Raised Beaches at Hope's Nose EarthCache

Hope's Nose (and also the nearby Thatcher Rock is notable for the preservation of an interglacial raised beach deposit some metres above sea-level. This pebble, shell and sand accumulation is approximately "Ipswichian" in age, i.e. a deposit of the last interglacial. It is similar to and probably a continuation of the low level raised beach or beaches of Portland Bill which are a similar height above sea-level. The Portland raised beach has given dates, not necessarily very accurate, of 125,000 and 210,000 years. In very round figures the raised beach at Hope's Nose is of about 150 thousand years old. The exposure is 37 metres long at the SE end of the promontory. It has been suggested that the only reason that we find raised beaches at Hope's Nose and Portland (and nowhere in between these places) is because the softer intermediate coast-line has been gradually worn back, whilst the headlands have withstood the waves by reason of their hardness. Thus there must have been a time when the coast between Hope's Nose and Portland was much less embayed than it is at present. Somewhere on this ancient coast-line the waters of the Teign and the Exe flowed into the sea many miles to the south of their present exits.

The Hope's Nose raised beach has a basement bed 0.3 to 0.4 metres thick. This is composed of locally derived limestone and slate debris, varying from fairly fine gravel to boulders and angular blocks up to about half a metre long. Above is cross-bedded coarse sand, becoming progressively finer upwards. The sand has a complex composition, including limestone clasts, slate, quartz sand grains, and also skeletal carbonate grains (shell debris), and the presence of clasts of flint. The flint could have come from the Eocene gravels of the Haldon Hills and adjacent area, or from the Chalk which lies some distance offshore to the south. Another possibility, is that in Pleistocene times when the raised beach was formed there were other flint deposits in the area which have since been destroyed. Dolerite clasts have also been found in the raised beach deposits. Such grains are unlikely to survive long travel and much weathering, but there is a dolerite intrusion nearby (at Black Head) which is the most likely source of the dolerite grains.

The raised beach is calcite-cemented. Such cementation of raised beaches is fairly common in carbonate environments in Britain, as at the Gower Peninsula (on Carboniferous Limestone). The calcareous waters may have come directly from the Devonian Limestone beneath, or from shell or limestone fragments within the raised beach deposits, or possibly from calcareous hillwash deposits.