7 Stagnogley

Stagnogley soils are ‘slowly permeable’ (badly drained!),  seasonally waterlogged soils.  They are sometimes called ‘surface water gleys’ because the cause of the drainage problem is the rainwater not being able to drain through quickly enough.  These are usually clay soils.  In cold, wet climates a stagnohumic gley (also called a ‘peaty gley’) develops, namely a stagnogley with a peaty surface horizon.   Both soils are characterised by mottling (patchy coloration) which becomes more obvious and intense with depth until a uniform bluish-grey horizon is reached.   The lack of oxygen penetration into the soil causes the iron to be reduced and take on the bluish colours.   Mottling indicates a zone through which the water table fluctuates, whereas the uniform bluish horizon is below the permanent water table.   Some stagnogleys are due to a layer of low permeability within the soil, and may be better-drained beneath.

Location:  Lleiniog, Beaumaris, Anglesey.  Proceed along B5109 out of the town, turn right along an unclassified road sign-posted to Penmon, and park where the road comes down to the sea at Lleiniog SH621792.  Walk (to the right) along the shore back towards Beaumaris, past a prominent limestone boulder. Typical stagnogley soils (Salop Series) are visible at the top of the low cliff in various places, the best examples are beyond the small cave.  Parent material; reddish till derived from local and Triassic rocks:  land use grassland


0-20     Ap      greyish-brown topsoil, sandy clay loam, moderately stony, well-developed granular structure, abundant fine roots, sharp, wavy boundary.

20-45   Eg      brownish, slightly mottled, clay loam, slightly stony, moderately-developed subangular blocky to prismatic structure.  Gradual boundary

45-70   Btg     reddish-brown, mottled, clay, slightly stony, angular blocky to prismatic structure. Gradual boundary

70-95   BCg    dark reddish-brown prominently mottled (orange and greyish), clay, coarse angular blocky structure. Gradual boundary

95  Cgk dark reddish-brown, prominently mottled, clay, with greenish/grey faces to peds, pinkish carbonate concretions.

(photo : John Conway)

These soils are seen at Lleiniog developed on the Irish Sea Till


(photo : John Conway)

This soil type can also be seen at various locations around the east coast of Anglesey.  A good place to visit is Trwyn Dwlban [SH532820] on the edge of Red Wharf Bay [turn off the A5025 signposted Red Wharf Bay and park on the coast] where the till overlies the famous outcrop of carboniferous limestone and sandstone pipes.

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