Abstract
LONDON. Geological Society, November 3.—Prof. W. J. Sollas, F.R.S., president, in the chair.—S. S. Buckman: Certain Jurassic (Lias-Oolite) strata of south Dorset, and their correlation. Descriptions of certain strata (Lower Bathonian to Pliensbachian) on the Dorset coast. Comparison is made with similar strata inland. The strata described are classified according to the scheme introduced for these strata in 1893. The strata are arranged among thirty-six zonal (hemeral) divisions. The Upper Lias part of the junction-bed of Down Cliffs, Chideock, is a very condensed, imperfect epitome in 20 inches of about 80 feet of strata on the Yorkshire coast. Between the bifrons-layer and the striatulus-layer of the junction-bed there is occasionally a 2-inch layer, which is all that represents some 250 feet of deposit in the Cotteswolds. The Upper Tcarcian makes a great showing at Burton Bradstock and Down Cliffs as the Down Cliffs Clay and Bridport Sands. The sequence of aalensis-strata above moorei-beds is demonstrated at Chideock Quarry Hill, in the upper part of the Bridport Sands. The Inferior Oolite strata of Burton and Chideock are not counterparts of one another; they supplement each other to a certain extent. Mr. Thompson's zonal scheme for the Upper Lias is considered.—S. S. Buckman: Certain Jurassic (“Inferior Oolite”) Ammonites and Brachiopoda. The paper describes certain species of Ammonites and Brachiopoda which are important for the identification, the correlation, or the dating of Inferior Oolite deposits, and certain other notable species which, having frequently attracted attention in the field, require naming in the interest of future workers.—Dr. W. F. Hume: The granite-ridges of Kharga Oasis: intrusive or tectonic? The author quotes the records given by Mr. Beadnell in his paper published in February, 1909, and although in agreement with the facts there stated, differs with regard to the interpretation of those facts. Whereas Mr. Beadnell regards the granite as intrusive, on account of the high dip of the sedimentaries, and the changes which they exhibit as regards colour and hardness, near the granite, the author considers that the dips are due to fold-movements almost at right angles to one another, since they lie on the same line as the crater-like basins, the rims of which are formed of the compact and steeply dipping limestones of the Lower Eocene, and he adduces as further evidence the fact that dykes and quartz-veins penetrating the crystalline rocks cease abruptly at the edge of the sandstone.—Dr. W. F. Hume: The Cretaceous and Eocene strata of Egypt. The fossiliferous Cretaceous strata are divided into three series:—(1) A northern Antonian type, marked by Cenomanian species, including typical Turonian strata. (2) A central Egyptian or Hammama type, Cenomanian strata being absent, Campanian marked by abundance of Ostrea villei and Trigonarca multidentata, and phosphatic beds; the Danian portion having an eastern facies, in which Pecten marls are a characteristic feature, and a western chalky limestone indicating a close affinity with the white chalk of northern Europe. (3) A southern or Dungul type, having close affinities with (2), but in the Campanian the phosphatic beds are inconspicuous, and the fauna consists of a group of specialised sea-urchins and of gastropods, among which Turritellæ are very prominent. The uniformity of the Lower Eocene throughout Egypt is emphasised, its triple subdivision being recognisable over vast areas. In the Middle Eocene this uniformity is replaced by differentiation. Five zones have been recognised in the lower division, while in the Upper Moqattam the Turritella-beds and the strata rich in Carolia placunoides and Plicatula polymorpha are of zonal importance. The Lower Moqattam is considered as beginning with the Nummulites gizehensis zone and closing with the Gistortia-bed. The relation between the Cretaceous and Eocene beds is discussed. Palæontologically, great groups such as the Ammonites, still abundant in the Upper Cretaceous, disappear in the Eocene, and are replaced by the characteristic nummulinid Foraminifera. Both periods bear a resemblance to each other in the dominance of oysters and sea-urchins. A notable feature is the rarity of Brachiopoda in Egypt throughout both periods, nor have belemnites been recorded from the Egyptian Cretaceous. Among post-Eocene formations the calcareous grits are shown to have a wide extension, but in the desert they differ in character from the mammal-yielding beds of the Fayûm. The Cretaceous period in Egypt was one, in the main, marked by the gain of sea over land, the Eocene was one of rest, while at the close of the Eocene and during the Oligocene the approach of a continental phase is clearly indicated.
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Societies and Academies . Nature 82, 117–120 (1909). https://doi.org/10.1038/082117a0
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DOI: https://doi.org/10.1038/082117a0