THE MEDITERRANEAN LOWER CRETACEOUS

cf. hitzeli J a c, Costidiscus recticoslatus (d'O r b.), etc. are found among the Aptian
sediments (F u r о n, 1960).
DSDP Site 367 (Leg 41) revealed Kimmeridgian red argillaceous limestones
which overlie basalt, followed upwards by Tithonian-Hauterivian sequence characterized
by cherty limestones and grey marls. The Barremian is represented by claystones,
the Aptian and Albian — by black shales (J a n s a, W i e d m a n n, in:
Von R a d et al., 1982).
Further north, at DSDP Site 368, located to the northwest of the Cape Verde
Islands, Miocene diabasic sills are found among Albian-Turonian black shales.
Data about the Lower Cretaceous are particularly numerous in the continental
margin of Morocco and near the Canary Islands.
At Site 369 to the southwest of the Canary Islands, opposite Cape Bojador, Aptian-Albian
silty marls with nannoplankton are found at the base of the section.
Further north, Site 370, situated on the parallel of Madeira Island in the continental
foot of the Moroccan Meseta, at 4216 m depth of the water, has passed 1176 m
and has revealed a terrigenous Lower Cretaceous (Berriasian-Albian), represented
mainly by turbidites with marl intercalations with nannoplankton, siltstones, sandstones
and rare conglomerate beds. These sediments are of flysch type. They are
dated by foraminifera and nannofossils (Butt, 1982).
An interesting Lower Cretaceous section is discovered at Site 397 between the
Canary Islands and Cape Bojador. The borehole passes 1453 m and reveals in the
lower part Valanginian-Hauterivian aleuritic argillites with siderite concretions.
They contain abundant remains of fishes, echinoderms, cephalopods and gastropods.
The sediments demonstrate a number of deltaic features, which correlate well
with the continental part.
In DSDP-Hole 397-A (from Site 397), Wiedmann (1979) has identified
Neocomites neocomiensis (d'O г b.), Phylloceras (H.) thetys (d'O г b.) and
Protetragonites cf. crebrisidcatus (U h I.), which prove the Valanginian, Hauterivian
and Barremian.
There are several boreholes in the Mazagan Plateau (DSDP-Leg 79). The borehole
at Site 545 reveals a considerable hiatus at the base of the Lower Cretaceous.
Yellow-grey dolomite and calcareous sediments dated to the Barremian-Aptian
directly overlie the Upper Jurassic carbonate platform, followed upwards by green
nannofossil clayey limestones which fill the volume of the Aptian, Albian and Cenomanian
(Von Rad et al., 1982).
The Lower Cretaceous at Site 547 is represented by the upper part of the
Albian Stage, which covers Upper Jurassic limestone breccias. Greenish nannofossil-bearing
claystones and mudstones with common intraformational flat-pebble
mudstone conglomerate layers and slump structures are developed. They are dated
by foraminifera as Upper Albian-Cenomanian (H i n z, Winterer et al.,
1982).
In the area of the Canary Islands (Fuertaventura) the Lower Cretaceous is
represended at its base by cross-bedded siltstones (Vaianginian-Hauterivian), passing
upwards into pelagic radiolarites and limestones (Aptian-Albian), which correlate
with the section at Cape Verde Islands (Maio Island) (Arthur et al., 1979).
Clear dependences are established between the Lower Cretaceous sections in
the investigated part of the Atlantic Ocean and in the outcrops from Northwestern
Africa.
Compared with the prodeltaic facies at Site 397, the Barremian-Aptian sediments
from the Tarfaya — El Aaiun region and in the shelf of Western Sahara have developed
a 1200 m thick complex of terrigenous sediments in deltaic facies (W i e dm
a n n et al., 1978; E i n s e 1 e, Von Rad, 1979). These sediments contain rare
fossils (bivalvs, gastropods, echinids, foraminifera). Bio- and lithofacies indicate
86