Late-Holocene climatic variability indicated by three natural archives in arid southern Australia

Abstract

Three terrestrial climate proxies are used to investigate the evolution of Holocene palaeoenvironments in southern central Australia, all of which present a coherent record of palaeohydrology. Single-grain optically stimulated luminescence from sediments supplemented by 14C from charcoal and lacustrine shells was obtained to date shoreline deposits (Lake Callabonna) and the adjacent Mt Chambers Creek alluvial fan. Our findings are complemented by a U/Th-based record of speleothem growth in the Mt Chambers Creek catchment, which we interpret to reflect increased precipitation. Together, these archives shed light on the timing of, and possible sources of water for, Holocene pluvial intervals. We identified several phases of elevated lake levels dated at ~5.8–5.2, 4.5, 3.5–2.7 and 1 kyr, most of which correspond to fluvial activity resulting from increased precipitation in the adjacent ranges. The enhanced hydrology during phases of the late Holocene likely increased the reliability of resources for regional human populations during a time of reduced winter rainfall. When considered within the framework of the current understanding of Holocene palaeoclimate in central Australia, our data suggest that the pattern of landscape response was broadly synchronous with larger scale climatic variability and punctuated by pluvial periods greater than today.

Late Quaternary evolution of a playa margin at Lake Frome, South Australia

“…Combined with our results of dune and spit formation, the existing data clearly imply active sediment supply from the Flinders Ranges at ~6-7 ka leading towards peak mid Holocene lake levels of ~3-4 m AHD at Lake Frome with the formation of the spit shortly after 5 ka. This scenario is in general agreement with other proxy records from around the Flinders Ranges documenting wet conditions between ~7 and 3 ka (Gliganic et al, 2014;McCarthy and Head, 2001;Quigley et al, 2010).…”

“…Deposition of Unit 2b around ~11 ka at ~4 m AHD is likely related to a lake transgression as recorded by beach facies in a prominent beach ridge between ~5-7 m AHD at Lake Callabonna , and supports the notion of locally wet conditions during the PleistoceneHolocene transition as seen is other regional studies around Lake Frome (De Deckker et al, 2011;Gliganic et al, 2014;Quigley et al, 2010). A detailed comparison of all younger, Holocene ages with existing chronologies from beach ridges (Fig.…”

“…As such, it provides new data towards an improved link between previously published records of lake stands as expressed by beach ridges along the western shores of Lake Frome and Callabonna Gliganic et al, 2014), and the detailed sedimentary, paleoenvironmental and geochemical records from cores in the lake centre (Bowler et al, 1986;De Deckker et al, 2011;Draper and Jensen, 1976;Singh, 1981). This link is expressed by (i) the good chronological overlap between the stratigraphic units in our study area and previously published lake stands as expressed by beach ridges.…”

“…In this context, the good agreement of a 2.8 ka radiocarbon age in the active Balcanoona Creek terminal splay and the construction of a beach ridge at Lake Callabonna at ~2.7 ka (Gliganic et al, 2014) implies that these events were short-lived, not enabling significant sediment delivery to the lake floor and limiting modifications to the playa marginal shoreline.…”

“…8b) shows that the evidence for sedimentary dynamics in relation to Holocene lake highstands is restricted to elevations below ~2.5 m AHD at our Lake Frome study site. This is below the possible elevation range for a connected and single water body across both lakes as dictated by the Salt Creek sill at 5±2 m AHD, and contrasts with beach deposits and beach ridges at ~5 m AHD dated to ~3.5-5.6 ka at Lake Callabonna Gliganic et al, 2014). So far, no beach ridges or other sedimentary evidence for lake levels at this elevation have been documented or dated around Lake Frome, even though samples from sandy clays in the upper metre of sediment in the lake centre yielded Holocene radiocarbon ages of ~3.4 and 4.6 cal ka BP (De Deckker et al, 2011;Draper and Jensen, 1976).…”