Underground borings through the Lower and Middle CoalMeasures beneath the Firth of Forth have proved sequences of rhythmically bedded volcanic detritus and a thin basalt lava. The detritus is believed to have been derived from a contemporaneous cinder cone or cones previously located by an off-shore boring. The new evidence suggests that locally there was an eastward shift of focus of eruption during Coal Measure times. The relationship of volcanism to this type of rhythmic sedimentation is discussed.
Methods and apparatus used in the isolation of heavy minerals vary considerably with different workers and this lack of uniformity obviously reduces the value of the conclusions in a branch of petrology in which quantitative data are essential. Panning in water and separation in bromoform are probably the two methods most widely adopted; but even with these there is considerable variation in the apparatus, each investigator using his own special panning device or type of separator. Also, whereas some writers employ direct bromoform separations, others treat the sediment by preliminary panning, and still others are content with panning alone. A paper published recently by Dr. F. Smithson showed the effects of panning on a crushed sandstone from the Yorkshire Trias and the results were compared with those of direct bromoform separations. The divergence of results was so great that it seemed worth while to carry out a similar type of investigation on some normal unconsolidated sands in which the heavy residue makes up about 0·2 to 0·3 per cent of the total bulk. The samples used in this case were mostly from the northern outcrop of the Folkestone Sand in the Weald, but some samples of Eocene Sands from the Continent were also examined.
Mine sections beneath the Firth of Forth at Wellesley Colliery fill gaps in the Knowledge of the strata adjacent to the junction between Middle and Upper Coal Measures. A hitherto unrecorded marine band which may formerly have been confused with Skipsey's Marine Band is now placed about 70 feet lower in the succession. A coal seam near the base of the Upper Coal Measures contains a rib of kaolin mudstone comparable with tonstein. Local reddening and alteration of coal to limestone in the Upper Coal Measures and more particularly in the upper part of the Middle Coal Measures is typical of a zone of partial oxidation beneath some major unconformity which may lie within the Upper Coal Measures or at some unlocated sub-Permian horizon above. Structureless highly-coloured clayrocks in the Upper Coal Measures, however, are regarded as primary red beds comparable with, and perhaps the equivalents of, the Etruria Marl of the English Midlands.
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