The stretch of Dorset coast between St Aldhelm's Head and Lulworth Cove will
always hold a certain fascination for S260 students. This site shares the introduction
to geology with other armchair challenges in the Isle of Skye, the Cotswolds
and Cheddar Gorge. One chilly morning some thirty members and friends gathered
on the Purbeck monocline above Tyneham to peer through the mist at a real landscape
below.
A convoy descended the steep lane to the village, now a collection of ruined
cottages that were requisitioned by the War Office in 1943. Only the church
and school house remain. Leaving the cars, we walked to Worbarrow Tout and climbed
to a point which on a clear day might have given excellent views along the coast
beyond Gad Cliff to Kimmeridge Bay and St Aldhelm's Head. The Portland Beds
at the Tout dip northwards, forming a ridge that faces a parallel Upper Chalk
ridge a kilometre and a half inland.
We took the path down to a small bay below the Tout. As the whole area is now
owned by the Ministry of Defence for military training, visitors are warned
to be aware of unexploded ammunition. While searching for fossil ostracods we
turned up a badly corroded but unused cartridge. Careful inspection with hand
lenses eventually did find some ostracods and there was also a good sample of
Purbeck Marble with remains of freshwater gastropods. We had an opportunity
at the foot of Gad Cliff for a demonstration of how to find true dip and strike.
For lunch we sat in the hazy sunshine on the rocks of Worbarrow Bay. We spent
the afternoon walking westwards round the bay beneath the extensive Wealden
clays and sands in the cliffs above. Fossils were almost entirely absent - only
a few traces of lignite and layers of iron pan could be found in the sandstone.
The beach went round as far as Cow Corner, below Upper Chalk cliffs. Fallen
blocks were a source of some echinoids and one block revealed the shapes of
several fair sized ammonites.
While a few stayed on the see if dinosaur footprints were still visible on the
other side of the bay, most of us returned to Tyneham and a chance to see the
fossil collection in the museum housed in the old village school.
Reference Material.
Topographical maps:
OS Landranger 194. Dorchester, Weymouth & surrounding area. 1:50 000.
OS Outdoor Leisure 15. Purbeck & South Dorset. 1:25 000.
Geological Maps:
BGS Portland. 1:250 000. Solid geology. The New Series includes the Continental
Shelf.
BGS sheet 341/342. West Fleet & Weymouth. 1:50 000. Solid and Drift edition.
The current edition does not show submarine geology, which may be an advantage
as the map is easier to read without it.
BGS sheet 342 (East) and part of 343. Swanage. 1:50 000. Solid and Drift edition.
Like the smaller Portland area map, this sheet includes submarine detail.
There is a detailed description of the geology of Worbarrow Tout by Paul Ensom
in Coast and Country. Geology Walks in and around Dorset. Dorset Geologists'
Association 2003.
Geoffrey S Dearn