SN5882 : Aberystwyth Grits - bedding

near to Aberystwyth, Ceredigion/Sir Ceredigion, Great Britain

Aberystwyth Grits - bedding
Aberystwyth Grits - bedding
The cliffs of the section of coast north of Aberystwyth towards Clarach show alternating light and dark grey layers. The lighter rock is fine-grained sandstone and siltstone, while the darker parts are coarser-grained mudstone. The same sequence is repeated many times. The section shown here is about 1.60m in height. Annotated version of this image: LinkExternal link

The alternating pattern arises from a deposition of sediment from under-water avalanches occurring on the continental shelf. This location was at the time (Silurian period) part of the ocean floor. These avalanches are known as turbidity currents. Each deposition event comprises an early deposition of sand, followed by finer-grained silt and finally fine clay-type (mud) particles.
Since this area of ocean floor was relatively distant from the source of the turbidity currents, the sandstone layer is only present for some of the beds, e.g. the thicker light one near the bottom. Further southwest, in Pembrokeshire, nearer the Silurian continental shelf, sand and silt outweigh the mudstone component. The ideal sequence of turbidites is known as the Bouma sequence LinkExternal link .
Craigyfulfran GCR site
The coastal stretch north of Aberystwyth towards Clarach is known for its exposed turbidite beds LinkExternal link and for their intricate folding and faulting patterns LinkExternal link . The name of the site originates from a sea stack located on the foreshore (links above are to the Geological Conservation Review's site reports).
Geological Conservation Review
The Geological Conservation Review (GCR) is a database of geological reference sites in Great Britain. It is published by the Joint Nature Conservation Committee (JNCC) in the form of site reports collected in printed volumes covering different geological periods and topical areas such as fossils, minerals or geomorphology. The site reports are gradually put online in a searchable database LinkExternal link .
Creative Commons Licence [Some Rights Reserved]   © Copyright Rudi Winter and licensed for reuse under this Creative Commons Licence.
year taken
2012
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SN5882, 374 images   (more nearby)
Photographer
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Image classification?
Supplemental image
Date Taken
Sunday, 20 May, 2012   (more nearby)
Submitted
Wednesday, 23 May, 2012
Geographical Context
Rocks, Scree, Cliffs  Geological interest  Coastal 
Near (from Tags)
Aberystwyth 
Image Buckets ?
Informative 
Subject Location
OSGB36: geotagged! SN 5826 8264 [10m precision]
WGS84: 52:25.3995N 4:5.1516W
Photographer Location
OSGB36: geotagged! SN 5826 8264
View Direction
SOUTH (about 180 degrees)
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Other Tags
Sandstone  Siltstone  Turbidite  Strata  Silurian  Mudstone  Aberystwyth Grits 

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