Cyclostratigraphy and astrochronology: Case studies from China

Abstract

A high-precision geologic time scale is the essential key for understanding the Earth’s evolutionary history and geologic processes. Astronomical tuning of orbitally forced stratigraphic records to construct high-resolution Astronomical Time Scales (ATS) has led to a progressive refinement of the geologic time scale over the past two decades. In turn, these studies provide new insights regarding the durations and rates of major Earth events, evolutionary processes, and climate changes, all of which provide a scientific basis for contextualizing and predicting future global change trends. South China hosts some of the best-exposed and well-dated Neoproterozoic through Mesozoic stratigraphic sections in the world; many of which are suitable for cyclostratigraphy and calibrating the geologic time scale. In North China, several Cenozoic oil-bearing basins have deep boreholes with continuous sampling and/or well logging that enable derivation of astronomically tuned time scales for an improved understanding of basin evolution and hydrocarbon generation. This Special Issue focuses on case studies of astrochronology and applied cyclostratigraphy research using reference sections within China. In this introductory overview, we: (1) summarize all existing astrochronology studies of the Neoproterozoic through Cenozoic sections within China that have been used to enhance the international geologic time scale, (2) examine briefly the astronomically forced paleoclimate information recorded in various depositional systems and the modern techniques employed to analyze the periodicity of these signals encoded within the sedimentary record, and (3) summarize the 20 contributions to this Special Issue of Palaeogeography, Palaeoclimatology, Palaeoecology on 'Cyclostratigraphy and Astrochronology: Case studies from China’.

Triple sulfur-oxygen-strontium isotopes probabilistic geographic assignment of archaeological remains using a novel sulfur isoscape of western Europe

“…To model 87 Sr/ 86 Sr variations in human teeth, we used a published model that predicts 87 Sr/ 86 Sr ratio in bioavailable Sr across the world and its associated uncertainty [13]. Briefly, this model uses a multivariate random forest regression framework, coupling biogeoenvironmental covariates and bioavailable 87 Sr/ 86 Sr data, to predict the average 87 Sr/ 86 Sr at each pixel and its associated uncertainty (1 standard deviation).…”

“…When applying this isoscape built and calibrated on modern data, we make the assumption that the present day bioavailable 87 Sr/ 86 Sr ratio is a good estimate of the bioavailable Sr available to the individuals studied here~530-years ago. As most of the bioavailable 87 Sr/ 86 Sr data used to calibrate the model are from undisturbed areas without farming activities, we assumed that fertilizers had little impact on the predicted 87 Sr/ 86 Sr variability [13]. In addition, the geology, climate and aerosol deposition of France is believed to have changed little in the last few centuries, suggesting that bioavailable 87 Sr/ 86 Sr variability was very similar to present-day [60].…”