The Shinnel Formation is dominated by over 2 km of quartzose sandstone
s. It crops out between the Fardingmullach and Orlock Bridge faults, N
orthern Belt of the Southern Uplands, and is of mid Ashgill age. The i
nterbedded and distinctive Tweeddale Member (previously the Wrae Limes
tone and Tweeddale lavas) comprises debris flow deposits with clasts o
f limestone which yield a diverse and abundant conodont fauna, includi
ng Pygodus anserinus, Baltoniodus variabilis, Periodon aculeatus, Prot
opanderodus varicostatus, Spinodus spinatus, Eoplacognathus lindstroem
i, Strachanognathus palvus and coniform species; an assemblage conside
red to be of P. anserinus Biozone (late Llanvirn (Llandeilian) to earl
y Caradoc (Aurelucian)) age. These conodont faunas are similar to thos
e from the upper Stinchar Limestone from Girvan to the north-west. The
deep or cool water, predominantly prioniodontid and panderodontid, co
nodont fauna is described systematically for the first time. Emended a
pparatus plans are proposed for Pygodus anserinus, Protopanderodus var
icostatus and Strachanognathus parvus.