The origin and history of sand bodies in the Pilliga State Forest, NSW

1.2 AIMS: The investigation of sand monkeys and other sand bodies in the Pilliga forms the basis for this study. This study in turn, forms a link in the overall investigation of the soils and sediments of the Pilliga by focussing on one part of the "sedimentary jig-saw" viz the sand bodies and evaluates how they fit into existing frameworks, both local (Pilliga) and regional (e.g: Riverina, semi-arid zone). Over the course of the study three pivotal issues have been identified and it is towards resolution of these issues that the thesis is aimed. 1. Several types of sand body have been recognised in the field; (a) Yellow sand monkey (b) Red sand monkey (c) Proposed source bordering dune (d) Deposits along current ephemeral creeks The first aim of the thesis is to characterise the different sand bodies, highlight the similarities and differences, account for the observed features and determine their origin as far as possible. 2. The sand bodies of the Pilliga form one part of a sedimentary landscape which also includes extensive clayey deposits. At present the stratigraphic relationships between the two are largely unresolved. The second aim is to advance the understanding of the palaeoenvironmental conditions that led to the depositional suite currently observed. It should be noted however, that this study does not involve a comprehensive investigation of the fine-grained deposits and as such cannot hope to entirely resolve their depositional situation. Nevertheless, a combination of stratigraphy and dating is used to more firmly establish the spatial and temporal relationships between the sand bodies and the clayey deposits, building towards a depositional history of the area. 3. Preliminary Thermoluminescence dating has obtained ages of around 45-62 ka in one of the sand bodies. Given the evidence of both climatic (Bowler 1978) and vegetation change (Dodson and Wright 1989) within that period, it is reasonable to expect that some degree of pedogenesis or post depositional modification (PDM) would affect the sand bodies in this presently sub-humid setting. Furthermore the would affect the sand bodies in this presently sub-humid setting. Furthermore the materials used in dating (quartz sand and charcoal) can be expected to be effected by bioturbation in varying ways. This mechanism has implications for PDM and the interpretation of dates. The last aim, therefore, is to undertake a preliminary assessment of pedogenesis in these sand bodies. 1.3 ORGANISATION OF THE THESIS: Due to the nature of the project and its multiple aims, the presentation does not take the form of a traditional scientific paper i.e. introduction, methods, results, discussion, conclusion. Rather, the questions outlined above will form the basis of the discrete chapters with the associated methods, results etc. adjoined. It is hoped that this format will provide greater coherence to the reader and allow more effective and focussed treatment of the material.