Publication: Petrografía de los depósitos arenosos fluviales y costeros en la Península de Tánger: implicaciones sobre la dinámica fluvial y litoral
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Publication Date
2005
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Sociedad Geológica de España
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Abstract
El estudio petrográfico de los depósitos fluviales y litorales de la vertiente atlántica de la Península de Tánger ha permitido el análisis de las relaciones entre la dinámica fluvial y litoral dentro del marco geodinámico de la cordillera del Rif y su posterior comparación con su homólogo bético. Las cuencas fluviales se alinean con las direcciones estructurales de la cordillera y van haciéndose más extensas hacia el Sur, a medida que se expande el arco rifeño. Las características cuarzolíticas de las arenas fluviales reflejan su origen en los mantos numídicos y en las zonas internas rifeñas y alcanzan progresivamente una mayor madurez a lo largo de su recorrido. En su desembocadura, se produce un enriquecimiento en carbonatos al cortar los ríos las plataformas lumaquélicas costeras. Las arenas playeras, en contraste, presentan gran homogeneidad y madurez mineralógica, debido a la alta dinámica litoral atlántica. Estos datos demuestran una gran similitud de petrofacies con las arenas fluviales y litorales de la cordillera Bética, aunque difiere la mayor abundancia de feldespatos en las arenas béticas, que drenan directamente rocas cristalinas y metamórficas. Las arenas costeras atlánticas son muy similares en ambas cordilleras, frente a la escasa madurez mineralógica que presenta la costa bética mediterránea por su menor dinámica litoral.
The present paper deals with the petrological study of fluvial and littoral deposits of the Tangier Peninsula Atlantic catchments (Morocco). It allowed us to establish relationships between littoral and fluvial dynamic in the Rif Cordillera geological frame and, further on, to compare it with equivalent sediments on the Betic Cordillera (Iberian Peninsula). Fluvial basins are elongated following the range main thrust structures, and enlarge towards the South, according to the Rif arch expansion. Fluvial sands are quarzolitic, with a maturity increase downstream, showing its origin in the Rif Internal Domain and Numidic flysch. Carbonate enrichment occurs on river mouths, as rivers incise on the Pleistocene lumaquelic platforms. Beach sands mineralogy, on the other hand, is homogeneous and mature, due to the strong Atlantic Ocean dynamic. This petrofacies is similar to the Betic fluvial and littoral sands ones, even though the Iberian sands are rich in feldspars as result of their granitic and metamorphic rocks provenance. Atlantic coastal sands are rather similar on both sides of the Gibraltar strait, by opposite to the poor mineralogical maturity of Betic Mediterranean sands related to a weak coastal dynamic.
The present paper deals with the petrological study of fluvial and littoral deposits of the Tangier Peninsula Atlantic catchments (Morocco). It allowed us to establish relationships between littoral and fluvial dynamic in the Rif Cordillera geological frame and, further on, to compare it with equivalent sediments on the Betic Cordillera (Iberian Peninsula). Fluvial basins are elongated following the range main thrust structures, and enlarge towards the South, according to the Rif arch expansion. Fluvial sands are quarzolitic, with a maturity increase downstream, showing its origin in the Rif Internal Domain and Numidic flysch. Carbonate enrichment occurs on river mouths, as rivers incise on the Pleistocene lumaquelic platforms. Beach sands mineralogy, on the other hand, is homogeneous and mature, due to the strong Atlantic Ocean dynamic. This petrofacies is similar to the Betic fluvial and littoral sands ones, even though the Iberian sands are rich in feldspars as result of their granitic and metamorphic rocks provenance. Atlantic coastal sands are rather similar on both sides of the Gibraltar strait, by opposite to the poor mineralogical maturity of Betic Mediterranean sands related to a weak coastal dynamic.