Abstract This chapter reviews sequence stratigraphic concepts and methodologies and presents an approach that is most applicable to the North Sea Jurassic, based on the concept of genetic sequence stratigraphy. The concept of depositional sequences, comprising rock units bounded by unconformities, has been developed from the late nineteenth century up to the present day. Many different studies have been carried out on North Sea Jurassic sequence stratigraphy, from the early 1980s to the present day and involving a range of different approaches. Many authors have adopted the J sequence approach that was first published in the early 1990s; however, a number of alternative North Sea Jurassic sequence schemes have also been described. A close relationship existed between tectonics and sequence boundary development, particularly during the Middle–Late Jurassic in the North Sea region. Several of the major unconformities that are known to be of regional extent can be directly related to significant tectonic phases. Other sequence boundaries, for which a tectonic control is not evident, for example, particularly in the Early Jurassic, were potentially driven by glacio-eustatic cycles, which may have been controlled by orbital forcing cycles.

Abstract The Kasimovian was a time of ecological upheaval and large-magnitude changes in palaeoclimate. Referred to as the ‘collapse’ of the palaeotropical rainforests, the Kasimovian is marked by rapid changes in megafloral communities and associated ecosystem effects on vertebrates and invertebrates. p CO 2 variation coincided with these ecological catastrophes, varying between pre-industrial levels (PAL) to 2×PAL on 10 5 year timescales. Our understanding of the carbon cycle perturbations that affected p CO 2 and the connection of these climate-forcings to the terrestrial upheaval of palaeotropical rainforests remains a grand challenge. Here, the effects of palaeosol accumulation and/or degradation on the terrestrial carbon cycle during the Kasimovian is assessed. Palaeosols are surveyed from ice-free depositional basins on Pangaea and assessed for palaeolandscape equilibrium. An orbital framework is developed in order to understand the relationships of palaeosols, the carbon cycle, and insolation. Based on these analyses a key time interval emerges in the early Kasimovian. This time interval records a shift in palaeolandscape equilibria, terrestrial carbon cycling, and orbital forcing. The carbon cycling and landscape equilibria are eccentricity-paced; however, predominance of short eccentricity and obliquity throughout this interval indicates that the changes to palaeosols and the locus of carbon burial may have acted as a stochastic process.

Abstract Cyclostratigraphy is an important tool for understanding astronomical climate forcing and for reconstructing geological time in sedimentary sequences, provided that an imprint of insolation variations caused by Earth's orbital eccentricity, obliquity and precession is preserved (Milankovitch forcing). Understanding astronomical climate forcing has proven fundamental for the study of Cenozoic climate systems and the construction of high-resolution continuous time scales (astrochronologies). Pre-Cenozoic astrochronologies face several challenges: (1) uncertainties in the deep-time astronomical solutions and parameters; (2) less complete and less well preserved strata; and (3) the sparsity of geochronologic anchor points. Consequently, Paleozoic astrochronologies are typically based on identification of the stable 405 kyr eccentricity cycle instead of shorter astronomical cycles. Here, a state-of-the-art review of Ordovician cyclostratigraphy and astrochronology is presented, as well as suggestions on their robust application in an Ordovician context. Ordovician astronomically driven climate dynamics are suggested to have influenced processes like glacial dynamics, sea-level variations and changes in biodiversity. Ordovician cyclostratigraphic studies can help to construct high-resolution numerical time scales, ideally in combination with high-quality radio-isotopic dating. As such, cyclostratigraphy is becoming an increasingly important part of an integrated stratigraphic approach to help disentangle Ordovician stratigraphy and palaeoenviromental changes.