Cyclostratigraphy under the Control of Orbital Periods: A Case Study of the Late Ordovician-early Silurian Strata

Lang, J.; Zhang, T.; Zhu, H.; Zeng, J., and Liang, X., 2018. Cyclostratigraphy under the control of orbital periods: A case study of the late ordovician-early silurian strata. In: Liu, Z.L. and Mi, C. (eds.), Advances in Sustainable Port and Ocean Engineering. Journal of Coastal Research, Special Issue No. 83, pp. 369–374. Coconut Creek (Florida), ISSN 0749-0208.To study the Milankovitch cycles in the late Ordovician-early Silurian strata, this study uses the fast Fourier transform mathematical function and one-dimensional continuous wavelet transform provided by MATLAB software to analyse the natural gamma-ray logging curve of the Wufeng-Longmaxi Formation in the study area. The results show that the Wufeng-Longmaxi Formation widely preserves the (Milankovitch) depositional cycles of 405 ka, 100 ka, 42 ka, and 21 ka. The primary cyclostratigraphy is controlled by paleoclimate. The thicknesses of cyclostratigraphies induced by eccentricity, obliquity and precession are approximately 12.208 m, 2.616 m, 1.221 m, and 0.621 m, respectively. The effect of the eccentricity period is the largest, of which the time span calculated by spectrum analysis and wavelet transform is generally consistent. The mathematical functions in MATLAB simplify the processes of mathematical operations, providing an effective approach for the future study of cyclostratigraphy.