Earthwatcher

Earthwatcher deceased

Posted: 02 Apr 2019


Taken: 27 Sep 2018

1 favorite     0 comments    111 visits

1/160 f/7.1 15.0 mm ISO 200

Canon EOS 600D

EF-S15-85mm f/3.5-5.6 IS USM


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Keywords

beach
Lower Coal Measures
Little Haven
The Settlands
incompetent deformation
faults
Pembrokeshire
Wales
geology
folds
coast
cliffs
rocks
thrusts


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Little Haven - The Settlands; detail of overturned anticline

Little Haven - The Settlands; detail of overturned anticline
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.

This is a close-up view of the prominent overturned, nearly recumbent, chevron-style anticline at the northern end of The Settlands. The relatively weak mudstone and shale sequence has deformed incompetently, with some thickening in the hinge zone.The dark shale bed just below the centre of the photo is at the horizon of the Amman Marine Band.

The overturned northern limb of the fold is separated from the nearly horizontal upper limb by a near-horizontal thrust. Below this thrust, disturbed, separate, repeated portions of the hinge zone are visible, one of which has developed axial planar cleavage in the grey seatearth with brown ironstone bands and nodules.

Above the anticline, another significant, higher, thrust has carried more sandy beds over the top.

See notes for individual descriptions of areas on the photo.

Fred Fouarge has particularly liked this photo


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