Search Results
The Cyclostratigraphy Intercomparison Project (CIP): consistency, merits and pitfalls
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.
Organic carbon burial is paced by a ∼173-ka obliquity cycle in the middle to high latitudes
2021, Huang, He, Gao, Yuan, Ma, Chao, Jones, Matthew M., Zeeden, Christian, Ibarra, Daniel E., Wu, Huaichun, Wang, Chengshan
Earth’s climate system is complex and inherently nonlinear, which can induce some extraneous cycles in paleoclimatic proxies at orbital time scales. The paleoenvironmental consequences of these extraneous cycles are debated owing to their complex origin. Here, we compile high-resolution datasets of total organic carbon (TOC) and stable carbon isotope (δ13Corg) datasets to investigate organic carbon burial processes in middle to high latitudes. Our results document a robust cyclicity of ~173 thousand years (ka) in both TOC and δ13Corg. The ~173-ka obliquity–related forcing signal was amplified by internal climate feedbacks of the carbon cycle under different geographic and climate conditions, which control a series of sensitive climatic processes. In addition, our new and compiled records from multiple proxies confirm the presence of the obliquity amplitude modulation (AM) cycle during the Mesozoic and Cenozoic and indicate the usefulness of the ~173-ka cycle as geochronometer and for paleoclimatic interpretation.