Content uploaded by José M. Martín
Author content
All content in this area was uploaded by José M. Martín on Nov 05, 2019
Content may be subject to copyright.
Sierra Nevada: Historia del levantamiento de un relieve deducida de las unidades conglomeraticas de su borde
... From the late Tortonian onward, these basins became progressively isolated until they reached their current geographical location (Montenat et al., 1990;Sanz de Galdeano, 1990;Vera, 1991, 1992;Sanz de Galdeano and Alfaro, 2004;Krijgsman et al., 2006;Corbí et al., 2012). Most of these basins opened directly to the Mediterranean tectonic activity took place at the northeastern (Sierra Arana) and eastern (Sierra Nevada) edges of the basin (Fig. 2) which produced significant amounts of terrigenous sedimentation at the base of the uplifted areas (Martín and Braga, 1997;Braga et al., 2003;Rodríguez-Fernández and Sanz de Galdeano, 2006). During this period the margins of the basin acquired similar contours to those observed today, although the basin remained open seawards to the south and west (Braga et al., 1990). ...
... Later, during the Pliocene and the Quaternary, sedimentation was limited to small, fault-controlled, highly-subsident depocentres (Morales et al., 1990). Pliocene-Quaternary materials comprise several detrital (mostly conglomeratic) continental formations separated from one another by unconformities (Dabrio and Fernández, 1986;Fernández et al., 1996;Martín and Braga, 1997;García-Alix et al., 2008b). ...
... This Formation has been interpreted as comprising sediments related to coalescent alluvial fans fed from the sierras located north and east of the Granada Basin. Its age is Pliocene to Early Pleistocene (Aguirre, 1957; Rodríguez-Fernández et al., 1989; Martín and Braga, 1997; Gü nter and Skowronek, 2001). ...
... The geometry of the extensional fault-system (Fig. 2), together with the fact that most of the seismicity is located in the flat area of the Granada Depression (Fig. 3), suggest that the main locus of extension has migrated basinwards since the Tortonian. The stratigraphical architecture of the border of the Granada Basin also points to a basinwards migration of sedimentation (Martín and Braga, 1997) and accordingly also of the extensional front. Thus, the migration of the extensional front basinwards has exhumed the footwalls of older faults, uplifting the Tortonian rocks, which presently crop out in ranges along the margins of the basin. ...
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.
... Terrigenous material shed from upland fed localised fan deltas around Sierra Nevada. The clasts in these fan deltas indicate that the Alpujárride Complex was still the only basament complex at the surface in the western Sierra Nevada (Rodríguez-Fernández, 1982;Martín and Braga, 1997) (Fig. 6). ...
... Several Subbetic upland areas were already emerged (Rodríguez-Fernández, Fig. 6. Erosion pulses of western Sierra Nevada and stratigraphic architecture of the corresponding conglomerate units (modified from Martín and Braga, 1997). 1982) and islands rimmed by shallow-water marine platforms replaced the former deep-water trough in the North Betic Straits (Soria, 1993). ...
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.
... During the late Tortonian (8.3 to 7.3 Ma) major tectonic activity took place in the north-eastern and eastern highland edges of the basin (Sierra Arana and Sierra Nevada,Figs. 2,3), leading to the deposition of significant quantities of terrigenous sediments at the base of the uplifted areas (Braga et al., 1990(Braga et al., , 2003Martín and Braga, 1997). Marine conditions prevailed and skeletal carbonate sediments accumulated in siliciclastic-free areas on platforms all around the margins of the basin. ...
... Initially, the basin was a marine embayment connected to the Atlantic Ocean to the northwest (Martín et al. 2014) and to the Mediterranean Sea to the south and west (Braga et al. 1990). From 8.3 to 7.3 Ma, major tectonic activity took place in the northeastern (Sierra Arana) and eastern (Sierra Nevada) highland edges of the basin (Fig. 2), resulting in the deposition of significant amounts of conglomerates at the base of the uplifted areas (Braga et al. 1990(Braga et al. , 2003Martín and Braga 1997). Skeletal carbonates accumulated in siliciclastic-free areas on platforms around the marine-basin margins. ...
The Granada Basin is a small (50 × 50 km) Neogene intramontane basin located in the central part of the Betic Cordillera (Spain). In the latest Tortonian, the Granada Basin desiccated and a thick salt succession formed, encompassing three halite- bearing units: the ‘Lower Halite Unit’, the ‘Intermediate Sandstone Unit’ (ISU), and the ‘Upper Halite Unit’ (UHU). ISU deposits record the onset of marine to non-marine conditions in the Granada Basin. The main purpose of this paper is to study the environment of formation and the diagenetic evolution of the ISU salt-bearing unit, in order to assess the events leading to and resulting from the continentalization of this basin in the late Miocene. This study includes visual core descriptions, petrographic (conventional petrography and scanning electron microscopy), and geochemical (δ34S and δ18O and 87Sr/86Sr) analyses. ISU deposition took place in a coastal lake, isolated from the open sea by a sand barrier. Lake evolution was from a very shallow, hypersaline lacustrine environment to a deeper, perennial lake undergoing frequent storm-induced marine flooding and, finally, to a shallower, perennial saline lake. Isotope analyses point to a mixture of different inflow waters, including marine- and underground (hydrothermal)-water inputs for the origin of the brines. Halite dissolution occurred after flooding events and clear-halite cement was precipitated inside primary-halite dissolution cavities. Early diagenesis involves halite re-crystallisation during repetitive, dissolution–precipitation cycles, gypsum replacement by halite, halite replace- ment by nodular anhydrite, and framboid pyrite formation. Intermediate- to late-diagenetic processes are silica (megaquartz, chalcedony, and lutecite) replacement of halite and anhydrite, and celestine replacement. Megaquartz formation relates to sulfate-depleted, UHU percolating brines. Chalcedony and lutecite crystallization took place sometime later from sulfate- rich percolating brines, during deposition of the gypsum sequence occurring on top of the salt. Celestine, replacing lutecite, resulted from the interaction with Sr-rich underground waters (via dissolution of previously formed celestine).
... Este valor medio en la incisión vertical en el tramo bajo del río Darro de 1,05 cm/año, en el periodo 1890-2010, cabe compararlo con otros datos de referencia existentes en la bibliografía. Es este sentido, Azañón et al., (2007) citan valores de encajamiento de la red fluvial de Granada (en este caso en referencia al río Genil, cauce donde desemboca el río Darro) entre 0,02 y 0,04 cm/año teniendo en cuenta para ello la profundidad del valle y una edad en el inicio del encajamiento fluvial en el borde Este de la depresión de Granada estimada en el Pleistoceno medio (en torno a 0,5 millones de años), correspondiente a la edad de los últimos depósitos sedimentarios situados en los abanicos aluviales de La Zubia (Martín y Braga, 1997). ...
In this paper, the average rate of the river Darro incision (Granada, Spain) is calculated over the historical period 1890-2010 in the urban section (Alhambra-Valparaiso sector). This has been used historical photographs that this river appears, from which it has been possible to determine the position of the channel at the time when the photographs were made. Comparison with the current scenarios has identified the height difference of the channel through absolute coordinates measures undertaken by theodolite. This methodology has allowed quantitatively estimate an index of mean vertical engagement of the river for the data collection time of 1,05 cm / year.
... These are normal faults, mostly SW-dipping ( Fig. 1). Migration of the extensional front basinwards has exhumed the footwalls of older faults, uplifting the Tortonian rocks, which presently outcrop in ranges along the margins of the basin (Martín and Braga, 1997). This migration of the mountain front also involved the Pliocene and Quaternary sediments, which presently constitute uplifted blocks in the eastern and northeastern borders of the Basin (Fig. 1). ...
The City of Granada is placed at the margin of a flat area known as the Granada Basin (Betic Cordillera, SE Spain) surrounded by mountains. The seismic activity in the Granada Basin is high, with a large number of earthquakes, all of them of moderate to low magnitude (mb ≤ 5.5). Historically, earthquakes in this area have produced important material damage and human casualties; however, it is hard to evaluate their magnitude. Seismicity has its origin mostly at depths between 5 and 17 km and the focal mechanisms indicate a present stress field dominated by a tensional tensor with an associated NE-SW extensional axis. The sedimentary cover of the Granada Basin is mostly coeval with the activity of faults that bound the basin, which have controlled the stratigraphic architecture. These faults are normal, mostly with a NW-SE orientation, and dipping towards the SW. Basinwards migration of the extensional front has exhumed the footwalls of older faults, uplifting the previous Tortonian sedimentary cover, which presently outcrops as emerged ranges at the margins of the basin. This work presents preliminary results of a paleoseismic study of the Granada Fault, an NW-SE active normal fault that produces a Plio-Quaternary throw of 300 m. According to these data, slip rate has been estimated in 0.38 mm/yr. Several paleosoils, Pleistocene in age, have been affected by this fault. These paleosoils were sampled and dated using the thermoluminiscence method to constrain these estimates. Three different seismic events can be recognized from the accumulative throw. The vertical slip per event ranges from 5 to 7 cm. Following empirical relationships, a moment magnitude between 5.9 and 6.0 can be preliminary assessed for these events.
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.
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'.
ResearchGate has not been able to resolve any references for this publication.