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Facies changes and paleogeographical implications in the Serravallian of the Lagos-Portimão Formation (Praia da Rocha, southern Portugal)

Dabrio, Cristino J. and González Delgado, José Ángel and Armenteros Armenteros, Ildefonso and Civis Llovera, Jorge and Pais, J. and Alonso Gavilán, Gaspar and Legoinha, P. (2008) Facies changes and paleogeographical implications in the Serravallian of the Lagos-Portimão Formation (Praia da Rocha, southern Portugal). Geotemas, 10 . pp. 131-134. ISSN 1576-5172

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Abstract

Detailed stratigraphic control and lateral tracing of facies between Praia da Rocha and the
adjacent Praia do Vau evidenced that, although the thickness of layers remains essentially homogeneous,
the internal composition, grain size and fossil contents change noticeably. Three orders of sequences were
distinguished. Smaller-scaled sequences were produced by storms (event beds). Second order sequences
are interpreted as generated by a Milankovitch forcing. The larger scale one is observed by the piling of
subunits, with assumed eustatic forcing. The prevailing W/SW orientation of paleocurrents measured, and
the overall model of dispersion systems, fit in an estuarine pattern of circulation during the Middle
Miocene in the North-Betic Strait. Local, gentle diapiric up-warping between Portimão and Albufeira also
contributed to water-depth and facies changes.
[RESUMEN]
Un control estratigráfico detallado y el seguimiento lateral de los cambios de facies entre las
Playas da Rocha y do Vau pone de manifiesto que, aunque las potencias de las capas se mantienen poco
más o menos constantes, la organización interna, el tamaño de grano y el contenido fosilífero varía
notablemente. Se distinguen tres órdenes de secuencias: las de menor escala son capas de evento
producidas por tormentas, las de segundo orden se interpretan como originadas por cambios orbitales de
tipo Milankovitch y las de mayor orden, marcadas por el apilamiento de unidades, se consideran de
origen eustático. El sentido de las paleocorrientes, predominante hacia el W/SW, y la distribución de los
sistemas de dispersión encajan en el modelo de circulación de tipo estuarino propuesto para el Estrecho
Nord-Bético durante el Mioceno Medio, aunque algunos abombamientos diapíricos entre Portimão y
Albufeira contribuyeron a los cambios de profundidad y de facies

Item Type:Article
Uncontrolled Keywords:Lagos-Portimão Formation, Serravallian, Algarve, Portugal, Formación Lagos-Portimão, Serravalliense
Subjects:Sciences > Geology > Stratigraphic geology
ID Code:10706
Deposited On:21 May 2010 09:16
Last Modified:25 Jan 2011 09:33

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