Jd. Floyd, LITHOSTRATIGRAPHY OF THE ORDOVICIAN ROCKS IN THE SOUTHERN UPLANDS - CRAWFORD GROUP, MOFFAT SHALE GROUP, LEADHILLS SUPERGROUP, Transactions of the Royal Society of Edinburgh. Earth sciences, 86, 1996, pp. 153-165
A formal lithostratigraphy is erected for all the Ordovician rocks in
the Southern Uplands of Scotland. At the base of the succession, the C
rawford Group (Arenig-Llanvirn) encompasses the chert and lava sequenc
es usually associated with the tract-bounding faults, and includes the
only proven Arenig rocks in the Southern Uplands. The overlying Moffa
t Shale Group (Caradoc-Llandovery) is now restricted to the black and
grey graptolitic shales which succeed the grey and red chert successio
ns. The Leadhills Supergroup (Caradoc-Ashgill) forms the overwhelming
bulk of the sedimentary succession and includes the thick Ordovician t
urbidite successions of the Northern Belt. Existing stratigraphical te
rminology is reviewed, revised or extended as appropriate to maintain
maximum continuity with current usage. Type sections for each unit are
either proposed, where newly defined or revised, or cited in the case
of existing definitions.