by James Michael Russell, Hendrik Vogel, Thomas von Rintelen, Martin Melles, David A. Fowle, Sean A. Crowe, Sean A. Crowe, John William King, Ian Watkinson, Nigel J. Wattrus, Gordon Douglas Haffner, Janelle Stevenson, Ristiyanti Marsetiyowati Marwoto

Lake Towuti (2.5°S, 121°E) is a, 560 km2, 200-m deep tectonic lake at the downstream end of the Malili lake system, a set of five, ancient (1-2 Ma) tectonic lakes located in central Sulawesi, Indonesia. Lake Towuti’s location in central Indonesia provides an important opportunity to reconstruct long-term terrestrial paleoclimate change in a crucially important yet understudied region- the Western Pacific warm pool, heart of the El Niño-Southern Oscillation. Lake Towuti has high rates of floral and faunal endemism and is surrounded by one of the most diverse tropical forests on Earth making it a hotspot of Sotheast Asian biodiversity. The ultramafic (ophiolitic) rocks and lateritic soils surrounding Lake Towuti provide ferruginous metal substrates that feed a diverse, exotic microbial community in the lake and its sediments, potentially analogous to the microbial ecosystems that operated in the Archean Oceans and on Mars. The Towuti Drilling Program will provide valuable new information to understand the climate, biological, and geomicrobiological evolution of this unique system. Between 2007-2010 we collected highly spatially resolved seismic reflection data (CHIRP and airgun) and numerous long sediment piston cores from various sites distributed across the lake. Seismic data revealed the presence of well-stratified and undisturbed sequences of up to 150 m thick, interpreted as continuous lacustrine sediment infill, which is typically underlain by more heterogeneous sediment packages up to 200 m thick, interpreted as fluvio-lacustrine sediment infill. Multiproxy analyses of our sediment cores document a continuous and detailed record of moisture balance variations and environmental change in Lake Towuti during the past 60 kyr BP, demonstrating the enormous promise of Lake Towuti for an ICDP drilling campaign. Here we propose an integrated Towuti Drilling Project to obtain drill core from the lacustrine and fluvio-lacustrine sequences in Lake Towuti. This will provide ideal material to gather information on (1) environmental, climatic, and limnological change over multiple glacial-interglacial cycles during the past ~650,000 years; (2) the age and origin of the lake and the environmental and climatic context that shaped the evolutionary history of endemic faunal and floral elements; (3) long-term changes in the microbial ecosystem, as well as microbial processes operating at depth in the sediment column. In order to best address the scientific key objectives we propose to drill three sites that were selected by the TOWUTI Science Team based on site survey datasets and mutual discussions using the Deep Lakes Drilling System.

• The sediments of Lake Towuti offer extraordinary interdisciplinary opportunities to reconstruct past climates and environments in the western equatorial Pacific, to study the origins and causes of explosive speciation in a tropical lake, to investigate coupled carbon and metal cycling in a ferruginous basin, and to investigate the structural geological evolution of a unique strike-slip basin. Through continental scientific drilling, our team will:
• Provide long and continuous lake sediment cores from Lake Towuti to test the timing, pattern, and mechanisms of orbital- to millennial-scale climate change in the western equatorial Pacific region;
• Investigate the long-term stability and resilience of rainforest vegetation to changes in climate, greenhouse gases, and fire frequency in one of the most diverse rainforests on Earth;
• Determine the age of Lake Towuti and the ensuing rates of speciation of Towuti’s endemic fauna;
• Document the timing of past changes in hydrological connectivity between the Malili Lakes, and evaluate models and mechanisms of biological evolution within Lake Towuti;
• Investigate the extent and metabolism of microbial life in the sediments in a ferruginous, non-sulfidic basin, and their relationships to carbon cycling, metal deposition, and gas generation;
• Evaluate the effects of climate-driven changes in the aquatic and terrestrial environment on water column and sedimentary biogeochemical cycling.

Asia, Geomicrobiology, Indonesia, Lake Drilling, Lake Towuti, Paleoclimate, Speciation, TOWUTI

Latitude: -2.71723, Longitude: 121.51479