Late Messinian coastal barrier and washover fan sedimentation in Sorbas (SE Spain)

Deposition of washover fans in coastal settings are related to accommodation space, slope of the basin margin, and coeval changes of sea level. Some preliminar y models of development and stacking of sand bodies are presented. [RESUMEN] El depósito de washover fans en áreas costeras está relacionado con el espacio de acomodación disponible, la pendiente del margen de cuenca y los cambios coetáneos de nivel del mar. Se ofrecen modelos preliminares del desarrollo y apilamiento de cuerpos arenosos

Uplift history of a Betic fold nappe inferred from Neogene-Quaternary sedimentation and tectonics (in the Sierra Alhamilla and Almeria, Sorbas and Tabernas Basins of the Betic Cordilleras, SE Spain)

Structural, stratigraphical and sedimentological studies of the Alhamilla region show that the Sierra Alhamilla was elevated relative to the surrounding basins by open folding towards the end of the Tortonian period (about 7 Ma ago) and before the onset of Messinian sedimentation. The main arguments are: (1) the dominant current direction in the Neogene cover changes from southward to southeast- and southwestward during the Late Tortonian, (2) Late Tortonian seismites suggest contemporaneous major tectonic activity which is contrasted by low tectonic activity during the Messinian, (3) Messinian reefs colonise Nevado-Filabride basement exposed (near Polopos) in the eroded hinge of the Alhamilla Anticlinorium, (4) the Northern Boundary Fault which is interpreted to be cogenetic with the formation of the Alhamilla Anticlinorium transects Tortonian sediments but is covered (near Cantona) by unfaulted Messinian reefs, and (5) the base of an almost non-tectonised Messinian succession (in the Sorbas Basin) unconformably overlies an erosion surface of folded Tortonian sediments, Neogene uplift of the Alhamilla region is interpreted here to be due to isostatic recovery after the emplacement of the Alboran Diapir between 20 and 25 Ma ago. Estimates of the average uplift rates vary between 0.7 to 0.5 mm a-' for the Miocene and 0.15 to 0.1 mm a-t for the Pliocene and Quaternary. Pliocene and Quaternary uplift rates are almost identical to the sedimentation rates of 0.23 to 0.2 mm a-' estimated previously for the Alboran Basin

Uplift history of a Betic fold nappe inferred from Neogene-Quaternary sedimentation and tectonics (in the Sierra Alhamilla and Almeria, Sorbas and Tabernas Basins of the Betic Cordilleras, SE Spain)

Structural, stratigraphical and sedimentological studies of the Alhamilla region show that the Sierra Alhamilla was elevated relative to the surrounding basins by open folding towards the end of the Tortonian period (about 7 Ma ago) and before the onset of Messinian sedimentation. The main arguments are: (1) the dominant current direction in the Neogene cover changes from southward to southeast- and southwestward during the Late Tortonian, (2) Late Tortonian seismites suggest contemporaneous major tectonic activity which is contrasted by low tectonic activity during the Messinian, (3) Messinian reefs colonise Nevado-Filabride basement exposed (near Polopos) in the eroded hinge of the Alhamilla Anticlinorium, (4) the Northern Boundary Fault which is interpreted to be cogenetic with the formation of the Alhamilla Anticlinorium transects Tortonian sediments but is covered (near Cantona) by unfaulted Messinian reefs, and (5) the base of an almost non-tectonised Messinian succession (in the Sorbas Basin) unconformably overlies an erosion surface of folded Tortonian sediments, Neogene uplift of the Alhamilla region is interpreted here to be due to isostatic recovery after the emplacement of the Alboran Diapir between 20 and 25 Ma ago. Estimates of the average uplift rates vary between 0.7 to 0.5 mm a-' for the Miocene and 0.15 to 0.1 mm a-t for the Pliocene and Quaternary. Pliocene and Quaternary uplift rates are almost identical to the sedimentation rates of 0.23 to 0.2 mm a-' estimated previously for the Alboran Basin

Late highstand patterns of shifting and stepping coastal barriers and wasgover-fans (late Messinian, Sorbas Basin, SE Spain).

The late Messinian Sorbas Member, up to 75 m thick, consists in its type area of a parasequence sel of three prograding coastal barriers (sequences I-III), associated With lagoon and washover sediments. Around the town of Sorbas these strata can be studied exceptionally well due 10 absence of burrowing by raised Messinian salinities and exposure along a network of up to 30 m deep canyons. Fifteen vertical sections were logged and careífully correlated. This permits to reconstruct and discuss pattems of relative sea-level movements between decímetres. up to 15 m within a parasequence. Excellent examples of non-tidal transgressive facies are characterized by lagoon and washover sedimenls instead of The usual combinatíon of washover and tidal deposits (channel and flood-tidal delta). Implications for the sandstone connectivity are given. The lower two sequences Are deposited in a relatively large tectonically enhanced wedge-shaped accommodation space. The show both fining-up, deepening sequences, followed by prograding coarsening-up shoaling sequences and can be compared to the c1assical parasequences of the Westem Interior Basin (USA). Progradation of sequence II was intemlpted by a major slide event (most likely triggered by an earthquake), which caused more than 400 m seaward slumping of a stretch of 1 km of coastal sands. The architecture of sequence III is more complex due to limited accommodation space characterístic for the late híghstand, so that this setting was very sensitive to sea-level fluctuations. This resulted in an intricate pattem of juxtaposed and superposed lagoonal muds, washover üms and swash zones. So-called "stranded" coastal barriers occur, which were lef behind after seaward Jump of the coastline over more than 1.5 km during forced regression. The pattem of reconstructed sea-level positions is weIl comparable to the sequential partem shown by the correlated equivalent, along the northem basin margin, which belong to the so-called Terminal Carbonate Complex. The problem of ranking the complex sequence III as one or more parasequences and it, consequences for cyclostratigraphy are shortly discussed. Two models of washover formation are given, respectively during more rapid and more slow sea-level rise. The intluence of synsedimentary folding on the location of barriers is discussed and also the source arca of extra and intraclasts supplied to barriers and washovers. After deposition of the Sorbas Member the sea withdrew from the Sorbas Basin, probably as a result of the majar downdrop in lhe Mediterranean at the maximum colation during the Salinity Crisis. It 15 suggested that the semi-enclosed selting of the basin resulted only in límited localized eros ion, in contrast to the deeper adjacent Vera Basin, which was more open to the Mediterranean