered carbonate profiles are observed to extensively mantle the calcarenite dunes of the Bridgewater formation surrounding the Lower Lakes, showing cyclic periods of superimposed pedogenesis corresponding to past glacial–interglacial transitions (Murray-Wallace, 2018; Phillips and Milnes, 1988). The absence of the calcrete capstone overlying Unit 6 indicates that either substantial erosion of this unit has occurred, or that this is a reworked deposit of material from nearby calcareous palaeosols.…”