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- ItemThe Cyclostratigraphy Intercomparison Project (CIP): consistency, merits and pitfalls(Amsterdam [u.a.] : Elsevier, 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, PhilippeCyclostratigraphy 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.
- ItemLoess-Palaeosol Sequences in the Kashmir Valley, NW Himalayas: A Review(Lausanne : Frontiers Media, 2020) Dar, Reyaz A.; Zeeden, ChristianLoess deposits and intercalated palaeosols are widespread in the Quaternary record, and these have been extensively used to gain insights into continental paleoclimatic and paleo-environmental conditions and changes. Especially over Eurasia, loess geoarchives play an important role for our understanding of past changes. Loess covers almost 500 km2 of the Kashmir Valley in north-western India, it occurs dominantly in plateau positions, but also on terraces and sometimes forms slope deposits with thicknesses ranging from several to more than 20 m. For the time being, however, the timing of the initiation of the loess accumulation, the provenance, the grain size composition and also the paleo-environment have not been studied systematically and yet only little quantitative data is available. Yet it is clear that deposition rates are at least comparable to European loess, and that the presence of multiple palaeosols intercalated in the loess can provide valuable information on the history of the region. The limited available data hinders regional and continental correlation, and tapping its value as archive of past environmental changes in this sensitive region with influence from Westerlies and the Indian Monsoon. However, several characteristic palaeosol patterns can be traced throughout the Kashmir valley, which provide stratigraphic information. Several studies investigate physical and chemical properties of the loess-paleosol sequences and conclude to its aeolian origin and recording of past climates. The intensity of soil formation phases is traced through various proxies in low resolution and yet without conclusive age control. Here we review the exiting literature, available data, and interpretations from loess-palaeosol sequences in the Kashmir Valley. These are placed in the context of our own observations and loess from the Indian subcontinent. © Copyright © 2020 Dar and Zeeden.