The Late Cretaceous Epoch, which lasted from 100 to 65 Ma, was a time of global sea-level rise, which reached a maximum at the beginning of the middle Turonian (Haq et al. 1987, 1988). The fully marine warm conditions on the shelf seas gave rise to abundant blooms of calcarous nannoplankton that largely formed the resultant Chalk we see today. In addition to the coccoliths, the microfauna contains both plank-tonic and benthonic foraminifera, calcispheres, ostra-cods and the debris of macrofaunal elements, such as inoceramids, echinoids and bryozoans. Within the chalk are horizons of marls and flints, the former from periods of higher clastic/carbonate deposition, and the latter from precipitation of siliceous-rich groundwaters, mostly in burrow systems.
Although the Late Cretaceous seas covered the majority of the British Isles, with the exception of the massifs in the positions of present-day NW Scotland, Cumbria, Cornwall, SW Wales and SW Ireland, much of the chalk deposited there has been removed by later erosion. The present-day outcrop is limited to a broad area from eastern Yorkshire through to Lincolnshire, a broad band from Norfolk to Dorset, then eastwards through Hampshire, and two swathes across the North and South Downs flanking The Weald. There are some chalk outliers in Devon and chalk is also preserved beneath the Tertiary basalts of Northern Ireland (Fig. 1). The stratigraphical coverage of the Late Cretaceous in Britain is largely complete from the Cenomanian to the Campanian; however, only part of the Early Maastrichtian Stage is