Last Glacial Maximum and deglacial branched GDGT‐based palaeotemperature reconstruction from a subtropical Australian wetland

ABSTRACT Future projections of climate change in the subtropics suggest warming and drying, while evidence from warm periods in the past shows increases in subtropical temperatures and precipitation. Eastern Australia is subject to interannual hydroclimate drivers and has experienced extreme flooding and droughts in recent years. To understand how the changes to the mean global conditions may affect sensitive environments, such as the wetlands in this region, baseline records of mean temperatures, especially since and during the Last Glacial Maximum (LGM), are vital. Several palaeoenvironment records exist from the coastal sand islands of Minjerribah (North Stradbroke Island) and K'gari (Fraser Island), south‐east Queensland. However, these records appear to show divergent responses to climate change. Whilst there are a variety of proxies used for environmental reconstruction (e.g., pollen, charcoal, dust flux), there are relatively few continuous records of quantitative temperature, which limits our understanding of the causes of environmental change. Presented here is a palaeoclimate reconstruction spanning the LGM to Holocene, utilising glycerol dialkyl glycerol tetraethers (GDGT), for Broutha Waterhole, a subtropical perched wetland in the Cooloola Sand Mass, Queensland, Australia, located between Minjerribah and K'gari. The GDGT‐based palaeotemperature reconstruction features a temperature minimum of 17.0°C (~4.3°C maximum cooling) during the LGM, which is very close to the palaeotemperature recorded from K'gari and consistent with the Australia‐wide temperature range. A progressively warming temperature during the deglacial is interrupted by a temperature decline (0.8°C–1.6°C) coincident with the Antarctic Cold Reversal (ACR), followed by a stable warm Holocene. It should be noted that there are possibilities of hiatuses of different periods at Cooloola Sand Mass compared to K'gari and Minjerribah, which may imply different control on the sediment deposition. This study provides a palaeotemperature record through the LGM and deglacial period that contributes to the limited quantitative temperature data in the subtropics.