Geology in Cabo de Gata-Níjar
The Cabo de Gata Nijar Geopark is a part of a complex orogenic system called the Betic-Rif Orogen, tha includes all the processes related to the to the western Mediterranean and the convergence between the African and Eurasian plates. It could be defined by its two branches, the north branch and the southern branch which correspond to the Betic and the Rif mountain belts. The orogen displays an arc shape open to the east. The igneous rocks that conforms the Cabo de Gata volcanic complex (among other areas) are subduction products and related to the extensional tectonics that take place during the Neogene in the area. A fragment of the subducted slab generates a westwards and eastwards rollback generating crustal thinning, formation of oceanic crust andformtaion of intramotane basins in the internatl areas of the Betic-Rif system. Since the Miocene, the extension ceased and the deformation in the area was controlled by the movement of the african and eurasian plate convergence (strike-slip faults like the Carboneras fault).
The geochemistry of the volcanic rocks lie in the calk-alkaline range, that is exactly what we could expecto from a back-arc basin (like the Alboran Basin). The CGVC is just a portion if this volcanic arc and the basin is controlled by the movement of the Carboneras fault, which diives the basin in two. The Carbnoneras fault is still active nowadays.
Due to the semiarid climate, the exposures are continuous all along the shoreline, but the volcanic edifices are not very well preserved. In spite of all that, the marine cliffs give us a lot of information and make possible a reconstruction of almost all the stratigraohy. This information allows us to define the CGVC as a field of submarine volcanic domes complexes and seamounts.
The Cabo de Gata volcanic complex is the largest-sized element of all the volcanic manifestations in SE Spain. It continues to expand under the Alboran Sea, and has been brouhgt to its present position by the operation of the Caborneras Fault. The greater part of volcanism in the Alboran Basin is actually submerged adn the volcanic structures of Cabo de Gata indicates clear sings of having been generated under the sea too. Some of the oldest volcanic structures could have grown out of the sea enough to reach the surface, forming volcanic island fringed by marine sedimentary platforms.
The Age of the Cabo de Gata volcanic complex is known through the study of fossils present in sedimentary rocks associated with the volcanic elements and dating with isitopes in the volcanic rocks. Volcanic activity developed in a broad period that extends from around 14.15 to 7.5 million years ago. During this interval, the volcanic activity ocurred in various cycles. The better-known and conserved volcanic features are the most recent, produced between 9-7.5 million years ago.
The base of the Cabo de Gata Volcanic Complex outcrops at various points (Serrata de Níjar y Carboneras) and is formed of Betic basement rocks (carbonate rocks an phyllites) of the Betic Range Internal Zones and includes Betic Basement Rocks and some marine sediments. Towards the top, the volcanic activity is fossilised by marine sedimentary deposists of the terminal Miocene.
The zone includes a wide variety of volcanic forces, ranging from explosive to effusive and recording transient conditions during eruptions. Volcanic rocks of Cabo de Gata are calc-alkaline in composition and were erupted from submarine vents and deposited in submarine settings, although the rare faces record the transition to several settings. Therefore, volcanism in Cabo de Gata is essentially submarine, although some volcanic edifices and products may have arisen from above sea level. In terms of rock chemistry, eruptive style, age and depositional setting, volcanic successions in Cabo de Gata can be compared with similar examples from the volcanic arc of Japan. The Cabo de Gata volcanic zone constitutes the best exposed, best preserved and most voluminous record of the volcanic arc of the Betic-Rif Orogen and is certainly the most important record of submarine volcanism in the western Mediterranean area.
From the first volcanic episodes to the last, the sea invaded the volcanic relieves generating an extensive archipelago. In the marine basins between volcanic relieves marine sedimentary deposits were produced. We can recognize now five sedimentary deposits, from Lower Tortonian to Plieocene. These basins leave behind a catalogue of bioclastic carbonates, reefs, bioherms diatomites, breccias and many more. In these basins we can find evidence of events as important as the Mediterranean Messinian Salinity Crisis, when the Mediterranean dried out as a consequence of the disconnection with the the Atlantic Ocean.
In a precise moment of time, during the Messinian, the temperature of the water allowed the formation of the coral reefs. The se reefs in cabo de Gata are formed on top of the volcanic relieves, and the most important of them inside the Geopark are in Cerro de los Lobos, La Molata de las Negras, La Higueruela y Mesa Roldán. These relieves where islands or high sea bottoms colonised by coral reefs and could completely covered or sorrounded by cliffs.
5 million years ago, the sea occupied all the low lying areas from Sierra Alhamilla to Andarax Valley to Campo de Níjar, and onjly the part of the Sierra de Cabo de Gata and Serrata de Níjar were emerged. After the Plio Quaternary uplift, the coastline was displaced to the south. During the Quaternary, and due to the climatic changes, the sea level went up and down with variations of more than 130 m. Those variations are registered as a privilegiated record where you can find all the distintive sedimentary environments from continental ( alluvial fans, dune systems…) to littoral and transitional (submarine deltas in ramblas, beaches, lagoons… and many more).
The volcanic activity has generated in Cabo de Gata a hydrothermal system that developed a mineralization of economic interest which left behind a big impression in the life of the people and the landscape of the area. The Rodalquilar Gold Mineralization it´s obviously the most famous, but other lesser metal has been exploted like lead, zinc, copper and manganese.Other nonmetallic mineralization of commercial interest is linked with the volcanic activity too. Bentonites are actually the most important.
Hydrothermalism is produced when a magmatic body cannot reach the surface, cooling slowly at hundreds of meters of depth. This body can supplies heat to the area, reaching temperaturas of 400-500º C, and emiting fluids very rich in acid. These fluids can rise up through the rocks, transforming them in a process called Hydrothermal Alteration. Somehow and due to the ciruclation, these fluids cool and mix with water, which make all the metals and associates precipitate in fissures, fractures… Forming hydrothermal deposist as the one that we can observe in Rodalquilar.
On the slopes of the Isleta-Los Escullos you can observe several levels of sediments from different generations of alluvial fans, some embedded with others, with very flat surfaces and slightly inclined towards the sea. They represent different phases of fan formation along the Quaternary, due to changes in climatic, tectonic and sea level conditions.
Albufera (lagoon) closed by a coastal line of dunes and beach. The salt is exploited in salinas that determine the landscape of the lagoon and control to a large extent its water regime.
Small lagoon produced at the mouth of the rambla de Morales by the closure of the coastline/beach. The occasional breaking of the cord by the avenues in the dry river channel produces the temporary disappearance of the lagoon until the new reconstruction of the cord by the sea.
Pyroxenic Andesites of characteristic black color that stand out in the landscape, especially on the cliff north of Las Negras. These rocks are eroded forming bolos that accumulate in the beach of Las Negras.
Outcrop of andesitic pyroxene and basaltic andesitic breccias with alternating levels of different colors. They are very striking, in addition to the changes of color and very dark colors, the numerous taphonis that can be observed on the slope.
Islet or very steep reef near the coastal cliff of volcanic origin. It is believed to be part of an old volcanic building.
Temperate carbonates and reefs of the upper Miocene located directly above volcanic rocks. In detail there are several carbonate units separated from each other by discontinuities (paraconformities and unconformities). Basal volcanic rocks are fundamentally volcanic agglomerates, dating radiometrically at about 8'7 Ma.
Very prominent reef near the coastal cliff that has the shape of a finger as its name indicates. It is a remnant of the retraction of the coastal cliff in the area.
Open-pit mining of bentonites due to the alteration of volcanic ash flows in an aqueous medium. These clays are characterized by being powdery masses of white color, unctuous to the touch and very plastic.
Enclaves of carbonate rocks stuck between volcanic rocks. These are temperate carbonates of the lower Tortonian age platform, rich in red algae, bryozoans and bivalves, plucked, dragged and enclosed between more modern volcanic rocks (from the Upper Tortonian).
Bioclastic carbonates, very fragmented and well classified, with abundant remains of red algae, bivalves, bryozoans and benthic foraminifera. They are deposits of temperate waters. They show exceptionally well-preserved sedimentary structures, essentially tabular cross-stratification at the base, and cross stratification at trough at the top.
Tempered platform carbonates and ancient submarine cliffs deposited on, and in connection with, an ancient volcanic dome. The latter shows a precious columnar disjunctions.
Outcrop of dacites with amphibole at the foot of the road that, moreover, is located in a spectacular natural viewpoint over the beach of Algarrobico and Carboneras.
Group of coalescent domes composed of dacites with large amphibole and biotite crystals. They are massive rocks in which there are observed banded flux and columnar disjunction very patent. This disjunction was used to obtain paving stones in small abandoned quarries.
Andesitic dome and pouring levels of massive lavas and pyroclastics superimposed on the northwestern flank of the dome. They highlight these flows very well by differences in color and type of erosion.
Outcrop next to the current beach fossil wind dunes of the Plesitocene, oolitic composition. The sedimentary structures are spectacular.
Sector of the fault system of Carboneras in which this structure is very patent due to the variety of lithologies affected since plaster, marl, bioclastic sands, etc. arise between the fracture lines.
A geoform on volcanic materials, essentially dacite and andesite with structures and textures of gaps, castings and domes, elliptical, more than a kilometer in diameter, surrounded by higher reliefs also volcanic, thus offering a bucket morphology almost closed.
However, it is a capricious modeling produced by the erosion of meteoric agents, rain essentially, on the volcanic massif, accentuated and developed over time by the hillside runoff itself.
Old strait of Pliocene age that communicated by the north-northeast the basin of Almería-Níjar with the Mediterranean Sea and through which intense currents were canalized, that mobilized calcareous sands and formed directly great dunes in the marine bottom. The cross stratification in the trough is the internal structure shown by the dunes, as a result of their migration as they were displaced by the currents.
Since the end of the eighteenth century, deposits of lead and zinc were exploited in the Cabo de Gata area, which subsequently led to intense industrial activity. The discovery of the gold is made by the smelters of Mazarrón that used the jaspers of the mines as fluxes extracting the gold to make the process profitable.
In 1940 the Ministry of Industry launched the installation of Rodalquilar for the benefit of gold exclusively. This activity lasts from 1,940 to 1,966 when the installation is closed.
The volcanic rocks that emerge in the morrón are a succession of rhyolitic ignimbrites, ignimbrites and surges and lava flows of andesitic lavas. The exposure of the pyroclastic deposits on the cliff is spectacular. On the volcanic substrate, initially penetrating the cracks of the rocks, there are Pleistocene deposits of wind dunes with very good sedimentary structures.
The Pliocene sediments fill a small basin located on the southeast margin of the Almería-Níjar basin at the foot of ancient Paleoacantilados. Balanid pavements abound in the center of the bucket. The latter are very spectacular and consist of aggregates of balánidos, preserved in position of life and large (centimetric).
Very complete cut of the Tortonian-Messinian platform carbonates installed directly on volcanic rocks. At the extreme base, temperate open-shelf carbonates rich in bryozoans and bivalves appear. Above them, the first Messinian reef unit (that of the biohermos) is located, discordantly, Enciman appears the carbonates corresponding to the unit of the coastal reef, also of the Messinian. In the latter, the facies of construction (of corals, Porites, encased by microbial carbonates) and that of the slopes are distinguished. To the roof appears, the so-called Terminal Complex, also Messinian, constituted by platform carbonates in which oolites and microbial domes (stromatolites and thrombolites) abound.
Holocene beach formed by very rounded pebbles and gravels (bowls) of volcanic nature whose source is located in the reliefs of the environment, dragged and deposited by the ravine of the Eagles.
Impressive hialoclastic deposits consisting of a rock of volcanic origin composed of andesitic rocks with very variable sizes (diameters from millimeter to metric) encompassed in a matrix of very fine grain size. This type of rocks originated by submarine eruptions in submerged volcanoes under the sea. On the cliff itself we can also observe columnar disjunctions that indicate the location of the volcano's power source.
Succession of Tyrrhenian fossil beaches that emerge on the right side of the current rambla. We observe mainly the structures of "foreshore" and "shoreface" of a sequence of progradantes beaches, whose different episodes are quite well dated. In some episodes Strombus remains are recognized, which help to interpret the age and assume warmer climatic conditions than the current ones during the corresponding period.
Its sand covers a magnificent outcrop of oolitic fossil dunes between 100,000 and 128,000 years old. The cliffs that close the beach to the east, on which the San Ramón Castle is located, are built on one of the most representative outcrops of post-volcanic sedimentary materials in the Park, in this case constituted by bioclastic calcarenites with abundant remains of fossil marine fauna , of an approximate age of 6 million years (Messinian).
Pliocene carbonaceous platform progradante towards the south. It corresponds to the north margin of the old Pliocene basin of Carboneras. In the slopes are frequent storms (storm layers).
System of quaternary beaches and wind dunes, current and subactual, partly fixed by vegetation. The beach cord closes the mouth of the Rambla de Morales located to the east.
The two hills that make up the Frailes correspond to two volcanic domes that are the points of departure for the materials that make up the upper part of the hills (approximately over 200 m). The rocks are basaltic andesites about 8 million years old.
Alluvial fans at the foot of the Sierra de Gabo de Gata that descend to the Albufera de las Salinas lagoon. There are several laterally anastomosed cones in which the morphology of the sedimentary bodies and their genesis can be clearly recognized.
Antirrhinum charidemi of Cabo de Gata
This geopark is perhaps one of the greatest natural gems of the province of Almeria. Its volcanic origin, and the prevailing sub-desert climate, have characterized the development and history of its inhabitants.
The arid landscapes hide an enormous botanical richness, precisely from there their singularity is born, in the adaptations to a ferocious climate by means of strategies to survive extreme conditions. Endless roots, dormant seeds, survivors of salt water, exploiting the morning dew...
Ecosystems such the ones formed by the azufaifo (Ziziphus lotus), palmito (Chamaerops humilis), cornical (Periploca angustifolia), esparto (Stipa tenacissima), romero (Rosmarinus officinalis), thyme and grasslands, as well as the vegetation that populates cliffs and dunes, make up the botanical landscape of the park, together with traditional crops, such as sisal (Agave sisalana) , chumberas (Opuntia ficus-indica) and small orchards.
Despite the sub-desert nature of the soil, in the geopark there are more than 1 500 species of flora, many of them endemic, forming one of the most unique, diverse and unique areas of Europe.
In its seabed coexist, in perfect harmony extensive meadows of Posidonia oceanic with great diversity of aquatic fauna and flora favored by the convergence of two different marine masses, the Atlantic and the Mediterranean. This phenomenon, together with the different types of seabeds originate a high animal and vegetable diversity with a catalog of more than 1 300 animals and 300 vegetables.
The transparency of the waters is due to a large extent to the presence of one of the best preserved oceanic Posidonia meadows in the entire Mediterranean. This endemic plant of the Mediterranean Sea, which is commonly confused with an algae, plays a fundamental role in the control of erosion and as a source of oxygenation and is the habitat of more than 700 animal species. Among its leaves, we can find sea urchins, starfish, sponges, molluscs, algae and fish.
In the rocky backgrounds, the games of the cavities and light are colored by corals, and other fauna and flora that live attached to their walls.
The avifauna of the geopark is especially important in the coastal steppe, where steppe birds live as the trumpeter finch (Bucanetes githagineus), alcaravan (Burhinus oedicnemus), Dupont´s lark (Chersophilus duponti) and sison (Tetrax tetrax).
In the Ramsar site of Salinas de Cabo de Gata, where more than 80 species are concentrated, many of them are waders such as avocetas (Recurvirostra avosetta), cigüeñuela (Himantopus himantopus), although we will also find gulls, mallards and flamingos.
In the Sierra de Cabo de Gata are common raptors such as the Bonelli's eagle or the eagle owl and small mammals such as the common genet and the fox that complete the fauna of the natural space.