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Viewing swaag.org website implies consent to set cookies on your computer. Full details Swaledale and Arkengarthdale Archaeology Group
Registered Charitable Incorporated Organisation Number 1155775
SWAAG Honorary President:
Tim Laurie FSA

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 *****SWAAG_ID***** 836
 Date Entered 18/09/2014
 Updated on 20/09/2014
 Recorded by Tim Laurie
 Category Geological Record
 Record Type Geological HER
 Site Access Public Access Land
 Record Date 31/08/2014
 Location Little Sleddale. West Gill Head
 Civil Parish Muker
 Brit. National Grid NY 80688 99978
 Altitude 675m
 Geology Namurian shales and sandstones. Thick beds of black shale with minor faulting.
 Record Name Little Sleddale. West Sike. Small faults infilled with white calcite in black shales
 Record Description Small oblique faults displacing horizontal nodular bands. The fault being infilled with white calcite and thus readily visible in black shales. I thank John Russell for his Notes on Faults, Shales, Siltstones and Mudstones. Thick beds of these soft dark rocks are present within the cyclic, alternating beds of limestone, thin coals and sandstone or gritstone strata which form the scenery of the Pennine Dales. These impervious shales and mudstones, being soft form spring lines above the more gentle concave slopes below the harder limestones and sandstones but are themselves rarely exposed except in the uppermost Gills where they can be prominent.
 Dimensions See photos.
 Additional Notes Geological Notes- thanks to John Russell: A simple guide to faults- 1 Shortening of the crust gives reverse faults-compression. 2 Stretching gives normal faults tension.. Faulting in shale is a XXXXX because shale is an incompetant rock and faults run everywhere. The rocks you mentioned are all very fine grained and to study them properly you need X ray diffraction techniques. Mudstone is a mixture of clay minerals mica and quartz.There is no layering of minerals and no plasticity. Shale shows distinct layers due to the alignment of clay minerals which are flat and platy-caused by the weight of the overlying rocks.Layers and laminations are described as fissile. Shale is not plastic and crumbles easily and is described as brittle-it is impermeable. Shale colour varies from grey to black depending on organics and iron content. Shale and mudstone have particle size around 2 microns.Between 4-6 microns come the silts and siltstone.Very difficult to tell them apart.The silt particles are just visible to the naked eye.
 Image 1 ID 5849         Click image to enlarge
 Image 1 Description Little Sleddale. Black shales exposed on the bank of West Gill Beck.
 Image 2 ID 5850         Click image to enlarge
 Image 2 Description Two parallel oblique faults displacing horizontal nodular bands in black shales above the bed of the stream.
 Image 3 ID 5851         Click image to enlarge
 Image 3 Description The calcite infil to the faults continues through the bedrock of the stream underlying the shale.
 Image 4 ID 5852         Click image to enlarge
 Image 4 Description Detail of the faults
 Image 5 ID 5854         Click image to enlarge
 Image 5 Description Detail of the faults
 Image 6 ID 5853         Click image to enlarge
 Image 6 Description West Gill seen from below.
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