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I. From the above review. it can be seen mal there is linle information on the
petrographic n,;tkeup of Cambrlan siliciclastics. and lhe chemical information provideri
here combined with previous work on slale!. suggests that the provenance of Cambrian
sllic:idulIC units may flO( be as ~11 understoOd as tw been Ulought. This clearly h.1S
an effect when eVillu,i1ing their signiranee as possible sources;
2. Albitisation of feldslW"5 in these Cambrian sandstones is ubiquilOVS. and is also
problematic (see e.g. ~unyomiCt al .. 1980; Quinn. 1985). Acomplclt underslanding
of lhe significance of these feldspars as delr;tal grains is precluded by a tack of
koowlcdge as 10 how and when they were allered:
J. Allochthonous Cambrian sandstones do 00l c10St'1)' ~mblt their panutochthonola
equivalents in terms of deuiLaJ makeup. Some of these differences clearly relate: to
differing depositional environmentS. but again Ihe conuoversy as 10 lhc e:uci age and
dqlOSilionaJ environment of the allochlhonous Cambrian units must hinder an
understanding of them as sourcesofdetrillls;
4. Two types of grains which are clearly resedimented are foond in the Goose Tickle
group and Lower Head Formation bUI 00l in the allochthonous Cambrian saOOsIOneJ.
Mictocline Ir.illins which are gener.l1ly more rounded than the rest of me quartz and
feldspat populalKtn are abundant. 1bere are also a very few silica cemenled yndsoone
fragments containing rounded gr.lins of quartz. microcline and plagioclase.
Although
microcline is presem in Ihe Cambrian units. il is not abundant. is frequently ..... ~olly or
panly replaced by albite. and is nor as ""'ell rounded as that found in the Ordovician
sandstones. The micnxline in the Goose Tickle group and loY.'el Head Formalion mosl