TERTIARY EROSION MAGNITUDES IN THE EAST MIDLANDS SHELF, ONSHORE UK

Sonic velocities from the Upper and Middle Chalk, the Kimmeridge Clay, the Lias and the Bunter Sandstone were used to quantify apparent eros ion (i.e. amount of missing section) in the Welton-1 and Cleethorpes-1 wells of the East Midlands Shelf, onshore UK. Apparent erosion was de termined with reference to sonic velocities in 150 wells the UK Southe rn North Sea area. Apparent erosion at Cleethorpes-1 is estimated as 1 .4 km (from the Kimmeridge Clay, Lias and Bunter Sandstone) and 1.6 km (from the Upper and Middle Chalk), and at Welton-1 as 1.6 km (from th e Bunter Sandstone) and 1.7 km (from the Lias). The consistency of res ults from the different units analysed increases confidence in the res ults with respect to compaction studies based on a single stratigraphi c unit. Estimates of missing section in this study are generally great er than those previously published for the East Midlands Shelf, but th ey are consistent with recent estimates from apatite fission track ana lysis.