Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/653

1870.] HIND GNEISSOID SERIES OF NOVA SCOTIA. 471 II. General Sketch of the Distribution of the Supposed Huronian AND LAURENTIAN SERIES IN NOVA SCOTIA.

In this general sketch of the old gneissic rocks of Nova Scotia they are grouped together. In succeeding paragraphs it is stated where Huronian or Cambrian gneiss and schist rest on the Old Laurentian gneiss as far as known. The country occupied by these gneisses is for the most part an uninhabited wilderness.

The object of this paper is to show that two gneissoid series, supposed to be the equivalents of the Huronian and Laurentian of Sir W. E. Logan, are exposed over very large areas in Nova Scotia, the Island of Cape Breton, and in New Brunswick.

The outcrop of the Laurentian and Huronian in Halifax and Hants Counties has been traced from a point seven miles west of Windsor, on the Basin of Mines (Bay of Fundy), to the Atlantic coast at Cape Sambro, a distance of forty-eight miles in an air-line, and sixty-four miles on the margin of the outcrop. This is the north-easterly boundary of an immense area of the same rock-series which, from information hereafter noticed, I believe continues with variable breadth to the Tusket Islands, near Yarmouth, a distance of about 135 miles in an air-line.

The area above described forms the western development of the Laurentian and Huronian gneisses and schists in Nova Scotia. It is separated from the eastern development by a narrow profound valley, occupied by Silurian strata, whose least breadth is eight miles. The outcrop of the south-western boundary of the eastern development is not continuous, but, as shown on the map, embraces two areas near Grand and Parker Lakes, and an area of unknown but very considerable and variable width, stretching (with some narrow interruption of Silurian strata which have escaped denudation) probably all the way to the Strait of Canso and Chedabucto Bay, a distance of 120 miles in an air-line ; so that, generally speaking, a Laurentian axis, capped here and there by strata of Huronian age, occupies Nova Scotia, certainly in one place at least forty-eight miles in breadth.

The existence in Nova Scotia of all formations, from the Trias to the Laurentian, with the exception of the Permian*, may now be regarded as very probable. Whether the rocks noticed in the footnote are of Permian or Triassic age, I am not able to say ; but, judging from the descriptions given of the relations of the Triassic to the Carboniferous by Dr. Dawson, I have hitherto considered

on the Gulf coast, and at Trout Brook, five miles north-east above Chetican, mottled sandstones and conglomerates rest unconformably on white and mottled sandstones and bituminous shales, supposed to be of Lower Carboniferous age. These latter rest unconformably, the first on red metamorphic rocks ; the second are seen in close proximity to red, green, and black corrugated schists, supposed to be of Lower Silurian age. In Dr. Dawson's tabular view of the geological formations of the Acadian Provinces (Acadian Geology, p. 19) the Permian is stated to be " not represented, unless by the lower part of the sandstones of Prince Edward Island." May not the unconformable patches in Cape Breton be a continuation of these Prince Edward-Island deposits?
 * In Cape Breton, at Jumping Brook, seven miles north-east of Chetican Island,