Património Geológico de Portugal

Inventário de geossítios de relevância nacional

Asseca

Categoria temática:Tectono-estratigrafia meso-cenozóica do Algarve

Proponente(s):Mário Cachão, Pedro Terrinha, Delminda Moura

Contacto:mcachao@fc.ul.pt, pedro.terrinha@lneg.pt, dmoura@ualg.pt

Região:Algarve

Município:Tavira Freguesia:Santo Estevão

Área do Geossítio (aprox.):13000 m2

Coord. Geográficas:37.1550000,-7.6963889

Área de protecção:0 m2


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Regime de propriedade:privado

Regime de protecção ambiental:
Incluído noutros regimes de protecção- em actualização

Avaliação quantitativa do valor científico (0-100):67.5

Avaliação quantitativa da vulnerabilidade (100-400):160

Justificação do valor científico:
The Asseca calcareous tuff consists of a system of three water falls (Torre, Paul and Pego do Inferno) of approximately 10m in height built up in calcareous tuffs. The morphology of each one of the waterfalls is rather different and only at Pego do Inferno (transl.: Abyss of Hell) the waterfall is well preserved and is made up of only one escarpment of more than 10m high. The absolute age of the tuffs is under determination by the relative position of the calcareous tuff system with respect to the surrounding stratigraphic units indicate Quaternary age possibly early Holocene.
The Asseca calcareous tuffs formed along an E-W trending fluvial valley (Ribeira da Asseca) carved on the soft marls of the Lowermost Jurassic (Hettangian). The valley is bound on its northern side by the Carboniferous age meta-sediments and on its southern side by the volcanics and limestones of the Lower Jurassic. The calcareous tuffs formed natural barriers that limited a lagoonar sytems. The barriers consist of an accumulation of calcareous tuffs made up of calcitized external mould of upright and recumbent macrophytes, speleo-thems and clasts and boulders of country rock cemented by calcareous tuff and calcite.
The mapping of the Asseca calcareous tuffs (Clavijo, 2003, unpublished report) showed that this system corresponds to the fluviatile models of Pedley (1990) with local development of lacustrine and palludal facies and dominance of the barrage facies. The existence of N-S trending faults active faults in this region has also been suggested to be at the origin of the formation of the waterfalls.
The Asseca calcareous tuffs system is no longer in activity as shown by the erosion, karstification and lack of living fauna and flora equivalent found in the lagoonar marls and waterfall tuffs.

Outros valores e sua justificação:

Observações:

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