Arkell.1956.Jurassic..

SOUTHERN ALPS J
73
SOUTHERN ALPS (LOMBARDY, VENETIA, SOUTH TYROL)
The Jurassic outcrop on the south side of the Alps begins near Lake
Como and forms a continuous strip from there eastwards through
Lombardy and Venetia, separating the piedmont plain from the high
Alps. The general dip is to the south, under the plain, from which it is
separated by a narrower strip of Cretaceous, while to the north it runs
out over a wider strip of Triassic limestones and dolomites. In the
region of Lake Garda all the Mesozoic outcrops widen and send a tongue
NNE., deep into the Alps of the Trientina; the reason for this is that they
are thrown down to the east along the Judicarian fault, which passes
through the Judicarian and Brenta Alps on a line about 10 miles west
of the lake. At the east end the outcrop passes through the Julian
Alps into Slovenia and curves round to the south-east into the Dinaric
Alps, which will be described with the Balkan Peninsula (p. 191).
Small outliers, mainly of Lias, occur many miles north of the chief
outcrop, in the Dolomites of the Tyrol and at a number of other places
on about the same latitude.
In facies and faunas the post-Pliensbachian Jurassics of the Southern
Alps conform closely to those of the Apennines and Sicily on the one
hand and those of the Carpathians and Vienna Basin on the other. The
North-Eastern Alps show the influence of proximity to the Bohemian
massif during the Lower and Middle Jurassic (Gresten facies, see p. 172),
but apart from that the North-Eastern Alps also belong to the same
province. The similarities in the Upper Jurassic are striking. With the
Swiss and French Alps and the territories beyond, including Provence
and Sardinia, there is far less agreement: in fact, contrast almost
everywhere after the Lower Pliensbachian. The inference is that these
regions were separated on the far side of the Alpine Schistes lustres
geosyncline, and that the geosyncline, which can be first detected in
Corsica, did not continue through the Eastern Alps but died out
not far east of the Rhine line. Doubts cast on the identity of the
Schistes lustres of the Lower Engadine and Tauern windows (see p. 162,
and Schwinner in Schaffer, 1951, pp. 216, 231) are thus supported by
the facies and ammonite faunas on the opposite sides and east end of
the Eastern Alps.
The chief peculiarities referred to, as characteristic of the Italian-
Carpathian region and a wide area of the Mediterranean, are: (1) great
abundance of special Hildoceratid ammonites in the Upper Pliensbachian
(the Domerian fauna); (2) ammonitico rosso in the Toarcian, with abundance
of otherwise rare Bouleiceratid genera; (3) thin, condensed, lenticular
Bajocian, Oxfordian, and Lower Kimeridgian; (4) Upper Bajocian,
Bathonian and perhaps Callovian developed as Posidonia beds with few
or no ammonites; (5) Lower and Middle Kimeridgian as red nodular
cephalopod limestones, the Acanthicus Beds; (6) lower part of the
Tithonian in same facies as the Acanthicus Beds, and passing up
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