Holocene savanna hydroclimate record from Kinrara Lake, north-east Queensland, Australia

Abstract

We present a record of hydroclimatic change over the Holocene from Kinrara Lake, in a seasonally dry savanna location in north-eastern Australia. The record is derived from the oxygen (δ18O) and carbon stable isotope (δ13C) composition of endogenic and biogenic (gastropod) carbonate. The stable isotope proxy records are complemented by elemental geochemical (Itrax) and sedimentological proxy data providing a record of hydrologic and climate change, spanning 10.5 ka to the present day. Two main forms of endogenic carbonate occur in the lake sediments; (i) carbonate associated with biofilms during the early-Holocene, under drier-than-modern conditions, (ii) photosynthetic and evaporatively-enriched precipitates in the late-Holocene, associated with enhanced climate variability inducing drought periods. Strong relationships between negative δ18O values and increased Ti, Rb, Fe/Mn, inc/coh, are linked with strengthened monsoon conditions, while enhanced periods of dryness are inferred from more positive δ18O values, increased Ca/∑Fe, Ti, Al, and subsequent intensifications in lake productivity (higher Si/Ti, S/Ti, Mn/Ti). Three distinct phases can be identified in palaeohydrological history of the lake; (i) a relatively stable drier-than-modern phase during the early-Holocene (10.5 to 8.2 ka), (2) a significantly wetter-than-modern, monsoon-dominated phase through the mid-Holocene into the late-Holocene (8.2–2.8 cal yr BP), and (3) after 2.8 ka, increased intensity of ENSO-related rainfall variability during the late-Holocene, continuing into the present.