Quaternary climatic instability in south‐east Australia from a multi‐proxy speleothem record

Abstract

Milankovitch‐scale Quaternary climatic oscillations within south‐east Australia are known to be characterized by relatively arid glacial and wet interglacial stages. However, terrestrial proxy records of environmental change are scarce, based largely on river terraces, dune sediments and pollen sequences. Here we present a speleothem‐based palaeoclimate record from Yarrangobilly caves, south‐east Australia. The oxygen isotopic composition of calcite (δ18Ocalcite) is taken to represent rainfall amount and used as an aridity index. High‐resolution trace element profiles and UV fluorescence support interpretations based on δ18Ocalcite, allowing further designation of key phases of speleothem growth into periods of relative aridity and moisture excess. A hiatus of approximately 37 ka duration divides the record into two key phases of growth which can be mapped onto marine isotope stages 5c–a and 3, respectively. Increasing aridity in the latter half of MIS 5 led to cessation of speleothem growth for the duration of MIS 4. Growth recommences during MIS 3, associated with greater moisture availability, enhanced vegetation and augmented biogeochemical cycling. This speleothem record provides a unique context of terrestrial environmental change and depicts hydrological conditions which fluctuate markedly over the 70‐ka period covering the time of megafauna extinction and human arrival on the continent.

Millennial-scale glacial climate variability in Southeastern Alaska follows Dansgaard-Oeschger cyclicity

“…The hiatuses recorded in speleothem EC-16-5-F could represent hydrological re-routing or blockage, as noted in speleothem studies elsewhere 24,25 . However, these processes tend to be permanent 26 , and are therefore not consistent with the continued growth of speleothem EC-16-5-F after each hiatus.…”

Groundwater and Global Palaeoclimate Signals (G@GPS)

“…Recent work from speleothem records in Yarrangobilly (~470 km SW of Sydney) differentiate two periods of growth covering MIS5b and 5a with an increasing aridity trend resulting in a growth hiatus covering MIS4 and restarting growth during MIS3 (Webb et al, 2014). Groundwater records, at present, can only be compared to the later part of the speleothem record but also show increasing wet conditions in Sydney Basin data at about 5-6 ka.…”

A multimethod approach to inform epikarst drip discharge modelling: Implications for palaeo‐climate reconstruction

“…The region may provide critical data to understand the palaeo‐climate of both southeastern Australia and the Southern Hemisphere, due to the location of the caves complex, which experiences precipitation sourced from southern mid‐latitudes to the tropics (Callow, McGowan, Warren, & Speirs, ; Theobald, McGowan, Speirs, & Callow, ). Despite this, there is very little published research conducted on the speleothems and associated hydrology of this region (see Markowska et al, ; Spate, Jennings, Ingle Smith, & James, ; Webb et al, ).…”

“…This will aid theCallow, 2015). Despite this, there is very little published research conducted on the speleothems and associated hydrology of this region (seeMarkowska et al, 2015;Spate, Jennings, Ingle Smith, & James, 1976;Webb et al, 2014).…”