Arkell.1956.Jurassic..

BORDERS OF THE MASSIF CENTRAL 73
MIDDLE AND LOWER KIMERIDGIAN (Plate 4)
With the possible exception of the very highest few metres, as just
mentioned, the great mass of marble-like, ruiniform limestones, forming
the upper part of the Mountain of Crussol, and for a considerable distance
below, belong to the Middle and Lower Kimeridgian. The Beckeri Zone
forms the top part, while the base of the Pseudomutabilis Zone falls at
or near the top of the Carriere Mallet, source of most of Fontannes'
ammonites. The Carriere Mallet was worked mainly in the Tenuilobatus
Zone, in which among a wonderful profusion of southern Phylloceratids,
Taramelliceras, Haploceras, Streblites, Glochiceras, etc. (Fontannes, 1879,
pis. i-vii) there occurs an occasional northern element such as Amoeboceras
subtilicaelatum Font. sp. (pi. ii, 7), Rasenia trimera Oppel sp. (pi. ix, 6),
Rasenia emancipata Font. sp. (pi. xi, 8), R. desmonota (Oppel), Prorasenia
stephanoides (Oppel), etc. (Dumortier & Fontannes, 1876, pi. xiv, 2, 4,
pi. xv, 2, 3). Unfortunately the stratigraphical relations of these to the
Ataxioceratids (including Idoceras) and other Perisphinctids has not been
CARRIERE MALLET CHATEAU OE CRUSSOL
6AAHITE TRIAS LIAS BAJ. BATH. LO. CALL. MlD.CALL. LO.OXF. UP.OXF KIM.
UIB0L1TES BED
FIG. 8.—Scale section of the Montagne de Crussol, viewed from the Rhone valley, looking
west. Based on Gignoux, after Riche & Roman, 1921, modified.
determined and probably never will be, since the quarry has been out
of use for many years. The thickness in the quarry is about 33 m. and
some sub-division has been attempted (Roman, 1950, p. 64). Although
many forms of Ataxioceras occur in the quarry, A. lothari (Oppel) with
A. discobolus (Font.), A. polyplocus (Rein.) and other species are said to
occur on a lower horizon in an old quarry at the head of Ravin d'Enfer
(Riche & Roman, 1921, p. 63); this is the lower part of Oppel's Tenuilobatus
Zone, characterized by A. polyplocus and Sutneria platynota in Swabia
(Polyplocus Subzone).
Crussol species from the Tenuilobatus Zone worth mentioning for
their correlation value, and because inadequately placed by Fontannes,
are Sowerbyceras loryi Mun. sp. (D. & F., 1876, pi. v, 2), Streblites
tenuilobatus Oppel sp. (pi. vii, 1), Katroliceras crussoliense Font. sp.
(pi. xiv, 3), Subdichotomoceras lacertosum Font. sp. (pi. xv, 1), Idoceras
spp. (pis. xvi, xvii, 1), and Nebrodites (pi. xvii, 3).
OXFORDIAN (C. 50-70 m.)
At Crussol something less than 30 m. of limestones represent the
Bimammatum Zone and yield the zone-fossil (already recorded by Oppel,
1865); below, about 50 m. of grey marls and marly limestones represent
the Transversarium and Cordatum Zones. Better and more fossiliferous
sections occur at La Voulte, where the Lower Oxfordian is developed in
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