Cyclostratigraphy and Astrochronology of the Cryogenian Datangpo Formation in South China
Abstract:The Datangpo Formation in South China is typical of Cryogenian interglacial deposits characterized by fine-grained siltstone and mudstone. It overlies glacial diamictites of the Chang’an Formation or its correlatable units and underlies diamictites of the Nantuo Formation. The base and top of the Datangpo Formation is constrained by U-Pb ages of 662.9±4.3 and 654.5±3.8 Ma, respectively. The existing ages roughly constrain the duration of the Datangpo Formation between 2.66 and 14.14 million years. To better understand the sedimentary cycles, climate events and astrochronological signal recorded in the Datangpo Formation, we investigated the millimeter and sub-millimeter scale siltstone-mudstone rhythmites from a drillcore northestern Guizhou Province, which was paleogeographically located in a slope environment of the Yangtze platform.
High-resolution color scale and X-ray fluorescence records are obtained from the drillcore of the Datangpo Formation. Power spectrum and wavelet transform analyses of gray scale variations and chemical element contents (e.g., Si, Al, Mn/Fe, Rb/K…) reveal a hierarchy of sedimentary cycle bands of 0.59 mm, 1.18 mm, 4.92 mm, which are likely derived by the solar variation periods of 11 yr, 22 yr, 90 yr, respectively. Cyclostratigraphic study indicates that the duration of the Datangpo Formation can be estimated as 9.2 m.y., which is consistent with the existing U-Pb age constrains. These results suggest that the climate fluctuations manifested in the color scale and geochemical records of the Datangpo Formation may have been controlled by periodic solar variations during late Neoproterozoic. The average sedimentary accumulation rate of the Datangpo Formation is thus calculated as 53.6 mm/ka using the duration derived from cycle analysis.