2019, Sinnesael, Matthias, De Vleeschouwer, David, Zeeden, Christian, Batenburg, Sietske J., Da Silva, Anne-Christine, de Winter, Niels J., Dinarès-Turell, Jaume, Drury, Anna Joy, Gambacorta, Gabriele, Hilgen, Frederik J., Hinnov, Linda A., Hudson, Alexander J.L., Kemp, David B., Lantink, Margriet L., Laurin, Jiří, Li, Mingsong, Liebrand, Diederik, Ma, Chao, Meyers, Stephen R., Monkenbusch, Johannes, Montanari, Alessandro, Nohl, Theresa, Pälike, Heiko, Pas, Damien, Ruhl, Micha, Thibault, Nicolas, Vahlenkamp, Maximilian, Valero, Luis, Wouters, Sébastien, Wu, Huaichun, Claeys, Philippe

Cyclostratigraphy is an important tool for understanding astronomical climate forcing and reading geological time in sedimentary sequences, provided that an imprint of insolation variations caused by Earth’s orbital eccentricity, obliquity and/or precession is preserved (Milankovitch forcing). Numerous stratigraphic and paleoclimate studies have applied cyclostratigraphy, but the robustness of the methodology and its dependence on the investigator have not been systematically evaluated. We developed the Cyclostratigraphy Intercomparison Project (CIP) to assess the robustness of cyclostratigraphic methods using an experimental design of three artificial cyclostratigraphic case studies with known input parameters. Each case study is designed to address specific challenges that are relevant to cyclostratigraphy. Case 1 represents an offshore research vessel environment, as only a drill-core photo and the approximate position of a late Miocene stage boundary are available for analysis. In Case 2, the Pleistocene proxy record displays clear nonlinear cyclical patterns and the interpretation is complicated by the presence of a hiatus. Case 3 represents a Late Devonian proxy record with a low signal-to-noise ratio with no specific theoretical astronomical solution available for this age. Each case was analyzed by a test group of 17-20 participants, with varying experience levels, methodological preferences and dedicated analysis time. During the CIP 2018 meeting in Brussels, Belgium, the ensuing analyses and discussion demonstrated that most participants did not arrive at a perfect solution, which may be partly explained by the limited amount of time spent on the exercises (∼4.5 hours per case). However, in all three cases, the median solution of all submitted analyses accurately approached the correct result and several participants obtained the exact correct answers. Interestingly, systematically better performances were obtained for cases that represented the data type and stratigraphic age that were closest to the individual participants’ experience. This experiment demonstrates that cyclostratigraphy is a powerful tool for deciphering time in sedimentary successions and, importantly, that it is a trainable skill. Finally, we emphasize the importance of an integrated stratigraphic approach and provide flexible guidelines on what good practices in cyclostratigraphy should include. Our case studies provide valuable insight into current common practices in cyclostratigraphy, their potential merits and pitfalls. Our work does not provide a quantitative measure of reliability and uncertainty of cyclostratigraphy, but rather constitutes a starting point for further discussions on how to move the maturing field of cyclostratigraphy forward.

2017, Wagner, Bernd, Wilke, Thomas, Francke, Alexander, Albrecht, Christian, Baumgarten, Henrike, Bertini, Adele, Combourieu-Nebout, Nathalie, Cvetkoska, Aleksandra, D'Addabbo, Michele, Donders, Timme H., Föller, Kirstin, Giaccio, Biagio, Grazhdani, Andon, Hauffe, Torsten, Holtvoeth, Jens, Joannin, Sebastien, Jovanovska, Elena, Just, Janna, Kouli, Katerina, Koutsodendris, Andreas, Krastel, Sebastian, Lacey, Jack H., Leicher, Niklas, Leng, Melanie J., Levkov, Zlatko, Lindhorst, Katja, Masi, Alessia, Mercuri, Anna M., Nomade, Sebastien, Nowaczyk, Norbert, Panagiotopoulos, Konstantinos, Peyron, Odile, Reed, Jane M., Regattieri, Eleonora, Sadori, Laura, Sagnotti, Leonardo, Stelbrink, Björn, Sulpizio, Roberto, Tofilovska, Slavica, Torri, Paola, Vogel, Hendrik, Wagner, Thomas, Wagner-Cremer, Friederike, Wolff, George A., Wonik, Thomas, Zanchetta, Giovanni, Zhang, Xiaosen S.

This study reviews and synthesises existing information generated within the SCOPSCO (Scientific Collaboration on Past Speciation Conditions in Lake Ohrid) deep drilling project. The four main aims of the project are to infer (i) the age and origin of Lake Ohrid (Former Yugoslav Republic of Macedonia/Republic of Albania), (ii) its regional seismotectonic history, (iii) volcanic activity and climate change in the central northern Mediterranean region, and (iv) the influence of major geological events on the evolution of its endemic species. The Ohrid basin formed by transtension during the Miocene, opened during the Pliocene and Pleistocene, and the lake established de novo in the still relatively narrow valley between 1.9 and 1.3 Ma. The lake history is recorded in a 584 m long sediment sequence, which was recovered within the framework of the International Continental Scientific Drilling Program (ICDP) from the central part (DEEP site) of the lake in spring 2013. To date, 54 tephra and cryptotephra horizons have been found in the upper 460 m of this sequence. Tephrochronology and tuning biogeochemical proxy data to orbital parameters revealed that the upper 247.8 m represent the last 637 kyr. The multi-proxy data set covering these 637 kyr indicates long-term variability. Some proxies show a change from generally cooler and wetter to drier and warmer glacial and interglacial periods around 300 ka. Short-term environmental change caused, for example, by tephra deposition or the climatic impact of millennial-scale Dansgaard-Oeschger and Heinrich events are superimposed on the long-term trends. Evolutionary studies on the extant fauna indicate that Lake Ohrid was not a refugial area for regional freshwater animals. This differs from the surrounding catchment, where the mountainous setting with relatively high water availability provided a refuge for temperate and montane trees during the relatively cold and dry glacial periods. Although Lake Ohrid experienced significant environmental change over the last 637 kyr, preliminary molecular data from extant microgastropod species do not indicate significant changes in diversification rate during this period. The reasons for this constant rate remain largely unknown, but a possible lack of environmentally induced extinction events in Lake Ohrid and/or the high resilience of the ecosystems may have played a role. © Author(s) 2017.