Arkell.1956.Jurassic..

ANDALUSIA 245
in the Balearic Islands. This line is interpreted as the front of a complex
of nappes (the Subbetic) which has travelled about 20 miles northwards,
overriding the autochthonous but often acutely folded foreland (the
Prebetic). The Prebetic zone forms the surface in the east, spreading
out over the edge of the Meseta and passing north into the Iberian
Ranges, but towards the west it sinks gradually beneath the basin of the
Guadalquivir.
The Subbetic zone of nappes has an intensely complex structure,
including klippes, one of which forms the Rock of Gibraltar (Bailey, 1953),
but the Mesozoic rocks of which it is composed are little altered and often
highly fossiliferous. To the Subbetic (including a northern zone of
nappes formerly known as Penibetic) belong all the best-known fossil
localities. The series is complete from Lower Lias to Cretaceous; the
whole of it from Pliensbachian to Maestrichtian in Mediterranean facies.
At any one locality, however, the sequence is often fragmentary, one or
other part cut out by tectonic movements; and the whole pile rests on
a sole plane over German-type Trias (plate 10 and figs. 29, 30).
To the south of the Subbetic zone, in a broad marginal band along
the coast and including the Sierra Nevada, runs the Betic zone of fartravelled
nappes, in which the rocks are more or less metamorphosed.
They consist largely of Alpine-type Trias and Palaeozoics. No Jurassic
has been recognized. The crystalline schists of the Sierra Nevada show
through the surrounding Betic nappes as a tectonic window, eroded on a
culmination. Similarly, west of Malaga, windows of Trias belonging
to one of the Betic nappes project through a higher Palaeozoic and
crystalline nappe. (Fallot, 1930, revised Fallot, 1948.)
Much work remains to be done before the Mesozoic preliminary
disturbances of the Alpine storm can be deciphered in detail in this region,
but local lacunae within the Middle and Upper Jurassic are suggestive,
and early Kimeridgian and Tithonian transgressions certainly occur.
Widespread Neocomian transgression in the east, claimed by Brinkmann
& Gallwitz (1933), is denied by Fallot (1934, pp. 81-6, 115), who states
that the supposed oversteps at the base of the Cretaceous are tectonic
contacts. The main formation of the Betic nappes is dated to the Lower
Eocene (and is therefore earlier than the Pyrenean folding), but the highest,
or Malaga nappe, is believed to be Oligocene, as are the earliest movements
in the Subbetic zone. Thereafter there was a widespread
Burdigalian transgression, which in some places was initiated in the
Aquitanian; and this was followed by a major orogeny between the
Burdigalian and Vindobonian in the Subbetic zone. The Vindobonian
is everywhere transgressive. Finally, the whole region was broadly
refolded in the post-Pontic Pliocene. These latest movements involved
all the Betic Cordilleras and adjacent parts of the Meseta. (Fallot, 1944.)
The sound foundations of our knowledge of the Jurassic laid by
Bertrand & Kilian (1889) and Kilian (1889) for the west and centre,
and byNickles (1896) for the east, have been built upon especially by
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