The Messinian record of the outcropping marginal Alborán basin deposits: significance and implications
Identificadores
URI: http://hdl.handle.net/10481/22940Metadata
Show full item recordEditorial
College Station, TX (Ocean Drilling Program)
Materia
Sorbas Spain Basins Messinian Evaporites
Date
1999Referencia bibliográfica
Martín, J.M.; Braga, J.C.; Sánchez-Almazo, I. The Messinian record of the outcropping marginal Alborán basin deposits: significance and implications. Proceedings of the Ocean Drilling Program, Scientific Results, 161: 543-551 (1999). [http://hdl.handle.net/10481/22940]
Sponsorship
This work was supported by DGICYT (Spain) Project PB93-1113 and by “Fundación Ramón Areces” Project: “Cambios climáticos en el sur de España durante el Neógeno.”Abstract
The Messinian record of marginal Alboran basins, such as the Sorbas Basin in southern Spain, consists of a shallow-marine
succession with intercalated evaporites. The pre-evaporite sequence comprises a bryozoan-bivalve, temperate-carbonate unit
overlain by tropical carbonates. The latter, in turn, consists of two superimposed units: a bioherm unit with coral (Porites, Tarbellastraea, and Siderastraea) and algal (Halimeda) mounds, and a coral (Porites)-stromatolite fringing reef unit. Climatic
fluctuations in the Alboran area, linked to the Neogene glacial-interglacial oscillations, are thought to be responsible for the
change from temperate to tropical conditions.
Evaporites are mainly selenite gypsum deposits. The first post-evaporite unit is a mixed siliciclastic-carbonate marginal
deposit, with small coral (Porites) patches and huge microbial (stromatolite and thrombolite) domes, changing basinward to
silts and marls containing planktonic foraminifers.
An incised erosion surface was scoured on top of the pre-evaporitic fringing reef unit. This erosion surface formed during
drawdown and desiccation of the Mediterranean Sea, when huge masses of salt were deposited in its center. Deposition of gypsum at the very margin of the Alboran Sea took place later in small, barred, satellite perched basins. In these silled basins
marine incursions became more and more frequent until a full connection with the Mediterranean Sea was established by the
end of the Messinian. Reflooding was completed during the Messinian, as demonstrated by the marine marls with planktonic
foraminifers found on top of the evaporites. This situation is comparable to that of the western Mediterranean (DSDP Site 372;
ODP Site 975), where the upper evaporites are directly overlain by Messinian marls with planktonic foraminifers. During the
initial stages of marine recolonization, microbes coexisted with, but outcompeted, the normal marine biota. This resulted in the
widespread proliferation of microbial carbonates (stromatolites and thrombolites).