Holocene and recent aeolian reactivation of the Willandra Lakes lunettes, semi-arid southeastern Australia

Abstract

The Willandra Lakes in semi-arid southeastern Australia provide some of the most continuous combined palaeoenvironmental and archaeological records on the continent. These are best preserved within the transverse shoreline (lunette) dunes on their downwind margins. Following final lake retreat c. 15 ka avulsion of the dominant fluvial inflow eastwards, the Willandra lunettes periodically reactivated, experiencing erosion, aeolian redeposition and alluvial sheetwash. These reworked sedimentary archives reflect regional climatic conditions rather than those of the entire catchment. Yet the focus of most study in the region to date has remained on the late Pleistocene. The general paucity of Holocene data has contributed to a perception that people largely abandoned the area in favour of the perennial Murray and Darling Rivers to the south and west. Our study reconstructs past geomorphological conditions and patterns of human mobility in adjacent Lakes Mungo and Durthong over the last c. 15 ka subsequent to final lake retreat, including the most recent 150 years since Europeans established pastoralism in the region. Our data show that Indigenous people did not abandon the area as previously assumed, but developed effective strategies for responding to the changed environmental conditions. Final lake retreat transitioned into a phase of aeolian accumulation c. 15-12 ka, indicating locally dry conditions. Subsequent aeolian reactivation peaked during arid phases experiencing less rainfall in the early Holocene and twice in the most recent 1000 years prior to European settlement in the area. Alluvial sheetwash was deposited onto lake floors during the mid-Holocene, and again in the early decades of European settlement. Aeolian reactivation, likely driven by European pastoral activities, increases in the most recent 150 years. Our study underscores the necessity of integrating geomorphological and archaeological investigations over landscape scales in order to optimise our understanding of interactions between people and their environment through time.

Northward expansion of the westerlies over glacial southeastern Australia: evidence from semi-arid lunette dunes, temperate basalt plains, and wind modelling

“…The two LGM ages at the overflow lake, WPL, derive from both sandy and clayey sediments from its inner lunette and likewise suggest oscillating water levels. Both the timing and sediments associated with this phase correlate with the so-called Arumpo unit of oscillating lake filling and drying observed in other Willandra basins (mean age 21.8 ± 3.4 ka; Fitzsimmons et al, 2015), and which represents the final phase of lake filling before the Willandra Creek ceased to flow (Fitzsimmons et al, 2019). The c. 29 ka age for the alternating sands and clayey sands of the WPL outer lunette predates inner lunette deposition.…”

“…The Willandra Lakes are a presently dry chain of five large (and several smaller) lakes located in the Murray-Darling Basin (MDB) of semi-arid southeastern Australia, a system best known for its preservation of past hydrological, environmental and archaeological traces (Bowler, 1976;Fitzsimmons et al, 2014;Fitzsimmons et al, 2019;Barrows et al, 2020;Jankowski et al, 2020), including some of the earliest evidence for human occupation on the continent (Bowler, 1998;Bowler et al, 2003). The lakes were fed almost entirely by the Willandra Creek, a distributary of the Lachlan River which has its headwaters in the temperate highlands and which ceased to flow just after the LGM (Fitzsimmons et al, 2014).…”

Revisiting the abandoned shorelines of Lake George, Australia: a refined optical dating framework

“…9e; Bowler et al ., 2012). Significant work within Lake Mungo has been conducted by numerous authors (Bowler et al ., 2003; Bowler et al ., 2012; Fitzsimmons et al ., 2014; 2019; Barrows et al ., 2020; Jankowski et al ., 2020). Although there is some variability in the palaeoenvironmental interpretations between these studies, a period of predominantly lake‐full conditions is thought to have existed from ~65 until ~36 ka ago (Fig.…”

Biocultural GIS mapping: A Living Country and Terra Nullius, Willandra Lakes Region World Heritage Area (WLRWHA), NSW

“…The areas of research focus in the Willandra are predominantly on the Lake Mungo lunette, with the other lunettes as subsidiary focus areas. This can be substantiated by even a cursory look at the published material from the Willandra Lakes, summarised by Fitzsimmons et al (Fitzsimmons, Spry, & Stern 2019). Long running projects conducted by Bowler and Stern have predominantly focussed on the Lake Mungo lunette (Please see Figure 20).…”