Juan Ignacio Santisteban

Environmental and geochemical record of human-induced changes in C storage during the last millennium in a temperate wetland (Las Tablas de Daimiel National Park, central Spain)

Las Tablas de Daimiel National Park has experienced many hydrological and ecological modifications through out its history, both of natural as well as anthropogenic origin, which have affected its carbon storage capacity and carbon fluxes. The study of those variations has been carried out by the analysis of its sedimentary record (geochemistry and pollen) and historical data. The natural changes have a wider variation range than the anthropogenic ones, showrepetitive patterns and the system reacts readjusting the equilibrium among its components. Anthropogenic effects depend on the direct or indirect impact on the wetlands of change and its intensity. In addition, the anthropogenic impacts have the capacity of breaking the natural balance of the ecosystem and the internal interactions.

Mapping geological stages of climate-dependent iron and clay weathering alteration on lithologically uniform sedimentary units using Thematic Mapper imagery (Tertiary Duero Basin, Spain).

Weathering processes are responsible for slight surface mineralogical differences allowing the distinction between lithologically similar geological units using Thematic Mapper (TM) data. Two different stages throughout time of overlying iron alteration are notoriously distinctive on the imagery and laboratory spectra. Their diverse spectral behaviour follows the dominant iron hydroxide with kaolinite and carbonate crusts on the Pliocene Ochre Alteration typical of a humid warm climate, compared with the dominant nonhydratated iron oxides with smectite on the Miocene Red Alteration developed under a mediterranean dry climate. Iron materials with carbonate hinder appearance of the typical iron absorption features in the visible wavebands. Therefore, the iron weathering alteration coatings will be obscured on the imagery when it is developed on carbonate sediments or detritic sediments with carbonate cement or matrix. The presence of carbonate within the sediment as cement or alteration product decreases the overall reflectance of laboratory nonconsolidated rocks and the clay size fraction from rocks, apart from smoothing the 2200 nm absorption typical of OH-bearing minerals. The presence of carbonate cement and carbonate crusts favours the differentiation of some units. Digital mapping through image processing of different series of digital data leads to a sequential masking of classes to produce a final map. The sequence of masking produces different maps which can be used as a tool to model aspects of the sedimentary basin and geological processes throughout time.

Long-term effects of aquifer overdraft and recovery on groundwater quality in a Ramsar wetland: Las Tablas de Daimiel National Park, Spain

Las Tablas de Daimiel National Park is one of Spains most representative groundwater‐dependent ecosystems. Under natural conditions, water inflows combined brackish surface water from River Giguela with freshwater inputs from River Guadiana and the underlying aquifer. Since the mid‐1970s, aquifer overexploitation caused the desiccation of the wetlands and neighbouring springs. The National Park remained in precarious hydrological conditions for three decades, with the only exception of rapid floods due to extreme rainfall events and sporadic water transfers from other basins. In the late 2000s, a decrease in groundwater abstraction and an extraordinarily wet period reversed the trend. The aquifer experienced an unexpected recovery of groundwater levels (over 20 m in some areas), thus restoring groundwater discharge to springs and wetlands. The complex historical evolution of the water balance in this site has resulted in substantial changes in surface and groundwater quality. This becomes evident when comparing the pre‐1980 groundwater quality and the hydrochemical status in the wetland in two different periods, under “dry” and “wet” conditions. Although the system is close to full recovery from the groundwater‐level viewpoint, bouncing back in the major hydrochemical constituents has not yet been obtained. These still appear to evolve in response to the previous overexploitation state. Moreover, in some sectors, there are groundwater‐dependent ecosystems that remain different to those found in preoverexploitation times. The experience of Las Tablas de Damiel provides an observatory of long‐term changes in wetland water quality, demonstrating that the effects of aquifer overexploitation on aquatic ecosystems are more than a mere alteration of the water balance and that groundwater quality is the key to aquifer and aquatic ecosystem sustainability.

Late Quaternary stratigraphy of the La Janda Basin (SW Spain) - first results and palaeoenvironmental significance

The La Janda basin in southern Spain is a near-shore geo-bio-archive comprising a variable Quaternary depositional history, with shallow marine, lacustrine, palustrine, and terrestrial strata. In the 1930s the lake was drained and is serving now as a huge agricultural area. The 33 m-core recovered in fall 2016 along with several shallower drill cores up to c. 15 m, reveals insights into a unique mixed terrestrial palaeo-environmental archive in Andalucia influenced by the Atlantic Ocean and hence the North Atlantic Oscillation (NAO) within the Gulf of Cadiz. The basins evolution was influenced both by the postglacial marine transgression and by an active tectonic fault controlling most of the accommodation space by causing subsidence. Our long core was accompanied by further corings along an E-W striking transect in order to reveal also the relation of the influence of tectonic activity with sedimentary sequences. Multi-Sensor Core Logging has been completed. Results of sedimentological, geochemical and micropalaeontological analyses will be presented in the frame of the climate variations during the Late Pleistocene and the Holocene, along with a preliminary age-depth model based on radiocarbon (AMS-14C) and optical stimulated luminescence (OSL) dating techniques. Our investigations ultimately aim at providing valuable information on major Late Pleistocene to Holocene climatic and palaeo-environmental fluctuations in the southernmost part of the Iberian Peninsula.