Geographical Review of Japan Vol. 59 (Ser. B), No. 1, 55-67, 1986 Geomorphology and Quaternary History of the Australian Continental Dunefields R. J. WASSON This summary paper forms part of a Japanese-Australian research project on human impact in the Australian semi-arid and arid zone. The dunefields are introduced in their various geologic and geomorphic settings and the sources and types of dune sands are then examined. The chro nology of dune building is detailed from the earliest evidence of aeolian activity. This is followed by a reconstruction of the palaeoenvironment of the last dune building phases, an assessment of the impact of Aboriginal burning, and a concluding sketch of the impact of European settlement. scale anti-clockwise whorl in which sand has I. The dunefields in their geologic been transported towards the east in the and geomorphic settings southern part of the dunefield, towards the north in the eastern part, and towards the Continental dunes of varying areal density west in the northern part of the whorl. The occur on about 40% of the surface of Australia most recent mapping of the dunefield has (Figure 1), making dunefields the most common augmented JENNINGS'(1968) map and now it landform assemblage, followed by uplands, is clear that the whorl is closed on its western alluvial plains, the coastal zone, lakes and side in the Gibson Desert of Western Australia. volcanic landforms. Examples of the main dune Despite the apparent potential for transport types are shown in Figure 2. Linear dunes of of sand over long distances around the whorl, different types are dominant in the dunefields, grain size and petrographic data show that with linear narrow crested dunes outnumbering sand has not moved very far from its sources both broad crested linear dunes and very short (WASSON,1983a). narrow crested linear dunes. Network dunes, The Mallee, Strzelecki, Simpson and Great parabolic and crescentic dunes are relatively Sandy dunefields (Figure 1) lie largely in infrequent, although parabolics are common on topographic basins which are also structural coasts. There are no extensive areas of basins that took their present gross form in the transverse dunes or star dunes in Australia, Mid to Late Tertiary (WASSON,1982). The and barchans have not been reported. It other dunefields lie in topographically more must be noted that about 20% of the dunefield complex areas. The Tanami dunefield lies on consists of dunes that cannot be adequately surfaces of low relief scattered between low classified and these are referred to as "confused ranges, dissected lateritic tablelands and plains, dunes." A thorough discussion of dune clas and dunes lie adjacent to floodlands and sification is provided by MCKEE(1979). sandplains. The northern Gibson dunefield is Most of the linear dunes join in y-junctions simply an extension of the Great Sandy dune which close in the direction of the modern field but further south the dunes lie between sand-shifting wind resultants (WASSON, low tablelands and ridges; a landform pattern 1984a), and are thought to reflect both modern that extends into the Great Victoria dunefield. and past wind resultants. From the y The western Gibson dunefield lies on the junctions, and orientation of parabolic and Yilgarn Plateau, and here the dunes lie along lunette dunes, the direction of movement of valleys set between lateritic breakaways, dunes can be determined (Figure 1). The granitic plains and ridges of metamorphic rock dune orientation map depicts a continental (JENNINGSand MABBUTT,1977). * Division of Water and Land Resources , CSIRO, GPO Box 1666, Canberra, Australia, 2601. 56 R. J. WASSON Figure 1. The major continental dunefields of Australia with directions of dune elongation and annual resultants of sand shifting winds. The shaded part shows the area of dunefields. The recently mapped (Figure 1) dunefield - Pleistocene lake sediments (Blanchetown Clay) of southern Western Australia consists of dunes (LAWRENCE,1980), while the sub-parabolic lying both in and downwind of shallow valleys quartzose dunes of the Lowan Sand are derived cut in lateritic plains and stripped granitic largely from the Mio-Pliocene littoral to near plains. In the far southwest of the Yilgarn shore regressive Parilla Sand (LAWRENCEand Plateau, the dunes border sources in shallow ABELE,1976; LAWRENCE,1980). valleys on a gently sloping plateau of granite By contrast, in the Canning Basin, which and gneiss. underlies much of the Great Sandy dunefield, The sources of sediment moulded into dunes and in the Officer Basin, which underlies much are diverse in the Australian dunefields. They of the Great Victoria dunefield, there is little include stream and lake sediments that are evidence of the Cainozoic downwarping that still accumulating, relict lacustrine sediment, has allowed relatively thick sequences of alluvium, and regressive marine sands. More sediment to accumulate in the basins underly specifically, the Simpson dunes were derived ing The Mallee and Simpson dunefields. In from actively accumulating alluvium along the Officer Basin, sandstones of the Lampe rivers in the south, from groundwater-control Beds mark the beginning of a terrestrial led deflation of relict alluvium and lacustrine fluviatile regime replacing the Cretaceous beds in the south-centre, and from relict marine environment. The post-Lampe Bed alluvium in the north (WASSON,1983a, b). In expression of alluviation lies in palaeorivers The Mallee the clayey linear dunes of the that extend across both the Officer and Canning Woorinen Formation (CHURCHWARD,1963; Basins (VAN DE GRAAF et at., 1977). The BOWLERand MAGEE, 1978) were derived age of the Lampe Beds suggests that the from fine-grained relict alluvium and Plio palaeorivers were initiated in the Eocene. The Australian Continental Dunefields 57 Figure 2. Main dune types found in the Australian continental dunefields. A: very short narrow crested linear dunes B: long narrow crested linear dunes C: broad crested linear dunes D: parabolic and crescentic dunes E: network dunes F: confused dunes. Late Cainozoic stratigraphy of the Officer and seen on aerial photographs; and the main Canning Basins has not received serious atten sources of dune sands seem to have been al tion, so that the events after the palaeodrainage luvium and lake sediments. The palaeorivers became relict (probably in the Miocene) cannot have acted as sources, with linear dunes stream be described. However, it is clear that: Qua ing downwind from areas such as Lake Auld ternary sediments up to 20m thick (excluding in the Great Sandy dunefield. the height of dunes) occur in these basins In summary, there are profound differences (Geol. Surv. W. A., 1974); drainage lines between dunefields in Australia. At one end younger than the "palaeodrainage" can be of the spectrum is the extensive well organized 58 R.J. WASSON Simpson dunefield, the dunes in which are suggest that the intersection of groundwater almost completely uninterrupted by hills and with the ground surface occurred after a long streams. At the other end of the spectrum is period of high water tables prior to 30,000 the western side of the Great Victoria dunefield years B. P., the water table falling as evapora where the landf orm pattern is a mosaic of tion and aridity increased. More recently, lateritic plains, mesas, and palaeorivers, with BOWLER(pers. comm.) has suggested that the the dunes forming small groups on relatively deflation of salts from lakes and boinkas flat surfaces. (groundwater outcrops zones, MACUMBER, 1980) led to the widespread efflorescence of II. Dune sediment types surfaces downwind. This idea means that the groundwater control of pelletization may have Most of the Australian continental dunes been less important than that produced by consist of fine to medium quartzose sands with surface efflorescence downwind of salt sources. small quantities of accessory minerals. These The role of salts in pelletization is interpreted sands are derived from the various sources from the analogous features found in coastal listed earlier and in most cases have been sabkhas and lagoons in Africa and Texas, and deflated from quartzose alluvium (WASSON, processes presently occurring near Lake Tyrell 1983a). In addition, BOWLER(1973), BOWLER (NW Victoria) and L. Eyre (N South Australia) and MAGEE (1978), WASSON (1983b), and (BOWLER,1973; WASSON,1983b). However, SLEEMANand STANNARD(1983a, b) have pelletized alluvium does occur on the Riverine drawn attention to both transverse (lunette) Plain under conditions which apparently deny dunes and linear dunes which are rich in clay. to salt a significant role (SLEEMAN,1982). Microscopic examination of these sediments The extraordinary structural stability of pellets has shown that the clay occurs in sand-size in dunes of the Strzelecki dunefield, in the aggregates which contain silt particles and clay absence of carbonates or soluble salts, suggests exhibiting a flecked extinction pattern in either that baking in high daytime tempera polarized light. These aggregates (or pellets) tures of algae/bacteria play a part in maintain have been observed in dunes in The Mallee, the ing and perhaps initiating their form. NANSON Riverine Plain of southeastern Australia, the (pers. comm.) has recently drawn attention to southwest of Western Australia, and in the pellets transported by the modern Gooper Strzelecki and Simpson dunefields (Figure 1). Greek in central Australia, again in the absence Pellets of similar size and type have also of significant quantities of salts. been found in clay-rich mantles on hills in the It is clear, however, that salt does play a Riverine Plain (SLEEMAN,1982), on silcrete major role in pelletization over large areas, both capped mesas on the edges of the Strzelecki mechanically by crystallization and by provid dunefield (author's unpublished data) and on ing an electrolyte for flocculation. WASSON low hills north of Broken Hill (CHARTRES, (1983a, b) has shown that gypsum in the basal 1982). These "clay blankets" are the "parna" parts of dunes in the central Simpson Desert of BUTLER(1956) and represent a dust mantle formed when saline groundwater rose into the deposited from aeolian suspension.