Arkell.1956.Jurassic..

CHAPTER 6
THE ALPS AND NORTHERN CARPATHIANS
PROVENCE, THE MARITIME ALPS AND SUBALPINE RANGES
Between Toulon and Cannes the coast cuts across the crystalline
horst of Maures and Esterel, a protrusion of the ancient basement of
the Alpine foreland comparable to the Massif Central, Vosges, and Black
Forest, but partly mantled in Permian and Triassic sediments. On the
north side the horst is bordered by a band of Jurassic outcrops which are
also cut by the coast between Marseilles and Toulon and again between
Cannes and Nice. The Jurassic sequence is epicontinental, neritic, with
coralline Tithonian. The structure has been intensely complicated by
folding, thrusting and decollement at a Triassic saline marl series, as in
the Jura (Goguel, 1943; Bailey, 1953). Northwards the Jurassic passes
into deeper-water facies, but is soon hidden by Cretaceous and Tertiary
cover under the basin of the Durance. The deformations to which the
sedimentary mantle has been subjected in this area have been portrayed
in a vivid and original manner by Goguel (1943).
Farther north-east along the Riviera the sea-coast intersects the outer
folds of the Alps between Nice and San Remo. They sweep inland as a
great belt of arcs and turbulent interlacing ruckles, forming the Alpes
Maritimes, Basses Alpes, Alpes du Dauphine and Chaines Subalpines.
At their widest they reach nearly to the Rhone valley opposite Crussol,
then they narrow north-eastwards near Grenoble. The Jurassic stratigraphy
of the part near Grenoble and Chambery has already been
described with the Jura Mountains, which there originate as a virgation of
the Subalpine ranges (Fig. p. 69).
From east to west in a broad band the Jurassic sediments are finegrained
and free from littoral influences. In the east at least, the Lias
is exceptionally thick, while in the west and centre the Tithonian is
poorly fossiliferous and comprises great thicknesses of false breccia
of obviously contemporaneous origin and containing no extraneous
fragments. These peculiarities have usually been attributed to origin
in deep water. Paquier called this band the 'fosse vocontienne' (after
the Vocontes, an ancient tribe), a term adopted by Haug (1891; 1910,
pp. 1086, 1089) who defined it as 'a deep depression where only finegrained
sediments were deposited', and where the Tithonian is 'unquestionably
bathyal', as in many parts of the Mediterranean region. Bathyal
is a vague term, for it is defined by the 'Committee on a Treatise of Marine
Ecology and Paleoecology' (1951, National Research Council, Washington)
as applying to depths 'from 100-200 m. down to somewhere between
2000 and 4000 m. Our present knowledge is inadequate to justify further
146
http://jurassic.ru/