Gloucestershire Geology Trust
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Breadstone Shale

Ordovician (Tremadoc)

PERIOD
GROUP
FORMATION
Ordovician
-
Bronsil Shale

Lithology
Fissile, micaceous, grey to bluish grey or greenish grey mudstone, with bands of fine-grained sandstone and rare thin calcareous beds with cone-in-cone concretions and interbedded siltstones.

Upper Boundary
Overlain by the Micklewood Beds (Tremadoc). Contact not seen but probably conformable and gradational. The Micklewood Beds are distinguished from the Breadstone Shale Formation by the more common occurrence of flaggy sandstone and siltstone beds.

Lower Boundary
Unconformable on older rocks.
Not seen. Strata beneath the Breadstone Shale Formation are not exposed in the Tortworth Inlier.

Representative Sites
Bushy Grove Plantation

Information on lithology and boundaries taken from the British Geological Survey Lexicon of Named Rock Units
and BGS Memoirs.

 

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