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The Alps and the Himalayas: a Geological Comparison

1867; Geological Society of London; Volume: 23; Issue: 1-2 Linguagem: Inglês

10.1144/gsl.jgs.1867.023.01-02.46

2058-105X

H. B. Medlicott,

Geological and Geochemical Analysis

Abstract C urrent opinions on Alpine geology are first fully discussed by the author, especially as regards the abnormal nature of the actual boundary of the Molasse with the rocks of the higher Alps, including the explanation usually given of this phenomenon, and of the contortion of the inner zone of Molasse—namely, the direct upheaval of the main mountain-mass. Mr. Medlicott then describes some of the sections exposed on the south flank of the Himalayas, and suggests a parallelism between them and those exhibited in the Alps. The clays, sands, and conglomerates of the Sivaliks are very like those of the Molasse; and in both regions the coarser deposits prevail towards the top. In the Himalayas also the younger Tertiary deposits almost invariably dip towards the mountain-range which they fringe,—the plane of contact inclining in the same direction, and thus producing actual, though not parallel, superposition of the older rocks. All the arguments which have been used to prove prodigious faulting in the case of the Alps would therefore, the author states, be quite as applicable to that of the Himalayas. But, as regards the latter range, Mr. Medlicott brings forward evidence which appears to him sufficient to prove that the present contact of the Sivalik formation with the mountains is the original one, modified only by pressure, without relative vertical displacement; and that the sinking of the mountain-mass is the proximate cause of the contortions of the Tertiary strata. He then endeavours to show that this explanation is equally applicable to the Alps, especially as it seems also to account for collateral phenomena which appear difficult of explanation consistently with the ordinary hypothesis; and he concludes by discussing the current theories of the formation of lake-basins, in relation to the more immediate subject of his paper.