Project Overview

For a brief overview of the project, see our pdf brochure in English or Bahasa

Lake Towuti is located on the island of Sulawesi, in central Indonesia. It is the largest tectonic lake in Indonesia, with a surface area of 560 km2 and a water depth of 200 m. It is at the downstream end of a chain of large, ancient tectonic lakes known as the Malili Lakes, consisting of Lakes Matano, Mahalona, and Towuti.

These lakes are surrounded by the East Sulawesi Ophiolite, the third largest ophiolite field in the world. The regional climate is very humid and tropical, with mean annual precipitation rates of ~3 meters/year. The lakes are dilute, circumneutral, and ultraoligotrohpic.

 

The Towuti Drilling Project seeks to drill and analyze 100-200 meter long sediment cores from Lake Towuti, South Sulawesi, Indonesia to understand the climatic, biological, geological, and biogeochemical history of central 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 and the rest of the Malili Lakes have high rates of floral and faunal endemism, with endemic flocks of fishes, snails, shrimp, and crabs, and are surrounded by one of the most diverse tropical forests on Earth making the region a hotspot of Southeast Asian biodiversity. The ultramafic (ophiolitic) rocks and lateritic soils surrounding Lake Towuti provide ferruginous metal substrates to a microbial community that catalyzes a complex set of biogeochemical reactions, precipitating high concentrations of metals (Fe, Cr, Ni) in the lake and its sediments.  These processes vary under a changing climate, resulting in a highly variable limnological that challenge Towuti's flora and fauna, and a variable geochemical environment that challenges our understanding of ore formation and the links between sedimentary proxies and paleoclimate.  The Towuti Drilling Project will provide valuable new information to understand the paleoclimatology, geology, biology, and metal biogeochemistry of this unique 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. Indeed, Lake Towuti will be the first lake drilling target anywhere in Southeast Asia. Highlights of this site include:
• The Indo-Pacific Warm Pool is the largest pool of warm water on Earth and is the source for much of Earth’s atmospheric water vapor, the Earth’s most important greenhouse gas.  Lake Towuti will provide the longest available record of changes in the hydrological cycle in this globally important region.
• The Malili Lake chain, of which Towuti is part, is the only highly biodiverse chain of lakes on Earth and offers a valuable natural laboratory to study biological evolution. Interestingly, despite hydrologic connections between the Malili Lakes, each houses its own endemic fauna, suggesting the organisms in these lakes evolved during previous intervals of basin isolation driven by changing lake levels or regional tectonics.
• Lake Towuti is one of the only large lakes on Earth that is housed in ophiolite.  Its sediments offer a valuable opportunity to investigate the geomicrobiology of metalliferous sediments and the interactions between climate, metal and carbon cycling, and metal burial. Moreover, Lake Towuti is now experiencing the impacts of changing land use and climate. By investigating past changes in climate and terrestrial ecosystems and their impacts on Lake Towuti’s chemistry, biology, and metals biogeochemistry, we will improve our understanding of Lake Towuti’s resilience and how to maintain a sustainable Lake Towuti ecosystem.

In particular, the Towuti Drilling Project seeks to drill 6 boreholes through lacustrine and fluviolacustrine sedimentary sections that will record the history of this basin during the past 1.5 Ma.  We will conduct on-site logging of these cores and immediate samples of metals, gases, and microbes to identify the organisms living in the lake sediment and the redox-sensitive metal reaction pathways they control.  After drilling, the sediment cores will be analyzed by an international team of nearly 30 scientists from the USA, Indonesia, Canada, and other project member countries to conduct multiproxy analyses to determine:
• The timing, pattern, and mechanisms climatic and hydrologic change in the western equatorial Pacific region, and in particular the pacing of orbital scale variability during the last 700,000 years;
• 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;
• The age of Lake Towuti, the rates of speciation of Towuti’s endemic fauna, and the changing environmental conditions that gave rise to these organisms;
• The extent and metabolism of microbial life in the sediments in a ferruginous lake basin, and their relationships to metal deposition and gas generation;
• The effects of climate-driven changes in the aquatic and terrestrial environment on water column and sedimentary biogeochemical cycling and resulting sedimentary metal concentrations and speciation.
• The rates of formation of the Lake Towuti basin, and the rates of fault movement and slip in this seismically active region.


We plan to drill three sites in Lake Towuti chosen to understand the regional climate and lake level history as well as the regional tectonic and paleobiological history. The planned cores will recover highly stratified lacustrine sediment of up to 150 m thickness, as well as deeper fluviolacustrine sediments deposited during the formation of Lake Towuti.