01whole.pdf (5.32 MB)
A palaeoenvironmental and palaeofire record from Dunphy Lake, Warrumbungle Mountains, south-eastern Australia / Jamie Lobb.
thesisposted on 2022-03-28, 13:28 authored by Jamie Lobb
This study addresses a significant geographical and temporal gap that exists in the Holocene record of fire and palaeoenvironmental conditions in the region of the Warrumbungle Mountains in eastern Australia. A multi-proxy approach (sedimentology, geochemistry, geochronology and macro-charcoal) was used at Dunphy Lake. A persistent, deep lake phase between ~18.2-16.8 ka was followed by a transition to infrequent dry and wet phases which continued to the present day. The detailed Late Holocene macro-charcoal record spans the last ~2.2 ka and shows that the main periods of enhanced fire activity coincide with an intensification of El Niño Southern Oscillation. High macro-charcoal concentrations overlap with the deposition of coarse sediment (sand) in Dunphy Lake, suggesting that some fires occurred at similar times to episodes of significant runoff and sediment flux from the catchment associated with intense dry to wet phases. An increase in macro-charcoal during the last ~2.2 ka also coincides with an increase in sediment accumulation rate from a long-term average of 0.0265 cm a⁻¹ to 0.0329 cm a⁻¹. Pollen was only present in the top of the profile, but indicates the occurrence of periodic wet and dry conditions during the last ~0.42 ka. These findings demonstrate a relationship between past fire events and post-fire aggradation, showing that an increase in fire and sedimentation during the Late Holocene is a complex response to environmental change.