Geological Survey Bulletin (Volume 1-5) (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1907. Excerpt: ... the slates of the Tullibardine area, but the junction-lines are invisible, and the presence or absence of any intervening strata undetermined. (2)--The General Sequence Of Events Leading To The Present Geological Structure. The following are the principal events which have succeeded each other in the area under consideration. They are presented in the order of their occurrence, as far as can be ascertained from the study of the rocks themselves and their field relationships. 1. The First Period of Sedimentation.--The series of sedimentary rocks, of which the slates of Mt. Farrell form the most considerable portion, appear to be the oldest rocks on the field. The passage from a conglomerate on the east through grits to the slates on the west seems to indicate a gradual submergence of an old basin. The old floor on which these sediments were laid down is not now recognisable; unless it be the quartzites and mica schists which outcrop on the eastern side of the valley of the Sophia River. As regards the age of the slates, it can hardly be fixed as yet. Lithologically their resemblance to the Dundas slates is marked. These latter are fossiliferous, and of Ordovician age. But at Mt. Farrell no fossils have been recognised in this formation. The slates may quite possibly have been contemporaneous with the sediments of the White Hawk area, now known from fossil evidence to be Silurian. 2. The Intrusion of the Older Igneous Rocks.--While it may be that these rocks are. in part at least, older than the slates, the writer considers the bulk of the evidence points to their later appearance. The rocks which now appear as diverse types seem to me to belong to one great series, and to have resulted from one magma. The syenites, quartz porphyries, felspar porphyries, an...