The Quarterly journal of the Geological Society of London . ELLASTOX GYPSUM BBECCIA. 179 unfits it for this purpose, and when it is still more impure it vergeson eoarsestone. It occasionally shows signs of stratification. The lower howl-shaped portion of the pillar is usually composedof eoarsestone enclosing numerous ovoid or rounded lumps of whitegypsum, and veins of satin-spar arranged more or less horizontallyor in conformity with the curved outline of the pillar. The deepestred colour occurs in this outer and lower layer, owing to theamount of included Keuper marl. At this locality there a
The Quarterly journal of the Geological Society of London . ELLASTOX GYPSUM BBECCIA. 179 unfits it for this purpose, and when it is still more impure it vergeson eoarsestone. It occasionally shows signs of stratification. The lower howl-shaped portion of the pillar is usually composedof eoarsestone enclosing numerous ovoid or rounded lumps of whitegypsum, and veins of satin-spar arranged more or less horizontallyor in conformity with the curved outline of the pillar. The deepestred colour occurs in this outer and lower layer, owing to theamount of included Keuper marl. At this locality there are only a few relics of original cover or cap left, for, as a rule, Glacial drift overlies the gypsum and fillsup parts of the swallowholes between the pillars ; but at one ortwo spots traces of about 2 feet of green and red marl were foundresting rather unevenly upon the white alabaster. At Woodlands, Fig. 3.—Diagram of a typical pillar at Ghellaston, showingwhite alabaster overlying lumps of the same set in redalabaster. (Heigh t of section = 9 feet.). *^^J^3^\ ^r i^g^gyg^Ei [Fibrous gypsum in eoarsestone is shown by narrowvertically shaded bands.] a quarter of a mile towards the south-east, the cap is exposedas a bed, from 2 to 3 feet thick, of green sandy marl and greengypsiferous marl resting upon a little red marl overlying the mainbed of gypsum. Sequence of Events before the Formation of the Breccia. We may now attempt to follow the sequence of events that ledup to, and finally resulted in, the formation of the breccia. The gypsum was apparently laid down irregularly, and conjointlywith the deposition of the horizontally-stratified marl, in the formof basin-shaped masses, which were probably due to crystallizationbeing set up at numerous isolated points, each of winch, is nowsituated on the central axis of a pillar. The lowest mass ofgypsum in each case was mixed with red marl, and now forms theeoarsestone of the pillar ; the next mass contained relatively littlemarl,
Size: 2622px × 953px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1840, bookidquarte, booksubjectgeology
