The overlying argillites
(Unit M5/5) have a sharp contact with sandstones.
The occurrence of Middle Cambrian to Late Ordovician organic-rich black shale deposits in an extensive area of Sweden (alum shale ), the Oslo region , Bornholm , Estonia (known as graptolite argillite
, "Dictyonema shale" , and kukersite as proper oil shale), Poland  and NorthWest Russia  has been known for a long time.
Three of these were used to make flaked adzes: Tahanga basalt, metasomatised argillites
from the northern South Island and argillites
from the southern coast.
The massive sulfide lenses commonly contained ribbon-like bands or large irregular masses of argillite
(mudrock), which had been silicified and mineralized.
On the lower parts of the Middle Hayden and nearby Lower Hayden brooks, about 19 km southwest of the Lower Birch Island type locality, the Lower Birch Island Member consists of about 6 metres of steeply dipping, thin-bedded, medium grey calcareous argillite
, silty argillite
and siltstone, overlying the Miramichi Group on the northwest, conformably and perhaps gradationally.
The Lower and Upper Fezouata formations consist mainly of argillites
and, together with the overlying Zini Sandstones and the Tachilla Formation, comprise the Outer Feijas Shale Group (Tremadocian to Darriwilian).
On the geochemistry of postsedimentary mineral formation in the Tremadoc graptolitic argillites
of North Estonia.
Geological horizons can be recognized clays Plicatules the Aptian, argillites
Callovian-Oxfordian clays and marls of the Gault, clays and marls domeriennes without this list being exhaustive.
The mine, which has never been systematically explored, has potential to host bulk-tonnage gold-silver mineralization within intensely altered granodiorite wallrocks and high grade gold mineralization in sheared argillites
The raw material which Maya archaeologists call 'slate' may not always be slate, as geologically defined, since it may derive from related geological materials, argillites
or phyllites (Fenton & Fenton 1940: 189-90, 309-11).
The Vine 1 occurrence is a shear-related vein system in Middle Aldridge Formation argillites
Estonian graptolite argillites
revisited: a future resource.
Geological horizons can be recognized clays Plicatules the Aptian, Callovooxfordien argillites
, clays and marls Gault clays Domerian, without this list being exhaustive.
were encountered beneath volcanic cover beginning at 553 meters.
Surface mapping and prospecting on the Dewdney Trail Property have identified areas with anomalous gold mineralization along a 13 kilometre trend of quartz-sericite-carbonate altered quartzite and interbedded argillites