Paper No. 9-25
Presentation Time: 8:00 AM-6:00 PM
LATE HOLOCENE ENVIRONMENTAL CHANGE FROM HIGH-RESOLUTION LAKE SEDIMENTS IN THE SNOWY MOUNTAINS, KOSCIUSZKO NATIONAL PARK, SOUTHEASTERN AUSTRALIA
CULHANE, Natalie1, CLARK, Douglas H.2, MICKELSON, Emma3, BURDICK, Aidan4, MCCALLUM, Adrian5, MACKENZIE, Lydia6, SHULMEISTER, James7 and CLARK, Jessa1, (1)Geology, Western Washington University, 516 High St, Bellingham, WA 98225, (2)Geology Department, Western Washington Univ, 516 High St., MS 9080, Bellingham, WA 98225, (3)Geology, Western Washington University, 516 High st, Geology Dept, Bellingham, WA 98225, (4)Earth and Planetary Sciences, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208, (5)School of Science and Engineering, University of the Sunshine Coast, Sippy Downs, 4556, Australia, (6)School of Earth Sciences, Zhejiang University, Hangzhou, China, (7)School of Earth and Environment, University of Canterbury, 20 Kirkwood Avenue, Christchurch, 8041, New Zealand
Over the past millennium, the environment of southeastern Australia has undergone substantial changes in environmental response and land management, largely related to climate change and late 18th century European colonialization. Although most previous studies focused on climatic changes across longer time scales, limited research has scrutinized the environmental impacts in this most recent transition. Lake sediments from glacial tarns in southeastern Australia’s Snowy Mountains provide an excellent opportunity to constrain environmental changes during this crucial period. Previous studies analyzing environmental proxies in sediment from the tarns Club Lk and Blue Lk imply anthropogenic influences and indicate fluctuations between cooling trends (1100-800 cal yr BP; 400-340 cal yr BP) and warming trends (800-400 cal yr BP; 60 cal yr BP - present) within the last millennium. However, this interpretation conflicts with other local (speleothem) and regional climate records.
To address these discrepancies, we collected a suite of sediment cores from two of the lakes (Albina and Club) in the Snowies in August 2022. At Lk Albina, we used a gravity corer and a Livingstone corer to collect sediments related to the last several millennia. Preliminary 14C and loss-on-ignition (LOI) analyses of the sediments reveal substantial variability in organic content during the last millennium, from 12% to >40%, with peaks at ca. 800 ya and 500 ya. Subtle peaks in magnetic susceptibility (2-2.5*10-3) correspond to LOI low points at ca. 600 ya and ca. 1320 ya, which also match peaks in charcoal accumulation in a previously published record for Club Lk. These peaks may indicate warmer, dryer regional conditions. In contrast to Albina, Club Lk data show less variability, with consistently lower LOI (3-14%) and higher magnetic susceptibility (1-18*10-3), suggesting this basin may be less sensitive to environmental change. Ongoing 210Pb dating and grain size analyses will provide tighter age constraints and further illuminate environmental changes in both lakes. Complete results of our analyses will be presented at the meeting.
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