Terrestrial and freshwater deposits
Two sections from Early Cretaceous lacustrine strata of the Xiagou Formation from the Changma Basin in Gansu Province, China, are correlated based on their carbon isotopic compositions of bulk sedimentary organic matter and carbonate, as well as carbonate oxygen-isotopic compositions. The samples were collected from fossiliferous strata, which contain well-preserved Cretaceous bird remains. The sections are primarily correlated based on a two-step increase in δ13Corg with an overall magnitude of c. 12.5‰. The stratigraphic variations in carbon isotopes within the two lacustrine sections are correlated with global carbon isotope variations C3–C7 based on marine carbon isotope records. This correlation places the Xiagou lacustrine strata in this locality within the early Aptian Stage, specifically, the Selli Equivalent, which is associated with Ocean Anoxic Event 1a.
Figures & Tables
Isotopic Studies in Cretaceous Research
The Cretaceous was a period characterized by very warm climate, oceanic anoxic and oxic events and enhanced volcanic activity. The end of the Cretaceous is punctuated by a well-documented asteroid impact and the extinction of, among other groups, the dinosaurs. This volume elucidates various aspects of Cretaceous marine and continental environmental conditions. The articles in this book present a broad range of interdisciplinary contributions, which are grouped into sections on marine environments(including anoxic and oxic events, volcanism and the Cretaceous–Palaeocene boundary); mixed marine–freshwater environments and continental records. The isotopic data are combined with further geochemical, palaeontological, lithological and mineralogical proxies. The interdisciplinary approach offered here gives a solid investigation base for this fascinating period. There are examples from Europe, Asia, South and North America, and from the Early Cretaceous to the Cretaceous–Paleogene boundary.