Arkell.1956.Jurassic..

SICILY 2O9
Morphoceras cf. dimorphum (d'Orb.), Sphaeroceras brongniarti (Sow.)
and Spiroceras spp. (Di Stefano & Cortese, 1891, p. 230).
As remarked above, subaqueous volcanic rocks of Middle Jurassic
age are widespread in Sicily, from near Monte Inici in the west to Monte
Iudica, near Mount Etna. They consist chiefly of tuffs, but in places
include agglomerates and submarine basalts. At one place only, Roccapalumba,
near Palermo, have ammonites been found in the tuffs: a
Cadomites sp. and an Oppeliid (Fabiani, 1930; Fabiani & Ruiz, 1933,
pi. ii, 19, 20). Mr Warman twice searched the tuffs at this locality and
sent me from them two good specimens of Cadomites daubenyi (Gemmellaro)
or a closely allied species, a fragment of an Oppeliid like that figured by
Fabiani & Ruiz, and a fragment of a Perisphinctid. The Cadomites makes
an Upper Bajocian date most probable for the volcanic episode.
MIDDLE AND LOWER BAJOCIAN
So many zones have proved to be represented by thin beds in such
limited areas that it would be rash to assume that any zone is missing
altogether in Sicily. So far, however, no trace has been found of the
lower zones of the Upper Bajocian, nor of the upper zone of the Middle
Bajocian (Humphriesianum Zone), and this non-sequence in so many
places may reasonably be connected with upheaval preceding the volcanic
activity.
Beds with Middle and Lower Bajocian ammonites have been found
only in the Trapani district, in the west, where they underlie Posidonia
alpina beds without the intervention of any volcanics. They consist of
dark grey, bedded limestones from which, at the outcrops on Monte
San Giuliano (Monte Erice), have been collected some 50 species of
ammonites and Nautilids ranging from the Opalinum Zone to the Sauzei
Zone inclusive. Phylloceratids are abundant. Of the other ammonites
the commonest are Graphoceratids and Hammatoceratids of the
Murchisonae Zone. Other important genera are Haplopleuroceras,
Zurcheria and other Sonninids, Erycites, Docidoceras longalvum (Vacek),
Otoites, the early Oppeliid Bradfordia (including Amblyoxyites and
lokastelid), Tmetoceras, Dumortieria and Leioceras. The whole agrees
closely with the San Vigilio formation on Lake Garda. (Gemmellaro,
18866; de Gregorio, 1886, pis. i, ii; Renz, 1925, revision, lists, analysis
and pis. i, ii; Kuhn, 1934; Nautilids figured by Tagliarini, 1901).
TOARCIAN AND UPPER PLIENSBACHIAN (DOMERIAN)
In the west these stages are poorly developed and represented by a few
metres of limestone poor in fossils (Renz, 1924) or with brachiopods and
some ammonites (Gemmellaro, 1872-82, p. 53, pis. X-XII). The centre
of interest shifts to the east, where there are up to 300 m. of grey shaly
marls and marly limestone, extremely rich in ammonites, in the neighbourhood
of Taormina. Following basic work by Gemmellaro (1885, 1886a,
1886c), Seguenza (1896) and others, the ammonites have been beautifully
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