Karstic Lakes in the Iberian Range: Late Holocene sedimentological evolution and environmental and climatic implications Fernando Barreiro-Lostres * Ana Moreno Santiago Giralt Pilar Mata Blas Valero-Garcés Instituto Pirenaico de Ecología (IPE)-CSIC
Introduction On the Iberian Range Large carbonate areas afected by endo- and exokarstic processes with … circular funnel-shaped depressions … travertine –damned lakes If this depressions intercept the regional aquifer, relative deep lakes occur. Instituto Pirenaico de Ecología (IPE) CSIC
Introduction KARST Instituto Pirenaico de LAKE Ecología (IPE) CSIC IMPERMEABLE SEDIMENTS
Introduction These systems are very sensitive to regional hydrological balances. In response to climatic changes, they present large variations on water properties (water table levels, chemistry, biota, etc.) So, climatic, environmental changes and the possible human impact are recorded in the sediments Instituto Pirenaico de Ecología (IPE) CSIC
Lacustrine sediments → Excepcional records Introduction of the environmental evolution of an area. We can study: - Clastic input: Human impact in the watershed during the last millennia has provoked an increase in sediment delivery to many lakes in Spain... but Increase run-off cause by climate factors can also be identified as short-term flooding events. - Evolution of redox stages at the lake bottom: Fe/Mn, Fe/S and Fe/Ti ratios can be used to unravel the evolution of the pH/Eh conditions during the Instituto Pirenaico de Ecología (IPE) CSIC sedimentation and early diagenesis stages. - Endogenic calcite formation: preservation of calcite varve in discrete intervals
We present here the sedimentary sequence of 3 karstic lakes Introduction Location and Geological settings 1) Taravilla 3) El Tobar 2) La Parra Instituto Pirenaico de Ecología (IPE) CSIC
Taravilla lake Upper Tagus River Valley (Guadalajara) Introduction Location and Geological settings Taravilla 1) Taravilla Instituto Pirenaico de Ecología (IPE) CSIC
Taravilla lake Introduction Geology Inlet Location and dominated by Geological Jurassic and settings Cretaceous Taravilla Limestones 1100 m asl. Outlet 2 ha surface area 11m max depth Inlets: 1 permanent spring at E. Outlets: 1 at SE (non functional on dry Instituto Pirenaico de Ecología (IPE) CSIC periods). Associated with tufa growths Water: freshwater, similar to River Tagus Mediterranean climate with strong continental influence (700 mm av rainfall)
Taravilla lake Composite sequence Introduction from 2 cores retrieved Location and in 2004 (Kullemberg Geological piston) – Last 1700 yr settings Taravilla - Sediment record is composed of dm-bedded, massive to faintly laminated, brownish-gray, carbonte sediments with variable amounts of Organic remains and several intercalated sandy layers. - 5 main sedimentary facies were Instituto Pirenaico de identified. Ecología (IPE) CSIC
Taravilla lake Introduction Facies Description Depositional environment Location and Geological 1: Massive, dark Cm- to dm-thick beds, Intense flood deposits grey silty-sand to massive to faintly laminated; reaching the inner settings coarse sand abundant plant macrorest. areas of the lake. Taravilla 2: Massive to light grey carbonate silt Cm- to dm-thick layers, Deposition in the middle of massive, variable amount of the lake during open water carbonate and OM circulation periods 3: Massive to Cm to dm-thick layers, Deposition in the middle of faintly laminated, faintly laminated, relatively the lake during periods of dark grey higher organic matter and more restricted water carbonate silt and lower carbonate content. circulation. mud Relatively high magnetic susceptibility. 4: Gastropod and Cm- thick layers with Organic rich layers charophyte-rich abundant fossils and associated with flood coarse silt and calcified Chara remains. events mud Instituto Pirenaico de 5: Laminated light Cm-thick layers, laminated, Middle of the lake, low gray-yellowish silt dominant carbonate energy dominant oxic Ecología (IPE) CSIC composition. Relatively low bottom conditions magnetic susceptibility.
Taravilla lake Introduction Location and Geological settings Taravilla Flood facies (1-4) L Flood facies (1-4) L dominate dominate I I during LIA during LIA A A HIATUS HIATUS Instituto Pirenaico de Low energy-oxic Low energy-oxic Ecología (IPE) CSIC MP MP facies (5) facies (5) & RA & RA
Taravilla lake Introduction To underline: Location and Geological settings - Facies variability Taravilla - Several allochthonous terrigenous layers in the sediment sequence have been identified deposited during the LIA (wetter and colder period) Main sedimentary processes: Instituto Pirenaico de Ecología (IPE) CSIC Flood layers as consequence of period of intense precipitation (with minor local anthropogenic impacts -deforestation-).
La Parra lake Cañada del Hoyo doline complex (“Torcas” de Introduction Cuenca) Location and Geological settings Taravilla La Parra 2) La Parra Instituto Pirenaico de Ecología (IPE) CSIC
La Parra lake Introduction Geology Location and dominated by Geological Cretaceous settings Dolostones Taravilla 1000 m asl. La Parra 1 ha area 17 m depth Holomictic Inlets: Mainly groundwater and runoff water. Outlets: Irrigation wells Instituto Pirenaico de Ecología (IPE) CSIC Water: Magnesium - bicarbonated 500 mm av. precipitation
La Parra lake 11 sedimentary facies!! (3 main Units) from Introduction one core retrieved in 2010 (UWITEC platform) Location and – Last 1600 yr Geological settings A) Detritical B) Laminated Taravilla 1) Silts La Parra Facies A Facies B Facies C Facies D Facies E 2) Sands 3) Gravels Instituto Pirenaico de Ecología (IPE) CSIC Facies F Facies G Facies H Facies I Facies J
La Parra lake Unit III: 1 st lacustrine deposits → Increase Introduction of water table - Laminated Location and facies Geological changing to settings coarser silts: Taravilla - Fast water table levels La Parra changes; - Litoral and shallower environment deposit . Instituto Pirenaico de Ecología (IPE) CSIC
La Parra lake Unit II: High Ti content and fine facies: Introduction Increase of Location and fine Geological siliciclastic settings inputs Taravilla Implies: La Parra - Higher lake levels - Higher local anthrogenic impacts (erosion). Instituto Pirenaico de Ecología (IPE) CSIC
La Parra lake Bottom Unit I: Maintained decrease in Ti Introduction content + coarser facies: Deposited Location and during the Geological onset of the settings MWP (900 yr cal BP) Taravilla La Parra 1 1 Instituto Pirenaico de Ecología (IPE) CSIC
La Parra lake Medium Unit I: Fine and Laminated facies Introduction Higher lake Location and levels. Geological settings Laminated facies: as Taravilla trends to anoxia at lake bottom La Parra Corresponds 2 2 with the LIA (similar pattern than nearby La Cruz lake) Instituto Pirenaico de Ecología (IPE) CSIC
La Parra lake Top Unit I: Dominancy of fine massive silts Introduction Laminated Location and facies Geological disappear settings 3 3 Relative Taravilla drop of lake levels during La Parra recent times Instituto Pirenaico de Ecología (IPE) CSIC
La Parra lake To underline: Introduction Location and - Sedimentray record is mainly composed by Geological clastic carbonated deposits. settings Taravilla - High facies variability... - … controlled by changes in detritic inputs. La Parra Main sedimentological aspects: - Detritic inputs more intense than expected (possible anthropogenic impacts during MWP) - Laminated facies restricted to some periods Instituto Pirenaico de (wet and cold, favours meromixis, LIA) Ecología (IPE) CSIC As consequence of Large hydrological fluctuations during the last 1600 yr.
El Tobar Cuenca Mountains (Cuenca) Introduction Taravilla La Parra El Tobar 3) El Tobar Instituto Pirenaico de Ecología (IPE) CSIC
El Tobar Introduction Developed on carbonated and Location and Meromictic Geological evaporitic settings Triassic formations Taravilla Holomictic La Parra 1250 m asl. El Tobar 2 sub-basins: - Holomictic: shallower (12 m depth) - Meromictic: funnel-shaped (20 m) → Has a permanent saline anoxic monimolimnion below 12 m due to groundwater seepage. Instituto Pirenaico de Ecología (IPE) CSIC Inlets: Recent connection with nearby reservoir (“La Tosca”, S shore), saline groundwater (diffuse) and freshwater springs (NE shore). Outlets: 1 surface outlet on the W shore
El Tobar Introduction Location and - 6 long cores were recovered in both sub- Geological basins (Kullemberg corer). settings Taravilla - They consist of 3 main facies, giving a La Parra finely-laminated to banded aspect to the sediment: El Tobar 1- Cm-thick beds of massive dark carbonatic mud with diatoms. 2- Cm-thick beds of coarse grey carbonatic-silty mud with Qz. 3- Cm-thick beds of medium-fine brown carbonatic mud with Qz. Instituto Pirenaico de Ecología (IPE) CSIC
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