ALBERT

Description: The Towuti Drilling Project (TDP) is an international research program, whose goal is to understand long-term environmental and climatic change in the tropical western Pacific, the impacts of geological and environmental changes on the biological evolution of aquatic taxa, and the geomicrobiology and biogeochemistry of metal-rich, ultramafic-hosted lake sediments through the scientific drilling of Lake Towuti, southern Sulawesi, Indonesia. Lake Towuti is a large tectonic lake at the downstream end of the Malili lake system, a chain of five highly biodiverse lakes that are among the oldest lakes in Southeast Asia. In 2015 we carried out a scientific drilling program on Lake Towuti using the International Continental Scientific Drilling Program (ICDP) Deep Lakes Drilling System (DLDS). We recovered a total of  ∼ 1018 m of core from 11 drilling sites with water depths ranging from 156 to 200 m. Recovery averaged 91.7 %, and the maximum drilling depth was 175 m below the lake floor, penetrating the entire sedimentary infill of the basin. Initial data from core and borehole logging indicate that these cores record the evolution of a highly dynamic tectonic and limnological system, with clear indications of orbital-scale climate variability during the mid- to late Pleistocene.

Description: The mass magnetic susceptibility (MS) was analyzed on wet bulk sediment aliquots using a KLY-2 Kappabridge (AGICO, Brno, Czech Republic). MS measurements were carried out on sample containers of 2 x 2 x 1.6 cm (i.e. a sample volume of 6.4 cm3), which frequently are used for palaeo and rock magnetic measurements. The only exceptions are samples 12 and 33, which did not contain sufficient material.

Description: For granulometric, geochemical and mineralogical analyses, approximately 25 ml of each surface sample was frozen for 24 hours and subsequently lyophilized using a Christ BETA 1-8 LDplus (Martin Christ Gefriertrocknungsanlagen GmbH, Osterode am Harz, Germany). The freeze-dried samples were homogenized and split into two aliquots. The other aliquot of the freeze-dried surface samples was ground to 〈63 µm with a Planetary Mill Pulverisette 5 (FRITSCH GmbH, Idar-Oberstein, Germany) and used for mineralogical and geochemical analyses. For quantitative analyses of the inorganic element composition of the surface samples, including concentrations of selected major, minor and trace elements (Ti, K, Al, Mg, Ca, Fe, Cr and Mn), 0.5 g of dry and ground bulk sample material was digested using a near-total digestion protocol with HCl, nitric (HNO3), perchloric (HClO4) and hydrofluoric (HF) acids in heated and closed teflon vessels. Measurements were performed by means of inductively coupled plasma-mass spectroscopy (ICP-MS) at Activation Laboratories Ltd., Ancaster, ON, Canada. Separate Si measurements were conducted by energy-dispersive X-ray fluorescence (ED-XRF) using a portable analyzer (NITON XL3t; Thermo Fisher Scientific, Waltham, MA, USA) at the University of Cologne, Germany. Triplicate measurements were performed on pellets of freeze-dried and ground sample aliquots, which were pressed into teflon rings under 12 bars, and subsequently covered with a 4 µm polypropylene film (X-ray film, TF-240-255, Premier Lab Supply, Port St. Lucie, FL, USA). Measurements were performed using a gold anode X-ray source (70 kV) and the 'mining-minerals-mode'. The secondary X-rays of element-specific photon energies were detected with a silicon drift detector and processed by a digital signal processor. Si concentrations (in ppm) were calculated from the element-specific fluorescence energies and compared with external and internal reference materials (STDS-4, BCR142R and BCR-CRM 277).

Description: For granulometric, geochemical and mineralogical analyses, approximately 25 ml of each surface sample was frozen for 24 hours and subsequently lyophilized using a Christ BETA 1-8 LDplus (Martin Christ Gefriertrocknungsanlagen GmbH, Osterode am Harz, Germany). The freeze-dried samples were homogenized and split into two aliquots. The other aliquot of the freeze-dried surface samples was ground to 〈63 µm with a Planetary Mill Pulverisette 5 (FRITSCH GmbH, Idar-Oberstein, Germany) and used for mineralogical and geochemical analyses. Total organic carbon (TOC) as well as total carbon (TC), total nitrogen (TN) and total sulfur (TS) were measured with a vario MICRO cube and vario EL cube combustion elemental analyzers (Elementar Analysesysteme Corp., Langensebold, Germany), respectively. For the TOC measurements, 15 mg of sediment powder was placed into metallic silver containers, heated to 100 to 120°C, and treated three times with a few drops of HCl (32 %) to dissolve carbonates. The metallic silver containers were then wrapped and pressed into silver paper, and the resulting pellets were analyzed for their TOC concentration using the vario EL cube. All concentrations are given as mean values of duplicate measurements. For TC, TN and TS measurements with the vario MICRO cube, 10 mg of sediment powder was placed in zinc containers, with 20 mg of tungsten (VI) oxide (WO2) added to catalyze oxidation. The total inorganic carbon (TIC) was calculated as the difference between TC and TOC. Analytical errors were determined on internal and external reference material. The C/N ratio is calculated as the weight ratio of TOC and TN. The carbon isotopic composition of bulk OM (δ13COM) in the sediment was measured on a set of 42 subsamples at Brown University, Providence, RI, USA. For that purpose, ca 50 mg of sediment was acidified in HCl (2 N) for one hour at 80ºC to remove carbonate minerals. The acid-treated samples were subsequently rinsed in deionized water and centrifuged four times to remove any excess HCl. The samples were then freeze-dried and homogenized prior to isotopic analysis. The δ13COM values were measured using a Carlo Erba Elemental Analyzer coupled to a Thermo DeltaV Plus isotope ratio mass spectrometer (Thermo Fisher Scientific, Waltham, MA, USA). The analytical precision determined through replicate measurements of internal sediment standards was 0.16 ‰. All results are reported relative to the Vienna PeeDee Belemnite (VPDB) standard.

Description: At the University of Cologne, Germany, a subsample was taken from one aliquot and used to produce smear slides for identification of sedimentary components using transmitted light microscopy. On selected samples, sponge spicules and diatom frustules were additionally investigated using a Zeiss Gemini Sigma 300VP scanning electron microscope (SEM; Carl Zeiss AG, Oberkochen, Germany). Furthermore, some magnetic mineral grains were identified with energy dispersive X-ray spectroscopy (EDX) of the Sigma SEM system. Based on smear slide analyses, a set of 40 samples that contain sponge spicules, diatoms and/or tephra particles were selected for automated, non-destructive particle image analyses using a dynamic imaging system (Benchtop B3 Series VS FlowCAM®; Fluid Imaging Technologies, Inc., Scarborough, ME, USA) to quantify the abundance of these particles. Aliquots of wet bulk samples were treated with hydrogen peroxide (H2O2; 30%) for seven days at room temperature to remove organic matter (OM) and disaggregate the siliceous biogenic particles, and were subsequently sieved with 25 and 80 µm meshes. The pre-treated sample fractions were diluted with deionized water (samples 〈25 µm) or polyvinyl pyrrolidone (PVP, 2 %; samples 25 to 80 µm and 〉80 µm). Particle recording in the 〈25 µm and 25 to 80 µm fractions was carried out using a 100 µm flowcell, a 10x objective lens with a collimator, and a 1 ml syringe-pump (flow rate 0.3 ml/min), whereas the 〉80 µm fraction was recorded using a 300 µm flowcell, a 4x objective lens without collimator, and a 5 ml syringe-pump (flow rate 0.6 ml/min). Data were acquired using the software VisualSpreadsheet (Fluid Imaging Technologies, Inc., Scarborough, ME, USA) until 10.000 images were recorded or 30 ml of the sample was investigated. An automated catalogue based on training sets developed for sponge spicules, diatoms and tephra particles was compiled to differentiate and group components with comparable characteristics in the measured sample fractions.