We investigated the mineral-magnetic behavior of sediments from Lake Towuti located in the Eastern Sulawesi Ophiolite belt, Indonesia. Rock magnetic analysis supplemented by X-ray diffraction and scanning electron microscopy analysis were performed on sediment core TOW10-9B from the north basin of Lake Towuti to give insights on the environmental and sedimentary processes controlling the magnetic properties of the sediment and its paleoclimatic significance. The results show that the core has three distinct zones of varying magnetic properties. Careful examination demonstrates that these zones correspond to varying levels of iron oxide dissolution and magnetite precipitation that are climatically and environmentally dependent. The magnetically strongest zone is characterized by weak iron oxide dissolution and intense magnetite precipitation, likely driven by changes in the stratification and/or water level of the lake during dry conditions in Marine Isotope Stage 2 (MIS2) period, whereas the two magnetically weaker zones are characterized by signs of dissolution and correspond to relatively wet conditions, respectively, during Marine Isotope Stage 3 (MIS3) and the Holocene. Although our data show that major changes in concentration dependent parameters, such as magnetic susceptibility and saturation isothermal remanent magnetization (SIRM), in Lake Towuti sediment correlate with changes in regional rainfall, many of the concentration changes are more strongly affected by in situ chemical processes than by changes in erosion and terrestrial sediment supply. These findings urge caution in the interpretation of magnetic mineral concentration profiles as indicators of clastic sediment inputs.
Bibliographical noteFunding Information:
We thank the Indonesian Ministry of Research and Technology (RISTEK) for permission to conduct the field research, Anders Noren and Satrio Wicaksono for field assistance, Limnological Research Center (LRC) University of Minnesota for their coring system, and PT. Vale Indonesia Tbk for logistical assistance. This research is partially based upon work supported by the National Science Foundation under Grant Number NSF-EAR-0902845 to JMR. Additional financial support was received from the Institut Teknologi Bandung in the form of a sandwich research grant (IMHERE 1st Batch) to GT and Research & Innovation Grant to SB. The initial part of this research was supported by Hibah Kompetensi research grant to SB from the Indonesian Ministry of National Education .
© 2014 Elsevier B.V.
Copyright 2015 Elsevier B.V., All rights reserved.
- Lake Towuti
- Magnetic minerals
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