Karstic Lakes in the Iberian Range: Late Holocene ...digital.csic.es/bitstream/10261/102881/1/IAS_Karstic_Lakes_final.pdf · Facies Description Depositional environment 1: Massive,

Karstic Lakes in the Iberian Range: Late Holocene

sedimentological evolution and environmental and climatic

implications

Fernando Barreiro-Lostres *Ana MorenoSantiago GiraltPilar MataBlas Valero-Garcés

Instituto Pirenaico de Ecología (IPE)-CSIC

Instituto Pirenaico de Ecología (IPE) CSIC

Introduction

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.

On the Iberian Range


Introduction

KARST

IMPERMEABLELAKE

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


IntroductionLacustrine sediments → Excepcional records of the environmental evolution of an area. We can study:

- Clastic input: Human impact in the watershed during the last millenniahas provoked an increase in sediment delivery to many lakes in Spain... butIncrease run-off cause by climate factors can also be identified as short-termflooding events.- Evolution of redox stages at the lake bottom: Fe/Mn, Fe/S and Fe/Tiratios can be used to unravel the evolution of the pH/Eh conditions during thesedimentation and early diagenesis stages.- Endogenic calcite formation: preservation of calcite varve in discrete intervals


Introduction

We present here the sedimentary sequence of 3 karstic lakes

Location and Geological settings

1) Taravilla

3) El Tobar

2) La Parra


Introduction

Taravilla

1) Taravilla

Taravilla lakeUpper Tagus River Valley (Guadalajara)



Taravilla lake

Inlet

Outlet

Geology dominated by Jurassic and Cretaceous Limestones

1100 m asl.2 ha surface area11m max depth

Inlets: 1 permanent spring at E.Outlets: 1 at SE (non functional on dry periods). Associated with tufa growthsWater: freshwater, similar to River TagusMediterranean climate with strong continental influence (700 mm av rainfall)

Introduction

Taravilla



Taravilla lakeComposite sequence from 2 cores retrieved in 2004 (Kullemberg piston) – Last 1700 yr

- 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 identified.

Introduction

Taravilla



Taravilla lakeFacies Description Depositional environment

1: Massive, dark grey silty-sand to coarse sand

Cm- to dm-thick beds, massive to faintly laminated; abundant plant macrorest.

Intense flood deposits reaching the innerareas of the lake.

2: Massive to light grey carbonate silt

Cm- to dm-thick layers, massive, variable amount of carbonate and OM

Deposition in the middle of the lake during open water circulation periods

3: Massive to faintly laminated, dark grey carbonate silt and mud

Cm to dm-thick layers, faintly laminated, relatively higher organic matter and lower carbonate content. Relatively high magnetic susceptibility.

Deposition in the middle of the lake during periods of more restricted water circulation.

4: Gastropod and charophyte-rich coarse silt and mud

Cm- thick layers with abundant fossils and calcified Chara remains.

Organic rich layers associated with flood events

5: Laminated light gray-yellowish silt

Cm-thick layers, laminated, dominant carbonate composition. Relatively low magnetic susceptibility.

Middle of the lake, low energy dominant oxic bottom conditions

Introduction

Taravilla



Taravilla lakeIntroduction

Taravilla


Flood facies (1-4) Flood facies (1-4) dominatedominateduring LIAduring LIA

Low energy-oxic Low energy-oxic facies (5)facies (5)

LLIIAA

MP MP & RA& RA

HIATUSHIATUS


Taravilla lake

To underline:

- Facies variability

- Several allochthonous terrigenous layers in the sediment sequence have been identified deposited during the LIA (wetter and colder period)

Main sedimentary processes:

Flood layers as consequence of period of intense precipitation (with minor local anthropogenic impacts -deforestation-).

Introduction

Taravilla



2) La Parra

La Parra lakeCañada del Hoyo doline complex (“Torcas” de Cuenca)

Introduction

Taravilla


La Parra


Geology dominated by Cretaceous Dolostones

1000 m asl.1 ha area17 m depthHolomictic

Inlets: Mainly groundwater and runoff water.Outlets: Irrigation wellsWater: Magnesium - bicarbonated 500 mm av. precipitation

La Parra lakeIntroduction

Taravilla


La Parra


La Parra lake11 sedimentary facies!! (3 main Units) from one core retrieved in 2010 (UWITEC platform) – Last 1600 yr

A) Detritical

Facies A Facies B Facies C

Facies F

Facies D Facies E

Facies G Facies H Facies I Facies J

1) Silts

2) Sands 3) Gravels

B) Laminated

Introduction

Taravilla


La Parra


Unit III: 1st lacustrine deposits → Increase of water table

- Laminated facies changing to coarser silts:

- Fast water table levels changes;

- Litoral and shallower environment deposit .


Taravilla


La Parra


Unit II: High Ti content and fine facies:

Increase of fine siliciclastic inputs

Implies:

- Higher lake levels- Higher local anthrogenic impacts (erosion).


Taravilla


La Parra


Bottom Unit I: Maintained decrease in Ti content + coarser facies:

Deposited during the onset of the MWP (900 yr cal BP)

11


Taravilla


La Parra


Medium Unit I: Fine and Laminated facies Higher lake levels.

Laminated facies: as trends to anoxia at lake bottom

Corresponds with the LIA

(similar pattern than nearby La Cruz lake)

22


Taravilla


La Parra


Top Unit I: Dominancy of fine massive silts

Laminated facies disappear

Relative drop of lake levels during recent times

33


Taravilla


La Parra


To underline:

- Sedimentray record is mainly composed by clastic carbonated deposits.

- High facies variability...- … controlled by changes in detritic inputs.

Main sedimentological aspects:

- Detritic inputs more intense than expected (possible anthropogenic impacts during MWP)- Laminated facies restricted to some periods (wet and cold, favours meromixis, LIA)

Large hydrological fluctuations during the last 1600 yr.


Taravilla


La Parra

As consequence of


3) El Tobar

El Tobar Cuenca Mountains (Cuenca)Introduction

La Parra

Taravilla

El Tobar


Developed on carbonated and evaporitic Triassic formations

1250 m asl.

2 sub-basins:

El Tobar

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

Holomictic

- Holomictic: shallower (12 m depth)- Meromictic: funnel-shaped (20 m) → Has a permanent saline anoxic monimolimnion below 12 m due to groundwater seepage.

Introduction

Taravilla


La Parra

El Tobar

Meromictic


El Tobar

- 6 long cores were recovered in both sub-basins (Kullemberg corer).

- They consist of 3 main facies, giving a finely-laminated to banded aspect to the sediment:

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.

Introduction

Taravilla


La Parra

El Tobar


El TobarIntroduction

Taravilla


La Parra

El Tobar

- Several short cores (gravity corer) were also recovered in both sub-basins.

- Dating is in progress, but 137Cs suggest high sedimentation rates (1cm/yr)

- This yellow clay can serve as chronological marker, as we consider it was deposited immediately after the opening of the connection between La Tosca reservoir and the lake (mid 1960).


El TobarIntroduction

Taravilla


La Parra

El Tobar

To underline:

The work is preliminary yet, but: - Sedimentray record is mainly composed by 3 facies of carbonatic mud (with 2 crystal sizes) with Qz, finely laminated in the mayor part of the core.

Main sedimentological aspects:

- Lake combines mero and holomixis (carbonates precipitation as laminaes) in a small karstic basin with a strong human impact since 1960.- La Tosca channel modified the hydrology, opening it to new sediment imputs (new fine detritic layers -yellow clays- and eutrophism).


El Tejo karstic lakeIntroduction

Taravilla


La Parra

El Tobar

- Deeper than La Parra lake (28 m depth), trends to development of meromixis.- Presents laminated sediments, probably varves in origin, but bad preserved in time.- High detritic influence on first 60 cm and some other detritic episodes intercalated at depth between lamination.

New Horizonts

Belongs to the Doline Cuenca complex (“Torcas”), as La Parra lake.

Geology dominated by Cretaceous Dolostones


1. Why each sedimentary sequence is so different?Introduction

Taravilla


La Parra

El Tobar

- Karstic lake origin on this area is similar- Climatic context is similar

So?

a) A high unexpected detrital influence has affected all lakes.

b) Depth of lakes: Laminated facies only in deeper lakes (El Tobar, El Tejo, La Cruz).

c) Calcite varve preservation is limited in time (El Tobar, El Tejo, La Cruz).

d) Differential local human impact (grazing, fires, irrigation).

New Horizonts

General Conclusions


2. Depositional EvolutionIntroduction

Taravilla


La Parra

El Tobar

a) Higher run off and sediment delivery during the LIA (Taravilla, La Parra, also in La Cruz)

b) Lower lake levels during the MWP (La Parra, not so clear on Taravilla)

c) The “Torcas” (Cuenca doline complex) were dry prior to 1600 yr

New Horizonts

General Conclusions


That's All!Introduction

Taravilla


La Parra

El Tobar

Thanks for your attention

New Horizonts

General Conclusions

The study is funded by GLOBALKARST and GRACCIE

CONSOLIDER-INGENIO projects (Spanish Government)

Core Platform at El Tejo lake.Sometimes, logistics are not so easy!


ReferencesIntroduction

Taravilla


La Parra

El Tobar

1. Barreiro-Lostres et al, “Facies sedimentarias de la laguna kárstica de La Parra (Cuenca) durante los últimos 1600 años”. Geogaceta, in press.

2. Moreno et al., “Flood response to rainfall variability during the last 2000 years inferred from the Taravilla Lake record (Central Iberian Range, Spain),” Journal of Paleolimnology 40, no. 3 (April 2008): 943-961.

3. García-Gil et al., “Vertical distribution of photosynthetic sulphur bacteria linked to saline gradients in Lake El Tobar (Cuenca,Spain),” Aquatic Microbial Ecology 20 (1999): 299-303.

4. Valero Garces et al., “The Taravilla lake and tufa deposits (Central Iberian Range, Spain) as palaeohydrological and palaeoclimatic indicators,” Palaeogeography, Palaeoclimatology, Palaeoecology 259, no. 2-3 (2008): 136–156.

5. Valero Garcés et al., “Una visión paleolimnológica de tres lagos kársticos (Zoñar, Estanya y Taravilla): evolución sedimentaria y paleohidrológica, clima e impacto humano e implicaciones para la gestión y conservación,” Boletín Geológico y Minero 120, no. 3 (2009): 479-496.

6. Romero-Viana et al., “Climate Signal in Varve Thickness: Lake La Cruz (spain), a Case Study,” Journal of Paleolimnology 40, no. 2 (February 2008): 703-714.

7. Romero-Viana et al., “Meromixis origin and recent trophic evolution in the Spanish mountain lake La Cruz,” AQUATIC SCIENCES 60, no. 4 (1998): 279-299.

8. Romero-Viana et al., “Climate Signal in Varve Thickness: Lake La Cruz (spain), a Case Study,” Journal of Paleolimnology 40, no. 2 (February 2008): 703-714.

New Horizonts

General Conclusions

Documents

Karstic Lakes in the Iberian Range: Late Holocene ...digital.csic.es/bitstream/10261/102881/1/IAS_Karstic_Lakes_final.pdf · Facies Description Depositional environment 1: Massive,