the deglaciation of the sierra nevada southern spain abstract cosmogenic 36 cl surface exposure dating was carried out on 19 samples from glacially polished bedrock rock glaciers and moraines of four glaciated valleys with different orientations in the sierra nevada spain around pico del veleta 37 3 n 3 21 w 3398 m asl remains of moraines older than the global last glacial maximum exist but their poor preservation makes them an unreliable subject for surface exposure dating results show that the last local glacial maximum advance took place earlier than the global last glacial maximum but within the mis 2 although additional dating is needed to confirm this exposure ages from bedrock steps show a general glacier retreat in progress by 15 14 ka shortly afterwards an extensive system of rock glaciers formed at the base of the valley headwalls with the most recent rock glacier lasting until 7 ka ago from their location morphology and analysis of other proxies we interpret their origin as related to the deglaciation process and marked instability of cirque headwalls rather than to extreme periglacial conditions a recent similar occurrence was the transformation of the little ice age glacier on the north face of the pico del veleta into a rock glacier under temperate high mountain climatic conditions

radiocarbon chronology of the early human occupation of argentina this paper reports the compilation and initial analysis of a database of 14c dates from archaeological sites in argentina for the period 13 000 and 7000 14c bp the spatial and temporal distribution of human occupation evidence during this period is surveyed with discussion of potential sampling biases affecting the recognition of such sites in each region of argentina the archaeological signal of human occupation at the beginning of this period 13 000 11 000 14c bp is suggestive but sparse and weak however from about 11 000 14c bp there is a consistent archaeological signal most of the earliest occupation evidence comes from the eastern pampas and from southern patagonia in the chaco and northeast regions similarly early archaeological sites have not yet been detected this contrast may reflect the actual distribution of early human occupation but it may also reflect biased research effort and or systemic factors affecting the visibility and level of preservation of the early archaeological record in other regions such as the eastern slope of the andes in patagonia the peri andean central west and the northwest where there has been intensive archaeological research for an extended period and there are fewer systematic factors which are likely to bias archaeological visibility the absence of archaeological evidence of early occupation may indicate delayed colonization of these more marginal environments the conclusion discusses the implications of 14c dates associated with fishtail projectile points for the western hemisphere pre clovis debate and the implications of terminal pleistocene early holocene dated remains of extinct mammals for the megafaunal overkill hypothesis

the summit erosion surfaces of the inner betic cordillera their value as tools for reconstructing the chronology of topographic growth in southern spain erosion surfaces at the top of mountain ranges have suggested to geomorphologists that the earth s crust can undergo rapid pulses of uplift during which rates of denudation fail to balance with rates of crustal uplift thereby preserving much of the initial plateau topography as it rises to greater elevations here we analyze a regionally extensive population of mappable planar surfaces which crown several major tectonically active sierras of the inner south eastern betic cordillera se spain based on a synthesis of long term landscape evolution involving landform reconnaissance dem based morphometric analysis structural geology sediment provenance analysis and field stratigraphy we conclude that the summit surfaces are a mosaic of discrete post orogenic erosion surfaces that each developed in relation to mediterranean marine base levels at a time when the sierras formed a series of low elevation islands they are not therefore fragments of a once regionally continuous paleoplain the summit surfaces were partly the result of shallow angle detachment faulting during the middle miocene in response to lithospheric slab detachment where evidence exists that the resulting low relief topography was reworked by marine abrasion during the tortonian sea level rise the terminal age of the surfaces is latest miocene age bracketing based on stratigraphic correlations among the many depocentres of the region and on published thermochronological data indicates that some erosion surfaces locally formed in less than 3 million years 8 ma 5 7 ma they were subsequently uplifted to their current elevations 1 7 to 2 km by pliocene to quaternary neotectonics in at least two major pulses

radiocarbon dates as data quantitative strategies for estimating colonization front speeds and event densities abstract archaeological analysis of large scale prehistoric population history requires us to estimate rates of spatial spread during dispersals and rates and magnitudes of temporal contraction during crashes using oxcal s mcmc sampling routine i introduce and demonstrate a simple and easily implemented method of estimating front speeds that takes due account of the uncertainty in the archaeological data in both dates and distances and argue that this method is more appropriate than those most often used in front speed estimation at present i also propose a simple and easily implemented method of estimating event densities as a demographic proxy as an alternative to summed calibrated probability distributions i argue that this alternative is a significantly better technique and show that its use also enables us to identify individual archaeological dates that are exerting particularly strong influence on the results so that we can efficiently allocate our attention when assessing the possible effects of exogenous sampling uncertainty to illustrate these methods i re analyse two published datasets relating to the early paleoindian colonization of north america my results with the new technique indicate that even with a very noisy dataset there was clear evidence in the framework of the intcal04 calibration curve for a drastic reduction in archaeological event densities following the younger dryas onset followed by a prolonged period of reduced human activity and a possible renewed phase of rapid growth after the younger dryas termination and onset of the holocene however the revised estimate of the younger dryas marine reservoir offset in the intcal09 calibration curve for 12 550 12 900 cal bp changes the picture significantly by flattening the peak in clovis age events and pushing it forward in time into the early younger dryas itself

early human occupation of uruguay radiocarbon database and archaeological implications abstract the early human occupation of the territory between the uruguay river and the atlantic coast occurred from ca 11 ka to 7 ka bp in four millennia environmental and cultural changes occurred with better conditions for human life and the end of the megamammal extinction process the climate became warmer and more humid the lowlands covered very extensive areas and the sea level and coastlines changed producing ecotonal zones with high productivity this process originated the la plata river of today environmental conditions and social processes are well combined in this successful human colonization corporate groups of dynamic hunter gatherers built an extended social interaction sphere and produced new tool kits for human work the emergence of variability in lithic projectile points is the material correlation of the technological adaptation to a new environmental condition the radiocarbon database for uruguay is adequate although a little limited for the atlantic coast there are several independent lines of evidence toward discussion of hunter gatherer modes of production and a dispersal model for the atlantic side of south america this paper explores information about covariant transformations in landscape occupation and in way of life as well as analyzing the role played by the atlantic coast in human expansion

controls on fan development evidence from fan morphometry and sedimentology sierra nevada se spain abstract we have studied the morphology and the morphometric relations between alluvial fans and drainage basins in a bajada system including more than 20 coalescent fans developed since the late pleistocene as a result of the recent uplift of the sierra nevada betic cordillera spain three allocycles of tectonic origin were recognised across which there is a clear evolution from debris flow to sheet flow dominated fans in connection with a decrease in the volume of fines available in the source areas the larger volume of accommodation space created by higher tectonic subsidence in the northern sector favoured vertical accumulation of sediment with the appearance of less elongated fans in the rest of the system where subsidence is less more elongated fans appear with the development of incised channels and irregular distribution of sediment in depositional lobes this involves the appearance of markedly asymmetric transverse profiles as well as lengthy recurrence between the sedimentation events on particular sectors of the fans where headward eroding gullies develop the lithology of the source area where intensely fractured rocks are found is responsible for an important sediment supply and a significant degree of clast sorting from the source area consequently a weak longitudinal trend in particle size can be recognised which influences the predominance of longitudinal constant slope profiles and anomalous relations between both fan area and fan slope and their drainage areas recent intense tectonic activity has caused the appearance of abnormally low slopes in upper sectors of some catchments where mass flows are trapped and the fans present a subsequently higher proportion of sheet flows recent piracy phenomena can be recognised in some of the drainage basins which indicate rejuvenation of the source area in which case the fan presents a rapid increase in the proportion of mass flows with the development of a segmented longitudinal profile due to the recent nature of the processes the morphometric relations in the fan fed by the basin affected by capture do not coincide with the other fans in the area

palaeoenvironmental reconstruction of la olla a holocene archaeological site in the pampean coast argentina the evolution of littoral palaeoenvironments in the southern pampas region of argentina towards the end of the early holocene and the beginning of the mid holocene is discussed and the formation processes of the archaeological site of la olla are analysed this site is located in the intertidal zone of the present beach and is remarkably well preserved the human occupation at the site has been dated at between 7400 and 6480 yrs bp and is interpreted as a place for the processing and consumption of the southern fur seal arctocephalus australis and southern sea lion otaria flavescens it is concluded that biostabilization by microbial mats of the sedimentary structures and archaeological remains that developed and are present on the tidal flat prevented their erosion by wind turbulence currents and waves this is what has permitted the exceptional preservation of the site on the basis of the analyses of one of the sectors of the site it can be concluded that the sedimentary succession of the la olla site is the result of the coastal environmental changes during the early mid holocene in the pre maximum transgressive episode during this interval a tidal flat developed on the pleistocene abrasion platform human occupation occurred during the formation of mixohaline marsh an upper intertidal lower supratidal zone ecosystem

emplacement of a fold nappe betic orogen southern spain the aguilon nappe sierra alhamilla southeast spain is a north closing recumbent isoclinal fold with a greatly thinned lower limb this large scale geometry can be demonstrated using small scale structures the fold nappe is detached along the lower limb and lies on a carpet of mylonitic schist mylonite and cataclasite formation of the nappe must have involved northward relative transport a point of current controversy in the betic zone during emplacement the nappe underwent extensive ductile deformation accomplished partly by pressure solution of silica in the highly deformed footwall rocks however quartz was deformed by crystal plastic processes the change in deformational mechanism suggests a downward increase in deviatoric stress which is compatible with a gravitational mechanism of nappe emplacement the core of the low grade nappe is occupied by medium grade schist the abrupt change in grade suggests that the schist contact is an extensional fault that excised part of the original metamorphic zonation and was subsequently refolded in the nappe such relations are common in the betic zone and suggest extension by listric normal faulting a characteristic feature of nappes emplaced by gravity spreading

deciphering tectonic and erosion driven exhumation of the nevado filabride complex betic cordillera southern spain by low temperature thermochronology introductionthe betic cordillera in south eastspain forms the westernmost end ofthe alpine mountain belt it is formedby a stack of metamorphic complexes the so called internal zones oralbora n domain which were thrustonto unmetamorphosed ysch units the latter are superimposed onunmetamorphosed sediments of thesouth iberian palaeomargin balanya and garci a duen as 1987 the pile ofmetamorphic complexes in the inter nal zones is formed from bottom totop by the nevado fila bride thealpuja rride and the mala guide com plexes the sierra nevada and sierra de losfilabres mountains in the centralbetic cordillera are antiformal ridgesresulting from large scale uprightfolding with e w to nne ssw foldaxes fig 1a in both the ranges thenevado fila bride rocks crop out inthe footwall of the mecina fault abrittle detachment fault which de nesa core complex like structure roofedby the alpuja rride complex galindo zaldi var et al 1989 jabaloy et al 1993 marti nez marti nez et al 1997 the mecina fault shows a top to the wsw sense of movement garci a duen as and marti nez marti nez 1988 galindo zaldi var et al 1989 the nevado fila bride rocks aregrouped into an upper unit with highpressure hp metamorphism and alower unit with lower pressure condi tions separated by the filabres fault a brittle detachment with top to the west sense of movement marti nez marti nez et al 2002 2004 fig 1a how and when the sierra nevadaand sierra de filabres were exhumedis still a matter of debate zirconu pb shrimp and garnet lu hfdating suggest that exhumation andcooling of the nevado fila bride com plex started immediately after the hpmetamorphic peak in the upper unitat 18 15 ma lo pez sa nchez viz cai no et al 2001 go mez pugnaireet al 2004 platt et al 2006 apatiteand zircon ssion track aft andzft ages in most of the nevado fila bride rocks support rapid coolingfrom 300 to 100 c at 12 8 ma johnson et al 1997 while aftdata in the western sierra nevadainclude ages that are younger than5 ma figure 1 b shows an isoagecontour map of available aft cool ing ages johnson 1997 johnsonet al 1997 reinhardt et al 2007 clark and dempster 2009 thiswork johnson et al 1997 proposedthat cooling was linked to the top to the wsw movement of the mecinafault starting at c 12 ma in the eastand ending at 9 8 ma in the west fig 1b to explain young c 4 ma aft ages and a negative age eleva tion correlation in the western sierranevada fig 2a johnson 1997 proposed the exhumation of a palaeo apatite partial annealing zone paz that was folded and eroded in thepliocene reinhardt et al 2007 obtained a similar age elevationpattern fig 2a and in contrast explained it by fault controlled exhu mation that involved unroo ng viaextensional detachments above thenevado fila bride core and localisedrapid denudation of the upland clarkand dempster 2009 presented addi tional aft ages from the westernsierra nevada that failed to corrobo rate the age elevation correlation fig 2a these authors proposedthree denudation events at 9 7 and4 ma the 9 ma event was related tothe movement of the mecina fault the 7 ma event was related to theformation of a rolling hinge anticlinerecognised by marti nez marti nezet al 2002 2004 and the third eventwas linked to a rapid cooling event at4 ma generated by rotation of thebasement block around an east westaxis abstract

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

tectonic denudation and topographic development in the spanish sierra nevada 1 the denudation history of the rapidly uplifting western part of the spanish sierra nevada was assessed using apatite fission track aft ages and 10be analyses of bedrock and fluvial sediments major contrasts in the denudation history are recorded within the 27 km2 rio torrente catchment upland areas are characterized by low relief low slope angles and locally the preservation of shallow marine sediments which have experienced 2 km of denudation since circa 4 ma the minimum denudation rates of 0 4 mm yr 1 derived from aft also contrast with the slow medium term 104 years erosion rates 0 044 0 015 mm yr 1 estimated from 10be measurements at high elevations the local medium long term contrasts in denudation rates within the high sierra nevada indicate that much of the unroofing occurs by tectonic denudation on flat lying detachments in lower elevation parts of the catchment rapid river incision coupled to rock uplift has produced 1 6 km of relief implying that the rivers and adjacent hillslopes close to the edge of the orogen are sensitive to normal fault driven changes in base level however these changes are not transmitted into the low relief slowly eroding upland areas thus the core of the mountain range continues to increase in elevation until the limits of crustal strength are reached and denudation is initiated along planes of structural weakness we propose that this form of tectonic denudation provides an effective limit to relief in young orogens

continuity and discontinuity in the human use of the north coast of santa cruz patagonia argentina through its radiocarbon record in this paper the analysis of a radiocarbon database of the north coast of santa cruz central patagonia argentina is presented dated archaeological samples were obtained from 56 different types of archaeological sites open air residential sites and burials and also rock shelters the objective of this paper is assessing the continuities and discontinuities in the chronological signal of the area and identifying tendencies along the holocene the database currently contains 75 radiocarbon dates falling between ca 8000 and 300 bp the radiocarbon data base provides information on the chronological spatial and contextual variability of the archaeological record of north coast of santa cruz by means of different analysis of sum of probabilities we present three different chronological moments of human use of the coast and intermediate zone can be identified a first moment is represented by early evidence of settlement during middle holocene a second moment corresponds to a hiatus between ca 5800 and ca 3900 bp without archaeological evidence finally a third moment is where an increasing of chronological signal occurred related to greater artifactual variability and an increase in the intensity of human settlement in the patagonian region the causes that could have influenced in the discontinuity of the chronological signal of the study area and the characteristics of the different moments identified are discussed

radiocarbon chronology of early human settlement on the isthmus of panama 13 000 7000 bp with comments on cultural affinities environments subsistence and technological change abstract the first human migrants entering south america must have used the isthmian route convincing archaeological evidence for pre clovis groups is lacking paleoindian artifacts including clovis and fishtail fluted projectile points have been found at several localities but at only one site vampiros 1 in buried and radiocarbon dated deposits 11 500 9000 bp close similarities between clovis point reduction sequences at two panamanian quarry workshops to those of early us clovis sites vouch for temporal proximity and suggest rapid movement of clovis bands through central america 11 050 10 800 bp vampiros 1 and other rock shelters were occupied during the early holocene 10 000 7000 bp when climate became warmer and wetter un fluted bifacial projectile points were made until 7000 bp widespread grinding stones and carbonized tree fruits announce a mixed economy at the beginning of the holocene cultivated leren arrowroot squash and bottle gourd appeared by 8000 bp there are no indicators of human activities at lake la yeguada 650 m asl 14 000 11 150 bp nor at vampiros 1 16 000 11 500 bp pre clovis populations were probably bound to the now drowned pacific coast intense burning and deforestation commenced at la yeguada 11 050 bp coevally with clovis human impacts were thenceforth continuous swidden farming had largely removed forest cover by 7000 bp across seasonally arid central pacific panama lake sediment data from forested areas with less seasonal climates on the caribbean and pacific watersheds indicate moderate human interference before 7000 bp the mtdna history of modern panamanians confirms native american continuity from before 10 000 bp and provides support for the pacific route of initial dispersal into south america

the alpujarride nevado fibabride extensional shear zone betic cordillera se spain in the betic cordillera the initial thickening of the alboran domain produced an alpine high pressure low temperature hp lt metamorphism in the alpujarride and nevado filabride complexes after 19 ma this thickening process evolved to an extensional stage with uplift rates of between 1 and 2 mm year 1 the extensional stage generated structures in a heterogeneous shear regime with a top to the west sense of movement the present day alpujarride nevado filabride contact is a detachment fault generated in this shearing regime in the footwall the first structure developed in this extensional stage is a planar linear fabric characterized by constrictive strain that is axial planar to kilometric recumbent tight to isoclinal folds the planar linear fabric is folded by inclined close to open folds with axes parallel to the stretching lineation the planar linear fabric and folds are deformed by a late extensional crenulation cleavage near the detachment surface finally brittle deformation was generated within the same kinematic framework as that of the ductile structures in the hanging wall meanwhile deformation had a brittle character producing faults and joints

the post last glacial maximum transgression in the de la plata river and adjacent inner continental shelf argentina abstract deposits resulting from the last glacial maximum transgression have been studied in the lowermost regions of the del plata fluvial basin in eastern argentina which include the de la plata river and adjacent inner shelf and coastal plains after applying the concepts of sequence stratigraphy those deposits were considered as a unit and defined as a depositional sequence composed of two systems tracts respectively representing the transgressive event and the highstand of sea level the sequence was deposited in different but genetically linked depositional environments such as high and low energy coasts with coastal barriers beach ridges coastal plains estuaries and deltas as well as inner shelf the boundary between the sequence and the underlying pre transgressive units is represented by the transgressive surface or unconformity modeled by the ravinement process which extends from the outer edge of the shelf to the coast this surface is time transgressive and can be recognized by distinct physical characteristics above and below it depending on the successive sedimentary environments developed in deep shallow or coastal waters as sea level fluctuated

granitic magma transport by fracture propagation granitic magmas commonly ascend tens of kilometres from their source terranes to upper crustal emplacement levels or to the earth s surface apart from its obvious bearing on the interpretation of the geology and geochemistry of felsic igneous rocks the magma ascent mechanism critically affects any modelling of the metamorphic evolution of the upper lithosphere as well as its rheology we propose that in general granitic magmas ascend via propagating fractures as dykes in extremely short time periods long distance diapiric transport of granitoid magmas through crustal sections is not viable on thermal or mechanical grounds and there is an apparent total absence of field evidence for diapiric rise of such magmas even in supposed type localities neither the shapes nor internal or external characteristics of granitic plutons necessarily reveal anything about the transport of their precursor magmas these are purely arrival phenomena dictated by local structure kinematics and stress states based on existing numerical treatments of the problem we show that granitic magmas are apparently sufficiently inviscid to travel through fractures to high crustal levels without suffering thermal death by freezing for example a 2000 km3 granitic batholith can be inflated by a 1 km 3m 20 km deep dyke system in less than 900 years the model proposed has numerous far reaching petrological and rheological consequences some of which are outlined

spacing and distribution of bed perpendicular joints throughout layered shallow marine carbonates granada basin southern spain abstract this contribution focuses on the controls exerted by sedimentological petrographic and mechanical rock properties on the distribution of bed perpendicular joints throughout layered carbonates the study was conducted on tortonian shallow marine skeletal grainstones and rudstones cropping out in the granada basin southern spain the results of combined field and laboratory analyses are consistent with the rock grain size of the studied carbonates exerting a key control on distribution of the bed perpendicular joints a positive correlation between joint spacing and mechanical unit thickness is computed for the grainstones whereas joints are almost absent in rudstones the rock grain size affected the diagenetic processes such as cementation and dissolution and therefore the resulting porosity and uniaxial compressive strength ucs values quantitative data show that higher ucs values are commonly associated with greater calcite amounts lower values of porosity and finer grain sizes and hence denser bed perpendicular joint sets in conclusion this study documents that it is possible to infer the density of bed perpendicular joints in layered carbonates based on the sedimentological petrographic and mechanical parameters considering the impact that this type of joints has on subsurface fluid flow the acquired knowledge can help the management of geofluids as well as the overall prediction of carbonate reservoir quality

small scale faulting topographic steps and seismic ruptures in the alhambra granada southeast spain 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

radiocarbon dates and anthropogenic signal in the south central andes 12 500 600 cal years bp this paper presents the analysis of the anthropogenic signal documented by four time series in the highlands of the south central andes puna of argentina and north chile spanning the period between 12 500 and 600 cal years bp our goal is to extract demographic and occupational histories from temporal data in this way based upon the full radiocarbon dataset and the sites of provenance of the dates we built the following time series the summed probability distribution of calibrated ages the relative frequency of calibrated ages the relative frequency of sites per unit of time and the frequency of new sites per unit of time for controlling the effects of site destruction on the anthropogenic signal we used the exponential model as well as the volcanic empirical model of taphonomic bias the four time series coincide in showing a regional pattern with a phase of low and fluctuating demography of relative long term duration followed by an growth phase well evident at 5000 cal bp in a context the economic intensification the long term demographic success of the hunter gatherers in the highlands many millennia before the consolidation of food production exemplifies the flexibility of this mode of subsistence for achieving human adaptation to extreme selective environments as the puna

a numerical model of dyke propagation in layered elastic media summary we develop a mathematical model describing dyke propagation in proximity of an elastic discontinuity of the embedding medium the dyke is modelled as a fluid filled crack in plane strain configuration employing the boundary element method the pressure gradient along the crack is assumed proportional to the difference between the densities of the host rock and the fluid mass conservation is imposed during propagation and fluid compressibility is taken into account the path followed by the crack is found by maximizing the total energy release given by the sum of the elastic and gravitational contributions the mathematical simulations provide a sort of refraction phenomenon that is a sudden change in the direction of propagation when the crack crosses the boundary separating different rigidities if the dyke enters a softer medium its path deviates towards the vertical if the dyke enters a harder medium its path deviates away from the vertical and may even become arrested as a horizontal sill along the interface if the rigidity contrast is large gravitational energy plays a major role during propagation in particular in proximity of layer boundaries this role is enhanced by the shift of the centre of mass due to changes of dyke shape mathematical results were validated by laboratory experiments performed injecting tilted air filled cracks through gelatin layers with different rigidities

analysis of a microcrack model and constitutive equations for time dependent dilatancy of rocks summary based on experimental observations and theoretical analyses the author introduces an ideal microcrack model in which an array of cracks with the same shape and initial size is distributed evenly in rocks the mechanism of creep dilatancy for rocks is analysed theoretically initiation propagation and linkage of pre existing microcracks during creep are well described also the relationship between the velocity of microcrack growth and the duration of the creep process is derived numerically the relationship agrees well with the character of typical experimental creep curves and includes three stages of creep then the damage constitutive equations and damage evolution equations which describe the dilatant behaviour of rocks are presented because the dilatant estimated value is taken as the damage variable the relationship between the microscopic model and the macroscopic constitutive equations is established in this way the mechanical behaviour of rocks can be predicted

quaternary slip history of the bare mountain fault nevada from the morphology and distribution of alluvial fan deposits analyses of alluvial fan sedimentation around bare mountain nevada indicate differential slip along the bare mountain fault during the pleistocene and holocene analyses show that the ratios of fan area to sediment source area and the degree of holocene sedimentation at the fan heads can be correlated with dip and displacement of the fault the well developed bajada and holocene deposits near the fan toes along the southwestern flank of bare mountain contrast with the location of holocene deposits near the fan heads and significantly smaller individual fan lobes on the eastern flank of the mountain adjacent to the bare mountain fault in addition ratios of fan area to source area along the eastern flank of the mountain decrease from north to south which we interpret to be caused by increased quaternary slip from north to south along the fault with relatively little holocene throw at tarantula canyon and maximum throw near wildcat peak the dip of the fault also changes from north to south with relatively shallow dip angles 45 to 50 at tarantula canyon and steeper 70 dips near wildcat peak geometric constraints dictate that for any given increment of horizontal extension vertical offsets will be smaller on those segments of the fault that have shallower dip angles on the basis of these observations we conclude that the recent slip rate of about 0 02 mm yr derived from trenching studies in the tarantula canyon fan should be considered a minimum value that may not represent the slip rate of the bare mountain fault as a whole

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

the use of summed radiocarbon probability distributions in archaeology a review of methods abstract using a database of australian archaeological radiocarbon dates n 2996 this paper explores three key methodological issues associated with the use of summed probability plots of radiocarbon data 1 the minimum sample size needed for a statistically reliable plot 2 the effect of radiocarbon calibration on the structure of these plots and 3 the application of a taphonomic correction to such time series data the results identify several protocols recommended as best practice when using summed probability plots 1 a minimum sample size of 500 radiocarbon dates should be used and the sample size and the mean of the standard deviations of the radiocarbon dates t in the sample should both be reported 2 a moving average trendline of 500 800 years should be used to offset the effects of the calibration process and 3 surovell et al correcting temporal frequency distributions for taphonomic bias journal of archaeological science 36 2009 1715 1724 is explored with modifications and temporal limits

late holocene environmental dynamics and climate variability in a mediterranean high mountain environment sierra nevada spain inferred from lake sediments and historical sources landscape dynamics in the periglacial belt of a high mountain mediterranean environment is a process of rapid evolution but complex reconstruction following this purpose in this paper we discuss data from two sources concerning the past evolution of the present day periglacial environment in the sierra nevada southern iberian peninsula mountain lake sediments and documentary sources la mosca lake sedimentary record provides information about the palaeocological evolution in the mulhacen cirque over the last three millennia while documentary sources enable us to reconstruct the landscape evolution in the high lands of this massif over the last eight centuries during the late holocene cold and wet phases have favoured the activity of geomorphic processes with ephemeral development of glaciers in the highest northern cirques abundance of late lying snow patches and a decrease of the vegetation cover in the highest catchments by contrast warm periods have been more conducive to geomorphic stabilit

morphotectonics of the iberian peninsula a morphotectonic interpretation of the relief of the iberian peninsula ip is presented based on an analysis of its gross forms several geological geophysical and geomorphological methods were used in order to build up a morphostructural sketch three main categories were established using the approach of rantsman 1979 territorial units 1 megablock 9 macroblocks 34 mesoblocks 1 374 blocks and 2 523 microblocks morphostructural alignments 2 first 8 second 20 third and 1 fourth rank and 43 knots between morphostructural alignments second fourth rank the main seismic activity is concentrated on the first and second rank lineaments and some important epicenters are located near the lineament intersections the origin of the earthquakes in the vicinity of such knots can be explained by the forcing pushing of macroblocks westwards the existence of earthquakes along the lineaments may be explained by tension from the present study it appears that earthquake occurrence in the ip is due principally to stress concentrations around morphotectonic zones a seismotectonic interpretation of the ip is also presented on this map three zones are distinguished a b c each of them with a different active level and dimensions

the role of extension in the miocene denudation of the nevado filabride complex betic cordillera se spain the internal zone of the betic cordillera se spain consists of a nappe stack of three complexes the deepest of which is the nevado filabride complex the zone is separated from the overlying alpujarride complex by a crustal scale shear zone that has variously been interpreted as a thrust or an extensional detachment a suite of 74 new apatite and zircon fission track results have been obtained from the nevado filabride complex and these have been used to define regional cooling patterns for the complex rapid cooling 105 c 200 c ma 1 is spatially related to the tectonic contact with the overlying alpujarride complex cooling to near surface temperatures occurred first in the east sierra de los filabres during the mid serravallian 12 1 ma and was completed by the early tortonian 9 8 ma in the west sierra nevada there is no correlation between fission track age and sample elevation these results are consistent with tectonic unroofing of this complex a finding that favors extension as the mechanism by which the two complexes were brought into contact extension spans the middle and earliest upper miocene 12 8 ma in the study area and therefore lasted much longer than previously documented a hypothesis is advanced which links oblique convergence between the iberian plate and the betic internal zones resulting in crustal contraction at depth with orogen parallel extension in the middle and upper crust

aggradation and dissection sequences on spanish alluvial fans influence on morphological development abstract similarities in quaternary alluvial fan development are identified throughout southeast spain pre wurm aggradation phases culminate in calcrete crusted upper fan surfaces which are followed by wurm dissection phases producing deep fanhead or through trenches deposits of the aggradation phases reflect source area size relief and geology and in addition to proximal distal facies variations show vertical decreases in debris flow and increases in gravel deposition the dissection phases were complicated by cut and fill sequences forming within trench terraces which show a southward decrease in complexity the sequences are expressed in progressive changes in fan terrace and channel slopes and intersection point location fan morphological development during the quaternary reflects long term progressive change complicated by short term responses to climatic fluctuations and further comolicated by the locally variable effectiveness of trenching thresholds

steady solutions for feeder dykes in a density stratified lithosphere abstract the propagation of dykes in the lithosphere is described physically as a fluid driven fracture process in a brittle elastic solid from this description mathematical solutions to the coupled equations of fluid mechanics fracture mechanics and elasticity are used to provide simple quantitative models for steady flow i e constant flow rate in a feeder dyke through a density stratified lithosphere conditions for fracture at the dyke margins and elastic deformation of the dyke walls to be significant are derived and evaluated the solutions demonstrate the importance of fracture elasticity and viscous pressure drop in determining the dyke s dimensions and of the role of the level of neutral buoyancy lnb in determining the height of ascent below the lnb vertical flow is driven by a dominant pressure balance between the local buoyancy and the local viscous pressure drop the width and lateral extent of a dyke increase towards the lnb and there is a transition from vertical flow to lateral flow directed along the lnb

tectonically driven landscape development within the eastern alpujarran corridor betic cordillera se spain almeria abstract the betic cordillera is a topographic manifestation of miocene to recent collision between the african and the european plates mountain ranges in the internal zone of the betic cordillera are exhumed massifs of metamorphic and sedimentary rocks and are surrounded by low lying sedimentary basins the neogene history of mountain range uplift and basin formation in the betics is well studied but quaternary topographic development and its relation to convergent plate boundary tectonics is less understood deformation rates of stream incision and factors controlling landscape evolution on the flanks of the highest mountains in the betic cordillera are studied to gain insight on the relationship of quaternary tectonics to topographic development specifically geomorphic processes that led to formation of topographic relief within the internal zone of the betic cordillera are assessed this paper is based on a field study conducted in the eastern alpujarran corridor eac which is the eastern half of a 4 6 km wide and 80 km long inverted sedimentary basin the mid to late quaternary history of basin denudation is deduced on the basis of morphostratigraphic geochronologic and structural geologic analyses of oxygen isotope stage 8 time fluvial deposits in the eac results of these analyses indicate that climate and faulting played only a minor role in landscape evolution in the eac instead the eac topographic trough was excavated by a drainage network whose axial stream rio andarax was incising at a rate between 0 3 and 0 7 m ka since oxygen isotope stage 8 this paper demonstrates that these incision rates are the same as regional rock uplift rates in the eac during the mid and late quaternary topographic relief between the eac and adjacent mountain ranges developed largely as a result of fluvial denudation driven by regional uplift the implications of the results of this investigation are used to propose a model of quaternary topographic relief development in the internal zone of betic cordillera topographic relief between internal zone bedrock massifs and adjacent basins formed largely as a result of fluvial denudation driven by regional uplift faulting also played a significant role in areas that are within a few kilometers of crustal scale fault zones

getting granite dikes out of the source region whether a dike can propagate far from a magma reservoir depends upon the competition between the rate at which propagation widens the dike and the rate at which freezing constricts the aperture available for magma flow various formulations are developed for a viscous fluid at temperature t sub m intruding a growing crack in an elastic solid the initial solid temperature equals t sub m at the source and decreases linearly with distance from the source if t sub m is the unique freezing temperature of the fluid dike growth is initially self similar and an essentially exact solution is obtained if t sub m is above the solidus temperature the solution is approximate but is designed to overestimate the distance the dike may propagate the ability of a dike to survive thermally depends primarily upon a single parameter that is a measure of the ratio of the dike frozen margin thickness to elastic thickness perhaps more intuitively one may define a minimum distance from the essentially solid reservoir wall to the point at which the host rock temperature drops below the solidus necessary for dikes to propagate far into subsolidus rock it is concluded that for reasonable material properties and source conditions most basalt dikes will have little difficulty leaving the source region but most rhyolite dikes will be halted by freezing soon after the magma encounters rock at temperatures below the magma solidus while these results can explain why granitic dikes are common near granitic plutons but rare elsewhere the potentially large variation in magmatic systems makes it premature to rule out the possibility that most granites are transported through the crust in dikes nonetheless these results highlight difficulties with such proposals and suggest that it may also be premature to rule out the possibility that most granite plutons ascend as more equidimensional bodies

atmospheric 14c variations derived from tree rings during the early younger dryas abstract atmospheric radiocarbon variations over the younger dryas interval from 13 000 to 11 600 cal yr bp are of immense scientific interest because they reveal crucial information about the linkages between climate ocean circulation and the carbon cycle however no direct and reliable atmospheric 14c records based on tree rings for the entire younger dryas have been available in this paper we present 1 high precision 14c measurements on the extension of absolute tree ring chronology from 12 400 to 12 560 cal yr bp and 2 high precision high resolution atmospheric 14c record derived from a 617 yr long tree ring chronology of huon pine from tasmania australia spanning the early younger dryas the new tree ring 14c records bridge the current gap in european tree ring radiocarbon chronologies during the early younger dryas linking the floating lateglacial pine record to the absolute tree ring timescale a continuous and reliable atmospheric 14c record for the past 14 000 cal yr bp including the younger dryas is now available the new records indicate that the abrupt rise in atmospheric 14c associated with the younger dryas onset occurs at 12 760 cal yr bp 240 yrs later than that recorded in cariaco varves with a smaller magnitude of 40 followed by several centennial 14c variations of 20 25 comparing the tree ring 14c to marine derived 14c and modelled 14c based on ice core 10be fluxes we conclude that changes in ocean circulation were mainly responsible for the younger dryas onset while a combination of changes in ocean circulation and 14c production rate were responsible for atmospheric 14c variations for the remainder of the younger dryas

fault creep growth model and its relationship with occurrence of earthquakes summary a fault model is used to analyse creep growth process of microcracks in damage zone near the tips of fault by means of the rheology fracture mechanics when microcracks in the zone link each other and their deformation quickly intensifies it means that an earthquake is taking place to a certain degree the relationships among some key parameters that are correlated to the growth of microcracks are analysed theoretically these parameters include failure time of fault number of microcracks in unit area stresses field yield strength and rheological properties of medium the results indicate that the model proposed here is reasonable to describe the pregnant process of an earthquake in the meantime this research shows that with the results of in situ surveys and lab experiments it is possible to estimate the time span for a fault expanding

magma driven subcritical crack growth and implications for dike initiation from a magma chamber 1 the purpose of this paper is to explore a viscoelastic energy dissipation theory for subcritical dike growth from a magma chamber the theoretical relationship between the dike growth velocity and dike length is established using the viscoelastic subcritical crack growth theory proposed by the first author and the solutions of stress intensity factor at the crack tip derived by a perturbation method effects of magma chamber over pressure buoyancy and viscoelastic properties of the host rock on the subcritical growth rate are included in the model the numerical results indicate that the viscous energy dissipation of the host rock could allow a short dike to slowly grow on the order of 10 7 10 5 m s under modest over pressure and to accelerate when the stress intensity factor increases close to the fracture toughness followed by the unstable dike propagation the proposed theory provides a reasonable understanding of dike initiation process from a magma chamber

buoyancy driven crack propagation from an over pressured source the propagation of a liquid filled crack from an over pressured source into a semi infinite uniform elastic solid is studied the fluid is lighter than the solid and propagates due to its buoyancy and to the source over pressure the role of this over pressure at early and late times is considered and it is found that the combination of buoyancy and over pressure leads to significantly different behaviour from buoyancy or over pressure alone lubrication theory is used to describe the flow where the pressure in the fluid is determined by the elastic deformation of the solid due to the presence of the crack numerical results for the evolution of the crack shape and speed are obtained the crack grows exponentially at early times but at later times when buoyancy becomes important the crack growth accelerates towards a finite time blow up these results are explained by asymptotic similarity solutions for early and late times the predictions of these solutions are in close agreement with the full numerical results a different case of crack geometry is also considered in order to highlight connections with previous work the geological application to magma filled cracks in the earth s crust or dykes is discussed

depositional and post depositional processes in human modified cave contexts of west central patagonia southernmost south america abstract this contribution aims to analyse depositional and post depositional processes from two volcanic caves bano nuevo 1 and cueva de la vieja from west central patagonia in order to evaluate if natural and anthropogenic processes recorded therein are representative of basin scale processes for this purpose geomorphological sedimentological micromorphological petrographic magnetic paleontological and archaeological data are integrated results allow correlating the bano nuevo 1 and cueva de la vieja sequences comprising a record of ca 19 000 years in the first place the distinction between endogenous and exogenous detritus input mainly recorded by the mineralogy and lithotypes provided environmental data related to landscape stability i e vegetation cover the latter in turn could be interpreted as part of a complex feedback associated with major climatic changes on the other hand cave weathering rates observed through vertical variations of the gravel fraction along with bioactivity recorded by percentages of total organic carbon and micromorphological analysis provided constraints on temperature and or humidity being in agreement with available regional information main regional palaeoenvironmental changes observed in the sequences were the deglaciation processes the pleistocene holocene transition the holocene amelioration and the anthropocene although no distinctive variations were observed within holocene deposits biological processes mainly resultant of the human occupations could have obliterated such finer scale distinctions

dike propagation through layered rocks 1 dike penetration through a succession of upper crustal layers with different densities is studied with a new numerical code for an individual layer to significantly affect dike ascent its thickness must be of order 1 when scaled to the characteristic length scale for the inflated nose region that develops below the dike tip this characteristic length is l q 1 6 g 1 1 2 g 2 3 where and are the viscosity and buoyancy of magma g and are elastic moduli for the encasing rocks q is the magma flow rate and g gravity for basaltic dikes l is 1 km which is of the same order of magnitude as the typical thickness of sedimentary strata and volcanic deposits in such conditions dike ascent proceeds irregularly with large changes of velocity and width at an interface scaling laws for the ascent rate and dike width are derived penetration through low density layers is determined by a local buoyancy balance in the inflated nose region of the dike independently of the total buoyancy of the magma column between source and tip in such conditions a dike develops an internal overpressure that may be large enough to generate a horizontally propagating sill for this to occur the thickness of the low density layers must exceed a threshold value which depends only on the rock strength and on the average negative buoyancy of magma for basaltic melt we estimate that this threshold thickness cannot be less than about 700 m and is 2 km on average

evidence for an active sinistral shear zone in the westeren alboran region a compilation of gravity seismicity neotectonics geology tomography and topography data from the alboran region reveals distinctive differences between the eastern and western part of the alboran region and betic cordillera calculated profiles of integrated crustal strength reveal that lateral differences in mechanical behaviour are caused by marked inherited differences in crustal make up the two domains with different tectonic behaviour are separated by a n025 trending lineament in the western alboran and central betic cordillera this lineament can be interpreted as an upper mantle lower crustal sinistral shear zone accommodating a large part of the convergence between africa and iberia

rheology of the lithosphere selected topics we review recent results concerning the rheology of the lithosphere with special attention to the following topics 1 the flexure of the oceanic lithosphere 2 deformation of the continental lithosphere resulting from vertical surface loads and forces applied at plate margins 3 the rheological stratification of the continents 4 strain localization and shear zone development and 5 strain induced crystallographic preferred orientations and anisotropies in body wave velocities we conclude with a section citing the 1983 1986 rock mechanics literature by category

a preliminary probabilistic seismic hazard assessment in terms of arias intensity in southeastern spain financiado por el grupo de investigacion peligrosidad sismica y microzonificacion de la junta de andalucia rnm 0217 y por el proyecto de la cicyt ries ctidib 2002 177

environmental evolution in sierra nevada south spain since the last glaciation based on multi proxy records abstract our knowledge of the quaternary landscape evolution in the high mountain areas of the iberian peninsula has substantially improved over the last decades the sierra nevada is one of the most studied mountain ranges in southern europe regarding its environmental evolution the purpose of the present paper is to integrate and summarize all the studies focused on the reconstruction of the palaeoenvironmental history in this massif since the last glaciation research has focused both on different sedimentary records and historical sources a wide range of geomorphological sedimentological and geochronological techniques have been used to characterize the glacial periglacial wetland and lacustrine records for palaeoenvironmental purposes for the last nine centuries tens of descriptions maps and sketches describe the landscape of the summit area of the sierra nevada providing evidences of the historical environmental events based on a multi proxy approach five periods have been identified last glaciation deglaciation holocene little ice age and recent evolution recent studies have detected the maximum expansion of glaciers in the sierra nevada around 30 32 ka bp predating the global temperature minimum no data about the environmental evolution is available between 20 30 ka bp around 19 20 ka bp glaciers advanced significantly the process of deglaciation was rapid and around 14 15 ka bp the massif was almost free of ice the late glacial promoted the formation of small glaciers in the highest northern cirques and widespread active periglacial processes i e rock glaciers during the holocene there has been an alternation of colder warmer periods and changing moisture conditions periglacial processes have been generally widespread in the summit area with an increasing or decreasing activity depending on climate conditions ephemeral reappearance of small glacial cirques occurred in the highest northern cirques during the coldest and wettest phases this is the case of the little ice age as revealed by historical documents and sedimentary records since the last decades of the xix century the temperature has increased 0 93 c leading to a decrease of the intensity of periglacial processes in the high lands of the sierra nevada

the pleistocene holocene transition and human occupation in the central andes of argentina agua de la cueva locality in the central andes of argentina evidences of early human occupations come from the precordillera a low mountain system which was under periglacial conditions prior to 14 000 14c yr bp when the cordillera principal and cordillera frontal were glaciated the corridors for human migration across the andes may have opened before 13 000 14c yr bp the pleistocene holocene transition gave rise to a substantial variability of environments and consequently of natural resources for early people who found in the precordillera new ecosystems with suitable conditions for living the first human groups arrived ca 11 000 14c yr bp at agua de la cueva rockshelter located at 2900 m above sea level in the western flank of the precordillera the occurrence of raw material outcrops close to the site and the archaeofaunistic record indicate a local and likely seasonal exploitation of mountain resources these early people lived in a shrub steppe environment under cooler and probably wetter conditions in which camelids were the most important food resource since 9000 14c yr bp warmer and drier conditions were dominant except for a lower intensity of human occupations the site function of agua de la cueva seems to have remained the same

a constant influx model for dike propagation implications for magma reservoir dynamics 1 most observations of seismicity rate during dike propagation on basaltic volcanoes show 1 rate stationarity despite possible variations of the dike tip velocity 2 frequent lack of clear and monotonic hypocenter migration following dike propagation and 3 event occurrences located backward with respect to the dike tip position on these bases the origin of the seismicity contemporary to dike intrusion within basaltic volcanoes cannot be solely related to the crack tip propagation seismicity rather appears to be the response of the edifice itself to the volumetric deformation induced by the magma intruding the solid matrix the volume change induced into the volcano edifice over time by the intruding magma is equal to the magma flux injected into the dike from the reservoir the consequence of this is that the stationary seismicity rate observed during the intrusion is a proxy for the magma flux withdrawn from the reservoir we consider a two phase dike propagation model including a first vertical propagation followed by a lateral migration along a lithological discontinuity we explore 1 under which geophysical conditions the vertical dike is fed at constant flow rate of magma and 2 dike propagation patterns implications entailed by constant volumetric flux on the piton de la fournaise volcano case study suggest a minimum size for the magma reservoir of about 1 km3 and a maximum value for the initial magma reservoir overpressure of about 2 2 mpa considering similar magma inflow rates during vertical and lateral dike propagation phases we reproduce independent estimates of propagation velocities rise times and injected volumes when applying the model to the august 2003 piton de la fournaise eruption

subcritical dyke propagation in a host rock with temperature dependent viscoelastic properties summary in this paper we examine the effects of temperature dependent viscoelastic properties of the host rock on the subcritical growth of a dyke from a magma chamber a theoretical relationship between the velocity of subcritical dyke growth and dyke length is established using a perturbation solution of stress intensity factor at the dyke tip and a viscoelastic crack growth theory in which the temperature dependent creep properties are taken into account the temperature field around the dyke is calculated using an analytic solution the numerical results for a dyke subcritically propagating from a magma chamber indicate that while the general dyke growth characteristics are similar to those with constant creep properties the subcritical dyke growth velocity is increased by an order of magnitude by considering the temperature dependence of the creep properties hence the subcritical growth duration before the dyke reaches the unstable growth state is significantly shortened

an incision wave in the geologic record alpujarran corridor southern spain almeria abstract the term incision wave was coined in the 1990s to describe wave like patterns of stream incision propagating through numerically modeled bedrock channel river systems an incision wave consists of a crest where available stream power is greatest and where vertical incision is most rapid the crest is flanked by limbs where there is less available stream power and where vertical incision rates are slower farther away from the crest available stream power is less and incision rates are slower than in the limbs modeling results suggest tectonically induced base level fall triggers incision waves that propagate upstream through bedrock stream networks however it has recently been postulated that the equation underpinning incision wave models cannot realistically simulate river systems this paper provides field geological evidence supporting the hypothesis that tectonically induced base level fall triggers incision waves that propagate through bedrock stream networks for tens of kilometers mid and late pleistocene alluvial morphostratigraphy in the rio andarax drainage basin southeast spain is interpreted to indicate that patterns of paleo stream power were controlled by an incision wave in the conceptual model proposed in this paper the signature of an incision wave in the rio andarax drainage network is recorded by the contrasting morphostratigraphy of oxygen isotope stage 8 ois8 time landforms at the crest of the incision wave during ois8 there is no record of a paleoalluvial level because available stream power exceeded critical stream power and streams were incising vertically the crestal area is flanked by ois8 time strath terraces which record the position of the two limbs of the incision wave farther upstream ois8 time alluvial fills mark an area unaffected by the incision wave during oxygen isotope stage 2 ois2 and or oxygen isotope stage 1 ois1 sediment availability in the rio andarax catchment was low and the pattern of relative stream power was threshold like rather than wave like differences in the manifestation of the incision wave during ois8 vs during ois2 and or ois1 indicate that climate and sediment availability can control how incision waves propagate through fluvial systems

temporal frequency distributions of alluvium in the american southwest taphonomic paleohydraulic and demographic implications abstract the use of radiocarbon frequency distributions to reconstruct prehistoric human and animal populations must account for taphonomic loss and other factors that affect the archaeological and paleontological records surovell et al jas 36 1715 1724 have recently proposed a correction for taphonomic bias that is based on the radiocarbon frequency of a global sample of volcanic deposits analysis of 717 radiocarbon dates sampled from the alluvium of the san pedro and santa cruz rivers and their tributaries in southeastern arizona shows that discovery and scientific biases also play an important role in the creation of radiocarbon frequency distributions and that the rate of taphonomic bias in prehistory is not predicted by the radiocarbon frequency of volcanic deposits the latter principle is further argued using a sample of 123 pliocene to clovis age proboscideans from the san pedro valley we propose an alternative model that is based on the nature of the stratigraphic record with discovery bias scientific bias taphonomic loss and the shape of the calibration curve all operating to influence the temporal frequency distribution of radiocarbon dated prehistoric phenomena

chronology of miocene terrestrial deposits and fossil vertebrates from quebrada honda bolivia abstract at 3500 m above sea level in the eastern andean cordillera quebrada honda basin exposes more than 300 m of middle miocene sedimentary strata developed on distal alluvial fan sediments interstratified with volcanoclastic deposits overlying paleozoic basement these deposits are rich in exotic vertebrate fauna adapted to a wetter and warmer climate at lower paleoelevation as contrasted with the present high elevation cold and dry andean conditions this study provides new magnetostratigraphic and 40ar 39ar age control of the quebrada honda rio rosario and huayllajara fossiliferous areas demonstrating that they are 13 1 12 4 ma part of the succession evidences cyclical deposition of calcretes and reddish mudstones which may be a response to precessional orbital forcing climatic processes paleomagnetic measurements show a significant clockwise tectonic rotation related to postdepositional tectonism associated with evidence of an important uplift after the deposition of quebrada honda sediments this uplift of the andean eastern cordillera was associated with the formation of the subandean fold thrust belt and the development of the amazon and la plata drainage basins proposed uplift rates of 200 m ma are compatible with well established rates of uplift recorded in contemporaneous alpine sections

coastal fan processes controlled by sea level changes a quaternary example from the tenryugawa fan system pacific coast of central japan a new hypothesis for dynamic processes in coastal fans is presented based on the concepts of temporal changes in fan morphology and associated sediment bodies in phased and cyclic mode these changes which are marked by overflows from a fan valley before its complete burial as well as after the initiation of its entrenchment are entirely related to relative sea level changes the hypothesis is exemplified by the middle pleistocene to holocene tenryugawa fan system pacific coast of central japan

when patagonia was colonized people mobility at high latitudes during pleistocene holocene transition abstract the pleistocene holocene transition was a critical time for the dispersal of human societies all over south america people looking for places to settle had to accept high environmental variability during the colonizing process the case studied for this paper is patagonia southern south america where the oldest dates ca 13 10 5 ka bp have been obtained for the peopling in the deseado river basin and magellan basin as well however two archaeological sites yielded similar dates on the western side of the andes monte verde and tagua tagua following archaeological and palaeoenvironmental data palynological faunal sedimentological and glaciological information as well as radiocarbon datings a hypothesis about the colonization of patagonia is presented analysing the ways and time of colonization for this region it is remarkable the coincidence of these ages in the centre of the steppe and close to the magellan strait even in the present tierra del fuego island though the eastern andean foothills seems to be occupied at least two millennia later it is proposed that independent peopling entries would have occurred both through the atlantic and pacific facades and that the andean foothills were colonized much later only when the available spaces allowed it

the initial peopling of central western patagonia southernmost south america late pleistocene through holocene site context and archaeological assemblages from cueva de la vieja site this article discusses new data on the initial peopling of central western patagonia based on research conducted at the cueva de la vieja site 45 16 27 s 71 32 24 w 718 masl contextualizing this event it in the broader pleistocene human dispersal of southernmost south america archaeological excavations and analyses at this cave site were undertaken to address the chronology of the initial settlement of the region characteristics of the first human presence and subsequent site redundancy this paper includes a description of the site context based on macro and microscopic stratigraphy of the excavated section the characterization of anthropogenic features and a comprehensive radiocarbon dating program archaeological assemblages i e lithics bones and charred seeds are used to explain the variations in the human occupation of this venue with particular emphasis on the earliest materials and occupational surfaces as well as post depositional processes the occupation events at cueva de la vieja span the last 12 000 calibrated years and indicate at this point the earliest securely dated human presence in central western patagonia at least one millennium after other thoroughly dated sites toward the east this suggests that the initial settlers must have occupied the eastern flank of the andes at this latitude only after glaciers and other glaciogenetic features retreated and viable ecosystems emerged

the baza fault a major active extensional fault in the central betic cordillera south spain in the guadix baza basin betic cordillera lies the baza fault a structure that will be described for the first time in this paper eight gravity profiles and a seismic reflection profile coupled with surface studies indicate the existence of a ne dipping normal fault with a variable strike with n s and nw se segments this 37 km long fault divides the basin into two sectors guadix to the west and baza to the east since the late miocene the activity of this fault has created a half graben in its hanging wall the seismic reflection profile shows that the fill of this 2 000 3 000 m thick asymmetric basin is syntectonic the fault has associated seismicity the most important of which is the 1531 baza earthquake since the late tortonian to the present i e over approximately the last 8 million years extension rates obtained vary between 0 12 and 0 33 mm year for the baza fault being one of the major active normal faults to accommodate the current ene wsw extension produced in the central betic cordillera the existence of this fault and other normal faults in the central betic cordillera enhanced the extension in the upper crust from the late miocene to the present in this regional compressive setting

the campo laborde site new evidence for the holocene survival of pleistocene megafauna in the argentine pampas abstract investigations have been carried out at the campo laborde archaeological site in the argentine pampas some issues related to pleistocene extinctions and the survivals of some species of megafauna into the early holocene are discussed at the site of campo laborde abundant bones of giant ground sloth megatherium americanum some from other pleistocene fauna doedicurus sp and neosclerocaliyptus sp and very few from extant fauna e g vizcacha lagostomus maximus patagonian hare dolichotis patagonum and peccary tayassu sp were found in association with two quartzite tools 128 microlithic debris from different raw material and two informal bone tools each of the species is represented by only one individual and only one bone of m americanum and one of d patagonum show cut marks different lines of evidence suggest that campo laborde is a giant ground sloth procurement site on the border of an ancient swamp where the prey was also initially butchered one of the recovered tools is the stem of a broken bifacial projectile point which would have been used as a hunting weapon based on the stratigraphic position this site could date to the early holocene six ams 14 c ages from m americanum bone collagen support this age although there is a wide chronological span between ca 9700 and 6700 bp the evidence obtained from campo laborde as well as from the la moderna site indicates that some pleistocene species such as giant ground sloth and some glyptodon d clavicaudatus and neosclerocaliyptus sp survived in the pampas until the early holocene therefore these megafauna coexisted with early hunter gatherers for several millennia and were exploited

megafauna extinction in south america a new chronology for the argentine pampas abstract the megafauna extinction in south america was one of the most profound events with the loss of 50 genera 83 three orders disappeared notoungulata proboscidea litopterna as did all large xenarthrans but how this fits into global extinction is uncertain mainly due to the lack of chronological resolution in recent years there has been an increase in the number of radiocarbon dating at archeological and paleontological sites but this information varies greatly from area to area in south america and few data can be considered to constitute a taxon date the timing of the late pleistocene extinction in the pampas is poorly established most taxa only appear in the biostratigraphic context and many reported 14 c dates do not meet rigorous criteria for accepting dates including reports suggesting survival of megafauna into the holocene in the present paper we evaluate the published radiocarbon dates in the pampas and present 20 new radiocarbon dates for paleontological sites in order to establish a more accurate extinction window for the key taxa these new dates are sufficiently robust to assess correspondences among last appearance records of megafauna first appearance records of humans and the younger dryas to holocene climatic transition in the argentine pampas these results highlight the need for greater effort in taxa selection for dating

timing and new geomorphologic evidence of the last deglaciation stages in sierra nevada southern spain abstract the main objective of this research is to improve knowledge of the deglaciation stages in sierra nevada southern spain by applying 36cl cosmogenic exposure dating to 28 samples from moraine and fossil rock glacier boulders and glacial polished surfaces in 5 glaciated valleys around veleta peak 3396 m asl 37 03 02 n 3 20 54 w the results show that shortly before the last glacial maximum lgm and during the lgm the heads of the glacial valleys were occupied by ice tongues with possible glacial transfluence between the valleys after 19 ka a major glacial regression started but glaciers during the oldest dryas od expanded again and refilled the valley bottoms the glacial advances of the pre lgm lgm and od formed polygenic moraine systems during the bolling allerod the glaciers receded and probably disappeared thereafter the valley bottoms remained ice free during the younger dryas yd small glaciers developed again but only in cirques shaped on east facing slopes subsequently these glaciers started retreating towards their valley heads and finally disappeared completely with the onset of the holocene rock glaciers developed inside the deglaciated cirques on the eastern slopes of some valleys but only under the most active and protected headwalls did large complex rock glaciers develop and remained active until the mid holocene

an analogue of dominance of tectonic over climatic forcing in intermontane coal bearing basins padul se spain abstract a multiproxy study based on sedimentology mineralogy magnetic susceptibility organic geochemistry and fossil content allowed to establish the sedimentary evolution of palustrine basins and to study the interplay between tectonic and climatic forcings in the sedimentation and facies arrangement that can be extrapolated to other coal bearing basins the reinterpretation of the data from 18 cores allowed to determine the facies distribution and to model the sedimentary evolution of the padul basin with the longest continuous continental quaternary record in the southwestern mediterranean region the padul basin sediment record and facies successions provide an outstanding example of tectonically and environmentally controlled sedimentation the sedimentary characteristics of the cores and thickness distribution revealed that recent tectonics was a more important forcing than other processes e g climate the influence of recent tectonics was determinant in facies arrangement that is to say that the activity of a rotated fault produced a differential subsidence causing more than 100 m of palustrine deposits to stack on the basis of the sedimentological record combined with data on the mineralogy fossil content magnetic susceptibility and total organic carbon three main sedimentary units were identified linked to diverse subsidence rates and paleoenvironmental oscillations the magnetic susceptibility was likely to have been controlled by the organic matter content toc values linked to oxic anoxic conditions in the lower part of the record unit a 107 0 68 7 m shallow lacustrine conditions were dominant with an important influx associated with considerable runoff from active alluvial fans linked to a higher subsidence rate unit b 68 7 37 6 m had a transitional character with a considerable decrease in the influence of the alluvial fan system the lake recharge through overland flow markedly diminished and pre existing groundwater recharge was dominant a sudden change to peaty materials indicated that surface runoff was directly diverted to the recently excavated durcal river gorge thereby precluding the basin from becoming a swampy environment with stagnant waters unit c upper 37 6 m was almost exclusively fed by bicarbonate groundwater and subsurface runoff through the highly permeable coarse alluvial fan deposits within these main sedimentary units minor mud peat shallowing upward sequences were identified

paleoenvironments in the paso otero locality during late pleistocene holocene pampean region argentina an interdisciplinary approach the recently excavated paso otero 4 site is located within the paso otero archaeological locality necochea district pampean region the site is characterized by the presence of a great variety of archaeological materials and a rich and complex stratigraphic record which allows use of an interdisciplinary approach the objective of this paper is to present the results of the geoarchaeological palynological phytolith and diatom analyses in order to reconstruct the paleoenvironmental conditions for the final late pleistocene through holocene these lines of research allow inference of paleoenvironmental and palaeoclimatic conditions on both local and regional scales at the site the rio salado member unit 2 where the archaeological deposit is buried underwent sudden and fluctuating changes in water availability conditions although the setting was basically characterized by calm depositional processes within and along the margins of interconnected lagoons paleoclimatic reconstructions indicate the existence of abrupt climatic changes throughout the sequence early holocene human occupations took place under regionally temperate warm climates while the end of the middle holocene witnessed cold and arid or cold temperate climates in general terms paleoenvironmental conditions inferred for paso otero 4 are in accordance with regional reconstructions proposed for the pampas

archaeological discontinuity in ultima esperanza a supra regional overview abstract the regional archaeological discontinuity between ca 11 761 272 cal bp and the beginning of the holocene at ultima esperanza chile will be discussed the absence of humans as measured by the deposition of artifacts on dated deposits was originally detected at the site scale especially at cueva del medio and cueva lago sofia 1 but recent excavations at several other sites extend it to the full scale of the cerro benitez locality it is suggested that this is not a case of abandonment of a colonized region but instead a case of discontinuation in the logistical use of a particular environmental patch accordingly the early holocene human presence in the cerro benitez locality is seen as the result of a new exploration by human foragers adapting to the increasingly forested environments of ultima esperanza

ams 14c dating of early human occupation of southern south america the time of appearance of a persistent and demographically viable hunter gatherer population in late pleistocene southern south america must be determined by evaluating evidence from as large as possible a sample of candidate archaeological sites in the region we co ordinated the ams dating of multiple bone and charcoal samples from previously excavated strata at the following sites arroyo seco 2 paso otero 5 piedra museo and cueva tres tetas all in argentina and cueva del lago sofia 1 and tres arroyos both in chile with one possible exception we did not obtain new results to confirm earlier observations of pre clovis age cultural activity at any of the sites considered in this study the possible exception arroyo seco 2 is considered in detail elsewhere politis g gutierrez m a scabuzzo c eds in press estado actual de las investigaciones en el sitio 2 de arroyo seco region pampeana argentina serie monografica incuapa 5 olavarria however our results for the samples which were the most preferred indicators of cultural events hearth charcoal and cut marked bone confirm that people were in the southern cone of south america at or soon after 11 000 bp 13 000 cal bp considered alongside recent age estimates for the clovis culture in north america these results imply the contemporaneous emergence of a consistent and archaeologically robust human occupation signal at widely separated locations across the western hemisphere such findings suggest that palaeoindian demic expansion may have involved more than one terminal pleistocene dispersal episode c 2008 elsevier ltd all rights reserved

past human populations and landscapes in the fuegian archipelago southernmost south america this contribution discusses possible relationships between human populations and holocene environmental deterioration phenomena cold arid pulses and volcanic eruptions in the fuegian archipelago south america based on summed probability distributions of archaeological dates paleoenvironmental information geospatial data and archaeological evidence during the first millennia after peopling only the hudson ca 7700 cal yr bp and the first monte burney ca 8600 cal yr bp eruptions might have played a role in human dispersion particularly a more intense human occupation around the beagle channel and long distance interactions are proposed as risk buffer strategies related to the hudson eruption a cooling phase and a demographic growth at ca 5500 cal yr bp might have favored more dispersed spatial occupations and a subsistence diversification in the beagle channel in the northern steppes the second monte burney eruption ca 4300 cal yr bp and an arid episode ca 2600 cal yr bp are proposed as the main triggers for changes in land use patterns long network interactions and subsistence strategies even though occupation changes in the fuegian archipelago coexist with environmental deterioration episodes after 1500 cal yr bp demographic processes and the european colonization most likely explain this trend similarities between the steppe ecotone and forest occupation curves suggest common behavioral patterns across the holocene

nature and impact of the neotectonic deformation in the western sierra nevada spain abstract the current high relief of the western sector of the sierra nevada was practically nonexistent before the tortonian as attested by the marine late neogene outcrops that reach a height of 1830 m which would easily surpass 2000 m if not for erosion the significant uplift produced over 3500 m has caused considerable thinning detachments and gravitational slides in the alpujarride units the general displacements of these movements are towards the wnw to ssw on the whole the morphology is fan like adapting itself to the border of the sierra nevada this border contains normal conjugate nw se and n s to nne ssw faults the latter also with sinistral strike slip character these faults have accommodated the uplift of the sierra nevada within an almost n s compressive context and linked e w extension this sector coincides with the western boundary of the nevado filabride complex and in its southern continuation with the western limit of the lower alpujarride units seeming to indicate a fault or faults reaching deep into the basement uplift has taken place unevenly over the last few million years with three noteworthy periods during the deposition of the block formation in the late tortonian towards the early middle pleistocene and in the middle late pleistocene this has resulted in considerable deepening of the fluvial net surrounding sierra nevada at the present time

quantification of the transient response to base level fall in a small mountain catchment sierra nevada southern spain 1 we integrated optically stimulated luminescence dating and 10be cosmogenic nuclide measurements to quantify short to medium term 102 104 years catchment dynamics and response to active tectonics in the 27 km2 rio torrente catchment sierra nevada southern spain rapid base level fall has triggered knickpoint migration up both trunk and tributary channels resulting in two distinct geomorphic zones 1 a steep lower catchment with concordant rates of hillslope erosion and channel incision over both short 100 years 5 8 mm yr 1 and medium 12 ka 5 1 mm yr 1 timescales and 2 a low relief soil mantled upland topography with uniformly low bedrock and hillslope erosion rates 0 05 0 02 mm yr 1 the uniformity of erosion in this upland surface indicates that catchment topography was previously in steady state rapid river incision below the channel knickpoints has resulted in the development of steep landslide dominated hillslopes that are essentially tracking the incising channel the magnitude of base level fall required to generate these steep hillslopes is 100 m at least 50 m of this base level fall occurred during the past 21 ka these steep hillslopes are eroding back into the low angled upland surface at a much slower rate than the channel knickpoint consequently the trunk channel knickpoint has already reached the catchment headwaters while hillslopes continue to adjust to the new base level indicating that the channel profile will regain equilibrium form long before hillslopes thus hillslopes are the limiting factor for the duration of landscape transience in this small mountain catchment

quaternary landscape evolution driven by slab pull mechanisms in the granada basin central betics abstract the granada basin is one of the largest neogene quaternary intramontane basins of the betic cordillera in se spain the landscape evolution in this basin is complex and does not respond to a simple model of headward erosion following river capture of a former endorheic catchment in the ne border of the basin the drainage network is highly incised and reveals two different stages of river development since the pleistocene the older drainage network presents low incision being locally controlled by ene wsw open folds the present day drainage network features deep incised valleys with a well defined local base level controlled by nw se normal faults the ene wsw open folds were generated by compressional stresses and affect a geomorphic surface that caps the local sedimentary sequence these folds are thought to reactivate a pliocene roll over formed in the hanging wall of ene wsw normal faults that bound the granada basin to the north and the deepest pliocene depocenter on the contrary quaternary depocenters are located in the hanging wall of the nw se oriented normal faults that control the present day drainage network nw se oriented the activity of these faults also contributes to the erosion of the pliocene depocenter located to the north thus suggesting a southwestward migration of the loci of extension to the center of the basin the broad scale scenario envisaged to explain the pliocene quaternary evolution of the ne border of the granada basin is one dominated by mantle slab pull coeval with the africa iberia continuous convergence

soil evolution over the quaternary period in a mediterranean climate se spain palaeosols in the granada basin se spain have been studied in two different situations surface soils on geomorphically stable surfaces since the early pleistocene with younger pedogenic overprinting and buried soils on unstable surfaces from the middle late pleistocene on which successive erosional depositional episodes have alternated with pedogenic episodes for each soil clay and iron accumulation indices the fet alt sit ratio clay mineralogy and micromorphological features were used to estimate the degree of soil development from the early to the early late pleistocene the main pedogenic processes were the leaching of carbonates weathering illuviation and rubification which resulted in bt horizons with red colours clay texture clay coatings and kaolinite neoformation the degree of weathering and the development of these bt horizons varied over time and the soils that formed on the surfaces from the early pleistocene show strongest weathering and development however after their formation there were periods in which they were partially truncated and recalcified resulting in polygenetic soils the different degrees of development of the buried soils during the last 474 000 years indicate that the wettest warm period was stage 7 and the driest stage 5 stages 9 and 11 must have had climates with intermediate wetness since the clay accumulation and iron oxide accumulation indices the differences in fet alt sit ratio between bt and c horizons the extent of kaolinite neoformation and the micromorphological features of the soils formed during stage 7 are all similar to the surface soils that formed on early pleistocene deposits these features cannot be used to date surfaces older than 242 000 bp by contrast the soils that formed during stage 7 and later periods show different extents of development and thus can be used for the approximate dating of landforms d 2002 elsevier science b v all rights reserved

neotectonic evolution of the central betic cordilleras southern spain abstract paleostress orientations were calculated from fault slip data of 36 sites located along a traverse through the central betic cordilleras southern spain heterogeneous fault sets which are frequent in the area have been divided into homogeneous subsets by cross cutting relationships observed in the field and by a paleostress stratigraphy approach applied on each individual fault population the state of stress was sorted according to main tectonic events and a new chronology is presented of the miocene to recent deformation in the central part of the betic cordilleras the deviatoric stress tensors fall into four distinct groups that are regionally consistent and correlate with three late oligocene aquitanian to recent major tectonic events in the betic cordilleras the new chronology of the neotectonic evolution includes from oldest to youngest the following main tectonic phases 1 late oligocene aquitanian to early tortonian 1 subhorizontal n s partly e w directed 3 subvertical compressional structures thrusting of nappes large scale folding and strike slip faulting in the alboran domain and the external zone of the betic cordilleras 2 early tortonian to pliocene pleistocene 1 subvertical 3 subhorizontal nw se partly n s directed or e w directed radial extension large scale normal faulting in the central betic cordilleras and in the oldest neogene formations of the granada basin related to the gravitational collapse of the betic cordilleras and the exhumation of the intensely metamorphosed rock series of the internal zones at the same time formation of the alboran basin and intramontane basins such as the granada basin 3 pleistocene to recent 3a 1 subvertical 3 subhorizontal ne sw with prominent normal faulting but coevally 3b 1 subhorizontal nw directed 3 ne sw subhorizontal with strike slip faulting extensional structures and strike slip faulting are related to the ongoing convergence of the eurasian and african plates and coeval uplift of the betic cordilleras reactivation of pre existing fractures and faults was frequently observed phase 3 is interpreted as periodic strike slip and normal faulting events due to a permutation of the principal stress axes mainly 1 and 2

late holocene environmental dynamics in fluvial and aeolian depositional settings archaeological record variability at the lower basin of the colorado river argentina abstract this paper deals with the way in which the environmental dynamics that took place in the lower basin of the colorado river buenos aires province argentina have affected the degree of archaeological resolution integrity and site preservation in different sectors of the study area e g coastal fringe delta and interior dune fields evidence from geomorphologic stratigraphic and sedimentary analyses as well as chemical parameters and zooarchaeological assemblages are used in order to propose spatial and temporal variations in the structure of the archaeological record these lines of evidence were also used for inferring general paleoclimatic trends the results obtained indicate that the inland landforms that contained initial late holocene archaeological assemblages 3000 1000 14c bp have suffered important morphodynamic processes that produced site destruction loss of organic material and lower degrees of integrity and site resolution conversely landforms located near the delta and the coastal fringe underwent more stable geomorphic processes e g pedogenesis that promoted better preservation resolution and integrity during the initial late holocene and particularly during the final late holocene 1000 250 14c bp the recognition of this pattern is crucial in order to evaluate demographic processes linked with the intensity and mode of hunter gatherer occupation of the area and population dynamics throughout time

the challenging application of cosmogenic dating methods in residual glacial landforms the case of sierra nevada spain abstract an accurate review of the literature on surface exposure dating methods shows evidence of the difficulty in applying cosmogenic dating methods to old moraines because of the intensity of late quaternary erosion processes moreover as in some previous cases we also found special difficulties in applying these methods to lia moraines caused by the intensity of current paraglacial processes the objective of this study is to apply cosmogenic dating methods to very old and very young moraines which in both cases have been or are being affected intensively by erosion with this purpose we collected samples of boulders from moraines corresponding to i the penultimate glaciation and ii the little ice age lia both from sierra nevada in the south of the iberian peninsula the sampling strategy was based on a preliminary accurate analysis of the geomorphological settings of two valley sites that resulted in the collection of only four boulder samples from an old moraine and three more from a very recent moraine using in situ produced cosmogenic 10be to date these boulders the old samples yielded an age of ca 130 135 ka for moraine stabilization the younger samples indicate that the lia moraine accretion probably occurred between the fourteenth and seventeenth centuries with a subsequent stage of accumulation during the nineteenth century as suggested by historical documents dating a glaciation that occurred prior to the last pleistocene glacial cycle and dating lia glacial stages are novel in the context of iberian glaciations and agree with other palaeoenvironmental studies in iberian and in other european mountains the limited number of boulders adequate for cosmic ray exposure dating prevents statistical methods to be applied and therefore highlights the need to improve geomorphological criteria in sample selection

multiple lines of evidence for possible human population decline settlement reorganization during the early younger dryas three approaches are used to test whether or not human populations across north america were affected by abrupt climate change and or other environmental factors associated with the onset of the younger dryas yd cooling episode at ca 12 900 cal bp they are 1 frequency analyses of paleoindian projectile points from across north america 2 time series of lithic assemblages from eleven paleoindian quarry sites in the southeastern united states and 3 summed probability analyses spa of radiocarbon dates from cultural human related sites across north america and parts of the old world the results of each analysis suggest a significant decline and or reorganization in human population during the early centuries of the yd varying in extent by region archaeological settings formerly heavily utilized such as stone quarries in the southeastern u s appear to have been largely abandoned while over large areas a substantial decline occurred in the numbers of diagnostic projectile points and cultural radiocarbon dates later in the yd beginning after about 12 600 cal bp there was an apparent resurgence in population and or settlements in many areas as indicated by increases in projectile points quarry usage and human related radiocarbon ages

late cenozoic landscape development and its tectonic implications for the guadalhorce valley near alora southern spain abstract landscape evolution is the result of a variety of geomorphological processes and their controls in time in southern spain tectonics climate and sea level fluctuations have been some of the main variables controlling long term late cenozoic landscape evolution in the guadalhorce valley malaga geomorphological reconstructions can be undertaken using sedimentary evidence from marine and fluvial deposits as well as erosional evidence such as terrain form and longitudinal profile analysis data are obtained and analysed from the upper miocene to present these allow reconstructions which add information and constraints to the uplift history and landscape development of the area main sedimentation phases are the late tortonian early pliocene and pleistocene important erosional hiatus are found for the middle miocene messinian and late pliocene to early pleistocene these phases of erosion and sedimentation resulted in a relative large and elongated tortonian marine valley filled with complex sedimentary structures next a prolonged stage of erosion of these deposits and incision of the major valley system took place during the messinian in the pliocene a short palaeo guadalhorce in a narrow and much smaller valley existed this valley was partly filled with marine sediments and prograding fan delta complexes during the pleistocene a wider and larger incising river system resulted in rearrangements of the drainage network evaluating the uplift history of the area we found that rates of tectonic activity were higher during the tortonian messinian and upper pleistocene while tectonic activity was lower during the pliocene relative uplift rates for the study area range for the messinian between 160 and 276 m ma 1 for the pliocene between 10 and 15 m ma 1 and for the pleistocene between 40 and 100 m ma 1

strain variations in a seismogenic normal fault baza sub basin betic chain insights from magnetic fabrics ams abstract ams and structural analysis are here applied to study the deformed zone associated with a large scale active normal fault in the central betic cordillera spain namely the baza fault system to determine i the kinematics of structures and their relation with fault zone architecture and segmentation degree ii the correlation between deformational structures and the different types of magnetic fabrics and iii the evolution of magnetic fabrics patterns from sedimentary to shear related associated with normal faults five outcrops 969 samples were analysed along the fault trace which shows different degrees of segmentation along strike and strong localization of deformation along narrow fault zones a first main set of magnetic fabric data corroborates the normal kinematics of the baza fault showing magnetic lineations parallel to the dip slip transport direction a second secondary set of magnetic lineations is parallel to the intersection lineation and can be related to less intense deformation in the fault rocks furthermore a detailed study 523 samples of a trench excavated across the fault zone where two fault splays tend to coalesce in a linkage relay zone indicates that i lithology and distance to fault planes are two factors that control the development of extension related magnetic fabrics in weakly deformed sediments ii the development of shear related fabrics in fault zones entails the mechanical rotation of minerals iii different orientation of magnetic lineations are related to different intensity of bulk deformation and iv magnetic lineation is useful to define local deviations of deformation axes produced by changes in the local extension direction from fault perpendicular to fault parallel extension in the linkage zone between adjacent fault splays

differential features of alluvial fans controlled by tectonic or eustatic accommodation space examples from the betic cordillera spain abstract the creation of accommodation space in subaerial sedimentary environments is closely linked to uplift the source area along basin margin faults or to a rise in base level depending amongst others on the relative importance of these two factors the margins of terrestrial sedimentary basins where alluvial fans develop produce aggradational progradational or retrogradational stratigraphic architecture we studied a total of 43 quaternary alluvial fans in the granada and bajo segura basins betic cordillera spain the analysis of their stratigraphic architecture and sedimentary facies has revealed the existence of three groups characterised by distinct stratal stacking patterns which is the result of differences in eustasy and tectonics the qualitative and quantitative analysis of these alluvial fans and their drainage basins has allowed us to define certain characteristic geomorphological patterns related in each case to the main mechanism operative in the creation of accommodation space these patterns are described as follows 1 alluvial aggradation is the main result of high tectonic subsidence with the development of quite open but small fans with a constant steep slope lacking incised channels and headward eroding gullies 2 in contrast when the principal mechanism in creating accommodation space is low tectonic subsidence progradation occurs and the fans are narrower and larger moreover the slopes of such fans are less steep in relation to the drainage area than in the above case being constant or even concave in longitudinal profile they also have short deep incised channels culminating downfan in a depositional lobe in inactive zones long deep headward eroding gullies develop 3 areas of extremely low tectonic subsidence and base level rise produce very open fans in the sedimentary basin although with a pronounced mountain embayment which gives them a characteristic mushroom shape in plan view in the latter case retrogradation is the typical stratigraphic stacking pattern and the fans are quite extensive with respect to their drainage areas usually showing a segmented longitudinal profile with a low gradient the feeder channels do not surpass stream order 3 and various extremely long and shallow incised channels can appear 4 contrary to the case of fans developing under a regime of subsidence when the accommodation is due to base level rise the fan slopes bear no relation to the extent of the catchment basins in such a case the overall fan slope is strongly influenced by the extent of the mountain embayment because it determines the distributions of debris and sheet flows over the alluvial surface

palaeoindian occupation of the atacama desert northern chile palaeoindian occupation of the atacama desert in northern chile has been found between 12 600 and 10 200 cal yr bp the new site at salar punta negra 24 28 s 60 53 w 2976 m includes about 1000 classifiable mostly unifacial artefacts and uniquely three different diagnostic types of early projectile points two of the lateglacial early holocene projectile types have wide distribution and are known from different geographical areas in south america the palaeoindian fell fish tail point mainly from the southern cone of south america and the triangular tuina points typical of the puna of the south central andes in northern chile and northwestern argentina in addition we found a third type a stemmed point typical for the salar punta negra filling a large geographical gap of fell occupation the site at salar punta negra provides evidence for generally much higher mobility and diversity of early cultures and supports an andean pacific route for early human exploration of south america to the south through the desert at intermediate altitudes contemporaneous high amplitude climatic changes were fundamental preconditions to provide adequate environments and habitats and to make palaeoindian hunting gathering occupation possible in the atacama desert copyright 2005 john wiley sons ltd

laboratory simulations of tensile fracture development in a volcanic conduit via cyclic magma pressurisation during volcanic unrest high magma pressure induces cracking and faulting of the country rock providing conduits for the transport of magma and other fluids these conduits known as dykes are fundamental structures for the transport of magma to the surface in volcanically active regions the mechanics of dyke propagation is not yet fully understood but is crucial to better model dyke emplacement and eruption in volcanoes central to this need is a greater understanding of the mechanical properties of the magma country rock interaction as a function of known magmatic pressure temperature and stress here we report data from a series of experiments in which we cyclically compress viscoelastic rhyolitic magma at 828 c 892 c and 918 c inside a cylindrical conduit like shell of basalt from mt etna italy until fracture occurs the compression is performed under strain rates cyclically varying between 5 10 6 and 5 10 5 s 1 the resultant monitored axial loading and relaxation illustrates how the presence of a visco elastic fluid magma controls the stress induced at the conduit margin boundary this is achieved by analysing the viscoelastic relaxation through time to calculate an apparent modulus which is found to decrease with both increasing temperature and time in the 4 cycles before failure we find that the apparent modulus decreases from 180 to 40 gpa 80 to 20 gpa and 8 to 1 gpa for imposed stress cycles at 828 c 892 c and 918 c respectively we theoretically estimate a tensile strength at failure of approximately 7 11 mpa consistent with recent field data and in agreement with a model derived from the sample geometry and basic material parameters post experimental neutron computed tomography and microscopic analyses further reveal the fragmentation of the melt and generation of tuffisite veins inside the conduit due to spontaneous crack nucleation associated with conduit wall fracture the geometry of the rupture area inside the melt is akin to a mach cone associated with supershear fractures we discuss our findings in terms of magma rock interaction leading to dykes tuffisite veins and magma fragmentation

timing of occupation and regional settlement patterns revealed by time series analyses of an archaeological radiocarbon database for the south central andes 16 25 s abstract developing spatially resolved high resolution datasets of robust long term changes in human demography constitutes a major challenge for archaeology one approach is to use the distribution of summed radiocarbon age probabilities to infer long term population dynamics i e palaeodemography however these can often be biased by preservation potential site taphonomy or researcher priorities among other aspects all of which require large datasets to resolve adequately for this report we have created such a dataset for the south central andes 16 25 s here termed the south central andes radiocarbon scar database scar spans the last 15 000 years and incorporates 1700 14c dates from 519 archeological sites reported across an extreme bioclimatic gradient that includes the hyperarid coastal atacama desert and adjacent cold high elevation altiplano among the possible methodological biases we first evaluated those related to calibration procedures otherwise changes in summed probability curves show no other relevant biases except for possible research interest priorities that could be responsible for the gaps in the record from the bolivian altiplano our temporally continuous time series indicates that prehispanic populations exhibited significant demographic changes during the last 13 100 cal bp except for coastal populations most regions show strongly coordinated demographic fluctuations that follow the same major patterns thus we identified two broad scale population events across the south central andes atacama inland bolivian altiplano from 13 100 4000 cal bp and then from 4000 cal bp to the present in contrast the atacama coastal records suggest a different and more variable occupation pattern over the last 13 460 cal bp which could be driven by the interaction with oceanographic processes i e upwelling a widespread major decline at 700 cal bp clearly predates the spanish colonization and occurs in all of our regions this widespread decline does not appear to be due to methodological biases and suggests that a population crash occurred before european occupation overall the scar database constitutes a valuable proxy for establishing the long term dynamics of prehistoric societies that inhabited the western andean slope time series analyses that use scar will shed new light on the demographic and cultural dynamics at different spatial scales and help clarify the processes involved in the migrational trajectories and cultural evolution of the peoples that inhabited the south central andes over the last 15 000 years