Geology of the Tabernas Basin - Junta de Andalucía

29 Pages·2009·2.56 MB·English

The Tabernas Basin
Geological Features

GEOLOGICAL FEATURES AND EVOLUTION
J. C. Braga - José M. Martín
SIMPLIFIED GEOLOGICAL MAP AND STRATIGRAPHICAL SUCCESSION FOR THE TABERNAS BASIN
Taken from Weijermars et al,1985
AGE LITHOLOGY DEPOSITIONALSETTING
NE
OCE
FILABRES O-PLEIST ALLUVIAL FANS.Conglomerates and sands
PLI
NE
OCE FAN DELTA and DELTA.Conglomerates and sandstones
PLI
Gypsum RESTRICTED BASIN
NO
Ram bla de Tabernas Tabernas MESSINIAN Seismite MMAarRlsIN E BASIN Filabres GDeeoslioegrtioca dl eS eTcatbioenrn as Alhamilla
Seismite Rambla de Tabernas Cerro
Geological Section Yesón alto CN-340 Alfaro
Alfaro (742 m) Reefs
ALHAMILLA Seismite
Geological Section (Gordo
SE AN Megabed)
NI
O
Baños ORT SUBMARINE FANS.Marls,sandstones and turbidites
Río Andarax SERREVALIAN-T
Pechina COASTAL PLATFORM.Conglomerates
GÁDOR
BETIC BASEMENT
Schists,quartzites,phyllites and marbles
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GEOLOGICAL FEATURES AND EVOLUTION
About eight million years ago (in the Miocene) extensive sedimentary package that the rivers intermontane basin between this new relief,to
the configuration of emerged and submerged eroded from the emerging relief.This material, the south,and los Filabres,to the north.
land around the littoral margin of Almería was comprising alternations of marl and sand,are
similar to that of today,but not identical:the sea amongst those which have,to a great part, In this depositional environment,marine at times,
extended through the territory of the Tabernas fashioned the eroded landscape of the Tabernas lagoonal for others,the deposition of limestones,
Desert up to the foot of the Sierra de los Filabres Desert. marls,muds and sands,and enclosed gypsum,
in whose borders fossil coral reefs of this age continued up until around 2 million years ago (in
formed,reliably marking the position of the Later,some 7 million years ago (in the Upper the Pliocene,almost at the start of the Quaternary),
ancient coastline.In the slopes of this ancient Miocene),the Sierra Alhamilla was uplifted, when the sea ultimately retreated,leaving the
sea,submarine fans deposited a thick and closing a narrow and elongated,marine sediments exposed to the action of erosive agents.
DISTRIBUTION OF EMERGED LAND 8 MILLION DISTRIBUTION OF EMERGED LAND 7 MILLION DISTRIBUTION OF EMERGED LAND 4 MILLION
YEARS AGO YEARS AGO YEARS AGO
1 2 3
Vélez-Rubio Guadix Huercal-Overa Vera Guadix
Alcalá la Real Baza Almanzora Vera
Corridor
Huercal Sorbas
-Overa Tabernas Sorbas
Tabernas
Granada Guadix Vera Carboneras Carboneras
AlhNaLmeara jTaórtolaMotril AdBrearja ATalmbeerrníaasSoCrabrabsoneras Present DaAyd CroaaBstelrinjae Almería Andarax Corridor APdrreasBeenrtja Day CoastlinAe lmería Mediterranean Sea
Present Day Coastline Western Basin
Reefs Braga,Martín and Quesada
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GEOLOGICAL FEATURES AND EVOLUTION
The Tabernas Basin has been
configured since then as a long
and narrow depression
Graphic Scalebar
(approximately 20 km in length
abnedtw 1e0e knm th ien Smiearxraim duem lo wsidth) SIERRA DE LOS FILABRES VERA
Filabres and the Sierra Alhamilla,
situated to the west of the SORBAS CABRERA
Sorbas Basin and in continuation
with it. TABERNAS ALHAMILLA
CARBONERAS
NÍJAR
SIERRA DE GÁDOR
ALMERÍA
CABO DE GATA
Neogene Sediment
Neogene Volcanic Rocks
Betic Substratum
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THE ERODED LANDSCAPE
The soft nature of the sediments that have filled storms.Within them the riverbeds are very
the Tabernas Basin from 10 to 8 million years broad and well-fitting,with steep and vertical
ago,the slow and continual uplift of the sierras sides,although they generally appear dry.
that border it,and the arid yet stormy climate
that has characterised this territory for a good In the soft and readily eroded foothills,the
part of the more recent Quaternary,have stream produces grooves,which grow towards
conditioned the model for one of the most rills and runnels,and terminate in furrows
spectacular erosive landscapes in continental separated by sharp crests.This landscape
Europe. is given the name ‘Badlands’,alluding to its
difficulty for being worked or put into
A geological landscape reminiscent of Africa agricultural production.
that has captured the attention of geologists,
naturalists,geomorphologists,photographers Turbidite sequences in the Tabernas Desert .
and film producers for generations:the Tabernas
Corridor,the most southerly desert in Europe.
This spectacular erosive landscape is not,
therefore,attributable to human action,but to
the concurrence of a series of geological factors
and its own natural evolution,upon which the
peculiarity of being one of the most important
scientific and educational places for the study
and comprehension of the natural phenomena
of erosion and desertification in the
Mediterranean Basin has been conferred.
The temporary and torrential character of
precipitation generates a rambla type of fluvial
system,normally dry,but which discharges
a great amount of sediment and water in an
Eroded landscape of the
almost instantaneous manner during strong Tabernas Desert.
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Evolution of the Drainage Network
Antonio Martín Penela
4 MILLION YEARS AGO 2 MILLION YEARS AGO
FILABRES
The eroded landscape of the Tabernas desert is During the latter stages of the Pliocene,around
a consequence of the geological evolution of Tabernas 2 million years ago,the elevation of the
the region over the length of the last 4 million mountainous relives and the fall in sea level
years,and more specifically,of its tectonic and Pliocene continued,since then practically all of the
Coastline
climatic evolution in the past 150,000 years. Province of Almería has become emerged.
ALHAMILLA
In the Lower Pliocene,about 4 In this period,areas subjected to erosion and
Mediterranean Sea
million years ago,a fall in sea level areas of sedimentation were differentiated.
took place simultaneously with a The latter were represented by small lakes
strong uplift of the adjacent relieves, installed in the most low-lying zones,and
GÁDOR
Sierra Alhamilla,Sierra Gador and alluvial fans in those that material coming from
Sierra de los Filabres,already emerged Almería Pre sentDayCoastlin the recently-formed mountainous massifs was
and with some elevation.As a consequence, e deposited.
broad surfaces of the region became emergent
FILABRES
and important fan deltas developed that The main drainage during this period
collected water coming from the Sierra de los were made up of a fluvial system
Filabres.One of these is the precursor of the of close appearance to the
modern River Andarax,that already occupied modern River Andarax,which was
Tabernas
a similar position,although its river mouth forming an important delta in its
(outlet) is somewhat displaced to the north, outlet to the Mediterranean.
ALHAMILLA
towards the position of La Rioja.
Palaeocoastline
GÁDOR
Present Day Coastline
Almería
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Evolution of the Drainage Network
THE PRESENT DAY
FILABRES
The establishment of more arid climatic
conditions in the Upper Pliocene,led to the
total desiccation of lacustrine areas and almost Tabernas
total inactivity in the alluvial fans.It is since this
period when erosive processes clearly became
dominant in the region,initiating the sculpture
of the modern landscape and the ALHAMILLA
Distribution of streams in a section of the
development of the fluvial network,which
Rambla de Tabernas.The high drainage
deeply excavated the Neogene and Quaternary density (increased number of streams per
unit of surface area) is typical of gullied areas.
sediments in the Tabernas Basin.The Andarax
River continued as the principal river,in which
all the water from the basin is drained,even
if in reality the water and sediment carried by GÁDOR
it to the sea is quite scarce.
Since the late Pleistocene,at a time when the
modern configuration of the fluvial network Almería
was initiated,the factors that have allowed its
strong incision,the development of badlands,
and its general evolution have been:tectonics,
the nature of the material,weak and easily-
eroded lithologies,and the climatic conditions.
Characteristic features of the present-day
erosive sculpture in the Tabernas Desert.
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Ramblas
Antonio Martín Penela
Ramblas constitute the main arteries of majority of cases,circulating only water from of factors such as progressive uplifting of the
the drainage network in the Tabernas Basin. surface currents originating as a result of region,the arid and stormy climate,the soft and
Through these the transport,and also the storms.The erosive processes in the ramblas erosive nature of the material.
deposition,of particles coming from the erosion take place during floods,excavating laterally
of the basin and the surrounding sierras is along the length of its margins. The rivers of the Tabernas Basin are continually
achieved. down-cutting,trying to reach their equilibrium
During the last 100,000 years the ramblas have with the base level of the sea.The occasional
They comprise braided fluvial systems, evolved,deepening and widening their river torrential precipitation and sparse vegetation
characterised by the development of numerous beds,starting to form valleys almost 100 metres cover allows an intense water-bourne erosion
sandy bars between which multiple channels deep and river courses whose width exceeds a that unleashes an intense processes of incision,
are initiated during flood periods.The flow of hundred metres.This important development of with a dense drainage network of dendritic
water in the riverbed is ephemeral,in the rambla valleys is a consequence of a combination type,and abrupt and unstable hillsides.
1 2 3
BASE LEVEL BASE LEVEL
BASE LEVEL
At the end of the Pleistocene incision of the fluvial network was In the Holocene the rivers excavated deeply in order to reach their equilibrium with base level.
initiated.The ramblas adopt a meandering morphological pattern. It produced a generalised incision of the river courses.
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Mechanisms of erosion in the desert: currents
Antonio Martín Penela
RAINDROP IMPACTS SHEET EROSION
Raindrops tear away Hardened ground
particles of the ground that favours the initiation
are transported down slope of sheeted flows,
by saltation.This process helped by the slope,
hardens the surface. that remove and
entrain the material.
Ground encrusted by the effects of raindrop impacts. Fairy Chimneys :Small mounds of ground protected from sheet erosion by more resistant
fragments of rock.
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