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- ItemChronological Assessment of the Balta Alba Kurgan Loess-Paleosol Section (Romania) – A Comparative Study on Different Dating Methods for a Robust and Precise Age Model(Lausanne : Frontiers Media, 2021) Scheidt, Stephanie; Berg, Sonja; Hambach, Ulrich; Klasen, Nicole; Pötter, Stephan; Stolz, Alexander; Veres, Daniel; Zeeden, Christian; Brill, Dominik; Brückner, Helmut; Kusch, Stephanie; Laag, Christian; Lehmkuhl, Frank; Melles, Martin; Monnens, Florian; Oppermann, Lukas; Rethemeyer, Janet; Nett, Janina J.Loess-paleosol sequences (LPSs) are important terrestrial archives of paleoenvironmental and paleoclimatic information. One of the main obstacles for the investigation and interpretation of these archives is the uncertainty of their age-depth relationship. In this study, four different dating techniques were applied to the Late Pleistocene to Holocene LPS Balta Alba Kurgan (Romania) in order to achieve a robust chronology. Luminescence dating includes analysis of different grain-size fractions of both quartz and potassium feldspar and the best results are obtained using fine-grained quartz blue‐stimulated and polymineral post-infrared infrared-stimulated luminescence measurements. Radiocarbon (14C) dating is based on the analysis of bulk organic carbon (OC) and compound-specific radiocarbon analysis (CSRA). Bulk OC and leaf wax-derived n-alkane 14C ages provide reliable age constraints for the past c. 25–27 kyr. CSRA reveals post-depositional incorporation of roots and microbial OC into the LPS limiting the applicability of 14C dating in older parts of the sequence. Magnetic stratigraphy data reveal good correlation of magnetic susceptibility and the relative paleointensity of the Earth’s magnetic field with one another as well as reference records and regional data. In contrast, the application of paleomagnetic secular variation stratigraphy is limited by a lack of regional reference data. The identification of the Campanian Ignimbrite/Y-5 tephra layer in the outcrop provides an independent time marker against which results from the other dating methods have been tested. The most accurate age constraints from each method are used for two Bayesian age-depth modeling approaches. The systematic comparison of the individual results exemplifies the advantages and disadvantages of the respective methods. Taken as a whole, the two age-depth models agree very well, our study also demonstrates that the multi-method approach can improve the accuracy and precision of dating loess sequences.
- ItemMineral Magnetic Characterization of High‐Latitude Sediments From Lake Levinson‐Lessing, Siberia(Hoboken, NJ : Wiley, 2021) Scheidt, Stephanie; Egli, Ramon; Lenz, Matthias; Rolf, Christian; Fabian, Karl; Melles, MartinLevinson-Lessing Lake in northern Central Siberia is a sedimentary archive characterized by continuous, widely constant sedimentation at high rates (0.7 m ka−1 for >32 ka). This study provides the first evidence of the suitability of the lake′s sediments for paleomagnetic analyses using the 46-m-long core Co1401. Although the lowermost 8 m are disturbed, the upper 38 m of Co1401 provide the preconditions for an exceptional, high-resolution paleomagnetic record located within the tangent cylinder of the inner core. High-resolution analyses of magnetic susceptibility, anhysteretic remanent magnetization, isothermal remanent magnetization, and hysteresis parameters show largely uniform mineral magnetic properties. First-order reversal curves indicate magnetite particles in pseudo-single domain state are the main remanence carrier, supplemented by single-domain particles, originating likely from magnetotactic bacteria. Above 6.7 m, the bulk magnetic mineralogy is slightly harder than below and initial greigite formation occurs. However, the main remanence carriers are still of detrital origin.
- ItemThe Towuti Drilling Project: paleoenvironments, biological evolution, andgeomicrobiology of a tropical Pacific lake(Sapporo : IODP, 2016) Russell, James M.; Bijaksana, Satria; Vogel, Hendrik; Melles, Martin; Kallmeyer, Jens; Ariztegui, Daniel; Crowe, Sean; Fajar, Silvia; Hafidz, Abdul; Haffner, Doug; Hasberg, Ascelina; Ivory, Sarah; Kelly, Christopher; King, John; Kirana, Kartika; Morlock, Marina; Noren, Anders; O'Grady, Ryan; Ordonez, Luis; Stevenson, Janelle; von Rintelen, Thomas; Vuillemin, Aurele; Watkinson, Ian; Wattrus, Nigel; Wicaksono, Satrio; Wonik, Thomas; Bauer, Kohen; Deino, Alan; Friese, André; Henny, Cynthia; Marwoto, Ristiyanti; Ngkoimani, La Ode; Nomosatryo, Sulung; Safiuddin, La Ode; Simister, Rachel; Tamuntuan, GeraldThe 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.
- Item“Climatic fluctuations in the hyperarid core of the Atacama Desert during the past 215 ka”([London] : Macmillan Publishers Limited, part of Springer Nature, 2019) Ritter, Benedikt; Wennrich, Volker; Medialdea, Alicia; Brill, Dominik; King, Georgina; Schneiderwind, Sascha; Niemann, Karin; Fernández-Galego, Emma; Diederich, Julia; Rolf, Christian; Bao, Roberto; Melles, Martin; Dunai, Tibor J.Paleoclimate records from the Atacama Desert are rare and mostly discontinuous, mainly recording runoff from the Precordillera to the east, rather than local precipitation. Until now, paleoclimate records have not been reported from the hyperarid core of the Atacama Desert (<2 mm/yr). Here we report the results from multi-disciplinary investigation of a 6.2 m drill core retrieved from an endorheic basin within the Coastal Cordillera. The record spans the last 215 ka and indicates that the long-term hyperarid climate in the Central Atacama witnessed small but significant changes in precipitation since the penultimate interglacial. Somewhat ‘wetter’ climate with enhanced erosion and transport of material into the investigated basin, commenced during interglacial times (MIS 7, MIS 5), whereas during glacial times (MIS 6, MIS 4–1) sediment transport into the catchment was reduced or even absent. Pelagic diatom assemblages even suggest the existence of ephemeral lakes in the basin. The reconstructed wetter phases are asynchronous with wet phases in the Altiplano but synchronous with increased sea-surface temperatures off the coasts of Chile and Peru, i.e. resembling modern El Niño-like conditions.