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Gruta da figueira brava (Arrabida): Geological setting
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The Arrabida Mountain Range is the best example in Portugal of alpine movements.
During Miocene times the Arrabida chain acquired the present structural set
up: overthrusting accidents striking ENE-WSW and N-S or NNE-SSW sinistral
lateral ramps. The main tectonic phases occurred about 17 Ma and somewhat less
than 16 Ma.
The Miocene deposits, mainly biocalcarenites, are middle Burdigalian and
Langhian in age.
During the Pleistocene the sea erosion cut several terrasse levels. Scattered
remnants of conglomerates corresponding to the 12-15 and to 5-8 meters marine
terrasses are ascribed to the last interglacial and to the beginning of the Wiirm glaciation
(= 100000 years, Tyrrhenian II and III). The 5-8 meters terrasse, which is of particular
interest, was deposited in a narrow marine erosion platform; the corresponding
deposits tend to fill the entry of the caves excavated in the sea cliffs during the Upper
Pleistocene such as Lapa de. St" Margarida and Figueira Brava Cave. These holes,
protected by overhanging parts of the cliffs as a sort of ceiling, were good shelters
forman.
With the advance of the Wiirm glaciation the sea level was progressively going
down. About 30000 years ago, the 5-8 meters platform and the caves dug in the cliffs
were elevated as related to an extensive coastal plain. The sea level was ca. 60 meters
below the present level (Miskovski, 1987). The human communities found in these
territories an excellent hunting ground. The Santa Margarida and Figueira Brava
caves were thus natural shelters. A large number of remnants of their occupation are
preserved such as shells, animal bones, a few Neanderthal remnants as well as lithic
and bone implements. 14C (and U series) dating indicate an age about 30000 years for
level 2 where archaeologic remnants were exploited.
Descrição
Separata do Tomo XXXVIII das Memories da Academia das Ciencias de Lisboa (Classe de Ciencias)
Palavras-chave
Miocene Pleistocene Portinho da Arrabida Figueira Brava cave Portugal