The sand sea that composes a large part of the Namib Desert in South West Africa covers approximately 34,000 km 2 and extends from the Great Escarpment on the east to the Atlantic Ocean on the west, south of the Kuiseb River. This sand sea, or erg, contains most of the principal dune types that have been recognized throughout the world, many of them of great height and separated by broad, flat interdunes. The dominant type and by far the most common form is the linear (seif, longitudinal) dune that extends as a series of long, nearly parallel ridges with north-south orientation across the length of the dune field. Studies of dune structure were made largely by trenching the various dune types to expose sections of cross-strata in selected parts. The trenches showed that those dunes attributed to unidirectional winds—barchan, barchanoid ridge, and transverse—with low-angle foresets on the windward sides and high angles on the lee sides, are mostly located along a narrow belt on the Atlantic Coast. The large interior dunes of linear type showed high-angle dips on both sides of the ridges and are believed to result from alternating two-directional winds. Because the genesis of these dunes has long been controversial, a review is given of the other principal hypotheses—deflation, helical roll, modification of simple dune forms, and outcrop-controlled lee-side accumulation—and evidence is presented for and against each. The most complex of dune types, in which arms radiate from a central point, is referred to as a star dune and is fairly numerous in various parts of the sand sea, especially near the vleis and along the northern dune margin. Such dunes are considered, both on the basis of data from trenching and from records of measured winds, to be the product of wind from three or more directions. Star dunes form along the ridges of linear dunes and also as isolated mounds on the desert floor, and they attain considerable heights. Minor dune types that are described and briefly discussed are those controlled by vegetation and referred to as coppice dunes. Also the small types known as dome dunes and blowouts, both of which were structurally analyzed, are discussed.

Interrelationships among late Holocene climate, the dynamics of coastal dunes and sedimentation in adjacent small lakes along coasts of the upper Great Lakes have been studied for over a decade. Nonetheless, many questions remain as to relationships between climate variability and dune activity. The study site is Oxbow Lake, near Saugatuck, Michigan, which formed as an artificial cutoff of the Kalamazoo River in 1906. Stratigraphic control of the infilled western end of the lake is from ground penetrating radar, and lake sediment from Livingstone and Glew cores with age control from 210 Pb/ 137 Cs/ 7 Be analysis. The climate data used included Lake Michigan water levels and temperature, precipitation, drought and evaporation data from a weather station 30 km to the south and wind data from buoys on Lake Michigan. Episodic peaks of eolian sand in the lake sediment are interpreted to be sourced from adjacent small parabolic dunes along the shoreline and from a foredune west of the lake. Linear regressions of the climate data and weight percent sand resulted in a variety of correlations, some conflicting, and with uncertain meanings. It was found through visual correlation that peaks in sand correspond with both peaks in water levels of Lake Michigan and the winter Palmer drought severity index. The implications of this research are that dune activity is linked to periods of wet conditions and storminess, contrary to typical eolian environments, but consistent with other studies in temperate coastal dunes along the Great Lakes. Results can be used as a modern analogue for coastal dune activity during times of high lake level.

Abstract A database of coastal dune sediments in England and Wales has been developed with potential applications in forensic investigations. Coastal dunes are popular sites for criminal-related activities, including burial of drugs, weapons and murder victims. The coastal dunes and associated areas of windblown sand in England and Wales occupy an area of approximately 200 km 2 within 112 individual identified systems. Research has been undertaken to ascertain the spatial variation in sedimentological properties of the coastal dune sediments in England and Wales. Field sediment sampling has been undertaken at each dune system. More than 1500 sediment samples have been analysed by laser diffraction to determine particle size characteristics, and more than 500 have been analysed by inductively coupled plasma atomic emission spectrometry (ICP-AES) to determine chemical composition. Two examples illustrate how the database has been used in criminal investigation.

Abstract The Maputaland area of northeastern South Africa is characterized by extensive dunefields which developed during polyphase reworking of regional aeolian cover sand from the Mid-Pleistocene to the Holocene. Extended parabolic dunes, many preserved only as wind-rift trailing limbs, as well as areas of sinuous crested dunes, hummocky dune systems and the high, composite, accretionary coastal barrier dune cordon are the dominant dune forms. There are few natural sections exposing the stratigraphic succession and unequivocal relative age relationships between dune systems are uncommon. A ground penetrating radar (GPR) survey of dunes and representative aeolian sand stratigraphic units was undertaken in order to investigate the internal structure of the different dune forms and identify stratigraphic relationships between buried sedimentary units. The GPR profiles revealed that the trailing limbs of almost all the parabolic dunes that were surveyed comprise stacked sand units, separated by low-angle reflections interpreted as bounding surfaces, which accumulated through polyphase vertical accretion. Most extended parabolic dunes are aligned north-south and the upper parts of the dunes are characterized by inclined reflections in GPR profile interpreted as large-scale sets of cross-stratification with apparent dips toward the west. A hummocky dune revealed cross-stratified aeolian sand superimposed on a truncated dune form and probably formed through deflation of pre-existing dunes. Using 100 MHz and 200 MHz antennae, it is clear that GPR is capable of imaging very fine sedimentary structures and buried erosional surfaces in the homogeneous aeolian sand of Maputaland. At some of the sites investigated, the buried sand units identified were sampled by hand-augering for infrared-stimulated luminescence dating. The age determinations on these samples suggest that vertical accretion of up to 7 m of sand occurred intermittently over variable time scales up to 25 000 years on some parabolic dune limbs during the Late Pleistocene. In some complex dunefields, adjacent dunes were mobilized at different times, suggesting that remobilization was localized. The implications of the complex internal structure and vertical accretion of extended parabolic dunes are discussed in the context of changes in vegetation cover and water table due to seasonal and short-term cyclical climate variations as well as long-term climate change patterns during the last glacial cycle and the Holocene.