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Paleo-lacustrine sediments indicate that a mega-lake developed in the Hetao Basin (HTB), suggesting dramatic changes in the geomorphology and surface process of the Yellow River and surrounding regions. However, the formation time of the mega Hetao paleo-lake (HTPL) in the HTB remains unclear. In this study, a set of 7.6-m-thick lacustrine sediments in the middle of the HTB is dated by both quartz optically stimulated luminescence (OSL) and K-feldspar (KF) post-infrared infrared stimulated luminescence (p-IR IRSL, pIRIR). The results are as follows. 1) The quartz OSL ages do not increase with depth as the KF pIRIR ages displayed but are saturated at ca. 80–100 ka with the consequence of age underestimation. The influence of signal saturation may occur below 96 Gy (ca. 32 ka) in this region. Thus, the KF pIRIR ages are chosen for geomorphological evolution reconstruction. 2) These ages suggest the level of the HTPL exceeded 1033 m asl twice—at the early stages of MIS 7 (∼255–245 ka) and MIS 5 (∼130–120 ka). However, the exact scale of the HTPL and its relationship with the Jilantai paleo-lake is unclear. 3) This chronology suggests strong linkage between periodic formation of the HTPL and glacial-scale climatic change. We therefore propose an alternative hypothesis to interpret these processes: the Hobq dunefield expanded eastward to dam the narrow Jin-Shaan Gorge during the glacial periods when the flow of the Yellow River was weak. Then, in the beginning of the interglacial periods, the basin was filled by abruptly resumed runoff in response to increased glacial meltwater and precipitation on the northeastern Tibetan Plateau. Once the lake spilt out, the loose dune dam was quickly breached.

Causal links that connect Holocene high stands of Lake Superior with dune building, stream damming and diversion and reservoir impoundment and infilling are inferred from a multidisciplinary investigation of a small watershed along the SE shore of Lake Superior. Radiocarbon ages of wood fragments from in-place stumps and soil O horizons, recovered from the bottom of 300-ha Grand Sable Lake, suggest that the near-shore inland lake was formed during multiple episodes of late Holocene dune damming of ancestral Sable Creek. Forest drownings at ∼3000, 1530, and 300 cal. years BP are highly correlated with local soil burial events that occurred during high stands of Lake Superior. During these and earlier events, Sable Creek was diverted onto eastward-graded late Pleistocene meltwater terraces. Ground penetrating radar (GPR) reveals the early Holocene valley of Sable Creek (now filled) and its constituent sedimentary structures. Near-planar paleosols, identified with GPR, suggest two repeating modes of landscape evolution mediated by levels of Lake Superior. High lake stands drove stream damming, reservoir impoundment, and eolian infilling of impoundments. Falling Lake Superior levels brought decreased sand supply to dune dams and lowered stream base level. These latter factors promoted stream piracy, breaching of dune dams, and aerial exposure and forestation of infilled lakebeds. The bathymetry of Grand Sable Lake suggests that its shoreline configuration and depth varied in response to events of dune damming and subsequent dam breaching. The interrelated late Holocene events apparent in this study area suggest that variations in lake level have imposed complex hydrologic and geomorphic signatures on upper Great Lakes coasts. [Copyright &y& Elsevier]

Channel-shaped deposits of well sorted sand with only 2–4% fine-grained material, being either massive and structureless or upward fining with basal lag, are found interbedded with aeolian sand in the Skeleton Coast Erg, Namibia. Detailed analyses of the channel-shaped deposits suggest that they are formed as hyperconcentrated flows within the erg. Grain-size analysis and whole rock geochemical modeling revealed that some of the fluvial sediments contain up to 70% aeolian sand, interpreted as a result of dune collapse into the fluvial system. In certain cases, this instantaneous supply of sand resulted in generation of sandy mass flows with laminar flow behaviour. The presence of smectite as dominant clay mineral proved to be of crucial importance in formation of mass flow deposits. These mass flows had no erosional capacity, and drape the palaeotopography. They are comparable to those generated by catastrophic collapse of dunes, described in the literature. This paper suggests that all these deposits should be termed intra-erg mass flows, as several of them carry little, if any debris. Based on their origin, intra-erg mass flows can be divided into two groups:(1)Attached intra-erg mass flows, which are formed and found attached to the dune that sourced the flow;(2)Detached intra-erg mass flows, which are not found adjacent to the dune sourcing the flow, and often carry material sourced outside the dune field.A five-stage model is proposed, involving dune damming to explain the observed deposits and the degree of reworking. When the flood basin behind the erg overtops the threshold area, water pours into the erg, giving rise to a complex fluvio-aeolian setting. The setting in the Skeleton Coast erg is comparable to recent as well as ancient settings, and reveals valuable information for reservoir characterization and hazard assessment. [Copyright &y& Elsevier]