CAMPSIE GLEN
Access: The field trip starts at the car park/bus terminus at Clachan of Campsie.
Tour: Geowalks
Weather: A fine, sunny day
Summary:
The high ground that forms the Campsie Fells is built of a thick sequence of Carboniferous lava flows, the Campsie Lavas.
In the lower ground to the south of the Campsies, these lavas have been downfaulted by the Campsie Fault, which forms the often prominent scarp found along the south slopes of the Fells. The complete sequence of lavas does, in fact, lie below the lower ground in the south, though its top is rarely exposed locally. On ascending Campsie Glen from the car park, the fault is crossed over about 200 yards to the north, though glacial and river erosion have obliterated any evidence for it in this vicinity.
In the higher ground to the north, Lower Carboniferous sedimentary rocks belonging to the Cementstone Group and lying stratigraphically below the lavas are exposed in Campsie Glen, to be followed upwards in the Glen and onto the Fells, by the complete sequence of lavas.
Many of the lavas in the Campsies are of Markle basalt, a distinctive type having large elongated white phenocrysts in a fine-grained groundmass. They may be examined conveniently in the old quarry just above the car park on the Crow Road (excursion guide: locality 6).
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