Overview 
The upper layer Upper Lias Junction Bed is found as a thin dull white-pink fine-grained limestone overlaying, and cemented to, the lower (and older) layer, the Middle Lias Marlstone Rock Bed. It is a condensed deposit indicating shallowing of the surrounding sea, with several non-sequences and planed surfaces, containing ammonites representative of several horizons on the Lower and lower Upper Toarcian. The bed appears to consist of four different ages of formation. The lowest layer contains ammonites from the topmost zone of the Middle Lias. The other layers include ammonites from the Upper Lias. These four layers separate along planes which appear to have been eroded by sea action before deposition of the next layer.

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According to 'Jenkyns and Senior', there is evidence for a minor palaeofaulting of this bed in the Eype Mouth area. This is the 'youngest' formation currently covered by this website. 

Fossils 
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 Zones and sub-zones 

 

Zones

Grammoceras thouarsense
Haugia variabilis
Hildoceras bifrons
Harpoceras falciferum
Dactylioceras tenuicostatum

after House

Beds and fossils 


'Layer' Geology Notes Fossils
Striatulum Hard grey-yellow limestone or earthy marl with limestone nodules. Top of bed planed off by erosion. Traces of variabilis Subzone welded to undersurface.
Bifrons Hard limestone mottled yellow pink-red. Fine-grained to conglomeratic. Well marked erosion plane separates this layer from above layer. Ammonites Hildoceras bifrons and Dactylioceras commune.
Falcifer Tough yellow-pink limestone, sometimes mottled red or green. Usually rests on planed-off top of the Marlstone Rock Bed. Ammonite Dactylioceras commune.

 

Bed photographs

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A piece of Junction Bed picked up from the western end of the beach at Eype Mouth. The upper surface of the bed shows several thin layers, believed to be the fossilised remains of algal growths (the scum from the surface of a drying out lake?). Embedded within the bed are many Ammonite and shell fossils, as well as small pebbles.

 Other Junction Bed references