Environmental problems and geological implications derived from evaporite dissolution in the Barbastro salt anticline (NE Spain) |
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Authors: | P Lucha F Gutiérrez J Guerrero |
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Institution: | (1) Departamento de Ciencias de la Tierra, Edificio Geológicas, Universidad de Zaragoza, 50009 Zaragoza, Spain |
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Abstract: | The halite-bearing Barbastro Formation crops out in the core of the Barbastro Anticline (Ebro Tertiary Basin). This anticline
is traversed perpendicularly by some of the most important Pyrenean drainages such as the Cinca and Noguera-Ribagorzana Rivers.
The terrace sequences of these fluvial systems have been used as markers to identify and assess dissolution-induced subsidence
and salt tectonics. In the limbs of the anticline, terrace deposits underlain by detrital bedrock do not show any evidence
of deformation and have a consistent thickness of less than 10 m. The deposits of certain terrace levels of the Noguera-Ribagorzana
River and its tributary, the Lo Reguer Creek, are locally thickened filling basins generated by dissolution-induced synsedimentary
subsidence up to several kilometers long and more than 100 m deep. Conversely, terraces of the Cinca River do not show anomalously
high thicknesses, but local uplifts related to differential upward flow of the halite-bearing bedrock. Locally, a minimum
uplift rate of 0.3 mm/year has been estimated from a 64-ka terrace tilted away from the valley. The subsidence hazards occur
chiefly in areas where the ground receives artificial water recharge. Serviceability of some canals has been notoriously affected
by evaporite karstification. The problem has been mitigated to acceptable levels by grouting. Numerous buildings of Ivars
de Noguera are severely damaged by dissolution subsidence, and possibly, by hydrocompaction of gypsiferous silts. The pipe
network has been replaced to ameliorate the subsidence risk. In the Cinca River valley, cavities with a total volume of about
180,500 m3 have been created by solution mining at depths greater than 500 m. No investigation methods are applied in the brine field
to monitor the distribution and evolution of artificial voids. Substantial increase in salinity of the Cinca River is another
evidence of subjacent evaporite dissolution. |
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Keywords: | Subsidence hazard Halokinesis Solution mining Ebro Basin |
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