Arkell.1956.Jurassic..

WESTERN AND CENTRAL ALPS 157
Lytoceratids and Haploceratids, and somewhat doubtful Perisphinctids, a
special feature is the presence of Simoceratids : Simoceras admirandum
Zittel, Nebrodites pulchellum (Gem.), N. aff. agrigentinum (Gem.), and the
peculiar Rogoznik form Simocosmoceras adversum (Oppel). Among
the Perisphinctids Blanchet records transitorius, contiguus, geron and
pseudocolubrinus.
The Rogoznik fauna does not agree with that of the Lower Tithonian
of the French and Swiss Alps and must therefore fall between the true
Upper and Lower Tithonian, namely into the gap already postulated
by Mazenot, and indicated in the correlation table on p. 91.
LOWER TITHONIAN AND KIMERIDGIAN
The Guillestre Marble contains ammonites (including Hybonoticeras
and Epipeltoceras) which indicate that it includes representatives of the
Tithonian, Kimeridgian and Upper Oxfordian, down to the Bimammatum
Zone (Blanchet, 1929, p. 50). In the High Limestone Alps also the
uppermost Oxfordian, Kimeridgian and Lower Tithonian are represented
in a still thicker limestone series, the Quintnerkalk, 300-400 m.
thick, at the top of which is the Canisfluh ammonite bed described above.
In many places this thick formation is magnificently exposed, but fossils
are difficult to find owing to weathering and difficult to extract owing to
hardness of the rock. In the Mechtal Alps (near the Sarner See, south of
Lucerne), however, about 90 m. from the top of the Quintnerkalk there
is another condensed ammonite bed at Hohmatt. It is 10-50 cm. thick
and ironshot, and contains at least 3000 ammonites to the cubic metre,
but they are all small and difficult to extract (Rod, 1937, 1946). Numerically
by far the most abundant are Haploceratids (mainly H. staszycii
Zeuschn. sp.), after which come a dozen species of Phylloceratids, then,
a long way behind, Perisphinctids, with a few Oppeliids, Aspidoceratids
and Lytoceratids. As shown by Rod (1946), most of this fauna is a condensed
version of the Beckeri Zone, or Acanthicus Beds (upper part)
of the Middle Kimeridgian, and he thinks it may even comprise representatives
of the Pseudomutabilis Zone and Tenuilobatus Zone (Streblites
tenuilobatus itself is listed). But in addition Rod believes that the Perisphinctids
include Sublithacoceras cf. dicratus (Schneid), S. kyphosus
(Schn.) and S. cf. callodiscus (Schn.) (cf. dicratus figured, pi. xiv, fig. 1),
all of the Ciliata Zone, Neuburg Beds, and he suggests that these may be
precursors of the Franconian type forms. In any case, the difference in
age between Beckeri Zone and Ciliata Zone may not be great, according
to Roll's findings (see p. 110). The Hohmatt condensed bed is
valuable as showing close connexion between the Neuburg fauna and
Kimeridgian faunas and, in contrast, a gap of at least 100 m. (the top of
the Quintnerkalk is not reached) up to the Upper Tithonian fauna: a
result consistent with the correlation shown on p. 91.
A suite of typical Lower and Middle Kimeridgian ammonites was
figured from the French and Swiss Alps by Favre (1877).
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