The Cretaceous Period in 2023 – progress and challenges

Over the past 30 years, our knowledge of Cretaceous stratigraphy and timescale has expanded exponentially. This has been based partly on the greater refinement of biostratigraphy, including the utilisation of groups of fossils previously poorly known or ignored (microcrinoids, inoceramid bivalves, diverse microfossil groups) and also the development of geochemical and geophysical stratigraphies, most notably stable carbon isotope- and magnetostratigraphy. These two methodologies have enabled previously impossible correlations to be made, independent of facies and sometimes in the absence of biostratigraphical evidence. The identification of orbital cycles in Cretaceous sediments, integrated with new radiometric dates, now provides a high-resolution timescale for intervals of the Cretaceous. Work continues apace to extend and refine the timescale and integrate this with new stratigraphical data. Additionally, data generated primarily for the purpose of correlation, such as stable carbon isotope curves, provide direct evidence of the Cretaceous carbon cycle and allow a better understanding of palaeoenvironmental changes.