Provenance versus weathering control on the composition of tropical river mud (southern Africa)

The nature of moisture at Gobabeb, in the central Namib Desert

1. Introduction 2. Rock weathering and desert surfaces 3. Aeolian geomorphology 4. Dunes 5. Rivers and slopes 6. Applied geomorphology in deserts: hazards, resources and the future 7. Regional variety.

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Arid and Semi-Arid Geomorphology

A classification scheme for fluvial–aeolian system interaction in desert-margin settings

The existence of a mid-Cretaceous erg system along the western Tethyan margin (Iberian Basin, Spain) was recently demonstrated based on the occurrence of wind-blown desert sands in coeval shallow marine deposits. Here, the first direct evidence of this mid-Cretaceous erg in Europe is presented and the palaeoclimate and palaeoceanographic implications are discussed. The aeolian sand sea extended over an area of 4600 km2. Compound crescentic dunes, linear draa and complex aeolian dunes, sand sheets, wet, dry and evaporitic interdunes, sabkha deposits and coeval extradune lagoonal deposits form the main architectural elements of this desert system that was located in a sub-tropical arid belt along the western Tethyan margin. Sub-critically climbing translatent strata, grain flow and grain fall deposits, pin-stripe lamination, lee side dune wind ripples, soft-sediment deformations, vertebrate tracks, biogenic traces, tubes and wood fragments are some of the small-scale structures and components observed in the aeolian dune sandstones. At the boundary between the aeolian sand sea and the marine realm, intertonguing of aeolian deposits and marine facies occurs. Massive sandstone units were laid down by mass flow events that reworked aeolian dune sands during flooding events. The cyclic occurrence of soft sediment deformation is ascribed to intermittent (marine) flooding of aeolian dunes and associated rise in the water table. The aeolian erg system developed in an active extensional tectonic setting that favoured its preservation. Because of the close proximity of the marine realm, the water table was high and contributed to the preservation of the aeolian facies.



A sand-drift surface marks the onset of aeolian dune construction and accumulation, whereby aeolian deposits cover an earlier succession of coastal coal deposits formed in a more humid period. A prominent aeolian super-surface forms an angular unconformity that divides the aeolian succession into two erg sequences. This super-surface formed in response to a major tectonic reactivation in the basin, and also marks the change in style of aeolian sedimentation from compound climbing crescentic dunes to aeolian draas.



The location of the mid-Cretaceous palaeoerg fits well to both the global distribution of other known Cretaceous erg systems and with current palaeoclimate data that suggest a global cooling period and a sea-level lowstand during early mid-Cretaceous times. The occurrence of a sub-tropical coastal erg in the mid-Cretaceous of Spain correlates with the exposure of carbonate platforms on the Arabian platform during much of the Late Aptian to Middle Albian, and is related to this eustatic sea-level lowstand.

Aeolian sand sea development along the mid‐Cretaceous western Tethyan margin (Spain): erg sedimentology and palaeoclimate implications

Mass and hyperconcentrated flow deposits record dune damming and catastrophic breakthrough of ephemeral rivers, Skeleton Coast Erg, Namibia

Contrasting styles of ephemeral river systems and their interaction with dunes of the Skeleton Coast erg (Namibia)

Morphology and Fluvio‐Aeolian Interaction of the Tropical Latitude, Ephemeral Braided‐River Dominated Koigab Fan, North‐West Namibia

ABSTRACT A high-resolution record of fluvial, aeolian and lacustrine deposits of Late Pleistocene age is exposed along the Neales Cliff in the lower reaches of the Nappamurra-Neales River, western Kati Thanda-Lake Eyre (KT-LE). Five major stratigraphic units reflect a variety of changes in sedimentary processes, depositional environments and hence palaeo-lake level fluctuations. This detailed record of a dryland terrestrial sedimentary succession in the northern part of KT-LE enables comparison to contemporaneous sequences in the southern part of KT-LE. The sedimentary record from the Neales Cliff area is placed into a continental stratigraphic framework, in which changes in sediment accumulation and depositional style are linked to climatically driven palaeo-lake level fluctuations independent of eustatic sea-level changes. Following the ~200 ka interglacial maximum, a drying-up systems tract is represented by a fluvial fining-upward trend, capped by palaeosols. A wettening-up systems tract followed, when lake level rose to +10 m AHD during the last interglacial, resulting in a lacustrine succession but punctuated by regular desiccation events. During the following drying-up systems tract, progressive lake-level fall resulted in deep incision around 100 ka, followed by enhanced fluvial deposition of fine-grained sediments. A brief rise in base level resulted in a wettening-up systems tract comprising a thin veneer of fluvial/alluvial sediments followed by extensive dune build-up and desert pavement development during the Last Glacial Maximum. Subsequent lake level fall to the present lake level of −15 m AHD, resulted in deep incision of up to 10 m by the modern day Nappamurra-Neales River.

The interplay of fluvial, lacustrine and aeolian deposition and erosion along the Neales Cliffs and its relevance to the evolution of Kati Thanda-Lake Eyre, central Australia, during the Quaternary

The ephemeral braided river dominated Koigab fan, Skeleton Coast, Namibia

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