Date and Time
Bath Royal Literary and Scientific Institution, 16-18 Queen Square, Bath BA1 2HN
Much of the marine stratigraphic record, and the history of evolution and climate change archived within it, was deposited in expansive epicontinental seas for which there are no suitably scaled modern-day analogues (Fig. 1).
Figure 1. Palaeobathymetric reconstruction of the Hettangian Stage (Lower Jurassic) of the Laurasian Seaway. Palaeogeographic configuration is modified from Dercourt et al. (2006) and paleodepths are approximately constrained from a detailed literature review.
The tides in these seaways have been variously argued as being either slight as a result of frictional damping or high as a result of resonant amplification. Tides are important because they influence sediment architecture and water-body mixing. Numerical models have supported the notion of frictional damping but outcrop sedimentology has identified the presence of abundant tidally modified sedimentary rocks in ancient epicontinental sea deposits.
Recent work using the Imperial College Ocean Model (ICOM), a fully hydrodynamic, finite element ocean model, shows that the majority of ancient epicontinental seas were likely to have been micro-tidal (tidal range of up to 2 m). Detailed modelling has, however, shown that local amplification and elevated tidal bed shear stress typically occurs as a result of resonance and paleogeographic funneling in embayments and over shallow platforms. Dr. Allison will introduce the model and give an overview of its novelty and utility for a range of broadly scaled applications. The latter will be illustrated with a series of verification exercises that includes modelling tidal range, stratification and bed shear stress on the NW European Shelf. Ongoing work is assessing the impact of amplified currents on seasonal stratification in the Lower Jurassic seaway of NW Europe and provisional results will be presented. This work has broad applicability to our understanding of sediment dynamics, nutrient cycling and biodiversity in ancient epicontinental seaways.
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