Abstract
Humid tropical landscapes are subject to intense weathering and erosion, which strongly influence sediment mobilisation and deposition. In this setting, we aimed to understand how geomorphology and hydroclimate altered the style and intensity of erosion and sediment composition in a tropical lake and its tectonically active catchment. Lake Towuti (2.75°S, 121.5°E) is one of the oldest and deepest lakes in Indonesia, with uninterrupted lacustrine sedimentation over several glacial–interglacial cycles. Here we present results from a novel set of Lake Towuti surface sediment, bedrock and soil samples from the catchment, and two existing sediment cores that extend to 30,000 and 60,000 years before present. We studied the catchment morphology, soil properties, geochemistry, and clay and bulk mineralogy. Results from several river long profiles show clear signs of tectonic activity, which enhances river incision, favours mass movement processes, and together with remobilisation of fluvial deposits, strongly influences modern sedimentation in the lake. Material from the Mahalona River, the lake’s largest inflow, dominates modern sediment composition in Towuti’s northern basin. The river transports Al-poor and Mg-rich sediments (mainly serpentines) to the lake, indicating river incision into the Mg-rich serpentinised peridotite bedrock. Relatively small, but important additional contributions of material, come from direct laterite-derived input and the Loeha River, which both provide Al-rich and Mg-poor sediment to the lake. Over time, the Al/Mg and kaolinite-to-serpentine ratios varied strongly, primarily in response to lake-level fluctuations driven by hydroclimatic changes. In the past 60,000 years, both the Al/Mg and kaolinite-to-serpentine ratios showed variations sensitive to changes in climate boundary conditions across glacial-interglacial cycles, while tectonic activity had less influence on changes in sediment composition on these short time-scales.
Original language | English (US) |
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Pages (from-to) | 279-295 |
Number of pages | 17 |
Journal | Journal of Paleolimnology |
Volume | 61 |
Issue number | 3 |
DOIs | |
State | Published - Mar 15 2019 |
Bibliographical note
Funding Information:Acknowledgements The Towuti Drilling Project was partially supported by grants from the International Continental Scientific Drilling Program, the US National Science Foundation, the German Research Foundation, the Swiss National Science Foundation (20FI21_153054/1 and 200021_153053/1), Brown University, Genome British Columbia, and the Ministry of Research, Technology, and Higher Education (RISTEK). PT Vale Indonesia, the US Continental Drilling Coordination Office, the GeoForschungszentrum Potsdam and DOSECC Exploration Services are acknowledged for logistical assistance to the
Funding Information:
project. We further thank Franziska Nyffenegger for support with the geotechnical analysis, Urs Eggenberger and Christine Lemp for help with the clay and bulk XRD analysis, Elias Kempf for assistance with thin section analysis, as well as Pierre Valla and Romain Delunel for fruitful discussions regarding the geomorphic aspects of the study. This research was carried out with permission from the Ministry of Research and Techonology (RISTEK), the Ministry of Trade of the government of Indonesia, and the Natural Resources Conservation Center (BKSDA) and Government of Luwu Timur of Sulawesi. We also wish to thank two anonymous reviewers and the editors for their helpful comments and suggestions, which improved our manuscript.
Publisher Copyright:
© 2018, Springer Nature B.V.
Copyright:
Copyright 2019 Elsevier B.V., All rights reserved.
Keywords
- Erosion
- Hydroclimate
- Lake level
- Lake Towuti
- Laterite
- Tropical palaeoclimate
Continental Scientific Drilling Facility tags
- TDP