Holocene evolution of the Anichab Pan on the south‐west coast of Namibia

Abstract

Coastal sediment-filled depressions (pans) are one of the few areas that contain Quaternary records of sea-level and palaeoenvironmental change along the western margin of southern Africa. Anichab is a 128 km 2 salt-encrusted pan on the hyper-arid southern coast of Namibia with an emergent, well-preserved and in-place mid-Holocene mollusc assemblage. The molluscs are typical of subtidal sands on the sheltered side of offshore islands but include several warm-water species no longer found living along this coast. The Holocene evolution of the pan was largely influenced by changes in sea level and supply of sand along the coast. Calibrated radiocarbon ages of mollusc shells indicate a maximum Holocene sea level of ca 2 m above mean sea level (msl) from 7AE0 to 6AE3 ka and a return to near present-day sea level by 5AE3 ka. The pan surface is 2 m below msl and has been emergent since 4AE9 ka from the build up of sandy beaches and coastal dunes. A thin (1-4 cm) halite crust occurs over much of the pan surface but a layer of halite-cemented sand up to 40 cm thick is restricted to the central pan. Gypsum occurs near the subsurface brine interface and is limited by calcium to the edges of the pan. Nodules of calcite-cemented sand are forming in brackish, relatively high alkalinity subsurface waters in the southeast corner of the pan and nodules of aragonite-cemented sand are forming in brines 1 m below the central pan surface. Although modern dolomite has been reported from coastal lagoons of Brazil and Australia, carbonate cements are a minor feature of Anichab Pan and dolomite was restricted to a single reworked nodule most likely of Late Pleistocene age. Therefore, Anichab Pan does not appear to be a modern analogue to extensive, mixed-water dolomite cements found in Upper Pleistocene sediment-filled depressions on the Namibian shelf.

Holocene sea level and environmental change on the west coast of South Africa: evidence from plant biomarkers, stable isotopes and pollen

“…7; 474 Miller et al 1995; Compton 2001Compton , 2006Compton , 2007. Although the thiophene data cannot serve as sea-475 level index points, they demonstrate generally good correspondence with the geomorphic evidence 476 from which Compton (2001) inferred an early to middle Holocene high stand ca.…”

Wind Erosion in Drylands

“…Climate change influences the supply of abrasive sediment, wind strength and direction, and the infilling of yardang systems by sand and lacustrine deposits. In Namibia, subtle changes in Holocene sea level affect the supply of beach sand that is driven inland to feed an aeolian corridor (Corbett, 1993;Compton, 2006Compton, , 2007. In deflation basins associated with lakebeds, cycles of erosion and sedimentation alternately lower and fill basins (Washington et al, 2006).…”

“…In southern Africa, they are prominent features in coastal Namibia (Corbett, 1993;Compton, 2007;Goudie, 2007). As early as 1887, Stapff described yardangs formed from bedrock in the Kuiseb Valley as 'aerodynamic landforms'.…”

Mineralogical assemblages, geochemistry and fossil associations of Pleistocene–Holocene complex siliciclastic deposits from the Southwestern Doñana National Park (SW Spain): A palaeoenvironmental approach

“…In addition, several groups of microfossils (diatoms, foraminifers, ostracodes, calcareous nannoplankton, and pollen) have been used as tracers of the main palaeoenvironmental features (Cearreta et al, 2003;Fontana, 2005;Zong et al, 2006;Bao et al, 2007). The final interpretations can be improved if additional macrofossil groups are studied and the (palaeo-)autoecology of their main assemblages is taken into account (Hayward et al, 2002;Compton, 2007). Sedimentary Geology 225 (2010) 1-18 In this general scenario, it is the frequent presence of distinctive sedimentary layers with characteristic textural and mineralogical features that have been attributed to storms, cyclones, hurricanes or tsunamis (Clague et al, 2000;Singarasubramanian et al, 2006;Tripsanas et al, 2007).…”