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| The Yellow Sands Formation in Pontefract |
Along
the length of the Magnesian Limestone, the lowest beds of the Cadeby Formation are often underlain by the very distinctive Yellow Sands Formation.
Yellow/orange in colour, it is generally loosely cemented and contains a high proportion
of wind rounded and frosted grains – indicating an aeolian origin; also, it is
often strongly cross-bedded, where the dunes have been subsequently reworked by
the transgression of the Zechstein Sea.
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| Roadside exposures of sandstone and limestone |
Very
often, even where there is no evidence of the outcrop of the Yellow Sands
Formation, the lowest beds of the Cadeby Formation often have a very distinct
yellow/orange colour, which mark the transition from sandstone to the overlying
limestone; this can be seen in old quarry exposures in South Elmsall and in
some of the building stones at All Saints church and Pontefract Castle.
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| An overgrown road cutting with a retaining wall |
In
South Yorkshire, the only outcrops of the Yellow Sands Formation seen during the
survey of Regionally Important Geological Sites (RIGS) are found on privately
owned land, with limited potential for field trip visits but, in Pontefract,
there are several roadside exposures that can be seen and closely inspected, if
common sense precautions are taken with respect to passing vehicular traffic.
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| A road cutting |
The
Yellow Sands Formation was once extensively worked for building and moulding
sand, as well as being used in the glass industry and in Pontefract - taking
advantage of deep road cuttings - adits were driven into the soft sandstone,
where it was mined by the pillar and stall method.
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| A back garden in Pontefract |
Although the old adits have
been bricked up, and many of the exposures are partially covered by retaining walls or
heavily overgrown, there is enough geology to make this a worthwhile field trip
location on a day out in West Yorkshire.
