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| Keywords: The Quarterly journal of the Geological Society of London (13936959322).jpg 84 PEOF T G BONNET ON TWO TEAVEBSES OF THE <br> over the crystalline rocks of the central range from which however <br> they have been almost entirely removed by denudation Of the <br> igneous rocks of the region especially those of the Southern Tyrol <br> it is needless to speak The above-named Thonschiefer with the <br> lower part of which some chloritic schists and crystalline limestones <br> are associated is extensively developed in the Eastern Alps The name <br> Thonschiefer is vague ; for if I mistake not it might be applied <br> to either a claj -slate or an aluminous schist Certainly the rock is <br> not the former though sometimes locally when greatly crushed it <br> presents a stroug resemblance to it In the extensive rock-collec- <br> tion of the Innsbruck Museum the series is called Thon-glimmer- <br> Schiefer which is made less ambiguous by the inserted word I <br> have a difficulty in finding an English equivalent Clay -mica- <br> schist is misleading aluminous mica-schist awkward ; upper mica- <br> schist is open to objection as involving an assumption as to strati- <br> graphy ; phyllite suggests too fine-grained a rock ; so I propose at <br> present in the poverty of English nomenclature to retain the <br> German term Thonglimmerschiefer <br> /3 The Pusterthal and Neighbourhood <br> We travelled by railway up the valley of the Adige traversed <br> the igneous rocks in the neighbourhood of Bozen and in due course <br> reached the Thonglimmerschiefer south of Klausen With the <br> members of this group previous visits to the Tyrol had already <br> made me fairly familiar and I could see even as I passed by that <br> though they varied somewhat in texture and hardness the dominant <br> rock is a moderately soft dull lead-coloured mica-schist in which the <br> individual films are not coDspicuous to the eye at any rate at the <br> first glance This obscuration of the true structure is very probably <br> the result of crushing The apparent foliation is a cleavage-foliation <br> the conspicuous surfaces are sheen surfaces which exhibit a <br> peculiar gloss looking sometimes like the polished black-lead of a <br> fire-grate <br> These macroscopic characteristics are very commonly so general <br> and so uniform that one can recognize the rock with certainty even <br> from a railway-train f Our first halt was made at Brunecken <br> where the Thonglimmerschiefer series is well exposed close to the <br> town and presents some interesting variations The picturesque <br> old castle stands on a craggy mound of white crystalline limestone <br> Appendix p 107 ; this on the southern side is distinctly bedded <br> like an ordinary limestone and dark streaks occur in the rock <br> parallel with this structure The beds are much twisted about but <br> they appear to have a general strike about S S E with a high dip <br> On the northern side a little mica-schist crops out apparently in <br> situ ; but its strike is nearer E S E Then comes after a short <br> In several places as I have myself seen and have learnt from the Innsbruck <br> Museum the dolomites of the Italian Tyrol rest on either Thonglimmer- <br> schiefer or mica- schist <br> t I have verified this assertion many times 36939865 113696 51125 Page 82 Text 45 http //www biodiversitylibrary org/page/36939865 1889 Geological Society of London Biodiversity Heritage Library The Quarterly journal of the Geological Society of London v 45 1889 Geology Periodicals Smithsonian Libraries bhl page 36939865 dc identifier http //biodiversitylibrary org/page/36939865 smithsonian libraries Information field Flickr posted date ISOdate 2014-04-21 Check categories 2015 August 26 CC-BY-2 0 BioDivLibrary https //flickr com/photos/61021753 N02/13936959322 2015-08-26 06 53 26 cc-by-2 0 PD-old-70-1923 The Quarterly journal of the Geological Society of London 1889 Photos uploaded from Flickr by Fæ using a script | ||||
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