Physical sedimentary controls on subtropical coastal and shelf sedimentary systems: Initial application in conceptual models and computer visualizations to support archaeology

Abstract

Advances in digital spatial analysis and 3D photorealistic modeling offer the potential to create virtual interpretations of the now inundated landscapes of NW Australia. While this provides a useful template for potential late Pleistocene and early Holocene coastal occupation on the shelf, we stress the importance of understanding sediment dynamics as a primary control for terrain modelling, particularly at the scale of human ecosystem dynamics. We briefly review six major drivers of change upon tropical and semi‐tropical continental shelves and coastlines, and some of the typical coastal geomorphologies associated with each. We then hypothesize how these drivers might have varied on the NW Shelf of Australia since 65 ka, and then apply the logic to the Barrow Island region, to form some “end‐member” visualizations of coastal change in the early Holocene. The visualizations indicate a high degree of variability in coastal morphology, particularly through the post‐glacial period, which is likely to have radically changed the capacity of the coastline to provide resources for human use during that period. Hence, rather than considering any single visualization as being absolute, end‐member visualizations should be used to generate testable hypotheses that are reviewed repeatedly in the light of new physical, environmental, and archaeological information.

Aboriginal artefacts on the continental shelf reveal ancient drowned cultural landscapes in northwest Australia

“…New investigations are now under way in many parts of the world to explore the role of the coastal zone in population dispersal, to reconstruct these submerged landscapes and their palaeocoastlines and palaeoenvironments, and to test their archaeological potential [1,[14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29]. However, systematic recovery and investigation of underwater archaeological sites, which is crucial to the evaluation of new hypotheses, is inhibited by powerful and ongoing constraints.…”

Coastal dune hydrology and its influence on maritime occupation sites (12–0.2 ka) in a semiarid island, San Miguel, California, USA

“…Could analog models of the distribution of upland dune occupation sites, apparently associated with freshwater resources, be used to search for low‐stand occupation sites in San Miguel that would have been submerged by the Holocene marine transgression? Such use of search model “drivers” have been applied to the North Australian shelf, now submerged by the Holocene marine transgression (Larcombe, Ward, & Whitley, ).…”

Sedimentary unknowns constrain the current use of frequency analysis of radiocarbon data sets in forming regional models of demographic change

“…Where depositional equivalence cannot be demonstrated, it is not justifiable to combine data from separate units. Across a wide range of inland, coastal, estuarine, deltaic and shelf settings, there are many processes that can produce similar degrees of stratigraphic completeness or incompleteness (Davies et al, 2016; Holdaway & Fanning, 2014; Kidwell & Flessa, 1995; Sommerfield, 2006), with stratigraphic incompleteness the norm for most shallow marine environments, including strongly tidal estuarine and deltaic systems (Larcombe, Ward, & Whitley, 2018; Sommerfield, 2006).…”

“…Through this full glacial cycle, there have been a wide variety of physical and biogeographic changes (e.g., Figure 4) on the Australian continent and its coastal regions, associated with changing climate, sea level and solar insolation (Fitzsimmons et al, 2013; Hesse et al, 2004; B. J. Johnson et al, 1999; Kuhnert et al, 2000; J. M. Reeves et al, 2013; Wyrwoll & Miller, 2001; see also Whitley et al, 2018 for a visualisation of some of these changes in NW Australia). Combined, these changes mean that at any particular time, there are a great number of complex spatial gradients of erosion, sediment transport and sediment accumulation across the continent; and also that for any single location through time, there have been a variety of changes to sedimentary processes and geoarchaeological context (e.g., Larcombe, Ward, & Whitley, 2018). Further, archaeological data derived from these sedimentary contexts are inherently complicated, often representing polytemporal, palimpsest deposits, formed by a suite of natural and cultural processes operating at a variety of scales (Bailey, 2007; Dunnell & Dancey, 1983; Holdaway & Wandsnider, 2008).…”

“…The issues of how much of the archaeological record is preserved and can be seen or detected are of international concern (e.g., Ayala & Fitzjohn, 2002; Frederick & Krahtopoulou, 2000; Gouma et al, 2011; Holdaway & Fanning, 2014) and differences in physical processes and associated stratigraphic resolution between sites and between regions are enormous. Such differences cannot be treated simply as low‐level noise and averaged away (Larcombe, Ward, & Whitley, 2018; S. Lowe, 1981; Silva & Steele, 2014, p. 610). The conclusion is inescapable—namely, that it is impossible to make meaningful correlations and trends between sites, especially at a continental scale, without acknowledging and understanding preservation bias and stratigraphic resolution.…”