Abstract
LONDON.Geological Society, April 5.— Dr. C. W. Andrews, F.R.S., vice-president, in the chair.—E. S. Cobbold: Trilobites from the Paradoxides beds of Comley (Shropshire), with notes on some of the associated brachiopoda by Dr. C. A. Matley. The author describes and illustrates the type-specimens of Paradoxides groomii, Lapworth, 1891, and the associated trilobites from the basement beds of the Middle Cambrian of Comley Quarry. Among the latter there are two or three other species of Paradoxides, represented by fragments insufficient for specific determination; also a species of Dorypyge, allied to D. orient, Gronwall, and one of Conocoryphe allied to C. emarginata, Linnarsson. He also describes some of the trilobites from a higher horizon containing Paradoxides davidis, Salter, and P. rugulosus, Corda; and notes on the brachiopoda from this horizon are contributed by Dr. Matley. A complete list of the trilobites hitherto identified from the local Cambrian deposits is given.—Dr. D. Woolacott: The stratigraphy and tectonics of the Permian of Durham (northern area). The Permian strata of Durham and Northumberland lie unconformably on a basin of the Coal Measures; they may be divided into:—(4) upper red beds with salt and thin fossiliferpus Magnesian Limestones (only exposed in the south of Durham), 300 feet; (3) the Magnesian Limestone; (2) the Marl Slate, 3 feet; (1) the Yellow Sands, from o to 150 feet. These beds, which vary much in thickness, lie in North Durham in the general form of a syncline beneath Sunderland. The un-fossiliferous Yellow Sands are probably a deltaic formation reassorted by wind, the other beds being the result of deposition in an inland sea undergoing desiccation. The magnesium carbonate existed in the waters of the sea, and was either deposited along with the calcium carbonate or introduced by seepage when the beds were being laid down. Great changes in the amount and distribution of these carbonates have, however, taken place since deposition. The percentage of calcium carbonate is sometimes more than 99, while that of magnesium carbonate is occasionally as much as 50. The fauna of the Magnesian Limestone is very restricted (about 140 species) and most peculiarly distributed. The marked palaeontological features are the profusion of individuals in the Middle Fossiliferous Limestone (which appears to have formed a shell-bank in the Middle Magnesian-Limestone sea), anet their sudden disappearance in the Upper Limestone. No corals, echinoderms, polyzoa, brachiopods, or cephalopods have ever been found above the top of the. Middle Fossiliferous division, only a few fishes, gastropods, lamelli-branchs, entomostraca, and foraminifera occurring in the Upper beds. The Lower and Middle Fossiliferous Limestones are marked by the presence of Productus horridus, Sow. Fish-remains occur at two horizons, namely, the Marl Siate and the Flexible Limestone, and the beds above these deposits. The Brecciated beds, which occur at various horizons, chiefly, however, in the two Middle divisions, constitute the most marked tectonic feature of the Magnesian Limestone of the area. They have been produced by thrusting, which brought about a decrease in the lateral extension of the Permian. Associated with the breccias are other proofs of thrusting:—(1) thrust or shear-planes; (2) disturbed and displaced masses of Lower Limestone; (3) intruded breccias; (4) slickensided and grooved, horizontal and vertical surfaces; (5) cleavage; (6) folding, both on a local and on a general scale; (7) buckling, thickening, and squeezing-out of beds; (8) phacoidal and other structures; and (9) fissuring.
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Societies and Academies . Nature 86, 269–270 (1911). https://doi.org/10.1038/086269a0
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DOI: https://doi.org/10.1038/086269a0