| Popis: |
Some 8 miles south of Adelaide a typical exposure of the conglomerate is bounded on the east by a series of alternating quartzitic and argillaceous bands of rock, comprising the central and western portions of a fan-fold, partly cut off by a fault. Further evidence of stress in this margin is given in the fissility, pseudo-ripple-marks, contortion and fracture, and obliteration of bedding in the quartzite-bands, and in the pinching-out of them into lenticles and false pebbles. On the west side the conglomerate is bounded by the ‘Tapley9s-Hill Clay-Slates,’ and there is evidence from the nature of the junction-beds that the conglomerate itself is isoclinally folded. In that portion of the conglomerate which is adjacent to its confines, ‘boulders’ of quartzite are apparently disrupted portions of quartzite-bands, since these are in alignment with the truncated portions of bands still existing, and are of similar composition. The Authors are not at present in a position to account for the presence in the conglomerate of boulders of rocks foreign to the beds that border the conglomerate, or of such as possess markings comparable to glacial striae, by their theory of differential earth-movements; but they consider that a boulder-bed subjected to lateral pressure would probably lend itself to the production of ‘false pebbles,’ through the disruption of intercalated hard bands within itself or on its boundaries. Dr. A. Strattan considered the first paper to be lucid and convincing account of an extremely-interesting series of deposits. The association of schistose rocks and slates with |
