GGeoeollogogyía ofdel theentornoArid Zone árido of f almerienseAlmería South East Spain

An educational field guide Geology of the Arid Zone of f Almería South East Spain

An educational field guide This guide has been produced and financed with the support of the hydrological management project between the Carboneras Desalinisation Plant and Almanzora-Western Almería Council. In the Natural Park of Cabo de Gata and its area of influence, a grant given by the Southern State Water Company (ACUSUR) and the Regional Ministry of Environment (la Consejería de la Junta de Andalucía), is gratefully acknowledged

Editor, Technical Director and Co-ordinator: Miguel Villalobos Megía Scientific Supervisor: Juan C. Braga Alarcón Authors: Juan C. Braga Alarcón José Baena Pérez José Mª. Calaforra Chordi José V. Coves Martínez Cristino Dabrio González Carlos Feixas Rodríguez Juan M. Fernández Soler José A. Gómez Navarro José L. Goy Goy Adrian M. Harvey José M. Martín Martín Antonio Martín Penela Anne E. Mather Martin Stokes Miguel Villalobos Megía Caridad Zazo Cardeña

Word Processing: Juan González Lastra Infographics: Félix Reyes Morales Design: Teresa del Arco Rodríguez, Juan Sánchez Rodríguez, Juan González Cué Photography: The photographs are the property of the authors whose names are inserted in the section headings, except for where specified at the foot of the photograph (in brackets) Translation: Jason Wood

© of the edition: State Water Company for the Southern Basin SA (ACUSUR), 2003 © of the edition: Regional Ministry of Environment, 2003 © of the 2nd edition: Fundación Gypaetus, 2007 © of the data, text, photos and illustrations: Authors, 2003

Technical Assistance: Tecnología de la Naturaleza, SL (TECNA)

Printing: Bouncopy ISBN: 978-84-935194-7-6 Legal Deposit: xxxxxx uring recent decades, the Province of Almería has developed as one of the more economically dynamic regions of Andalucía and Spain. Its exceptional environmental D conditions due to a favourable geographical situation, and the enterprising character of its people, have made the blossoming prosperity and rapid consolidation of one of the most vigorous and technologically advanced horticultural zones in Europe possible. However, through time, this shining development has come to have a negative bearing on a historical problem in Almería: the scarcity of hydrological resources. In reality the hydrological demands for agricultural use considerably exceed the natural resources that are available, so that as a consequence, it has motivated a growing social sensitivity and demands for solutions to this problem.

This situation has required, on the basis of their competency, the intervention of the Medio Ambiente (Environmental Agency), which through the public company Aguas de la Cuenca Sur S.A. (ACUSUR), has put an ambitious plan of action into practise: the Global Plan of Priority Hydrological Action in Almería Province, known as Almería Plan, whose work, is declared to be of general state interest.This plan has meeting the demands for water of the agricultural organisations in the Almerían coastal zone as the main objective.

Part of this work, on the other hand, has been the need to achieve protection of a region with exceptional ecological and environmental value, at times not fully recognised amongst its own population. Indeed, through strict application of the criteria developed by the European Union in its Strategy for the Preservation of Biodiversity, the Province of Almería, and especially its semi-arid zones, are declared to be one of the regions of greatest environmental and ecological importance in Europe.The presence of unique habitats, the biological diversity that provides a wealth of species, turns the east coast of Almería into a veritable “Natural Wonder” in the context of continental Europe. To all this can be added the exceptional geological value placed on these arid landscapes. All of these conditions mean that Protected Natural Spaces have already been declared and proposed as places of community interest, and these occupy a considerable area of Almería. By European law, the Spanish government must guarantee their conservation. In order for the partly unavoidable work of the Almería Plan to go through in these precious spaces, both the Junta de Andalucía (provincial government) and the Medio Ambiente (environmental agency), given their respective environmental concerns, decided to maximise the methods of environmental protection. All joint work has been subjected to rigorous controls and has employed a significant use of correctional means, whose aim is to reduce the extent of the possible environmental impact that work generates in the construction phase.

In a complementary fashion, several administrations had agreed to fulfill the European Habitat Directive, putting into place a broad program of compensatory measures. In this case the ultimate aim is contributing to an improvement in the global quality of the natural environment of these regions that were affected by the management of new hydrological resources, but also with the purpose of spreading an awareness amongst the inhabitants of these regions that everyone must keep a vigil and act in a responsible manner in order to conserve the environment.

The volume that is presented is framed in this context. A publication that we hope will contribute to drawing the Almerían population closer to the exceptional qualities of the natural environment which surrounds them. A recognition essential for establishing the basis of respectful relationship, that will make both the conservation and sustainable use of this noble region a possibility.

Teófilo García Buendía Fuensanta Coves Botella Manging Director of ACUSUR Director of the Medio Ambiente Index

PROLOGUE Prologue ...... 10 How to use this guide ...... 11

INTRODUCTION The Geological Timescale and some basic geological principles ...... 13 Largescale Geological Units in Andalucia ...... 16 Largescale Geological Units in the arid region of SE Almeria ...... 17 Geological History and Geographical Evolution of SE Almeria ...... 20

NEOGENE BASINS OR DEPRESSIONS OF ALMERIA The Almeria-Nijar Basin ...... 21 · Geological Features and Evolution ...... 23 · Volcanic Periods ...... 25 - Origin of magmatic processes and volcanic features ...... 25 - The Cabo de Gata volcanic complex ...... 29 - Hydrothermal Alteration and mineralisation in the volcanic complex ...... 32 - The gold of Rodalquilar ...... 34 · Sedimentary periods in the volcanic archipelago ...... 37 - Sedimetary episodes ...... 37 - Deposits of the earliest marine basins ...... 39 - Re-initiation of sedimentation since the last volcanic period ...... 40 - Messinian reefs ...... 42 - Evaporites and carbonates since reflooding of the Mediterranean ...... 43 · The last period: recent evolution and continentalisation of the Bay of Almería ...... 44

· DIDACTIC ITINERARY: THE ALMERIA-NIJAR BASIN ...... 47 1. Alluvial dynamics of the ramblas: Las Amoladeras ...... 49 2. Fossil beaches of the Rambla de las Amoladeras ...... 52 3.The dune system at the outlet mouth of Rambla Morales ...... 55 Index

4.The lagoon of Rambla Morales ...... 56 5.The Salinas (Saltpans) of Cabo de Gata ...... 58 6. Volcanic Domes of Punta Baja, El Faro and Vela Blanca ...... 61 7.The volcanoes of Mónsul ...... 64 8.The Barronal dunefield ...... 65 9.The Los Frailes volcano ...... 66 10.The fossil dunefield of los Escullos ...... 68 11. Infilling Alluvial Fans of la Isleta-Los Esculllos ...... 70 12. Volcanic calderas of Rodalquilar ...... 73 13. Mining and mineralogical processes in Rodalquilar ...... 76 14.Post-volcanic sediments at la Molata de Las Negras ...... 79 15.The bentonites of Cabo de Gata ...... 82 16. Marine sediments of Cañada Méndez ...... 86 17.The quay at Agua Amarga ...... 89 18.The Mesa Roldán reef ...... 92 19. El Hoyazo de Níjar ...... 95

The Sorbas Basin ...... 97 · Main Geological Features ...... 99 · The Sorbas Karst ...... 102 - Origin of the Sorbas gypsum ...... 102 - Karst : slow dissolution of rocks ...... 105 - Genesis and evolution of the gypsum karst of Sorbas ...... 106 - Surficial karst landscape of Sorbas ...... 107 - Subterranean scenery: dissolution features ...... 108 - Subterranean scenery: crystallisation features ...... 110

· DIDACTIC ITINERARY: THE SORBAS BASIN ...... 111 1.The southern margin of the Sorbas Basin and panorama at Peñas Negras ...... 113 2.Turbidites of the peñas negras fan ...... 115 Index

3. Infilling of the basin through until deposition of the gypsum: the Los Molinos del Río Aguas series ...... 117 4.The karst plain, the cornice (escarpment) and block falls ...... 119 5.The resurgence (springs) of Los Molinos ...... 121 6. Infilling of the basin after gypsum deposition ...... 122 7.Fluvial-karst barrancos: the Barranco del Infierno ...... 124 8.Fossil Beaches of Sorbas ...... 126 9. Dolinas ...... 130 10. Lapiés ...... 131 11.Túmulus ...... 132 12.The Cariatiz Reef ...... 133

The Tabernas Basin ...... 135 · Rasgos geológicos y evolución ...... 137 · Erosional Landscape ...... 140 · Evolution of the drainage networ ...... 141 · The ramblas ...... 143 · Mechanisms of erosion in the desert: currents ...... 144 · Mechanisms of erosion in the desert: evolution of slopes ...... 146

· DIDACTIC ITINERARY: THE TABERNAS BASIN ...... 149 1.The turbidite succession of the Tabernas submarine fan ...... 151 2.The Las Salinas travertines of the Tabernas Desert ...... 154 3.Escarpment landforms in the vicinity of Cerro Alfaro ...... 157 4.Tunnel erosion (piping) ...... 159 5. Quaternary alluvial fan-lake system ...... 161 PROLOGUE

he arid landscapes of Almería are possible to observe or interpret several of the three more corresponding to each of the three well known amongst professors of most outstanding geological features in Almería sedimentary basins that might be visited. T geology, and other taught subjects Province.These features are of great importance These three chapters each consist of a general related to the teaching of earth for understanding the origin and evolution of part, in which basic concepts required in order sciences, of an astonishingly high number the geological landscape in Almería; a history to understand the phenomena that are of European universities, who appreciate it and peppered with events so extraordinary as the interpreted in the field locations of the itinerary use it as a huge natural laboratory to carry out formation of the volcanic archipelago of Cabo area explained, folowed by a detailed practical field investigation.This has been due de Gata, the desiccation of the Mediterranean description of the proposed itinerary. to two special features, an extraordinary Sea or the colonisation of the coastline by geological record within its sedimentary basins tropical coral reefs. The itineraries are can be completed within the and the high quality of outcrop exposure. three most emblematic Natural Protected The guide aims to be a product that is simple to Spaces in eastern Almería and the immediate The geology of this region has, in fact, inspired use. On one hand it is intended for surrounding area: the Cabo de Gata-Níjar an enormous scientific literature produced at self-interpretation, or interpretation without the Natural Park, the Gypsum Karst Natural Park of the highest level. However, up until now assistance of a guide or teaching professional, at Sorbas and the Tabernas Desert Natural Park. publications of a more informative tone that the higher end of secondary education, the These are places where the didactic use of the seek to focus their efforts on the general university level, for different disciplines related guide for environmental purposes will arise, as educational potential of this exceptional to the teaching of earth and environmental well as it being the first, basic line of evidence in geological landscape, have not existed. sciences. On the other hand, it is a didactic management material used by the public. It is guide to support the teaching professional, that hoped that in this sense the guide can be easily This has been the objective of this work, to deal clearly “translates” information, so that it can be used and will increase the environmental with this singularly important geological region adapted to the most suitable pedagogical level understanding of the population visiting these with a broad vision in a manner that is more each time. emblematic Natural Spaces. widely informative.Within this volume, three itineraries are put forward, each one of which It has been structured into four large chapters, Miguel Villalobos Megía connects a series of field stops where it is an initial one of introductory character, and Guide Co-ordinator

10 How to use this guide

THE COLOURS IN THE GUIDE SYMBOLS AND COLOURS OF LOCATION MAPS FOR POINT OF INTEREST

This guide is structured in various sections that can be identified Location maps for points of interest are found in the didactic itinerary by a colour code in the lower and upper right corners of each sections.These are located in a box in the upper right corner of the page. page. The full page maps that appear at the beginning of each chapter have an additional explicative legend. The colours correspond as follows: The symbols and colours correspond as follows:

Introduction

The Almería-Níjar Basin

Didactic Itinerary of the Almería-Níjar Basin

The Sorbas Basin

Didactic Itinerary of the Sorbas Basin

The Tabernas Basin

Didactic Itinerary of the Tabernas Basin

11

INTRODUCTION. The Geological Timescale and some basic geological principles

Juan C. Braga - José M. Martín

There is a series of basic principles that one ◗ By studying the internal structure and needs to understand prior to setting out on any composition of rocks, their age (that should be explanation about the geology of a region: measured in millions of years) and the way that they are distributed in a region, geologists ◗ The geography and landscape of a region are can reconstruct the way in which the always changing.The mountains and valleys landscape and geography of the region has that surround us or the position of the changed, where the coastline was situated at coastline today have not always been as we different times, where there was a volcano, know them now, now, neither have these when the mountains were uplifted that are features always been there.The land that we emerged now, etc.This reconstruction is not walk on, in the majority of cases, has risen up simple and requires the accumulation of much from the depths of an ancient sea, and the knowledge from very distinctive specialist distribution of land and sea will change fields within geology. However, once through time. recognised, even with provisional status, such that our understanding will improve with time, ◗ These changes result from complex geological it is converted into a story that can be processes: sediments that are transformed into entertained. new rocks and erosion of rocks that already exist into sediments; uplift or emergence of ◗ All of these geological processes, without land areas, with the consequent retreat of the exception, are extraordinarily slow from a sea, and flooding of other areas, that are human perspective.The duration, the pace, invaded by seas and oceans, where of geological processes is counted in millions of accumulation of sediment starts again that will years.The pre-history and history of humans later be transformed into other rocks, followed has been instantaneous in comparison with the by renewed emergence and further long history of our planet that began at least destruction, etc. 4,600 million years ago.

13 THE GEOLOGICAL YEAR ◗ That the Palaeozoic era, in which distinct forms of life ◗ That the Tertiary era, with the development of the developed and diversified, reached up to the 13th of majority of mammals, reached up to the 30th of If we compressed all of the known geological time of our December. December.The first primates did not appear until the planet, some 4,600 million years, into a natural year of only 29th of December. 365 days, we would observe: ◗ That the Mesozoic era, that of the large reptiles, lived through to the 26th of December, the time at which, for ◗ That the Quaternary era, with the appearance of our ◗ That through the Precambrian, about which we know example, the great dinosaurs became extinct. more immediate relatives, occupied only part of the virtually nothing, save that it gave shelter to practically 31st of December. In fact, only towards the last minute no life, only extremely primitive forms lived through of the year did Homo sapiens sapiens, ourselves, until the 16th of November, almost a complete year. appear.

20 : 19 : 00.00 Sudden extinction of large reptiles (65 m.a.) JANUARY FEBRUARY MARCH APRIL 19 : 99 : 33.91 Appearance of the first primates (40 m.a.)

18 : 17 : 19.19 Appearance of Homo erectus (3 m.a.)

21 : 08 : 58.52 Appearance of Homo habilis (1.5 m.a.)

MAY JUNE JULY AUGUST 23 : 52 : 00.11 Appearance of Homo sapiens neanderthalensis (70,000 a.)

23 : 58 : 00.09 Appearance of Homo sapiens sapiens (35,000 a.)

23 : 59 : 48.28 Start of the Christian era (2,000 a.)

23 : 59 : 49.02 Fall of the Roman Empire (1,600 a.) SEPTEMBER OCTOBER NOVEMBER DECEMBER 23 : 59 : 58.57 Discovery of America (500 a.)

23 : 59 : 58.89 French Revolution (200 a.)

29 : 59 : 59.30 Start of the industrial revolution (100 a.)

00 : 00 : 00.48 Average duration of human life (70 a.)

Precambrian Palaeozoic era Mesozoic era Tertiary era Quaternary era 250

Upper

TABLE OF Holocene GEOLOGICAL TIME QUATERNARY 0.01 272 Pleistocene 1.8 PERMIAN Lower Pliocene 5.3 300

Miocene Upper

325 23.5 Oligocene 34 Lower CARBONIFEROUS CENOZOIC/TERTIARY CENOZOIC/TERTIARY Eocene

53 360 PALAEOGENEPalaeocene NEOGENE Upper 65 375 Middle 385 Upper Lower DEVONIAN 410 96 PALAEOZOIC Upper MILLIONS OF YEARS MILLIONS OF Lower 425 Lower SILURIAN 135 Upper 435 MALM Upper 154

MESOZOIC Middle 455 Middle DOGGER 470

180 ORDOVICIAN Lower 500 Lower LÍAS Upper 205

Upper Middle 230 Middle CAMBRIAN Lower

TRIASSIC JURASSIC245 CRETACEOUS 540 Lower 250 Proterozoic PRECAMBRIAN 2.500 Archean 4.600 15 Largescale Geological Units in Andalucia

Juan C. Braga - José M. Martín

In Andalucía three largescale geological units may be differentiated:

1. The Iberian Massif or Hercynian Massif piling up of rocks through thrusting during 3. The Neogene Basins or depressions overall of the Meseta outcrops to the north of the slow collision of the Alboran Plate up and comprise the third largescale unit in Guadalquivir and forms the mountainous onto the Iberian Plate, and later uplifting. Andalucía. During the emergence of the Betic lineament of Sierra Morena. It consists The primary internal structure is divided into Cordillera there were times in which the sea mainly of strongly folded and deformed, a younger External Zone, nearer to the extensively covered depressed regions that metamorphic (schists, quartzites and Iberian Massif, and an older Internal Zone, are emerged today, such as the Guadalquivir limestone marbles) and igneous (granites closer to the modern littoral zone.Within Basin and other intermontane basins like and similar) rocks, of very ancient age the latter, several stacked tectonic units can Guadix-Baza,Tabernas, Sorbas or Almería- formed between more than 550 and 250 be recognised, in turn, essentially from Níjar.They are young sediments, less than 25 million years ago (Precambrian and the bottom towards the top they include the million years old, characterised by having a Palaeozoic).They form part of the old Iberian Nevado Filábride Complex, Alpujárride very limited degree of deformation, such that continent whose coasts were covered by Complex and Maláguide Complex. they hold a great value for studying the the sea that occupied the greater part of the recent geological history in this western modern Andalucían territory. sector of the Mediterranean.

2.The Betic Cordillera constitutes the second GEOLOGICAL UNITS largescale unit, and the first formed from extension. This much younger, large alpine

mountain chain, had already started uplifting Hercynian Massif of the Meseta approximately 25 million years ago (in the Lower Miocene) and continues uplifting Neogene Depressions today. It runs from Cádiz in the west to Almería in the east, extending to Murcia, BETIC CORDILLERA Valencia and the Balearics. At the latitude of Campo de Gibraltar Complex the Rock of Gibraltar it is inflexed producing External Zone a more or less symmetrical structure along the north of Africa. Internally, a complex Internal Zone structure is present as a consequence of the

16 Largescale Geological Units in the arid region of SE Almeria

Juan C. Braga - José M. Martín

Almería is located, from a geological point of view, at the southeastern extreme of the Betic Cordillera. The old Betic relieves (Sierra de Gádor, Filabres, Alhamilla, Cabrera, etc.) constitute the margin and the basement of a series of much younger intermontane marine basins (Tabernas, Sorbas, Almería), that were filled with sediments simultaneously with the emergence of the Betic Cordillera structure. Meanwhile, in the vicinity of Cabo de Gata, numerous similarly recent volcanoe rumbled in full activity.These three geological terrains are Characteristic flaggy appearance (schistosity) of dark Quartzite crests in the Nevado- Filábride core of the Sierra micaschists in the core of the Nevado- Filábride Complex. Alhamilla (photo M.Villalobos). clearly distinguishable today in the surrounding Almerían desert landscape.

THE BETIC SIERRAS to their better resistance to erosion, are also Skirting the core of the previously mentioned The core of the mountains in this region common. mountains another band appears, also consists of very old rocks, some even around consisting of very old rocks although somewhat 550 million years old. They are grouped under Quartzites display dark, yellowish and orange younger than the former, that are grouped the generic name of the Nevado-Filábride colours, and also have a flaggy appearance, under the name of Alpujárride Complex Complex (alluding to the fact that they make although poorly defined. Metamorphosed (alluding to the fact that it extends from up a good part of the Sierra Nevada, and its limestones and marbles are also found but Alpujarra, where for one part it constitutes the eastern extension, the Sierra de los Filabres). to a lesser extent, such as those quarried in southern flank of the Sierra Nevada, and for They are mainly graphitic micaschists: display the Sierra de Macael. Locally rocks related to the other, the coastal chain: sierras de Lújar, dark, yellowish and orange colours with a slaty granite appear, known as gneiss. All of these Contraviesa, Gádor, etc.). appearance and a flaggy characteristic, that is arose from the transformation to say, they are divided into well-defined, (metamorphism) of existing rocks that more or less irregular laminations. Quartzites suffered elevated temperatures and pressures which form rough crests and sharp cliffs, due at great depth in the interior of the earth.

17 Largescale Geological Units in the arid region of SE Almeria

This strip mainly comprises two very distinct types of rock, easily recognisable in the field. One of these are schists, known in the region as 'Launa', which are slightly transformed clays, of vivid blue, red and glossy grey colours. Traditionally they have been used to make impermeable roof slates in the construction industry.The other rocks are limestones and dolomites, composed of calcium and magnesium carbonates, which produce white, Alpujarride limestone relief of the Sierra de Gador (Photo, M. grey or black escarpment relieves, for example, Typical purple colour of phyllites or 'Launas' in the material of the Alpujarride Complex (Photo, M.Villalobos). Villalobos). the north flank of the Sierra Cabrera, Sierra Alhamilla, the escarpments of Lucainena or Turillas, close to Níjar, or the many cliffs of the Sierra de Gador. All of these limestones and dolomites were formed at the bottom of a tropical sea more than 200 million years up by fractures.They are also mineralised, and THE SIERRA DE CABO DE GATA ago. Afterwards, in the same manner as the rest have historically been the object of exploitation of the material from the Alpujarride complex, to yield iron (Sierra Alhamilla), lead and silver The Sierra de Cabo de Gata is an individual they suffered transformation (metamorphism) at (Sierra de Gador and Sierra Almagrera), and mountain range, different to the others, formed elevated temperatures and pressures, which other minerals. from volcanic rocks during two stages of came about at great depth in the earth's volcanicity, one from approximately 14 to 10 interior. million years ago and the other from 9 to 7.5 million years ago. In reality, they represent only Material from the old Betic mountains has a small percentage of rocks of this nature, suffered an intense deformation expressed as constituting the bottom of the Alboran folds of distinct scales and fractures, in addition seafloor and extending to Melilla, outcropping to their slaty characteristics (schistosity). In some discretely in the Isla de Alboran. places the rocks are literally destroyed, mashed

18 Major Geological Units of arid SW Almeria

DEPRESSIONS OR LOW-LYING AREAS In these marine inlets the products of sedimentary erosion of the emerged land The rocks that occupy the low-lying areas of accumulated: boulders, pebbles, gravel, sand the Almerían landscape, modern depressions and mud. Limestone rocks also formed from such as the Almanzora Valley, Andarax Valley, the accumulation of the remains of marine Tabernas, Sorbas Basin, Campo de Níjar plain creatures. In a changing global climate, the or El Poniente or El Poniente, consists of region passed through cold and much warmer geologically young material, accumulated in periods. the last 15 million years, while the Mediterranean Sea surrounded the mountains and the In the warm periods, the seawater temperature Detail of stratification in Alpujarride limestone rocks (Photo, volcanoes of Cabo de Gata forming a small (in the western Mediterranean) was similar to M.Villalobos). archipelago.The Betic mountains, and in general those of the tropics today, in the order of 20º C, all of the Iberian Peninsula, were uplifted from and coral reefs developed along the margins of the depths of the Mediterranean Sea. islands and emerged lands.Theses coral reefs, like those of Purchena, Cariatiz, Nijar, Mesa Roldan, etc., are amongst the best fossil Volcanic rocks from this area formed a examples that exist in the world. landscape of volcanoes, submarine or emergent, individual or grouped, to form small islands. In colder periods, the western Mediterranean These volcanic structures are recognisable in the had a temperature similar to today, and terrain of Cabo de Gata, in many cases, where limestones were formed from the remains of red they are seen to form steep, more or less conical algae, bryozoans, molluscs etc., like those hills in the area: Los Frailes, Mesa de Roldan, occurring on the actual seafloor of the platform Cerro de los Lobos, La Tortola, etc. Brecciated that encircles Cabo de Gata.These conditions, or volcanic rocks (formed from fragments yet colder ones, prevailed in the region from of different composition or aspect) are very 5 million years ago. abundant, resulting from diverse volcanic processes: differential cooling of distinct parts of lava flows, eruptions, nuee ardentes, avalanches down the sides of volcanoes, etc.

19 Geological history and geographical evolution of SE Almeria

Juan C. Braga - José M. Martín

The Betic mountains (Nevado-Filabride and Later, around 7 million years ago, the Sierra de emerge, whilst those closest to the coast have Alpujarride complexes) originated from Gádor and Sierra Alhamilla emerged. Although been abandoned by the sea only recently from collision of the African continent with Europe. today they seem like high mountains to us, a geological point of view. For example, the The Betic rocks are formed from sediments they are believed to be quite young in high valley of Almanzora, above Albox, was deposited at the bottom of the sea hundreds of geological terms, and their rate of uplift on vacated by the sea around 7 million years ago, millions of years ago.These rocks were buried a human scale is very low, For example, the however, the sea extended over land at many kilometres of depth (beneath other average velocity of uplift for the Sierra surrounding the Bay of Almería until just rocks), under such pressure and temperature Alhamilla since emergence from the sea is less 100,000 years ago. that they were transformed, changing the than 2 cm each year. appearance of the minerals that make them up With the final retreat of the sea to its current (this process is known as metamorphism). Later, The last relief to emerge, which is for certain position, for the moment, the impressive they slowly emerged.The structure of the Betic the youngest mountain range of the peninsula, geological record for this area, accumulated Cordillera was yet to be uplifted at different is Sierra Cabrera that came out of the sea over a period of 15 million years, is exhibited in speeds according to the arrangement of blocks 5.5 million years ago. Almería under exceptional conditions of compartmentalised by large regional fractures. preservation. It is an area of maximum During the past 2 million years, Almería, like educational and scientific value for studying The Sierra Nevada-Sierra de los Filabres block, the rest of the planet, has suffered from strong and understanding the evolution of the for example, was the first to emerge from the Quaternary climatic variations. In the glacial Mediterranean and the formation of the Betic sea, around 15 million years ago, and has stages, the sea fell more than 100 metres from Cordillera over the past 15 million years. stayed up since this time, as the most elevated its present level and the climate was much relief in Andalucía and one of the most colder. In the interglacial stages, as now, the elevated in Spain and Europe.The bottom of sea was in a position similar to that of today, the Alborán Sea is subsiding and extending, and the climatic conditions would also have thanks to fractures through which volcanic been similar in character. material of Cabo de Gata was once extruded. Since emergence of the Sierra Nevada-Sierra The process of marine retreat from these de los Filabres, that still continue to be basins can also be seen in relation to the uplifted, the Sierra de la Estancias emerged present-day geography, in that the interior from the sea around 9 million years ago. depressions, those most removed from the modern Mediterranean, were the first to

20 The Almeria-Nijar Basin

Geological Features

Geological Features and Evolution

Juan C. Braga - José M. Martín

The Almería-Níjar Basin has been a small GEOLOGICAL LOCATION OF THE ALMERIA-NIJAR BASIN marine sedimentary trough since 15 million years ago, the time at which emergence of the relieves occurred, that today constitute the SIERRAS Sorbas Basin Sierra Nevada and the Sierra de los Filabres 1. Sierra Nevada 2 massifs, whose foothills were located at the Tabernas Basin Vera 2. Filabres coastline. 3. Sierra de Gádor 4. Alhamilla Vera Basin 5. Cabrera Sorbas In this period, however, the Almería Basin was 1 5 6. Sierra de Cabo de Gata not individualised from the Sorbas and Tabernas 4 Tabernas basins. In this marine basin, Níjar Carboneras sediments started to arrive from the 3 Almería dismantling of the emergent relieves through the fluvial network. Extensive submarine fans El Ejido were generated on top of the marine platform, 6 while the fully active volcanoes of Cabo de Gata were rumbling, probably fashioning Almería-Níjar Basin a tropical volcanic archipelago. Campo de Dalias Basin

It was much later, about 7 million years ago, when uplift of the Sierra de Gádor and Sierra Neogene-Quaternary sediments Neogene volcanic rocks Betic substratum Alhamilla caused the individualisation of the Almería-Níjar Basin, to the south of these same hills and between the emerged volcanic relieves The Almería-Níjar Basin therefore included all A region that had constituted a marine seafloor of Cabo de Gata. of the current, low-lying land present between during the last 15 million years in which Sierra de Gádor, Sierra Alhamilla, Sierra Cabrera a sedimentary record has remained, with Sierra Cabrera emerged 5 million years ago, and and the coastline, including the volcanic unsurpassed observable characteristics, it definitively separated the Sorbas and Vera relieves of the Sierra de Cabo de Gata. exceptional for the understanding of evolution in basins. the Mediterranean Basin at this time, and its geography, climate and ecology.

23 Geological Features and Evolution

SIMPLIFIED GEOLOGICAL MAP OF THE ALMERIA BASIN

According to Zazo and J. L. Goy Sierra de Alhamilla

Níjar

Sierra de Gádor

Gata Almería e d o b Ca Cabo e de Gata Roquetas de mar rra d Sie

Sª Alhamilla Alquián Sea level Sª Alhamilla

Níjar Pozo de Los Frailes Sea level

Old Quaternary terrain Miocene volcanic Recent Quaternary (Holocene) formations, from 10,000 years ago (Pleistocene: 1.8 Ma to 10,000 yrs) formations (15.7 to 7.9 Ma) to present Albuferas Pliocene terrain (5.2 to 1.8 Ma) Ancient basement Fluvial deposits (saltpans) Dunefields

Miocene terrain (23.7 to 5.2 Ma) Alluvial fans Travertines

Littoral barries and/or fringes Deltas 24 VOLCANIC EPISODES Origin of magmatic processes and volcanic features Juan M. Fernández

MAGMAS AND MAGMATIC ROCKS MELTING OF PRIMARY MAGMAS Main cone Magmas are formed through the partial melting Parasitic cone and emplacement of rocks at high temperature Lava flow in the interior of the Earth. They consist of a Plutonic rocks mixture of liquid, dissolved gases (water vapour and carbon dioxide) and minerals. Magma Dykes chamber Derived Magmas that come directly from the partial magma melting of rocks at depth are called primary magmas. Sometimes they reach the surface Partial melting straight away, however, it is more common that of the crust they remain static at different levels within the mantle and the continental crust, forming magmatic chambers. In such a situation the CRUST magmas may partly crystallize, assimilate MANTLE the country rock and suffer other modifications, the final result of which is a series of derived magmas of different compositions. This process is known as magmatic differentiation. minerals may crystallise in an ideal manner, matrix a proportion of small minerals of larger Magmas are generally less dense than the creating rocks with large-sized crystals such as size (phenocrysts) may be present, which had material within which they are forming, and, granites. crystallised previously in the magma chamber. therefore, they tend to climb up through the mantle and continental crust, until they cool and When the magma reaches the surface, it gives At times, during its ascent, the magma is crystallize, giving place to intrusive rocks. way to volcanic or eruptive activity.The results injected into fissures, forming dykes.These are are volcanic rocks and so-called volcanic also known as hypabyssal rocks. Magmas that solidify slowly underneath the features. Cooling is very rapid, so that the rocks terrestrial surface form bodies of intrusive do not crystallise well, forming a vitreous rocks. Cooling happens very slowly, so that the matrix or a very fine crystal size. Within this

25 Origin of magmatic processes and volcanic features

MAGMAS AND PLATE TECTONICS The origin of magma is related to the dynamics The origin of Cabo de Gata volcanism is of the lithospheric plate margins:The majority of complex, and under discussion at present. Although there are a great variety of types basaltic magmas originate through partial and compositions of magmas, the three most melting of the mantle in divergent plate In whatever case, it is related with the orogenic important generic types are the basaltic group boundaries (mid-oceanic ridges). Andesitic and process of crustal thickening in this area, (or basic, 50% of silica), the siliceous group siliceous magmas are generated in subduction the Alborán domain, due to the collision of the (or acid, 65 to 70% of silica), and the andesitic zones by partial melting of both the oceanic plate African and European plates; and afterwards group (or intermediate) such as those of Cabo and the continental crust. their thinning through phenomena of de Gata. extensional or transtensional character.

OCEANIC CRUST CONTINENTAL CRUST

Island arc TrenchMid-oceanic ridge Trench Rift valley

Plateau basalts

Continental crust Oceanic crust Upper mantle Lithospheric (asthenosphere) mantle

26 Origin of magmatic processes and volcanic features

ACTIVITY AND VOLCANIC FEATURES BASALTIC MAGMAS

The type of eruption and the products resulting PYROCLASTIC CONE OR CINDER CONE Lava flows STRATOCONE from volcanic activity depend, above all, on two important aspects: the viscosity of the lava, Pyroclastic levels which determines fluidity, and the gas content of the lava.

Basaltic magmas, poor in silica, are fluid. At the surface they flow rapidly, forming lava flows that at times travel great distances (this type of volcanism is known as effusive). If the basaltic lava is rich in gas, it is released with ease by ACIDIC MAGMAS means of intermittent explosions, creating pyroclastic types of cone (also known as cinder cones).The alternation of lava flows and DOMES OF SILICEOUS MAGMA pyroclastic episodes fashions another type of volcanic edifice known as the Stratocone volcano.

Acidic magmas, on the other hand, rich in silica, are much more viscous. Upon exiting onto the surface, they cannot flow easily, and form accumulations around the eruptive Pelean Dome Cumulate Dome Crypto-dome mouth (domes), or flow very slowly forming lava flows over short distances (this type of volcanism is called extrusive).

SOME TYPES OF DOME

27 Origin of magmatic processes and volcanic structures

EXPLOSIVE VOLCANISM IGNIMBRITES collapses into the vacated space, forming an PYROCLASTIC FLOWS enormous depression called a caldera. Some calderas can be more than 25 kilometres in The high viscosity of lavas from acidic magmas Ash diameter and several kilometres deep.When, after cloud means that on occasions gases cannot be the formation of a caldera, the magmatic chamber easily liberated, accumulating as bubbles, and Eruptive Column receives new supplies from deeper zones, the increasing their internal pressure until they are Volcanic interior of the caldera can return to a state of ash fall unleashed in enormous explosive phenomena uplift, a phenomenon known as resurgence. Nuee Ardente that violently erupt huge volumes of Pyroclastic flow The calderas are one of the most dynamically semi-molten rock into the atmosphere. active volcanic features and are frequently The so-called pyroclastic flows are generated associated with earthquakes, thermal activity, by this means, their solidification then geysers, hydrothermal waters etc. produces rocks known as pyroclastics. They can be of different types: BRECCIAS AND AGGLOMERATES FORMATION OF A VOLCANIC CALDERA

Ignimbrites Nuee A mixture of very hot gas, ash and rock Pyroclastic flow Ardente fragments is launched from the volcano in an Dome eruptive column.The density of the mixture, greater than that of air, means that it falls rapidly, smothering the underlying hillside in the form of a covering flow comprising a 1 glowing cloud of gas.They create rocks rich in ash and pumice. CALDERAS

Lithic Breccias or Agglomerates The largest and most explosive volcanic eruptions 2 The flow forms from the rupture, explosive or throw out tens and hundreds of cubic kilometres otherwise, of the summit of the volcano. of magma onto the earth's surface.When too Rock fragments that made up the actual dome high a volume of magma is extruded from a 3 dominate in this case. magmatic chamber, the earth subsides or

28 The Cabo de Gata Volcanic Complex

Juan M. Fernández

GEOLOGICAL CONTEXT AND AGE grown out of the sea sufficiently enough to in various cycles.The better-known and reach the surface, forming islands of volcanic conserved volcanic features are the most recent, The Cabo de Gata volcanic complex is the origin fringed by marine sedimentary platforms. produced between 9 and 7.5 million years ago. largest-sized element of all the volcanic manifestations in SE Spain. It continues to The age of the Cabo de Gata volcanic complex is The base of the volcanic complex outcrops at expand beneath the Alboran Sea, and has been known through the study of fossils present in various points (Serrata de Níjar and Carboneras) brought into its present position by the sedimentary rocks associated with the volcanic and is formed of Betic basement rocks operation of the Carboneras-Serrata Fault.The elements and from dating with isotopes (mostly (carbonate rocks and phyllites of the Malaguide greater part of volcanism in the Alboran basin is Potassium/Argon) in the volcanic rocks.Volcanic and Alpujarride complexes) and some marines actually submerged.The volcanic structures of activity developed in a broad period that extends sediments (marls) from the Lower-Middle Cabo de Gata also indicate signs of having been from around 14-15 to around 7.5 million years Miocene.Towards the top, the volcanic activity is generated, by and large, beneath the sea. Some ago (that is to say, Middle and Upper Miocene). fossilised by marine sedimentary deposits of the of the oldest volcanic structures could have During this interval the volcanic activity occurred terminal Miocene (Messinian reefs).

THE CABO DE GATA VOLCANIC COMPLEX WITHIN THE CONTEXT OF THE ALBORAN SEA SUBMARINE VOLCANISM

Sª de Los Filabres Calderas Volcaniclastic Mediterranean Sedimentary deposits Sorbas Sea levels Sª Nevada Sorbas (Alboran Sea) Basin Sea level Sª Alhamilla Níjar

Almería Sª de Gádor Basin Las Negras Polarca Serrata de Níjar Ridge Almería Adra S. Jose Islet Cabo de Platform Alboran Basin Gata Chella Carboneras Fault Bank Genoveses Betic Basement Pollux Ridge Bank Hydrothermal Magmatic Chambers Almería Canyon Neogene Basins Sabinal Bank Systems Emerged Volcanic Rocks Submerged 29 The Cabo de Gata Volcanic Complex

RELIEF FEATURES OF THE CABO DE GATA VOLCANIC COMPLEX

A Nijar-Almeria Serrata de Sierra de Basin Nijar Cabo de Gata PlioQuaternary Carboneras Miocene Volcanic Complex Basement Mesa Roldán ult Carboneras Fault s Fa ra ne C bo Car Agua Amarga La Serrata de Nijar is a zone of volcanic origin, associated with the Carboneras Fault. The rocks, concealed beneath the sedimentary filling of the Campo de A Níjar, have been uplifted and project outwards at the surface of La Serrata because they are caught up between different fractures in the fault zone. íjar N a de Las Negras rrat Se D Rodalquilar Rodalquilar Caldera B Del Garbanzal Dome-Flow Miocene sediments B Los lobos LA ISLETA

Ancient massive rocks White ignimbrites E Los Frailes Caldera

El Cerro de Garbanzal is a unique volcanic structure, almost circular in plan, San José formed by the extrusion of a massive dome-flow.The geometry of this type of structure is known in some places as fortified domes or 'tortas'. Quite eroded, it is preserved as a ceiling above marine sedimentary remains. Barronal Cabo de Gata 30 The Cabo de Gata Volcanic Complex

C D Messinian Conglomerates Carbonates Dome Breccias Caldera (reworked breccias) Sediments (Messinian and Pliocene)

Rodalquilar Complex Pre-Caldera Rocks

Volcanic Ashes Massive Nucleus

MAGMATIC CHAMBER Mesa Roldan (and Los Lobos) are excellent examples of volcanic structures fossilised by marine sedimentary rocks and crowned by terminal Miocene coral reefs. It may be characterised by an andesitic lava dome, enclosed by The Rodalquilar Caldera, one of the most notable volcanic features, was generated fragmented rocks (dome breccias), produced by submarine eruptions with because of the collapse of the caldera floor into the underlying magma chamber in little or no explosiveness. Linked with the Los Frailes volcano, they are the a series of highly explosive volcanic processes, producing the deposition of various most recent volcanic emissions in Cabo de Gata. pyroclastic rock units (ignimbrites).The later hydrothermal alteration of these rocks gave place to the characteristic mineral deposits of this area, especially gold.

RECENT SEDIMENTS E Post-Volcanic Sediments MESSINIAN CARBONATES Los Frailes Caldera Rodalquilar MIOCENE SEDIMENTS Pyroxene Andesites Frailes Complex LA SERRATA SEQUENCES Lighthouse PYROXENE ANDESITES Volcanic Sequences LAS NEGRAS AND CARBONERAS SEQUENCE ESTRADA DOME, PANIZA DOME, ETC. White Rhyolites Amphibole Andesites GARBANZAL DOME RODALQUILAR DOME The Los Frailes Volcano formed around 8 million years ago above older rocks (more than 10-12 ma) SEDIMENTS AND ALLUVIUM that extended towards the southern limit of the Sierra de Cabo de Gata. In this case, the volcanic ANDESITES WHITE RHYOLITES activity did not give place to typical central volcanoes, but to an extensive landscape of more or less Substratum BETIC BASEMENT dispersed volcanic domes. Levels of fossiliferous marine sediments were deposited between the phases of eruption of the different domes that serve as guide levels. Additionally, they produced some highly explosive eruptive processes (ignimbrites), related to the collapse of calderas.

31 Hydrothermal Alteration and Mineralization of the Volcanic Complex

Juan M. Fernández

HYDROTHERMAL SYSTEMS A. GEOLOGICAL SKETCH B. HYDROTHERMAL SYSTEM

The hydrothermal systems associated with the Cinto Los Tolles Rodalquilar Caldera Fumeroles volcanic complex of Cabo de Gata has generated important mineralization of economic interest whose profits have left a marked impression in the history and upon the countryside of this district.Without doubt, Meteoric the most acclaimed deposits are gold from Waters

Rodalquilar, exploited until very recent times. Magmatic Exploitation of other lesser metals has existed, Vapours (SO2, HCl, etc.)

however, such as lead and zinc, copper and Arribas et al.,Simplified from 1995 manganese. Magma Degassing from Magma

Other non-metallic mineralization of the surface, cooling slowly at hundreds of disassociated components to precipitate in commercial interest has also been generated in metres or a few kilometres of depth. In these fissures and fractures, forming hydrothermal association with this system. Bentonites are conditions, the sub-volcanic body supplies heat deposits, such as the famous Rodalquilar gold. actually the most important. Long ago the area to the surrounding area, that can reach had benefited from alunite, a mineral temperatures of around 400-500 C, and emits In Cabo de Gata, the main hydrothermal gold (aluminium sulphate and sodium or potassium) gases and acid-rich fluids, such as hydrochloric deposits are located in the Rodalquilar complex that was concentrated in yellow-coloured virgin or sulphurous (between 200 and 350 C). of calderas, associated with an intense zone of seams cutting the white-coloured and These hydrothermal fluids rise up through the hydrothermal alteration.This alteration zone is pulverised looking, altered volcanic rock. It has intruded rocks, transforming them produced by intrusion and cooling, beneath the numerous industrial applications, amongst (hydrothermal alteration) and cleaning many calderas, of a magmatic body.The hydrothermal others it is used as a source for the production chemical components out of them (lixiviation), fluids carried by this body wash out the gold at of alum, for the tanning of leather, etc. such as gold and many other metals that were depth and utilised the various fractures existing originally very dispersed in the rocks. Upon in the caldera to circulate and deposit the gold Hydrothermal processes are a frequent arriving in more surficial zones the fluids cool in more superficial zones.The formation age of phenomenon in volcanic areas.They are and mix with water of subterranean or marine the deposits is estimated at around 10.4 million produced when a magmatic body cannot reach origin, which provokes the metals and other years.

32 Hydrothermal Alteration and Mineralization of the Volcanic Complex

LOCATION OF MINERALIZATION THROUGHOUT MINERALIZATION CABO DE GATA

La Islica El Llano de D. Antonio Carboneras

Agua Amarga Fernán Pérez Smelting works of Los Alemanes Nuevos, to Bluish and greenish colouration Las Hortichuelas the west of San José, for the recovery of lead corresponding to superficial alteration Las Negras and zinc (photo J. M. Alonso). minerals of copper and lead sulphides. Rodalquilar

El Barranquete Exploitation of Manganese El Pozo de Los Escullos los Frailes from Cerro del Garbanzal. El Cabo Mineralization corresponds to de Gata San José Overview of typical scenery the dark zone. in bentonite clays: white- INDUSTRIAL MINERALS coloured powdered masses, Bentonites greasy to the touch and very plastic. Alunite METALLIC MINERALS Gold Galena and Blende Copper Manganese

Exploitation of alunite from galleries in the proximity of Rodalquilar.The mineralization corresponds Hydrothermal breccia of white to yellow-coloured veins chalcedony with native gold (lodes). (Photo Arribas).

33 The Rodalquilar Gold

Carlos Feixas

THE DISCOVERY delayed the mine consolidation throughout the The English company Minas de Rodalquilar (End of the 19th century - 1939) whole of the 20th century. handled a total of 107,000 tons of mineralized rocks until 1939, obtaining 1,125.5 kg of gold. The existence of gold in the Almerian district of This first stage of discovery of gold from Of these only 39 tons corresponded to the Rodalquilar was casually discovered at the end Rodalquilar, and the development of the first period 1936-1939. of the 19th century. Gold was detected in lead mines, coincided with the great Almerian smelting works of Cartegena and Mazarron, that economic crisis. This involved emigration utilised quartz coming from the lead mines of workers to Algeria, and subsequently to of Cabo de Gata as a flux.The Mazarron smelters America, a decline in lead mining and later in sought out the gold-bearing quartz, and with its iron mining, and a crisis in the grape market. scarce gold content they financed the cost of transport.

In an authentic state of gold fever many concessions were registered in this era that gave way to a multitude of litigation that

Old lodes economic for lead at the end of the 19th century in Ruins from the first treatment plant installed around 1915 in quartz dykes, from some of which the existence of gold was the Ma Josefa mine, in El Madronal (Rodalquilar) (Photo, Col. detected in Rodalquilar (Photo, Col. Evaristo Gil Picón). Extraction workers in the Los Ingleses Mine (around 1930) Evaristo Gil Picon). (Photo, Col. Evaristo Gil Picón).

34 The Rodalquilar Gold

THE DREAM (1940-1966) Cerro del Cinto area, where mineralisation Until 1966 Rodalquilar lived its golden dream. appeared in a disseminated form in the acidic Its population came to reach 1400 inhabitants. In 1940, the state decreed the seizure of the volcanic rock body, determining a 4000 ton It was furnished with infrequent services for this mines, entrusting the task of investigation to mass of mineralised rock with 4.5 grams of gold time in rural populations, cinema, social club, the Spanish Institute for Geology and Mining per ton. administration buildings, school, etc. (IGME), that looked at the old lodes that had been exploited without favourable results. Until 1942, the date at which this seizure ended, a total of 37 kg of gold was recovered.

At the end of 1942 the National Institute of Industry (INI), through the Adaro National Enterprise for Mineral Investigation (ENADIMSA), amplified and intensified investigations, abandoning the lodes and concentrating in the

Drilling workers in the open cast mines opened during the May 1956.The head of state at that time attends the production 'El Ruso’,first transport lorry for the Rodalquilar mines ENADIMSA period of exploitation (Photo, Col. Evaristo Gil of one of the gold ingots,with all of the propaganda exhibited (around 1940) (Photo, Col. Evaristo Gil Picon). Picon). by the regime (Photo,Col.Evaristo Gil Picón). The Rodalquilar Gold

In the first years of activity from this period REALITY (1967-1990) so often realised by national mineral concerns, in the order of 700 manual labourers worked in including, to a greater degree, foreign ones. Rodalquilar, the greater part of them dedicated The closure of the mines in 1966 put an end to This period is characterised by intensive to the construction of infrastructure and the period of splendour. A little afterwards the investigation of the Rodalquilar mining district, workings. At the end of this, between 200 and population declined very abruptly to 75 but having emphasis on genetic models of gold 300 workers were permanently involved in the inhabitants, in summary nearly identical to that mineralisation. exploitation. ENADIMSA continued, in principle, of today. with the subterranean system of extraction In spite of all this reality prevailed, although it is that had been emplaced by the English. After exploitation was carried out by ENADIMSA estimated that that around 3 tons of gold In1961, however, the first open cast workings in the previous period, the concessions and reserves are awaiting recovery, their exploitation were undertaken in the Cerro del Cinto. licences returned to their owners. Even though is not possible because of the complexity of the investigation had been forgotten in this period, deposit. During this period the bulk of gold production in Spain shifted to Rodalquilar, with more than 90% of the total production. However this dream only lasted a while. Investment exerted pressure to make new workings, and salary rises in the 70's decade considerably increased the production costs in a deposit already so difficult because of the irregular distribution of economic reserves. All of this forced the closure of the workings in 1966.

Mining town of Rodalquilar (photo Evaristo Gil Picón).

36 SEDIMENTARY BASINS IN THE VOLCANIC ARCHIPELAGO Sedimentary Episodes Juan C. Braga - José M. Martín

From the first volcanic episodes and TERTIARY BASINS IN THE SOUTHEASTERN PENINSULA GEOLOGICAL MAP OF THE CABO DE GATA AREA subsequent to the last, the sea invaded the volcanic relieves generating an extensive archipelago. In the marine basins between volcanic relieves marine sedimentary Vera deposits were produced. Five sedimentary Sierra de Filabres episodes can be recognised: Sorbas Cabrera Alhamilla Carboneras Carboneras Níjar 1. In an early episode sediments were Sierra de Gádor deposited upon the first volcanic rocks. Almería Fernán Pérez Their age is Lower Tortonian (between Cabo de Gata 9 and 8.7 million years).They are mainly Almería Basin bioclastic carbonates. Neogene Sediments Serrata Neogene Volcanic Rocks Las Negras 2. In a second phase sediments formed above Betic Substratum Rodalquilar rocks of the last volcanic event.Their age is Upper Tortonian to Messinian (between 5.5 and 6.5 million years ago).They are also bioclastic carbonates, and marls, that accumulated in deeper zones.

3. Above the previous episode, a series of Cabo de Gata related units characterised by the presence of reef bodies were deposited.Their age is San José Messinian (around 6 million years old).

Key in the following page >>

37 Sedimentary Episodes

4. After the deposition of the reefs a thicknesses of gypsum and other salts were phenomenon known as the Mediterranean deposited. Above these, or above the eroded SEDIMENTARY EPISODES Messinian Salinity Crisis took place.The surface, carbonate sediments typical of warm Mediterranean dried out 5.5 million years ago seas were deposited: oolites and stromatolites. as a consequence of its disconnection with the

Undifferentiated Recent detritus Atlantic. During this period material around 5. A last marine episode that passes into the borders underwent partial erosion and in continental deposition half way through 5º Conglomerates the central area of the large Mediterranean (in the Pliocene, between 5 and 2 million Basin, and in its marginal basins, important years ago). Bioclastic Sands

Marl, Mud and Sand STRATIGRAPHY OF THE CABO DE GATA AREA Calcareous Breccia 4º Sierra Cabrera Cabo de Gata Carbonates with oolites and stromatolites QUATERNARY

Gypsum

Coastal reefs PLIOCENE

Bioherms, patch reefs 3º

Reef Blocks, slumps MESSINIAN

Marls, at times with intercalated diatomites or calci-turbidites

2º Bioclastic carbonates, locally volcaniclastic conglomerates

Volcanic rocks of around 8 million years old TORTONIAN Millions of years 1º Bioclastic carbonates, locally volcaniclastic conglomerates

Volcaniclastic rocks more than 9 million years old or undifferentiated

Betic Substratum: Micaschists, Quartzites, Dolomites, Amphibolites, etc

38 Deposits of the First Marine Basins

Juan C. Braga - José M. Martín

Since the formation of the earliest volcanic relieves of Cabo de Gata the sea invaded the area generating small marine basins, extensions of the self-same Mediterranean Sea. In these small marine basins, and above the volcanic relieves, the first marine sediments known in the Cabo de Gata area were deposited, some 9 to 8.7 million years ago (Lower Tortonian). The majority of the rocks are carbonates coming The sea, in the Lower Tortonian, surrounded Details of the present-day sea bottom at La Sediments (bioclastic carbonates) from the volcanic relieves.The coastline had Polarca.The organisms (bryozoans and red the Lower Tortonian comprising the from sediments formed by skeletons (fossils) of characteristics similar to those of today. algae) are similar to those that were living remains of fossils of bryozoans, red bryozoans, bivalves, calcareous red algae, and producing sediment in this period. algae and bivalves. echinoderms (sea urchins), barnacles, and foraminferans (these types of rock are denoted The Agua Amarga Basin, for example, was PALAEOGEOGRAPHY OF THE AGUA AMARGA AREA 9 MILLION YEARS as bioclastic carbonates).These fossil remains a small prolongation of the AGO (LOWER TORTONIAN) (shells, winkles etc.) are quite similar to those Mediterranean during this period that PalaeoCoast organisms that are actually living in the extended between recently emerged line Emerged Mediterranean waters just off of Cabo de Gata volcanic relieves in the Cabo de Gata area. Land today. Together with carbonates generated by Sedimentary structures indicate that the Sedimentation within living marine beings, sediments also bioclastic carbonates from the Lower marine basin Present accumulated through the denudation of the Tortonian in the Agua Amarga Basin Coastline Agua volcanic relieves emerged there (these are formed in littoral and shallow Amarga Taken from Betzler et al. 1997 called volcaniclastic deposits). marine environments. Furthermore, one can The Agua Amarga Basin, towards the west of the understand a succession in this town, is one of the areas where these sediments material, in which each phase are better represented. had a distinctive geography, Cross stratification stemming from the characterised by different accumulation of sand-sized carbonate grains of the skeletons of marine organisms sedimentary processes. (bryozoans, bivalves, red algae, etc.) in submarine dunes at little depth.

39 The Re-initiation of Sedimentation After the Last Volcanic Episode

Juan C. Braga - José M. Martín

The last volcanoes in the Cabo de Gata area were active between 8.7 and 7.5 million years ago. In this period the domes of some of the most characteristic relieves of the Natural Park were formed, like those of the upper part of Los Frailles, the Cerise de Lobos and Mesa de Roldan.The extrusion of volcanic material broke through the older sedimentary rocks in some places, enclosing blocks within some of the lavas.

On top of these new volcanoes, and on occasions on top of older rocks, towards the end of the Tortonian geological stage, around 7 million years ago, a shallow marine platform Volcanic eruptions fragmented the sedimentary rocks from the lower episode (Lower Tortonian), light pink was initiated that marked a renewed incursion material in the photo, and enveloped them in lavas, dark material in the photo. of the Mediterranean around the archipelago of small islands generated by the volcanic activity. In this shallow marine environment mostly carbonate sediments formed from the remains of marine fossils that were deposited, for which reason they are called bioclastic carbonates.

Present-day marine bottom in Cabo de Gata.The Upper Tortonian bioclastic carbonates comprising the organisms present (bryozoans, bivalves and red algae), fossil remains of bryozoans, bivalves and red algae. are the carbonate producers, that accumulate on the bottom generating carbonate sediment.

40 The Re-initiation of Sedimentation After the Last Volcanic Episode

Inside these shallow marine basins the organisms with a marine flora.The carbonate particles depth the carbonate particles became finer each produced from carbonate, that is to say those that produced in this factory were distributed by storms time and, finally, gave way to marls formed from have shells, chambers etc., lived in a preferred style towards the coast, where they accumulated a mixture of clays, transported into the sea by immediately beneath the zone pounded by the in beaches and bars, and out towards the sea, in suspension, and microskeletons of planktonic surf, associated to a great extent by plant meadows successive sheets.Towards zones of even greater organisms.

SEDIMENTARY MODEL FOR THE UPPER TORTONIAN

Nivel del mar

Beaches

Shoals Factory

Fan Sheets

Stratification and cross-lamination typical Trough stratification typical of submarine Accumulations of the remains of organisms Sheeted fans in the Rambla de los Viruegas. of beach depsoits. dunes in shoals. that produce carbonates.

41 Messinian Reefs

Juan C. Braga - José M. Martín

CORAL REEFS

Some 6 million years ago, in the Messinian geological stage, and after deposition of the temperate carbonates and marls described previously, an increase in the water temperature allowed the formation of coral reefs in the SE Peninsula and, particularly, in the Cabo de Gata region. At the present day, coral reefs live in waters of little depth in intertropical latitudes, where the average winter water temperature does not fall under 20º C. In these sites huge volumes of rock and sediment are constructed by means of their calcareous skeletons.The presence of reefs in our region indicates that, in the period of their Reefs constructed from coral (light tones in the photo), fringing islands of volcanic origin in modern seas, as would have happened 6 million years ago in Cabo de Gata. formation, the water was warmer than in the modern Mediterranean.

In Cabo de Gata the coral reefs formed on top Coral reef of or around the volcanic relieves. Some of the most characteristic places within the Natural Park are found to be the reefs of Cerro de Los Lobos, la Molata de Las Negras, La Higueruela and Mesa de Roldan.These relieves were islands or high sea bottoms that Volcanic Dome were colonised by coral reefs and could be completely covered or surrounded by reefs. Calcareous corals that presently live in the tropics are In Mesa Roldán, 6 million years ago, a coral reef fringed the constructors of reefs. and covered a volcanic dome (dark tone).

42 Evaporites and Carbonates After the Recovery of the Mediterranean

Juan C. Braga - José M. Martín

In certain sectors of Cabo de Gata such as

La Molata de las Negras, Mesa Roldan and Field view of Field view of others, above the last reefal episode an gypsum banks. stromatolites erosion surface is observed that affects features, with their typical the reef and removes the greater part of its laminar deposits.This erosion surface is the structure. expression of Messinian desiccation in this part of the Mediterranean, known as the Salinity Crisis.

Its age is approximately 5.5 million years Following deposition of the gypsum, both above this level and on top of the erosion surface (Terminal Messinian). In effect, around this that reached the reefs, a sedimentary deposit formed fundamentally by carbonates with time the Mediterranean dried-up, by closing stromatolites and oolites can be identified. the communication between the Atlantic and the Mediterranean, therefore removing The oolites are particularly spherical, with an internal structure of concentric calcium carbonate the entry of water from the former. During layers. this period, the reefs around the border remained exposed to erosion, and in the central sectors, as much in the main marine basin, the SEDIMENTARY INTERPRETATION FOR THE GYPSUM IN A MEDITERRANEAN CONTEXT Mediterranean, as in the small marginal basins that Coastal reef 5.9 Ma bp (5.5 Ma bp) communicated with it, like Erosion Sill Marginal Basin that of Sorbas or Almería, Desiccation Normal Salinity important massive deposits of Gypsum and Gypsum gypsum were formed. other evaporites Precipitation Situation prior to deposition of the evaporites, Deposition of evaporites in the centre of the Deposition of evaporites in the interior of with formation of reefs in the margins and Mediterranean while it is disconnected from the marginal basins as they are being invaded by muddy-marly sediments in the basin. Atlantic and dries out. the first pools of water in the process of Mediterranean reflooding.

43 RECENT EVOLUTION AND EMERGENCE OF THE BAY OF ALMERÍA

J. Baena - C. Zazo - J. L. Goy - C. J. Dabrio

The Bay of Almería and Andarax Valley, Campo de Níjar and area of Roquetas del Mar surrounding it, made up a large sedimentary basin during the Pliocene and Quaternary (since 5.2 million years ago), with material mostly deposited in a marine environment.

At the start of the Pliocene the sea occupied all of the present low-lying areas: in the west up

to the slope of the Sierra de Gádor, through Detail of a cemented sand beach. Remains Marine deposits of a pebble beach covered Detail of a cemented pebble the Andarax Valley reaching up to the location of a typical tropical marine fauna by continental deposits with a calcareous beach. Retamar. of Rioja and bordering the Sierra Alhamilla, (Strombus bubonius) indicated by the crust above it. Retamar. pencil. Rambla de Amoladeras. penetrating across all of the Campo de Níjar where only the Sierra de Cabo de Gata and parts of the Serrata de Níjar were emerged. During the Quaternary, as a consequence of Deep marine The Andarax River, that presently discharges repeated climatic changes, alternating cold deposits in the Bay of Almería.Yellow into the sea close to Almería and in a north- glacial periods and warm interglacials, the sea muddy south direction, was located further to the level suffered strong variations that could have limestones, locally called Marls with northeast, between Rioja and Viator, during been in the order of 130 metres.These Leprosy. the Pliocene. variations were responsible for continuous changes in the position of the coastline, and for The high relieves that bordered the the distribution and abundance of the different sedimentary basin were traversed by ramblas marine and continental deposits. which, as at present, provided detrital material (blocks, pebbles, sand) to the marine basin. In the Bay of Almería a magnificent record of Shallow these distinctive sedimentary environments can marine During the Plio-Quaternary uplift in the region be observed, ranging from continental (alluvial carbonate was initiated, leading to the displacement of the fans, dune systems, etc.) to littoral and deposits. Whitish coastline in a southerly direction. transitional (submarine deltas in ramblas, calcarenites beaches, lagoons and littoral features, etc.). with fauna.

44 RECENT EVOLUTION AND EMERGENCE OF THE BAY OF ALMERÍA

EVOLUTION OF THE COASTLINE IN THE BAY OF ALMERÍA FROM THE PLIOCENE (5 MILLION YEARS AGO) UNTIL THE PRESENT

SIERRA ALHAMILLA SIERRA ALHAMILLA SIERRA ALHAMILLA SIERRA DE GÁDOR SIERRA DE GÁDOR SIERRA DE GÁDOR Ancient position Ancient Ancient position of Ancient Ancient of the Rio Andarax Coastline the Rio Andarax Ancient position of Coastline the Rio Andarax Coastline Modern position Modern position Modern position of the Rio Andarax of the Rio Andarax of the Rio Andarax

Almería Almería Almería

Airport Airport Airport

Modern Coastline Modern Modern Coastline Coastline

5,000,000 YEARS AGO 1,800,000 YEARS AGO 900,000 YEARS AGO

CONTINENTAL AREAS MARINE AREAS

Continental Interior Shallow Water Ancient Delta Ancient Coastline

Littoral Fringe Deep Water Modern Delta Modern Coastline

45 RECENT EVOLUTION AND EMERGENCE OF THE BAY OF ALMERÍA

ILLUSTRATIVE GEOLOGICAL PROFILES OF THE STRUCTURE OF THE SEDIMENTARY FILL IN THE BAY OF ALMERÍA

Sª Alhamilla

Níjar Pozo de los Frailes Sª Alhamilla Alquián Sea Level Sea Level

Sierra Alhamilla Níjar

Sierra de Gádor Quaternary Deposits (from 1.8 million years ago to Present) Campo de Níjar ALMERÍA El Alquián Upper Pliocene Deposits a at G (from 3 to 1.8 million years ago) Aguadulce de El Pozo de ra er los Frailes Lower Pliocene Deposits Bay of Almería Si (from 5.2 to 3 million years ago) Roquetas de Mar Miocene Deposits Cabo de Gata (from 23.7 to 5.2 million years ago) Mediterranean Sea Volcanic Terrain Punta del Sabinar (from 15,7 to 6,5 million years ago) Pre-Neogene Neogene Neogene and Substratum Volcanic Rocks Quaternary Basins Ancient Basement

Sª de Gádor Almería Basin Extension of Cabo de Gata Basin Pollux Bank Almería La Serrata Sea Level

46 The Almeria-Nijar Basin

Didactic Itinerary CABO DE GATA-NIJAR NATURAL PARK

1 1. Alluvial Dynamics of Ramblas: Las Amoladeras

A. Martín Penela

THE RAMBLAS Channels Bars

The Rambla de las Amoladeras is a superb example of alluvial systems in arid zones.These river courses, usually dry, represent channels in which currents of short duration can flow as a direct result of precipitation, scarcely receiving water from other sources.

A broad valley floor is exhibited, usually with a low sinuosity. The dynamics of this alluvial system are Its river bed is occupied by numerous interweaved channels fundamentally controlled by the climate and the and the bottom covered by sediments organised into bars shortage of vegetation. Seasonal rains, and channel deposits.Their sediments are mostly made up of frequently stormy and of short duration, create gravel-sized particles. an important surface torrent, with great erosive power, that supplies water and sediment to theses river beds.

The channels are very mobile, and develop as furrows that interweave amongst themselves, adjacent to the bars, that appear as small mounds, upon which vegetation is frequently established.The bars, of different form and size, change their arrangement and morphology after each flood.

0 10/100 m The floodplain represents a portion of the river bed that is only inundated during important floods. In it a great part of the fine materials that were transported Channels in suspension can be deposited, giving rise to deposits Bars that favour the development of fertile soils. Floodplain occupied by water only during the largest flood events

49 1. Alluvial Dynamics of Ramblas: Las Amoladeras

FLOODS PHASES IN A FLOOD

As a result of intense storms, the dry 1. DRY PERIOD 2. PERIOD OF STRONG FLOODS riverbeds in the ramblas can be transformed, in a short time, into violent torrents of water loaded with sludge and detritus. These very intensive floods, sudden and powerful, can be unduly catastrophic and cause great destruction in agricultural zones and to built structures, in the river beds of the ramblas or within the same floodplain. The large floods take place sporadically, tied to seasonal changes or times of rain. 3. PERIOD OF DIMINISHING FLOW 4. PERIOD OF SCARCE ACTIVITY

Damage caused by a flood .

50 1. Alluvial Dynamics of Ramblas: Las Amoladeras

ALLUVIAL TERRACES STAGES IN THE FORMATION OF A SYSTEM OF TERRACES

Alluvial terraces are deposits positioned 1 sporadically along the side of a valley that correspond to non-eroded segments of Stage of alluvial infilling.The earlier alluvial sediments. When a current deposits most of the rejuvenation of the alluvial system is sediments that it transports produced by climatic, tectonic or other and produces a river fill. changes, water currents deeply erode the sediments within their channel, giving rise to a new river course in a lower A change in base level topographic position with respect to the 2 means that the rambla older channel. Alluvial Terrace in the Rambla de Amoladeras. 1st Terrace evolves in order to reach a state of equilibrium. On top of the previously formed deposits a new channel is emplaced which erodes the pre- existing alluvium that had come to construct the older terrace level. Older Terraces

Flood-susceptible river bed 3 1st Terrace Channel Bars 2nd Terrace

If the conditions repeat Substratum themselves, they will be succeeded by new phases of filling and erosion from which various terrace levels will originate. 51 2. Fossil Beaches of the Rambla de Las Almoladeras

C. Zazo - J. L. Goy - C. J. Dabrio - J. Baena

The surrounding area of the Rambla de las beach, of unknown age, which contains the Amoladeras are characterised by the presence remains of a fossil fauna like that which actually of one of the most complete geological records lives in our coasts. of fossil Quaternary beaches, and with the best conditions for observation, in the Spanish This beach is separated from those which follow coastal zone.These marine beaches, that it by a deposit of cemented sand that fundamentally developed between the last corresponds to a fossil dune field, that formed 200,000 years and the present day, were when the sea descended, leaving the beach partially covered on the surface by a dune deposits emerged and dried out, such that it system that started to form around 2500 years allowed the wind to accumulate sand. ago. In the talus of the right hand margin of the The following deposits (B, C and D) consist of river mouth of the rambla, a mixture of deposits cemented conglomerates rich in Strombus consisting of well-cemented sands and pebbles bubonius.The separation between the distinct with a marine fauna can be seen, that represent beaches consists of erosive surfaces, generated ancient beaches, and consequently, the position during falling sea level in the coldest periods. of the coast at that time. Average absolute dating (Uranium-Thorium), has obtained ages of 180,000 years, 128-130,000 years and 95-100,000 years for the three differentiated beach levels. All of the beaches contain fossils of Strombus bubonius.They dominate Tyrrhenian beaches, a name that is derived from the Tyrrhenian Sea, for it was there that beaches with this characteristic fauna were described for the first time.

An interpretation of the geometry of the outcrop allows differentiation of, from left to right: in the first place some conglomeratic sediments (A) corresponding to the oldest

52 2. Fossil Beaches of the Rambla de Las Almoladeras

Surge Beach Level Fault Plane Channels/Grooves or Wall

Fosil dune ACTUAL SECTION

Fault planes Well Modern Beach

Sea Level Modern Dunes Rambla Amoladeras

INTERPRETED SECTION

SO NE

Modern Beach Dunes D Sea Level A C B 95.000 years 128.000 years 180.000 years >250.000 years

Each position of the coastline has left behind an associated fossil beach level. In the river mouth outcrop of the Rambla de las Almoladeras, four superimposed fossil beach levels can be observed with ages of more than 250000, 180000, 128000 and 95000 years, respectively.The latter three levels contain the remains of a marine mollusc (Strombus bubonius), that still persists in modern tropical coasts, so that a warm, almost tropical, climatic character existed in the coast during these stages.

53 2. Fossil Beaches of the Rambla de Las Almoladeras

The fossil beaches of the littoral zone in MODERN AND ANCIENT GEOGRAPHIC 0 1000km DISTRIBUTION OF STROMBUS BUBONIUS Almería contain abundant fossils of marine IBERIA species that do not inhabit theses coasts at Present times, although they had populated Canary Mediterranean Sea the littoral zone between 180,000 and 70,000 Islands years ago. Strombus bubonius is, amongst

others, a fossil of special importance.This has Tropic of Cancer become used as an excellent palaeoecological indicator, in that it reveals variations in salinity and water temperature of the sea with great River Niger sensitivity. Its presence in these fossil beaches Lake Chad

tells us that the sea which bathed the Almería Nile River coastline was at other times warmer, Atlantic Ocean Atlantic possessing subtropical conditions. ÁFRICA Gulf of Guinea Equator Strombus bubonius is a marine mollusc Gastropod, typical of warm seas, originating S.bubonius,(modern) S. bubonius, (fóssil) Cold Canary Current from the African equatorial Atlantic, entering into the Mediterranean through the Straits of Gibraltar when the atmospheric and surface water temperature of the sea are a few degrees higher than they are at present. During the last glaciation, between 65000 and 10000 years ago, oceanic waters cooled, so that they prompted a new migration of this species towards the African equator, in whose coastline they are found living today, actually forming part of the diet of townsfolk in this Details of the shape of Strombus bubonius from fossil beach Dorsal and Ventral views of an example of Strombus bubonius. littoral zone. levels,above which the modern littoral boundary is positioned.

54 3. The Dune System in the River Mouth of Rambla Morales

C. Dabrio - J. L. Goy - J. Baena - C. Zazo

The dune systems that are observed in the The variation in sea level occurring in this coast surroundings of the river mouth of the Rambla throughout the Pleistocene-Holocene has given Morales are produced by the action of westerly rise to various phases of dune formation. winds, that lift up sand from the beaches and The oldest dunes are cemented, the most recent transport it towards the river bed, accumulating may be: semi-mobile, covered over by it around small bushes or topographic vegetation, or mobile, which are those that irregularities in the surface. In this way dune finally bury the earlier ones, in their advance construction is initiated. towards the land.

FORMATION AND DEGRADATION OF THE DUNE SYSTEMS OF CABO DE GATA

A B C Westerly Winds 2nd active beach episode Active beach Strombus bubonius Sea level Sea level 1 1 1 1 1 1 1 2 1 Fossil Pleistocene dunes Primary dune system Holocene active beach Strombus bubonius Fossil Pleistocene beaches A slight fall of sea level leaves the beach, slightly more A new rise in sea level deposits another beach episode (2) extended, under the effects of erosion by westerly winds, that On top of the fossil beaches and dunes, the first active beach above the previous erosional surface. Dunes continue carry along the finest elements (sand) in the form of a train of of Holocene (less than 10,000 years old) is deposited (1). advancing. dunes (primary system).

D E

2 112 Modern active beach Finally the last rapid rise in sea level 1 2 2 1 emplaces the modern beach (3).The dunes advance, but they have been disappearing Second dune system due to intensive quarrying of sand in order Another rapid fall in sea level causes a repetition of the same 3 2 to cover pastural land with sand. phenomenon which forms a new train of dunes (2nd system), that Exploitation of these dune systems is advances mixing with the previous one. actually completely prohibited. 55 4. The Lagoon of Rambla Morales

C. Dabrio - J. L. Goy - J. Baena - C. Zazo

In the river mouth of Rambla Molares a small lagoon, with an almost permanent character, has been created. Its origin stems from interaction between the rambla system itself with the beach. During two times of the year (end of spring - start of autumn) the phenomenon called gota fría is registered in the Mediterranean coast, that comprises intense and torrential rains concentrated in periods of very short time (several days). During these periods the ramblas transport a great quantity of water and sediment, that is finally to be deposited in the sea, eroded from the beaches that previously closed off the river mouth, River Mouth of showing a great capacity for cleaning out the the Rambla de Morales rambla (high energy stage). Lagoon Closing barrier of the river mouth Aerial view of the river mouth of Rambla Morales. These sediments are redistributed along the length of the coastline, during periods of good weather (low energy stage), by means of littoral currents or drift currents, that in the case of the Rambla Morales circulate in a southeasterly direction, regenerating beaches and barriers once more. As these beaches are topographically higher than the bottom of the rambla, towards the land they leave a small depression that fills up with View of the lagoon from the river mouth of the Rambla Morales. It can be observed how the present, water from scarce rainfall that accumulates during topographically higher, littoral barrier causes a closing inter-storm periods.This water, not having the of the rambla, such that it impedes its normal drainage into the sea.This situation persists up until when, in strength of movement, remains stagnant creating Aspect of the modern beach that forms part of the a state of high energy, the rambla breaks through the a lagoon in the river mouth of the rambla. littoral fringe which closes off the inlet of the rambla. littoral barrier nourishing the sea with sediments.

56 4. The Lagoon of Rambla Morales

SIMPLIFIED SCHEME OF LAGOON FORMATION PROCESSES IN THE RIVER MOUTH OF THE RAMBLA MORALES

1. HIGH ENERGY STAGE 2. LOW ENERGY STAGE 3. NEW STAGE OF HIGH ENERGY

Littoral Barrier (Beach-Dunes) Ancient littoral barrier New littoral barrier

Lagoon Temporary lagoon deposits

Sediments Sediments Sediments Rambla Morales Bars

Littoral Littoral Littoral drift drift drift

Rambla Lagoon Rambla

57 5. The Salt Pans (Salinas) of Cabo de Gata

J. L. Goy - C. J. Dabrio - J. Baena - C. Zazo

THE NATURAL ALBUFERA beaches that wash over the barrier beach and mud carried by the wind have less importance. The modern salt pans (salinas) of Cabo de Gata constitute a magnificent example of an Evaporation, controlled primarily by direct 'albufera' or backshore lagoon system set up as sunshine and by the wind, plays a very notable a Mediterranean salt pan by man.This type of part in the dynamics of these lagoons, system is natural, and is generated thanks to a contributing effectively to their desiccation, depressed area at the back of the coastline, which is why they can be a suitable mechanism where freshwater accumulates. It is for the manufacture of salt. permanently separated from the sea by a beach-barrier, forming mainly from sandy sediments carried by the ramblas and IDEALIZED GEOMORPHOLOGICAL SKETCH OF THE SALINAS displaced along the length of the coastline by Lagoon Active alluvial fans littoral drift.

The lagoons receive hydrological supplies from rainwater, from rivers that discharge into Sierra them and, on occasions, from subterranean aquifers and from Lagoon Border the sea itself. Bahada Alluvial Fan The lagoon tends to fill with River Evaporation sediments from diverse Floodplain Cabo de Gata Lagoon Barrier Beach Ram sources.The most bla important are provided by Oleaje the alluvial apparatus Laguna Sierra de Gata that drain the Wind Littoral Drift Aerial view of the active alluvial fan systems that surrounding relieves of originate from the Sierra de Cabo de Gata relief. In Beach the sierras. Sandy many cases they behave as coalescing fans, in that they are laterally connected and superimposed one sediments from the Waves upon another.

58 5. The Salt Pans (Salinas) of Cabo de Gata

IDEALIZED GEOMORPHOLOGICAL SKETCH OF THE SALINAS A schematic section of the lagoon showing the diverse dynamic and morphological elements.

Atmospheric Dust The deposits of the lagoon (E) connect with those of the alluvial fans (A) and Alluvial Fans origina- ting from the with those of the backshore part of the surrounding Relieves Rain beach (B) that obtains sediments carried during large storms when Currents Evaporation swells can spill over the barrier beach. Transfer of Water and Sediment A Fine Sediments and B Some Precipitates The model is only active, as at present, Sea during the periods which high sea level D C E is maintained that coincide with interglacials. On the other hand, during Infiltration glaciation the sea level had remained Groundwater Depressed Area lower, placing the beach towards the Erosion Surface formed Older Lithified and Present Barrier south. In these periods the zone could during periods of Low Sea Level Cemented Barrier remain subjected to the erosive action Reworked Littoral Fringe of external agents (wind, currents, etc.), forming an erosive surface (C).

Fan Cones Sierra de Cabo de When the lagoon and the littoral fringe Gata (strandplain) are active, during Littoral Fringe Alluvial Fan interglacial periods, the beach grows System Beach Salt Pans Albufera Lagoon (progrades) towards the sea (D) and a thick covering of sediments accumulates in the lagoon (E).

View of the salinas from the south.

59 5. The Salt Pans (Salinas) of Cabo de Gata

WORKINGS OF A MARITIME SALT PAN SALINISATION PROCESS

The natural lagoon systems like that of Cabo de Evaporation Concentrates Gata have historically been utilised by man in Precipitates the extraction of salt: these are the characteristic maritime Mediterranean salt pans. Basically this consists of taking water from the A B C D sea in a controlled process of evaporation, by which means a progressive increase in salinity is produced, until a stage of saturation and Pump 36 g/l 80 g/l 140 g/l 350 g/l 325 g/l 370 g/l or (Salinity in grams per litre) precipitation of common salts (halite, NaCl) is basin reached. Sea Brine Mg Cl2 In each a circuit that consists of several concentration pools (A, B, C) of broad extent and Floating salt little depth is established, fed directly by water (halite) layers formed in the from the sea with a salinity of 36 grams per litre. A B absence of The seawater is introduced by a channel to C wind. the first concentration pools (A), in which the D marine macrofauna is retained (fish, gastropods,…) and a settling of (terrigenous) material from suspension is produced. Precipitation of calcium-magnesium carbonates Aerial view of the salt pans from the east.The letters correspond (upon increasing salinity from 36 to 140 grams to the identification of different areas of the salt pans referred per litre) and the elimination of micro- to in the text. organisms (algae, bacteria,…) occurs in the marine water upon achieving an intermediate of calcium sulphate (upon reaching a salinity (D) where the precipitation of common salt concentration (B). After this initial phase, of 140 to 325 grams per litre). Once these (at 325-370 grams per litre) occurs, extracted for the water follows its path through different undesirable products have been taken out of storage, purification and finally sale. concentrations (C), favouring the precipitation solution, the brine goes through crystallisation

60 6. Volcanic domes of Punta Baja, El Faro and Vela Blanca

Juan M. Fernández

THE VOLCANIC SERIES ◗ The Vela Blanca dome cuts across the tuffs and might have formed simultaneously with the The coast in the vicinity of the Cabo de Gata previously mentioned lava flows. It is highly lighthouse shows an excellent outcrop of massive altered and impregnated with manganese volcanic rocks that form the structure of a oxides, which give it a very dark coloration volcanic feature known as domes.Their age (Punta Negra). of formation is greater than 12 million years. ◗ Above the flows, another level of pyroclastic They are surrounded by a complex sequence of rocks appears that extends several kilometres pyroclastic rocks and lava flows, of varying towards the north. composition, that have been affected by ◗ The highest peak (Bujo, 374 m) corresponds to an hydrothermal alteration. andesitic dome that cuts through the previous sequence. Similar domes are recognised at Climbing up the vela Blanca hill gives an overview different points in the southern massif of Cabo de of the volcanic rock succession that exists in the Gata. southern end of the Sierra de Cabo de Gata.: Bujo (373 m) ◗ Surrounding the Punta Baja-Cabo de Gata Dykes Andesitic pyroclastic levels Lava flows domes, white-coloured rocks known as tuffs Cerro de vela blanca (213 m) can be recognised.They have a pyroclastic Faults origin (ignimbrites), that is to say, they are Grey tuffs produced by highly explosive eruptions. Vela Blanca Dome Punta negra These are the oldest rocks in the area. Alluvium White tuffs ◗ Above them, other levels of greyish-coloured Cala Rajá tuffs are developed, also pyroclastic in character. Finger reef ◗ On top of this andesitic lava flows (rock of Punta Baja Dome intermediaate character) can be recognised. They form a well-defined promontory, that is White tuffs (pyroclastic rocks, ignimbites) Grey tuffs (pyroclastic rocks, ignimbites) repeated on the slope through the influence of various faults. At a distance, columnar Massive amphibolitic andesites (domes) Massive amphibolitic andesites (flows, dykes and domes) jointing can be recognised. Pyroclastic rocks (pyroxene andesites) Recent alluvial deposits

61 6. Volcanic domes of Punta Baja, El Faro and Vela Blanca

VOLCANIC STRUCTURES of these hexagonal columns of rock, means that generated towards the margins of the domes, they have been utilised, in this and many other and includes folds that can be formed during The dome complex of Punta Baja-El Faro-Vela place in the Sierra de Cabo de Gata, for the extrusion.The colour bands indicate slight Blanca comprises several massive lava bodies obtaining paving slabs. differences in the composition of the lava during aligned in an east-west direction, probably extrusion, whilst the flow lamination is produced exploiting a fracture in this orientation as they Other structures observed in these rocks are by resistance to flow of viscous lava around the are extruded. lamination and flow banding.This is mostly margins of the dome.

Domes are volcanic features that originated when viscous lava, rich in silica, flowed slowly onto the surface, and accumulated around, CRYPTODOME AND ASSOCIATED STRUCTURES solidified and plugged its own exit point. At times the lava does not manage to exit onto the surface, and forms an accumulation beneath Partial emergence Breccia (Mónsul type) the intruded rocks, that is called a 'cryptodome'. Columnar jointing

The complex in this area contains two principal Colour bands domes, one beneath the lighthouse and the other at Punta Baja, in both of which a spectacular series of characteristic volcanic structures may be recognised:

The most pronounced is columnar jointing, typical of massive rocks. It is produced through Marginal lamination the slow cooling of lava after its emplacement. Country rock (white tuffs) Upon cooling the volume of lava diminishes slightly, and this contraction is accommodated by the formation of regularly-spaced joints, in a perpendicular arrangement with respect to the Nucleus cooling surface of the lava.The peculiar shape

62 6. Volcanic domes of Punta Baja, El Faro and Vela Blanca

White tuff at Cala Rajá, pyroclastic material (ignimbrite) in which the domes of Punta Columnar jointing in the Punta Baja dome. Baja, El Faro and Vela Blanca are enclosed.

Fanning of Columnar joints in Punta Baja, traditionally used for the extraction of Flow lamination on the margin of the El Faro dome in Cabo de Gata. decorative paving blocks.

63 7. The Mónsul volcanoes

Juan M. Fernández

THE MONSUL SUBMARINE VOLCANOES In the panorama in front, the feeder zone of the volcano can be distinguished. It consists The steep volcanic cliffs surrounding the area of darker, andesitic lavas, and exhibits a very of Mónsul consist of volcanic agglomerates characteristic structure known as columnar (or breccias).They are a type of rock formed from jointing. These structures are produced due to angular blocks of (andesitic) volcanic rock, with the contraction of lava upon cooling. a diameter that ranges from millimetres to metres, enclosed within a fine, sand-sized matrix, also of volcanic origin.

This material takes its origin from submarine eruptions produced around 10 to 12 million INTERPRETATION OF THE OBSERVED PANORAMA years ago, from submerged volcanoes.The La Media volcanoes were located next to one another, in Luna inlet a manner in which, once an explosion had Mónsul inlet occurred, the erupted material was deposited in stacked layers on the marine seafloor. Dunefield Beach Parking

Agglomerates or volcanic Andesitic lavas with Beaches and Dunes Debris breccias columnar jointing RECONSTRUCTION OF GENETIC PROCESSES

Sea level during the eruption

Feeding zone of the volcano

64 8. The ‘barchan’ dunefield of Barronal or Mónsul

C. Dabrio - J. Baena - J. L. Goy - C. Zazo

Wind carries out two fundamental processes, plan view, are: barchans, or half-moon dunes, with erosion and accumulation, which create certain their corners or points facing in the same morphological features; dunes are amongst these. direction as the wind; parabolic dunes, with the The term 'dune' is used in a broad sense to corners (horns) facing in the opposite direction designate the majority of accumulation features, of to the wind; linear (seif) dunes, produced when sand deposits. a flat zone, with sandy material covering its floor, exists close to a relief orientated almost In the dunefields of the Almería littoral zone the perpendicular to the dominant wind direction. dominant types, according to their morphology in

TYPES OF DUNES IN CABO DE GATA

PARABOLIC DUNES BARCHAN DUNES Wind

Crest Vegetation Leeward face Wind Depression Wind Windward face

Lunite Corner (horn) Mónsul barchan dunefield. 1. Accumulation of sand 2. Migration of the Barchan and due to vegetation increase in size Wind

LINEAR (SEIF) DUNES DUNES ACCUMULATING DUE TO VEGETATION

Wind Wind Dune Movement of sand in favour of the wind direction in the Mónsul dunefield.

Volcanic substratum Wind

65 9. The Los Frailes Volcano

Juan M. Fernández

The Los Frailes hill (473 m), is one of the most LOWER UNIT: distinctive elements of the volcanic Complex. AMPHIBOLITIC ANDESITES It consists of two readily distinguishable units a lower unit of amphibolitic andesites and an The lower unit of Los Frailes constitutes the upper unit of dark basaltic andesites, that collapsed floor of a magma chamber that was correspond to the two main summits (El Fraile vacated during an individual or several very and the more recent El Fraile Chico). Both of the intense eruptions. In these eruptions a great Los Frailes rest upon andesites, strongly altered volume of magmatic material left the surface by hydrothermal processes, that make up the through rapid and very explosive phenomena, southern volcanic massif of Cabo de Gata. and the roof of the magma chamber collapsed giving rise to a chaotic mixture of rock fragments, associated with dome remains and lava flows, that constitute the most common between the units of chaotic breccias. In material in this lower unit.The explosive intervals numerous places layers of sedimentary rocks are are marked by intervals of pyroclastic rock (tuffs) found in addition, pertaining to beach and of different types, that are found intercalated shallow marine environments, rich in fossils;

GEOLOGICAL PANORAMA OF THE LOS FRAILES VOLCANO FROM THE LA ISLETA VIEW POINT

SW Summit domes NE El Fraile Chico El Fraile (493 m) Sacristán Cerro de Morrón de Mateo BASALTIC ANDESITES Sedimentary levels caves Santa Cruz Bentonite quarries DACITES

AMPHIBOLITIC ANDESITES San Felipe ALLUVIAL FANS castle Rambla LA ISLETA DOMES Fossil beach of Los Escullos SEDIMENTARY UNIT

66 9. The Los Frailes Volcano

these are intercalated within the volcanic rocks They are relatively well preserved rocks, without Other eruption phases gave rise to abundant of the lower unit, and are very abundant alteration, whose age is estimated at 8.5-8.6 agglomerates or pyroclastic breccias, in between the lower and upper units.The age of million years.They are also situated above eruptions somewhat more explosive.The end of the lower unit is believed to be between 10.8 sediments rich in fossils from the Tortonian, magmatic activity is marked by the extrusion and 12.4 million years by some authors, and belonging to shallow marine environments, and of the domes that constitute the two around 14.4 million years by others. beach sediments.This data indicates that this previously-mentioned pinnacles (summit upper unit of Los Frailes constituted a volcanic domes), that sealed the eruption vents. Erosion UPPER UNIT: island during its formation 8 million years ago. has been intense up until now, although the BASALTIC ANDESITES greater relative resistance of the massive lava The unit is built from two main emission centres, domes has configured a roughly conical erosive The summit of Los Frailes is composed of a unit that discharged several massive lava flows morphology for this unit. of basaltic andesites.These rocks are the most (at around 1000º C temperature), whose basic (poor in silica) in Cabo de Gata, although characteristic columnar jointing has been utilised with properties that did not reach the point of for the quarrying of paving stones (several hills being basalts. can be seen in the middle of the slope).

INTERPRETED GEOLOGICAL PANORAMA OF THE LOS FRAILES VOLCANO FROM THE LA ISLETA VIEW POINT

SW NE RELLLANA de El Fraile Rodalquilar BASALTIC ANDESITES (8 M.A.) SUMMIT DOMES IGNIMBRITES OF THE San Cerro de LAVA FLOWS RODALQUILAR CALDERA José Enmedio SEDIMENTARY LEVELS VOLCANO-SEDIMENTARY UNIT

OLD AGGLOMERATES AMPHIBOLITIC ANDESITES (ANDESITES) (12-10 M.A.) MASSIVE ANDESITES

67 10. The fossil dunefield of Los Escullos

C. Zazo - J. L. Goy - J. Baena - C. Dabrio

In the Almerían littoral zone there have been by the wind, formed in a warmer environment three important phases dune system than at present.This is knowwn through the development during the Quaternary: greyish existence of an associated fauna (Strombus cemented dunes, formed of the fragments of bubonius)that belongs to warm seas, and by the schists, volcanic rocks, and quartz grains, such as ooliths themselves.Through the microscope it those that are observed in Rambla Amoladeras, can be observed that the ooliths are composed and which formed at a time known to be of a nucleus of quartz grains or rock fragments between 250,000 and 180,000 years ago; white- or faecal pellets and a coretex that shows coloured oolitic dunes, consisting of rounded concentric layers of aragonite. Oolites actually grains known as oolites, around 128,000 to form in the infralittoral zone, at a few metres 100,000 years old (last interglacial period); and depth, on the seafloor of warm waters that are finally, greyish, uncemented dunes , that illustrate saturated in carbonate and highly agitated by the same coloration and composition as the first, waves. although in this case they were not cemented, formed from around 6,000 years ago to the Present.

In the Los Escullos cove, beneath the San Felipe San Felipe castle of los Escullos castle, we can observe, without doubt, the best Isleta del Moro exposure corresponding to white, oolitic dunes in the Natural Park. However, other exposures exist in the Rodalquilar and Los Genoveses beaches.

These ancient dune systems are excellent indicators, not only of the position of the Oolitic coastline at the time of its formation, but of the dunefield ecological and environmental conditions. The San Felipe castle of Los Escullos sits on top of a In the Cabo de Gata Natural Park area, fossil oolitic In effect, the oolitic dunes were generated due spectacular fossil oolitic dunefield.Without doubt the best dunefields exist in other places: here the exposures of Los to the movement of old oolitic beach sediments record of this type of deposit in the area of the Natural Park. Genoveses may be observed.

68 10. The fossil dunefield of Los Escullos

OOLITIC DUNES OF LOS ESCULLOS

Los Frailes Los Escullos Oolitic dunes Sea

DETAIL OF THE OUTCROP A Ooliths B

Dirección de paleovientos

INTERNAL STRUCTURE OF THE DUNES

Microscopic view (thin section) of the components of dune oolites from Los Escullos (Photo A). Upon increasing the resolution (Photo B) the ooliths can be identified perfectly as the spherical structures that stand out within the sandy matrix.

69 11. Alluvial fans of the La Isleta-Los Escullos coastal plain

J. L. Goy - C. Zazo - C. Dabrio - J. Baena

The Sierra de Cabo de Gata exhibits an abrupt the depression, provokes a fall in their capacity to relief, with strong slopes, that contrasts with the transport and the consequent accumulation gentle morphology of the littoral depressions (deposition) of the sediments (blocks, pebbles, (coastal plains).The abrupt change of slope that silts, etc.) which they moved towards the most is produced in the courses of small barrancos as low-lying areas. An open alluvial fan in thus they exit from the mountain relieves, and enter formed.

SIMPLIFIED GEOLOGICAL SCHEME OF THE QUATERNARY DEPOSITS IN THE LA ISLETA-LOS ESCULLOS AREA

Fluvial deposits Slope deposits Littoral deposits

Alluvial fan Channel deposits of Gravity deposits Marine deposits Aeolian deposits terraces and rivers deposits

Phase 6 (c) Present river Colluvium and Beach undifferenciated slope deposits

Holocene Phase 6 (b) Littoral barrier

Phase 6 (a)

2nd Terrace Aeolian dunes

Phase 5 1st Terrace Quaternary Phase 4

Phase 3 Pleistocene

Phase 2 Abandoned river Phase 1

Miocene Volcanic rocks

70 11. Alluvial fans of the La Isleta-Los Escullos coastal plain

A fall in sea level, linked to the slow uplift of PROCESSES OF DEPOSITION AND INCISION IN ALLUVIAL FANS the relief, caused incision of the initial barranco (primary river course) in the OPEN FAN INCISION deposits of the older open fan, upon whose surface soils were already able to develop. Sierra de Cabo de Gata Sierra de Cabo de Gata

Paleosuelo The formation of subsequent fans, during the initiation of a new rise in sea level, gives way to incised fans at a lower altitude to the previous one.

Sea level Sea level In the area of La Isleta-los Escullos, several Slow uplift incised surfaces (roofs of fans), inclined Fan formation phase 1 gently towards the sea are observed, that Fan formation phase 2 represent distinct phases of fan formation throughout the Quaternary.Theses are due to changes in the climatic conditions, tectonics and eustacy (oscillations of sea level), and their study provides very interesting information about such conditions.:

Los Escullos La Isleta Aerial view of La Isleta-Los Escullos in which phase 2 alluvial fans may be observed, with a schematic overlay.

71 11. Alluvial fans of the La Isleta-Los Escullos coastal plain

PANORAMA FROM THE LA ISLETA VIEWING POINT AND INTERPRETATION OF THE ALLUVIAL FAN SYSTEM

Cerro de Los Filabres Alluvial fan entrenchment Phase 1 Phase 2 Phase 3 alluvial fan Los Escullos alluvial fan alluvial fan

Beaches Oolitic dunes LA ISLETA VIEWING POINT

Undifferentiated slope deposits Beaches Phase 1 alluvial fans Phase 3 alluvial fans

Volcanic rocks Fossil oolitic dunes Phase 2 alluvial fans

72 12. Rodalquilar volcanic calderas

Juan M. Fernández

One of the most significant volcanic structures rapidly vacated and its roof collapses, leaving of the Cabo de Gata Volcanic Complex are the behind a roughly circular depression. Rodalquilar calderas, from the centre of which known gold deposits are located. Rodalquilar shows the superposition or nesting of two successive calderas; the larger is the Rodalquilar caldera, and inside it the La Lomilla caldera is located (thus named after La Lomilla de Las Palas).Theses calderas are collapse structures produced by highly explosive eruptions, that gave place to tow large units of pyroclastic rock, known as the Cinto ignimbrites and the Lázaras Ignimbrites, Detail of the Cinto respectively. Calderas are collapse features that pumice flows.The dark stippled area are produced when, during an explosion of corresponds to large great magnitude, the magma chamber is very quartz crystals.

INTERPRETED GEOLOGICAL SKETCH OF THE RODALQUILAR VOLCANIC CALDERA

SE Caldera de Rodalquilar NW Caldera de la Lomilla Mines La Rellana Lázaras ignimbrite 600 La Isleta Cerro del Cinto 400 200 Sea level Domes of the Pre-caldera -200 caldera margin rocks -400 -600 -800 m Detail of the Cinto collapse breccias. Concentration of (dark) blocks within a pumice flow (light- Collapse breccias Altered andesitic Cinto ignimbrite Unaltered andesitic intrusions coloured). intrusions 73 12. Rodalquilar volcanic calderas

GEOLOGICAL HISTORY The system of fractures generated during Thin layers of sedimentary and volcanic rocks the collapse were later infilled through the were deposited on top of the planar surface of The Rodalqular Caldera and the Cinto development of a hydrothermal system and by the Lázaras Ignimbrite. Ignimbrite mineral deposits. The Rodalquilar Caldera is the larger, with a 4km FORMATION OF THE MAGMATIC CHAMBER by 8km width and an oval shape. Its origin is related to the thick pyroclastic unit of the Cinto Pre-caldera volcano Ignimbrite, which formed 11 million years ago, on top of a mass of older mass of andesitic flows (A), due to collapse of the magmatic chamber. Pre-caldera andesites

B. FORMATION OF THE RODALQUILAR CALDERA Magma chamber Since the collapse of the Rodalquilar Caldera and formation of the Cinto Ignimbrite (B), the Rodalquilar Caldera magmatic chamber refilled itself, and the ignimbrites filling the caldera bulged outwards, Cinto Ignimbrite making way for the present Cerro del Cinto Filling of the caldera (a resurgent dome). This phenomenon is very common during caldera formation processes, Collapse and is called resurgence (C). breccias C. RESURGENCE La Lomilla Caldera and the Lázaras Ignimbrite A new episode of intense eruptive activity gives Ring Resurgent dome way to the formation of the Lázaras Ignimbrite, dome simultaneously with the collapse of the La Lomilla Caldera 9D). this caldera is 2 km in diameter and is nestled in the Rodalquilar Caldera. Resurgence

74 12. Rodalquilar volcanic calderas

Resurgence and hydrothermal systems The end of magmatic activity in Rodalquilar is marked by the emission of a series of flows and the extrusion of andesite on the surface, and the formation D. FORMATION OF THE LA LOMILLA CALDERA of an intrusion just underneath the La Lomilla Caldera Rodalquilar calderas.This new phase of resurgence of the magmatic system is Lázaras Ignimbrite Sediments accompanied by a doming of the pile of Domes formed on the ring-like margin of the caldera. volcanic material, the opening of fractures and the development of the hydrothermal system, which produced alteration of the rocks and the formation of mineral deposits.The age is younger than 9 million years. In this phase a series of very extensive fractures formed with a north- south orientation, that were partly infilled through mineralization. The Lázaras Ignimbrite corresponds to a tuff formed from pumice fragments (dark colours) in a matrix of RESURGENCE AND FORMATION OF THE HYDROTHERMAL SYSTEM Finally, all of the associated volcanic fine ash (light colours). deposits were covered by marine Reef complex Hydrothermal system Andesites carbonate sediments at the end of the Miocene (latest Tortonian and Messinian), Contact forming the features of La Molata, Romeral, Molatilla, etc.

Intrusion

Resurgence

La Molata carbonates on top of the ignimbrites of the Rodalquilar caldera.

75 13. Mining and metallurgical processes in Rodalquilar

Carlos Feixas

MINING IN RODALQUILAR

Exploitation of gold in Rodalquilar has been carried out by means of two very different methods, such that it relates to extraction as much as to the retrieval of precious metal.

Mining in the 19th century and at the start of the 20th century, was carried out by internal exploitation of high-grade quartz veins through means of shafts and galleries. On the other hand, mining took a new path from 1956 through the National Company ADARO, characterised by combined exploitation; interior workings with high grade material (over 5 g/ton), and cutting or quarries on the outside, with lower grade material (1 to 1.5 g/ton)> the mixture of these products allowed intermediate grades of 3 g/ton to be obtained, optimal for the type of extraction plant that was working it.

In the last decades of the 19th century and the Opening of the track that connected the Cerro del Cinto mine workings with the grading and concentration plant. Mine entrance of 'Lode 340' during the period of maximum start of the 20th century, the recovery of gold This infrastructure already meant an enormous advance activity in the mining district of Rodalquilar.The was carried out through means of smelting that opened up the possibility of mechanising the quarrying photograph is taken roughly in the 50's decade (Photo, furnaces obtaining a lead blende rich in system (Photo, Evaristo Gil Picón). Evaristo Gil Picón). gold and silver. In the second half of the 20th century, recovery was carried out through the operation of electric furnaces, after concentrating by means of washing with cyanide solutions.

76 13. Mining and metallurgical processes in Rodalquilar

QUARRYING METHODS Spoil rock

Mineralization The extraction workings in the interior are achieved by following the auriferous lodes and exploiting raised chambers (A); the materials C was removed by shafts and A galleries (B).The outside workings were carried out on small, terraced,

quarry benches (C).The minerals B D obtained in this way were mixed and piled up ready for transport to the treatment plant (D).

Cerro del Cinto quarry cuttings completed by ADARO in order to supply the treatment plant.

The darker structures correspond to the richest lodes (Photo, Juan M. Fernández).

77 13. Mining and metallurgical processes in Rodalquilar

METALLURGICAL METHODS 16) in order to activate gold precipitation in the means of zinc dust, with zinc content of following reaction: between 10 and 40%; it is put through an

The quarried mineral was mixed in a storage 2 NaAu(CN)2 + Zn ---> Na2Zn(CN)4 + 2Au. electric heater for drying, where the last traces shed (1), and afterwards subjected to initial This process is known as “Merril Crowe”. of humidity are removed.The dry product is crushing in a grinding machine (2), and secondly precipitated by acid washing and the precipitate in a mill (3). Later it was classified in vibrating The precipitate in the tanks comes from a is removed through filtration.The gold is sieves (4 and 5).This product was submitted to process of retrieval through precipitation by obtained by fusion in an electric furnace. electromagnetic separation (6), in order to eliminate metals other than gold. Afterwards it was milled in ball mills (7).The remains were classified in pressure washers (8) in order to OPERATIONAL RECONSTRUCTION ACCORDING TO THE METALLURGICAL PROCESSES IN THE ACTUAL separate the fines, without gold, and return the INSTALLATIONS OF RODALQUILAR pieces with gold to the mills for grinding. The minerals concentrated in this way were mixed in

two heavy tanks (9) with a solution of cyanide 1 (10) in order to subject it to the following 5 6 chemical reaction in a medium with pH 9 to 11: 2 4 3 Photograph from an era when the mining 8 installations of Rodalquilar were working.The 4 Au + 8 CNNa + O2 + 2 H2O ---> 10 7 photo dates from the 50's decade (Photo, Evaristo Gil Picón). 4 Na(CN2 Au) + 4 NaOH. 9 9 In 4 cleaning tanks (11) the mixture of mineral and cyanide is removed and ventilated in order 11 to obtain the solution rich in gold, that is reclaimed in the tank (12).The cyanide solution 12 11 is rinsed in tanks (13) and afterwards put 11 through a filter. Immediately following the 13 ventilation continues under a partial vacuum by 11 14 15 means of pumps in tanks (14) and, straight 16 System of cleaning tanks in operation (Photo, afterwards, is added to zinc dust in a tank (15, 17 Evaristo Gil Picón).

78 14. The Post-volcanic sediments of La Molata de las Negras

Juan C. Braga - José M. Martín

In La Molata de Las Negras sedimentary rocks above the present sea level.The presence of are present that record the geological history of coral reefs and oolitic limestones indicates that the Cabo de Gata region since the volcanic during the formation period of units B, C and D activity. Above the volcanic basement a series (Messinian), the climate of the western of sedimentary units may be observed that Mediterranean was warmer than at the present correspond to deposits formed in a small basin day and similar to that of tropical latitudes at (an inlet or bay), connected with the present. Mediterranean, and presently emerged, uplifted

La Molata D La Joya Bioherm C B A Volcánics

UNIT A theses rocks comprises clasts and grains coming Field view of Consists of bioclastic limestones; rocks composed from the erosion of the volcanic relieves. bryozoans and fossil bivalves of the remains of bryozoan skeletons, bivalves, red that formed the algae, starfish, sea urchins and foraminiferans. limestone These organisms lived in the small marine basin of of Unit A. Las Negras, joined to the Mediterranean in the Upper Tortonian-Lower Messinian, around 7 million years ago.The organisms whose remains form these rocks are similar to those that today live, and produce sediment, in the marine platform surrounding Cabo de Gata.The climate in the The remains of calcareous algae and bryozoans that presently live on the seafloor of the Cabo de region during this period would have been similar Gata platform produce a sediment similar to that to present or slightly warmer. A small proportion of which formed the limestone of Unit A.

79 14. The Post-volcanic sediments of La Molata de las Negras

UNIT B. CORAL REEFS underwent erosion (observed in the panorama as that which stand out in the panorama, easily and view point from the central part of the appreciable from this perspective.These reefs TAfter deposition of the bioclastic limestones hillside). are mainly formed through the in situ there was a stage of uplift and deformation of the accumulation of the calcareous skeletons of basin seafloor, in such way that before In Unit B, formed during the Messinian around corals belonging to several genera (Porites, the following unit (unit B) was deposited, the 6 million years ago, coral reefs stand proud in Tarbellastrea and Siderastrea). Between the coral bioclastic limestones were inclines and the form of isolated pinnacles (bioherms), such colonies and around the pinnacles, algae and invertebrates lived, whose skeletons also contributed to the formation of carbonate DISTRIBUTION AND STRUCTURE OF BIOHERMS IN THE REEF STRUCTURE sediment. Blocks derived from these reefs, such as that observed to the left of the large pinnacle, A. Diagram of a reef mound Hemispherical colonies Sticks fell down slope and became mixed with the (bioherm) marls and mud that were being deposited in the Breccias and calcarenites sea offshore, in deeper regions, situated towards our left. Marls formed through the settling of silt from suspension in seawater, and through the accumulation of the skeletons of planktonic 10 m micro-organisms such as foraminifers, unicellular Laminar colonies B.Scattered distribution of algae, and at times diatoms. bioherms in the platform

Basin Slope Platform

100 m

Tarbellastrea coral colony, one of the components of the Unit Slumped blocks of bioherms intercalated between fine-grained sediments in the basin B bioherms.

80 14. The Post-volcanic sediments of La Molata de las Negras

UNIT C cyanobacteria.Towards the sea (towards the UNIT D left), the reef gave way to a slope where debris Rests on an erosion surface that had an effect on Corresponds to a fringing reef that was coming from its destruction accumulated. the reef (Unit C) and removed a large part of its advancing from our right towards our left. The grain size of this debris is segregated deposits.This erosion surface is the expression of Here the corals are almost exclusively Porites downslope, in a way that it continually the Messinian desiccation of the Mediterranean at and the coral colonies are surrounded by becomes finer. Between the reef debris, other this locality, known as the salinity crisis. Its age is foraminifers and encrusting red algae; that in organisms grew, such as calcareous green end Messinian (around 5.5 million years ago). turn are covered by stromatolites, that is to say, algae (Halimeda) and bivalves. carbonates that are precipitated (or bound) Unit D is fundamentally formed from stromatolites by the action of micro-organisms, mainly and oolitic carbonates.The latter are made up of microscopic, spherical particles, called ooliths, with an internal structure of concentric layers of calcium DIAGRAM SHOWING ONE PHASE OF REEF GROWTH carbonate. Oolites are presently forming in the shallow, agitated waters of tropical seas. N-S Stromatolites are domes or irregular constructions formed by miilimetre-thick (or less) layers of carbonate.

Reef laguna framework

Talus Distal slope Proximal slope slope

Lagoon Bioclastic breccias 10 m 0 10 m Reef crest Calcirudites Coral thicket Microscopic view of ooliths that Field view of stromatolites, with their Coral pinnacles Calcarenites formed the carbonates of Unit D. typical laminated structure.

Coral blocks Calcilutites and breccias

81 15. Bentonites of cabo de Gata

Carlos Feixas

GENESIS AND NATURE The Cabo de Gata bentonites are by nature OF BENTONITES around 75% to 95% Calcium-Sodium- Magnesium types, and the rest of the rock Bentonite is a rock composed of minerals consists of other types of clays and small from the clay group.Their internal structure quantities of other minerals originating from of superimposed layers of different chemical volcanic rocks.They display various colours, composition defines their key characteristic: from reds, greens, yellows and blacks, to whites. their capacity to absorb a quantity of water The deposits have an irregular and stratified several times greater than their own volume. morphology. This is produced through storage of fluid in the spaces that exist between the different layers. SIMPLIFIED DIAGRAM OF BENTONITE FORMATION Bentonites originate from the alteration 200 m Alteration of volcanic of volcanic rocks, also through processes of rocks to bentonite hydrothermal alteration (rise of hot solutions through fractures) or also through weathering 200 m alteration (due to the action of meteoric water).

The special composition of the Cabo de Gata volcanic complex means that within it the greatest concentration of bentonite deposits in Volcanic rock Bentonite Spain formed. In fact, they constitute the only exploited industrial minerals that exist within the Natural Park. Descent of cold meteoric water Increased heat Increased heat Ascent of hot hydrothermal solutions

82 15. Bentonites of cabo de Gata

DISTRIBUTION OF QUARRYING. GEOLOGICAL MAP OF THE CABO DE GATA AREA

Undifferentiated Recent detritus

Pliocene sand and conglomerate Carboneras Marls, clay, sand and carbonate Gypsum Fringing reef, marl and bioclastic carbonate

Bioclastic carbonate

Bentonite quarry exploited in an intermittent fashion in the Volcanic rocks Serrata de Níjar.The bentonite masses that display some A Betic substratum Fernán Pérez colouration hold less commercial interest than those that are white.

Serrata 5 Km

B Las Negras Rodalquilar

C Cabo de Gata The main areas of quarrying within Cabo de Gata are found in: Quarrying of white bentonite in the area of Morrón de Mateo. San José Cantera de Los Trancos (A) Cortijo de Archidona (B) El Morrón de Mateo (C)

83 15. Bentonites of Cabo de Gata

Bentonite mining is carried out through an open cast quarry method. In a modern quarry the following activities are undertaken:

◗ Conditioning and preparation The discovery of productive layers takes place with the help of excavating machines or mechanized tractors.

◗ Extraction Once the surface is cleaned off, quarrying is The mineralized body might be covered by non-mineralized Los Trancos quarry is the principal bentonite mining concern rocks that need to be removed for quarrying. in the park.The extent of the quarry benches can be observed, carried out by cutting down benches taking the lorries as a scale. lengthwise along the face, with a height of about 10 metres and a length close to 50 metres.

◗ Drying and classification The material quarried in this way is spread out across large areas or “heaps”, cleaned of impurities and classified by qulaity according to the use for which it is destined. Conditioning Extraction and preparation Pile

◗ Storage Drying Classification The dried and classified material is stored in large uncovered piles ready for transport to treatment plants or for direct sale. Bentonite Volcanic rock

84 15. Bentonites of Cabo de Gata

USES AND APPLICATIONS cleansing aids and fertilizers, also as discolourants and clarifiers of wines and oils. Bentonite clays, due to their physical properties, are utilised in many industrial fields. ◗ Properly compacted it is an excellent impermeable material, used to this end for ◗ In the smelting industry they are used, along holding back and securing residues in storage with siliceous sand, to prepare the mould of containers and potentially contaminant manufacture parts, in that they are capable substances. of fusing together the sand, without altering the composition of the cast.

◗ Addition to cements allows mortars to remain fluid for a longer period of time, for which its use is essential in special cements.

◗ As an integral part of drilling mud. Due to its addition, the viscosity of the drilling mud increases and is capable of pulling out broken components more easily. Additionally, it is capable of covering and keeping the walls of the borehole intact when drilling of the borehole finishes.

◗ Its addition to powdered irons minerals means that they can be recovered in a profitable way from smelting. Characteristic field view of bentonite clays: white- ◗ coloured powdered Their capacity for absorbing water and ionic masses, greasy to the exchange means that they can serve as touch and very plastic.

85 16. Marine sediments of Cañada Méndez (Agua Amarga)

Juan C. Braga - José M. Martín

In the outcrops of Cañada Méndez, structures are extremely abundant in the exceptionally exposed carbonate sediments carbonates, such as lamination, cross- generated in temperate and shallow marine stratification, etc., reflecting their transport platforms, with temperatures and salinities through the action of waves and by currents identical to the modern Mediterranean, are on the same marine bottom. exposed. They are located directly on top of volcanic rocks 9.6 million years in age. At the very base of the sediment succession, just above the volcanics and immediately beneath the carbonates, sand of volcaniclastic character appear (that is to say, supplied by erosion of the same volcanic rocks) with a few marine fossils (essentially the remains of shells).

Two different carbonate units are represented. The lower stands out here as the most important, known informally as the red unit due to its characteristic colour. It is Lower Tortonian in age, roughly 9 million years old.

These carbonates are bioclastic in nature. They consist of the abundant, highly fragmented remains of calcareous marine organisms typical of shallow marine environments (0 to 100 m deep), such as bryozoans, red algae, bivalves, echinoderms, brachiopods, benthic foraminiferans, barnacles, gastropods and solitary corals, Fragments of typical carbonate clearly visible in hand specimen and/or by producing organisms in the microscope. Ordered internal sedimentary platform environment.

86 16. Marine sediments of Cañada Méndez (Agua Amarga)

SEDIMENTARY RECORD, PHASE 1 PHASE 2 PALAEOGEOGRAPHICAL EVOLUTION AND SEDIMENTARY MODEL OF THE AGUA AMARGA BASIN

The sedimentary record in this area allows us to reconstruct the palaeogeography of the 100 m 100 m Agua Amarga Basin during the Lower Tortonian Palaeocoastline based on the interpretation of its distinct Palaeocoastline environments of deposition. Its 600 m palaeogeography was essentially that of a small Present coastline Present coastline bay, open towards the south, with a small Agua amarga Agua amarga submarine high (ridge) situated right at its entrance, especially notorious for determining episodes in its history.The basin was filled by PHASE 3 PHASE 4 different packages of sediments in successive phases.

PHASE 1: In the initial phase ramblas reached the bay, extending into the sea in the form of submarine fans.The underlying volcaniclastic 100 m sands correspond to deposits of the distal part 50 m Palaeocoastline of these sand fans, coming from the destruction Palaeocoastline of volcanic relieves.

Platform carbonates are positioned immediately Present coastline Present coastline above. By means of the dominant sedimentary Agua amarga Agua amarga structures it is possible to differentiate four units in the interpreted section: Taken from Betzler et al., 1997

87 16. Marine sediments of Cañada Méndez (Agua Amarga)

PHASE 2: A lower unit in which the most PHASE 3: An intermediate phase with corresponds to typical beach sediments. characteristic features are layers of cross- abundant trough cross-stratification (in curves, Laterally, and superimposed on the previous stratification (of rectilinear appearance, Photo Photo B).They are interpreted as marine dunes deposits, a last unit composed of fine sands with A), separated by very low-lying (almost that migrated parallel to the coast. high-angled, poorly-developed, and/or horizontal), sharp and continuous surfaces. unconsolidated muds without evident They are the deposits of storm-generated fans, PHASE 4: An upper phase in which the most sedimentary structures (Photo D).These are deposited on the protected side of a high or characteristic sedimentary structures are low- interpreted as coastal aeolian dunes and submarine volcanic ridge located to the south. angled parallel lamination (Photo C), this lagoons, respectively.

ACTUAL PANORAMA OF THE INTERPRETED FIELD SECTION

PHOTO A. Field view of layers with tabular PHOTO C. Low-angled parallel lamination cross-stratification, tied to storm fans. corresponding to episodes of beach progradation. INTERPRETATION OF THE OBSERVED PANORAMA

Volcanic Storm fans Beaches Upper PHOTO B. Field view of trough cross- substratum carbonate unit PHOTO D. Mud levels (soft sediments) stratification produced by the migration of Volcaniclasstic Sub-aquatic Coastal Debris formed in coastal lagoons. sub-aquatic dunes. rocks dunefield Lagoon

88 17. The Quay at Agua Amarga

José Vicente Coves - José Antonio Gómez

The extensive development of mining The plans of work were decided, in March 1894 activity during the 19th century and first the project wording was finalised and signed off decades of the 20th century in Almería by D. Cayetano Fuentes, and on the 18th of Province furnished the existence of a February 1895 the concession was granted by mining railway network of which only the royal order.This was for an economic railroad, vestiges are preserved at the present day. without any government grant and for a period One of the routes is that from Lucainena of 99 years. Nevertheless, in September 1894, to Agua Amarga. Across the Natural Park work on the construction of the railway had parts of the railway can still be seen and already started, and, one month later, the are preserved, and the mine workings Biscayan company announced the purchase of quay at Agua Amarga although very 63,000 oak sleepers. deteriorated.This constitutes, along with

Rodalquilar, one of the 2 most interesting The works were progressing and, GENERAL VIEW OF LUCAINENA - AGUA AMARGA archaeo-industrial elements of the by the middle of 1895, the Natural Park. quayside-unloading bay had LUCAINENA been completed. Finally, in Pte. Rafaela NATURAL PARK PERALEJOS Rambla Pte. Molinillo March 1896 the work ended. Honda Sierra Bco. del Collado de In May the first shipment of Polopillos Alhamilla Valenciano Río Alías CARBONERAS minerals accumulated in the Venta del Pobre CAMARILLAS Agua Amarga storage facilities LA PALMEROSA Línea de boarded the steamboat ALBIA. Mesa -Almería road ferrocarril ra Roldán NÍJAR Ve The cost of installing the Collado de AGUA a Albacete AMARGA Se railway was 3,500,000 pts, the ean rran mineral storage area was dite Me Sierra de Gata credited with a cost of 60,000

Locomotive LUCAINENA (Nasmyth Wilson 464/95), one of pts and the quay 265,000 pts.The total In 1901 the transport of minerals by railway the machines used on the mineral transport line from investment for establishment was around was attributed a cost of 0.025 pesetas per ton Lucainena to Agua Amarga.The photo dates from the end of the 19th century (Photo, Col. J.M. Sánchez 3,675,000 pts with an average investment cost per kilometre, and the loading cost was 0.123 Molina). of 100,000 pts/km. pesetas per ton.

89 17. The Quay at Agua Amarga

Although the mining venture company last time in Agua Amarga. A little later the maintained a good level of activity in the first mining installations and railroad started to be decade of the 20th century, in the second the dismantled.The locomotives, the bridges and second the marked started to no longer be the railway were taken apart and transported favourable. In the years that followed the First in lorries to Almería. World War, a grave iron industry crisis which took place in Europe and Spain, meant a tough trial for national mining of iron. In 1919 and

1920 the Agua Amarga storage facilities were RECONSTRUCTION OF THE INSTALLATIONS OF THE completely full of a mineral that no one MINING QUAY AT AGUA AMARGA bought.These difficulties were compounded by competition from North-African mines, salary rises that started to be introduced around this date, and included the loss of personnel due to the strong migratory movement recorded in Almería Province during this period.

The company endured a marked decline until in 1931, and faced with the impossibility of exporting its iron, it was forced to temporarily

suspend operation of the railway. Operation Agua Amarga was sporadically renewed, but in 1930, with the state of civil war, the situation worsened. During the three years of struggle the mines and railway remained in the hands of its own workforce, although without great activity. In 1939 transport by rail was restarted until activity finally ceased in 1942, the date in which the steamboat Bartolo loaded for the

90 17. The Quay at Agua Amarga

Present state of the mining installations in the mineral working quay of Agua Amarga.To the right a general view of the installations can be observed: in the background the Sierra Alhamilla, place of iron exploitation and origin for the transport network; in the foreground, the large inclined plane through which the wagons carrying minerals could descend to the silos. On the left, the remains of the said 'silos' used for mineral storage prior to final loading (Photographs, M.Villalobos).

The boat BARTOLO receiving the last cargo shipped out of Agua Amarga from the Locomotive LUCAINENA (Nasmyth Wilson 464/95), one of the machines used on the Lucainena mines.With it, a page in the history of mining in Almería closed. mineral transport line from Lucainena to Agua Amarga.The photo dates from the end of the 19th century (Photo, Col. J.M. Sánchez Molina).

91 18. The Mesa Roldán reef

Juan C. Braga - José M. Martín

GEOLOGICAL INTERPRETATION the shape of a mesa, owes its structure to the formation of coral reefs and other sedimentary The Mesa de Roldán relief feature is essentially deposits above the volcanic dome in more a volcanic dome that formed about 8.7 million recent periods.Two sedimentary units may be years ago. However, the roof of Mesa de distinguished. Roldán, the upper platform that gives this hill

PALAEOGEOGRAPHY OF THE CABO DE GATA VOLCANIC AREA DURING THE DEPOSITION OF THE REEF COMPLEX

INTERPRETATIVE GEOLOGICAL SKETCH OF Carboneras THE PANORAMA Níjar El Hoyazo

Agua Amarga

Mesa Roldán Reefs Marine basin

Las Negras W E

Reefs and oolites Los Lobos Reefs Volcanic rocks Present Coastline 5 km

Emerged Area Reefs 20 m

92 18. The Mesa Roldán reef

LOWER SEDIMENTARY UNIT A B THE REEFS

The lower sedimentary unit is constructed from the remains of coral reefs. As in other places within the region, during the Messinian, around 6 million years ago, corals utilised the raised seafloor that constituted the volcanic dome to install

themselves and form a reef.The calcareous Calcareous corals in modern tropical seas construct coral skeletons of the corals just as happens in reefs similar to those that formed in the region 6 million modern tropical seas (Photo A), finished years ago. constructing a rigid structure of carbonate rock. In the Mesa de Roldán, the coral C constructors belong to the genera Porites (Photo B) and, to a lesser extent, Tarbellastrea and Siderastrea. Other organisms such as red algae, encrusting foraminiferans, bivalves, gastropods, serpulid worms, etc. (Photo C), contributed with their skeletons to the reef construction or the accumulation of carbonate sediment.

The remains of bivalves contribute to the formation of reefal Corals of the genera Porites are the main constructors of deposits. Messinian coral reefs in Almería.

93 18. The Mesa Roldán reef

UPPER SEDIMENTARY UNIT Since that period until the Present, the climate Ooliths THE PATCH REEFS in the region has followed a general trend of cooling, although this tendency has suffered Above the lower sedimentary unit there is an strong fluctuations, especially during the last 2 m erosion surface, and, above it, a new 2 million years. sedimentary unit is present.The latter, also Messinian in age, but younger (around 5.5 Reef million years) is again constructed from coral reefs along with some particulate carbonate Ooliths sediments that are called oolites (lower figure). Here the reefs have only a small dimension, Breccias Previous Reef patches a few metres wide with a height of D 1 or 2 metres, formed by corals of the genera Porites (Photo D) and well-developed micritic Patch reefs and oolitic limestones appear in the upper unit. coatings of microbial origin (Photo E).These reefs grew surrounded by oolitic sediments. This type of oolitic sediment consist of small carbonate particles with a spherical shape and Micritic carbonate an internal structure of concentric laminations E coatings encrusting the upper part of patch reefs (Photo F). At present, ooliths, as the particles at the same time as the are known, are formed in shallow, agitated, coral colonies were periodically living. tropical seas.

The oolitic carbonates as much as the coral reefs testify that in the western part of the Microscopic image of F Mediterranean, on the southeast Iberian oolitic sediments.These particles, ooliths, constitute peninsula, during the Messinian around 5.5 the bulk of sediments in the upper unit. million years ago, at the end of the Miocene, Coral colonies of the genera Porites (vertical a tropical climate prevailed, similar to that now sticks), surrounded by micritic carbonate coatings (white hue), that constitute the patch found in lower latitudes, closer to the equator. reefs of the upper unit. 94 19. The Hoyazo de Níjar

Juan C. Braga - José M. Martín

The Hoyazo de Níjar hill is a locality of great Later on, through the decades of the 50s and geological interest. This relief feature, with the 60s in the 20th century, they were quarried a circular form, that stands out in the extensive as an abrasive product, due to their great plain of the Campo de Níjar, in fact constitutes durability.They were mined in the sediments of a small volcano whose crater emerged as an the Rambla de la Granatilla, which formed a island in the archipelago of small volcanoes small alluvial fan at the exit of El Hoyazo, in emplaced in this area around 6 million years whose sediments the very resistant garnets had ago. accumulated, coming from the destruction and erosive washing of volcanic material. It may be At the base of the Sierra Alhamilla relief, where regarded, as such, as a typical secondary source the coastline was located during this period, or “placer deposit”. and surrounding the volcanic crater of El Hoyazo, fringing reefs composed of the coral Porites and typical of warm waters developed. The reef which capped and surrounded El Joyazo is magnificently conserved, exhibiting the complete reef structure.

The Hoyazo de Níjar volcano is also known for an abundance of garnets, minerals that make up almost 1% of the volcanic rock. The origin of the garnets in the volcanic rock is related to the existence of schists rich in the same semi- precious mineral at depth, which were carried upwards towards the surface in volcanic eruptions. The garnets are desirable when they form well-shaped crystals, like jewels. In the case of El Hoyazo, people came to benefit as th such in the 19 century. Exterior view of the small atoll of fringing reefs on top of the volcanic cone. At this point, fluvial erosion by the Rambla de la Granatilla has dissected the carbonates, facilitating access to the interior of the structure (Photo, M.Villalobos).

95 19. The Hoyazo de Níjar

DIAGRAM OF EL HOYAZO DE NIJAR

C. Dabrio

The Níjar Volcano Sierra Alhamilla “El Hoyazo”

Sea Level

Interior view of Hoyazo de Níjar.The interior depression is carved into the ancient volcanic crater.The upper capping level corresponds to the reefal carbonates, that are supported externally upon the volcanic relief in the form of a small atoll (Photo, M.Villalobos).

Pre-reef substratum

Volcanic rocks

Basin 500 m 100 m Reef talus

50 0 m Reefs Detail of the reef carbonates (Photo, M.Villalobos).

96 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

101 desplegable INGLES OK copia.qxp 27/5/08 01:43 Página 2

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

4

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

5

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 The Sorbas Basin

Didactic Itinerary 1 1. The southern margin of the Sorbas Basin: the area of Peñas Negras

Juan C. Braga - José M. Martín

From the area of Peñas Negras a magnificent an almost vertical fault plane with an east-west perspective for a good part of the sediments direction.The basement materials are phyllites, filling the Sorbas Basin can be seen, and how quartzites, limestones and dolomites belonging they contact with much older material of the to the Alpujárride Complex of the Internal Zone sierras Alhamilla and Cabrera, that constitute of the Betic Cordillera, of an age known to be the margin and the substratum or basement between approximately 200 and 300 million of the basin. years.The filling material of the basin, in lateral contact with the basement, are muddy In the southern panorama (towards Sierra marlstones that intercalate with levels of Alhamilla) the contact between the sediments sandstone, and locally conglomerates.These filling the basin and Betic rocks of the basement materials correspond to the Unit 2c in the can be observed.The contact appears as a very general stratigraphical scheme.Their age is notable, rectilinear cutting and corresponds to Upper Tortonian (around 8 million years).

SOUTHERN PANORAMA

Sierra de Alhamilla Faulted Margin Recent debris

SORBAS BASIN

Muddy marlstones with sandstone and conglomerate intercalations. (Upper Tortonian)

ALPUJARRIDE SUBSTRATUM (BASEMENT) Motorway Alpujárride Limestone and Dolomite

Alpujárride phyllites

113 1. The southern margin of the Sorbas Basin: the area of Peñas Negras

In the northern panorama we can make out package of deposits (units 3 to 7), in which a forms (Unit 6) and, capping this series, other the Cerrón de Hueli. In it a good part of the calcareous bench stands out in the mid-height carbonates of microbial origin (Unit 7). All of filling sequence of the Sorbas Basin can be formed from bioclastic limestones (Unit 3). these units may be seen with greater detail at observed. In the foreground, muddy Marls are located above (Unit 5) that are a different points on the proposed route. marlstones with intercalations of sandstone lateral continuation of the coral/algal reefs and conglomerate (Unit 2c). Above these a (Unit 4a). On top of the marls the gypsum

NORTHERN PANORAMA

Microbial carbonates (stromatolites), sands and conglomerates (Messinian)

Cerrón de Hueli Collado de las Cabezas Gypsum (Messinian)

Marls (Messinian)

Coral reefs (Messinian)

Bioclastic limestones (Tortonian-Messinian boundary)

Motorway Muddy marlstones with sandstone and conglomerate intercalations. (Upper Tortonian)

114 2. Turbidites of the Peñas Negras fan

Juan C. Braga - José M. Martín

Sedimentary infilling of the Sorbas Basin was produced directly from erosion) came to be initiated around 8 million years ago (in the deposited, resulting from the destruction Upper Tortonian).The coastline was located to (denudation) of the Sierra de los Filabres relief. the north of the town of Sorbas, at the foot of the Sierra de los Filabres.The mountainous The ramblas through which sediments from the Alhamilla-Cabrera lineament was still located at mountains were cannibalised continued to enter the bottom of the sea, although Sierra Alhamilla the sea as submarine canyons. Upon entering the already formed a submarine high (submarine furrow, the submarine canyons terminated where ridge) of positive relief. Between the the slope rapidly smoothed out, unloading the aforementioned ridge and the Sierra de los majority of sediments that they had transported, Filabres a deep marine furrow existed, with forming a submarine fan.The sediments that we several hundreds of metres of depth, in which observe belong to one of these fans, here called large masses of sediments of detrital character the Peñas Negras fan. It forms Unit 2c of the (consisting of isolated particles or clasts, general stratigraphical scheme.

FIELD SKETCH OF AN OUTCROP WITH SUBMARINE FAN SEDIMENTS FROM PENAS NEGRAS

Turbidite layer

Thin turbidite layers

Background sediments (muddy marlstone)

Conglomerate layer

Faults

115 2. Turbidites of the Peñas Negras fan

In the submarine fan the sediments are considered practically instantaneous INTERNAL ORGANISATION OF A TURBIDITE SEQUENCE structured in an alternation of decimetric (in hours to weeks).The frequency of layers of sand (which stick out more repetition of this process in the area is because they are later cemented), formed about one turbidite event every few Mud-silt by turbidite currents (suspension of sand hundred years.The sediment Sand and mud), and layers of finer-grained intercalated between the turbidite sediments (muds/silts)that correspond to layers (mud-silt), with an equivalent or background sedimentation in the basin lesser thickness, on the other hand, Nevado - Filábride between each of the turbidity currents. were deposited very slowly from suspension over a time of hundreds On a geological timescale the to thousands of years for each layer. Submarine canyon Submarine fan deposition of a turbidite layer can be

SUBMARINE MORPHOLOGY OF THE SORBAS-TABERNAS AREA DURING THE UPPER TORTONIAN SHOWING THE POSITION OF SUBMARINE FANS IN TABERNAS AND PENAS NEGRAS

Palaeocoastline PALAEOGEOGRAPHY OF THE SOUTHEASTERN PENINSULA DURING THE UPPER TORTONIAN Sierra de los Filabres Rambla systems Transport direction of turbiditic sediment Carbonate Almanzora Corridor Sierra de las platform Estancias Reefs Sorbas Peñas Negras submarine fan Sierra Nevada Filabres Palaeocoastline Granada Tabernas Tortonian palaeocoastline

Present coastline Almería Submarine ridge of the proto-Sierra Alhamilla

Tabernas submarine fan

Modified from Haughton, 1994

116 3. The sedimentary fill of the basin up until deposition of the gypsum: the panorama from Los Molinos Juan C. Braga - José M. Martín

From this location the succession of sedimentary environmental changes that the Sorbas Basin deposits that filled the centre of the Sorbas Basin and the southeast Iberian Peninsula underwent during the interval between 7.1 and 5.3 million throughout their geological history. years ago (Messinian) can be observed. The geological study of the sediments allows This sequence of sediments, the stratigraphical the geographical reconstruction of the basin, record of the basin, is at the same time a result and its environmental conditions, for each of and testament to the geographical and episode of fill or sedimentary unit:

Sierra de Filabres

Los Molinos

PALAEOGEOGRAPHY DURING THE DEPOSITION OF BIOCLASTIC LIMESTONES (Unit 3, 7 Ma bp)

The lower unit (unit 3) consists of bioclastic limestones, known in the region as “Azagador limestones”.They formed Uleila BÉDAR around 7 million years ago in marine platforms of shallow FILABRES depth that surrounded the relieves that had already Mojácar Palaeocoastline emerged, the precursors to the modern sierras de los Filabres and Bédar to the north, and Sierra Alhamilla to the Sorbas Open south.They mainly stem from the accumulation of the sea skeletons of fossil algae and marine invertebrates such as Sedimentation of Lucainena Platform bryozoans, molluscs, etc. Seafloor influenced silt and plankton Modern coastline Beach Shoals by storms from suspension In the deeper marine zones, marls were deposited ALHAMILLA Carboneras (Unit 5a), formed from a mixture of silt coming from the Substratum erosion of emerged land and the fossil skeletons of micro-organisms.

117 3. The sedimentary fill of the basin up until deposition of the gypsum: the panorama from Los Molinos

PALAEOGEOGRAPHY DURING REEF DEPOSITION (Unit 5b, 6 Ma bp)

The beige coloured marls from the upper part of Unit 5 (5b) Uleila BÉDAR accumulated at the same time as FILABRES coral reefs grew along the Coral reef Mojácar coastline of the emergent Palaeocoastline relieves, about 6 million years Lagoon Coral reef Sorbas Open ago (unit 4, that does not Open sea sea Substratum DELTA outcrop in this section, but does Reef talus slope Lucainena immediately to the west in the Turrillas exposure of Hueli). Shallow sea Modern coastline (reef lagoon) ALHAMILLA Carboneras

PALAEOGEOGRAPHY DURING GYPSUM DEPOSITION (Unit 6, 5.5 Ma bp)

Unit 6 consists of thick layers of gypsum, between which thinner layers of silt and fine sand are Open Uleila sea intercalated. BÉDAR FILABRES Mojácar This gypsum formed around 5.5 million years ago Ridge by chemical precipitation due to the partial Palaeocoastline Semi-restricted basin evaporation of seawater. In the Sorbas Basin, CABRERA Sorbas which was already closed to the west and separated from Tabernas, intense evaporation of seawater developed as a result of partial isolation Lucainena ALHAMILLA Modern coastline from the main body of the Mediterranean Sea. Evaporation The confinement was probably caused by a Carboneras marine area of shallow depth (a ridge) that Gypsum precipitation Open sea Substratum Ridge separated the Sorbas Basin and the rest of the Semi-restricted basin Mediterranean.

118 4. The karst plain, the escarpment cliff and block falls

José M. Calaforra

From this position detailed aspects of the surface karst landscape of Sorbas may be clearly observed, especially the extensive karst plain and the escarpment cliff sculpted on top of the gypsum, and the block falls that result from the destruction of its own cliff.

The broad overlying plain is a result of the levelling that was produced by the introduction of alluvial fans above Karst plain. the gypsum once the basin had become terrestrial. After the erosion of this material, the process of dolina formation was initiated on the karst plain.

Differential erosion developed between the hard and resistant gypsum, and the much Longitudinal fracture on the margin softer underlying marls, which progressively increased the relief of the gypsum cliff. At the same time, parallel fractures Escarpment and cliff (archive photo, Almería Speleoclub). originated through the gravitational instability that it started to produce. These processes caused the carving and fall of large gypsum blocks onto the slope. These are known as block falls.

Longitudinal fractures on the margin of the escarpment that cause Escarpment and cliff (archive photo, Almería Speleoclub). its retreat,detachment and fall of blocks into the barranco.

119 4. The karst plain, the escarpment cliff and block falls

EVOLUTION OF THE SURFACE KARST LANDSCAPE

SNSN Gravitational Fluvial drainage Karst plain 1 2 Block falls Differential erosion instability Dolinas fractures Springs

Karstic spring

SN Scarp retreat 3 Falls and slides (block falls)

Gypsum Marls

Karstic spring Caves 120 5. Karst: source of water and life

M. Villalobos

Karst functions like a large sponge: it collects and stores all of the rainwater, later discharged to the exterior through resurgence. These are the karstic springs, source of water, fertility and life; especially in a sub-desert environment like that of Sorbas.

After an episode of rainfall, water filters through the gypsum and traverses the network of chambers and galleries until reaching the lowest point in the cave system, from where it is discharged into the valley via a spring.These springs function only in an intermittent manner, following periods of rainfall, and may be situated in middle or high Recharge Zone positions on the slopes of the valley. Zone of rapid transmission Another portion of the water, however, circulates in a much slower fashion, crossing Zone of slow through the gypsum until reaching the transmission impermeable marls. The water, which can Accumulation therefore no longer continue its journey Zone towards deeper zones, accumulates at the base of the gypsum and is displaced Impermeable Zone horizontally until it finds a place to exit into the outside.This point is located at the base of the Río de Aguas canyon, and gives birth to the springs of Los Molinos.These springs are in permanent operation and generate a creek of great ecological value. 121 6. Basin infilling after deposition of the gypsum

Juan C. Braga - José M. Martín

From this point, a UNIT 7 panorama of the post- evaporitic (after the The lower deposits in this panorama are mostly sands, muds and yellowish-white formation of the gypsum) coloured marls. During the period of formation of this material, around 5,5 million years ago (at the end of the Messinian), the Sorbas Basin was a bay closed off to the sedimentary filling of the west. At the present site of Sorbas town, there was a system of sandy barriers and Sorbas Basin can be beaches that sealed off a lagoon environment to the west. Along the fringe of the contemplated. Sierra de los Filabres, discharge of material coming from the erosion of this relief was concentrated in small deltas (fan deltas) that spread out across a narrow marine The succession of platform where oolitic limestones were forming.The deepest parts of the beaches, the fan deltas and the platforms were colonised by micro-organisms that formed deposits in this fill records microbial carbonates (stromatolites and thrombolites).The Sorbas bay open out the last phases in the towards the Mediterranean via the Vera Basin, and perhaps via the corridor of the history of the Sorbas Rambla de los Feos that separated the sierras Alhamilla and Cabrera. Basin as a marine Uleila Marine area connection to the Fan deltas Mediterranean and the FILABRES start of its history as Palaeocoastline Beach/barrier island Mojácar a fluvial basin. Enclosed CABRERA lagoon Sorbas Detail of a giant Lucainena Turrillas stromatolite; structures that ALHAMILLA are very common in the Modern coastline Sorbas Basin. Carboneras

INTERPRETATION OF THE PANORAMA

UNIT 10 UNIT 7 UNIT 8

UNIT 9 Sierra de Filabres Sorbas

122 6. Basin infilling after deposition of the gypsum

UNIT 8

On top of the previous unit, another is present formed from conglomerates, sands, muds and red silts.They are fluvial sediments formed during a temporary emergence of the basin. On the floodplain of the fluvial system, lakes of little permanence were created in which white limestones were deposited (very apparent in the landscape between red fluvial material, as may be seen in the photograph opposite).

In the centre of the basin, Unit 8 is essentially formed of red silts of fluvial origin. However, some intercalated white layers stand out in the landscape, corresponding to lagoon deposits.

UNIT 9 UNIT 10

After the episode of emersion, the Sorbas Basin underwent its last The last deposits of the sequence are fluvial sediments formed after the final emergence of the basin, less invasion by the sea around 5 million years ago, and the yellowish than 5 million years ago, in the Pliocene and Quaternary.This fluvial material records, through time, the bioclastic sands of Unit 9 were deposited.The basin is, once again, a bay change in the drainage system of the Sorbas depression, from an initial exit only towards the south (lower closed off to the west with possible connections to the open sea left hand sketch), to a dual drainage system exiting towards the south (Río Alías) and towards the east (Río through the Vera Basin and via the corridor of the Rambla de los Feos, Aguas), as occurs today. as is sketched in the figure below.

FILABRES FILABRES Río Aguas Palaeocoastline Uleila

FILABRES CABRERA CABRERA

Mojácar ALHAMILLA ALHAMILLA Sorbas CABRERA Río Alías

Turrillas Lucainena Taken from Mather, 1993

ALHAMILLA Modern coastline Alluvial fans Carboneras Drainage network Catchment area

123 7. The fluvio-karst Barranco del Infierno and Cueva del Yeso

José Mª Calaforra

The fluvio-karst barrancos, deep and with the local intensification of dissolution processes sub-vertical walls, are generated by the and karst erosion (2 and 3). Some fluvial courses combined action of fluvial erosion processes evolved rapidly while others remained as dry and karst dissolution. barrancos abandoned by permanent streams. Groups of galleries appeared at distinct levels, At an eaarly stage the fluvial network is whose genesis was related to to the progressive established, according to the structural and fall in base levels, or, in other cses, the actual lithological conditions of the area (1). level of the water saturation zone (Phreatic level Progressively, the fluvial network incises due to or water table) (4).

KARSTIC BARRANCOS

1 2 Fluvial stream Dolinas Barrancos Water table

w.t. w.t.

Dry caves Deepening of In the karst barrancos, on occasions, natural arches are 3 Incision of 4 barrancos Simas barrancos observed that are a relic of the gallery of a cavern which was located in this position. Falling water table

w.t. w.t. Evaporite formation: Gypsum (a) with intercalations Caves Ephemeral springs of Marl levels (b).

124 7. The fluvio-karst Barranco del Infierno and Cueva del Yeso

The Barranco del Infierno and Cueva del Yeso capture of water which flowed through these the Barranco del Infierno represents a surface constitute the most notable examples of fluvio- barrancos (2)., In this way, only some stretches of course, that drains its water directly from rivers, like karst evolution in the gypsum karst of the Sorbas these fluvial courses continued their deepening the La Fortuna spring, and a subterranean course Basin.The cavern has developed at the point of and evolution (3), while part of the barranco (the Cueva del Yeso) whose genesis and confluence of two karst barrancos (1). At a given remained at a greater height than base level, progressive deepening had followed the same time, a sinkhole was established that allowed the marked by the floor of the main barranco. Actually, stages as the barranco that received its water (4).

GEOMORPHOLGYC EVOLUTION OF EL BARRANCO DEL INFIERNO (CUEVA DEL YESO) ‘Stratified Chamber’ of Cueva del Yeso: the configuration of galleries at times 1 2 Dolinas relates to collapses of Cueva del Yeso large layers of gypsum, Barranco Subterranean course Phreatic Fluvial destabilised by the capture galleries erosion of marl levels (Photo, El Tesoro Water table Speleoclub archives). w.t.

w.t.

3 4 Blind valley Hanging valley Hanging valley Barranco del Karst barranco Infierno

w.t. Present Cueva del Yeso Epi-phreatic hanging gallery La Fortuna springs Subterranean stream in the Cueva del Gypsum Basal marls Yeso (Photo, Javier Les, G.E.T.).

125 8. Fossil beaches of Sorbas

Juan C. Braga - José M. Martín

The sands and muds visible in this outcrop are In this case, the sand is extracted, moved away beach sediments deposited around 5.4 million from the beach, and carried offshore by years ago (at the end of the Messinian) and storms.The aeolian dunes constitute the correspond to Unit 7a in the general emerged part of the beach, and the wind is stratigraphical scheme.This material was their principal transport agent. In the beach, deposited in the interior of a bay, with an the dominant movement is up and down the east-west layout, and clearly open towards the length of its slope, forming a very east. A system of barrier islands crossed the characteristic, low-angled, parallel lamination. bay from north to south, along a line where today In its upper part (transition to the dunes) the the town of Sorbas is located, restricting a bioturbation structures of crabs and roots are shallow lagoon in its most internal part. abundant. Immediately underneath, the so-called ‘beach rock’ is frequent; produced by The distinctive types of sediments and their early cementation and breakage in the surf. interrelationships allow the interpretation of a sedimentary model in which the following environments are differentiated:

◗ Enclosed Lagoon. Muds and fine laminated PALAEOGEOGRAPHY silts. In these desiccation cracks and the

footprints of birds and mammals which give Uleila evidence for little depth are frequent. Fan deltas FILABRES ◗ Barrier Islands. Sandy barriers, partially Mojácar Palaeocoastline emerged, in which three subzones can be Beach/barrier island defined: that of the washover fan, that of the Enclosed CABRERA aeolian dunes and that of beaches in the strict lagoon Sorbas sense.The washover fans correspond to sand lobes that formed behind the dune barrier and partially poured into the lagoon. Turrillas Lucainena Modern coastline ALHAMILLA

126 8. Fossil beaches of Sorbas

◗ Sand Shoals (Bars). Shallow PALAEOGEOGRAPHY submarine sand dunes, moved by waves, that develop trough Aeolian Washover dunes Wave ripples cross-stratification as the most evident fans Beach Submarine dunes internal structure. In the deepest part (towards the sea) they change to a planar disposition, covered with small-scale (centimetre) wave ripples. ENCLOSED ◗ Platform. Marine zone dominated by LAGOON BARRIER ISLAND SAND SHOALS STROMATOLITES PLATFORM mud sedimentation at a depth greater than fair weather wave base (around 10 m). Mounded carbonate structures The albufera of Cabo de Gata, actually exploited as a salt pan, (of decimetre to metre width), formed constitutes a living example of an enclosed back-barrier lagoon, very similar to the one that was located close to the by micro-organisms and known as site of Sorbas town during the Miocene. stromatolites, appear at the start of the platform.

Aquatic birds that lived in the lagoon left their footprint traces behind in the mud.These footprints are found today, converted into trace fossils, therefore giving evidence of their means of deposition. Taken from S. M. Stanley (1992) 127 8. Fossil beaches of Sorbas

In this outcrop the observed sediments are beach development forms a cemented layer.The the emerged part of the beach.These change mostly those belonging to the interpreted different layers, of metric thickness, dip (are rapidly into laminated sands: sands with a lagoon/barrier island system. Much more inclined) gently towards the east.The package low-angled, parallel lamination (beach in the modern (Pliocene-Quaternary) red clearly marks the advance (progradation) of the strict sense), with cemented fragments (beach conglomerates are positioned discordantly beach/barrier island system towards the east rock) and abundant bioturbation structures. above them, from Unit 10 in the general and the progressive infilling of the bay. Finally, towards the most easterly part of the stratigraphical scheme. layers, sand with a trough cross-stratification The sand layers correspond to distinctive appears, linked to the submarine dunefields in The lagoon clays (muds/silts) are superposed on episodes of beach formation.Their internal the deepest part of the beach. So then, within the beach sands and laterally interdigitate with structure varies laterally from west to east. each individual layer, sediments are laterally them towards the east.The beach deposits crop At the western end they appear as massive distinguished from the aeolian dune zone to out in the river bed of the rambla. Each phase of sands without structure, formed as dunes in the deepest submerged zone of the beach.

INTERPRETATION OF THE PANORAMA

Beach sediments Lagoon sediments Washover fans Plio-Quaternary alluvial sediments Modern debris

128 8. Fossil beaches of Sorbas

DETAILS OF THE OBSERVED STRUCTURES

Bioturbation (trace fossils of biogenic activity) by crabs and Levels of cemented beach rock. roots in the emerged part of the beach.

Washover fans

Bioturbation

Beach rock

Lagoonal muds and silts

Low-angled parallel lamination

Trough cross-stratification Details of trough cross-stratification and ripples in the Layers corresponding to beach levels inclined towards the submerged part the beach, produced by wave movement. southeast. Wave ripples

129 9. Dolinas: windows of the karst

J. M. Calaforra

From the place in which we are located a may be counted.The phenomenon may be multitude of small, circular depressions may be better observed from a birds eye view. observed.These depressions terminate in a well or sinkhole, through which they are The origin of these dolinas is known to be connected with the subterranean caverns of diverse.The majority are due to dissolution of the Sorbas gypsum karst.They are the dolinas, the gypsum rock, although they can also the windows of the karst.The sector that we be produced by the cave-in or collapse of the observe belongs to the Covadura System, and layers or include erosion of a level of marls. in its interior a multitude of small depressions

Birds-eye view of dolinas (Photo, M.Villalobos).

TYPES OF DOLINAS IN SORBAS

CAVE-IN OF A GYPSUM LEVEL EROSION OF A MARL LEVEL DISSOLUTION OF A GYPSUM LEVEL

Marl

Marl

Gypsum Gypsum Gypsum

130 10. Lapiés

M. Villalobos

Lapiés are surficial dissolution features of gypsum. and furrows, separated by sharp crests.They have They are characterised by the presence of grooves different sizes.

Sharp-crested lapiés. Microlapiés (Photo, F.M. Calaforra). 131 11. Túmulos

J. M. Calaforra

LAYERS OF GYPSUM RISE UP

1

2

3

Túmulos Field.

Túmulos (mounds) are features exclusive to increase in the volume of water that is absorbed Sorbas.They exhibit a doming of the surface layers by the gypsum crystals.They are concentrated in of the gypsum.They are generated through an large expanses forming Túmulos Fields. Túmulo. 132 12. The Cariatiz Reef

Juan C. Braga - José M. Martín

One of the most characteristic types of rock in In the Sorbas Basin there are four reef the landscape of the Sorbas Basin are reef carbonate episodes (Upper Tortonian to carbonates, that is to say, carbonates formed Messinian).Without doubt, the most spectacular from the skeletons of corals and other and well-known, and at the same time, the most organisms that lived and live in reefs, such as important volumetrically, are the 6 million year red algae, molluscs, serpulid worms, etc. old Lower Messinian reefs.

Presently the coral constructors of reefs live exclusively in warm tropical seas (Caribbean, Red Sea, Australian Great Barrier Reef, etc.).

Outcrop of the reef framework at Cariatiz.

The framework of coastal (fringing) reefs was formed from colonies of Modern reef corals in the Great Barrier Reef, Australia. Colonies of Acropora, one of the main present-day coral Porites with a stick and layer form. constructors. 133 12. The Cariatiz Reef

The Cariatiz reef, facing us, constitutes one of PALAEOGEOGRAPHY OF THE SORBAS BASIN DURING THE the best examples of fossil reefs within the FORMATION OF COASTAL REEFS (LOWER MESSINIAN, 6 MILLION YEARS AGO) Mediterranean Basin. From the point in which we are situated, and following the length of the left bank of the Barrnco de los Castaños towards Uleila BÉDAR the north (left), a spectacular section of the FILABRES Mojácar Cariatiz reef platform is visible, formed in Palaeocoastline Coral Reef the Lower Messinian around 6 million years ago. Sorbas Open Sea In this platform reef carbonates produced by Deltas Cariatiz reef in the Barranco de los Castaños.The the skeletons of corals and other organisms Lucainena Shallow Sea deposits formed in each phase of reef growth produce a such as calcareous algae and molluscs Turrillas (reefal lagoon) wedge geometry that is inclined and thins towards accumulated. Corals (almost exclusively of the ALHAMILLA Present Day Coastline the basin (towards the south), and is easily visible from Carboneras the slope on the other side of the barranco. In front of us genus Porites) formed fringes (rims) of coastal various growth phases (wedges) can be observed. reefs surrounding the emerging relieves in this The most spectacular results in the photo. period.They correspond to Unit 4a in the general stratigraphical scheme. SCHEMATIC DIAGRAM OF A PHASE OF REEF GROWTH

The reef encloses a reefal lagoon towards the land where corals and other organisms Lagoon produced from calcium carbonate also grew. Reef Crest Towards the sea, the reef generated a talus slope Coral Thicket in which debris derived from the destruction of Coral Pinnacles

the reef accumulated.The clast size of this debris Lagoon Coral Breccia and Blocks is separated down slope, in the way that each Framework Bioclastic Breccias time it is finer. Between the reef blocks and Upper Talus debris, other organisms grew such as calcareous Slope Calcirudites Middle Talus Slope Lower Talus Slope green algae (Halimeda), bivalves and fish. Calcarenites

Calcilutites

134 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 DEPOSITIONAL SETTING

ALLUVIAL FANS. Conglomerates and sands FILABRES PLIO-PLEISTOCENE PLIO-PLEISTOCENE

FAN DELTA and DELTA. Conglomerates and sandstones PLIOCENE

Gypsum RESTRICTED BASIN NO Tabernas Geological Section MARINE BASIN Seismite Marls Rambla de Tabernas MESSINIAN Filabres Desierto de Tabernas Alhamilla

Seismite Rambla de Tabernas Cerro Geological Section Alfaro Yesón alto CN-340 Alfaro (742 m) Reefs

ALHAMILLA Seismite Geological Section (Gordo SE Megabed)

Baños SUBMARINE FANS. Marls, sandstones and turbidites Río Andarax SERREVALIAN-TORTONIAN SERREVALIAN-TORTONIAN

Pechina COASTAL PLATFORM. Conglomerates GÁDOR

BETIC BASEMENT Schists, quartzites, phyllites and marbles 137 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 Tabernas Sorbas -Overa Tabernas Guadix Carboneras Granada Vera Carboneras Berja Alhama Sorbas Berja Almería Tabernas Carboneras Adra Adra Almería La Tórtola Berja Motril Almería Adra Andarax Corridor Nerja Present Day Coastline Present Day Coastline Mediterranean Sea Present Day Coastline Western Basin Reefs Braga, Martín and Quesada

138 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 and 10 km in maximum width) VERA between the Sierra de los SIERRA DE LOS FILABRES Filabres and the Sierra Alhamilla, situated to the west of the SORBAS CABRERA Sorbas Basin and in continuation TABERNAS with it. ALHAMILLA CARBONERAS NÍJAR SIERRA DE GÁDOR

ALMERÍA

CABO DE GATA

Neogene Sediment

Neogene Volcanic Rocks

Betic Substratum

139 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. 140 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. ALHAMILLA Province of Almería has become emerged.

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 ent Day Co Almería res ast Sierra de los Filabres, already emerged P lin the recently-formed mountainous massifs was e and with some elevation. As a consequence, 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 Tabernas modern River Andarax, which was 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 141 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. 142 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. 143 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.

144 Mechanisms of erosion in the desert: currents

RILL EROSION GULLIES AND BARRANCOS

The flow is Deepening of the rills channelised forming increases the capacity for furrows or ‘rills’. excavation by concentrated flows, increasing the process until rills are created and barrancos as well.

Erosive rills upon slopes are one of the characteristic features of soft hillsides in semi-arid Typical eroded landscape of gullies, known as ‘Badlands’. regions.

145 Mechanisms of erosion in the desert: evolution of slopes

A. Martín Penela

LEDGES FROM THE RETREAT OF SLOPES UNDERMINING BY BASAL UNDERCUTTING

Erosion of the softest material forms unstable cornices in the harder Lateral erosion of the slope base in meandering areas causes instability material above it, which topple down due to gravity. and, afterwards, block falls from above.

146 Mechanisms of erosion in the desert: evolution of slopes

MASS SLIDES EROSION IN TUNNELS (PIPING)

Fissures parallel to the slope allow partial slumping and the collapse of Water penetrates into the ground and generates a network of collectors vertical tunnels. through which material is removed.The pipes grow progressively and the relief ends in collapse giving rise to pseudokarstic morphologies.

Water entry holes

Discharge holes

Tensional Fissure in the slope margin

Circulation pipes

Mass slide

147

The Tabernas Basin

Didactic Itinerary

1. The turbidite succession of the Tabernas submarine fan

Juan C. Braga - José M. Martín

TURBIDITES 8 million years ago (during the Tortonian) the Tabernas Basin had not been differentiated as such, since the relieves that delimited it to the south did not exist, like they do at present; One of the most significant sedimentary the uplifting of the Sierra Alhamilla was initiated afterwards, features of the Tabernas Basin is the around 7 million years ago. existence of a thick package of detrital sediment deposited around 8 million years ago (in the Tortonian) at the bottom of the sea, at several hundred SIERRA DE LAS ESTANCIAS Reefs metres of depth, in a slope setting, at the foot of the slope and on the Palaeocoastline SIERRA NEVADA-FILABRES submarine plain.Two different types of Granada Almanzora deposits are distinguished: Corridor Almería Modern Coast a) Those of submarine fans, situated at the foot of the slope and associated Fluvial Main entry with turbidity currents, known as apparatus: point for Nevado-Filabride ramblas sediments Betic Basement turbidites. PALAEOGEOGRAPHY OF THE TABERNAS BASIN AROUND 8 MILLION YEARS AGO (TORTONIAN) b) Mass failures on the slope, caused by With information taken from Kleverlaan, 1989 Platform seismic movement (earthquakes) of great magnitude, known as seismites. Tabernas The Tabernas Submarine Fan occupied an area Fan Slope of some 100 km2 extent. In it one can Upon this sedimentary unit differentiate the most distinctive elements such Basin characterised by the alternation of as feeder channels, with a conglomerate fill decimetre layers of sandstone and marl, (with clasts of up to several cubic metres), and Actual location of Tabernas the characteristic erosive sculpture lobes, that are built as mounded deposits at (‘Badlands’) of the Tabernas Desert has located at the exit of channels, consisting of sand and mud.The source area of all these Main direction been fashioned to a great extent. sediments is the Sierra de los Filabres, located Lobe Slump Scar of sediment on the northern margin. distribution Coastline Platform Border

151 1. The turbidite succession of the Tabernas submarine fan

The turbidite succession that we observe in the INTERNAL STRUCTURE Barranco del Poblado Mejicano corresponds to OF A TURBIDITE LAYER the external zone of the Tabernas Fan and (Bouma Sequence) consists of sand layers linked to turbidity MUD-CLAY Parallel Lamination currents (suspension of sand and mud with Cross-Lamination a density of between 1.5 and 2 g/cm3), SAND Parallel Lamination intercalated with fine sediments of mud and Normal Grading clay size. Both types of sediment are present in decimetre thick layers.Turbidite currents come from the upper part of the fan, and/or Nevado - Filábride emergent area, or from the platform situated well away from here.The sediments that they transport are essentially deposited in the lobes and at the margin of the fan.The clay and mud layers are deposits that are formed at the bottom of the marine basin between every two turbidite layers. Submarine Canyon Submarine Fan

In response to differential erosion, the turbidite extraordinarily rapid.The most granular (sandy) suspension, in intervals of time from hundreds layers, which are laterally very continuous, intervals were deposited over a period of a few to thousands of years for each layer. stand out in the landscape.The succession is hours.The finest (muds) take as much as actually found to dip towards the north, as a few weeks. On the geological timescale a consequence of the later uplift of the Sierra deposition of the turbidite may well be Fan margin Alhamilla, although the original (very gentle) considered as almost instantaneous.The succession. inclination of the stratified succession was in frequency of repetition of this process within this Alternation of hard layers of exactly the opposite sense.The turbidite layers, zone was approximately one turbiditic event sandstone in detail, consist of sand whose grain size every 700 years.The sediment that is intercalated turbidites and soft layers progressively diminishes upwards, and some between the turbidite layers (clay-mud) was, consisting of mud in its upper part. Its deposition is however, deposited very slowly from muddy sediments. 152 1. The turbidite succession of the Tabernas submarine fan

SEISMITES At times in these slides only deformation folds are produced in the layers, without the sediment Throughout the turbidite succession observed in affected becoming disrupted, generating the barranco levels of seismites are intercalated structures known as ‘slumps’.In reality a complete within it. Internally they are composed of two transition exists between several situations, in types of material: (a) a conglomerate, at the base, that many slumps, if they continue through the with clasts (sometimes up to several cubic sliding process, end up by breaking up and metres) encased in a sand and mud-sized matrix, generating a breccia (intraformational breccia), and (b) a sand, in the higher part of the layer, of whose clasts frequently exhibit irregular turbiditic character (up to several metres in geometries, in a recurved form, corresponding to thickness).The origin of these layers is tied to the remains of folds. Deformation of layers produced by sliding: Slumps slumping of material in the marine platform slope, induced by earthquakes.The poorly- consolidated sediment that exists there, is easily mobilised through the shock produced by a seismic disturbance. If the shock is of sufficient intensity it slides, towards the frontal slope, at the same time disrupting and mixing with the fluid, generating a density flow that is afterwards going to give rise to a basal conglomerate deposit.The upper turbidite corresponds to sand that is lifted into suspension in the roof of the density flow, that is deposited immediately afterwards. Seismites correspond to instantaneous events on the geological timescale. Many of them have a considerable extent, and are suitable as correlation levels (guide levels).Their expanse gives an indirect One of the most characteristic levels in the Tabernas estimate to the intensity of the earthquake that Basin, interpreted as a seismite, is known as the ‘Gordo Megabed’,whose thickness reaches up to 40 metres was generated. (Kleverlaan, 1989). 153 2. The Las Salinas Travertines in the Tabernas Desert

A. Mather - M. Stokes

One of the most surprising, and at the same development is acquired is located in the place time poorly known, aspects of recent known as Las Salinas. geological processes that can be observed in the Tabernas Desert is the presence of The precise age of these formations is uncertain Quaternary travertine formations from for the moment.The process is active at present different areas within it. One of the zones and most probably it was already in operation where the better and most spectacular during the Pleistocene.

LOCATION OF THE LAS SALINAS TRAVERTINES IN RELATION TO FAULT LINES

To Granada

o

ch

le

bla de bla

rde Travertines are a type of natural limestone Ve

Ram rock, formed from the precipitation of Mexican Town carbonates out of surface and subterranean water. Modern travertines are developed in

r ja very localised zones associated with active ú

n de Rambla Las Salinas a streams, at springs in fluvial water courses, L e d To Tabernas and in general, at whatever position a la LAS SALINAS b Restaurant Rambla de Tabernas change in the velocity of flowing water is Alfaro Ram produced, so that the degasification and Petrol Station Los Callejones Bridge consequent precipitation of calcium carbonate is favoured.

To Almería

Travertines Fault Line

154 2. The Las Salinas Travertines in the Tabernas Desert

At Las Salinas it seems clear that its IDEALIZED SECTION OF TRAVERTINE GENETIC PROCESSES IN LAS SALINAS, IN RELATION TO THE DISPOSITION OF present-day operation is due to the GEOLOGICAL FRACTURES AND THE CIRCULATING FLOW OF WATER circulation of water, of both pluvial and subterranean origin, at a certain depth that ends up appearing at the surface due to a series of rather Fluvial Recharge important fractures with an approximate east-west orientation.

Thanks to this line of tectonic disturbance, a very slow and continuous stream of water flows out, with a large saline concentration owing, probably, to the washing of saline material from the area of Yesón Alto and to progressive concentration within water from capillary rise. The carbonate precipitated due to the slope creates typical travertine deposits with laminated and Rising circulation of subterranean flow concretionary structures. Young Quaternary Travertines Circulation Flow of Water

Turbidite Sequence Fault Zone

155 2. The Las Salinas Travertines in the Tabernas Desert

Detail of the internal structure of the travertines (Photo, M. Detail of travertine deposits and salt pseudostalagtites in the Villalobos). accretionary curtain (Photo, M.Villalobos).

Surface crest of the fault zone associated with the formation of travertine deposits (Photo, M.Villalobos).

General view of the travertine accretionary curtain (Photo, M.Villalobos).

156 3. The Escarpment landforms of the Cerro Alfaro District

M. Villalobos

A very characteristic morphology in the erosive In the specific case of the Tabernas Desert, the landscape of the Tabernas Desert are most visible and spectacular examples have escarpment landforms, especially visible in the the peculiarity that the sense of inclination of Cerro Alfaro district.These consist of inclined the layers (towards the north) is reversed with layers of hard material, normally sand and/or respect to the original deposition of the layers conglomerate, that protect the much weaker (towards the south), that is to say, that they have underlying material, usually marls, from been uplifted from the south and inclined erosion. towards the north.This inversion must be seen as due to uplifting of the Sierra Alhamilla, just as reflected in the accompanying figure.

EVOLUTION OF AN ESCARPMENT LANDFORM,WITH A LAYER OF HARD MATERIAL INCLINED ABOVE A PACKAGE OF WEAK MATERIAL THAT IS ERODED LATERALLY

157 3. The Escarpment landforms of the Cerro Alfaro District

INTERPRETATIVE SECTION FOR THE ESCARPMENT LANDFORMS IN THE CERRO ALFARO DISTRICT IN RELATION TO THE EVOLUTIONARY HISTORY OF THE BASIN AND UPLIFT OF THE SIERRA ALHAMILLA

Almería-Tabernas Basin Sierra de los Filabres In the period that existed between15 and 6 million years ago (Serravallian – Sea Level Messinian), the sea washed against the foot of the Sierra se los Filabres. Numerous submarine fans, a continuation of the rivers that drained the sierras, fed sediments into the marine basin, depositing a thick series of turbidites, alternating layers of weak, marl sediments and tough sands and conglomerates.

AROUND 8 MILLION YEARS AGO

Approximately 7 million years ago, at the end of the Tortonian, tectonic readjustment Sierra de Alhamilla Sierra de los Filabres had caused emergence of the Sierra Alhamilla block, separating the Tabernas Basin Almería Basin towards the north of the Sierra Alhamilla from the Almería Basin towards the south. Tabernas Basin Sea Level They continued to be marine for a significant period of time, up until around 4 million years ago. Uplift of the sierra elevated and brought up turbiditic material already deposited, reversing the inclination of the layers.The post-Messinian deposits were markedly different in these basins. AROUND 2 MILLION YEARS AGO

Sierra de Alhamilla Sierra de los Filabres Since 4 million years ago (Upper Pliocene and Pleistocene) the environment in these basins has been virtually continental. Erosive agents have acted upon Almería Basin Cerro de Alfaro, Escarpment landform Nivel del mar Tabernas Basin exposed material in the basin, especially in Tabernas, forming the erosive landscape that we can observe.The harder layers of the turbidite series create the typical landforms of dipping escarpments, also in a reversed sense to that in which they were deposited. PRESENT DAY

Post-Messinian deposits of the Almería Basin Serravallian-Messinian deposits of the Almería-Tabernas Basin, hard layers in dark green, softer layers in light green Post-Messinian deposits of the Tabernas Basin Betic Substratum; Nevado-Filábride and Alpujárride complexes

158 4. Tunnel Erosion (Piping)

Antonio J. Martín Penela

Tunnel erosion (also known as ‘piping’) It originates from the movement of constitutes a peculiar erosive mechanism which concentrated flows of water that circulate may achieve an important development in through poorly consolidated material, semi-arid regions.The resulting landforms, of producing a washout that gives way to the great scenic beauty, are known as ‘pseudokarst’ formation of tubular conduits (tunnels or pipes). or mechanical karst. In the Tabernas Desert they are superbly represented.

DIFFERENT STAGES OF TUNNEL EROSION

Collection Pipes 1 2 Drainage Pipes The removal of solid particles through the drainage orifices produces an increase in the size of the existing macropores and fissures, creating more or less complete, continuous channels, that come from the collection pipes or sinkholes through to the drainage pipes.These tunnels can have a diameter between 10 and 40 cm, and a few metres of length.

Local Base Level

Tunnel erosion is initiated through part of the rainwater permeating into the ground through fissures and cracks on the surface.

Fissures and cracks in the Collection pipes on a slope, oriented in association Drainage pipe close to surface. with fractures. local base level.

159 4. Tunnel Erosion (Piping)

DIFFERENT STAGES OF TUNNEL EROSION

3 4

The channels grow progressively until they are made Progressive development of the tunnel network, unstable. Partial or total collapse of the walls and roof occur accompanied by many collapses through part of it. A when they are flooded with intense rainwater, causing an system of barrancos is initiated in which numerous failed excess of weight in the overhangs.The phenomenon may channels and blind valleys with U-shaped sections, are also occur after a significant drought, through the intense still preserved, that rapidly evolve into V-shaped sections. cracking of the material, producing a sudden fall. Altogether, a net retreat of the slope takes place.

Failed and abandoned drainage pipe, resulting from the descent of the tunnel network towards local base level.

Large sized collection pipes or sinkholes, originating from the Weathered pseudokarstic morphology which evolves coalescence of several vertical collection pipes with the towards a system of gullies. collapse of their walls.

160 5. The Quaternary alluvial fan-lake system

A. M. Harvey

One of the most visible and characteristic The lateral superposition of fans in the same features in the recent sculpture of the Tabernas front generates a system of coalescing fans. In Desert are alluvial fans. alluvial fans, the coarsest material is deposited in the more proximal zones (closer to the The development of alluvial fans takes place at a relieves), while the finer, less-heavy sediment, break of slope produced at the contact between may be carried to the more distal zones a more or less mountainous front and a small (furthest from the relieves). In the more distal, sedimentary trough. In this morphological practically planar parts of the fan, marshy or setting, when the confined river or rambla swampy zones are frequently formed, and courses of the mountainous zone reach the include small lagoonal basins that are filled by sedimentary basin, with much lower slope, they sediments. suffer a sharp reduction in their capacity to transport bedload, generating extensive deposits in the form of a fan.

Sierra TYPES OF ALLUVIAL FAN

OPEN FAN Sierra

ENTRENCHED FANS Depression

Depression COALESCING FANS Sierra Sierra

De SUPERPOSED FANS Depression pression

161 5. The Quaternary alluvial fan-lake system

IDEALIZED SCHEME OF THE ALLUVIAL FAN-LAKE SYSTEM DURING THE PLEISTOCENE IN THE EASTERN SECTOR OF THE TABERNAS BASIN

Sierra de Alhamilla Sierra de Filabres

Tabernas Basin

Although alluvial fan morphologies are frequent and obvious throughout the desert zone, in the vicinity of the Tabernas District, it is possible to Betic Substratum distinguish an ancient yet still functioning alluvial Sedimentary Fill of the Basin fan system, that at present feeds into the main drainage of this area, the Rambla de Tabernas, an Alluvial Fans artery for the removal of sediment and water alike, Lake-Lacustrine Deposits that are discharged from the fluvial network in the eastern sector of the basin. Principal drainage direction in the basin

View of the lacustrine deposits (photo J. C. Braga). 162 5. The Quaternary alluvial fan-lake system

The fans started to function during the QUATERNARY DEPOSITS OF THE ALLUVIAL FAN-LAKE SYSTEM IN THE TABERNAS AREA Pleistocene, after an erosive period that stripped out the upper part of the sediments in the Betic Substratum basin. Rambla Honda Rambla de Fill material of the los Nudos Tabernas depresssion During the operation of these alluvial features, Lacustrine Sediments the basin drainage remained interrupted for ES Alluvial Fans some time, generating a lacustrine zone in ABR FIL which around 20 metres of sediments were E LOS River Channels RA D SIER deposited.These deposits are visible in the Observation Points vicinity of Tabernas and the Los Callejones Roads bridge (at the junction of the motorway with Rambla de la Galera Quarry the old Murcia road).

Rambla de los Molinos

Rambla de Norias Sierra del Marchante

In the map several places used for field observations are Rambla de located Tabernas TABERNAS 1. General view of coalescing alluvial fan deposits in Rambla Honda Rambla de la Sierra 2. Coarse river sediments typical of the more proximal part of the alluvial fan, in relation to the supply front from the Los Bar SIERRA DE ALHAMILLA Filabres relief Alfaro 3. Finer sediments characteristic of distal deposits (visible in the quarry area) 4. Lagoon sediments visible in close vicinity to the Alfaro petrol station 163