Lydney Cliff
Also within
Condition (Natural England)
| Unit | Feature | Condition | Area (ha) | Assessed |
|---|---|---|---|---|
| SO653017 | — | Favourable | 8.93 | 2011-10-25 |
| SO653019 | — | Favourable | 2.97 | 2011-10-25 |
Climate exposure
This is about exposure to a nationwide pressure this habitat type carries — not a verdict on this site's own management.
Coastal habitats are exposed to sea-level rise and storm erosion. Where hard sea defences sit behind them, there's nowhere landward to retreat to — a squeeze that keeps compressing the habitat no matter how well it's managed.
Geology & landscape
Geological Feature: Rock Outcrop · Geological Period: Devonian, Silurian · Rock Type: Conglomerate, Limestone, Sandstone, Shale
Landscape processes: Coastal, Fluvial
Description
Description This site contains exposures in the topmost Raglan Marls equivalent to the lower part of the Red Marls of Lower Devonian age, up to the level of the Psammosteus Limestone. The section includes several calcrete profiles with a variety of pseudo anticline structures developed in the more mature profiles and a complex sand body which probably formed as a fluvial distributary channel. Fish fragments occur in the sandstone and the only bivalves known from the tower Old Red Sandstone have been found in the shales. The outcrop is important for assessing the extent of marine tidal influence on the shale rich sequence in the Lower Old Red Sandstone below the Psammosteus Limestone. The calcretes here have some of the best developed pseudo anticlines in the British Old Red Sandstone and this locality was one of those used in the first recognition of calcrete soils in the geological record. Two important fish beds also occur here, amongst several fish bearing horizons in a sequence of Upper Silurian Lower Devonian strata. One of the fish beds contains species of cephalaspids and cyathaspids together with bivalves molluscs. This assemblage is considered to be proof for a brief marine incursion within a sequence of otherwise predominantly estuarine to fluvial environments. This is highly unusual and atypical for fish beds of this age. The other fish beds here are all fluvial in origin and include the so called Fish Conglomerate. Together they yield Protopteraspis leathensis, Sabrina canthusarcuatus and species of Traquairaspis, Tesserapis, Antlaspis, Corvaspis and a Turminiapagei theoldont assemblage. This is a mixture of species which elsewhere occurs both above and below the Silurian Devonian boundary. This is the only extant locality for Sabrinacanthus arcuatus, the only species of a genus of climatiid acanthodian, described from disarticulated specimens of pectoral girdle and spine.