a strike slip fault corridor within the alpujarra mountains betic cordilleras spain in a long corridor in the internal zone of the betic cordilleras bounded to the north by the sierra nevada and to the south by the sierras lujar contraviesa and gador two discernible bands of strike slip faults exist these bands lie in an approximately e w direction and are well exposed throughout and beyond the 85 km long belt the characteristic features of strike slip faults such as cataclastic rocks composed of variously textured fault breccia which also include fragments of rocks up to several metres in size incipient foliation and striation demonstrate the right lateral nature of the displacement there are also fractures which run in a nw se and nne ssw direction and apparently originated after formation of the e w faults the magnitude of lateral displacements is difficult to calculate evidence of considerable vertical movement can be found locally these strike slip displacements have essentially occurred since the middle miocene period and might still be taking place

geology and tectonics of the betic zone se spain abstract the southern margin of the iberian continent comprises a complex geological history which can be traced back into the proterozoic when a gneissic basement was formed a cover of nevado filabride rocks was deposited onto this proterozoic basement during the palaeozoic the permian intrusion of the bedar granite suggests that the palaeozoic sedimentary rocks now exposed in the betic cordilleras have been affected by the hercynian orogeny similar to that of palaeozoic rocks in the adjoining ossa morena zone the hercynian basement was probably covered by alpujarride carbonates in the mesozoic when rifting opened tethys and intruded 140 ma old basic dyke swarms the palaeozoic basement of the betic cordilleras comprises a suture of late cretaceous subduction 80 85 ma b p this can be inferred from hp lt metamorphic facies obducted in coeval thrust slices of nevado filabride rocks the nevado filabride nappes include mesozoic carbonates transformed into marbles macael the suture was probably annnealed after the closure of tethys the mesozoic boundary between africa and europe and the rifting in tethys ceased during the palaeogene when the atlas mountains were formed 36 ma b p subsequently relative movements between africa and europe in the neogene were accommodated by strike slip faults these define the iberian microplate moving eastward by atlantic spreading and possibly subducting under italy neogene deformation of iberia is most intensive in southeastern spain due to emplacement of a mantle diapir under the alboran area this occurred early in the neogene aquitanian and caused nappe spreading involving alpujarride and malaguide rocks the subsequent neogene history has now been studied in great detail and is reviewed here it involves clear examples of calc alkaline volcanism most probably not related to subduction seismic motion along strike slip faults within the iberian microplate and syntectonic deposition in intermontane neogene basins

early carboniferous carbonate systems an alternative to the cainozoic paradigm abstract an alternative model for carbonate deposition is offered for the early carboniferous the major features of this interval are not explained using late cainozoic analogues early carboniferous low latitude shallow seas were apparently strongly influenced by upwelling and high nutrient levels these conditions favoured highly carbonate productive offshore systems but also resulted in the formation of extensive abiogenic carbonates as muds and ooids if correct the carboniferous serves to illustrate the dangers in extrapolating from present day systems to the geological record

drowning of algal mounds records from the upper carboniferous lower pseudoschwagerina limestone carnic alps austria abstract anthracoporella algal mounds up to 22 m thick occur within the cyclic sequences of the lower pseudoschwagerina limestone uppermost carboniferous carnic alps austria their depositional environment lay between the wave base and the base of the photic zone the algal mounds are overlain by dark well bedded cherty wackestones and packstones the cherty limestones contain cephalopods thick shelled brachiopods and sponge spicules and lack anthracoporella in growth position they are typical deeper water sediments deposited below the photic zone this sequence records drowning episodes the shallow water algal mounds were drowned by relative rise of sea level as sea bottom production shut down below the photic zone the sedimentological and paleontological evidence of drowning are supported by geochemical data of two measured sections the mean sulfur content of the well oxygenated algal limestones is 0 02 for both sections the toc values are 0 17 for the section ai and 0 10 for the section ar the s contents of the cherty limestones are approximately twice as high with values of 0 48 and 0 05 for the respective sections toc values of the cherty limestones are also significantly higher with 0 30 and 0 51 contents for the respective sections the cherty limestones document the termination of the mounds and the demise of reef building algae in each cycle this interval is therefore termed shroud facies the rapid sea level rise reported is a further proof for high magnitude sea level fluctuations in intervals of glacio eustasy the documented drowning mode is novel through the definable interval of drowning the repeated events during a short time interval the full record of pre syn and post drowning deposits and the unequivocal attribution to glacio eustatic sea level rise this mode seems to be characteristic of an icehouse period and clearly differs from the drowning mode in greenhouse periods which is often gradual lacks an unequivocal cause and is often preceded by subaerial exposure

lineated valley fill lvf and lobate debris aprons lda in the deuteronilus mensae northern dichotomy boundary region mars constraints on the extent age and episodicity of amazonian glacial events abstract in order to assess the nature degradational processes and history of the dichotomy boundary on mars we conducted a detailed morphological analysis of a 70 000 km 2 region of its northern portion north central deuteronilus mensae south of lyot in the vicinity of sinton crater this region is characterized by the distinctive sinuous 2 km high plateau scarp boundary outlying massifs to the north and extensive fretted valleys dissecting the plateau to the south these features represent the first order modification and retreat of the dichotomy boundary and are further modified by processes that form lineated valley fill lvf in the fretted valleys and lobate debris aprons lda along the dichotomy scarp and surrounding the outlying massifs we use new high resolution image and topography data to examine the nature and origin of lvf and lda and to investigate the climatic and accompanying degradational history of the escarpment on the basis of our analysis we conclude that 1 lvf and lda deposits within the study region are comprised of the same material show integrated flow patterns and originate as debris covered valley glaciers a significant amount of ice hundreds of meters is likely to remain today beneath a thin cover of sublimation till 2 there is depositional evidence to suggest glacial highstands at least 800 m above the present level implying previous conditions in which the distribution of ice was much more widespread this is supported by similar deposits within many other areas across the dichotomy boundary 3 the timing of the most recent large scale activity of the lda lvf in this area is about 100 500 million years ago similar to ages reported elsewhere along the dichotomy boundary 4 there is evidence for a secondary but significantly limited phase of glaciation the deposits of which are limited to the vicinity of the alcoves similar later phases have also been reported elsewhere along the dichotomy boundary 5 modification of the fretted valleys of the dichotomy boundary has been substantial locally but we find no evidence that the amazonian glacial epochs caused retreat of the dichotomy boundary of the scale of tens to hundreds of kilometers our findings support the results of an analysis just to the east of the study region and of studies carried out elsewhere along the dichotomy boundary that find further evidence for the remnants of debris covered glaciers and extensive valley glacial land systems

a mid ordovician temperate carbonate shelf the black river and trenton limestone groups of southern ontario canada abstract mid ordovician limestones of southern ontario are usually considered to be tropical shelf limestones and interpreted using facies models derived from recent tropical carbonate environments nevertheless depositional rates grain types faunas erosion surfaces mineralogy and geochemistry are more compatible with a temperate or even cold shelf environment in view of the low latitudes 20 s indicated by paleomagnetism this suggests deposition in relatively cold seas deposition below a tropical thermocline or that the paleomagnetic data are wrong similar features in other caradocian limestones of eastern north america show that these inferred cooler conditions were widespread if deposition occurred below a tropical thermocline most shallow water caradocian limestones must be re interpreted as deeper water deposits more likely in view of the evidence for temperate conditions in shallow water is that the whole eastern seaboard of north america was affected by cold currents arising from southern polar ice caps and thus was a temperate shelf environment

palaeostress analysis of the northern nijar and southern vera basins constraints for the neogene displacement history of major strike slip faults in the betic cordilleras se spain this paper presents the results of a detailed structural analysis of the northern nijar and southern vera basins with special emphasis on the evolution of the regional stress field and the associated timing of movement of the serrata gafarillos and palomares strike slip fault zones these major fault zones control the neogene deformation of the se internal betic cordilleras in spain detailed stress analysis on neogene sediments of the vera and nijar basins shows a strike slip regime with nw se oriented subhorizontal maximum principal stress 1 during tortonian and earliest messinian times under the influence of this stress field dextral displacement along the n090e trending gafarillos fault zone resulted in deformation of the sediments of the southern sorbas and northeastern nijar basins during the early messinian a clock wise rotation of the stress field occurred stress analysis in rocks with late early messinian up to quaternary ages in the nijar and vera basins indicates a strike slip regime with n s oriented subhorizontal maximum principal stress 1 under the influence of this stress field the main activity along the n010e striking palomares strike slip fault zone took place resulting in deformation of the neogene sediments of the southeastern vera basin and culminating in a maximum sinistral displacement of more than 20 km at the same time the stress field was not suitably oriented to exert a large shear component on the gafarillos fault zone which activity ended after the earliest messinian fault and outcrop patterns of syntectonic neogene sediments in the vera basin show that displacement along the palomares fault zone decreased at the end of the middle miocene although minor displacement phases may still have occurred during the late miocene and possibly even pliocene from the middle miocene onward deformation in the nijar basin was controlled by sinistral displacement along the n040e trending serrata strike slip fault zone

neotectonics and morphotectonics of the southern almeria region betic cordillera spain kinematic implications most previous studies related to the recent tectonic development of southeastern betic cordillera and in particular the south of almeria agree with the kinematic variety that can be observed in the post miocene structures at different scales this variety is difficult to explain if we consider only the regional stress field related to the convergence of the eurasian and african plates that remained relatively steady over the last 9 ma this work proposes a block tectonics with horizontal and vertical relative movements driven by strike slip movements of major faults to explain the variety of kinematics observed in the area from middle miocene to present the combined activity of the alpujarras fault zone dextral strike slip and the carboneras fault zone sinistral strike slip induces within the major block bounded by them the squeezing of minor pre existing fault bounded crustal blocks this process generates traction areas inside the escaping block which are linked with the existence of gradients of westward movement rate this tectonics can explain some of the structures related with the extensional tectonics predominant in the south of almeria province and the development of the minor and major morphostructures driven by faults with different kinematics the tectonics of blocks proposed is useful to give a coherent interpretation of apparently incoherent local structural data into a regional and homogeneous compressional stress field

hydrogeochemical processes in an arid region of europe almeria se spain abstract in the lower andarax river basin 3 aquifer units have been defined namely the carbonate aquifer the deep aquifer and the detrital aquifer which between them contain a wide variety of water types identification of hydrogeochemical processes has been performed by studying a series of ionic ratios comprising the principal constituents together with b and li cl vs so4 cl vs mg cl vs li b vs li among the processes detected the circulation of groundwaters with high concentrations of so4 was found to have significant effects moreover in the coastal region naturally occurring processes related to the flushing of saline waters from sediments of marine origin occur in conjunction with others clearly of human origin that are related to saltwater intrusion a further factor is the entry from overlying deposits of waters with a high saline content this salinity is related to the flushing of sediments of marine origin the use of b and li together enables waters in which salinity is related to seawater to be distinguished from others in which salinity is related to evaporitic layers or to thermal areas the concentration of li is directly related to water temperature while that of b is greater in the most saline sectors of gypsiferous and or seawater origin

tectonic significance of the present relief of the betic cordillera abstract tortonian calcarenites of the betic cordillera were deposited in coastal or very shallow marine environments and represent an ideal marker for estimating vertical movements from the late miocene to the present a map showing the heights at which these tortonian marine rocks are situated has a clear correlation with the present relief indicating that today s relief has been formed since the tortonian there is also a good correlation between present relief and the bouguer anomaly distribution in the betic cordillera as well as with crustal thickness likewise the present relief is directly related to the geodynamic setting of a horizontal n s to nnw sse compression and an almost perpendicular extension along with isostatic readjustment existing in the betic cordillera from the tortonian as a result of these regional stresses faults and folds have produced notable vertical movements the highest rates of uplift of the betic cordillera coincide with large antiforms in particular those of the sierra nevada and the sierra filabres several subsiding sectors also exist for example the granada basin or the guadalquivir basin the foreland guadalquivir basin has a complex history because the uplift in its eastern sector and subsidence in the western sector coexisted during the late tortonian today the whole betic cordillera is characterized by differential regional uplift even in the aforementioned subsiding sectors

syn tectonic sedimentation in a neogene strike slip basin containing a stacked gilbert type delta se spain abstract the pliocene sedimentation in the cerro blanco ei barranquete subbasin cbb subbasin that forms part of the larger almeria nijar carboneras basin anc basin is controlled by a releasing overstep and a restraining zone in the ne trending serrata strike slip fault zone the sedimentary development of this subbasin can be considered in three stages of a fault kinematic model during stage i a wave influenced shoaling zone was present in front of an emergent serrata cape to the ne with a basin to the sw and w uplift of the shoaling zone in a restraining n080e trending cerro blanco fault zone cb fault zone is evidenced by the following syn tectonic sedimentary phenomena a a rotational unconformity towards the nw b four deepening pulses in the shallow water zone c massflow deposits originating from a near coastal zone possibly triggered by tectonic pulses during stage ii the uplifted zone became increasingly shallow and finally emerged quartz pebbles in the sediments that indicate a land connection between the serrata cape and the metamorphic basement in the north differentiate this stage from the previous one prograding shoreline deposits marked the outbuilding of the serrata cape towards the sw an episodically subsiding zone due to a releasing overstep between the sinistral n040e trending nw serrata boundary fault nwsb fault and b fault during stage ila is indicated by a southwestward outbuilding fandelta during this stage there was only one depocentre during stage ilb the depocentre of the subsiding zone split up this shifting of depocentres is explained according to the releasing overstep model by an increase of the overlap between the nwsb fault and the b fault during stage iii the cbb subbasin became continental and was inverted as demonstrated by its present day relief the area was severely faulted by n040e trending r and y shears on a metre scale which led to an estimated cumulative sinistral displacement of 2 km since fandelta deposition the present day activity of the nwsb fault is shown by sinistrally deflected stream courses and pressure ridges

the fate of foramol temperate type carbonate platforms abstract on rimmed shelves of bahamian type characterized by chlorozoan associations and typical of tropical seas carbonate production keeps pace with normal sea level rise except when rapid rise or drastic environmental changes occurs on the other hand open temperate carbonate shelves are characterized by low carbonate production of the foramol association molluscs benthic foraminifera bryozoans coralline algae etc and generally show seaward relict sediments because carbonate production cannot keep pace with normal rate of sea level change several examples of recent drowning foramol carbonate platforms e g large areas of the mediterranean sea eastern northeastern yucatan shelf as well as analogous ancient drowned foramol type carbonate platforms e g early to middle miocene of the southern apennines miami terrace may support the idea that the drowning of many ancient carbonate platforms has been favoured by their biogenic foramol sensu lato constitution because of their typically low rate of growth foramol carbonate platforms are fated to be drowned even if the sea level rise is one with which the normal growth of chlorozoan platforms can keep pace similar conditions may also occur in tropical areas where variations in environmental conditions such as the presence of cold waters changes in salinity and increased nutrients preclude the development of chlorozoan associations

lateral interaction between metamorphic core complexes and less extended tilt block domains the alpujarras strike slip transfer fault zone betics se spain abstract the alpujarras area in southeastern spain exhibits one of the scant documented examples of extension related strike slip faults bordering core complexes in the world faults of the alpujarras fault zone define a regional scale complex ene striking transfer zone that marks the boundary among the sierra nevada elongated dome a highly extended constricted core complex and a less extended domain formed by large scale tilt blocks detailed mapping and structural analysis show that the alpujarras fault zone is an integral part of the wsw directed normal fault systems that thinned the betic hinterland during the middle miocene to recent time fault patterns and palaeostress analysis both indicate that dextral movement along the strike slip faults was induced by a local stress field with a sub horizontal e w to ese wnw trending maximum principal stress axis which is synchronous with the regional stress field driving the normal fault systems palaeostress analysis also indicates subsequent variations in the stress field with a sub horizontal nw se to n s trending maximum principal stress axis thus producing both the tectonic inversion of the northern fault of the alpujarras system and shortening of the unloaded extensional detachment footwall a simplified kinematic model for the tectonic evolution of the alpujarras area from the middle miocene to recent emphasizes the kinematic coupling of normal faults and strike slip transfer zones in the extensional process

fold and fault interactions during the development of an elongated narrow basin the almanzora neogene quaternary corridor se betic cordillera spain 1 elongated corridors grow in different tectonic settings mainly in areas deformed by fold and fault sets parallel to the borders the almanzora corridor however is a good example of an e w elongated asymmetrical narrow basin developed in a changing stress scenario generated by the interaction of fold and fault sets oriented parallel and oblique to the corridor borders the initial crustal thickening process was mainly related to the development of the e w oriented sierra de los filabres large antiform which constitutes a major heterogeneity during the tortonian a nw se convergent tectonic setting oblique to this already emerged antiform gives rise to a large dextral simple shear band that determines the development of a major fold las estancias antiform the asymmetrical location of minor tectonic structures faults and minor folds and the distribution of sedimentation denudation areas that finally configure the almanzora corridor synform furthermore development of nw se oriented normal faults points to ne sw orthogonal extension in a new stress field oblique to the corridor borders this region illustrates that the elongated character of the corridors may persist inherited from the orientation of previous crustal rheological heterogeneities in addition marine transgression may be produced in compressional settings favored by the synform development during initial stages of crustal thickening finally led to the relief uplift

carbonate lithofacies as paleolatitude indicators problems and limitations abstract detailed study of miocene carbonates in the mediterranean region and their analogues on modern carbonate shelves in the mediterranean sea brazil and other areas reveals at least three major types of carbonate platform lithofacies in addition to the classic tropical coral reef chlorozoan lithofacies a chloralgal lithofacies similar to the chlorozoan but without hermatypic corals b rhodalgal lithofacies characterized by abundant encrusting coralline algae and c molechfor lithofacies consisting of benthic foraminifers molluscs echinoids bryozoans and barnacles these carbonate lithofacies present complex distribution patterns seemingly related primarily to latitude and depth that control water temperature although other factors e g water circulation river discharge suspended sediment controlling water salinity and temperature nutrient content light penetration etc also play important roles chloralgal and rhodalgal lithofacies can be considered two transitional terms between the two end members the chlorozoan lithofacies which characterizes shallow tropical shelves and the molechfor lithofacies which characterizes colder and or deeper areas detailed textural and sequential analysis are required for satisfactory interpretation of these lithofacies in ancient rocks

upper ordovician facies in the lac saint jean outlier quebec eastern canada palaeoenvironmental significance for late ordovician oceanography upper ordovician caradocian carbonates of eastern north america were deposited along the iapetus continental margin and record a transition from warm to cool water settings despite this margin having been within the southern hemisphere tropical belt this event has been documented from virginia usa to southern quebec canada although not previously from areas close to the palaeoequator field petrographic and major element geochemistry data have been gathered from the poorly known upper ordovician carbonate succession outcropping in the lac saint jean outlier in central quebec the succession consists of a lower siliciclastic formation tremblay overlain by three limestone formations simard shipshaw and galets and capped by shales pointe bleue shale from macro and microfaunal evidence carbonate sedimentation occurred during the late caradoc and is younger than the early to mid caradoc carbonate succession present farther south relative sea level fluctuations recorded in the sediments suggest an overall sea level rise briefly halted by a minor end caradocian sea level fall the lower limestone formation simard consists of muddy sediments with algal coral stromatoporoid boundstones green algae are abundant this unit reflects low energy sedimentation on a shallow warm water carbonate ramp colonized by a diverse chlorozoan fauna the upper limestone formation galets is typified by coarse grained bioclastic sediments punctuated by numerous phosphate rich hardgrounds with evidence for high energy shallow marine conditions faunas were dominated by crinoids and bryozoans this unit represents high energy sedimentation on a cool shallow water carbonate ramp colonized by a brynoderm faunal association between both units a deeper marine outer shelf limestone formation shipshaw was developed in the lac saint jean area a transition from warm to cool water carbonate ramps occurred in latest caradoc times and is litho and biofacies wise similar to what is documented for lower caradocian limestones present farther south upwelling of nutrient rich cool bottom oceanic waters was a probable cause for this transition

active tectonics in the sierra nevada betic cordillera se spain insights from geomorphic indexes and drainage pattern analysis article i nfo the sierra nevada of the central betic cordillera is a 3000 m high mountain range surrounded by neogene quaternary sedimentary basins having been uplifted since late miocene times the southern and western mountain fronts of the sierra nevada are fault bounded while the northern one is an unconformity between the neogene quaternary sediments of the guadix baza basin and the metamorphic rocks of the nevado filabride complex we have carried out a geomorphic study by examining drainage patterns and characteristics of mountain fronts in order to reveal areal variations and styles of rock uplift mountain front sinuosity smf area altitude relations hypsometric curves and valley floor entrenchment differ significantly between the northern western and southern mountain fronts the lack of important faults along the northern sierra nevada mountain front together with the elevated topographic position of the guadix baza basin average altitude is around 1100 m points to similar uplift of both geomorphic units sierra and basin in a single large scale crustal block the asymmetry factors show systematic asymmetries at both sides of the lanjaron river probably due to the presence of an active nne ssw oriented antiform in the western sierra nevada finally river profiles indicate maximal river entrenchment in the western part of the sierra nevada probably related to the uplift of the footwall of the padul niguelas fault system therefore our geomorphic analysis suggests that the western part of the sierra nevada is tectonically active by means of a combination of normal faults along the mountain front and nne ssw oriented active folds which in turn likely have a gravitational origin related to the exhumation of the footwall of the normal fault system

geodetic evidence for continuing tectonic activity of the carboneras fault se spain abstract the carboneras fault zone cfz is a prominent onshore offshore strike slip fault that forms part of the eastern betic shear zone ebsz located in se spain in this work we show for the first time the continuing tectonic activity of the cfz and quantify its geodetic slip rates using continuous and campaign gps observations conducted during the last decade we find that the left lateral motion dominates the kinematics of the cfz with a strike slip rate of 1 3 0 2 mm yr along the n48 direction the shortening component is significantly lower and poorly constrained recent onshore and offshore paleoseismic and geomorphic results across the cfz suggest a minimum late pleistocene to present day strike slip rate of 1 1 mm yr considering the similarity of the geologic and geodetic slip rates measured at different points along the fault the northern segment of the cfz must have been slipping approximately at a constant rate during the quaternary regarding the eastern alpujarras fault zone corridor afz located to the north of the cfz our gps measurements corroborate that this zone is active and exhibits a right lateral motion these opposite type strike slip motion across the afz and cfz is a result of a push type force due to nubia and eurasia plate convergence which in turn causes the westward escape of the block bounded by these two fault zones

structure of alluvial valleys from 3 d gravity inversion the low andarax valley almeria spain test case this paper presents a gravimetric study based on 382 gravimetric stations in an area about 32 km2 of a nearly flat basin the low andarax valley this alluvial basin close to its river mouth is located in the extreme south of the province of almeria and coincides with one of the existing depressions in the betic cordillera the paper presents new methodological work to adapt a published inversion approach growth method to the case of an alluvial valley sedimentary stratification with density increase downward the adjusted 3d density model reveals several features in the topography of the discontinuity layers between the calcareous basement 2 700 kg m3 and two sedimentary layers 2 400 and 2 250 kg m3 we interpret several low density alignments as corresponding to se faults striking about n140 145 e some detected basement elevations such as the one previously known by boreholes in viator village are apparently connected with the fault pattern the outcomes of this work are 1 new gravimetric data 2 new methodological options and 3 the resulting structural conclusions

an introductory perspective on non tropical shelf carbonates abstract this brief account introduces the topic of non tropical shelf carbonate deposits both modern and ancient specific aspects of which are described and discussed in the 22 accompanying papers in this special issue of sedimentary geology non tropical shelves are loosely defined as lying poleward of the present limit of development of hermatypic coral reefs or beyond the mean annual surface water isotherm of about 20 c typically near 30 latitude most geoscientists have traditionally regarded shallow water carbonate formation as a low latitude phenomenon however wherever the rate and extent of terrigenous sediment dilution is small the potential exists for extensive deposits of skeletal carbonate to accumulate on shelves beyond the sub tropics the facies attributes of the modern non tropical carbonates are distinctive and contrast significantly with the structural lithological faunal floral mineralogical and diagenetic character of their tropical counterparts in the rock record non tropical limestones probably occur throughout the phanerozoic but generally remain to be identified and or interpreted as such they are presently described mainly from the ordovician permian and tertiary quaternary periods of major continental glaciations and accentuated latitudinal thermal gradients a uniformitarian approach to the recognition and interpretation of ancient shallow marine limestones requires acceptance of both tropical and non tropical carbonate facies models

orthogonal folding of extensional detachments structure and origin of the sierra nevada elongated dome betics se spain 1 a close relationship of the kinematics and timing between low angle extensional faulting and upright folding is established for the miocene detachment systems in the hinterland of the betics in southeastern spain folding accompanied tectonic denudation developing elongated domes with fold axes both parallel and perpendicular to the direction of extension the geometry kinematics and tectonic evolution of two major sequentially developed extensional fault systems have been characterized in several e w elongated mountain ranges of the central betics on the basis of new cartographic and structural data and a comprehensive revision of other available geological and geophysical observations the extensional systems have an average wsw direction of extension and led to exhumation of the two lower metamorphic complexes of the betics the nevado filabride and the alpujarride during the middle and upper miocene serravallian to tortonian the extended domain contains a core complex with distal and proximal antiformal hinges separated by around 60 km and with a fold amplitude of 6 km measured parallel to the direction of extension the total amount of extension across the core complex is about 109 116 km corresponding to a stretching factor of 3 5 3 9 estimated using the distance between fold axial surfaces and a geometrical model accomplishing footwall deformation during tectonic denudation via subvertical simple shear the elongated domal and basinal geometry of the detachments and their respective footwalls is due to the interference between two sets of orthogonal large scale open folds trending n s and e w longitudinal n s trending folds are interpreted as isostatic folds i e folds that developed in response to differential unloading of the extensional detachment footwalls inducing ductile flow in the middle crust these folds formed in a rolling hinge anticline in which rotation migrates westward through the footwall as it is progressively unroofed in contrast e w trending folds being subparallel to the direction of extension have a contractional origin and progressively affect to the west the isostatically readjusted segments of the detachments once they are inactive orthogonal folding occurred since the serravallian to lower pliocene extension is still active from the rolling hinge anticline in sierra nevada to the west the middle miocene to pliocene tectonic evolution of the sierra nevada elongated dome at the core of the betic hinterland is another example of the coexistence of extension and contraction during continued overall convergence and mountain building

neogene evolution of the sorbas basin se spain determined by paleostress analysis abstract the neogene subsidence history of the sorbas basin situated in the internal zone of the betic cordilleras of southeastern spain is strongly controlled by strike slip deformation the sedimentary sequence of the basin offers a good control on the timing of separate phases of fault activation the southern border of the sorbas basin is formed by a major east west trending fault zone the gafarillos fault zone which consists of intermixed slivers of pre neogene basement blocks and neogene basin sediments fault patterns and paleostress analysis both indicate that major displacement along this fault zone was dextral with a n310e oriented maximum principal stress axis strike slip movement along the east west oriented faults ended during the earliest messinian after a minimum of 6 ma of activation paleostress analysis indicates a subsequent phase of strike slip fault movement present in sites of up to early pliocene age the maximum principal stress axis orientation is n350e for this phase this deformation is synchronous with sinistral displacement along the palomares fault zone situated directly to the east of the study area subsequently our paleostress analysis indicates an extensional regime during the late pliocene to quaternary however extensional tensors were calculated at a number of sites possibly representing local stress regimes coexisting with the main strike slip deformation and sorbas basin subsidence folding of tortonian sediments points out that local compressional deformation took place as well during the neogene basin history observed wide ranges for the ellipsoid shapes of the calculated tensors support the existence of lateral stress variations

active transfer fault zone linking a segmented extensional system betics southern spain insight into heterogeneous extension driven by edge delamination pliocene and quaternary tectonic structures mainly consisting of segmented northwest southeast normal faults and associated seismicity in the central betics do not agree with the transpressive tectonic nature of the africa eurasia plate boundary in the ibero maghrebian region active extensional deformation here is heterogeneous individual segmented normal faults being linked by relay ramps and transfer faults including oblique slip and both dextral and sinistral strike slip faults normal faults extend the hanging wall of an extensional detachment that is the active segment of a complex system of successive wsw directed extensional detachments which have thinned the betic upper crust since middle miocene two areas which are connected by an active 40 km long dextral strike slip transfer fault zone concentrate present day extension both the seismicity distribution and focal mechanisms agree with the position and regime of the observed faults the activity of the transfer zone during middle miocene to present implies a mode of extension which must have remained substantially the same over the entire period thus the mechanisms driving extension should still be operating both the westward migration of the extensional loci and the high asymmetry of the extensional systems can be related to edge delamination below the south iberian margin coupled with roll back under the alboran sea involving the asymmetric westward inflow of asthenospheric material under the margins

relationships between tectonic and geomorphological linear features in the guadix baza basin southern spain linear elements of the landscape of the guadix baza basin southern spain were identified from a landsat tm image three important lineament trends have been identified in the guadix baza basin the first is ne sw which is the dominant trend in the basin the second is nw se and the third is ene wsw these three trends are correlated to the major faults of the guadix baza basin the study of linear features by the analysis of satellite data has revealed a strong link between the buried tectonic structures and the morphological features appearing at the surface the distribution and density of lineaments explains much of the morphology of the land surface it is possible to reconstruct elements of the tectonic and denudational history of the region and show that during quaternary times lineaments controlled the sedimentation of the basin and the drainage pattern copyright 1999 john wiley sons ltd

a step fault in central betics associated with lateral lithospheric tearing at the northern edge of the gibraltar arc subduction system abstract we study the crustal and lithospheric mantle structure under central betics in the westernmost mediterranean region by migrating p receiver functions along a dense seismic profile 2 km interstation distance the profile north south oriented probes the crustal structure of different geological units from the alboran domain in the south with metamorphic rocks through the external zones with sedimentary rocks to the variscan terrains of the iberian massif in the north from north to south the moho depth increases from 30 km to 46 km underneath the guadix basin due to the underthrusting of the iberian crust below the alboran crust and suddenly shallows to 30 km underneath the internal zones with a step of 17 km this sharp moho step correlates well with a lithospheric step of 40 km where the thickness of the lithosphere changes abruptly from 100 km in the north to 50 km in the south we interpret this sharp and prominent lithospheric step as the termination of the iberian lithosphere caused by a near vertical step subduction transform edge propagator fault that continues towards the surface as a positive flower tectonic structure of crustal scale this step fault is located at the northern edge of the narrow westernmost mediterranean subduction system facilitating the slab rollback motion towards the west the sharp termination of the iberian lithosphere occurs under the contact between the alpujarride and the nevado filabride complexes of the alboran domain in an ene wsw right lateral transpressive shear zone the thickest crust and lithosphere do not correlate with the highest topography along the profile suggesting that this high topography is a combined effect of the positive flower structure and the push up of the asthenosphere produced by the removal of the iberian lithosphere

foraminiferal zonation of late paleozoic depositional sequences from the later part of the devonian through the permian calcareous foraminifers became abundant and evolved rapidly this rapid evolution of taxa forms the basis of a detailed zonation through the carboniferous and permian comparison of this evolutionary history of foraminifers their biostratigraphic zonation and the depositional sequences in which they occur suggests that sea level events in late paleozoic depositional history contributed significantly in subdividing a fairly continuous evolutionary record into a succession of about 75 identifiable foraminiferal zones during a 100 125 myr time span although variable in terms of duration and vertical occurrences the more completely recorded high stand intervals give brief histories of the foraminiferal evolutionary record and are sandwiched between the poorly recorded or unrecorded low stand intervals many of the individual foraminiferal zones are confined to a single depositional sequence the late paleozoic carbonate foraminiferal fossil record as with the rest of the fossil record is strongly affected by sediment deposition nondeposition as a result of major changes in sea level this incomplete fossil record is the result of repeated depositional breaks because of the way that depositional sequences form it is not possible to ascribe macromutations punctuated evolution or punctuated gradualism as the cause of this evolutionary pattern of the shelf carbonate fossil record this pattern is distinctive and we refer to it as sequence evolution and sequence extinction in the later part of the middle permian and in the late permian the fossil record clearly illustrates that a series of faunal losses through sequence extinctions progressively exceeded faunal replacements and new species through sequence evolution but not a mass extinction as is commonly ascribed to the end of the permian period most permian faunas became extinct in the interval of 8 to 4 million years before the end of the late permian

early middle miocene stratigraphic turning points in the alicante region se spain reflections of western mediterranean plate tectonic reorganizations abstract the paper concerns the miocene deposits of the alicante region se spain which forms part of the prebetic and intermediate units representing the former southern passive margin of the iberian continent from the late jurassic up to the miocene the alicante region was the scene of a facies distribution with more continental lagoonal or shallow marine conditions in the north and northwest and more open or deeper marine in the south and southeast the early middle miocene deposits can be divided in three sedimentary cycles each one controlled by a different tectonic regime cycle i aquitanian is deposits after a block faulting phase at about 25 ma related to the formation of the ligurian and balearic troughs cycle ii burdigalian early langhian is separated from first cycle sediments by a complete reorientation of palaeogeography at 19 5 ma due to the collision of iberia with africa the southern part of the region is folded and uplifted and separated from a northern emerged area by a trough cycle iii late langhian serravallian is controlled by strike slip movements caused by the continuing convergence between africa and europe and resulting in the development of a new set of basins at 15 5 ma at the middle late miocene boundary the alicante region emerges thus younger important tectonics could not be dated our results are in conflict with several recent plate tectonic models for the miocene history of the western mediterranean where the internal betic zone is placed juxtaposed to the alicante region prior to the burdigalian

chemical evolution of groundwater in triassic gypsum bearing carbonate aquifers las alpujarras southern spain a hydrochemical study employing modelling techniques was carried out using samples taken at 65 points springs and wells in triassic carbonate aquifers lujar gador unit alpujarride complex betic cordillera these aquifers are made up of limestones and dolomites with some gypsum scattered or interbedded though the area is semi arid recharge is relatively high because of their mountainous nature the carbonate rocks contain dense microfissuration the groundwater flow regime is predominantly diffuse the karstic forms are in general poorly developed two main hydrochemical processes have been identified in these aquifers one is incongruent dissolution of dolomite that determines the chemical composition of the less mineralised water the other is dedolomitisation dolomite dissolution together with calcite precipitation caused by dissolution of gypsum which becomes predominant when the flow encounters interbedded gypsum this reaction is also frequently associated with low temperature thermalism and can play a part in more intense local karstification cavities sinkholes high transmisivity in wells observed in the sectors of these aquifers where gypsum is more abundant a reaction path model has been used to simulate the geochemical processes through a hypothetical aquifer with similar lithology to the alpujarride carbonate aquifers successive stages of evolution through the carbonate sequence represented by different saturation states with respect to calcite dolomite gypsum and co2 have been modelled and then compared with the field data

cool water carbonates in a paleoequatorial shallow water environment the paradox of the auernig cyclic sediments upper pennsylvanian carnic alps austria italy and its implications distinct parts of limestones within the upper paleozoic auernig group of the carnic alps austria and italy are characteristic of cool water carbonates the carnic alps were between 5 n and 10 s paleolatitude during the late carboniferous a position confirmed by dasyclad algae and fossil plants the floral association occurrence of coal seams and absence of evaporites indicate a humid tropical environment the entire section lacks abiotic components of typical warm water limestones no ooids and no aggregates occur within the auernig group parts of the limestones show surprisingly a cool water association of high diversity bryozoans brachiopods crinoids red algae sponge spicules and entomozoan ostracodes the genesis of these limestones atypical for a paleoequatorial setting cannot be explained by changes in salinity bathymetry or terrigenous input the water temperature possibly linked with upwelling nutrient supply and paleoceanographic currents is the most convincing cause of this unusual association paleoceanographic changes are interpreted as linked to contemporaneous glaciation deglaciation cycles in gondwana this paper shows that cool water carbonates in shallow water environments are not necessarily nontropical as generally interpreted future studies should consider water temperature oceanic circulation and availability of nutrients supplementary to bathymetry salinity and latitude related climate in interpretation of carbonate components

alpine tectonics and rotation pole evolution of iberia abstract the geological evolution of the betic cordilleras and pyrenees reflects the cretaceous and tertiary rotation pole and kinematic evolution of the iberian and african plates new constraints on the alpine tectonic evolution of the iberian plate are provided by p t t data and regionally consistent stretching lineations from the metamorphic parts of the betic cordilleras high pressure low temperature metamorphism in the betic cordilleras resulted from continent continent collision which caused subduction to a maximum depth of 37 km a preliminary 116 10 ma radiometric age for this event corresponds to the initiation of seafloor spreading to the west of iberia which lasted until about 80 ma intracontinental thrusting in the betics between 99 ma and 83 ma took place after subduction ended e w to ese wnw trending stretching lineations indicate the direction of thrusting which resulted in extensional strains of 200 600 the timing of thrusting in the betics coincides with a 95 80 ma tectonic phase in northern africa during which e w stretching lineations were formed the stretching lineations are coincident with the 110 80 ma motion vector of africa iberia with respect to eurasia thrusting in the betics and deformation in northern africa was driven by convergence of africa iberia and eurasia cretaceous deformation is further recorded by terrigeneous sedimentation in the mauritanian flysch and by the tectosedimentary evolution of the malaguide complex crustal thinning magmatism and metamorphism in the pyrenees during the 110 85 ma period is governed by a left lateral strike slip of africa iberia with respect to eurasia around the same rotation pole as thrusting in the betics during the 80 54 ma period the rotation pole was situated west of gibraltar near the previous active collision zone this inhibited large scale overthrusting and related penetrative deformation in northern africa and the betic cordilleras deformation was instead transferred to the northern boundary of iberia now acting as an african promontory from the campanian on wards oblique convergence took place around the combined gibraltar rotation pole deformation culminated in the late eocene corresponding to spreading in the norwegian greenland sea at 55 ma which induced an additional compression in western eurasia during the pyrenean collision high pressure metamorphic rocks in the betic cordilleras were exhumed and they cooled substantially the cooling trend was disturbed by oligocene extensional deformation and introduction of a transient heat source which correlates with the mantle being uplifted during extension heating culminated at the oligocene miocene boundary in the betic cordilleras and in northern africa this evolution agrees with the development of a plate boundary between iberia and africa at 30 ma after completion of the pyrenean collision the new plate boundary was connected to the western european rift system renewal of compression and overthrusting in the betic zone took place after 20 ma overthrusting is succeeded by two phases of wrenching juxtaposing crustal segments with different moho depths inherited from the late oligocene to early miocene extension