Br. Du Riche Preller— Three Glaciations of StvifzerlancL 31 



hornstone, nummulitic limestone, dark Alpine limestone, derived from 

 the detritus of Miocene nagelfliib, red limestone or sernifite, green or 

 so-called Tavayanaz sandstone, and other rocks of the Glarus Alps. 

 Pebbles of Julier and Puntaiglas (Ehine watershed) gabbro, 

 granite, and diorite which abound in the later glacial deposits, are 

 absent in this nagelfluh : hence the inference that its constituents 

 are derived exclusively from the Glarus Alps.^ Some other very 

 large deposits of hollow nagelfluh occur in the Aare Yalley and 

 below Turgi, near Kaiserstuhl on the Khine, and on the Irchel, 

 bordering on the Ehine and situated about half-way in a line 

 between Zurich and Schaifhausen. The deposits named, together 

 with other intermediate ones, vary in altitude above sea-level from 

 300 to 872 metres or, roughly, from 1000 to 3000 feet, thus forming 

 a belt of fluvio-glacial deposit, which may, therefore, be also taken 

 as indicating the contour line and limit of the terminal moraine 

 of the first Upper Pliocene glaciation. 



Second Glaciation.— Upon a long interglacial Upper* Pleistocene 

 period of erosion, followed a second and far more extensive glaciation, 

 which covered the whole North of Switzerland to Basle and the 

 Jura, while to the south-west the Khone glacier advanced as far as 

 Lyons. Of the glacial deposits of this period I examined, among 

 others, the very typical deposit laid open in a quarry on the so-called 

 Allmend of Zurichberg, viz. on the hill above the town, on the right 

 of the lake and opposite Utliberg, at an altitude of about 570 metres 

 or 1890 feet above sea-level. In this deposit the boulder-clay, 

 showing the usual characteristics of larger and smaller more or less 

 angular blocks with polished and striated surtaces, passes gradually 

 into gravel-bearing moraine sand or surface moraine, which, in its 

 turn, is covered by a thin layer of alluvial soil. This gradation, 

 shown in the diagram, is observable in every one of the numerous 

 smaller quarries, excavations and foundations for building purposes 

 on the Zurich hills flanking the lake on the right bank, seeing that 

 these hills are entirely covered with the deposits of the second 

 glaciation resting on molasse. The gravel-beds of the Limmat 

 valley, which are so extensively quarried below Zurich, and reach 

 as far as Turgi, Waldhut, and Basle, are the fluvio-glacial deposits 

 of this second glaciation, and the characteristic feature of all the 

 three gradations, viz. of boulder-clay, moraine sand, and the 

 glacier-stream deposits, is that their material is largely derived 

 from rocks of the Grisson Alps, such as granite and Marmels gabbro* 

 of the Julier Alps (Hinter-Ehine) and of Puntaiglas granite and 

 diorite (Vorder-Ehine), showing that in Middle Pliocene times 

 there existed a connection between the Ehine and Linth valleys 

 and that the glaciers of the former considerably reinforced those 

 of the latter. 



1 Puntaiglas granite and diorite are derived from the classic locality or valley of 

 the same name, descending from the southern slopes of the Todi group to the Vorder- 

 Ehine valley near Truns. Sernifite is a red limestone derived from the Sernf valley 

 in the Glarner Alps from Glarus to Elm. 



2 Marmels gabbro is derived ft-om the classic locality of that name, situated in the 

 Oberhalbstein or Sur valley (Julier Pass) of the Grisson Alps. 



