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Middle Miocene coral-Oyster reefs, Murchas, Granada, Southern Spain
Abstract
Middle Miocene coral-oyster patch reefs crop out at Murchas. They are irregularly shaped masses of coral-oyster boundstone, up to 18 m wide and 3-4 m high, that developed on the outer part of a homoclinal ramp, seaward of some sand shoals, in a mixed carbonate-terrigenous environment. Heliastrea is the predominant coral. Porites, Tarbellastraea and the phaceloid coral Mussismilia are also important components. These corals show no clear pattern in their distribution and appear embedded in a silty (bioclastic) matrix. Oysters in the reef community belong to the species Hyotissa aquarrosa.
... Shallow-marine sedimentation continued to the north and east of Los Guájares valley, with deposition of terrigenous rudstones to packstones, unconformably overlying the Betic basement and older Miocene deposits (Avidad et al., 1978;Braga et al., 1996;Estévez et al., 1985;González-Donoso, 1978;Rodríguez-Fernández, 1982;Rustichelli et al., 2013). These limestones extend southward to the Ízbor valley section (Fig. 1B) and probably are the remnants of the connection of the Granada Basin with the Mediterranean Sea during the Tortonian. ...
... These are the only coral reefs confidently dated as early Tortonian known in the Betic Cordillera. The genus richness in these reefs is lower than the one in older Langhian reefs in the Granada Basin, in which 8 genera were reported (Braga et al., 1996), and lower than the richness in late Tortonian reefs, which comprise 7 genera in the Almanzora Corridor (Martín et al., 1989) (Fig. 1A). Both assemblages include the three genera found in Los Guájares. ...
The Los Guájares valley is located about 35 km south of Granada in the Internal Zones of the Betic Cordillera. The Miocene deposits in this area consist of six sedimentary units separated by unconformities, which are exposed in small and laterally discontinuous outcrops overlying metamorphic rocks of the Alpujárride Complex. The lowest unit comprises upper Serravallian marls with planktonic foraminifera filling neptunian dykes and covering Triassic dolomitic marbles of the Alpujárride Complex. These marls reflect deep marine deposition on the Betic basement under a local extensional regime. Uplift of the region led to emergence and deposition of continental red alluvial-fan conglomerates and foothill breccias. The overlying unit, a shoreline conglomerate with small oyster banks, indicates relative sea-level rise. Shallow-marine conditions continued during the deposition of the following unit, early Tortonian in age, which consists of calcareous sandstones with hermatypic corals. Small patch reefs developed in the overlying unit composed of sandy limestones with corals ( Porites, Tarbellastraea, Thegioastraea ) and oysters, and sandy limestones with coralline algae in the most distal areas. The coral reefs in Los Guájares and some coral heads in Albuñuelas, a near locality, are the only record of early Tortonian coral buildups in the Mediterranean. The last marine unit comprises lower Tortonian conglomerates, sandstones and siltstones accumulated in the front of a small delta. Oyster banks and concentrations of Turritelines suggest high nutrient levels in the delta-front paleoenvironments. The Los Guájares valley area emerged afterwards, following the onset of a compressional geodynamic regime in the central Betic Cordillera and since the early Tortonian only small bodies of foothill and alluvial-fan deposits formed in a predominantly erosional context.
... However, Middle Miocene reefs and related facies are known elsewhere in the Eastern Mediterranean, in Israel (Buchbinder et al. 1993) and in the Mut basin (southern Turkey) (Vescogni et al. 2014). Middle Miocene reef development was more common in the western Mediterranean region; e.g. in Hungary (Oosterbaan 1990), Austria (Riegel and Piller 2000), northern Italy (Chevalier 1962), Algeria (Belkebir et al. 1994), France (Chevalier 1962;Cahuzac and Chaix 1996) and Spain (Calvet et al. 1994;Braga et al. 1996). ...
The existing chronostratigraphic framework in NW Cyprus of two-phase, Early and Late Miocene reef and associated facies development is tested and improved using a combination of calcareous nannofossil, benthic and planktic foraminiferal, and also Sr isotope dating. Following localised Late Oligocene neritic carbonate deposition (e.g. benthic foraminiferal shoals), reefs and related facies (Terra Member) began to develop c. 24 Ma (Aquitanian) and terminated c. 16 Ma (end-Burdigalian). Early Miocene reef and marginal facies were then extensively redeposited as multiple debris-flow deposits until c. 13.7 Ma, influenced by a combination of global sea-level fall (related to growth of the East Antarctic Ice Sheet) and local- to regional-scale tectonics. Reef growth and related deposition resumed (Koronia Member) c. 9.1 Ma (Tortonian), then terminated by c. 6.1 Ma (mid-Messinian), followed by the Messinian salinity crisis. Neritic accumulation in NW Cyprus began earlier (Late Oligocene), than in southern Cyprus (Early Miocene). The Early Miocene reefs developed on a c. N-S-trending structural high in the west (Akamas Peninsula area) whereas the Late Miocene reefs developed on both flanks of the neotectonic Polis graben. The two-phase reef development is mirrored in SE Cyprus and in some other Mediterranean areas; e.g. S Turkey, Israel, Italy, S Spain.
Supplementary material: GPS Locations of dated samples, the Sr isotope method and the samples examined for planktic foraminifera biostratigraphy are available at https://doi.org/10.6084/m9.figshare.c.5205315 .
... Consecuencia del adelgazamiento inducido por estas estructuras fue el inicio de la generación de los relieves béticos en el Langhiense superior (Braga et al., 1996) y su desarrollo subsiguiente (Sierra de los Filabres y Sierra Nevada), la exhumación de segmentos corticales relativamente profundos (Azañón et al., 1998 ), y la compartimentación de los dominios aún sumergidos, nucleándose lo que posteriormente pasarían a ser las cuencas intramontañosas (Granada, Guadix-Baza, Dalías, Sorbas, etc, en el caso de las Cordilleras Béticas) que aún hoy continúan sometidas a levantamiento (Braga et al., en prep.). La generación de relieves emergidos disparó la erosión de los mismos, lo que a su vez contribuyó a adelgazar aún más la corteza, favoreciendo la regeneración de los relieves mediante respuesta isostática a la descarga producida por el efecto combinado del adelgazamiento estructural y la erosión. ...
The Geosites project, initiated by the IUGS Global Geosites Working Group and also supported by UNESCO, aims to produce a global inventory of the Earth's geological heritage. This global inventory requires a systematic methodology, which is based on the selection of geological frameworks with international significance, in every country. These frameworks are topic events, time or regional geotectonic elements, etc. The second step of this methodology is the selection of the most valuable and representative sites of these geological frameworks (geosites). Fortunately, the geological diversity of Spain provides a great number of frameworks with global significance; in addition, the high quality of outcrops (due to topographic and climatic reasons) will allow the selection of illustrative geosites. In this paper a list of Spanish geological frameworks set by consensus is presented. It was prepared following the Geosites Project methodology without taking into account the National Inventory of Geosites, which is in progress and covers a 40% of the Spanish territory. The IGME (Geological Survey of Spain) composed a preliminarg list, which was sent to all the University Departaments of Geology, Mining Schools and Research Centers, for its analysis, discussion and improvement. The result of this request was the selection of 20 "frameworks", which is the first Spanish contribution to the Geosites Project.
... The yellow square highlights the study area. Localities are given by numbers: 1 Murchas (Braga et al., 1996), 2 Sant Pau d'Ordal (Permanyer and Esteban, 1973; Calvet et al., 1994), 3 Hérault (Chevalier, 1961), 4 Saubrigues (Chevalier, 1961), 5 Manciet (Chevalier, 1961), 6 Torino Hills (Chevalier, 1961), 7 Balistra (Pedley, 1996 and further literature), 8 Aléria (Pedley, 1996 and further literature), 9 Ohrid (Okhrid) (Kojumdgieva and Strachimirov, 1960; Kojumdgieva, 1976), 10 Pleven (Kojumdgieva et al., 1978; Budd et al., 1996), 11 Oymapinar (Karabıyıkoğlu et al., 2005), 12 Tepeki and Köprücay (Karabıyıkoğlu et al., 2005), 13 Retznei and 'Tittenbach' quarry (Friebe, 1991; Friebe, 1993; Reuter and Piller, 2011), 14 Duplek (Baron-Szabo, 1997), 15 Fertörákos (Randazzo et al., 1999), 16 Wiesfleck (Kroh, 2007), 17 Sooß-Lindkogel (), 18 Müllendorf/Großhöflein (Dullo, 1983; Riegl and Piller, 2000), 19 Budapest area (Oosterbaan, 1990; Randazzo et al., 1999; Saint Martin et al., 2000), 20 Zebegény (e.g. Oosterbaan, 1990; Randazzo et al., 1999), 21 Bahna (Tiţă, 2007), 22 Delineşti (Tiţă, 1999Tiţă, , 2000), 23 Lăpugiu de Sus (Rus and Popa, 2008), 24 Podeni (Saint Martin et al., 2007; Bucur et al., 2011), 25 Devínska Nová Ves (Švagrovský, 1978), 26 Židlochovice (Cicha, 1978), 27 Borač (Brzobohatý and Cicha, 1978), 28 Korytnica (Bałuk and Radwański, 1977; Roniewicz and Stolarski, 1991; Stolarski, 1991), 29 Grobie (Górka, 2002), 30 Maksymivka (Radwański et al., 2006). ...
The south-western edge of the Leitha Mountains in the southern Vienna Basin (Austria) exposes parts of an Upper Langhian (Middle Badenian) shallow water (b30 m) carbonate platform. The study of its ecospace comprises sedimentological and palaeontological data of 4 up to 36 m thick carbonate sections of the Müllendorf quarries which have been logged and subjected to detailed investigation and sampling. The sed-imentary record is dominated by coralline algal debris sands which represent 7 distinct lithofacies (bioclastic coralline algal-mollusc facies, Hyotissa facies, Isognomon facies, coral facies, rhodolith facies, bryozoan facies). All these facies are described in detail in respect to lithology and biota and are palaeoecologically interpreted. Striking features of these limestone successions are periodical intercalations of coral-and mollusc-rich hori-zons. Their formation had been triggered by water turbidity and low amplitude changes in relative sea level. These relations are especially interesting as the platform carbonates formed at the northern edge of the Langhian Peri–Mediterranean reef belt. Water turbidity, as ecological master factor, and depth played the fundamental role in ecosystem and community expression within ecospace. The lateral distribution and the ecological relations between the various facies types allow proposing an ecospace-occupation model.
... house, 1999), but at dierent times (Fig. 5). In fact, geochronological (Platt and Whitehouse, 1999; Zeck and Whitehouse, 1999 ; Sa nchez-Rodrõ Âguez and Gebauer, 2000 ) and sedimentological data (Braga et al., 1996) indicate that the upper units of the AC underwent HP metamorphism before or at 20 Myr and were already exhumed at 18±15 Myr. At this time (4±8 Myr before its exhumation) the NFC was still being subducted. ...
This study provides new constraints on fast cooling and exhumation rates of high-pressure metamorphic rocks in young active mountain belts. Ion microprobe (SHRIMP) U–Pb analysis of zircon in a pyroxenite layer of the Cerro del Almirez ultramafic rocks (Nevado-Filábride Complex, southern Spain) gave an age of 15.0 ± 0.6 Myr (95% c.l.). Mineral inclusions demonstrate that zircon formed close to the high-pressure peak. Combined with previous fission track data, the 15 Myr age suggests high cooling (˜ 80 °C Myr−1) and exhumation (˜1.2 cm yr−1) rates for the unit. The new results indicate that both the Nevado-Filábride Complex and the overlying Alpujárride Complex, with somewhat higher ages and exhumation rates, underwent similar metamorphic evolutions at different times. This implies that the Alpujárride rocks were exhumed when the Nevado-Filábride was subducting and that the same tectonic scenario propagated from one portion of the Betic Cordilleras to another.
... The Neogene-Quaternary sediments of the Granada Basin (southern Spain) unconformably overlie a basement paleorelief constituted by rocks from the Internal and the External Zones of the Betic Cordillera (Fig. 1). The marine record of the Granada Basin extends from the Middle Miocene to the Tortonian, and the continental sedimentation from the latest Tortonian (Middle Turolian) to the Quaternary (Dabrio et al., 1982;Martín et al., 1984;Braga et al., 1990Braga et al., , 1996García-Alix et al., in press). This paper deals specifically with the interval of the continental history spanning the latest Tortonian (Middle Turolian) through the Zanclean (Ruscinian), for which a high resolution biostratigraphy based on rodents has been established (García-Alix, 2006;García-Alix et al., in press). ...
This paper analyses the relationship between the evolution of the Late Miocene and Early Pliocene rodent and insectivore assemblages from the Granada Basin (southern Spain) and climate changes. These climatic changes, in terms of humidity and temperature fluctuations, are inferred from variations of the relative abundances of taxons with definite ecological preferences. There is a general tendency towards a temperature increase from the latest Tortonian (Middle Turolian) to the Messinian (Late Turolian), and towards a decrease from the Mio-Pliocene boundary (latest Turolian–earliest Ruscinian) to the end of the Zanclean (Late Ruscinian). Dry conditions predominate in the latest Tortonian (Middle Turolian). At the beginning of the Messinian (Late Turolian) there was a significant increase in humidity, followed by an aridification throughout the end of the Messinian and Zanclean (Late Turolian and Ruscinian). These climatic variations are in accordance with the sedimentary evolution of the basin, and agree with the climatic interpretations inferred from the shallow-marine carbonate sediments (temperate/ tropical) deposited in the marine basins of southeastern Spain during the studied time interval.
... The progressive unroofing and erosion of Betic nappes is recorded by the lithological variety of clasts incorporated in various types of mass-flow deposits within lower Miocene pelagic sediments (Rodríguez-Fernández, 1982). However, the first evidence for emerging Betic basement highs is the occurrence of upper Langhian coral reefs and associated coastal conglomerates in the southern Granada Basin (Braga et al., 1996a) and in the Vera Basin (Barragán, 1997). In the Granada Basin these deposits appear in a single isolated outcrop near Murchas (Fig. 1), indicating the presence to the north of an emerged Betic island, probably the precursor of the Sierra Nevada -La Tórtola chain (Fig. 1). ...
The facies distribution in the sedimentary units infilling a series of Neogene basins has been used to reconstruct the relief generation and uplift across the Internal Zone of the Betic Cordillera in southern Spain. Uplift amounts and average rates can be estimated using the current elevation of the outcrops of well-dated deposits indicative of ancient sea-level positions. Coral reefs and coastal conglomerates record the initial development of emergent Betic relief during the Langhian. Continental and marginal marine deposits indicate the existence of a large island centred on the present Sierra Nevada–Sierra de los Filabres chain by the end of the Middle Miocene. The precursor of the Sierra Nevada–Sierra de los Filabres chain, originally part of this large island, remained emerged whilst the surrounding areas were re-invaded by the sea during the early Tortonian. At the end of the Tortonian the inland basins (Granada and Guadix basins) became continental, while the Sierras de la Contraviesa, Sierra de Gádor and Sierra Alhamilla emerged, separating the Alborán Basin from the Alpujarra, Tabernas and Sorbas basins, which became narrow passages of the Mediterranean Sea. In contrast, the Sierra Cabrera emerged during the late Messinian, suggesting a progressive uplift from west to east of the sierras south of the Sierra Nevada–Sierra de los Filabres chain. During the Pliocene, only the low areas closest to the present-day coast remained as marine basins and progressively emerged throughout this stage. The highest average uplift rate recorded is 280 m/Ma for the Sierra de Gádor, although the average uplift rates of upper-Neogene coastal marine rocks since depositon have maximum values of approximately 200 m/Ma. Most of the uplift of the Betic mountains took place before the early Pliocene. The recorded uplift of Neogene rocks was highest at the margins of western Sierra Nevada, where peaks higher than 3000 m occur. The average rates of uplift were lower to the east of this major relief. The main sierras and depressions in the present-day landscape correspond respectively to the emergent land, in which uplift was concentrated, and to the marine basins that existed before the final emergence of the region. The altitude of the sierras reflects the time at which they became emergent, the highest mountains being the first to rise above sea level.
... Morton, 1989). Oyster buildups today are generally monospecific and only develop in brackish settings (Stenzel, 1971; Bahr and Lanier, 1981; Bottjer, 1985; Puckett, 1994). Although ancient open marine oyster reefs exist they are rare, much smaller than those described here, and contain a diverse assemblage of reefbuilding zooxanthellate corals (cf. Braga et al., 1996). In modern settings a number of environmental factors have been shown to govern oyster buildup abundance and distribution within brackish coastal environments and include: temperature, salinity, nutrient levels, terrigenous clastic sedimentation rate, nature of the sea floor, predation, disease, and proximity to currents (Bahr and Lani ...
Paleoestuarine, monospecific oyster bioherms and biostromes formed by the extant, soft-bottom oyster, Ostrea angasi, are prolific in the Pliocene Norwest Bend Formation, Murray Basin, South Australia. These buildups are pioneer communities that record “arrested ecological succession”, comprising only the Stabilization and Colonization Stages of reef development. Each of these stages is directly linked to a different phase of marine inundation.Stabilization is restricted to the early transgressive systems tract when pre-existing topographic highs were flooded and populated by dense aggregations of oyster clusters. Colonization is manifest throughout the transgressive and highstand systems tracts when increased accommodation allowed the vertical and lateral accretion of juvenile oyster communities into large buildups. Bioherms formed in areas of low terrigenous clastic sedimentation and seafloor disturbance, both of which encouraged rapid community growth. Biostromes in contrast, record buildup development on an unstable seafloor where episodic, catastrophic community burial by storm sedimentation created repeated conditions of seafloor stabilization and colonization. Subaqueous dunes formed as part of the falling stage systems tract when river and tidal currents reworked shell material from bioherms and biostromes into large-scale, subaqueous bedforms.Brackish water conditions in the palaeoestuary, a turbid water column, mesotrophic nutrient levels, and high spatial homogeneity of oyster buildups are interpreted to have prevented recruitment of specialized, stenohaline organisms that typify the Diversification Stage of other metazoan reefs. Comparison with modern, low diversity oyster communities imply that high fecundity and growth rates as well as exogenic nutrient cycling also made oysters in the Norwest Bend Formation highly adapted competitors capable of thriving in this nutrient-rich setting.
... The Neogene-Quaternary sediments of the Granada Basin (southern Spain) unconformably overlie a basement paleorelief constituted by rocks from the Internal and the External Zones of the Betic Cordillera (Fig. 1). The marine record of the Granada Basin extends from the Middle Miocene to the Tortonian, and the continental sedimentation from the latest Tortonian (Middle Turolian) to the Quaternary (Dabrio et al., 1982;Martín et al., 1984;Braga et al., 1990Braga et al., , 1996García-Alix et al., in press). This paper deals specifically with the interval of the continental history spanning the latest Tortonian (Middle Turolian) through the Zanclean (Ruscinian), for which a high resolution biostratigraphy based on rodents has been established (García-Alix, 2006;García-Alix et al., in press). ...
This paper analyses the relationship between the evolution of the Late Miocene and Early Pliocene rodent and insectivore assemblages from the Granada Basin (southern Spain) and climate changes. These climatic changes, in terms of humidity and temperature fluctuations, are inferred from variations of the relative abundances of taxons with definite ecological preferences. There is a general tendency towards a temperature increase from the latest Tortonian (Middle Turolian) to the Messinian (Late Turolian), and towards a decrease from the Mio-Pliocene boundary (latest Turolian–earliest Ruscinian) to the end of the Zanclean (Late Ruscinian). Dry conditions predominate in the latest Tortonian (Middle Turolian). At the beginning of the Messinian (Late Turolian) there was a significant increase in humidity, followed by an aridification throughout the end of the Messinian and Zanclean (Late Turolian and Ruscinian). These climatic variations are in accordance with the sedimentary evolution of the basin, and agree with the climatic interpretations inferred from the shallow-marine carbonate sediments (temperate/ tropical) deposited in the marine basins of southeastern Spain during the studied time interval.
Based on more than 4500 km of new and re-processed multichannel seismic lines, high-resolution seafloor bathymetry, available well data, and basement dredge samples, we have re-evaluated the entire stratigraphy and the tectonic evolution of the Alboran and western Algerian basins. We have correlated the sediment units deposited since the beginning of the formation of the different sub-basins, and we present for the first time a coherent stratigraphy and large-scale tectonic evolution of the whole region. The results provide the information to test and refine models of the geodynamic evolution of the westernmost Mediterranean.
The data analysis supports an independent evolution of the sub-basins through the latemost Oligocene and Miocene, and a common Plio-Holocene evolution. The latemost Oligocene and Miocene evolution was controlled by the evolution of the Gibraltar subduction system. The oldest sedimentary unit is restricted to the West Alboran and Malaga basins depocenter that during the latemost Oligocene and early Miocene connected to some smaller marine basins currently uplifted and located onshore on the Betics range. Later, during the middle Miocene, the Habibas and Pytheas sub-basins formed a second depocenter on the North African margin. The different sedimentary units found in both depocenters, together with their different deformation patterns, support that the West Alboran-Malaga and the Habibas-Pytheas depocenters were separated by a major tectonic boundary. The early Tortonian initial arc magmatic activity produced the formation of new areas floored by a volcanic basement by the end of the late Tortonian, when the first sedimentary units deposited in the East Alboran sub-basin, and probably during the late Tortonian-early Messinian in the South Alboran sub-basin. Extension of the back-arc setting created oceanic crust flooring the Algero Balearic Basin. The extensional formation of the westernmost Mediterranean basins ended in the latemost Miocene. The western migration of the subduction system stopped and the convergence between the African and the European tectonic plates started to dominate the tectonic evolution of the region. During the Plio-Holocene, the sub-basins did not further subside individually so that these sediments have spread out across the whole Alboran Basin. A new tectonic contractional and strike-slip fault system developed that is active nowadays.
The integration of our results together with the most recent tomographic studies has been used to test and refine the existing kinematic models of the area. None of the existing models explains all our large-scale observations.
The Miocene is an essential period in the configuration of
the present-day relief of the Betic Cordillera and the
South Iberian continental margin, which determined the
structure and evolution of the Neogene sedimentary
basins (Fig. 3.1). The crustal thinning processes that
occurred during the early and middle Miocene, after the
main metamorphic events, generated major low-angle
normal faults that separate the main metamorphic complexes.
Although a wide variety of tectonic models have
been proposed for this setting, most of them are related to
delamination or to subduction with associated roll-back.
During the late Miocene, the relatively flat and low relief
of the continental crust facilitated the accumulation of
sedimentary deposits, which are interlayered with volcanic
rocks in the eastern Betic Cordillera and Alborán
Sea. The continuous Eurasian-African convergence
finally produced regional uplift since the late Miocene
and the development of large late regional E-W to
NE-SW folds, which determine the main reliefs.
Lateral spreading forms when fractured rocks or soil mass slide slowly over a softer underlying material. In this work, we studied two cases, one in the south of Spain and other in the north of Tunisia. Both are rock spreadings and occur along shear or tensile fractures. These mass movements involve in almost all cases rocks and occur along shear or tensile fractures
Gold of alluvial origin is found in Granada (SE Spain), occurring as fine, millimetre- to centimetre-sized plates. It has been panned in the Genil and Darro rivers since Roman times, and was also mined in the conglomerates of the 'Alhambra Formation'. The 'Alhambra Formation' is an alluvial-fan deposit, up to 200 m thick, of lower Pliocene age (~5 My). The area of the mine corresponds to a poorly-sorted, well-rounded conglomerate, with clasts of metamorphic rocks. The mine is Roman and was exploited using the 'Ruina Montium' method: a huge scar on top of the hill, from which the man(Roman)-induced landslide started, can still be recognized. This mine, with an average gold content of 0'5 gr/m3, was worked again between the years 1875 and 1877 by a French company: they dismantled the gold-bearing conglomerate using a powerful water jet, and separated the gold by amalgamation with mercury. The origin of the gold is closely related to that of the 'Alhambra Conglomerate', which comes in turn from the erosion of an older, Miocene conglomerate. The source rocks for the latter are those of the metamorphic Sierra Nevada core. Gold concentration took place during successive processes of erosion, transportation and deposition (sedimentary cycles). The Miocene conglomerate formed first; then the 'Alhambra Conglomerate', and, finally, the placer-deposits linked to the Genil and Darro rivers. Gold has been panned exclusively in these rivers at those places where they cut across the 'Alhambra Conglomerate'.
Zooxanthellate-coral (z-coral) generic richness values from 102 Oligocene–Miocene localities from the Mediterranean and adjacent areas are tested in this paper as a proxy for relative palaeotemperatures, essentially using the quantitative relationship between taxonomic richness and prevailing seawater temperature underlined by the so-called “energy hypothesis”. Patterns of generic richness and inferred palaeotemperatures are examined for each stage of the Oligocene–Miocene time interval and compared with some global palaeoclimatic curves based on oxygen stable-isotopes. Except for the Mid- Miocene Climatic Optimum, which is not recorded in the generic richness of the Mediterranean z-coral communities, the coral-richness-derived palaeotemperatures correlate well with the general palaeoclimatic trends shown by the isotope curves. Results also show: (1) a gradual increase of temperature from the early to the late Rupelian; and (2) a gradual widening of the temperature range after the Burdigalian. The latter indicates that z-coral communities were able to maintain themselves in the region by progressively adapting to a wider temperature range from the mid-Miocene onwards to the Messinian, as the Mediterranean was migrating northward. Although limitations and biases are underlined and discussed in the paper, the “energy hypothesis” applied to fossil z-coral faunas appears to offer a powerful method when used at global or regional scales to estimate changes in palaeotemperatures. It holds particular promise for time intervals and regions where conventional isotopic data are lacking, such as the Oligocene and Miocene of the Mediterranean.
During the Oligocene–Miocene Greenhouse-to-Icehouse climatic transition, the biogeography of reef corals or zooxanthellate-like scleractinian corals was gradually changing from a pan-tropical Tethyan Province in the Eocene to three reef-coral Provinces of the Western Atlantic–Caribbean, Indo-Pacific and Mediterranean. Our REEFCORAL database encompasses updated and homogenized data on paleoenvironmental and systematics of scleractinian corals occurring in the Oligocene and Miocene outcrops from circum-Mediterranean regions, provided by most of relatively recently published data in the literature and by the study of published and unpublished collections of coral specimens from the same area, including the important collections housed at the MNHN (Paris) and our own collections. As there is no validated direct criterion for the identification of the coral-zooxanthellate symbiosis in the fossil record, and considering the difficulty to use the biogeochemical approaches in the context of this study, the subjectivity of the morphological criteria and the relative recent age of the fossil corals we are dealing with, a uniformitarian approach has been used for inferring the symbiotic status of scleractinian genera in REEFCORAL. Among the 158 genera included in our database, 93 can be considered as zooxanthellate and 10 have a doubtful zooxanthellate status. This relatively exhaustive database was used to reconstruct the temporal and spatial distribution of scleractinian corals in the Mediterranean during the Oligocene–Miocene time in order to discuss the interplaying effects of the global cooling at that time, the re-organization of the Tethyan realm resulting from the African, Arabian and Eurasian plate collision and the emergence of the Alpine chains, driving the gradual northward movement of the whole region outside the tropical/subtropical belt.
During the Oligocene and Miocene, shallow-water carbonates of the Mediterranean region were rich in scleractinian corals thriving within various depositional settings, including different reef types. Their diversity patterns, although related to a complex interplay between a suite of environmental factors and palaeobiogeography, are considered to be strongly controlled by climate variability and changes in sea-surface water temperature.By using the quantitative relationship between present-day coral taxonomic richness and prevailing sea-water temperature, underlined by the so-called “energy hypothesis”, we test zooxanthellate-coral generic richness values from a selection of 102 Oligocene–Miocene localities of the Mediterranean region as a proxy for relative palaeotemperatures.For each Oligocene–Miocene stage, generic richness values per z-coral site are firstly examined, together with variations of the Mediterranean z-coral generic pool. For better testing the method and assessing its potential application, patterns of generic richness and inferred palaeotemperatures are then compared with global palaeoclimatic curves based on marine oxygen stable isotopes data or other climate proxies, such as palaeoclimatic records from European continental floras and from fossil coral linear extension rate.Results clearly show that fluctuations of coral richness-derived palaeotemperatures correspond relatively well with global changes of sea-water temperature especially for the entire Oligocene, the Chattian–Aquitanian boundary and the Late Miocene. The well known Mid-Miocene Climatic Optimum, however, is not recorded, suggesting that regional factors, acting together with important palaeogeographical changes, exerted a strong control on the generic richness of Mediterranean z-coral communities.A remarkable decline of taxonomic richness is recorded after the Burdigalian, together with a gradual decrease of palaeotemperatures in the region. From the Middle Miocene onwards to the Messinian, however, an increase in the temperature range of z-coral localities is clearly visible, indicating that z-coral communities were able to thrive and adapt to a wider temperature range, as the Mediterranean was gradually migrating northwards, outside the tropical belt.The “energy hypothesis”, if used at global or regional scale, can be considered a promising and reliable method for estimating Cenozoic palaeotemperatures, from coral or other suitable fossil assemblages of shallow-water carbonates.
Many Tertiary species of Crassostrea appear to have inhabited shallow-marine environments where they produced extremely large and thick shells. In contrast, living Crassostrea species are restricted primarily by marine predation to brackish, hypersaline, and intertidal environments where they produce comparatively smaller and thinner shells. If Crassostrea populations have used estuarine environments as a refuge from predation since the Cretaceous, then their presence in fully marine environments after the Cretaceous is puzzling. In order to interpret differences in environment and shell size, I examined the paleoecology and sclerochronology of two marine and two estuarine populations. Results are consistent with the hypothesis that thicker shells in Tertiary Crassostrea titan deterred increased exposure to fully marine predation. Life spans and growth rates estimated from annually formed growth increments show that C. titan grew significantly faster in shell thickness, as well as lived two to three times longer, than Quaternary Crassostrea virginica. Similar or lower valve-height growth rates in C. titan, as well as thinner shell walls in the attachment area, are consistent with exposure to marine predation, but not with alternative factors, such as higher salinity or alkalinity. Thicker valves in C. titan resulted from the successive addition of chalky deposit layers, in contrast to C. virginica valves, which contain significantly less of this unusual shell structure. A high incidence of incomplete drill holes in juvenile C. titan shells demonstrates that their thick valves were successful in deterring muricid predation. The association of C. titan with other large suspension feeders (barnacles and pectenids), as well as with phosphatic-pellet sediments, suggests that elevated planktic productivity may have supported this reefal community and enabled C. titan to grow thicker shells. The occurrence of both shallow-marine and estuarine Crassostrea since the Cretaceous raises the possibility that estuaries have served as refugia from which populations have dispersed into fully marine environments multiple times through the Cenozoic.
The Geosites Project, initiated by the IUGS Global Geosites Working Group and supported by UNESCO, aims to produce a global inventory of the Earth's geo-logical heritage. This global inventory requires a sys-tematic methodology, based on the selection of geologi-cal frameworks of international significance in each country. These frameworks are topic events, temporal or regional geotectonic elements, etc. The second step of this methodology is the selection of the most valuable and representative sites of these geological frameworks (geosites). Fortunately, the geological diversity of Spain provides a great number of frameworks of global signif-icance. In addition, the high quality of the outcrops (for topographic and climatic reasons) will allow for the selection of illustrative geosites. This paper presents a list of Spanish geological frameworks drawn up by con-sensus. It was prepared in accordance with the Geosites Project methodology, without taking into account the National Inventory of Geosites, which is in progress and covers 40% of Spanish territory. The IGME (Geological Survey of Spain) drew up a preliminary list, which was sent to all the university departments of geology, mining schools and research centres, for analysis, discussion and improvement. The result of this request was the selection of 20 frameworks, forming the first Spanish contribution to the Geosites Project.
We investigated gneisses from the upper sequence of the Nevado-Filábride Complex in the western Sierra Nevada, close to the contact with the Permo-Triassic Alpujárride Complex. Despite intense deformation, the occurrence of skarn-like lenses (epidote + amphibole + garnet + quartz) and abundant post-magmatic hydrothermal tourmaline in both the gneisses and adjacent metasediments strongly suggests that an originally intrusive contact is preserved. High-pressure assemblages are not preserved in the dated gneisses due to intense retrograde overprinting during exhumation. Nevertheless, thermobarometry performed in adjacent skarn rocks and metapelites indicates maximum temperatures and pressures ranging from 605 ± 74 to 715 ± 72 °C and from 11.0 ± 2.5 to 14.5 ± 2.5 kbar. SHRIMP ion microprobe U-Pb analyses were performed on zircons from one gneiss. The zircon crystals display igneous oscillatory-zoned domains, with an age of 301 ± 7 Ma (95% c.l.), rimmed by dark, unzoned overgrowths of metamorphic origin (mean age of 16.5 ± 0.4 Ma). The former age is interpreted as dating the crystallisation of the granitic protolith of the gneiss. This implies a pre-Permian age for the Nevado-Filábride marbles, traditionally considered to be Triassic, and a Palaeozoic age for the complete sequence of the upper part of the Complex. Accordingly, in western Sierra Nevada, the observed succession from the Nevado-Filábride Complex to the Alpujárride Complex (Permo-Triassic phyllites and Triassic marbles) can be considered normal from a stratigraphic point of view. Therefore, the present-day contact between the two complexes, the Mecina Fault in Sierra Nevada, is interpreted as a normal fault generated during exhumation rather than a thrust structure. The age of the metamorphic zircon overgrowths (16.5 ± 0.4 Ma) is likely to be related to de compression, as suggested by titanite inclusions found in zircon. Titanite postdates rutile, the high-pressure Ti-rich phase. This indicates exhumation of the Nevado-Filábride Complex significantly after the Alpujárride Complex (∼18 Ma).
Coralline red algae are common in Oligocene and Miocene marine shallow-water carbonate and siliciclastic rocks, as well as deep-water re-deposited sediments containing particles removed from platforms. Corallines are mostly reported in reef-related carbonates but are also the main components in shallow-water heterozoan carbonates from temperate regions. The known distribution of Oligocene coralline assemblages does not suggest any palaeobiogeographical differentiation. In contrast, for the Miocene, the occurrence of taxa still living today with restricted geographic distribution supports an actualistic approach and the rough differentiation of palaeobiogeographic regions as follows: (a) a tropical region (characterised by thick Hydrolithon plants and Aethesolithon); (b) a subtropical Mediterranean (with common Spongites and Neogoniolithon species); and (c) a temperate region with shallow-water assemblages dominated by Lithophyllum.In a few examples from the northern margin of the western Tethys, the correlation of Oligocene carbonate-facies and algal assemblages indicates a dominance of Lithothamnion species in the shallower environments, while Mesophyllum is most abundant in deeper platform settings. The taxonomic composition of Miocene coralline assemblages and growth forms changes with depth, having patterns similar to those in the algal associations in present-day marine platforms. Mastophoroids and lithophylloids (Aethesolithon, Hydrolithon, Neogoniolithon, Spongites, and Lithophyllum species) characterize the shallower assemblages, whereas the melobesioids Lithothamnion and Mesophyllum and the sporolithacean Sporolithon are dominant in deeper-water settings. The common algal nodules (rhodoliths) comprise thick plants of few species in the shallowest palaeoenvironments, while in deeper platform areas they are composed of more diverse algal assemblages, with thin encrusting and protuberant-branching growth forms.
The Alhambra (14th century AD) in Granada (southeast Spain) is built at the summit of a Pliocene to Lower Pleistocene conglomeratic formation. Tens of small-scale normal faults crop out along the northern hillslope of the Alhambra, which have a N130–N150°E strike, dipping 65–75° mostly to the southwest. These are closely spaced faults (approximately 5–30 m) with centimetre to several metre displacements. Several topographic steps in this area coincide with hectometre- to kilometre-scale faults with the same kinematics as the small-scale ones. Some of these faults appear to be active and related to the present seismicity detected in this region, and associated with the cracks and other damage observed in the Alhambra. Several focal mechanisms calculated in this study are in accordance with the dominant NW–SE orientated normal faults. We interpret that the topographic steps of these faults are a consequence of repeated earthquakes during the past 800 ka. The last large earthquake of approximately 5.1 magnitude in this area occurred in 1431, destroying the Alixares Palace, the Arabian fence and part of the Alhambra wall. We consider the seismic risk associated with these faults to be moderate, as the displacement is partitioned into several hectometre- to kilometre-scale faults. Copyright © 2004 John Wiley & Sons, Ltd.
The Neogene Osmaniye-Bahçe sub-basin and neighbouring sub-basins of the same age (İskenderun-Arsus-İA, Hatay-Samandağ-HS)
are located near the triple junction of the Anatolian, African and Arabian plates in the easternmost part of the Mediterranean
region, (Bay of İskenderun, southeastern Turkey). These sub-basins are surrounded by the Misis Uplift to the west, the Taurus
Mountains to the north, the Amanos Uplift to the east and the Karataş-Osmaniye Fault, a segment of the East Anatolian Strike-Slip
Fault, to the southwest. Strike-slip tectonics strongly affected Neogene and pre-Neogene sediments of the area. The first
marine transgression took place in the Middle Miocene that resulted in the deposition of patch reefs with minor siliciclastic
input in the local lagoons and shoals. Shallow shelf areas over the topographic highs provided suitable hard substratum for
the colonization by corals and other reef builders. The patch reefs, i.e., the Horu Formation, mainly comprise reef cores
and flanks. The reef cores are lenticular, massive bodies characterized by corals in in situ growth positions that are of
thin to thick branching, massive domal and platy morphologies, while reef flanks and peri-reefal areas are mainly composed
of reworked coral blocks and bedded biogenic limestones. In the early Late Miocene, the reefs prograded across the shelf margin
due to sea level rise and then were gradually replaced by deltaic sediments (Kızıldere Formation). The early phase of deltaic
deposition is represented by vertical and lateral transitions with lagoon-estuary sedimentary systems and small-scale Ostrea reefs associated with carbonate and siliciclastic interbeds. The most important controlling factors for the sedimentation
in these sub-basins were antecedent topography, clastic input, sea level changes and syn-sedimentary tectonics.
KeywordsNeogene–Reefal limestones–Osmaniye-Bahçe sub-basin–SE Turkey
Defined here as ‘essentially in place calcareous deposits created by sessile organisms’, Organic Reefs are diverse and complex structures with a long geological history. Their classification has been the subject of fierce debate, often characterized by reliance on subjective features such as wave-resistance and qualitative attempts to discriminate between ‘first’ and ‘second class’ reefs. In contrast, emphasis is here placed on the objective characteristic of the type of sedimentary support, which largely determines the sedimentary composition of the deposit.
Pollen analysis of sections spanning the Middle Miocene (Langhian and Serravallian) from southern Spain to Switzerland has been carried out with the aim of reconstructing the existing latitudinal environmental gradient.Floral assemblages indicate a tropical–subtropical to warm–temperate climate for the entire area during the Middle Miocene. The presence, in all pollen spectra, of taxa with high temperature requirements demonstrates that the latitudinal gradient in temperature was relatively low. The development of a diverse subarid flora in southern Spain including Neurada, Lygeum, Prosopis, Calligonum, Nitraria, Caesalpiniaceae, etc., points to a very dry climate with a marked seasonality. These features clearly indicate that a very warm and dry climate (i.e. a steppe environment) was already present during the Langhian in the northwestern Mediterranean area. On the other hand, milder conditions are progressively inferred towards the north as subdesertic elements gradually disappeared and taxa with higher water requirements increased. The latter dominates the pollen assemblages in the eastern central part of France and Switzerland, thus precipitations would have been evenly distributed throughout the year. We interpret this gradient from subdesertic vegetation in the south to humidity-adapted plant environments in the north as the result of a latitudinal gradient in precipitation.
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