410 Dr. Preller—Contact-Zone of Alps and Apennines. 
and Mte. Ermetta (1,267 m.) in the Voltri Apennines on the east. 
- The depression of 500 metres thus constitutes a syncline, in the 
centre of which the region is deeply cut from north to south, and in 
its lower part, between Santuario and Savona, is eroded to a width 
of 4 kilometres by the Letimbro and Lavanestra. In striking contrast 
to the regularly stratified and undisturbed slopes on the north or 
Po side of the Apennines, the Savona region is intensely folded, 
contorted, and faulted, the maximum of disturbance being in the 
centre, viz. in and near the Letimbro Valley immediately west and 
north of Santuario, where all the rock formations converge. 
_ As previously mentioned, the northern part of the region is largely 
covered, in places to a depth of 400 metres, by Oligocene marine 
conglomerates and breccia which represent a former littoral formation 
raised in later Oligocene or early Miocene times. It was during that 
emergence and raising from the sea that the Savona region was, 
by enormous pressure from below and from both sides west and east, 
compressed, folded, fractured, brecciated, and, as Termier and Boussac 
term it, reduced to a chaotic condition, a process repeated on a smaller 
scale in Post-Pliocene times and followed in each case by a settling 
which gradually produced the present depression and contact-zone 
between the Alps and the Apennines.’ 
This enormous compression by repeated earth-movements explains 
the crushing, lamination, brecciation, and more or less intense 
alteration of the crystalline rocks, as well as the highly angular 
unconformity between them and the sedimentary formations, and the 
marked disturbance of the latter along the lines of contact. The 
many passages and stages of alteration in the crystalline rocks render 
a differentiation between transformed granite, gneiss, and amphibolite 
very difficult; but the granitic rocks being largely predominant and 
of eruptive origin, it is by no means improbable that the gneissic 
and amphibolie rocks too are derived from granite which thus 
constituted the whole original massif.? Its eruption and spreading 
out over the Permo-Carboniferous formation must in that case have 
taken place about the Middle Permian period, as the Upper Permian 
or Verrucano in part overlies the massif. This interpretation thus 
solves without an overthrust the cardinal problem of the abnormal 
superposition of the crystalline rocks on the Permo-Carboniferous 
formation.’ 
If, on the other hand, the problem is to be solved by an overthrust, 
it appears more probable that the whole crystalline massif was 
1 7,. Mazzuoli, in an interesting memoir on the ‘‘ Formazione dei Con- 
glomerati Miocenici nell’Apennino Ligure ’’, Boll. R. Com. geol., 1888, p. 9 et 
seq., mentions the noteworthy fact that soundings carried out by the Italian 
Marine Department along the Riviera littoral of Genoa and Savona have proved 
the existence of submarine river valleys at depths up to 900 metres at 4 nautical 
miles from the shore. The ratio of fall below sea-level is thus about the same 
as that from the Apennine crest-line to the coast. 
= The gneissic rocks of Valdana, in the south-eastern part of Elba, are by 
common consent of granitic origin, though older than the microgranites in the 
west of Elba (B. Lotti, op. cit., p. 285). 
3 By this interpretation Termier and Boussac’s exotic granite mass, section 
Fig. 3, whose submarine part is of course purely hypothetical, becomes simply 
an ordinary intrusive tongue formed in situ. 
