RELATION TO ME80Z0IC ROCKS IX THE LEPONTINE ALPS. 237 



"3. In the Central massif s occur rocks which exactly resemble true crystal- 

 line schists in mode of occurrence. Petrographically, they are related to tliein 

 by passage-rocks ; at least, the line of separation is not easily distinguished. 

 Such I'ocks are p/it/llifes, chloritc-schisfs, felsite-schists, mica-schists, and espe- 

 cially sericite-gneisses, all of which we regard with certainty as paLTOzoic. Th(5 

 proofs are the following : — 



" (a) In some places in these zones are found intercalated beds of graphitic 

 and sometimes even anthracitic schists (Bristenstock, &c.). 



" {h) Traces of fossils have been oiten found (trunks of Calamites from Gut- 

 tannen in the Haslithal, Carboniferous plants in strips wedged in on 

 the Todi, &c.). 



•' {c) At the end of the Central-massif distinct zones of Carboniferous slates 

 are often developed, out of the zones of these sericitic gneisses ; and 

 the synclinal (' Mulden ') nature of these zones, in comparison with 

 the old granitic gneisses, is shown there by the wedging in of still 

 younger unaltered sediraentai-y rocks. 



•' (cZ) I have already shown in my Todi-Windgallen group that even the 

 Verrocano (Permian), when nipped in between crystalline schists, 

 assumes a close resemblance to them, and appears as a part of the 

 crystalline Central-massif. 



'' Fragments of these rocks are found in the Triassic Rauchwacke, but this is 

 not the case with the garnetiferous schists of Scopi, which are younger than the 

 Rauchwacke, and belong to the true sedimentary synclinal zones (' Mulden'). 



" A great unconformity exists in the Central Alj^s between Paleozoic and 

 Mesozoic formations, but not between Pahiiozoic and Azoic. 



" I. The Pal(SO~oLC formations mostly show an intimate tectonic relation to 

 the crystalline schists, and have been converted petrographically into crystal- 

 line schists. The central-massifs consist, perhaps to the extent of two thirds, 

 of true old crystalline schists, older than the Cambrian, in part, perhaps, the 

 primitive crust (Erstarrungskruste, granite-gneisses, protogine) ; and to the 

 extent of about one third of Palaeozoic mica-schists, sericite-schists, amphibolites 

 and other similar rocks which have been derived by dynamic metamorphism 

 from Pali^ozoic slates, sandstones, and conglomerates ; and Baltzer distinguishes 

 between the old nucleus and the younger shell (slates) of the Central-massif. 

 They are kneaded and pressed into one another. 



•' II. The genuine Mesozoic deposits follow, sometimes conformably, some- 

 times nnconformably. In places they have become crystalline and schistose 

 {schicfrig-krystalliniscK) ; but they never occur as a constituent of the Central- 

 massif, but always accompany the Mesozoic deposits, or are intercalated as 

 ' Mulden ' in, and especially between, the Central-massifs. They are never termed 

 ' C^rystalline-schists ' in the geological sense of the word — at the most, only in its 

 petrographical sense. 



"The latest literature on these things is, above all : — 



" Baltzer. ' The Aar-massif and a part of St. Grothard massif,' ' Beitriige 

 zvir geol. Karte der Schweiz, 24th Lieferung, 1S88. 



" Grubemiiann {Frof. Dr.). ' The Sedimentary " Mulde " of Piora.' 



•'Baltzer furnishes, in the volume above cited, some excellent work on the 

 rocks indicated under I., and gives a drawing of the Calamile-like trunk from 

 Guttanen. Grubenmann does the microscopic work in connexion with the 

 Mesozoic formations belonging to II., which \\ix\cnever been referred, by us, to 

 the crystalline schists or to the Central i/iassif. 



" Result. 



•' Much of what have been regarded as genuine crystalline scliists in the Alps 

 is Palit'ozoic. 



" The crystalline metamorphosed Mesozoic rocks always occur as sedimentary 

 deposits, and have never been termed ' crystalline schists ' in the stratigraphical 

 sense " *. 



* After reading once more Dr. Heim's essay, communicated to the International 

 Geological Congress in 1888, I cannot hold myself to blame for misunder- 

 standing it, and must contend" that the sentences quoted above on page 223 



