Preserving the palaeoenvironmental record in Drylands: Bioturbation and its significance for luminescence-derived chronologies

Luminescence (OSL) dating has revolutionised the understanding of Late Pleistocene dryland activity. However, one of the key assumptions for this sort of palaeoenvironmental work is that sedimentary sequences have been preserved intact, enabling their use as proxy indicators of past changes. This relies on stabilisation or burial soon after deposition and a mechanism to prevent any subsequent re-mobilisation. As well as a dating technique OSL, especially at the single grain level, can be used to gain an insight into post-depositional processes that may distort or invalidate the palaeoenvironmental record of geological sediment sequences. This paper explores the possible impact of bioturbation (the movement of sediment by flora and fauna) on luminescence derived chronologies from Quaternary sedimentary deposits in Texas and Florida (USA) which have both independent radiocarbon chronologies and archaeological evidence. These sites clearly illustrate the ability of bioturbation to rejuvenate ancient weathered sandy bedrock and/or to alter depositional stratigraphies through the processes of exhumation and sub-surface mixing of sediment. The use of multiple OSL replicate measurements is advocated as a strategy for checking for bioturbated sediment. Where significant OSL heterogeneity is found, caution should be taken with the derived OSL ages and further measurements at the single grain level are recommended. Observations from the linear dunes of the Kalahari show them to have no bedding structure and to have OSL heterogeneity similar to that shown from the bioturbated Texan and Florida sites. The Kalahari linear dunes could have therefore undergone hitherto undetected post-depositional sediment disturbance which would have implications for the established OSL chronology for the region

Air Cherenkov Methods in Cosmic Rays: A Review and Some History

The history of application of the Cherenkov light emission in the atmosphere to cosmic ray and gamma-ray astronomy studies is briefly outlined with an emphasis on the pioneering activity of A.E. Chudakov. The present-day situation and some new ideas are also discussed.Comment: 11 pages, 5 figures, invited talk presented at the conference P.A. Cherenkov and Modern Physics (Moscow, June 22-25, 2004) commemorating P.A. Cherenkov centenary. Submitted for publication to Journal of Radiation Physics and Chemistr

Single-grain and multi-grain OSL dating of river terrace sediments in the Tabernas Basin, SE Spain

River terraces represent important records of landscape response to e.g. base-level change and tectonic movement. Both these driving forces are important in the southern Iberian Peninsula. In this study, Optically Stimulated Luminescence (OSL) dating was used to date two principal river terraces in the Tabernas Basin, SE Spain. A total of 23 samples was collected from the fluvial terraces for dating using quartz OSL. Sixteen of the samples could not be dated because of low saturation levels (e.g. typical 2xD0 < 50 Gy). The remaining seven samples (5 fossil and 2 modern analogues) were investigated using both multi-grain and single-grain analysis. Single grain results show that: (i) measurements from multi-grain aliquots overestimate ages by up to ∼ 4 ka for modern analogues and young samples (<5 ka), presumably because (ii) the presence of many saturated grains has biased the multi-grain results to older ages. Despite the unfavourable luminescence characteristics we are able to present the first numerical ages for two terrace aggradation stages in the Tabernas Basin, one at ∼16 ka and the other within the last 2 ka

PT-symmetric Solutions of Schrodinger Equation with position-dependent mass via Point Canonical Transformation

PT-symmetric solutions of Schrodinger equation are obtained for the Scarf and generalized harmonic oscillator potentials with the position-dependent mass. A general point canonical transformation is applied by using a free parameter. Three different forms of mass distributions are used. A set of the energy eigenvalues of the bound states and corresponding wave functions for target potentials are obtained as a function of the free parameter.Comment: 13 page

Coral Sea Marine Park Coral Reef Health Survey 2022

The Coral Sea is a critically important and significant ecosystem, which (like coral reefs globally) is increasingly threatened by changing environmental conditions, particularly ocean warming. Previous surveys conducted in 2020 and 2021 showed shallow reef habitats across the Coral Sea Marine Park (CSMP) experienced severe and widespread bleaching in early 2020, with almost two-thirds of all corals surveyed across the CSMP being bleached, and leading to a substantial (39%) decline in coral cover across the CSMP in 2021. James Cook University was commissioned by Parks Australia to assess: (i) the latest condition of benthic, fish and invertebrate communities, (ii) any ongoing impacts of the 2020 bleaching event on benthic, fish and invertebrate communities, and (iii) gain some understanding of the potential resilience and recovery of corals following the 2020 bleaching event. The project undertook detailed surveys of coral, fish and macro-invertebrate communities and associated reef health at fifteen CSMP reefs over two voyages in November 2021, and February-March 2022. Surveys were conducted to provide rigorous quantitative information on temporal (i.e., 2020, 2021, and 2022) and spatial (i.e., among reefs and regions) patterns in (i) cover and composition of corals and macroalgae; (ii) regional patterns of biodiversity; (iii) coral health, injury, and recruitment; and (iv) abundance and composition of reef fishes, sea snakes, and ecologically or economically important invertebrates