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Depósitos continentais e marinhos na plataforma litoral da região do Porto. Importância da tectónica na sua organização espacial
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One of the most common characteristics of Portuguese littoral is the existence of a planed surface (the so-called "littoral platform"), situated at different altitudes and bordered from the inland by a straight relief, strongly contrasting with that planed surface. This one is generally covered with several outcrops of the so-called Plio-Pleistocene deposits.
Till the eighties this platform has been interpreted as stable staircase of old marine levels, registering in a passive way the eustatic variations. The rigid step bordering it easterly should be a fossil cliff.
However, our study has proved that many of these deposits have a continental origin. These continental deposits have fluvial or
alluvial fan facies and they are lying above 40 meters. Marine deposits seem to be quite rare and they only occupy a small western area, beneath the altitude of 40 meters and
developing into three different marine levels.
There is a rigid step between the two kinds of deposits. We think that the clear geometric separation between these deposits
together with this rigid step, indicates a tectonic origin.
It seems that the sea must have touched only the western part of this surface, when neotectonic movements lowered it down.
There are more evidences for neotectonic movements: a) there are faults (mainly inverse faults) affecting the higher deposits of this littoral platform; b) the same marine level seems to appear at different altitudes, developing an irregular pattern with a general trend dipping from the North to the South.
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littoral platform marginal relief alluvial fans marine deposits Quaternary neotectcnics