Societies and Academies

Abstract

LONDON Geological Society, June 6.—Mr. J. W. Hulke, F.R.S., president, in the chair.—George Paul was elected a Fellow of the Society. —The following communications were read: —The estuaries of the Severn and its tributaries, an inquiry into the nature and origin of their tidal sediment and alluvial flats, by Prof. W. J. Sollas, M.A., F.R.S.E., F.G.S. —Notes on a col lection of fossils and rock-specimens from West Australia, north of the Gascoyne River, by W. H. Hudleston, M.A., F.G.S. —Notes on the geology of the Troad, by J. S. Diller. Com municated by W. Topley, F.G.S. This paper gave a brief account of the results obtained by the author whilst attached to the United States Assos Expedition. Together with a geo logical map (scale 1: 100,000) this was sent to Mr. Topley for the service of the new geological map of Europe (and its bor ders), which is now being prepared by a Committee of the International Geological Congress. The country described is that lying south and west of the River Mendere (Scamander). The sedimentary rocks may be divided into three great groups: — I. An old, possibly Archaean, highly crystalline series, forming the mountainous lands of the Ida range (5750 feet), but also appearing in smaller detached areas to the west and north-west. Probably these have existed as islands from early times, and around these the later rocks have accumulated. Mount Ida itself is almost a dome, the lowestrocks (talcschists) occupyingthe summit. On the northern slopes there is true gneiss. No igneous rocks enter into the structure of this mountain. At different horizons there are bands of coarsely crystalline limestone, and as far as can be seen this series is conformable throughout. 2. Resting on these old rocks and in part made up of their remains is a series of partially crystalline rocks, chiefly limestone. It is probable that this series is in large part of Cretaceous age; but it contains rocks which are older, possibly Palaeozoic. Eocene fossils have lately been discovered by Mr. Frank Calvert, which also may have come from this series. The rocks in the south of the Troad, hitherto supposed to be Lower Tertiary, are now known to be of later date. Sharply marked off from these older rocks are the Upper Tertiaries; these are of two ages, occurring in two distinct areas. 3. The Upper Miocene, which fringes the western shores of the Troad, and forms a broader, band at the north-west corner in the lower course of the Mendere. Hissarlik is built on this. These beds are marine, and belong to the Sarmatmn Stage. The Troad is the most south-westerly point at which the Mactra-kalk is yet known. 4. Freshwater beds, which occur in force in the interior of the country, between the Menderé and the south coast, and in patches near the coast. These are Upper Miocene or Lowest Pliocene. Later than these are the Pliocene beds of the great plain of Edsemet The igneous rocks are of various ages, but most are of Tertiary date. The oldest is a granite which intrudes through and alters the oldest (? Archaean) crystalline rocks. This is invaded by dykes of Quartz-porphyry. Quartz-diorite invades and alters the group of partially crystalline rocks. The oldest rocks in the newer series are the Andesites and Liparites. These, in part, are older than the Sarmatian stage, as the conglomerate at its base con tains fragments of these rocks. But they are also in part of later date. Where they can be studied together the Liparite is the later of the two, as it flows through and carries up fragments of the Andesite. The Andesite (unlike the Liparite) seems to have reached the surface, in some cases, through volcanic vents. Basalts and Nepheline-basalts are of late Tertiary date; possibly they are the latest volcanic rocks of the district, but their relation to the other eruptive rocks of the Troad cannot be definitely determined. The volcanicjrocks in the isolated area between Alimadja and Lyalar are interesting because their relative ages are here well seen. The earliest was melaphyre; this was followed by mica-andesite, horneblende-andesite, augite-andesite, basalt, and late (if not last) by liparite. Mr. Topley, who in the absence of the author read the paper, explained the objects of the Assos Expedition and the geological results obtained by Mr. Diller. He gave a short account of previous literature, and mentioned some of the main points in which our knowledge of the Troad is now advanced. Mr. Topley briefly described the physical geography and general structure of the country, illustrating this by means of a section which he had prepared from Mr. Diller's map and paper.