Overview 

Although formed during a time when the sea level was fairly deep and often anoxic, the Coinstone Stone bed, the Stellare Nodule Bed (Bed 88f) were formed during a time when the sea had shallowed quite significantly, combined with erosion leading to some non-sequence occurring.

Fossils 

Crinoid Pentacrinites fossilis

The ammonite Asteroceras obtusum is also known as the Obtuse Star Ammonite, the Asteroceras stellare is also known as the True Star Ammonite and the Microderoceras birchi is known locally as both the Tortoise ammonite and the White Ammonite. Other ammonites found in this bed include Oxynoticeras oxynotum and Echioceras raricostatum.

 Zones and sub-zones 

Beds and fossils 

Possible non-sequence bed located between here

The horizons forming bed 83, are collectively known 
as the 'Obtusum Shales'. 

Bed photographs

This photo shows the location of the Black Ven Marl bed 80, the Lower Cement Bed, where is appears at the top of the cliff to the west of the Charmouth seafront.

This is a piece of Black Ven Marl (probably Bed 81a-81h). It was recovered from the talus slope just below the Upper Cement Bed (Bed 82). The surface of the marl shows a layer of poorly preserved and crushed fossils, mainly Ammonites and Devils Toenails.

This is a lenticular nodule from the Coinstone Bed (Bed 89). The top side of this lenticular limestone nodule is covered by a layer of darker limestone. This upper layer appears to be riddled by holes (it is believed that these were formed by burrowing animals, prior to the sedimentary rock hardening up).

This is a piece of a Stellare Nodule (Bed 88f) that has been previously opened by a fossil collector. Instead of containing a fossil, this nodule just had brown Zinc Sulphide (Blende) crystals. The entire nodule measured over 19 inches in diameter.

This photo is a piece of Limestone with Brachiopods Bed (Bed 87). It shows a cluster of brown Zinc Sulphide (Blende) crystals that had formed in a crevice within the specimen.

This is a piece of Upper Cement Bed (Bed 82). During the severe winter storms of 1996/97, a large number of big pieces of this bed, some of them up to 2m square, were landslipped down onto the beach, a drop of some 30 feet!

This is a piece of the Lower Cement Bed (Bed 80). In this specimen: no crystals, no fossils, no nothing - just a lump of very hard limestone.

Formed by the Lower Cement Bed [Bed 80], the Black Rock Reef can be seen exposed between the low and high tide marks. Normally the surface of the bed is well exposed and can be walked upon, however, following severe storms, parts of the reef can be covered by several feet of sand, with only the tops of the reef showing.

The terraces covering the face of Black Ven indicate the large number of landslips that have happened. Shales with Beef, Black Ven Marls and Belemnite Marls are all exposed.

This is a Flatstone in the process of being excavated out from the Black Ven Marl. The wellington boot gives some idea of the size of the stone. Further digging proved the stone to be twice the depth seen here. Once excavated the stone was 'opened' but alas, contained no large examples of the Asteroceras Turneri ammonite.

 Other Black Ven Marl references

• Ian West's 'Fossils of the Lias'

  • http://www.soc.soton.ac.uk/SOES/STAFF/imw/liasfos.htm