Correlation of the Triassic and Jurassic successions proved in the Lyme Regis (1901) borehole with those exposed on the nearby Devon and Dorset coasts

The Lyme Regis (1901) Borehole was one of numerous coal-exploration boreholes
drilled in southern England during the late 19th and early 20th centuries. It is one of
the few deep boreholes (>200 m depth) in the east Devon-west Dorset area and,
unlike more recent hydrocarbon-exploration boreholes, was continuously cored. The
borehole was sited [NGR SY 3364 9297] on the floodplain of the River Lim on the
outcrop of the Jurassic Blue Lias Formation, and was continuously cored to a final
depth of 396.85 m within the Triassic Mercia Mudstone Group. Selected samples and
some of the cores were examined by the Geological Survey geologists Jukes-Browne
and Woodward who were working in the area at the time of drilling. The former
published a description of the succession based on his and Woodward’s notes and the
driller’s log, and correlated it with the succession of Triassic and Jurassic rocks that
are almost wholly exposed in the cliffs between Sidmouth and Lyme Regis. A recent
revision of the stratigraphy of the coastal successions has enabled that proved in the
borehole to be reassessed and placed more accurately into its regional stratigraphical
context.