THE MEDITERRANEAN LOWER CRETACEOUS

14.3. Sardinia
The Lower Cretaceous is developed in three regions of the island: Nurra — in the
northwestern part, San-Antioco — in the southwestern part, and Dorgali—Orosei—Siniscola
— in the northeastern part. The section at Orosei is most representative
(D i e n i, M a s s a r i, 1965a, b;Wiedmann, Dieni, 1968).
The series is also well exposed in the Tuttavista Mountain, west of Orosei. Its
base is connected with carbonate sediments which pass from the Tithonian. Lagoon
environments are discovered episodically in the uppermost part of the carbonate
complex.
At the top of the reef complex there are calcarenites of littoral type with
oolites, remnants of corals, algae (Lithocodium sp.), Trocholina alpina (Leu p.),
T. elongata (Leu p.), which belong to the Berriasian.
Upper Valanginian calcarenites and siliceous marls with Neocomites neocomiensis
(d'O r b.) and Teschenites teschenensis (U h 1.) overlie the denuded surface of
the Tithonian-Berriasian limestones. These marls also contain clastic material with
Exogyra couloni (D e f г.), serpulae, ostracods, which are of shallow-sea character
with estuary influences.
The Hauterivian is represented by a monotonous formation of limestones,
in some places with flint. Among them the following species have been found : Acanthodiscusradiatus
(В г.), A. pseudoradiatus (B a u m b.), A. cf. bernensis (B a u m b.),
Leopoldia cryptoceras (d'O r b.), L. leopoldi (d'O г b.), Leopoldia sp., Oostrella
cultrata (d'O г b.), Oosterella spp., Crioceratitessablieri(A s t.), С. sornayi (S а г к.),
Spitidiscus rotula (S о w.), etc.
The Barremian comprises oolitic limestones and calcarenites which pass upwards
into subreef bioclastic limestones of Urgonian type. They contain different
foraminifera, most frequent among them being the Orbitolinidae: Orbitolinopsis
flandrini M о u 1 g., O.'cuvillieri M о u 1 1., O. elongatus Dieni, Massari,
Orbitolina conoidea-discoidea Gras. There are also remains of Dasycladacea:
Lithophyllum shebae E 11., Gayeitxia sp., Munieria baconita D e e c, Actinoporella
podolica A 11 h., Salpingoporella dinarica R a d., Clypeina sp., Bacinella irregularis
R a d., etc.
The Aptian starts with limestones, silicified in some places. Intraformational
breccias with glauconite and phosphorite concretions are developed locally. Brachiopods,
bivalvs and rare ammonites occur most frequently among them. Above
them follow clayey limestones which pass into marls with cherty concretions. They
contain Deshayesites deshayesi (Ley m.), Praeglobotruncana (Hedbergella) sp.
and' Conorotalites cf. bartensteini aptiensis (Bet t.), which characterize the Bedoulian
Substage. The Gargasian is represented by glauconitic marls at the base
and by clayey limestones with flint in theupperpart.lt is characterized by : Acanthohoplites
cf. bigoti (S e u п.), Colombiceras tobleri (J а с), C. caucasicum tyrrhenicum
W i e d., Dieni, Neohibolites semicanaliculatus (В 1.), N. ewaldi (S t г.),
N. spicatus S w i n п., Orbitolina sp., etc. The Clansayesian comprises clayey limestones
with cherty concretions. It is characterized by: Acanthohoplites abichi
(Ant h.), A. nolani (S e u п.), A. quadratus (С о 1 1.), A. subangulicostatus S i n z.,
Neohibolites strombecki (M ii 11.), N. aptiensis К i 1., etc.
The Albian is represented by clayey limestones. Calcareous conglomerates are
developed locally in the upper part. It is characterized by extremely rich ammonite
association: Phylloceras spp., Protetragonites spp., Eogaudryceras spp., Kossmatella
spp., Tetragonites spp., Hamites spp., Lechites spp., Anisoceras spp., Ostlingoceras
spp., Puzosia spp., Hysteroceras spp., Dipoloceras cf. rectangulare Spath, Mortoniceras
nanum Spath, Mortoniceras spp., Stoliczkaia notha (See 1.), S. dorsetensis
Spath, Neohibolites spp., etc. (W iedmann, Dieni, 1968).
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