Sorbas Basin Explained
The Sorbas Basin is a sedimentary basin around the town of Sorbas in Almeria Province in south-east Spain. It is believed to have been formed by extension, between two fault-bounded blocks which rotated anti-clockwise to take up the compression resulting from Europe's collision with Africa. The basin is filled with turbidites and evaporites of the Tortonian-Messinian ages of the Miocene Epoch.
It is a matter of some debate whether the basin dried out at the same time as the main Mediterranean basins.[1] [2] [3]
Basin fill
The basin is divided into the following members:
- At the bottom of the image, the house is constructed on the steep yellow cliffs of the resistant Azagador Member.
- The lower (whiter) and upper (yellower) Abad Marls, a Tortonian/Messinian series of turbidites featuring pronounced Milankovic (20,000 year precession) cyclicity, allowing chronostratigraphic dating; these fine muds are easily eroded.
- When the sea returned overdeepening the basin, salt water waterfalls eroded a 200 m depression patterned by 30 m deep gullies.[4]
- the Messinian Yesares Member, a gypsum evaporite, forms the steep bluffs at the top of the valley; there is some debate about how conformable its contact with the Abad marls is.
- Pliocene deposits, rest unconformably on the top.
- Complexity of drawdown and reflooding complicate correlation of the ‘Salinity Crisis' stratigraphy.
Basin significance
The basin was separated from the main Mediterranean basin during the Messinian salinity crisis; therefore the timing of the Yesares Member relative to the main basin evaporites is crucial to distinguish between models of how the Mediterranean dried out.
Notes and References
- Riding, R. . Braga, J.C. . Martín, J.M. . 2000 . Late Miocene Mediterranean desiccation: topography and significance of the 'Salinity Crisis' erosion surface on-land in southeast Spain: Reply . . 133 . 3–4 . 175–184 . 10.1016/S0037-0738(00)00039-7 . 2000SedG..133..175R. 1874/1630 . free .
- Braga, J.C. . Martín, J.M. . Riding, R. . Aguirre, J. . Sánchez-almazo, I.M. . Dinarès-turell, J. . 2006 . Testing models for the Messinian salinity crisis: The Messinian record in Almería, SE Spain . Sedimentary Geology . 188 . 131–154 . 10.1016/j.sedgeo.2006.03.002. 2006SedG..188..131B .
- Krijgsman, W. . Fortuin, A.R. . Hilgen, F.J. . Sierro, F.J. . 2001 . Astrochronology for the Messinian Sorbas basin (SE Spain) and orbital (precessional) forcing for evaporite cyclicity . Sedimentary Geology . 140 . 1–2 . 43–60 . 10.1016/S0037-0738(00)00171-8 . 2001SedG..140...43K. 1874/1632 . free .
- Significance of the 'Salinity Crisis' erosion surface on-land in southeast Spain . 10.1016/S0037-0738(98)00115-8 . Robert Ridinga, Juan C. Bragab and José M. Martín . 1999 . Sedimentary Geology . 123 . 1 . 1999SedG..123....1R.