Quaternary palaeohydrological evolution of a playa lake: Salada Mediana, central Ebro Basin, Spain

Abstract

Sedimentary features, mineralogy, bulk geochemical composition, stable isotope analyses and pollen data from sediment cores were used to reconstruct the Late Quaternary depositional evolution of the Salada Mediana playa lake (central Ebro Basin, northeastern Spain). The 150‐cm‐long sediment core sequence is composed of gypsum‐ and dolomite‐rich muds (Lower and Middle sections) and black, laminated, calcite‐bearing sediments (Upper section). The Salada Mediana formed as a karstic depression in the Miocene gypsum substratum during the Late Pleistocene. The Lower section was deposited in a sulphate–carbonate saline lake that ended with a period of desiccation and basin floor deflation. Subsequent deposition (Middle section) took place in a playa‐lake system. Two cycles of lower water table and expanded saline mud flats occurred. The Holocene sequence is missing, probably as a result of aeolian erosion. Sedimentation resumed only a few centuries ago, and saline pan environments dominated until modern times. The Salada Mediana facies succession was mainly governed by fluctuations in the hydrological balance, brine composition, and salinity; however, aeolian processes (detrital input and deflation) and recycling of previously precipitated salts also played a significant role.

Bloedite sedimentation in a seasonally dry saline lake (Salada Mediana, Spain)

“…In the sequence of mineral formation inferred for the basin, sodium sulfates are formed before bloedite precipitation (Auqué et al, 1995;Valero-Garcés et al, 2000a), in agreement with results of evaporation experiments (Auqué et al, 1995;López and Mandado, 2007).…”

“…The lake is dry in summer but the basin floor is covered by surface brines during other parts of the year, with up to about 50 cm thickness of the brine layer (Pérez et al, 1998) composition (Pueyo Mur, 1978/1979Mingarro et al, 1981;Auqué et al, 1995;Pérez et al, 1998;Valero-Garcés et al, 2000a;López and Mandado, 2007).…”

“…In most earlier studies of the Mediana basin, thenardite is mentioned as salt crust component, assumed to be derived at least in part by transformation of a mirabilite precursor (Na 2 SO 4 .10H 2 O) (Pueyo Mur, 1978/1979Mingarro et al, 1981;Auqué et al, 1995;Valero-Garcés et al, 2000a, 2000b. In the sequence of mineral formation inferred for the basin, sodium sulfates are formed before bloedite precipitation (Auqué et al, 1995;Valero-Garcés et al, 2000a), in agreement with results of evaporation experiments (Auqué et al, 1995;López and Mandado, 2007).…”

“…The presence and nature of salts in this basin are described in a number of earlier publications, comprising regional studies with mineralogical data for the surface crusts and the underlying sediments (Pueyo-Mur, 1978/1979Mingarro et al, 1981), and palaeolimnological studies that include some information about the uppermost part of the deposits (Pérez et al, 1998;Valero-Garcés et al, 2000a, 2000b. One experimental study using local brines also provides data for the natural crusts (Auqué et al, 1995).…”

Palynological evidence of the geoecological belts dynamics from Eastern Cordillera of NW Argentina (23° S) during the Pre-Last Glacial Maximum

“…The drier climate could have changed the Laguna Blanca lake into a playa lake system. Playa lake systems are typical of arid regions and are characterized by the reduced thickness of accumulated sediment, the presence of numerous sedimentary hiati, the complexity of evaporite deposition and early diagenetic processes (Valero Garcés et al, 2000). In this context, the scarce representation or even complete absence of the Late Glacial and Holocene sedimentary record could be explained by local geomorphological inactivity or by recent eolian deflation.…”