The conventional approach to assessing the archaeological record in most parts of the world involves a combination of excavation of stratified deposits and extensive survey of surface deposits. Although widely applied in Australia, in both research-based and management archaeology, the method does not conform well to the nature of the surface archaeological record here. Over much of semi-arid and arid Australia, archaeological "sites" are, in fact, accretion phenomena that are not easily interpreted as the outcome of short-term behavioral events. Using results from twelve years of geoarchaeological research in western New South Wales, we demonstrate that there is considerable variability in landsurface age, and hence the "availability" of archaeological surfaces, over relatively short distances. Therefore, it cannot be assumed that stone artifact deposits, for example, that appear to be similar in character are of similar age. Data are also presented that demonstrate that the presence of artifacts on the surface, their apparent absence in sediments buried beneath the surface, and the apparent recent ubiquity of the archaeological record are all a function of geomorphic processes that, at the same time, expose some artifact deposits at the surface and erode and bury others amid large volumes of sediment. Interpreting the surface artifact record within a spatial and temporal geomorphic framework is crucial to understanding the past human behavior that the artifact deposits represent.

DisclaimerThe University of Gloucestershire has obtained warranties from all depositors as to their title in the material deposited and as to their right to deposit such material.The University of Gloucestershire makes no representation or warranties of commercial utility, title, or fitness for a particular purpose or any other warranty, express or implied in respect of any material deposited.The University of Gloucestershire makes no representation that the use of the materials will not infringe any patent, copyright, trademark or other property or proprietary rights.The University of Gloucestershire accepts no liability for any infringement of intellectual property rights in any material deposited but will remove such material from public view pending investigation in the event of an allegation of any such infringement. AbstractWe present the results of a compliance-based excavation on the banks of Peach Tree Creek within the alluvial margin of the Nepean River, Penrith, NSW. The excavations consisted of: i) Two mechanically excavated trenches (3x1 m) in controlled 20 cm spits to depths of 4 m below surface; and ii) a subsequent stage of manual salvage excavation (6 m 2 ) focussing on the artefact-bearing levels indicated by the testing phase. The excavations identified two sedimentary deposits, with the lowest being part of the Cranebrook Formation, a deep alluvial deposit within which artefacts dating to >40 ka have been previously reported. We recovered four indurated mudstone/tuff and two coarse silcrete artefacts, all having characteristics of the late Pleistocene/early Holocene, and which we have OSL dated to >9.5 ka from the upper portion of the Richmond Unit of the Cranebrook Formation (3.5-3.9 m below the surface). Along with a greater understanding of the formation (only a part of which was deposited during the last 50 ka) and recent archaeological discoveries, our results lend increasing support for visitation of the Nepean river corridor by Aboriginal people as part of the initial colonisation of Australia. It remained a key locale for occupation and visitation throughout the late Pleistocene. Finally, we discuss the current NSW State government guidelines for investigating archaeological deposits and identify concerns about their effectiveness and applicability when investigating areas of potentially deep stratigraphy along the banks of the Nepean River.

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While exploration of Australian post-colonial (≤0.25 ka) OSL dating is well established in a range of natural sedimentary contexts (e.g. fluvial, aeolian, coastal), to date there have been no successful examples of the technique applied to archaeological sediments of this era. Here we present the results of a multi-phase compliance-based archaeological excavations of a new bridge crossing the Hawkesbury-Nepean River (northwest Sydney). These works identified a Last Glacial Maximum (LGM) aeolian deposit through which a colonial era drainage system had been excavated. Historical documents reveal the construction of the system occurred between 1814 and 1816 CE. An opportunistic range-finding Optically Stimulated Luminescence (OSL) sample was obtained from anthropogenic trench backfillcomposed of reworked LGM depositsimmediately above the drainage system. Minimum and Finite Mixture age models of single grain quartz OSL provided a date of 1826 CE (1806-1846 CE), in close agreement with the documented age of construction. These findings provide the first evidence of a colonial structure reliably dated using OSL, and demonstrate the feasibility of wider deployment of OSL dating to other archaeological sites of the recent era (≤0.25 ka). We propose that such environments associated with large volumes of sand-rich backfill, in particular, likely heighten OSL dating success. We propose that well-documented historical archaeological sites in Australia also have the potential to provide a robust testing ground for further evaluating the accuracy of OSL dating in a range of young archaeological sedimentary contexts, potentially to sub-decadal levels.