Mansands Beach, Brixham, Torbay, Devon, England, UKi

Regional Level Types
Mansands Beach	Beach
Brixham	Town
Torbay	Unitary Authority
Devon	County
England	Constituent Country
UK	Country

In the headland (known as Crab Rock Point ) south of the beach a small trial has been dug into the soft mudstones just above the high tide mark. The entrance is little more than adult shoulder width and 1m high whilst the horizontal extent is only 2m. No mineralisation is visible in the trial other than some coloured staining in the walls.

However, on the seaward end of this thin finger of the headland extensive ochreous yellow staining is apparent and following the slim inlet back to the point opposing the trial there is a mass of predominantly white quartz in the wall of the inlet a little above high tide mark, with both ochreous yellow staining and small patches of green discoluoration from copper secondary weathering.

The inlet follows a high angle thrust fault with movement from the south and in the opposing (southern) wall of the inlet there is another ocherous patch.

The rocks are very thin beds of mudstone within the Bovisand Formation (which also includes coarser sediments such as sandstones) and in places ripple marks have been preserved from when the sediments were deposited in a shallow marine environment some 400 million years ago. The Variscan Orogeny (circa 320 million years ago) was probably responsible for inclining the beds.

The ochre deposit is perhaps 3m by 0.3m, but it lies in the same plane as the sediment beds. However, the deposit can be followed horizontally back into the cliff as the cliff is eroded away in other places exposing the deposit. Not only that but the lengthways orientation of the deposit has the same orientation as the ripple marks in the sediments.

It is conceivable that in the original shallow sea there was a shore line either to the right or left of the photo as indicated by the ripple marks, which as on a present day beach generally run lengthways along the beach. However, also running lengthways with the shore were troughs in the sediment and into these have collected the sources of iron and copper. Perhaps grains of metal minerals were being washed down a river along with the sand and mud that make up the rocks and then because the metal rich grains were much denser than sand or mud they would sifted into hollows in the sea bed to form 'alluvial' deposits.

In the later mountain forming orogeny the metal mineral grains dissolved into solution and later recrystallised as the deposits that are now present within the quartz.

Personal observation, July, 2015

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