The Sorbas Basin

Geological Features desplegable INGLES OK copia.qxp 27/5/08 01:43 Página 1

Geological Features and Evolution Geological Features and Evolution

STRATIGRAPHY OF THE SORBAS BASIN GEOLOGICAL MAP OF THE SORBAS BASIN GEOLOGICAL CONTEXT OF THE SORBAS BASIN PALAEOGEOGRAPHICAL EVOLUTION OF THE SORBAS BASIN FROM THE UPPER TORTONIAN (8 Ma) TO THE LOWER PLIOCENE (4 Ma)

50 m Uleila A. UPPER TORTONIAN (around 8 Ma) B. END TORTONIAN-LOWER MESSINIAN (around 7 Ma) C. LOWER MESSINIAN (around 6 Ma)

Graphic Scalebar Vera Millions of years SIERRA DE LOS FILABRES Sorbas Emerged land 10 Conglomerates and sands 5 Km Uleila Uleila CABRERA Uleila Bédar Mojácar FILABRES BÉDAR QUATERNARY ALHAMILLA FILABRES Mojácar Carboneras Shallow platform Palaeocoastline 1.8 9 Bioclastic sands Níjar Sorbas Coral reef SIERRA DE GÁDOR Sorbas Open Sorbas sea Deltas Open 5.3 Tabernas Present Sorbas Submarine fan Lucainena sea 8 Conglomerates, sands and muds Almería Turrillas Lucainena Platform coastline Turrillas Present coastline PLIOCENE Turrillas Lucainena Carboneras Shallow sea Submarine fan Submarine high ALHAMILA Carboneras 7a 7a Conglomerates, oolites, patch reefs Cabo de Gata ALHAMILA (reefal lagoon) 7b and stromatolites Lucainena 7b Sands and muds Neogene sediments 6 Gypsum Neogene volcanic rocks Turrillas Position of geological section 5 Km Modified from Montenat, 1990 Betic Substratum MESSINIAN 5 Marls 5.9 D. UPPER MESSINIAN E. UPPER MESSINIAN (around 5.4 Ma) F. PLIOCENO INFERIOR (around 4 Ma) 6.2 GEOLOGICAL SECTION (evaporitic unit, around 5.5 Ma) 4b 4b Fringing reefs 4a 4a Calcarenites NW SE Abanicos deltaicos Uleila 7.1 Gypsum karst Uleila Sea Zone 3 Bioclastic limestones Sierra de los Filabres Sierra Alhamilla Uleila Open FILABRES FILABRES Bédar sea Palaeocoastline Palaeocoastline Mojácar Río Aguas FILABRES Mojácar Beach/ Barrier island Mojácar 2b 2b Reefal limestones Barrier Semi-arid basin Enclosed CABRERA TORTONIAN 2c 2c Marls, sands and conglomerates lagoon Sorbas CABRERA Present CABRERA Sorbas Sorbas coastline Lucainena 2a Conglomerates and red sands Lucainena Present Lucainena Present Turrillas ALHAMILA ALHAMILA coastline coastline ALHAMILA Carboneras Carboneras Turrillas Carboneras 1 Betic Substratum. Metamorphic rocks: phyllites, schists, quartzites, marbles, etc...

PRE-MIOCENE 5 Km

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THE SORBAS KARST. Origin of the Sorbas gypsum Geological Features and Evolution

Juan C. Braga - José M. Martín Juan C. Braga - José M. Martín

Around 5.5 million years ago (in the Messinian) AEREAL DISTRIBUTION The Sorbas Basin constitutes an intermontane At the end of the Miocene (around 5,5 million the coastline progressively retreated until the Mediterranean dried up through closure of 200 Km Salt OF MESSINIAN basin of singular geological interest for the years ago, during the Messinian) an enhanced reaching its present position. SALT DEPOSITS IN 44º N its communication with the Atlantic Ocean due THE MEDITERRANEAN study and understanding of palaeogeographical process of desiccation of the Mediterranean Sea to tectonic uplift, and masses of evaporites SEA and palaeoenvironmental changes occurring on caused the marine Sorbas Basin to become The final retreat of the sea meant that the (gypsum and salt) were deposited in its central the Mediterranean coast during the last practically dry, with a very shallow depth marine sediments became exposed to Spain and deepest region.The thickness of 8 million years, and its relationship to the subjected to strong evaporation. In these the action of erosive agents.The removal of the accumulated salt (mainly sodium chloride) Sorbas geological evolution of the Betic Cordillera. circumstances a package of gypsum almost 100 upper sedimentary layers left the highly soluble exceed 1500 m in some places. In relation to this metres in thickness was deposited: the Sorbas gypsum subjected to the continuous action of Alborán phenomenon, important deposits of gypsum Gibraltar Eight million years ago (in the Upper Miocene), gypsum. Afterwards, the sea reoccupied its water, which progressively dissolved it. (hydrated calcium sulphate) were also the configuration of land emerged and level, continuing the accumulation of marls and Therefore, one of the most important gypsum deposited in the Sorbas Basin, which locally Morocco submerged beneath the sea along the coastal detrital sediments above the gypsum, up until, karst landscapes in the world for its size, worth 32º exceed 130 m in thickness and that outcrop 8º 0º 8º 16º zone of Almería was similar to present, but not around 3.5 million years ago (in the Pliocene), and beauty started to form.

over an area of nearly 25 square kilometres. Rouchy, from Taken 1980 identical: the sea spread across the Sorbas Basin, dry land today, up to the foothills of the Sierra

de los Filabres, in whose margin reefs of fossil DISTRIBUTION OF EMERGED LAND AND SEA 6 MILLION YEARS AGO corals from this age remain as testament, closely SEDIMENTARY INTERPRETATION FOR THE SORBAS GYPSUM IN A MEDITERRANEAN CONTEXT marking the position of the ancient coastline. On the slopes, submarine fans deposited thick Guadalquivir Sorbas Sorbas Basin Mediterranean Atlantic and extensive sediments that the rivers stripped Basin out from the emergent relief.The later Almería Fringing reef A (5.9 Ma bp) B C (5.5 Ma bp) emergence of Sierra Alhamilla and Sierra Atlantic Ocean Mediterranean Sea Evaporation Semi-confined Sorbas Basin Cabrera configured a long and narrow Erosion Desiccation Uleila FILABRES intermontane marine basin between these new Normal salinity relieves, to the south, and Los Filabres, towards Mojácar Gypsum the north, where the deposition of marine Sorbas Mediterranean Sea Gypsum and other salts sediments continued: this is today called the Present Turrillas Sorbas Basin. Coastline Situation prior to the deposition of evaporites, Evaporite deposits in the centre of the Mediterranean Evaporite deposits in the interior of the Sorbas Basin. Lucainena with the formation of reefs along the margins and result from this disconnection with the Atlantic, and drying Carboneras ALHAMILLA marly-muddy sediments in the basin. out.

102 99 Geological Features and Evolution

Juan C. Braga - José M. Martín

The Sorbas Basin constitutes an intermontane At the end of the Miocene (around 5,5 million the coastline progressively retreated until basin of singular geological interest for the years ago, during the Messinian) an enhanced reaching its present position. study and understanding of palaeogeographical process of desiccation of the Mediterranean Sea and palaeoenvironmental changes occurring on caused the marine Sorbas Basin to become The final retreat of the sea meant that the the Mediterranean coast during the last practically dry, with a very shallow depth marine sediments became exposed to 8 million years, and its relationship to the subjected to strong evaporation. In these the action of erosive agents.The removal of the geological evolution of the Betic Cordillera. circumstances a package of gypsum almost 100 upper sedimentary layers left the highly soluble metres in thickness was deposited: the Sorbas gypsum subjected to the continuous action of Eight million years ago (in the Upper Miocene), gypsum. Afterwards, the sea reoccupied its water, which progressively dissolved it. the configuration of land emerged and level, continuing the accumulation of marls and Therefore, one of the most important gypsum submerged beneath the sea along the coastal detrital sediments above the gypsum, up until, karst landscapes in the world for its size, worth zone of Almería was similar to present, but not around 3.5 million years ago (in the Pliocene), and beauty started to form. identical: the sea spread across the Sorbas Basin, dry land today, up to the foothills of the Sierra de los Filabres, in whose margin reefs of fossil DISTRIBUTION OF EMERGED LAND AND SEA 6 MILLION YEARS AGO corals from this age remain as testament, closely marking the position of the ancient coastline. On the slopes, submarine fans deposited thick and extensive sediments that the rivers stripped Guadalquivir Sorbas Basin out from the emergent relief.The later Almería emergence of Sierra Alhamilla and Sierra Atlantic Ocean Mediterranean Sea Cabrera configured a long and narrow Uleila FILABRES intermontane marine basin between these new relieves, to the south, and Los Filabres, towards Mojácar the north, where the deposition of marine Sorbas Mediterranean Sea sediments continued: this is today called the Present Turrillas Sorbas Basin. Coastline Lucainena Carboneras ALHAMILLA

99 STRATIGRAPHY OF THE SORBAS BASIN

50 m

Millions of years 10 Conglomerates and sands QUATERNARY 1.8 9 Bioclastic sands

5.3 8 Conglomerates, sands and muds PLIOCENE

7a 7a Conglomerates, oolites, patch reefs 7b and stromatolites 7b Sands and muds 6 Gypsum

5.9 MESSINIAN 5 Marls 6.2 4b 4b Fringing reefs 4a 4a Calcarenites

7.1 3 Bioclastic limestones

2b 2b Reefal limestones

TORTONIAN 2c 2c Marls, sands and conglomerates

2a Conglomerates and red sands

1 Betic Substratum. Metamorphic rocks: phyllites, schists, quartzites, marbles, etc... PRE-MIOCENE Geological Features and Evolution

GEOLOGICAL MAP OF THE SORBAS BASIN GEOLOGICAL CONTEXT OF THE SORBAS BASIN

Uleila

Graphic Scalebar Vera

SIERRA DE LOS FILABRES Sorbas CABRERA

ALHAMILLA Carboneras Níjar SIERRA DE GÁDOR Sorbas Almería

Cabo de Gata Lucainena Neogene sediments

Neogene volcanic rocks Turrillas Position of geological section 5 Km Modified from Montenat, 1990 Betic Substratum

GEOLOGICAL SECTION

NW SE Gypsum karst Sierra de los Filabres Sierra Alhamilla

Río Aguas

5 Km Geological Features and Evolution

PALAEOGEOGRAPHICAL EVOLUTION OF THE SORBAS BASIN FROM THE UPPER TORTONIAN (8 Ma) TO THE LOWER PLIOCENE (4 Ma)

A. UPPER TORTONIAN (around 8 Ma) B. END TORTONIAN-LOWER MESSINIAN (around 7 Ma) C. LOWER MESSINIAN (around 6 Ma)

Emerged land Uleila 5 Km Uleila Uleila Bédar BÉDAR FILABRES Mojácar FILABRES Mojácar Shallow platform Sorbas Palaeocoastline Sorbas Open Coral reef Tabernas sea Present Deltas Sorbas Open Submarine fan sea Turrillas Lucainena Lucainena Platform coastline Turrillas Present coastline Turrillas Lucainena Submarine fan Carboneras Shallow sea Submarine high ALHAMILA ALHAMILA (reefal lagoon) Carboneras

D. UPPER MESSINIAN E. UPPER MESSINIAN (around 5.4 Ma) F. PLIOCENO INFERIOR (around 4 Ma) (evaporitic unit, around 5.5 Ma)

Abanicos deltaicos Uleila Uleila Sea Zone Uleila Open FILABRES FILABRES Bédar sea Palaeocoastline Palaeocoastline Mojácar FILABRES Mojácar Beach/ Barrier island Mojácar Barrier Semi-arid basin Enclosed CABRERA lagoon Sorbas CABRERA Present CABRERA Sorbas Sorbas coastline Lucainena Lucainena Present Lucainena Present Turrillas ALHAMILA ALHAMILA coastline coastline ALHAMILA Carboneras Carboneras Turrillas Carboneras

101 THE SORBAS KARST. Origin of the Sorbas gypsum

Juan C. Braga - José M. Martín

Around 5.5 million years ago (in the Messinian) AEREAL DISTRIBUTION the Mediterranean dried up through closure of 200 Km Salt OF MESSINIAN SALT DEPOSITS IN 44º N its communication with the Atlantic Ocean due THE MEDITERRANEAN to tectonic uplift, and masses of evaporites SEA (gypsum and salt) were deposited in its central Spain and deepest region.The thickness of accumulated salt (mainly sodium chloride) Sorbas exceed 1500 m in some places. In relation to this Alborán phenomenon, important deposits of gypsum Gibraltar (hydrated calcium sulphate) were also deposited in the Sorbas Basin, which locally Morocco 32º exceed 130 m in thickness and that outcrop 8º 0º 8º 16º

over an area of nearly 25 square kilometres. Rouchy, from Taken 1980

SEDIMENTARY INTERPRETATION FOR THE SORBAS GYPSUM IN A MEDITERRANEAN CONTEXT

Sorbas Basin Mediterranean Atlantic

Fringing reef A (5.9 Ma bp) B C (5.5 Ma bp) Evaporation Semi-confined Sorbas Basin Erosion Desiccation Normal salinity

Gypsum Gypsum and other salts

Situation prior to the deposition of evaporites, Evaporite deposits in the centre of the Mediterranean Evaporite deposits in the interior of the Sorbas Basin. with the formation of reefs along the margins and result from this disconnection with the Atlantic, and drying marly-muddy sediments in the basin. out.

102 Origin of the Sorbas gypsum

The gypsum deposits in the Sorbas Basin PALAEOGEOGRAPHY OF THE SORBAS BASIN DURING GYPSUM DEPOSITION (5.5 Ma bp) were not, however, strictly contemporaneous with the deposition of evaporites in the centre of the Mediterranean, but somewhat later. Open sea Uleila This deposition took place during the BÉDAR reflooding phase of the Mediterranean, FILABRES Mojácar upon refilling with new water, presumably BARRIER coming from the Atlantic and invading a PALAEOCOASTLINE SEMI-RESTRICTED LAGOON CABRERA broad semi-restricted depression, that at Sorbas the time occupied a large part of what Lucainena today constitutes the Sorbas Basin. ALHAMILLA Present coastline Carboneras The Sorbas gypsum was deposited in an evaporitic basin, of restricted character, closed towards the west and separated from the open sea by a submarine barrier Semi-restricted basin located at its most easterly end, created through uplift of the Sierra Cabrera. Evaporation

Basement Gypsum precipitation Open sea Barrier

103 Origin of the Sorbas gypsum

In detail, the evaporite sequence of STRATIGRAPHICAL COLUMN OF THE SORBAS EVAPORITE Sorbas consists of banks of gypsum, SEQUENCE AND DETAILED STRUCTURE OF THE GYPSUM BANKS WITHIN THE SUCCESSION of up to 20 m thickness, separated by

marly-limestone intervals and/or Taken from Dronkert, 1976 carbonates.The thickness of the gypsum Mts. banks diminishes towards the top at the same time as that of the non-evaporitic 120 intervals increases.The latter, at least in 110 the higher part, possess a marine Field view of the gypsum banks. character, in that they incorporate the remains of the calcareous skeletons 100 of marine organisms and record the Supercones 90 Supercone different episodes of basin inundation.

80 In the highest banks of gypsum in the sequence a very spectacular growth Palisades 70 structure of arborescent character evidently forms, known as supercones 60 (also called cauliflowers), that are Detailed field view of the gypsum supercones. interpreted as resulting from 50 competition between the growth Nucleation Cones of gypsum and the deposition of 40 contemporaneous muddy sediments. according to Dronkert, 1977. 30

Gypsum 20

Marly limestones and/or muds 10 Field photograph of the gypsum banks from the upper Carbonates part of the evaporite sequence.

104 Karst: the slow dissolution of the rocks

M. Villalobos

Rainwater and groundwater are capable FEATURES IN KARST LANDSCAPE of dissolving soluble rocks in a slow 22. Column process that takes thousands of years. 1. Tepuys (Karst en cuarcitas) 15. Bedding Plane 23. Resurgence 2. Pitons, Stacks ,Towers (tropical karst) 16. Pipe 24. Dry valley The resultant landscape, known as karst 3. Lapiés/Karren (high mountain karst) 17. Sump 25. Trop Plein 4. Dissolution Dolina 18. Debris cone or karstic landscape, is very peculiar. 26. Cave 5. Uvala 19. Gours 27. Canyon A It is characterised by the presence of 6. Polje 20. Fossil Gallery 7. Ponor 21. Lake abundant closed depressions at the 8. Collapse dolinas 9. Rock bridge surface (dolinas, potholes, etc.) and 10. Joint a complex subterranean drainage system 11. Sinkhole 12. Pothole (cavities). 13. Chimney B 14. Cascade

Karstification of gypsum is an infrequent phenomenon in nature.The greater part C of known karst are limestones.The Sorbas karst is the most important gypsum karst in Spain, and one of the four best known examples in Europe. Additionally, it has ra. a very high scientific and didactic value in au J. L. S a world context. m n fro Take

A B C

Zone of recharge (photo J. M. Calaforra). Zone of transfer (photo J. M. Calaforra). Flooded Zone (photo J. M. Calaforra).

105 How is the gypsum karst of Sorbas formed?

J. M. Calaforra

1.THE DRAINAGE NETWORK IS ESTABLISHED 1.The gypsum is originally covered by Sierra de los Filabres Sierra de los Filabres other sediments, on top of which the incipient drainage network starts to Sorbas Basin

install itself. Faults

2.THE SURFICIAL DISSOLUTION OF GYPSUM STARTS

2.The drainage network erodes the Sierra de los Filabres Sierra de los Filabres upper sediments until exposing the gypsum in very localised places Sorbas Basin where the first dolinas originally start to be dissolved.

3. SUBTERRANEAN DRAINAGE IS INITIATED

Sierra de los Filabres 3.The gypsum is becoming exposed to Sierra de losFilabres a greater extent at the surface through time. A multitude of dolinas develop that Sorbas Basin favour the entrance of water into the interior.

4. KARST DEVELOPS

Sierra de los Filabres Sierra de los Filabres 4.The general entrance of water into the gypsum mass promotes its slow Sorbas Basin dissolution, creating a complex subterranean network of galleries.

Sediments beneath the gypsum Gypsum Sediments above the gypsum 106 Landscape and surface features

M. Villalobos

A multitude of small depressions pepper the surface of the An escarpment cliff delimits the karst.These are the dolinas.They result from the dissolution or entire southern margin of the collapse of the surface layers of the gypsum. gypsum outcrop.

The extensive plain, the escarpment cliff and the valley are the most characteristic elements of the surface landscape.

Above the gypsum rock an extensive karstic plain is fashioned.

Large gypsum blocks tumble down from the cliff covering the marl slope.These are The Río Aguas cuts down towards the south into soft called block falls. marly sediments giving rise to a broad valley.

107 Dissolution features: chambers and galleries

J. M. Calaforra - M. Villalobos

1 2 3

Rainwater penetrates into the rock interior, starting to dissolve Dissolution progressively enlarges the initial channel. The water penetrates through to the lower layers.The initial the gypsum. crystallization features start to form.

(Photo J. Les)

The water infiltrates, slowly dissolving gypsum rock, generating a complex network of subterranean galleries. Chambers are formed from galleries through the dissolution of the walls, and by the fall of blocks from the walls and roof.

1 2 3

108 Dissolution features: chambers and galleries

Slowly meanders are excavated, on occasions they are very long.

Only the lower section is permanently flooded.

4 5

109 Crystallization features: speleothems

J. M. Calaforra - M. Villalobos

1 2 3

Water circulates through the incipient galleries and chambers, Gypsum is saturated in this slow process so that it then The roof, walls and floors of chambers and galleries are infiltrating and dissolving the gypsum rock. precipitates in the form of small crystals. coated with a multitude of gypsum crystals in fanciful designs and colours.

Water infiltrates dissolving the gypsum, is saturated and crystallizes in extremely delicate forms.These are the speleothems.

It has taken hundreds of thousands of years, millions at Stalagmites. Columns. Mamelones. Rings. times, in order for nature to sculpt them. Respect them, never touch them, and be careful not to damage them by accident.They have an incalculable value, but only here where they were born, they have no value elsewhere. Stalagmite mounds. Curtains. Corals. Balls.

110