a vegetation history from the arid prepuna of northern chile 22 23 s over the last 13 500 years the quaternary paleoclimate of the central andes is poorly understood due to numerous discrepancies among the diverse proxy records that span this geographically and climatically complex region the exact timing duration and magnitude of wet and dry phases are seldom duplicated from one proxy type to another and there have been few opportunities to compare climatic records from the same proxy along environmental gradients vegetation histories from fossil rodent middens provide one such opportunity on the pacific slope of the andes we previously reported a vegetation history from the upper margin 2400 3000 m of the absolute desert in the central atacama desert of northern chile that record identified a distinct wet phase that peaked between 11 8 and 10 5 ka when steppe grasses and other upland elements expanded as much as 1000 m downslope and a secondary wet period during the middle to late holocene 7 1 3 5 ka the latter wet phase remains controversial and is not as readily apparent in our lowelevation midden record we thus sought to replicate both phases in a midden record from the mid elevations 3100 3300 m of the arid prepuna where slight precipitation increases would be amplified midden records from these elevations identify conditions wetter than today at 13 5 9 6 7 6 6 3 4 4 3 2 and possibly 1 8 1 2 ka dry phases occurred at 9 4 8 4 ka and possibly at ca 5 1 ka present floras and modern hyperarid conditions were established after 3 2 ka the records from the two elevational bands generally match with some important differences these differences could reflect both the discontinuous aspect of the midden record and the episodic nature of precipitation and plant establishment in this hyperarid desert 2003 elsevier science b v all rights reserved

origin of fibrous gypsum in the newark rift basin eastern north america abstract cores from the red beds constituting the upper triassic passaic formation a syn rift sequence in the newark basin display subhorizontal fractures veins filled with satin spar gypsum such veins are apparent in the shallow subsurface 100 300 m below present ground level but are not observed in outcrops or in quarries because of groundwater dissolution these fractures are roughly parallel to the present ground surface in the basin suggesting topographic influence on their formation fractures observed in cores are seen to crosscut stratigraphic boundaries indicating that the veins formed after stratal tilting and faulting and thereby post date the early late jurassic the gypsum crystals making up the vein fill grew perpendicular to the fracture walls suggesting that opening and filling of the fractures was contemporaneous and that the fractures are extensional that gypsum crystallizes from meteoric and connate waters and is derived by dissolution of associated evaporites is reflected in the d 18o 34s and 87sr 86sr isotopic compositions of the sulfate fractures are interpreted to be a result of unloading and exhumation fractures were initiated after major depositional and tectonic events took place and post date the late jurassic satin spar precipitated in those fractures carried in by gypsum saturated brines derived either by dissolution of the near surface sulfate evaporites or rehydration of more deeply buried anhydrite such satin spar veins are not evaporites but are composed of chemically remobilized sulfate

testing 87sr 86sr as a paleosalinity indicator on mixed marine brackish water and terrestrial vertebrate skeletal apatite in late paleocene early eocene near coastal sediments mississippi abstract mixed marine brackish water and terrestrial vertebrate skeletal apatite is found in the late paleocene early eocene tuscahoma and bashi formations of mississippi the co occurrence in these near coastal marine deposits of skeletal apatite with different provenances offers a unique opportunity for unraveling the effects of diagenesis on apatite 87sr 86sr composition with bearings on the use of this isotope pair as paleosalinity indicator the results show that the sr isotopes of all originally poorly ordered phases of skeletal apatite have extensively re equilibrated with pore water with significantly lower 87sr 86sr ratios than late paleocene early eocene seawater for example marine shark and ray teeth from the bashi formation all have clearly nonmarine 87sr 86sr ratios 0 7073 0 7075 compared with a coeval seawater ratio in the range 0 7077 0 7078 however separated shark tooth enamel with a high original crystallinity appears to have retained all or most of its in vivo sr isotopic signature until the present here we also show that 87sr 86sr results on recent vertebrate skeletal material from different environments are in good agreement with expected values for respective habitat earlier analyses of calcite material from the bashi formation indicated the existence of a shift in seawater 87sr 86sr to a lower value at the paleocene eocene boundary the strong influence of pore water with low nonmarine 87sr 86sr on the apatite in the bashi formation suggests that the proposed isotopic shift may be an artifact related to diagenetic processes

big sites short time accumulation rates in archaeological sites large complex archaeological sites are often characterized by only a handful of radiocarbon dates this practice encourages indiscriminant dating of sites for the sole purpose of determining age if a more rigorous dating scheme is employed and accumulation rates are calculated otherwise invisible aspects of human behaviour become apparent issues central to settlement pattern analysis such as abandonment and reoccupation events population fluctuations building activities and activity areas are more easily identified when accumulation rates are calculated in this study accumulation rates are calculated for seven shell midden sites found in the san juan islands washington the collections are stored at the burke museum of natural history and culture university of washington seattle washington eighty two charcoal pieces were selected according to a comprehensive horizontal and vertical sampling regime and radiometrically dated accumulation rate calculations suggest that large archaeological sites like these shell middens do not always represent continuous human occupation characterized by gradual accumulation of material rather these large complex sites accumulated during short duration occupations that were repeated infrequently in the same area this research recommends that numerical accumulation rates be calculated using at least two calculations the excavation unit accumulation rate and the entire site accumulation rate and that the excavation unit accumulation rate is the more useful scale for interpreting settlement history calculations of these rates focus the multifaceted interaction between human behaviour and natural processes in a way that qualitative guesses cannot

linking lacustrine cycles with syn sedimentary tectonic episodes an example from the codo formation late aptian northeastern brazil the codo formation exposed in the eastern grajau basin northeastern brazil consists mostly of black shales limestones and evaporites arranged into several shallowing upward cycles formed by progradation of lake deposits three ranks of cycles are distinguished the lower rank cycles correspond to millimetric interbeddings of bituminous black shales with evaporites calcimud stones or peloidal wackestone packstone grey green shale with calcimudstone peloidal wackestone packstone or ostracodal wackestone grainstone and ostracodal wackestone grainstone and or calcimudstones with cryptomicrobial mats and ooidal pisoidal packstones the intermediate rank cycles average 1 7 m in thickness and are formed by complete and incomplete cycles complete cycles show a transition from central to intermediate and then to marginal facies associations and include two types c1 cycle with central lake deposits consisting of evaporites and black shales and c2 cycle with central lake deposits formed by grey green shale complete cycles were produced by the upward gradation from central to marginal environments of the lake or saline pan sabkha system incomplete cycles are those where at least one facies association is lacking having been formed by successions either with central and intermediate facies associations i1 or intermediate and marginal facies associations i2 the higher rank cycles are on average 5 2 m thick and consist of four depositional units that display shallowing upward successions formed by complete and incomplete intermediate rank cycles that vary their distribution upward in the section and are bounded by sharp surfaces while the lower rank cycles display characteristics that reveal their seasonal signature detailed sedimentological characterization and understanding of stratal stacking patterns related to the intermediate and higher rank cycles support a genesis linked to syn sedimentary tectonic activity this is particularly suggested by the high facies variability limited lateral extension and frequent and random thickness changes of the intermediate rank cycles additionally the four higher rank cycles recognized in the codo formation match with stratigraphic zones having different styles of soft sediment deformation structures attributed to seismic activities therefore the several episodes of lake shallowing recorded in the codo formation are linked to seismic pulses that alternated with sediment deposition this process would have created significant changes in the lake water level and resulted in sharply bounded successions with upward gradation from deeper to relatively shallower facies associations

application of strontium isotopes to understanding the hydrology and paleohydrology of the altiplano bolivia peru abstract strontium concentrations and strontium isotopic ratios were measured in natural waters and carbonate sediments from throughout the bolivian and peruvian altiplano in order to improve hydrologic and paleohydrologic mass balances with the ultimate goal of better understanding the paleoclimatic history of the central andes rivers flowing into lake titicaca have a wide range of strontium isotopic ratios that exhibit spatial patterns consistent with the lithologies of the different drainage basins because of the limited exchange of water between the two main sub basins of lake titicaca lago grande and lago huinaimarca and between the sub basins of lago huinaimarca there are significant differences in strontium isotopic ratios between the sub basins calculated elemental balances of strontium in lake titicaca are in reasonable agreement with previously published budgets of water and major elements however the strontium isotopic budget indicates that the lake is not in isotopic steady state this also implies that the major element budgets are unlikely to be in steady state lake titicaca had a higher than modern strontium isotopic ratio during the early and middle holocene elevated values persisted in lago grande until at least 2000 cal yr bp consistent with other evidence that modern hydrologic conditions namely overflow were not established until that time an isotopic budget calculated for late pleistocene paleolake tauca in the central altiplano suggests that between 70 and 83 of its riverine inputs were derived from lake titicaca overflow this calculated flow represents about a 30 fold increase over the average discharge of the modern rio desaguadero at desaguadero or a seven fold increase over its average discharge into lago poopo the strontium isotopic budget if complete precludes the possibility that decreased evaporation alone could have accounted for the existence of paleolake tauca

seawater 87sr86sr for the late permian delaware basin evaporites new mexico u s a abstract the delaware basin southeastern new mexico u s a contains a thick section of marine evaporites the three uppermost units all of ochoan age of evaporites are in ascending order castile formation salado formation and rustler formation the castile consists predominantly of bedded and massive anhydrites the salado of massive halite with numerous interbeds of anhydrite sylvite and minor other units and the rustler of impure anhydrites gypsums halites silty and clayey units dolomites and others the previously established seawater 87 sr 86 sr curve for the late latest permian is marked by a dramatic increase from 0 7068 at 250 ma ago to 0 7072 by the permian triassic boundary data are not shown for rocks of approximate ochoan age however the results of our study show the following average 87 sr 86 sr values for the rocks samples castile 0 706880 0 000005 salado 0 70688 0 000004 and rustler 0 706976 0 000008 thus a systematic increase in 87 sr 86 sr is observed from castile to salado and especially to rustler consistent with a previous prediction these data are submitted for the seawater curve for the ochoan group upper evaporites of late permian age

evidence for temporal fluctuations in marine radiocarbon reservoir ages in the santa barbara channel southern california abstract differences in the 14 c ages of closely associated marine shell and carbonized plant material from stratified archaeological deposits on san miguel island california suggest holocene 10 000 present fluctuations in marine 14 c reservoir ages these fluctuations coincide with 18 o and 13 c shifts measured in mytilus californianus shells from the same stratigraphic contexts and general atmospheric oceanic circulation models for the region based on these data we make three primary observations 1 significant changes appear to have occurred in the radiocarbon reservoir during the holocene 2 these fluctuations appear to correlate with regional oceanographic changes and 3 high resolution 14 c dating of marine shells may require different r values for different periods of time

delta o 18 of fissurella maxima as a proxy for reconstructing early holocene sea surface temperatures in the coastal atacama desert 25 degrees s abstract fissurella maxima is a keyhole limpet that is abundant and well preserved in archaeological shell midden sites along the coast of chile making it an appropriate species to use for reconstructions of past sea surface temperature sst in the present study we evaluate the potential of f maxima shells as a proxy of sst by analysing 18o of modern shells collected alive from the atacama desert area of taltal 25 s and archaeological shells from two early holocene rockshelter sites 224a and paposo norte 9 reconstructed sst from modern f maxima shells were related to sst obtained from in situ thermometers supporting the use of this mollusc species as a paleotemperature archive mean sst reconstructed from early holocene archaeological shells 14 13 c was 2 86 c cooler than mean temperature recorded in modern shells 16 99 c mean sst reconstructed from modern shells was 1 04 c warmer than the mean temperature of in situ thermometers 15 95 c hence the paleo sst data from archaeological sites 224a and paposo norte 9 enrich the early holocene nearshore paleoceanographic scenario of the pacific coast of south america with mean sst cooler than present day sst our results validate the use of f maxima shells as a sst proxy and contribute to a better understanding of the latitudinal distribution of the coastal upwelling regime during the early holocene temporal changes in the structure of the humboldt current along the holocene and its influence on human adaptation through the prehistory of south america

origin of satin spar veins in evaporite basins abstract satin spar fibrous gypsum veins occur in rocks overlying evaporites in the amadeus basin australia appalachian basin usa cheshire basin england elk point basin canada palo duro basin usa paradox basin usa and zechstein basin england these antitaxial veins which are characterized by central partings and near vertical fibers fill horizontal and inclined fractures most satin spar veins occur in highly fractured or brecciated clastic strata that overlie or are associated with bedded halite anhydrite and gypsum saline springs are commonly present indicating that halite dissolution is active the similarities in morphology and occurrences of these veins suggest a common genesis satin spar veins result from several simultaneously active processes recharge of low salinity surface water results in dissolution of shallow 200 m to 750 m deep halite development of cavernous porosity and formation of extensional fractures in the rock column overlying salt dissolution zones greater solubility of anhydrite than gypsum at low temperatures and at salinities below halite saturation causes hydration of anhydrite to gypsum which takes place without significant volume change once groundwater is saturated with respect to gypsum any further anhydrite hydration and solution must result in supersaturation and the excess caso4 carried by ground water flowin from dissolution zones precipitates as gypsum in open high permeability fractures

deciphering the sedimentological imprint of paleoseismic events an example from the aptian codo formation northern brazil abstract a stratigraphic horizon bearing several styles of soft sediment structures occurs sandwiched within entirely undisturbed deposits in the lacustrine codo formation aptian located in the eastern part of the grajau basin northern brazil these deposits show a variety of sedimentary features distinguished according to their deformation style as follows from bottom to top a zone 1 consisting of widespread molar tooth structures i e fine grained spar filled cracks that are interconnected with small scale faults fissures and stylolites inclined at a high angle to bedding b zone 2 represented by complex convolute folds with lateral gradation of smooth synclines and anticlines into isoclinic folds and internal layers that retain the normal bedding features recumbent folds nappe folds with associated thrust faults pseudonodules and mound and sag structures c zone 3 consisting of normal faults and fissures that are vertical to near vertical show ragged morphology with small delicate peaks taper both downward and upward after a few centimeters and are associated with large up to 2 5 m long collapsed boulders and d zone 4 characterized by shales with irregular convolute folds these deformation zones are interpreted to reflect sediment rheology and alternating periods of sediment accumulation and deformation under the influence of synsedimentary seismic events as suggested mostly by 1 occurrence between undeformed deposits 2 lateral correlation for several kilometers of distance 3 similarity with other features formed in areas affected by seismic activity 4 presence of structures attesting to sediment deformation in an unconsolidated to semi consolidated state and 5 complex association of brittle and ductile deformation structures hence zone 1 records small scale cracking and faulting of early cemented cohesive deposits zone 2 is dominated by ductile deformation structures formed on water saturated unconsolidated sediments probably as a reflex of compressional stress zone 3 records a change in tectonic style to dominantly distension as evidenced by the horizon with normal faults finally zone 4 shows structures attributed to ductile deformation of water saturated muds which was probably formed during the same episode of deformation responsible for the faults and fissures in zone 3 this succession of deformation events appears to be consistent with transtensional and compressional shear stresses during the sedimentary evolution of the grajau basin

re evaluation of mid holocene deposits at quebrada puripica northern chile duringthe middle holocene 8 3 ka wetland deposits accumulated in areas with emerg ent water tables in the central atacama desert 22 24 s producinga stratig raphic unit unit c that can be mapped and correlated across different basins and geomorphic settings wherever mapped unit c is located between 6 and 30 m above modern wetlands and includes thick sequences of diatomite and organic mats the origin depositional environment and paleoclimatic significance of unit c is controversial and currently under debate grosjean science 292 2001 2391a suggests the unit developed under a regime of falling lake and ground water levels whereas evidence presented here suggests that unit c formed during a period of rising ground water levels and increased vegetation cover the debate is embedded in broader discussions about geomorphic processes in ground water fed streams as well as the history and forcingof climate variability in the central andes the central atacama and andes are remote with few opportunities for different researchers to examine the same site one exception is a sequence of mid holocene deposits at the confluence of quebrada seca and r o puripica in northern chile 23 s grosjean et al quat res 48 1997 239 246 initially suggested the deposits accumulated in temporary lake basins which formed when recurringdebris flows from a side canyon quebrada seca dammed the main channel r o puripica duringa period of drought and reduced stream flow upon our visit to the site we found evidence that clearly demonstrates the deposits were not formed in temporary lakes but rather were deposited in a wetland environment disagreement remains about the climatic interpretation of wetland deposits grosjean science 292 2001 2391a now suggests that local ground water levels rise and wetland deposits aggrade in deep canyon systems such as r o puripica when stream power and channel erosion is reduced duringprolong ed dry spells however sedimentological evidence and the presence of unit c in many depositional environments not just deep canyons indicate that it formed during a period of higher regional ground water levels that were sustained by enhanced precipitation and recharge in the high andes 2003 elsevier science b v all rights reserved

radiocarbon dating and the old shell problem direct dating of artifacts and cultural chronologies in coastal and other aquatic regions abstract archaeologists have long recognized the problem of the old wood effect in radiocarbon dating charcoal and wood samples the age of which may be hundreds of years older than their use by humans such problems have resulted in significant changes in how most researchers select wood and charcoal samples for 14 c dating with many now using relatively short lived carbonized materials for dating despite the significant strides made in our understanding of the potential biases of the old wood effect little emphasis has been placed on the possible impacts of dating old shell in archaeological deposits the use of marine shell for 14 c dating is widespread in coastal areas around the world including a growing emphasis on the dating of individual shell artifacts via accelerator mass spectrometry ams in dating shell artifacts we have obtained several dates older than associated 14 c dates for short lived subsistence remains from the same deposits including great disparities 10 000 years and more subtle differences 100 years these discrepancies appear to be due to the use of old shells by humans to make beads and other artifacts including shells collected from fossil deposits older archaeological sites and beaches the problems caused by the use of old shells to make beads and other artifacts are surmountable through careful sample selection analysis of multiple 14 c dates on a variety of materials and proper calibration procedures

reconstruction of the miocene western amazonian aquatic system using molluscan isotopic signatures abstract strontium isotopic ratios and sr contents of molluscs from the miocene pebas formation in colombian amazonia indicate that the bulk of the pebas formation was deposited in a freshwater environment predominantly draining the andes with minor contribution from the shield regions the molluscan oxygen and carbon isotopic composition does not provide a palaeosalinity proxy but points to a lacustrine palaeoenvironment the faunal character confirms such an interpretation sr isotopic ratios further suggest that a marine incursion that reached the area was composed of a mixture of shield derived freshwater and seawater with a maximum salinity of about 5 psu faunistic components of this incursion level support a shield seawater mixing the incursion most likely reached western amazonia from the north probably along the western guyana shield

marine radiocarbon reservoir age variation in donax obesulus shells from northern peru late holocene evidence for extended el nino for at least 6 m y el nino events have posed the greatest environmental risk on the peruvian coast a better understanding of el nino is essential for predicting future risk and growth in this tropical desert to achieve this we analyzed archaeological and modern pre bomb shells from the surf clam donax for the radiocarbon reservoir effect r to characterize late holocene coastal upwelling conditions in northern peru 8 14 s mean r values from these shells suggest that modern upwelling conditions in this region were likely established between a d 539 and a d 1578 our radiocarbon data suggest that upwelling conditions ca a d 539 were less intense than those in modern times the observed coastal water enrichment in 14 c may be consequence of frequent strong el nino events or extended el nino like conditions these r inferred marine conditions are in agreement with proposed extended el nino activity in proxy and archaeological records of ca a d 475 530 extended el nino conditions have been linked to political destabilization societal transformation and collapse of the moche civilization in northern peru a return to such conditions would have significant impacts on the dense population of this region today and in the near future

using archaeological shell middens as a proxy for past local coastal upwelling in northern chile abstract shell middens large heaps of refuse materials that are often interspersed with burials hearths and other cultural features provide important data regarding the lifestyles of past coastal and maritime dwellers despite the abundance of organic materials radiocarbon ages from shell middens can be a challenge to interpret because marine shells are depleted in radiocarbon with respect to their contemporaneous atmosphere known as the reservoir effect r this issue is particularly problematic in regions like the coastal atacama desert where the upwelling of subsurface radiocarbon depleted waters creates a shell local reservoir effect r with a time variable intrinsic uncertainty here we review and discuss how the dating of diverse materials from these deposits including the shells themselves can reveal large shifts between the terrestrial atmospheric and marine carbon cycles furthermore a chronology of such shifts can be used as a proxy of upwelling intensity and to help establish the duration of strong versus weak local upwelling episodes to test and evaluate these ideas we present a chronology of r and r variations from a 2 m shell midden sequence from caleta vitor in northern chile that spans the middle holocene which remains underrepresented by regional r values the 2000 y sequence of caleta vitor located onshore from a major upwelling center displays dramatic shifts in radiocarbon reservoir effects which we hypothesize are linked to strong changes in the intensity of local upwelling further replication of such archaeomalacological records will be key for not only solving methodological problems regarding the dating of coastal sites but can provide further insights into the evolving terrestrial and marine carbon cycles and how these relate to past climate change

a multidisciplinary analysis of shell deposits from saltes island sw spain the origin of a new roman shell midden abstract the analysis of shell deposits eroded by a ebb tide channel on saltes island tinto odiel estuary sw spain resulted in the identification of a new shell midden associated with the activity of a nearby roman factory over the 4th 5th centuries ce this midden differs from other old shell deposits sandy tidal flats cheniers washover fans in several features a its malacological content dominated by edible species mainly the bivalve glycymeris nummaria and differentiated by statistical analysis b a partial selection and better conservation of glycymeris nummaria linnaeus its most abundant species c the absence of microfauna which implies a previous washing to its final deposit and d an age concordant with the one deduced from the roman amphoraic remains found in this area and subsequent to the washover fans on whom it was deposited all these features together with the absence of both anthropic fractures or cooking would indicate that this roman shell midden was the end result of a trawling on subtidal glycymeris rich sandy bottoms with adjacent grasslands where the gastropod bittium reticulatum da costa was the most abundant mollusc this gastropod is the dominant species in the remaining shell deposits

abu dhabi sabkha persian gulf revisited application of strontium isotopes to test an early dolomitization model a study of brines and diagenetically altered minerals from coastal sabkha of abu dhabi persian gulf was undertaken to test the flood recharge evaporative pumping model for early dolomitization using strontium isotopes as a tracer the sup 87 sr sup 86 sr ratio of the sabkha brines defines a pattern of both horizontal and vertical mixing of coastal seawater and continental ground water consistent with a previously proposed model the sup 87 sr sup 86 sr ratio of the diagenetic dolomites indicates early dolomitization by marine recharge waters the sup 87 sr sup 86 sr ratio of gypsum from the dolomitization area 1 4 to 4 4 km from high tide mark and seaward reflects precipitation from marine brines but more landward 6 to 9 km gypsum and anhydrite record a continental signal in the minerals suggests a paragenetic evaporative sequence dolomite yields gypsum yields anhydrite the dolomitizing fluid is evaporated seawater that recharges the sabkha aquifer during supratidal flooding and is afterward pumped upward through the saturated zone by evaporative processes

radiocarbon dating and the old wood problem the case of the hohokam chronology abstract many archaeological chronologies including that of the hohokam in southern arizona are based on a series of radiocarbon dates on wood this paper argues that because of variability in rates of wood decay processes in the environment and in systemic context such archaeological chronologies are potentially biased towards excessive antiquity by an old wood problem and must be reassessed following the theoretical insights of dean 1978 this paper sets forth principles and procedures for relating radiocarbon dates to cultural events emphasis is placed on identifying and taking into account the formation processes of 1 the dated specimens and 2 the deposits that yielded them this methodological framework is applied to hohokam radiocarbon dates and a chronology much shorter than the original gladwin haury formulation is supported

using strontium isotopes to determine the age and origin of gypsum and anhydrite beds the variation of 87sr 86sr in seawater with time can be used to determine the age of calcium sulfate beds precipitated from brine derived from seawater the determination of a marine origin can be established by the consistency of strontium isotope results from samples at different stratigraphic levels in a single gypsum anhydrite bed collected at separated sites the scatter of strontium isotope results in the gypsum anhydrite samples examined here is interpreted to result from the contribution of meteoric strontium to the salina strontium isotope results from three evaporite settings the jurassic todilto formation from new mexico the permian blaine formation from blaine county oklahoma and the permian salado formation from new mexico are used to determine the age and origin of the parent brine for these gypsum anhydrite beds the calcium sulfate beds from each of these formations precipitated from salinas that originated with a marine flooding but show at different times and localities volume do

marine to non marine sedimentation in the upper miocene evaporites of the eastern betics se spain sedimentological and geochemical evidence abstract several neogene basins in the eastern betics contain a record of thick upper miocene evaporites the inner basins those located distal to the mediterranean coast include evaporite units ranging from the late tortonian to the early messinian whereas the marginal basins those located in the vicinity of the mediterranean coast include evaporite units corresponding to the late messinian that are linked to the salinity crisis the sedimentological and geochemical comparison of the evaporites in the inner and marginal basins enable us to show their differences in the modes of deposition under local structural controls and differentiated palaeogeography in the inner basins of the murcia alicante region a number of evaporite units have been differentiated whose gypsum lithofacies have 1 variable strontium contents with mean values primary gypsum between 1121 and 2380 ppm 2 isotopic compositions of sulphur 34 s ranging from those characteristic of the tertiary marine water 20 3 to 25 5 to those characteristic of the triassic sulphates 8 0 to 16 0 the latter suggesting recycling of the sulphate anion in meteoric waters intermediate values 17 4 to 19 6 are attributed to mixed mother brines and 3 strontium ratios 87 sr 86 sr comprised between 0 70804 and 0 70888 these values range from those of the tertiary marine water to those exceeding the triassic sulphates suggesting additional continental contributions from country rocks and hydrothermal solutions the comparison between the sulphur and strontium isotopic compositions of the sulphates together with the study of the biota present in the marls associated with the gypsum allows us to distinguish between marine continental and mixed units in the marginal basins of the eastern betics where single evaporite units characterized by selenitic gypsum prevail 1 the strontium contents are more homogeneous with mean values primary gypsum between 493 and 625 ppm 2 the isotopic compositions of oxygen 18 o and sulphur 34 s are comprised between 12 2 and 14 8 and between 22 0 and 23 5 respectively and 3 the strontium ratios 87 sr 86 sr vary from 0 70890 to 0 70895 all these isotopic values reveal a marine origin and the lack of contribution of significant continental water during the late messinian evaporite deposition in the betic strait these characteristics are similar to those of the lower evaporite

on the influence of topography in the induction of coastal upwelling along the chilean coast the contribution of the winds and the topography in the induction of upwelling along the chilean coastal zone is calculated the topographic induced upwelling is estimated taking into account the effect of the meridional changes of the coastline orientation the wind induced upwelling was calculated for the austral summer using nscat scatterometer data resulting a total amount of 2 1 106 m s 1 of water transported offshore for the whole chilean upwelling zone it is shown that the topographic effect dominates the wind induced upwelling in several parts of the chilean coast particularly at 23 s antofagasta 25 5 s 30 s coquimbo 33 s valparaiso and 37 s concepcion antofagasta coquimbo valparaiso and concepcion are well known zones of intense upwelling the results show that the topography plays a key role in the upwelling of the chilean coast specially in its northern part

a late pleistocene human presence at huaca prieta peru and early pacific coastal adaptations abstract archaeological excavations in deep pre mound levels at huaca prieta in northern peru have yielded new evidence of late pleistocene cultural deposits that shed insights into the early human occupation of the pacific coast of south america radiocarbon dates place this occupation between 14 200 and 13 300 cal yr bp the cultural evidence shares certain basic technological and subsistence traits including maritime resources and simple flake tools with previously discovered late pleistocene sites along the pacific coast of peru and chile the results help to expand our knowledge of early maritime societies and human adaption to changing coastal environments

evaporites marine or non marine division of evaporites into those types that retain information about primary mineralogy textures and structures primary evaporites and those types so extensively altered that few or no primary features remain secondary evaporites only primary evaporites can give unequivocal data bout their marine or non marine origin to help evaluate such primary deposits they have been further divided using the following attributes 1 whether the depositional setting was marine or non marine 2 whether the source water was a seawater b meteoric c hydrothermal d diagenetic e volcanogenic or f mixed specific criteria for making distinctions are 1 kinds of fossils 2 sedimentology of the associated non saline facies 3 kinds of primary saline minerals 4 association of such saline minerals both in qualitative and quantitative terms 5 trace element isotope and fluid inclusion geochemistry of such saline minerals modified journal abstract

marine to nonmarine facies transition in permian evaporites of the palo duro basin texas geochemical response the late paleozoic palo duro basin evolved from a marine to nonmarine environment as it was infilled the evaporitic part of the sequence leonardian through ochoan is composed of regressive carbonate anhydrite halite cycles that displaced open marine environments toward the south during basin filling systematic vertical changes in evaporite geochemistry through the evaporite section include increasing 87sr 86sr ratios and decreasing altered from marine 34s in anhydrite decreasing recycled bromide content of the halite and increasing meteoric influence on the stable isotopic composition of fluid inclusions in halite geochemical changes correspond to changes in evaporite sedimentology and document the evolution from marine dominated to partly nonmarine evaporites geochemical tracers when used with sedimentological and facies analysis provide reliable indicators of the sources of water and solutes in an anhydrite halite facies tract perennial intermittently stratified and ephemeral brine pool conditions affect the amount of synsedimentary recycling variable rates of reflux and marine recharge control residence times of brines in the depositional environment these are two key processes in relating evaporite geochemistry to depositional environment

an upper aptian saline pan lake system from the brazilian equatorial margin integration of facies and isotopes facies and isotope sr and s data were combined in order to discuss the genesis and palaeohydrology of an upper aptian evaporite succession formed during the initial development of an intra continental rift from northern brazil comparison of facies distribution between two investigated areas shows i stable well stratified and hypersaline lakes with periods of anoxia and closure in the eastern margin of the basin where there was evaporite precipitation only in central lake environments and ii more ephemeral conditions in the eastern margin of the basin where a saline pan complex developed and evaporite precipitation took place mainly in marginal salinas and surrounding mudflats in both areas expansion contraction cycles developed as sedimentation took place accompanied by a decrease and then an increase in 87 sr 86 sr and d 34 s isotope values this combined with the wide distribution of sr and s isotope data within individual depositional cycles as well as petrographic and scanning electronic microscopic sem images led to the conclusion that diagenesis was not enough to obscure the primary geochemical signature a non marine brine source is suggested by 87 sr 86 sr ratios between 0ae707824 and 0ae709280 which are higher than those from upper aptian sea water i e between 0ae70720 and 0ae70735 the d 34 s value varies from 16ae12 to 17ae89 in the eastern margin of the basin which is in disagreement with upper aptian marine values 13 to 16 both geochemical tracers were influenced by facies characteristics and thus a model is provided where 87 sr 86 sr values respond to changes in expansion and contraction

stable δ13c δ18o and strontium isotopes through the paleocene at gebel aweina eastern tethyan region abstract stable 13 c 18 o and strontium 87 sr 86 sr isotopic records have been established through the paleocene section at gebel aweina in the eastern desert egypt the section has been formed in a shelf upper bathyal environment and spans the interval from planktonic foraminiferal zones p1d to p6a or p6b integrated evaluation of isotopic results and scanning electron microscope observations suggest that strontium and whole rock 13 c records reflect primarily original isotopic trends whereas 18 o and foraminiferal 13 c values have been severely affected by diagenesis the whole rock 13 c record exhibits a continuous increase of 4 from the early paleocene to middle late paleocene the increase is followed by a stepwise 13 c decrease of the same magnitude through the late late paleocene and onwards the gross trends of this 13 c record have earlier been registered in many coeval deep sea sections but there are also some significant disparities at aweina for example the paleocene carbon isotopic changes have a higher amplitude in the deep sea the mid to late paleocene 13 c increase has been interpreted to reflect high biological productivity and or changes in the global carbon mass balance the 13 c decrease in the upper part of the aweina section can be identified as the paleocene eocene transitional long term 10 3 kyr negative 13 c shift which may reflect a major reorganisation in global oceanic circulation patterns the well known latest paleocene deep sea benthic foraminiferal extinction event has been found in the upper part of the aweina section and coincides with a distinct and rapid 13 c decrease of 1 5 the benthic extinction event and the associated 13 c anomaly thus represent important stratigraphic markers also in more shallow environments the gebel aweina 13 c record shows considerably lower values compared to the global 13 c record during early and early late paleocene and in the latest paleocene in the early late paleocene foraminiferal zones p3a to the base of p4 the aweina 13 c values increase rapidly by 1 5 and converge with the global record thereafter the two records covary up to the benthic extinction event after which they diverge the convergence between the records may reflect sea level rise and more open water mass exchange between the eastern tethys and the world ocean the similarity of pilot 13 c records from greece and tunisia with the aweina record support this interpretation diagenetic processes however cannot be ruled out and further studies are required to determine the significance of the 13 c depletions in the eastern tethyan sediments the 87 sr 86 sr ratios through the paleocene at gebel aweina are remarkably invariable close to a value of 0 7077 this is the same trend that has been reported in some earlier detailed studies conducted on well preserved calcitic material from the paleocene indicating original sr isotopic signatures at gebel aweina the homogeneity of sr isotopic ratios throughout the paleocene contrasts with the prominent changes observed in the carbon isotope record indicating a decoupling of the mechanisms regulating the mass fluxes of these elements the invariable sr isotopic ratios suggest stable conditions as regards to relative changes in mass fluxes of riverine and or hydrothermal sr during the paleocene

late pleistocene human occupation of the hyperarid core in the atacama desert northern chile abstract few archeological sites in south america contain uncontroversial evidence for when the first peopling of the continent occurred largely ignored in this debate extreme environments are assumed either as barriers to this early wave of migration or without potential for past habitability here we report on a rare 12 13 ka human occupation from quebrada mani site qm12 a plantless near rainless landscape 1240 m asl and 85 km from the pacific ocean located in the hyperarid core of the atacama desert this location harbored wetlands and riparian woodlands that were fed by increased rainfall further east in the central andes during the latest pleistocene excavations at qm12 yielded a diverse cultural assemblage of lithics burned and cut bones marine gastropods pigments plant fibers and wooden artifacts alongside a prepared fireplace sixteen radiocarbon dates from site qm12 on charcoal marine shells animal dung plant remains and wood reveal that the occupation took place between 12 8 and 11 7 ka these results demonstrate that the atacama desert was not a barrier to early american settlement and dispersal and provide new clues for understanding the cultural complexity and diversity of the peopling of south america during the last glacial interglacial transition

temporal variability in the holocene marine radiocarbon reservoir effect for the tropical and south pacific understanding the marine radiocarbon reservoir effect i e marine radiocarbon reservoir age r and or correction r is important for the construction of robust radiocarbon chronologies for marine archives for various research areas including archaeology palaeoecology paleoceanography quaternary research and climate change studies in this study we examined temporal r variability for the south china sea scs and the great barrier reef gbr during the past 8 1 ka based on 14c analysis of 230th dated corals results show large r variations of 410 yr and 490 yr for the scs and the northern gbr for 5 5 8 1 ka and 5 5 7 ka respectively and a smaller r variability of 200 yr for the scs for 2 3 5 ka our data together with those previously published for the tropical and south pacific indicate that variability in ocean upwelling bringing old subsurface waters to the surface and or changes in the sources or 14c level of the upwelled waters are responsible for seeing large r variations in coastal areas along the eastern pacific and the tropical east pacific tep of several hundred to a thousand years mostly during the early to middle holocene r variations in the central and western pacific of several and a couple of hundred years during the middle and late holocene respectively might be due to variability in pacific wide ocean circulation associated with climatic changes controlling the spread of upwelled waters from the tep to the west this mechanism together with local regional effects such as changes in ocean upwelling in the scs resulting from east asian monsoon variability and changes in upwelling and or horizontal advection in the northern gbr associated with variability in the el nino southern oscillation might be responsible for the observed r variations in these areas the results of our study also indicate the need for regional marine radiocarbon calibration curves for improved radiocarbon dating of marine samples as the observed holocene r values for the tropical and south pacific are not fully reproduced by a recent modelling work using a 3d ocean model which takes into account climate change effects ocean circulation changes were included in the model for the period of 11 5 50 cal kyr bp but possibly not considered or not well represented for the holocene which might explain the differences between the observed and modelled r values

shell midden sclerochronology abstract sclerochronological analysis of shell midden faunal remains offers a unique opportunity to study climate and environmental change in relation to human activity middens exist near most aquatic habitats almost worldwide for much of the late pleistocene and holocene they afford good preservation of accretionary calcium carbonate remains such as mollusk shells and fish otoliths in comparatively well dated contexts as such midden samples are a source of sequential proxy records of past climate and environmental conditions and may provide detailed pictures of human environment interaction however midden samples present several challenges to the development and application of sclerochronological proxies including unique taphonomic concerns here these challenges are outlined within descriptions of the major applications of midden sclerochronology archeological concerns including season of capture reconstructing the history of anthropogenic environmental impacts and paleoclimate environment proxy reconstructions

retention of hunter gatherer economies among maritime foragers from caleta vitor northern chile during the late holocene evidence from stable carbon and nitrogen isotopic analysis of skeletal remains abstract on the basis of stable carbon and nitrogen isotope analysis of human remains this paper provides evidence for the retention of hunter gatherer economies among coastal inhabitants in northern chile during the late holocene at the same time that inland populations were adopting agricultural economies coastal diets from the caleta vitor region of the atacama desert were dominated by marine based foods predominantly from upper trophic levels the focus on reliable marine food resources is interpreted as a risk minimisation strategy in this marginal arid environment although these coastal hunter gatherers adopted other goods and traditions from agricultural populations their participation in this larger interregional exchange network did not affect their basic subsistence economies associated new radiocarbon dates from the site are also discussed skeletal remains and artefacts associated with the caleta vitor shell middens generally originate from sites with dates ranging from c 9000 476 bp however the human remains that are the subject of this research cover the time period c 4000 476 bp

deposition and early alteration of evaporites summary the depositional settings for primary and early diagenetic evaporite deposits generally fall into three categories marginal mixed shallow subaqueous and subaerial shallow and deep subaqueous these three environmental groupings hold for both marine and nonmarine settings although the details of continental evaporites may be far more complex than in most marine fed water bodies the primary evaporite morphologies from many continental playa hypersaline marine and marine marginal depositional settings are reasonably well understood because of the numerous detailed studies of recent holocene and cenozoic deposits that serve as models for sedimentary interpretation the sedimentological features that develop in deeper water settings are inferred based on examination of unaltered cenozoic deposits each environmental setting develops characteristic depositional features and patterns and one facies grades into the next because there may be significant physiochemical changes in water composition during deposition as well as sudden change s in both water depth and basinal circulation description and interpretation of evaporative rocks should not be based on mineralogy alone but on the distinct sedimentary characteristics of each part of a deposit in cases where sediments still reflect their primary mineralogy and morphology most of the environments can now be recognized however geochemical studies are commonly required to determine the source s of the original water the determinative geochemical techniques that presently serve as a support to sedimentologic study include studies of fluid inclusions bromine content of chloride salts and the stable isotopes of strontium sulphur carbon and oxygen only after these and perhaps other chemical analyses are considered can the full depositional history of a region be reasonably unravelled

marine radiocarbon reservoir effect along the northern chile southern peru coast 14 24 s throughout the holocene abstract through an extensive sampling and dating of pairs of associated shells and charcoal fragments combined with reanalysis of all the available previous data we reconstruct the evolution throughout the holocene of the regional marine radiocarbon reservoir effect r values along the northern chile southern peru area 14 24 s after elimination of the cases in which the terrestrial component yielded older ages than the marine shells to which they were associated the study is based upon data from 47 pairs of associated marine and terrestrial material our results suggest major changes in both the magnitude and variability range of r during the whole holocene period 1 between 10 400 and 6840 cal yr bp high values 511 278 yr probably result from a strengthened se pacific subtropical anticyclone and shoaling of equatorial subsurface waters during intensified upwelling events 2 between 5180 and 1160 cal yr bp lower values 226 98 yr may reflect a major influence of subtropical water and diminished coastal upwelling processes 3 during the last thousand years high values between 355 105 and 253 207 yr indicate an increased influence of 14 c depleted water masses and of enso for the early twentieth century a r value of 253 207 yr was calculated

scale of time averaging in archaeological shell middens from the canary islands characterizing the degree of disturbance in archaeological deposits is critically important for archaeologists assessing foraging strategies environmental conditions or behavior patterns of ancie

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