Arkell.1956.Jurassic..

148 THE ALPS AND NORTHERN CARPATHIANS
Maritimes there is typical bastard marble with Natica leviathon, as in the
northern Dauphine and Jura.]
PURBECKIAN ?
Near the Riviera coast (Alpes Maritimes), the bastard marble with
Natica leviathon is underlain by thick Tithonian limestones, at the top
of which are beds of green and black marl and nodule beds containing
multicoloured pebbles, small gastropods, and Chara, all closely resembling
the Purbeckian of the Jura (Gignoux & Moret, 1937). Doubt has been
cast on the chronological value of these beds, however (in the absence
of more supporting evidence) by the discovery of marls with Chara and
pebbles in the Middle Berriasian of the Chambery area (see p. 87).
TITHONIAN
The Tithonian consists of dolomites and white limestones, hundreds of
metres thick in the south. They build the white Riviera sea-cliffs between
Nice and Mentone, and inland form karstic plateaux cut with canons
as much as 400 m. deep, or in the folded country rise in mural escarpments
and crests almost bare of vegetation. In this southern facies
fossils are rare and ammonites seldom obtainable. Kilian & Guebhard
(1905, p. 817) give a long list of mollusca, echinoids, corals, etc., but only
one ammonite, 'Perisphinctes (indet.)'; but subsequently Upper Tithonian
ammonites have been recorded from the hinterland of Cannes and Nice:
Berriasella lorioli '(Zit.), B. cf. calisto (d'Orb.), B. carpathica (Zit.)
(Lanquine, 1935, pp. 104-5). Unfortunately the levels of these rare finds
relative to the 'Purbeck Beds' of the same area remain to be determined.
In the central and northern areas thicknesses are much less and the
cephalopod facies comes in. The Upper Tithonian with a rich ammonite
fauna as at Aizy near Grenoble is exposed at Claps de Luc in the valley
of the Drome near Die, and near Sisteron, and the list includes Berriasella
lorioli and B. richteri, the two species which led Kilian to the conviction
that this horizon 'is certainly equivalent to the Purbeckian of the Jura'
(Kilian, 1895, pp. 676-9). Beneath comes Kilian's Lower Tithonian,
thick false-breccias and crystalline limestones with Perisphinctids (contiguus,
geron, pseudocolubrinus, etc.) and Pygope janitor ('janitor'' in reference
to its occurrence at the 'Porte de France' at Grenoble).
MIDDLE AND LOWER KIMERIDGIAN
Haug (1891, p. 103) and Kilian followed Neumayr and classed the
Beckeri Zone as Kimeridgian, not Tithonian, but did not distinguish
it from the Pseudomutabilis Zone. As in other regions of the Mediterranean,
however, distinction in the field is difficult, owing to the
similar hard limestone facies, and Lanquine (1935, p. no) lists Hybonoticeras
beckeri among the few Tithonian ammonites, while Kilian
& Guebhard (1905, p. 805) gave a mixed list from the 'Upper Kimeridgian
and base of the Portlandian', and included an Aulacostephanus in their
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