Arkell.1956.Jurassic..

TOARCIAN (150-300 m.)
PORTUGAL 241
The Toarcian is best known from Choffat's detailed work at Thomar,
north of the Tagus (Choffat, 1908; brachiopods revised by Dubar, 1932,
p. 30). The succession of ammonite horizons is as follows:
Thin bed with Pecten pumilus (o- 5 m?)
Limestone with Dumortieria aff. dumortieri (Th.) and numerous
Pleydellia ('Lioceras belonging apparently to L. aalense'). (At least 10 m.)
Marly limestones and limestones with numerous Rhynchonella cf.
cynocephala; Dumortieriae, Leioceras, Brasilia [?], Hammatoceras procerinsigne
(Vacek), H. cf. subinsigne (Oppel). (10 m.)
Marly limestones with Hammatoceras insigne and Polyplectus cf.
discoides. (5-8 m.)
Limestone with abundant H. insigne, also Grammoceras fallaciosum
(Bayle), Polyplectus discoides (Zieten), Dumortieria sp., Catacoeloceras
cf. crassum. (2 m.)
Yellow limestones with a few corals. (7- 5 m.).
Middle Toarcian marls, marly limestones and limestones with Hildoceras
bifrons, Dactylioceras annulatum and many other fossils. (70 m.).
Lower Toarcian marls and limestones with Dactylioceras annulatum,
D. braunianum and other spp., Harpoceras falcifer (Sow.) and H. grunozvi
(Hauer). Spiriferina rostrata, Rhynchonella tetrahedra, etc. (16 m.)
Thin bed with numerous Spiriferina rostrata, R. tetrahedra and Aulacothyris
resupinata.
At Peniche the basal beds of the Toarcian are as follows (Mouterde,
1953); this is an extremely important sequence, as will be seen.
Bed. 16. Marls with small brachiopods and Dactylioceras helianthoides
Yokoyama, D. attenuatum (Simpson), D. sp., Catacoeloceras sp.
Bed 15c Abundant Dactylioceras aff. crassulosum (Simpson), D. cf.
attenuatum (Simpson), D. cf. mirabile Fucini, Harpoceras sp. (coarsely
ribbed), Protogrammoceras madagascariense (Thevenin), Ovaticeras cf.
ovatum (Y. & B.) and ? Canavaria sp.
Bed 15a". No ammonites.
The P. madagascariense in bed 15c is noteworthy, since this species
occurs with Bouleiceras in Madagascar and Arabia. More recently
Boukiceras itself has been discovered in Portugal, 3 km. south of Coimbra,
again associated with Protogrammoceras madagascariense and this time at
last dated unequivocally to the Lower Toarcian, since it overlies beds with
Dactylioceras helianthoides, D. semicoelatum and Leptaena (Dubar &
Mouterde, 1953; Mouterde, 1954). The genera Peronoceras, Paroniceras
and Frechiella also occur north of Coimbra (Renz, 1912; Meister, 1914).
PLIENSBACHIAN
The succession at Peniche given above is continued downwards by
more marls and marly limestones containing the Arieticeras ('Emaciaticeras')
and Canavaria ('Tauromenia') fauna of Sicily and the Apennines.
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