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| An outcrop of Carboniferous sandstone |
In
1997, the survey of potential RIGS in Doncaster, like others in the rest of the
county, was based on information gleaned from old maps, geological memoirs and
local knowledge of the area. For some reason, Barnburgh Cliff was not
identified during the desk top study and I first saw this site in 2007, when temporarily working with the British Geological Survey to produce the Doncaster Geodiversity Assessment.
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| Permian dolomitic limestone |
Walking
through a plantation along a straight bridleway, with a continuous
exposure of well bedded dolomitic limestone up to 4 metres high - on one side -
I thought that this place must have been quarried as a building stone
at some time; it has been suggested that a Roman road passed closely by.
It is a very good place to examine the lowest parts of the Cadeby Formation - with its shelly ooid-limestones and
reefs - which has a totally different character to the Sprotbrough Member seen at Warmsworth Park.
The yellow colour of the limestone often coincides with the appearance of large fissures, parallel
to the rock face, filled with orange coloured sand of Quaternary age. Some of these have developed into small caves, which elsewhere in South Yorkshire have been investigated by
speleologists, and which are the home for various
species of bats.
Although
the Permian limestone contains some very interesting geological features, Barnburgh
Crags is one of the very few places that I know of in South Yorkshire, where the underlying Carboniferous rocks can also be seen at the same locality. Unlike Ashfield Brick Pit, which as a SSSI was controversially infilled, the exact
position of the unconformity that separates these geological periods can only be
inferred from field evidence – but it is still an excellent field trip locality, at
all levels of study.
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| Upper Carboniferous Sandstone |
