Foreword: Revisiting Lake Eyre Basin landscapes

Abstract

Sitting at the heart of the Australian continent, the modern drainage system termed the Lake Eyre Basin (LEB) has always occupied a special place in the geography of Australia. With its ~1.2 million km catchment area, and currently draining one-fifth of the continent, it is the fourth largest internally draining basin in the world. Much like its global counterparts in Africa (e.g. Chad Basin), or Asia (Caspian Basin), the Lake Eyre Basin is a wide and relatively shallow intra-cratonic basin with a long history of slow tectonic warping and subsidence. Succeeding an earlier Mesozoic basin that existed in Central Australia, an internally draining sedimentary depositional centre existed through much of the Cenozoic. This resulted in the geological structure termed the Lake Eyre Basin whose extent is primarily subsurface and is represented by a series of sedimentary formations, notably, the Palaeocene–Eocene Eyre Formation, the late Oligocene– Pliocene Namba and Etadunna formations, and the Pliocene–Quaternary Wipajiri, Tirari and Kutjitara formations, and their lateral equivalents (see, Callen et al., 1995). These geological structures of the Lake Eyre Basin document an eventful and climatically variable history in the Cenozoic, accompanied by a general drying trend that led into the arid to semi-arid environmental conditions that dominate much of the continent’s interior today (e.g. Martin, 2006; McGowran & Hill, 2015). Superimposed on, but only partly overlapping the geological Lake Eyre Basin, is the modern drainage system of the Lake Eyre Basin (LEB; see, Habeck-Fardy & Nanson, 2014 for a review). The aridity of the LEB is clearly reflected in many environmental variables (Figure 1). For example, annual rainfall totals can be as low as ~120 mm/a in the central portion of the basin. Low annual rainfall combines with evaporation rates of >4000 mm/a to provide a primary control on soils, flora and fauna, their ecological characteristics and evolution. While much of the LEB is covered by grasses and shrubs, these arid landscapes prompted early explorers to label the LEB as the “dead heart” of Australia – a perspective that clearly ignored the LEB’s environmental, ecological, geomorphic, hydrological, or even just the topographic diversity, across all spatial scales. It was not until the mid-20 century, however, that scientists started to systematically approach and investigate this diversity, and early work on the landscapes in the LEB soon recognised the variable nature of environmental conditions over seasonal to multimillennial temporal scales. It became clear, that even the lowest and possibly driest place on the Australian continent – the salt-covered lake floor of Kati Thanda-Lake Eyre –