Page:Quarterly Journal of the Geological Society of London, vol. 35.djvu/855

Rh GLENGAKIFF GHITS AND SLATES. 715 Representative beds of the Upper Silurian Series in Kerry and Mayo and Gahvay. Kerry (including Dingle). West Mayo and Galway. 3. Upper Slate Series. — Bright red 3. SalrocJc Slate Beds.— Bright red and purple slates, forming the shores slates and shales, with bands of grit of Dingle Harbour, also underlying and one of limestone. Lingula Sy- the Lower Carboniferous beds at mondsii, Pterinma retroflexa, Trochus Sneem, Kenmare, Glengariff, &c. multitorquatus. About 3000 feet. 3000 feet. 2. Glengariff-gritandFerriter's-Gove 2. Mweelrea Beds. — Green and pur- Series. — Massive green grits, sometimes pie grits, conglomerates, with beds of pebbly, with beds of slate (Beeks and slate and shale. Volcanic ashes and Killarney and Glengariff mountains, felspathic lavas in the lower beds. Great Blasket Island, &c). The slate Fossils of Wenlock and Ludlow spe- series of Dunquin coast, Ferriter's cies. 8000 feet. Cove beds, with volcanic ashes and traps, fossils of Wenlock and Ludlow species. About 10,000 feet. 1. Smerwick and Sybil-Head Beds. 1. Owenduff Series (Upper Llando- — Lying at the base of the Dingle very). — Green and grey grits, sand- section. Purple and brown and green stones, shales, with brecciated lime- sandstones, flagstones, and shales (no stone, with volcanic ashes and traps ; fossils). At Bull's Head, on the slope base generally a conglomerate. Fos- of Caherconree, Llandovery species sils : — Favosites fibrosus, Cyathophyl- have been found, Favosites alveolaris, lum elongatum, Encrinurus punctatus, Cyathophyllum (Petraia) elongatum, Illcenus Bowmanni, Orthis reversa, Atrypa hemisphcerica, &c. Atrypa hemisphesrica, Trochus multi- torquatus, &c. About 2000 feet. From the comparisons above it will be observed that there is no essential difference between the sections in the two districts recor- ded. In both the fossils are chiefly plentiful in the beds represen- ting the Llandovery and Wenlock series ; and if in the upper beds of the Dingle series they are absent or scarce, such is also the case with the Mweelrea beds in Mayo. As regards thickness, both sec- tions are incomplete ; but we find in each case a great development of sedimentary strata, surpassing that of their representatives in the Silurian border districts of England and Wales, in which calcareous beds occupy a prominent position. To this feature I propose to return further on. Volcanic Products. — Another feature of resemblance between the beds of the two districts, that of Dingle and Killarney, is the occur- rence in both of the products of contemporaneous volcanic action. In the former district these are opened to us along the coast N. of Dunquin Harbour amongst the beds of the Wenlock and Ludlow stage, and on a large scale (fig. 1). They are several hundred feet in thickness, consisting of beds of felspathic ash and lapilli, more or less consolidated, traversed by cleavage-planes and passing from the condition of an agglomerate to that of the finest powder. The ge- neral dip corresponds to that of the Silurian beds, being south at 25°-30° ; and immediately north of the entrance of Dunquin Har- bour or Inlet there occurs a mass of intrusive greenish felstone, about 100 yards across, which may possibly be the consolidated lava filling