LAKE TOWUTI, INDONESIA: FIRST SEDIMENTOLOGICAL RESULTS OF A NEW SURFACE SEDIMENT STUDY DURING THE ICDP-TDP CAMPAIGN 2015

Abstract:

A. HASBERG¹, M. MELLES¹, H. VOGEL², J. RUSSEL³, S. BIJAKSANA⁴ and all ICDP field campaign participations

¹Institute for Geology and Mineralogy, University of Cologne, Zülpicher Str. 49a, 50974 Cologne, Germany, email: hasberga@uni-koeln.de

²Department for Geology, University Bern, Switzerland

³Department of Geology, Brown University, USA

⁴Faculty of Mining and Petroleum Engineering, Institute Teknologi Bandung, Indonesia

Lake Towuti (2.75°S, 121.5°E), the largest tectonically formed lake (surface area: 561 km²) of the Republic Indonesia, is located in Central Sulawesi. The lake has a high, unique, Fe-reducing bacterial biodiversity and it has an important relevance to evolutionary biology through its location. Furthermore it is part of the Malili lake system, which consists of five lakes. The three largest of these, Matano, Mahalona and Towuti, are connected through a surface outflow today, but the linkage may not have always existed during the past, as indicated by the high level of endemism in each lake and the active tectonic movement of the ‘Matano Fault system’.

In summer 2015 the ICDP-funded Towuti Drilling Project (TDP) was conducted at Lake Towuti and recovered over 1000 meters of new sediment core. Within the scope of the TDP, lake surface sediments were also collected to investigate the modern terrestrial climate and aquatic environmental conditions, as well as the major sediment input sources from the catchment area. We collected a 1 to 4 km high-resolution grid of 84 surface samples from Lake Towuti and five samples from the Mahalona River, which links the Malili Lakes. These 89 surface samples were analyzed by various, sedimentological methods including smear-slide microscopy, coarse-fraction analyses, grain-size analysis, XRF-powder, and CNS measurements.

The results will help to understand the interaction between the present-day lake sedimentation, hydrological and climatic conditions and to evaluate these as proxies for the hydrological connections between the Malili lakes -and paleoclimatic conditions. The reconstruction of the long-term history of the hydrological connection of the Malili Lakes due to the surface runoff into Towuti will be based on the dataset from these surface samples.