Geoarchaeology

Physical sedimentary controls on sub-tropical coastal and shelf sedimentary systems: initial application in conceptual models and computer visualisations to support archaeology.

Journal:For Geoarchaeology Peer Review Manuscript ID GEO-17-061.R1

Wiley - Manuscript type: Research Article

Date Submitted by the Author: n/a

Complete List of Authors: Larcombe, Piers; RPS Metocean; University of Western Australia, School of Earth and Environment Ward, Ingrid; Flinders University Faculty of Social and Behavioural Sciences, Archaeology; University of Western Australia, Social Sciences Whitley, Thomas; Sonoma State University

underwater archaeology, sediments, sea-level change, visualisation, Keywords: Australia

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Larcombe, Ward & Whitley – Physical sedimentary processes, sub-tropical coastlines, archaeological implications 1 2 3 Physical sedimentary controls on sub-tropical coastal and shelf sedimentary 4 5 systems: initial application in conceptual models and computer visualisations 6 to support archaeology. 7 8 P Larcombe1,2, I A K Ward3, 4, T Whitley5 9 10 1. School of Earth and Environment, University of Western Australia WA 6009, Australia 11 12 2. RPS MetOcean Pty Ltd., Jolimont, WA 6008 13 14 3. Archaeology Department, Flinders University, SA 5042 15 16 4. School of Social Sciences, University of Western Australia, WA 6009 Australia 17 18 5. Anthropological Studies Center, Sonoma State University, CA 94928, USA 19 * Corresponding author [email protected] Peer Review 20 21 22 23 ABSTRACT 24 25 26 Advances in digital spatial analysis and 3D photorealistic modeling offer the potential to create 27 28 virtual interpretations of the now inundated landscapes of NW Australia. Whilst this provides a 29 30 useful template for potential late Pleistocene and early Holocene coastal occupation on the shelf, we 31 32 stress the importance of understanding sediment dynamics as a primary control for terrain 33 34 modelling, particularly at the scale of human ecosystem dynamics. In this paper we briefly review 35 36 the six major drivers of change upon tropical and semi-tropical continental shelves and coastlines, 37 38 and their typical coastal geomorphologies. We then hypothesise how these drivers might have 39 40 varied on the NW Shelf of Australia since 65 ka, and then apply the logic to the Barrow Island region, 41 42 to form some ‘end-member’ visualisations of coastal change in the early Holocene. The visualisations 43 44 45 indicate a high degree of variability in coastal morphology, particularly through the Post-Glacial 46 47 period, which is likely to have radically changed the capacity of the coastline to provide resources for 48 49 human use during that period. Hence, rather than considering any single visualisation as being 50 51 absolute, end-member visualisations should be used to generate testable hypotheses that are 52 53 reviewed repeatedly in the light of new physical, environmental and archaeological information. 54 55 56 KEYWORDS: Underwater archaeology, sediments, sea-level change, visualisation, Australia. 57 58 Page 1 59 60 John Wiley & Sons Geoarchaeology Page 2 of 48

Larcombe, Ward & Whitley – Physical sedimentary processes, sub-tropical coastlines, archaeological implications 1 2 3 4 5 6 INTRODUCTION 7 8 9 There is increasing international interest in the role of submerged archaeological sites and 10 11 landscapes in influencing archaeological thinking on human dispersal (Bailey, 2014; Flemming, 2017, 12 13 and references therein). Unlike the rest of the world, Australia has no record yet of submerged 14 15 archaeological sites (Nutley, 2014; Ward & Veth, 2017) , despite the evidence of human occupation 16 17 back beyond 50 ka (Malaspinas et al., 2016; Clarkson et al., 2017; Veth et al., 2017) and the 18 19 For Peer Review 20 widespread regional presence of preserved drowned shorelines (Fairbridge, 1964 in Wyrwoll, 21 22 1979:134; Brook et al., 2017). The investigation of drowned landscapes is therefore particularly 23 24 important for Australia where virtually all evidence of late Pleistocene and early Holocene coastal 25 26 living in Australia has been submerged (Ulm, 2011). 27 28 29 To begin to address this knowledge gap and aid prospection of the as-yet unknown submerged 30 31 archaeological potential, as well as to help assess the past changes in the availability of coastal 32 33 resources for humans, Ward et al. (2013) combined relative Post-Glacial sea levels with modern 34 35 bathymetric data to develop a series of maps to illustrate the inundation history of the Dampier 36 37 Archipelago region of NW Australia. These relatively basic maps clearly demonstrated the first-order 38 39 effects of Post-Glacial coastal changes on the NW Shelf. However, the development of coastal 40 41 42 resources and their human use are perhaps more likely to be controlled by second and third-order 43 44 effects associated with movement of sediments and resultant variations in coastal sedimentary 45 46 environments (Ward et al., 2015). 47 48 49 Approaches that are more sophisticated use computer-based visualisations to illustrate past change 50 51 – often termed computer simulations for models of change through time (Lake, 2014; his italics). 52 53 The capacity of computer-based visualisations to illustrate past change is now almost limitless, with 54 55 computers able to deal with vast and complex datasets related to climatic, ecological, environmental 56 57 58 Page 2 59 60 John Wiley & Sons Page 3 of 48 Geoarchaeology

Larcombe, Ward & Whitley – Physical sedimentary processes, sub-tropical coastlines, archaeological implications 1 2 3 and human systems. The current trend in archaeological simulation is towards greater 4 5 environmental realism, through the explicit inclusion of environmental heterogeneity and human 6 7 impact on the environment (Lake, 2014; d’Alpoim Guedes et al., 2016). The problem is that such 8 9 ‘realism’ can be taken at face value or, as per McGlade (1995: 129), as abstract representations of 10 11 some ‘real world’ phenomena, rather than as a resource with which to test a range of 12 13 interpretations – for example, in the positioning and nature of past coastlines. 14 15 16 For archaeologists, the “location of a coastline” and the elevation of regional sea level are often 17 18 principal factors in explaining whether and how people might have migrated around the world, or 19 For Peer Review 20 how they adapted a coastal way of life (Bailey & Parkington, 1988). However, in our view, the 21 22 concept that the coastline has a precise location is a misnomer because locations fluctuate with 23 24 25 time, firstly due to the rise and fall of the tides, but more significantly due to temporal changes in 26 27 the location and form of coastal sediment accumulations. Indeed, a recent study of regional coastal 28 29 changes with Post-Glacial sea-level rise change explicitly acknowledges the lack of such inclusion – 30 31 “Our models do not account for topographic (sic) changes associated with sediment erosion and 32 33 deposition, which might be important in this region” (d’Alpoim Guedes et al., 2016). In this case, 34 35 and many others, the past ‘line’ of the coast is indeed unknown and, if sediment bodies are later 36 37 removed, it might even be unknowable. This does not mean that there is no value in such regional 38 39 reconstructions, but means that there is a need to understand better the archaeological significance 40 41 of their recognised limitations. 42 43 44 What is generally referred to as the coastline actually incorporates a range of physical sedimentary 45 46 environments and associated ecosystems. Correspondingly, there are multiple perceptions of the 47 48 natural world and these are both scale-dependent and context-specific (McGlade, 1995: 126). From 49 50 51 an archaeological perspective, these coastal contexts and their change over time both need to be 52 53 defined before or as part of any assessment of human coastal and aquatic adaptations (Bailey & 54 55 56 57 58 Page 3 59 60 John Wiley & Sons Geoarchaeology Page 4 of 48

Larcombe, Ward & Whitley – Physical sedimentary processes, sub-tropical coastlines, archaeological implications 1 2 3 Parkington, 1988); or for assessment of the likely location and preservation potential of submerged 4 5 archaeological sites (Ward et al., 2015). 6 7 8 Conceptual models formed for archaeological purposes will be most useful when founded on 9 10 realistic processes of coastal sedimentary evolution, and on thorough on-site investigations (e.g. 11 12 Inda et al., 2017) that enable researchers to test, advance or reject these models. It is important to 13 14 consider the nature of the coastal sedimentary environments involved because of their capacity to a) 15 16 provide different resources (economic and utilitarian, Bailey & Parkington, 1988; Fitzpatrick et al., 17 18 2015), b) drive different technological developments (e.g. fishing technologies, Dortch, 1997; 19 For Peer Review 20 Colaninno, 2011); and c) impact archaeological site preservation (Tveskov & Erlandson, 2003; Ward 21 22 & Larcombe, 2008; Ward et al., 2015). In this paper, we hope to improve matters by promoting a 23 24 25 process-based geoarchaeological approach. 26 27 The paper has four main sections. First we describe i) a selection of physical sedimentary 28 29 30 environments relevant to tropical and sub-tropical continental shelves, and ii) six fundamental 31 32 physical drivers that control such shelves, their coastlines and their typical coastal morphologies, and 33 34 then iii) hypothesise how these drivers might have varied on the NW Shelf of Australia since 65 ka. 35 36 Fourthly, iv) we apply the logic to the Barrow Island region to form some ‘end-member’ 37 38 visualisations of coastal change in the early Holocene with which to assess how coastal 39 40 environments might have changed as the continental shelf was being flooded during the Post-Glacial 41 42 transgression. 43 44 45 It is unrealistic to expect any single ‘model’ of past change to encompass adequately the diverse 46 47 natural (including physical) and cultural factors that comprise human ecodynamic systems, so that, 48 49 instead, a suite of scenarios are preferred (McGlade, 1995). Together, such scenarios can be used to 50 51 focus archaeological thinking and assist with hypothesis generation, by superimposing 52 53 considerations of human use and occupation patterns onto some of the more likely physical 54 55 56 scenarios. Our example of Australia’s NW Shelf, including the area near Barrow Island, is a region of 57 58 Page 4 59 60 John Wiley & Sons Page 5 of 48 Geoarchaeology

Larcombe, Ward & Whitley – Physical sedimentary processes, sub-tropical coastlines, archaeological implications 1 2 3 significant active coastal and marine archaeological research (Veth et al., 2017); however, we do not 4 5 propose or promote a particular set of past physical changes during the period of human occupation 6 7 because a) there is insufficient geological and palaeoenvironmental evidence at present, and b) 8 9 there is great complexity of the driving physical processes. We do consider the validity and potential 10 11 use of the suite of visualisations in the light of available palaeoenvironmental and archaeological 12 13 information for the Barrow Island region. 14 15 16 17 18 19 WHAT CONTROLS COASTLINESFor ANDPeer HOW DO Review WE CONSIDER THEM? 20 21 22 Types of coastline 23 24 In the geological, geographical and sedimentological literature, the complexity and dynamics of 25 26 coastlines are well-described (Boyd et al., 1992; Dyer, 1986; Davis & Dalrymple, 2012). Coastlines 27 28 may be characterized in many ways, including in terms of their long-term mobility (e.g. hard or 29 30 31 ‘soft’), their shape seen in 2D or 3D form, their perceived long-term location change (e.g. prograding 32 33 and eroding), their planform (i.e. morphology seen from above), their tendency for stability or 34 35 (rapid) change and their driving processes (e.g. high-energy, sheltered, macrotidal, microtidal, etc). 36 37 However, viewed simply, sedimentary environments can be considered as a combination of just 38 39 three main factors: the volume of the sediments themselves, their physical nature and composition, 40 41 and their dynamics (Pethick, 1984), the interactions of which are able to generate environments as 42 43 different as muddy mangrove swamps, sandy beaches and gravelly coastal bars. Coastline 44 45 characterization schemes can sometimes mix these factors, and contain implicit assumptions about 46 47 relationships between them. One consequence is that, taking an archaeological point of view, some 48 49 50 ‘types’ of shoreline might be erroneously taken as a clear indication of certain conditions which are 51 52 viewed as favourable or not to human use of some kind. It is therefore useful to elucidate some of 53 54 these factors to help clarify some of their implications for archaeology. 55 56 57 58 Page 5 59 60 John Wiley & Sons Geoarchaeology Page 6 of 48

Larcombe, Ward & Whitley – Physical sedimentary processes, sub-tropical coastlines, archaeological implications 1 2 3 The example of estuaries 4 5 6 Whilst estuaries have been dealt with exhaustively in the literature (Davis & Dalrymple, 2012; Dyer, 7 8 1986; Masselink, 2011; Nichols & Biggs, 1985) in our context, they are particularly useful because 9 10 they encompass a very wide range of ‘coastal environments’ pertinent to human use. Estuaries are 11 12 resource-rich contexts for Aboriginal people both past (McBryde et al., 1982; McNiven, 2003; Ross, 13 14 2009; Manne & Veth, 2015; Veth et al., 2016) and present (Jackson et al., 2012; Russell et al., 2015). 15 16 17 Their physical environments are many and varied, including: back barrier, central basins, channels, 18 19 flood and ebb tidal deltas,For bay-head Peer deltas, intertidal Review flats, mangroves, rocky reefs, saltmarshes, 20 21 saltflats, tidal sand banks, etc. (Boyd et al., 1992; Dalrymple et al., 1992). The dynamics and 22 23 geomorphological characteristics of these environments and their general physical associations are 24 25 well documented, (Dyer, 1986; Dalrymple et al., 1992) and form a major part of modern descriptive 26 27 frameworks aimed to assist management. 28 29 30 The triangular diagram of Dalrymple et al. (1992) and Boyd et al. (1992) was established largely to 31 32 describe estuaries, and discriminates coastal environments across three axes (Figure 1). The points 33 34 of the diagram represent ‘estuarine’ geomorphologies produced by the overwhelming dominance, 35 36 on ‘geological’ timescales of perhaps centuries and longer, of each of the three drivers - waves 37 38 (dominant at bottom left), tides and rivers - resulting in three main suites of distinct sedimentary 39 40 environments, namely deltas, strandplains and tidal flats (Figure 1). Intermediate areas represent 41 42 43 different combinations of environments, for example tide-dominated and wave-dominated 44 45 estuaries, below which lie coastal lagoons where river influence is negligible and tidal influence is 46 47 weak (Boyd et al., 1992). For our purposes, river influences can be taken a little simplistically to 48 49 indicate ‘terrigenous sediment supply’. Clearly, such diagrams are qualitative and the boundaries 50 51 between regions are illustrative only, but as noted above, there are key archaeological advantages 52 53 to consider such elements in archaeological research. 54 55 56 57 58 Page 6 59 60 John Wiley & Sons Page 7 of 48 Geoarchaeology

Larcombe, Ward & Whitley – Physical sedimentary processes, sub-tropical coastlines, archaeological implications 1 2 3 As noted above, the estuarine ternary diagram (Figure 1) was designed to illustrate the long-term 4 5 results of geological processes, rather than consider the dynamic nature of coastlines, and therefore, 6 7 it does not necessarily consider the relative role of episodic events compared to day-to-day 8 9 processes in shaping the coast and adjacent shelf. Major and rapid change is intrinsic to many 10 11 coastlines, sometimes linked to El Nino Southern Oscillation (ENSO) or some other atmospheric- 12 13 ocean interaction (Woodroffe & Murray-Wallace, 2014) as well as changes in the delivery and the 14 15 coastal configuration of sediments (e.g. Lewis et al., 2014; Stanley & Clemente, 2017). Storms, 16 17 Tropical Cyclones and other ENSO-related events can have an immediate impact on coastal 18 19 For Peer Review 20 geomorphology, water circulation and ecology in coastal estuarine systems, because of inundation, 21 22 barrier overwash or breaching (Hopley, 1974; Filgueira, 2014; May et al., 2017). In terms of coastal 23 24 dynamics, key parameters include the intensity and repetition of those events that dictate whether 25 26 the change is short-term or chronic. Although the ternary diagram of Figure 1 does not easily deal 27 28 with such events, it incorporates many different physical features of coastlines, and is a convenient 29 30 way to help illustrate the potential nature of coastlines and their changes. Below, to underpin 31 32 associated archaeological implications, we describe a case study of past coastal change in the 33 34 Barrow Island region, NW Shelf, Australia, but it is first necessary to describe key drivers of coastal 35 36 change in sub-tropical latitudes, with examples, and include general consequences for archaeology. 37 38 39 Drivers of change 40 41 42 Here we consider the ‘coastline’ to include a suite of sedimentary environments, including those of 43 44 the adjoining continental shelf, deltas, estuaries and rivers, and the coastal plain. We also describe 45 46 six main physical drivers of change, i) shelf bathymetry, ii) fluvial sediment delivery, iii) shelf 47 48 sediment availability, iv) waves, v) tidal range and currents, and vi) cyclones. Of course coastal 49 50 environments are influenced by a mixture of all these drivers, and our purpose here is certainly not 51 52 to argue that these individual drivers are the definitive drivers for those cases described below, but 53 54 rather to show that they are clearly useful to help illustrate some key aspects relevant to 55 56 archaeology. In passing, we do not consider sea-level change as a driver because a) it is a secondary 57 58 Page 7 59 60 John Wiley & Sons Geoarchaeology Page 8 of 48

Larcombe, Ward & Whitley – Physical sedimentary processes, sub-tropical coastlines, archaeological implications 1 2 3 factor that merely influences other drivers as part of the geological history, including archaeological 4 5 site preservation (Ulm, 2011; Rowland & Ulm, 2012), and b) there are a range of assumptions about 6 7 how former coastlines and human use are linked with sea-level change (Beaton, 1995; O’Connell & 8 9 Allen, 2012), some of which can be inaccurate (see Ward et al., 2015). Further, we show below that 10 11 a relatively precise understanding of the interactions of past relative sea level, coastal configuration 12 13 and sedimentation is necessary to be able to make defensible statements about the implications for 14 15 human use of coastal environments and preservation potential. Hence, use of sea-level change (and 16 17 curves) alone for such archaeological purposes appears, unfortunately, flawed. Palaeotidal and 18 19 For Peer Review 20 other modelling is increasingly helping understanding of the potential range of oceanographic and 21 22 sediment dynamics on the shelf at lower relative sea levels, especially through the transgression, 23 24 with archaeological inferences beginning to be drawn (Ward et al., 2013; Bird et al., 2016), however 25 26 much remains to be done on the associated sedimentary factors. 27 28 29 i. Shelf bathymetry 30 31 Shelf bathymetry can control sedimentation through the influence it has on the space available for 32 33 sediments to accumulate, called accommodation space (Jervey, 1988). Shelf bathymetry also 34 35 modulates oceanographic processes and thereby sedimentation patterns, and, of course, where 36 37 sediment accumulation rates are low, the pre-existing bathymetry itself becomes significant. An 38 39 example of shelf bathymetry as a driver is the shelf in the region of Lindi, southern Tanzania (Figure 40 41 42 2A). Here, the coastline and the bathymetry of the narrow shelf are derived largely from the river 43 44 and continental slope processes of the last few million years or more (Liu et al., 2016a, b; 2017). The 45 46 monsoon-associated north-flowing East African Coastal Current (EACC), and associated deeper 47 48 currents have transported marine sediments northwards along the slope, with currents of up to 2 49 50 m/s during the SE monsoon (Shaghude & Wannas, 2000) and 0.2 m/s during the NE monsoon 51 52 (Newell, 1957). The slope is incised by numerous submarine canyons that carry sediment from the 53 54 rivers and shelf down the continental slope (Bourget et al., 2008; Liu et al., 2016a) bypassing the 55 56 shelf. Narrow fringing reefs form along the coast between river mouths that occupy embayments 57 58 Page 8 59 60 John Wiley & Sons Page 9 of 48 Geoarchaeology

Larcombe, Ward & Whitley – Physical sedimentary processes, sub-tropical coastlines, archaeological implications 1 2 3 formed through fluvial processes at lower sea levels. Overall, there has probably been relatively 4 5 little change in the coastal geomorphology, and only a few kilometres of change in its location, over 6 7 the last 50 ka or longer (Kent et al., 1971). Although the East African coast itself has a relatively 8 9 uniform topography and environment, it has a complex cultural record relating to ancient 10 11 transoceanic interacts cross the Indian Ocean (Breen & Lane, 2003), with preliminary surveys 12 13 pointing toward a similarly rich maritime and underwater cultural heritage (Bita & Tripati, 2015). 14 15 16 An example in NW Australia of a coastline controlled by shelf bathymetry is Roebuck Bay, at Broome, 17 18 where the presence of extensive submerged palaeoshorelines to seawards has contributed to the 19 For Peer Review 20 formation of a wide sheltered embayment, rich in resources, and flushed daily by the macrotidal 21 22 regime (Wilson, 2013). Over the last few thousand years, this would have provided ample resources 23 24 25 for humans. Further, in terms of preservation potential, the sheltered, progradational coastline and 26 27 likely associated accumulation within the bay would indicate excellent conditions for archaeology. 28 29 30 ii. Fluvial sediment delivery 31 32 Fluvial sediment supply is the driver of the Burdekin Delta, Queensland (Figure 2B), the largest river 33 34 delta in Australia, through which is transported an average of ~3.5 million tonnes of sediment each 35 36 year (Neil et al., 2002). The delta directly controls >100 km of the modern coastline, both directly 37 38 through riverine flow and freshwater plumes, but also through modification of the ‘downdrift’ 39 40 shoreline to the north, where successive bays (Upstart Bay, Bowling Green Bay, Cleveland Bay) 41 42 receive pulses of the sediment from the modern river mouth, and through both avulsion and 43 44 channel switching over the last few thousand years (Lewis et al., 2014). Although cyclones and wind- 45 46 47 driven currents transport sediment at the delta front itself, the morphology of the prograding delta 48 49 itself is a direct result of the dominance over many millennia of fluvial sediment delivery over other 50 51 sedimentary processes (Fielding et al., 2012). Hence, these drivers will have predominantly 52 53 influenced primary and secondary archaeological deposits. 54 55 56 57 58 Page 9 59 60 John Wiley & Sons Geoarchaeology Page 10 of 48

Larcombe, Ward & Whitley – Physical sedimentary processes, sub-tropical coastlines, archaeological implications 1 2 3 An example of a dominant fluvial driver in NW Australia is the prominent De Grey River delta that 4 5 extends 80 km along the coast and projects 30 km out from the hinterland in the Pilbara region. 6 7 Rainfall, river flow and hence sediment supply is seasonal and highly intermittent, so landform 8 9 changes can be highly variable (Stul et al., 2014). Inland, all of the main tributaries in the De Grey 10 11 River basin have wells and springs in their headwaters and numerous pools along their courses, 12 13 which are of cultural significance (Environment Australia, 2001), and these may have extended 14 15 offshore during lower sea levels. 16 17 18 iii. Shelf sediment availability 19 For Peer Review 20 21 An example of shelf sediment supply as a driver is the SE African shelf (Figure 2C). This shelf and 22 23 coastline is dominated by a remarkably fast oceanic current, the Agulhas Current that flows SSW 24 25 along the shelf at speeds up to 2.45 m/s (Flemming, 1981; 1983; see also Flemming & Martin, 2017 26 27 and references therein). It drives a dynamic patchy sand transport pathway located on the central 28 29 shelf that in places forms submarine dunes of up to 200 m in spacing and 8 m in height, and a variety 30 31 of other bedforms. At depths of 50-65 m, the pathway interacts with a series of drowned barrier 32 33 shorelines that segment a palaeo-lagoon complex (Green et al., 2014) with a range of potential 34 35 resources for past human exploitation. The shelf sediment cover is patchy and of highly variable 36 37 thickness, so that across the shelf there are large changes in sedimentary regime and hence 38 39 archaeological preservation potential (Flemming & Martin, 2017). 40 41 42 A similar scenario exists on the inner shelf at James Price Point in Western Australia (Ward et al., 43 44 2016). Here, bathymetrically prominent cemented palaeoshoreline sequences are preserved at -15 45 46 47 m and – 8 m depth, between which are bodies of tidally mobile foraminiferal sands that form a long- 48 49 term along-shelf sediment transport pathway towards the south, driven by cyclone-induced flows. 50 51 Whilst the cemented palaeoshoreline ridges themselves are likely to preserve archaeology (Ward et 52 53 al., 2016), the past sediments located between the palaeoshorelines, and any associated 54 55 archaeology, are likely to have been subject to (at least) partial removal through subsequent 56 57 58 Page 10 59 60 John Wiley & Sons Page 11 of 48 Geoarchaeology

Larcombe, Ward & Whitley – Physical sedimentary processes, sub-tropical coastlines, archaeological implications 1 2 3 southward transport. In both the above examples, the availability of shelf sediment and its 4 5 transport clearly influences the formation and preservation potential of deposits of archaeological 6 7 interest. 8 9 10 iv. Waves (including seasonal winds) 11 12 The shelf off SW Western Australia (Figure 2D) is high-energy and influenced by Southern Ocean 13 14 swells and storms (Richardson et al., 2005). Large waves occur at most times of the year, with 15 16 offshore significant wave heights of up to 10 m in winter and spring. The coastline features rocky 17 18 promontories between which lie sandy reef-bounded embayments, some with large fields of coastal 19 For Peer Review 20 21 dunes, and other more exposed steep coarse beaches (Shore Coastal, 2015). The highly energetic 22 23 wave regime, combined with the strong coast-parallel currents, means that there is a highly 24 25 erosional sedimentary regime along most of the coastline and on the adjacent shelf (Carrigy & 26 27 Fairbridge, 1954; Li et al., 2009). The modern bathymetric contours are coast-parallel, down to the 28 29 shelf edge at 160-180 m depth and beyond, indicating that the general wave-dominated regime is 30 31 likely to have been similar through the last 50 ka or more. 32 33 34 In general, prehistoric sites in shallow waters or along the coast, exposed to destructive effects of 35 36 wave action and scouring currents particularly during storm events, may be dispersed or destroyed 37 38 (Stewart, 1999). In terms of submerged sites, studies by Nutley (2006) in Sydney Harbour indicate 39 40 that even in an area with limited exposure to wave action, archaeological sites are extremely 41 42 vulnerable to inundation, particularly when associated with steep slopes or flat rock shelves 43 44 periodically awash during high tides or floods. Nutley (2009) concluded that few archaeological 45 46 47 features would have sufficient physical resistance to survive the full force of coastal waves on an 48 49 oceanic coast like New South Wales; rather, rapid inundation is key to preservation. There appears 50 51 similarly little prospect of finding submerged archaeological sites on the shelf of SW Western 52 53 Australia, even on the rocky promontories, because of combined mechanical forces of wave action 54 55 56 57 58 Page 11 59 60 John Wiley & Sons Geoarchaeology Page 12 of 48

Larcombe, Ward & Whitley – Physical sedimentary processes, sub-tropical coastlines, archaeological implications 1 2 3 with periodic inundation (wetting) and exposure (drying), unless they are buried by or protected 4 5 behind a frontal beach-barrier system. 6 7 8 v. Tidal range (and flow directions) 9 10 Much of the NW shelf of Australia is subject to very large tidal ranges (up to > 12 m at Broome). A 11 12 series of large funnel-shaped estuaries occur in the Joseph Bonaparte Gulf (tidal range 2 - 4 m) that 13 14 itself has a similar funnel shape (Figure 2E). The area experiences fast tidal currents, generally 15 16 orientated perpendicular to the coastline, and the coastal sedimentary environments include 17 18 extensive tidal creek systems (< 70 km long), mudflats up to 10 km wide, large areas of estuarine 19 For Peer Review 20 21 mangrove systems and saltflats, and an array of chenier ridges (Coleman & Wright, 1978; Lees, 22 23 1992a, b). This range of environments provides a wealth of potential human resources. The modern 24 25 bathymetry indicates that the tidal channels, which contain very large mobile sandy bedforms, 26 27 extend well out into the subtidal zones to depths of 30 m and beyond, where they have a greater silt 28 29 component (Clarke & Ringis, 2000; Przeslawski et al., 2011). The system’s present and past 30 31 dynamics (Clarke & Ringis, 2000; Lees, 1992a, b) indicate that for this section of coastline at least, 32 33 the tidally dominated regime and the sedimentary environments have probably been similar for the 34 35 last 8 - 5 ka. Therefore, there has been thousands of years of strong reworking of inner-shelf and 36 37 coastal sediments and hence of any associated archaeology. 38 39 40 Macro- and meso-tidal estuarine morphologies (meandering or sinuous channels, often funnel 41 42 shaped; multiple channels, bars and banks) also occur extensively at the coast in the northern part of 43 44 Australia’s NW Shelf (Brooke et al., 2017). In the Dampier Archipelago region (Figure 2F), Ward et al. 45 46 47 (2013) investigated the likely tidal regime changes over the Holocene transgression, and described 48 49 how deposits across the shelf have had greatly varying potential to be reworked by the changing 50 51 tidal currents. Tidal sediment reworking was particularly high, for example, during the middle part 52 53 of the Holocene transgression, at the time when relative sea level (RSL) was 50 – 30 m below 54 55 present. Further, the simulations indicated that, in the last 9 - 7 ka alone, at a single location just off 56 57 58 Page 12 59 60 John Wiley & Sons Page 13 of 48 Geoarchaeology

Larcombe, Ward & Whitley – Physical sedimentary processes, sub-tropical coastlines, archaeological implications 1 2 3 the modern archipelago, peak spring tidal speeds were mostly coast parallel, and increased at this 4 5 location through the middle and late Holocene. When relative sea level (RSL) was at 20 m below 6 7 present, peak tidal speeds were approximately 0.25 m/s, able to move fine sand. Later, at an RSL of 8 9 10 m below present, the peak had increased to 0.35 m/s, able to move medium-coarse sand, until at 10 11 modern sea levels, the peak tidal speed attained ~0.75 m/s, able to move all grades of sand, and fine 12 13 gravel (Ward et al., 2013). 14 15 16 In both cases described above, most drowned coastal deposits are likely to have been completely 17 18 reworked by the strong tidal processes that developed over the shelf during the latter stages of the 19 For Peer Review 20 Post-Glacial sea-level rise, to say nothing of the greatly enhanced currents and bed mobility induced 21 22 by the thousands of cyclones over the same period. The key exceptions to this are drowned 23 24 25 cemented shoreline sands, many of which remain as prominent relief features on the sea floor (e.g. 26 27 Brooke et al., 2017; see section vi below). 28 29 30 vi. Cyclones/Hurricanes/Typhoons (and their effects) 31 32 In sub-tropical regions, cyclones and seasonal tropical storms can be critical controls on coastal 33 34 geomorphology, for example, through reworking coastal sediments during storm surges. Such 35 36 regions also house ample sedimentary environments able to provide both resources for humans 37 38 (Ward et al., 2015) and conditions likely to allow some preservation of coastal archaeology. As an 39 40 example, cyclones are a key driver of sedimentary environments (Figure 2G) on the central Great 41 42 Barrier Reef (GBR) shelf, especially the middle shelf but also parts of the inner shelf and coastline 43 44 (Larcombe & Carter, 2004; Nott, 2006; Carter et al., 2009) where cyclones have been a routine 45 46 47 occurrence for more than the last 6000 years. Current measurements, sedimentary bedforms, 48 49 sedimentary facies distributions and sea-bed cores all indicate intense cyclone-driven reworking of 50 51 the GBR seabed, out to water depths of > 40 m, associated with very low net sediment accumulation 52 53 rates (2-20 mm / 1000 yrs). Hence, the seabed is dominated by episodic reworking and transport 54 55 events, with the seabed reworked to depths of 10-30 cm by major events. Mean recurrence 56 57 58 Page 13 59 60 John Wiley & Sons Geoarchaeology Page 14 of 48

Larcombe, Ward & Whitley – Physical sedimentary processes, sub-tropical coastlines, archaeological implications 1 2 3 intervals have been calculated between each complete ‘resetting’ of various shelf and coastal 4 5 sedimentary environments (Table 1). It is important to note that a) the stratigraphy will be 6 7 incomplete in regions where net sediment accumulation is slow or absent, and b) that the preserved 8 9 stratigraphy represents only the most major events, because large events might themselves rework 10 11 a series of previous smaller ones. Therefore, statistically, the actual resetting times will be around 3- 12 13 5 times as often, i.e. varying between a minimum of ~25 yrs for the inner shelf and 200 years for the 14 15 middle shelf (Larcombe & Ridd, 2015). Thus, most coastal and shelf environments are reset on 16 17 relatively short timescales compared to most archaeological studies, so that the likelihood of 18 19 For Peer Review 20 deposits remaining undisturbed is extremely low. 21 22 A similar array of physical evidence occurs at a wide variety of depths on Australia’s cyclone- 23 24 25 influenced NW Shelf (Jones, 1973; Jones et al., 2009, Larcombe et al., 2014; Belde et al., 2015) 26 27 although relatively little material has been dated. On the inner and middle shelf are located 28 29 extensive fields of asymmetric very large submarine sand and gravel dunes (sensu Ashley et al., 30 31 1990), almost universally aligned with the steep sides facing SSW along the shelf, and an array of 32 33 other large sedimentary bedforms. This evidence is consistent with the speed and direction of 34 35 cyclone-associated currents, as theorized, measured and modelled, causing along-shelf bed 36 37 sediment transport over many decades and centuries (Larcombe et al., 2014, cf. Larcombe & Carter, 38 39 2004). 40 41 42 There are profound archaeological implications. The sediment dynamics of shelf environments in 43 44 northern Australia indicate frequent likely burial, exposure and/or reworking of archaeological 45 46 remains, with reworking of material on the shelf being particularly intense and extensive, thus 47 48 influencing preservation of non-indurated seabed features, particularly during the latter stages of 49 50 51 the Post-Glacial transgression (Ward et al., 2015). It is unsurprising that, in Upstart Bay in North 52 53 Queensland, Bird (1992, 1995) found that the majority of known archaeological sites were 54 55 significantly reduced, modified or destroyed after Tropical Cyclones Charlie in 1988 and Aivu in 1989. 56 57 58 Page 14 59 60 John Wiley & Sons Page 15 of 48 Geoarchaeology

Larcombe, Ward & Whitley – Physical sedimentary processes, sub-tropical coastlines, archaeological implications 1 2 3 Over much longer timescales, local favorable locations at some inner-shelf islands, and along certain 4 5 sections of the coastline where sediment has accumulated more or less constantly, will provide the 6 7 best preservation potential for archaeological deposits. Locating such areas and interpreting any 8 9 archaeology found will be informed by understanding past sediment dynamics. 10 11 12 13 CASE STUDY - THE SHELF OFF MODERN BARROW ISLAND, WESTERN AUSTRALIA 14 15 Located halfway out across the NW Shelf, Barrow Is. is well positioned to provide relevant 16 17 information on the different phases of physical shelf evolution and human occupation over the last 18 19 For Peer Review 20 50,000 years or so (Veth et al., 2017). Current water depths between the east coast of the island 21 22 and the mainland generally do not exceed 20 m. Tidal ranges are moderate (3 m at Mean High 23 24 Water Springs) and semi-diurnal, which, combined with the shallow bathymetry along the east side 25 26 of Barrow Island, results in large areas of exposed seabed at low tide. In contrast, the west coast of 27 28 the island is exposed to waves arriving from the Indian Ocean that refract around the northern and 29 30 southern ends of the island. Prevailing winds are south to south-westerly, with a mean speed of 5.8 31 32 m/s and mean maximum of 19.4 m/s (Holloway & Nye, 1985). Barrow Island is located in a region 33 34 with very frequent Tropical Cyclone activity, with one cyclone every two years passing within 50 35 36 nautical miles of the island1. 37 38 39 Excavations on Barrow Is. have indicated that by 42.5 ka humans were gathering wood (Avicennia 40 41 marina and Bruguiera exaristata) and shell resources (specifically Terebralia, Tellina, Nerita and 42 43 Melo) from mangrove, mudflat and rocky substrates (Veth et al., 2017). Fuel wood (including Acacia 44 45 46 spp. and Eucalyptus spp.) was also being harvested along freshwater watercourses. In the early 47 48 Holocene, people were exploiting mangrove environments as well a more diverse range of marine 49 50 fauna, including fish, turtle, marine mammal, crab, sea urchin and over 40 species of marine mollusc 51 52 (Veth et al., 2017). The presence of mangrove and mudflat species are clear indications of tidal 53 54

55 1 www.bom.gov.au/cyclone/history/wa/onslow.shtml 56 57 58 Page 15 59 60 John Wiley & Sons Geoarchaeology Page 16 of 48

Larcombe, Ward & Whitley – Physical sedimentary processes, sub-tropical coastlines, archaeological implications 1 2 3 influence of the coastal environment around Barrow Is.. This is further supported by (i) palynological 4 5 data indicating prior to 38 ka, a fringe vegetation of mangroves and chenopod salt-marshes that 6 7 became more extensive around 12 ka with drowning of the shelf (van der Kaars, 1991); (ii) the 8 9 presence of calcareous ooids on the mid-ramp of the Rowley Shelf, dated at 15.4 – 12.7 ka (James et 10 11 al., 2004), and which are interpreted as having formed in a shallow (< 5 m) tide-dominated coastal 12 13 setting with elevated salinity; and (iii) the mesotidal palaeotidal regime indicated for the nearby 14 15 Dampier Archipelago region of the shelf (Ward et al., 2013). Through the Holocene, the strong tidal 16 17 influence will have been combined with additional physical drivers. 18 19 For Peer Review 20 As presented in Whitley (2017: 6), a high-resolution bathymetric model provides some predictions 21 22 for the multidirectional movements of sediment and of the coastal zone from the time of earliest 23 24 25 human colonization through until today. We use this experimental application of ‘Terragen’ to 26 27 develop, visualise and emphasise some of the possible physical factors and their changes through 28 29 time that need to be considered when designing archaeological prospection in the offshore zone and 30 31 also when interpreting archaeological data collected offshore, on the emergent islands and from the 32 33 adjacent mainland. 34 35 36 Positing the main drivers controlling coastal sedimentary environments. 37 38 Before developing any terrain visualisation, we first posit the changing relationships between the 39 40 main drivers controlling coastal sedimentary environments along the Barrow Island section of the 41 42 NW Shelf from 65 ka to present (Table 2), illustrated here at key points in the past (Figure 3). These 43 44 drivers are not readily quantifiable, so our assessment is a simple qualitative comparison, expressed 45 46 47 using a 1-4 scale. As a starting point, we posit that the modern sedimentary conditions for the NW 48 49 shelf are dominated by shelf bathymetry, tidal range and cyclones, more or less equally, with shelf 50 51 sediment availability the next important, and finally, with least influence, fluvial sediment delivery 52 53 and waves. The coastal and shelf sedimentary composition, distribution, suite of bedforms and 54 55 56 57 58 Page 16 59 60 John Wiley & Sons Page 17 of 48 Geoarchaeology

Larcombe, Ward & Whitley – Physical sedimentary processes, sub-tropical coastlines, archaeological implications 1 2 3 sedimentary environments all indicate that, for the modern shelf, there is the regional importance 4 5 of: 6 7 8 • the pre-existing shelf topography, because most Post-Glacial Holocene deposits are thin and 9 10 there are many bathymetric features and islands derived from drowned shorelines (e.g. 11 12 Baker et al., 2008; Wilson, 2013) (score 4); 13 14 15 • the widespread occurrence of mesotidal to macrotidal estuaries (e.g. Lees, 1992a) (score 4) 16 17 and 18 19 For Peer Review 20 • cyclone-associated features on the seabed (Larcombe, 2014; Ward et al., 2016; cf. Belde et 21 22 al., 2015; 2017) (score 4). 23 24 25 Less prominent is the influence of shelf sediment availability, whereby many sediments on the NW 26 27 Shelf, but fewer geomorphic features, are formed of biogenic sediments (e.g. James et al., 2004; Dix 28 29 et al., 2005) and Holocene thicknesses are generally thin and patchy (score 3). Finally, the modern 30 31 shelf and coastline overall is broadly starved of modern terrigenous sediment supply from rivers 32 33 although there are some minor deltas in places (Ryan et al., 2003) (score 2), and there are relatively 34 35 few (but not zero) features indicative of the dominance of non-cyclonic waves (score 2). 36 37 38 We emphasise that this starting point is not asserted to be necessarily “correct”, nor is it based 39 40 simply on the features of the coastline itself, in which case, for example, the influence of waves 41 42 43 would have a higher score in controlling the nature of beaches (e.g. Eliot et al., 2011). Rather, the 44 45 critical issue here is the archaeological value gained in realizing that the relative importance of these 46 47 drivers has varied though time. To illustrate such variation and underpin some archaeological 48 49 consequences, we have chosen a suite of past critical points in the shelf’s evolution (Table 2), and 50 51 plotted out the estimated scores for each driver (Figure 3). We explain the reasoning below (see 52 53 also references in Table 3). 54 55 56 57 58 Page 17 59 60 John Wiley & Sons Geoarchaeology Page 18 of 48

Larcombe, Ward & Whitley – Physical sedimentary processes, sub-tropical coastlines, archaeological implications 1 2 3 • The literature indicates that the glacial lowstand tidal range at 20 ka (Yokoyama et al., 2001; 4 5 Siddall et al., 2003) was almost twice as great as today (Rudnick and Ferrari, 1999; Egbert et 6 7 al., 2004), so there are likely to have been large intertidal flats and a productive coastline 8 9 with the capacity to have provided marine resources (James et al., 2004; Ward et al., 2015). 10 11 The widespread presence of many drowned valley systems on the middle and outer shelf 12 13 (e.g. Baker et al., 2008; Wilson, 2013) indicates the possibility of large estuaries, even though 14 15 published core evidence to date is scarce. On the open coast, tidal current speeds were 16 17 18 probably not as great as today because of the generally steeper submarine slopes. 19 For Peer Review 20 • During the middle part of the transgression, when RSL was 50 to 30 m below present, there 21 22 will have been particularly strong shelf tidal currents (Ward et al., 2013). Further, cyclone 23 24 activity may have increased slightly through the Holocene because of the increasing mass of 25 26 shallow warm shelf waters (see Larcombe & Carter, 2004, for the argument and references) 27 28 but throughout the Holocene highstand there may also have been relatively little significant 29 30 change in cyclonic activity. 31 32 33 There are of course many uncertainties involved, but we conclude that there were significant 34 35 changes in the key drivers in the Barrow Island region during the transgression: i) a major increase 36 37 through the last 30 ka of the significance of shelf bathymetry, ii) lesser increases in tidal effects and 38 39 cyclones, and iii) a major relative change between drivers in the last 10 ka. Such changes would have 40 41 caused great changes in coastal configurations and associated coastal biomes. Along the coastline of 42 43 44 the present-day NW Shelf, the range of modern estuaries include tidal creeks (41%), wave- 45 46 dominated deltas (17%) and tide-dominated deltas (16%) (Ozcoasts, 2015), thus broadly 47 48 encompassing the lower central portion of the ternary diagram (Figure 4). Extrapolating this back in 49 50 time, we can postulate the likely dominant groups of estuarine environments. 51 52 53 Conditions before and at LGM (i.e. 30 - 20 ka) were probably fairly similar, encompassing mostly 54 55 strandplains, coastal lagoons and some tide-dominated estuaries, but changed thereafter, so that 56 57 58 Page 18 59 60 John Wiley & Sons Page 19 of 48 Geoarchaeology

Larcombe, Ward & Whitley – Physical sedimentary processes, sub-tropical coastlines, archaeological implications 1 2 3 during the period of rapid rise in RSL there may have been a greater representation of wave- 4 5 dominated estuaries, as part of a wider range of environments. At the mid-Holocene highstand, the 6 7 transition continued to produce the likely dominance of tide-dominated estuaries, as well as greater 8 9 river inflow. Present-day conditions are relatively similar, but there are drier conditions, and as the 10 11 shorelines have become less unstable, there is a little more relative wave influence. 12 13 14 Computer simulations of past coastal change in the Barrow Island region 15 16 Building from the above, we have combined data and analyses in ArcGIS 10.4.1 (ESRI 2017) with the 17 18 3D visualisation tools of Terragen 4.0 (Planetside Software, 2017) to explore and model the past 19 For Peer Review 20 21 coastal sedimentary environments. Terragen is a 3D modeling software package known as a 22 23 ‘scenery generator’ that uses a connected suite of modules for terrain, water, lighting, atmosphere, 24 25 shaders, objects, and cameras, to render high-resolution still images and animations taken from 26 27 specified locations. It thus renders photorealistic imagery, which conforms to our visual expectations 28 29 but is generated entirely by the software. Therefore, it is not an ‘artistic interpretation’ but a 30 31 computer-generated image based on specified parameters and rules. A summary of the main inputs 32 33 into the visualisations of the NW Shelf around Barrow Is. is given in Table 3, detailed in Whitley et al. 34 35 (2016) and Whitley (2017), and a simplified flow chart of the process is given in Figure 5. Generating 36 37 the visualisations involved converting both quantitative and qualitative data from various sources 38 39 into models of how changing climatic parameters play out across bathymetry and topography to 40 41 42 influence sea levels and vegetation patterns over time. Different input parameters create different 43 44 visualisations and some of these parameters are applied manually to the terrain models, while 45 46 several are simulated as autonomous ‘rules’ in Terragen. The simulation outputs are strictly 47 48 conjectural but are based on the best information currently available. Much of the underpinning 49 50 data is fragmentary or even contradictory, and is subject to issues of both scale and resolution. 51 52 Further, much of the information is ‘static’ in nature and does not reflect the dynamic nature of 53 54 most of the complex driving forces on coastal morphology. Thus, the resulting visualisations need to 55 56 57 58 Page 19 59 60 John Wiley & Sons Geoarchaeology Page 20 of 48

Larcombe, Ward & Whitley – Physical sedimentary processes, sub-tropical coastlines, archaeological implications 1 2 3 be seen as experimental simulations of different potential scenarios and not as ‘re-creations’ of past 4 5 events. We present both still images and an animation of past coastal evolution. 6 7 8 i. Animation of ‘shoreline’ evolution 9 10 First, we present an animation representing the period 65 ka to the present day, illustrating the 11 12 coastal evolution with and without the autonomous hydrodynamic effects ‘rules’ of coastal erosion, 13 14 fluvial sediment contributions and wave diffraction (Figure 6a – c for still images, and for the full 15 16 animation see Supplementary Information). Put simply, the hydrodynamic effects rules act to 17 18 manipulate the ‘static’ bathymetry, based on simple parameters tied to the climatic conditions. 19 For Peer Review 20 21 Thus, the comparison is intended to simulate how the visuals might change given the different 22 23 condition mentioned above. 24 25 26 Viewed from the low-earth orbit perspective, local-level hydrodynamic effects make little difference 27 28 to the overall simulation of coastal change over the past 65 ka, beyond generating some 29 30 morphological artifacts, such as simulated coastal sand ridges or estuaries, as a result of applying 31 32 these experimental processes. Principally this is because (a) the angle of the upper continental slope 33 34 and outer shelf is relatively steep, so that the potential for altering some of the driving 35 36 hydrodynamic effects is low, and probably (b) it is not possible to incorporate, at this regional scale, 37 38 the nature of the physical connections between the various sub-regional sedimentary systems. An 39 40 example of the influence of such regional sedimentary connections is the central Great Barrier Reef 41 42 shelf, wherein an ambient shore- and shelf-parallel sediment transport regime passes sediment 43 44 through and between a series of north-facing inner-shelf embayments (Belperio, 1983; Belperio & 45 46 47 Searle, 1988) rich in coastal resources. Here, the nature of Holocene coastal evolution has been 48 49 greatly influenced by episodes of avulsion on the Burdekin River, which as described above has 50 51 generated pulses of sediment accumulation to switch between adjacent embayments (Lewis et al., 52 53 2014). There are likely to have been similar links between different parts of the NW Shelf coastline, 54 55 but the paucity of dated marine shelf cores means that detailed information on such past changes is 56 57 58 Page 20 59 60 John Wiley & Sons Page 21 of 48 Geoarchaeology

Larcombe, Ward & Whitley – Physical sedimentary processes, sub-tropical coastlines, archaeological implications 1 2 3 absent at present, so that such variations are not able to be reproduced for the NW Shelf 4 5 simulations. This is an example of where we might be able to create sophisticated experimental 6 7 hydrodynamic rules, but their application would be heavily determined by the resolution of the data 8 9 we have and our knowledge regarding how those dynamics apply in very specific local conditions. In 10 11 other words, there is a very powerful tool, but a decided lack of detailed data to drive it at present. 12 13 14 At a regional scale, such visualisations can help provide an approximation of the position of the 15 16 coastline for any particular period and/or location of interest, such as around the earliest period of 17 18 human occupation from around 65 – 50 ka. However, we consider the real interest in such 19 For Peer Review 20 visualisations are at the local scale (e.g. individual embayments or estuaries, i.e. local sedimentary 21 22 ‘units’) because it is at these scales that people use and occupy landscapes, and at which physical 23 24 25 processes impact archaeological site preservation (Johnson, 2002). At the local scale, even simply 26 27 modifying the hydrodynamic effects based on regional trends in climate (compiled from various 28 29 specific and qualitative sources, Table 3) can make a significant difference to the coastline, 30 31 particularly in shallow parts where sediments in the littoral zone are more mobile (Figure 6a – c, see 32 33 Supplementary Information for full animation). Archaeologically, such shallow-water sedimentary 34 35 effects are likely to be very important in controlling the location and nature of resources, such as 36 37 those associated with protected embayments, or, in contrast, macrotidal estuaries or strandplains 38 39 (c.f. Figure 4). 40 41 42 ii. Still images 43 44 We present some still images of what the Barrow Island area might have looked like at 8.2 ka had its 45 46 47 coastal sedimentary environments been controlled overwhelmingly by a single particular physical 48 49 driver (Figure 7). We have chosen to illustrate these scenarios using three separate and distinct 50 51 drivers: fluvial sediment supply, ambient waves (i.e. excluding cyclonic or storm waves) and tides. 52 53 Each still image was manually generated by using expert judgment to displace a Terragen terrain 54 55 based on modern bathymetry, by adding appropriate coastal sedimentary bodies and features. The 56 57 58 Page 21 59 60 John Wiley & Sons Geoarchaeology Page 22 of 48

Larcombe, Ward & Whitley – Physical sedimentary processes, sub-tropical coastlines, archaeological implications 1 2 3 animations used autonomous processes based on elevation, slope, and climatic rules to simulate 4 5 experimental hydrodynamic effects and arrived at similar outcomes. The manual applications work 6 7 in a similar way, but we can have more immediate control over the effects based on slightly 8 9 modifying local conditions, shaders, surfaces, and vegetation patterns. This is another form of 10 11 experimentation, and it allows application of some effects that are not currently reducible to rule- 12 13 based scenarios. 14 15 16 In the resulting ‘fluvial’ scenario (Figure 7a), river systems occur to the east and south of Barrow Is. 17 18 each with a narrow tidal inlet to the sea. As is typical of rivers in NW Australia, these rivers would be 19 For Peer Review 20 shallow, ephemeral and sandy, with episodic terrigenous sediment supply to the coast. Here, their 21 22 catchments would be of limited size, and their wide seaward entrance would be flanked by a narrow 23 24 25 intertidal zone, and exposed bedrock and rocky reef. Marine conditions would be likely to prevail 26 27 throughout much of the lower river system for long periods. 28 29 30 In the ‘wave-dominated’ scenario (Figure 7b) we depict a coastal lagoon developed through the 31 32 presence of a sandy barrier (Harris & Heap, 2003). Such back-barrier environments are common of 33 34 wave-dominated coasts (Masselink et al., 2011). The lagoon entrance would be intermittently open 35 36 to seaward exchange, through a very narrow entrance, and the lagoon represents a regime of low 37 38 wave and tidal energy. Episodic storms and cyclones might breach the barrier at times, resulting in a 39 40 more saline environment, at least until the barrier reforms. The timing, duration and volumetric of 41 42 direct water exchange between the ocean and the coastal lagoon, and/or through the barrier itself, 43 44 would help control the marine resources available. Seagrass beds, saltmarsh and floodplain species 45 46 might be supported, but extensive stands of mangroves are unlikely, due to the lack of a constant 47 48 49 connection with the open ocean (Roy et al., 2001). 50 51 In the ‘tide-dominated’ scenario (Figure 7c), there are funnel-shaped estuaries within which there 52 53 would be repeated sediment resuspension and through which there would be only minimal delivery 54 55 56 of freshwater and terrestrial sediment to the coast. Large areas of estuarine mangroves would 57 58 Page 22 59 60 John Wiley & Sons Page 23 of 48 Geoarchaeology

Larcombe, Ward & Whitley – Physical sedimentary processes, sub-tropical coastlines, archaeological implications 1 2 3 occur, flanked by saltflats or saltmarsh (c.f. Semeniuk, 1982). Freshwater wetlands and floodplain 4 5 vegetation (such as Melaleuca spp.) might occur above the influence of most (but not all) tides (Ryan 6 7 et al., 2003). 8 9 10 iii. Which is the correct model? 11 12 “It is correct?” is a very common question. Of course, none of these visualisations or still images 13 14 correctly represents the actual past development of the Barrow Island region, because at present 15 16 there is insufficient knowledge of the past changes in the controlling variables. It is therefore 17 18 important to ask what palaeo-environmental information exists or is needed to help determine 19 For Peer Review 20 21 which scenario, or aspects of them, might be i) most accurate and ii) most relevant to archaeology. 22 23 Such information might include accurate bathymetry (e.g. LIDAR), retrodictive tidal-modelling, 24 25 evidence for past groundwater levels, offshore sedimentary records and benthic shelf habitats, 26 27 microfossil records (especially for mangroves, freshwater or brackish lagoons, etc.), proxies for 28 29 rainfall, temperatures, and so on, as well as archaeological and associated data. The same suite of 30 31 needs are also required to improve confidence in ongoing retrodictive reconstructions of coastal 32 33 change, biomes and associated interpretations of demography during the LGM and early Holocene 34 35 (e.g. Guesdes et al., 2016; Williams et al., in press). 36 37 38 Whilst high-resolution LIDAR data may not necessarily clarify things because it implicitly assumes 39 40 that the sea-floor now represents that of the past, it may usefully illustrate features of past and 41 42 present sediment transport regimes, such as incised rivers, indurated or cemented coastal dunes 43 44 and scour. Further, some relevant aspects may never be known to a satisfactory extent. 45 46 47 Archaeological records, for example, are generally limited by the poor preservation conditions, on 48 49 Barrow Island and in NW Australia generally. On the other hand, visualisations may simulate the 50 51 evolution of relevant physical features that might subsequently have been destroyed in the later 52 53 stages of sea-level rise. On the Rowley Shelf, for example, submerged Pleistocene terraces above 54 55 56 57 58 Page 23 59 60 John Wiley & Sons Geoarchaeology Page 24 of 48

Larcombe, Ward & Whitley – Physical sedimentary processes, sub-tropical coastlines, archaeological implications 1 2 3 the LGM strandline (located at ~120-125 m depth) appear to have been obliterated (Wilson, 2013: 4 5 28). 6 7 8 Therefore, the information presently available provides some answers but not others. The 9 10 contextual information derived from Boodie Cave on the western side of Barrow Island indicates 11 12 that for much of the late Pleistocene and early Holocene (Ward et al. 2015; Veth et al., 2017) there 13 14 was a diverse coastal environment with both marine and freshwater influences. As outlined above, a 15 16 wave-dominated system in the area, including a back-barrier lagoon, might offer a range of brackish 17 18 to marine resources but extensive mangroves are unlikely, because of the likely dominance of sandy 19 For Peer Review 20 sediments, a steep foreshore and a relatively mobile intertidal zone. In contrast, a tide-dominated 21 22 coastal system has an extensive intertidal zone and the potential for large areas of productive 23 24 25 mangrove forests, which arguably fits better with the available information. However, in terms of 26 27 defining environment and resource availability, a range of other factors may need to be taken into 28 29 account in the palaeolandscape simulations, such as freshwater seepage (e.g. Mathews et al., 2011), 30 31 the effects of oceanic currents such as the Leeuwin Current (Wywroll et al., 2009) and/or the effects 32 33 of biogeography on the dispersal of plant and animal species (Wilson, 2013). During periods of low 34 35 sea level, for example, the extremely steep and narrow continental shelf around the Montebello 36 37 Islands may have virtually isolated a western “embayment” from another embayment further east 38 39 (Wilson, 2013:318). Hence, more specific (local) data are needed regarding physical processes, 40 41 sedimentary context (e.g. Ward et al., 2017) and biogeography (Wilson, 2013) to help refine the 42 43 44 visualisations for key periods in the past and to permit the best interpretation of the archaeological 45 46 data. We contend that this conclusion also applies to other coastlines of the world, where 47 48 archaeological evidence also implies major changes in coastal environments and resource use (e.g. 49 50 d’Alpoim Guides et al. 2016; Gilbertson et al., 2017; Williams et al., in press). Ultimately, however, 51 52 such visualisations are still subjective and should not be taken to be any more inherently accurate 53 54 than any other archaeological ideas, no matter how much detail or quantification they might contain 55 56 (Whitley, 2017:11). 57 58 Page 24 59 60 John Wiley & Sons Page 25 of 48 Geoarchaeology

Larcombe, Ward & Whitley – Physical sedimentary processes, sub-tropical coastlines, archaeological implications 1 2 3 In summary, the above simulations provide the means to ask questions and develop testable 4 5 hypotheses rather than provide solid answers. Such questions may relate to: i) changing 6 7 configurations and productivity of the shoreline environment available for use by early Aboriginal 8 9 occupants, before and during the Post-Glacial transition, and including how sensitive the 10 11 development of the coastal environment was to episodic events or changing coastal configurations, 12 13 ii) the likely location and preservation of Late Pleistocene and early Holocene submerged 14 15 archaeological sites along different parts of the continental shelf, and iii) their links with onshore 16 17 archaeological records, including the significance of past physical changes in placing existing well- 18 19 For Peer Review 20 documented terrestrial and coastal sites into a broader physical context. No single simulation (or 21 22 driver) may be correct, particularly for the Pilbara coast, which is relatively variable and contains 23 24 wave-dominated barrier-island shores, ria-archipelago rocky shores, and tidal creek systems (Wilson, 25 26 2013:208). 27 28 29 Unfortunately, but importantly, such variability means that it may be highly speculative to 30 31 extrapolate the findings of a small number of coastal archaeological sites, however well 32 33 documented, to the broader region. Evidence is needed to help establish whether these or any 34 35 other archaeological observations are typical or atypical of the region and to help test conceptual 36 37 patterns of human use and dispersal. As noted above, and emphasised by Whitley (2017:11), 38 39 computer simulations used with appropriate physical processes can help devise geospatial 40 41 experiments, which can help generate hypotheses to test using fieldwork. Together, these can 42 43 44 clarify our understanding of such issues. 45 46 47 48 CONCLUSIONS 49 50 Focusing on sub-tropical and tropical continental shelves and coastlines, this work has described the 51 52 range of drivers of physical sedimentary change in such regions. A series of case studies of sub- 53 54 tropical and tropical continental shelves and coastlines has indicated the range and complexity of 55 56 57 58 Page 25 59 60 John Wiley & Sons Geoarchaeology Page 26 of 48

Larcombe, Ward & Whitley – Physical sedimentary processes, sub-tropical coastlines, archaeological implications 1 2 3 sedimentary environments and geoarchaeological implications arising from the results of different 4 5 dominant drivers of physical change over the last 50,000 years or so. 6 7 8 Likely changes in these physical drivers change though time and the archaeological relevance have 9 10 been described, using the Barrow Island section of Australia’s NW Shelf as a case study. Here, and in 11 12 general on Australia’s northern shelves, it is highly unlikely that there is widespread preservation of 13 14 past coastal archaeology on the modern continental shelf, but there some relevant exceptions. 15 16 17 The computer package Terragen has be applied to the past NW Shelf system to help generate and 18 19 visualise analogues (Whitley,For 2017), Peer and it is a flexible Review experimental geoarchaeological tool which 20 21 allows hypothesis generation through illustrating the possible range of past coastal sedimentary 22 23 environments. It can provide, for example, the means to develop a variety of model scenarios, at a 24 25 range of temporal and spatial scales, which can assist with hypothesis generation. However, 26 27 because of the paucity of detailed core data from the marine environment, and other data to help 28 29 30 provide greater coupling of pattern, process and scale, there is limited opportunity at present for its 31 32 direct use in hypothesis testing. 33 34 35 There are a wide range of physical sedimentary processes and changes through time that need to be 36 37 considered when designing archaeological prospection on sub-tropical and tropical continental 38 39 shelves, and when interpreting collected data from the shelf environments, from islands and the 40 41 mainland. Unfortunately, the variability means that it may be highly speculative at present to 42 43 extrapolate findings from a few well-documented coastal archaeological sites to the broader region. 44 45 The general geoarchaeological lessons are broadly applicable to a wide range of coastal and marine 46 47 environments. 48 49 50 51 ACKNOWLEDGMENTS 52 53 RPS MetOcean funded PL’s contributions to this research. IW is funded by Australian Research 54 55 56 Council grant DP170100812. IW wishes to thank Flinders University and the Royal Society for funding 57 58 Page 26 59 60 John Wiley & Sons Page 27 of 48 Geoarchaeology

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Larcombe, Ward & Whitley – Physical sedimentary processes, sub-tropical coastlines, archaeological implications 1 2 3 Planetside Software, (2017) Terragen 4.1: http://planetside.co.uk/ 4 5 Przeslawski, R., Daniell, J., Anderson, T., Barrie, J.V., Heap, A., Hughes, M., Li, J., Potter, A., Radke, L., 6 Siwabessy, J., Tran, M., Whiteway, T., & Nichol, S. (2011). Seabed Habitats and Hazards of the Joseph 7 Bonaparte Gulf and Timor Sea, Northern Australia. Canberra: Geoscience Australia Record 2011/40. 8 9 Reeves, J.M., Barrows, T.T., Cohen, T.J., Kiem, A.S., Bostock, H.C., Fitzsimmons, K.E., Jansen, J.D., 10 Kemph, J., Krause, C., Petherick, L., Phipps, S.J., & OZ-INTIMATE Members (2013). Climate Variability 11 12 over the Last 35,000 years Recorded in Marine and Terrestrial Archives in the Australian Region: an 13 OZ-INTIMATE Compilation. Quaternary Science Reviews, 74, 21–34. 14 15 Richardson, L., Mathews, E. & Heap, A. (2005). Geomorphology and Sedimentology of the South 16 Western Planning Area of Australia - Review and synthesis of relevant literature in support of 17 Regional Marine Planning. Geoscience Australia, Record 2005/17. 124pp. 18 19 Ross, P.J. (2009) NgarrindjeriFor fish traps Peer of the lower Review Murray Lakes and Norther Coorong Estuary, 20 South Australia. (Masters thesis) Adelaide: Flinders University, Dept. of Archaeology. 21 22 Rowland, M.J. & Ulm, S. (2012) Key issues in the conservation of the Australian coastal 23 24 archaeological record: natural and human impacts. Journal of Coastal Conservation, 14(1), 159-171 25 26 Roy, P. S., Williams, R. J., Jones, A. R., Yassini, R., Gibbs, P. J., Coates, B., West, R. J., Scanes, P. R., 27 Hudson, J. P., & Nichol, S. (2001). Structure and function of southeast Australian estuaries. Estuarine, 28 Coastal and Shelf Science, 53, 351-384. 29 30 Rudnick, D.L., & Ferrari, R. (1999) Compensation of horizontal temperature and salinity gradients in 31 the ocean mixed layer. Science 283, 526-529. 32 33 Russell, S., Sullivan, C.A., & Reichelt-Brushett, A.J. (2015). Aboriginal consumption of estuarine food 34 resources and potential implications for health through trace metal exposure; A study in 35 36 Gumbaynggirr Country, Australia. PLoS ONE 10(6): e0130689. doi:10.1371/journal.pone.0130689 37 38 Ryan, D.A., Heap, A.D., Radke, L., & Heggie, D.T. (2003). Conceptual models of Australia’s estuaries 39 and coastal waterways applications for coastal resource management. Geoscience Australia Record 40 2003/09, 145 pp. 41 42 Shore Coastal (2015) Shire of Augusta Margaret River. Margaret River Coastal Hazard Risk 43 Management and Adaptation Plan for Shire of Augusta Margaret River. Report to Shire of Augusta 44 Margaret River. 87 pp. 45 46 Siddall, M., Rohling, E.J., Almogi-Labin, A., Hemleben, Ch., Meischner, D., Schmelzer, I., & Smeed, 47 48 D.A. (2003). Sea-level Fluctuations during the Last Glacial Cycle. Nature 423, 853–858. 49 50 Stanley, J-D., & Clemente, P.L. (2017) Increased Land Subsidence and Sea-Level Rise are Submerging 51 Egypt’s Nile Delta Coastal Margin. GSA Today 27, 4-11. 52 53 Stul, T., Gozzard, J.R., Eliot, I.G., & Eliot, M.J. (2014). Coastal Sediment Cells for the Pilbara Region 54 between Giralia and Beebingarra Creek, Western Australia. Report prepared by Seashore 55 56 57 58 Page 34 59 60 John Wiley & Sons Page 35 of 48 Geoarchaeology

Larcombe, Ward & Whitley – Physical sedimentary processes, sub-tropical coastlines, archaeological implications 1 2 3 Engineering Pty Ltd and Geological Survey of Western Australia for the Western Australian 4 Department of Transport, Fremantle. 5 6 Tveskov, M.A., & Erlandson, J.M. (2003) The Haynes Inlet weirs: estuarine fishing and archaeological 7 site visibility on the southern Cascadia coast. Journal of Archaeological Science, 30(8), 1023-1035 8 9 Ulm, S. (2011). Reassessing marine fishery intensification in Southeast Queensland. Queensland 10 Archaeological Research, 13, 79-96. 11 12 Van der Kaars, S. (1991) Palynology of eastern Indonesian marine piston-cores: a Late Quaternary 13 14 vegetational and climatic record for Australasia. Palaeogeography, Palaeoclimatology, 15 Palaeoecology, 85(3-4), 239-302. 16 17 Veth, P., Ward, I., & Manne, T. (2016). Coastal Feasts: A Pleistocene Antiquity for Resource 18 Abundance in the Maritime Deserts of North West Australia? The Journal of Island and Coastal 19 Archaeology, 1-16. For Peer Review 20 21 Veth, P., Ward, I., Manne, T., Ulm, S., Ditchfield, K., Dortch, J., Hook, F., Petchey. F., Hogg, A., 22 Questiaux, D., Demuro, M., Arnold, L., Spooner, N., Levchenko, V., Skippington, J., Byrne, C., Basgall, 23 24 M., Zeanah, D., Belton, D., Helmholz, P., Bajkan, S., Bailey, R., Placzek, C., & Kendrick, P. (2017). Early 25 human occupation of a maritime desert, Barrow Island, North-West Australia. Quaternary Science 26 Reviews, 168, 19–29. 27 28 Waelbroeck, C., Labeyrie, L., Michel, E., Duplessy, J.C., McManus, J.F., Lambeck, K., Balbona, E., & 29 Labracherie, M. 2002. Sea Level and Deep-water Temperature Changes Derived from Benthic 30 Foraminifera Isotopic Records. Quaternary Science Reviews, 21, 295–305. 31 32 Ward, I., & Larcombe, P. (2008). Determining the preservation rating of submerged archaeology in 33 34 the Post-Glacial southern North Sea: a first-order geomorphological approach. Environmental 35 Archaeology 13 (1), 59-83. 36 37 Ward, I., & Veth, P. (2017). To the Islands: The archaeology of the archipelagoes of NW Australia and 38 its implications for drowned cultural landscapes. In G. Bailey, J, Harff, & D. Sakellariou (Eds.) Under 39 the Sea: Archaeology and Palaeolandscapes. Coastal Research Library, vol 20. Springer, Cham. 40 Retriavable from https://doi.org/10.1007/978-3-319-53160-1_24 41 42 Ward, I., Veth, P., & Manne, T. (2014) To the islands born: the research potential of submerged 43 44 landscapes and human habitation sites from the islands of NW Australia. Geological Society, London, 45 Special Publications, 411, 251-263. 46 47 Ward, I., Larcombe, P., Mulvaney, K., & Fandry, C.A. (2013). The potential for discovery of new 48 submerged archaeological sites near the Dampier Archipelago, Western Australia. Quaternary 49 International, 308-309, 216 – 229 50 51 Ward. I., Larcombe, P., & Veth, P. (2015). A new model for coastal resource productivity and sea 52 level change: The role of physical sedimentary processes in assessing the archaeological potential of 53 54 submerged landscapes from the northwest Australian coastline. Geoarchaeology, 30, 19 – 31. 55 56 57 58 Page 35 59 60 John Wiley & Sons Geoarchaeology Page 36 of 48

Larcombe, Ward & Whitley – Physical sedimentary processes, sub-tropical coastlines, archaeological implications 1 2 3 Ward, I., Larcombe, P., Carson, A., & Lane, A. (2016) Archaeological assessment of coastal and 4 marine development sites: case study from James Price Point, Western Australia. Journal of the 5 Royal Society of Western Australia, 99(2), 31 – 46. 6 7 Ward, I., Merigot, K., & McInnes, B. (2017) Application of quantitative mineralogical analysis in 8 archaeological micromorphology: a case study from Barrow Is., Western Australia. J. Arch. Methods 9 10 and Theory. Retrievable from DOI 10.1007/s10816-017-9330-6. 11 12 Whitley, T.G. (2017). Geospatial analysis as experimental archaeology. Journal of Archaeological 13 Science, Retrievable from https://doi.org/10.1016/j.jas.2017.05.008 14 15 Whitley, T.G., Berry, M., & Clayton Martinez, L. (2016). Re-Visualizing the Drowned Landscapes of 16 Murujuga and the Dampier Archipelago, Western Australia. Paper presented at the 2016 Australian 17 Archaeological Association Conference, Terrigal, NSW. Full version available at: 18 https://www.academia.edu/35381795/Visualizing_125_000_Years_of_Environmental_and_Landsca 19 For Peer Review 20 pe_Change_in_NW_Australia and 21 https://www.researchgate.net/profile/Thomas_Whitley/publications?pubType=workingPaper 22 23 Whitley, T.G. & Dortch, J. (2017). Murujuga landscapes: visualising the transition from the Dampier 24 Range to the Dampier Archipelago. Paper for the 2017 Australian Archaeological Association 25 Conference, Melbourne, VIC. 26 27 Williams, A.M., Ulm, S., Cook, A.R., Langley, M.C., & Collard, M. (2013) Human Refugia in Australia 28 During the Last Glacial Maximum and Terminal Pleistocene: a Geospatial Analysis of the 25–12 ka 29 Australian Archaeological Record. Journal of Archaeological Science 40, 4612–4625. 30 31 Williams, A.N., Veth, P., Steffen, W., Ulm, S., Turney, C.S.M., Phipps, S., Smith, M., & Reeves, J. 32 (2015). A Continental Narrative: Human Settlement Patterns and Australasian Climate Change over 33 34 the Last 35,000 Years. Quaternary Science Reviews 123, 91–112. 35 36 Williams, A.N., Ulm, S., Sapienza, T., Lewis, S., Turney, C.S.M. (in press) Sea-level change and 37 demography during the last glacial termination and early Holocene across the Australian continent. 38 Quaternary Science Reviews, https://doi.org/10.1016/j.quascirev.2017.11.030 39 40 Wilson, B. (2013). The biogeography of the Australian North West Shelf: environmental change and 41 life's response. Elsevier. 42 43 Woodroffe, C.D. & Murray-Wallace, C.V. (2014). Quaternary Sea-Level Changes: A Global 44 Perspective. Cambridge: Cambridge University Press. 45 46 Wyrwoll, K. (1979). Late Quaternary climates of Western Australia: Evidence and mechanism. Journal 47 48 of the Royal Society of Western Australia 62, 129–142. 49 50 Wyrwoll, K.-H., & Miller, G. (2001). Initiation of the Australian summer monsoon 14,000 years ago. 51 Quaternary International 83-85, 119-128. 52 53 Wyrwoll, K.-H., Greenstein, B.J., Kendrick, G.W., & Chen, G.S. (2009) The palaeoceanography of the 54 Leeuwin Current: implications for a future world. J. Royal Society of Western Australia 92, 37-51. 55 56 57 58 Page 36 59 60 John Wiley & Sons Page 37 of 48 Geoarchaeology

Larcombe, Ward & Whitley – Physical sedimentary processes, sub-tropical coastlines, archaeological implications 1 2 3 Yokoyama, Y., De Deckker, P., Lambeck, K., Johnston, P., & Fifield, L.K. (2001). Sea level at the Last 4 Glacial Maximum: Evidence from Northwestern Australia to Constrain Ice Volumes for Oxygen 5 Isotope Stage 2. Palaeogeography, Palaeoclimatology, Palaeoecology, 165, 281–297. 6 7 8 9 10 11

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Larcombe, Ward & Whitley – Physical sedimentary processes, sub-tropical coastlines, archaeological implications 1 2 3 Tables 4 5 6 Table 1 Mean recurrence intervals in various coastal and shelf sedimentary environments of the 7 central GBR between major sedimentary events, associated with cyclones, & general 8 trends of net accumulation (+) erosion (–) or variable (±) (modified after Larcombe, 2006. 9 Data sources: Hopley, 1982; Gagan et al., 1988; Nott & Hayne, 2001; Larcombe & Carter 10 2004; Liu et al., 2014). 11 12 Sedimentary environment & type Mean recurrence interval Inferred Long-term general sedimentary 13 of data (yrs) in the stratigraphy interval (yrs) tendency. Accumulation (+ve), 14 Erosion (–ve), Variable (±) and 15 main sedimentary features 16 Coastline & island perimeter 180-280 36 - 93 ± ve 17 (Beach ridges & Chenier ridges) 18 Beach erosion, formation of chenier ridges at muddy costlines 19 For Peer Reviewand beach ridges at sandy coastline 20 21 Inner shelf seabed (shelbeds) 120-150 24 - 50 +ve 22 a) Receive sediment from rivers 23 and from erosion on middle shelf 24 b) Unmix bed sediment, transport it 25 along shelf, creating large dunes 26 of shelly gravel and graded beds 27 Middle shelf seabed (shellbeds) 360-600 72 - 200 -ve 28 29 As inner shelf plus formation of sand/gravel ribbons and 30 longitudinal furrows 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 Page 38 59 60 John Wiley & Sons . . et alet . (2003) . (2005),. et al et . (2013). . (2015) et al et

) et alet et al et 4 4 2 2 3 2 4 4 0,0 2015 Modern moisture , 2014,, Ridd, Larcombe & . (2001),. Siddall . (2004), Dix (2013 & 2015) Brewer et et Brewer2007 al. et al et et al et et al et . (2008),References in Ward of the NW Shelf. RLS = relative relative = RLS Shelf. NW theof references in references Ward et alet References in Ward James Lees Lees (1992a),Ringis (2000),& Clarke See Refs3See inTable (“Temperature and Pearce 2003,Pearce et al. Heyward et 2006, al. Larcombe Larcombe Yokoyama Baker Baker

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rise rise Larcombe, Ward & Whitley – Physical sedimentary processes, sub-tropical coastlines, archaeological implications implications archaeological coastlines, sub-tropical processes, sedimentary Physical – Whitley & Ward Larcombe, Page 39 Page periodof rapid RLS Middle ofMiddle Geoarchaeology John Wiley & Sons LGM LGM RSL at RSL

2 3 3 2 3 1 4 2 2 3 4 3 3 3 3 3 3 3 30, -9030, -110 20, For -60 10, Peer Review References References References References References References References level) level) elevance ofelevance timing Pre-LGM Lowest R Approximate(ka) Timing& relative sea levelrelative(m sea modern sea level, LGM = last glacial maximum. Data are illustrated in Fig. 2. in Fig. areillustrated Data maximum. glacial =last LGM level, sea R 1. Shelf bathymetry 2. sediment deliveryFluvial 3. availability Shelf sediment 4. (incl. seasonal Waves winds) 5. (& range Tidal flowdirections) 6. (& Cyclones their effects) Table 2 Table evolution the in points critical with associated =most), 4 to least, (1 = time through driver each of rating elative Driver

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Larcombe, Ward & Whitley – Physical sedimentary processes, sub-tropical coastlines, archaeological implications 1 2 3 4 5 Table 3 Main inputs into computer simulations for the NW Shelf around Barrow Is. (see also Whitley 6 et al., 2016; 2017). 7 8 Model element Input Data Source/description Resolution 9 1.Terrain model Bathymetry Geoscience Australia (2009) 250 m 10 Bathymetry Geoscience Australia (2012) 50 m 11 Hydrographic AUS57 (Dampier Archipelago), 1:75,000 12 charts AUS741 (Dampier Archipelago), and 1:150,000 13 AUS742 (Rosemary Is. to Barrow Is.) 1:300,000 14 Topography Geoscience Australia (2011) 30 m 15 Hydrology Australian Bureau of Meteorology 30 m 16 (ABM 2015) 17 2. Palaeoenvironment Sea level Yokoyama et al. (2001), Waelbroeck ~ 10,000 to 18 model et al. (2002), Siddall et al. (2003), and 1000 yrs 19 For PeerLambeck Review et al. (2014) 20 21 Temperature/ Wyrwoll and Miller (2001) ; 22 moisture Fitzsimmons et al. (2013); Hesse et 23 al. (2004); Johnson et al. (1999); 24 Reeves et al. (2013); Williams et al. 25 (2013; 2015) 26 3. 3D visualisations Terrain dataset GIS-corrected terrain model 30 m 27 Water/sea level Set at 100 year increments 100 yrs 28 Lighting/ Set at 300º N at an elevation of 12º varies 29 Atmosphere above the horizon 30 Vegetation Includes spinifex, acacia-dominant varies 31 shrublands, lowland eucalypt forest, 32 semi-open dry woodlands, coastal 33 tropical forest, riparian woodlands, 34 mangroves and marine vegetation 35 Surface Includes littoral zone marine sands, varies 36 37 sediments tidal flats, beach sands, and interior 38 sand dunes 39 Hydrodynamic Includes simulations of coastal varies 40 effects erosion, fluvial sediment 41 contributions, and wave diffraction 42 43 44 45

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Larcombe, Ward & Whitley – Physical sedimentary processes, sub-tropical coastlines, archaeological implications 1 2 3 List of Figures 4 5 6 Figure 1 The ternary diagram of Dalrymple et al. (1992) and Boyd et al. (1992) which 7 discriminates coastal environments across three - the first axis representing wave, tidal 8 and fluvial processes (redrawn from 9 10 http://www.ozcoasts.gov.au/conceptual_mods/introduction.jsp). The points of the 11 diagram represent ‘estuarine’ geomorphologies produced by the overwhelming 12 dominance of each of the three drivers: waves, tides and rivers (read terrigenous 13 sediment supply). (WDD = wave-dominated delta, TDD = tide-dominated delta). 14 15 Figure 2 Global examples of coastlines dominated by different drivers of change, including (a) 16 17 shelf bathymetry, (b) fluvial sediment delivery, (c) shelf sediment availability, (d) waves 18 (including seasonal winds), (e) tidal range (and flow directions), (f) tidal range (Barrow 19 Is./DampierFor Archipelago), Peer and (g) cyclones/hurricanes/typhoons Review (and their effects). 20 Bathymetry sourced from navionics (https://webapp.navionics.com/). 21 22 Figure 3 Relative importance rating of each driver in controlling coastal sedimentary 23 environments, for the Barrow Is. region over the last 30 ka. 24 25 Figure 4 Postulated regions, plotted on Figure 1, of the coastal sedimentary environments of the 26 27 Barrow Island region of the NW Shelf at the present day and at 5 ka, 10 ka, 30 -20 ka. 28 (Note episodic events are not included on this figure.) 29 30 Figure 5 Flowchart (simplified) of the key inputs, processes and connections made regarding 31 ArcGIS and Terragen in generating the visualisations. 32 33 Figure 6 Comparative visualisations around Barrow Is. at different times in the past (a) 50,000 34 yrs BP, (b) 8200 yrs BP and (c) 4100 years BP, without (left) and with (right) the 35 hydrodynamic effects. 36 37 Figure 7 Still images of visualisations around the area south of Barrow Island from an oblique 38 39 aerial perspective (~ 17,000 m) around 8200 years BP, with the different dominant 40 driver of (a) fluvial sediment supply, (b) ambient waves and (c) tides. The ‘true’ scenario 41 is likely to be a combination of these. Pink area on a) indicates the extent of the 42 modern islands for reference. (Note that these captions are a correction to Whitley, 43 2017). 44 45

46 47 Supplementary Animation 48 49 50 51 52 53 54 55 56 57 58 Page 41 59 60 John Wiley & Sons Geoarchaeology Page 42 of 48

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 For Peer Review 20 21 22 23 24 25 26 27 28 29 30 31 32 Figure 1 The ternary diagram of Dalrymple et al. (1992) and Boyd et al. (1992) which discriminates coastal 33 environments across three - the first axis representing wave, tidal and fluvial processes (redrawn 34 from http://www.ozcoasts.gov.au/conceptual_mods/introduction.jsp). The points of the diagram represent 35 ‘estuarine’ geomorphologies produced by the overwhelming dominance of each of the three drivers: waves, 36 tides and rivers (the latter taken as terrigenous sediment supply in this context). 37 38 89x70mm (300 x 300 DPI) 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 John Wiley & Sons Page 43 of 48 Geoarchaeology

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 For Peer Review 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 Global examples of coastlines dominated by different drivers of change, including (a) shelf bathymetry, (b) 46 fluvial sediment delivery, (c) shelf sediment availability, (d) waves (including seasonal winds), (e) tidal 47 range (and flow directions), (f) tidal range (Barrow Is./Dampier Archipelago), and (g) 48 cyclones/hurricanes/typhoons (and their effects). Bathymetry used with permission from Navionics 49 (https://webapp.navionics.com/). 50 190x270mm (96 x 96 DPI) 51 52 53 54 55 56 57 58 59 60 John Wiley & Sons Geoarchaeology Page 44 of 48

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 For Peer Review 20 21 22 23 24 25 26 27 28 29 30 31 Figure 3 Relative importance rating of each driver in controlling coastal sedimentary environments, for the 32 Barrow Is. region over the last 30 ka. 33 34 198x150mm (96 x 96 DPI) 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 John Wiley & Sons Page 45 of 48 Geoarchaeology

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 For Peer Review 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 Postulated regions, plotted on Figure 1, of the coastal sedimentary environments of the Barrow Island region 46 of the NWS at the present day and at 5 ky BP, 10 ky BP, 30 -20 ky BP. (Note episodic events are not 47 included on this figure.) 48 49 245x559mm (300 x 300 DPI) 50 51 52 53 54 55 56 57 58 59 60 John Wiley & Sons Geoarchaeology Page 46 of 48

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 For Peer Review 20 21 22 23 24 25 26 Figure 5 Flowchart (simplified) of the key inputs, processes and connections made regarding ArcGIS and 27 Terragen in generating the visualisations. 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 John Wiley & Sons Page 47 of 48 Geoarchaeology

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 For Peer Review 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 Comparative visualisations around Barrow Is. at different times in the past (a) 50,000 yrs BP, (b) 8200 yrs 38 BP and (c) 4100 years BP, with and without the hydrodynamic effects. 39 40 168x159mm (300 x 300 DPI) 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 John Wiley & Sons Geoarchaeology Page 48 of 48

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 For Peer Review 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 Figure 6 Static visualisations around the area south of Barrow Island from an oblique aerial perspective (~ 46 17,000 m) around 8200 years BP, with the different dominant driver of (a) fluvial sediment supply, (b) 47 ambient waves and (c) tides. The ‘true’ scenario is likely to be a combination of these. Pink area on a) 48 indicates extent of modern island. (Note that these captions are a correction to Whitley, 2017). 49 50 259x532mm (300 x 300 DPI) 51 52 53 54 55 56 57 58 59 60 John Wiley & Sons