Little Settlands - incompetent deformation 1

Structural geology of Little Haven and The Settlands

The cliffs from Little Haven to Broad Haven (and northward) display a spectacular range of geological structures, folding, faulting and thrusting, mainly in the Lower Coal Measures. The relatively weak mudstone and shale-dominated sequences show much incompetent deformation: tight, thrusted and overturned folds, in contrast to the thicker, stronger, sandstones which have formed relatively open and concentric folds.

Immediately north of The Rain headland is a small embayment: 'Little Settlands'. Here, a chaotic looking series of disturbed bedding and downward-facing small folds are in contact with a thin coal. The whole sequence is inverted, the inversion being a continuation of the overturned structure seen on The Rain and the northern end of the main Settlands bay, e.g. on the left in the previous photo here:


Downward-facing means that the way-up, younging direction, of the folds is downwards, rather than the normal upwards. So the structure at the lower right (see note) which looks like an overturned anticline is actually an inverted syncline. The evidence for the way up is provided by small scale (too small to be seen clearly in this photo) sedimentary slump and load casts on the bases of sandy layers within the predominantly shale and mudstone sequence. The inverted folds are thought to have been initiated immediately prior to the main folding and thrusting event.

The coal is completely inverted ('up' is to down to the left) and separated from the inverted folds by a prominent shear plane just below the bottom of the walking stick and running up towards the upper left.

The stick is 90 cm long.