Depositional environment and OSL chronology of the Homeb silt deposits, Kuiseb River, Namibia

Abstract

Previous studies suggest that the Homeb silts of the Kuiseb valley, Namibia (i) accumulated in a dune-dammed lake, (ii) are end-point deposits, (iii) represent an aggrading river bed, and (iv) are slackwater deposits. Thus, they have been used alternatively as evidence of past drier conditions or past wetter conditions. Lithostratigraphic analysis of two sediment sequences at Homeb indicates sedimentation by aggradation of the Kuiseb River triggered by a transition from an arid to humid climate. OSL ages for the sequences were obtained by the SAR protocol on aliquots of 9.6-mm and 4.0-mm diameter and on single grains. Four-millimeter aliquot minimum ages closely approximate the single-grain minimum ages and are younger than 9.6-mm aliquot minimum and central ages. Based on these results, the small-aliquot (4-mm) approach appears to provide ages comparable to those obtained by the more laborious and time-consuming single-grain method. Minimum ages indicate rapid deposition of the Homeb Silts in at least two episodes centered at ∼15 ka and ∼6 ka during climate transitions from arid to humid. Flash floods eroded the valley fills during slightly more arid conditions.

Morpho‐sedimentary records at the Brahmaputra River exit, NE Himalaya: climate–tectonic interplay during the Late Pleistocene–Holocene

“…Predepositional bleaching history of the sediments was assessed by the two different methods as summarised in Srivastava et al (2006). The first used the relationship between the natural luminescence intensity and the palaeodose of the individual aliquots.…”

50,000 years of vegetation and climate change in the southern Namib Desert, Pella, South Africa

“…Chase and Meadows, 2007;Lancaster, 2002), and as a result very little is known about long-term climate and vegetation dynamics surrounding the hyperarid core of southwestern Africa. The arid environment has precluded the preservation of organic material, and most palaeoenvironmental records have been obtained from a diversity of geomorphic features such as dune sediments (Bateman et al, 2003;Blümel et al, 1998;Bristow et al, 2007;Chase and Thomas, 2006;Chase and Thomas, 2007;Eitel et al, 2002;Stokes et al, 1997;Stone and Thomas, 2008;Telfer, 2007;Thomas et al, 1998;Thomas et al, 1997), fluvial deposits (Blumel et al, 2000;Bourke et al, 2003;Eitel et al, 2002;Eitel and Zöller, 1996;Heine, 2004;Heine and Heine, 2002;Heine and Völkel, 2009;Lancaster, 2002;Srivastava et al, 2006;Stone et al, 2010;Vogel, 1982) and fragmentary lacustrine records (Cooke and Heine, 1979;Deacon and Lancaster, 1988;Heine, 1978Heine, , 1982Lancaster, 1979Lancaster, , 1984Lancaster, 1986;Lancaster and Teller, 1988;Teller and Lancaster, 1985;Teller and Lancaster, 1986;Teller et al, 1990;Ward, 1984). Many of these, while being potentially valuable indicators of landscape dynamics (Thomas, 2013), are of debatable palaeoclimatic significance …”

Morpho-sedimentary records of active tectonics at the Kameng river exit, NE Himalaya

“…To check the regional continuity of the terraces an additional sample LD-96 was collected from terrace T 3 located 5 km upstream of Bhalukpong at Tipi town. The sample preparation was done following widely accepted protocols (for details see Srivastava et al, 2006). OSL was recorded for 100 s at 125°C temperature through filter combination of BG-39 + U-340 on a Riso TL/OSL-12 system with a halogen lamp source for stimulation.…”

“…The extent of bleaching of the sediments was assessed by the method outlined by Srivastava et al (2006). The method utilizes the relationship between the natural luminescence intensity and the paleodose of individual aliquots.…”