interhemispheric climate links revealed by a late glacial cooling episode in southern chile understanding the relative timings of climate events in the northern and southern hemispheres is a prerequisite for determining the causes of abrupt climate changes but climate records from the patagonian andes1 2 3 4 and new zealand5 6 7 8 for the period of transition from glacial to interglacial conditions about 14 6 10 kyr before present as determined by radiocarbon dating show varying degrees of correlation with similar records from the northern hemisphere it is necessary to resolve these apparent discrepancies in order to be able to assess the relative roles of northern hemisphere ice sheets and oceanic atmospheric and astronomical influences in initiating climate change in the late glacial period here we report pollen records from three sites in the lake district of southern chile 41 s from which we infer conditions similar to modern climate between about 13 and 12 2 14c kyr before present bp followed by cooling events at about 12 2 and 11 4 14c kyr bp and then by a warming at about 9 8 14c kyr bp these events were nearly synchronous with important palaeoclimate changes recorded in the north atlantic region9 supporting the idea that interhemispheric linkage through the atmosphere was the primary control on climate during the last deglaciation in other regions of the southern hemisphere where climate events are not in phase with those in the northern hemisphere local oceanic influences may have counteracted the effects that propagated through the atmosphere

littoral landforms and pedosedimentary sequences indicating late holocene lake level changes in northern central europe a case study from northeastern germany abstract a multidisciplinary study was carried out at lake groser furstenseer see lfs in order to explore the potential of littoral sediments palaeosols and landforms as indicators of historical lake level changes this research was initiated to investigate the extent to which lakes in northern central europe responded hydrologically to climatic and land use changes in the last millennium specific landforms investigated comprise lake terraces beach ridges local basins peatlands and dunes revealing a wealth of sedimentary sub environments at the lakeshore eleven sections were recorded with subsequent sedimentological pedological geochronological osl 14c and palaeobotanical pollen macro remains analyses most of the pedosedimentary littoral sequences show a succession of basal glacial sand intermediate palaeosols and lacustrine sand on top a broader number of semi terrestrial buried palaeosols along the lakeshore were systematically identified and analysed providing evidence for changing hydrological conditions during the late holocene additional historical data from the last centuries e g maps aerial photos public records allow the lake levels reconstructed from geoarchives to be connected with modern gauging data all local data sources available enable a tracing of lake level changes of the lfs during the last millennium comprising periods of relatively low c 1200 ad 2000s ad and relatively high water levels c 1250 1450 ad c 1780 ad 1980s ad the amplitude of lake level changes during the last c 1000 years amounts to c 3 m so that the fluctuations of the last 30 years recorded by lake level monitoring only reflect a small amount of the potential variability regional climate and local land use history suggest that the medieval lake level dynamics of lfs were primarily governed by climate and secondarily influenced by human impact on the drainage system at present the lake level is additionally influenced by the impact of highly water consuming pine plantations in the catchment area the regional significance of the local development at lfs can be demonstrated by comparison with other regional and supra regional lake level data the present study underlines the potential of a closer examination of the littoral zone for lake level reconstructions with high altitudinal precision

the flank margin model for dissolution cave development in carbonate platforms the bahama islands contain many abandoned dissolution caves at elevations between two and seven metres above current sea level the development of dissolution caves in tropical carbonate islands is dependent on the position and nature of the freshwater lens lens position is controlled by sea level which in stable carbonate platforms like the bahamas is a function of glacioeustatic sea level still stands caves in the bahamas that are currently subaerial must have developed during past higher sea levels during the late quaternary sea levels higher than present have been relatively short lived and that limits the amount of time that a freshwater lens could be situated at the elevation required for the cave formation the bahama islands are low lying landforms where only aeolian ridges extend to elevations higher than six metres above current sea level past high sea level events greatly reduced the exposed land area of the bahama islands thus also limiting both the catchment for and size of freshwater lenses caves must be younger than the rock in which they are developed most subaerial bahamian caves are found in limestones that are less than 150000 years old development of large dissolution caves under these limitations of time and lens size requires a powerful dissolutional mechanism the mixing of discharging freshwater with tide pulsed incoming marine water under the flanks of emergent dune ridges may have produced the conditions necessary bahamian caves formed by this process are phreatic chambers with complex interconnections and blind tubes their presence demonstrates that significant dissolution can occur rapidly as a result of the mixing of fresh and marine waters beneath small carbonate islands

variability of el nino southern oscillation activity at millennial timescales during the holocene epoch the variability of el nino southern oscillation enso during the holocene epoch in particular on millennial timescales is poorly understood palaeoclimate studies have documented enso variability for selected intervals in the holocene but most records are either too short or insufficiently resolved to investigate variability on millennial scales1 2 3 here we present a record of sedimentation in laguna pallcacocha southern ecuador which is strongly influenced by enso variability and covers the past 12 000 years continuously we find that changes on a timescale of 2 8 years which we attribute to warm enso events become more frequent over the holocene until about 1 200 years ago and then decline towards the present periods of relatively high and low enso activity alternating at a timescale of about 2 000 years are superimposed on this long term trend we attribute the long term trend to orbitally induced changes in insolation and suggest internal enso dynamics as a possible cause of the millennial variability however the millennial oscillation will need to be confirmed in other enso proxy records

similarities and dissimilarities between the dynamics of sand and dust during wind erosion of loamy sandy soil abstract aeolian dynamics were measured during a wind erosion event on an agricultural field in northern germany because the topsoil was loamy sand particle flow behaved as a sand dust mixture and not as pure sand 63 m or pure dust

the gomphotheres proboscidea gomphotheriidae from pilauco site scavenging evidence in the late pleistocene of the chilean patagonia the archaeo paleontological site of pilauco southern chile has one of the richest late pleistocene mammal records of the northern chilean patagonia with at least nine forms dominated by gomphothere remains this site has a complex taphonomic history due to postdepositional processes that affected the integrity frequency and distribution of the fossil bones one of these processes is the action of large carnivores indicated by tooth marks recorded exclusively in gomphothere bones in this paper we describe gomphotheriidae fossil remains and give a detailed description of carnivore tooth marks detected in the sample the absence of diagnostic fossil specimens does not allow genus or species assignment the type location intensity and dimensions of the tooth marks are compatible at least with a large felid which probably scavenged a partially exposed carcass the record of this taphonomic feature is important in order to understand the postdepositacional history of the pilauco site in which natural and cultural agents are involved

porosity development in coastal carbonate aquifers geochemical mixing theory suggests that the mixing of seawater and calcite saturated fresh ground water can result in a solution that is undersaturated with respect to calcite previous studies of the mixing of such waters in carbonate rocks along certain coastlines have indicated that this mixing effect may be responsible for significant amounts of calcite dissolution and porosity development in this study potential rates of porosity development by calcite dissolution are assessed by combining geochemical mixing theory with the hydrodynamics of fresh water salt water mixing zones in a coupled reaction transport model results from the reaction path model phreeqe are used with a variable density ground water flow and solute transport model to simulate an idealized cross section of a coastal carbonate aquifer results of the simulations indicate that the dissolution process is sensitive to fresh water chemistry ground water velocities and sea level movement dissolution potential was evaluated at three field sites and evidence from those sites is in general agreement with the simulation results dissolution rates indicated by the model show that under the proper conditions this dissolution mechanism can produce significant increases in porosity over relatively short spans of geologic time tens of thousands of years

postglacial vegetation fire and climate dynamics at central chilean patagonia lake shaman 44 s a 19 cal ka bp pollen and charcoal record from lake shaman 44 s 71 w chile was analyzed to establish vegetation fire and climate dynamics of the forest steppe ecotone in central chilean patagonia lake shaman record indicates that the upper rio cisnes valley was free of ice at around 19 cal ka bp from this date and until 14 8 cal ka bp a grass steppe with high proportions of shrubs associated to colder and drier conditions than present developed in this area a continuous increase of nothofagus accompanied by a decline in the steppe shrubs and sudden dominance of paludal over aquatic plants from 11 cal ka bp was associated to effective moisture increase but still under modern values the replacement of the cold dry grass shrub steppe by a similar than present forest steppe ecotone suggests an increase in temperature indicating the onset of the holocene at the same time moderate fire activity suggested by the charcoal record could be related to major fuel availability as consequence of nothofagus forest expansion between 8 and 3 cal ka bp the record indicates the easternmost position of the forest steppe ecotone suggesting the highest effective moisture with the establishment of seasonality between 5 and 3 cal ka bp from 3 cal ka bp the record indicates a retraction of the forest steppe ecotone accompanied by a high pollen record variability and an increased fire activity these late changes suggest decreased effective moisture associated with a high climatic variability at regional and extra regional scale climatic changes at lake shaman s record are mostly associated to changes latitudinal shifts and or strengthening weakening of past southern westerlies that were previously recorded along patagonia from the lateglacial to the mid holocene during the late holocene a regional pattern characterized by high record variability emerges throughout central chilean patagonia this variability would be related to 1 low magnitude southern westerlies changes probably associated to enso and or sam or 2 the complex relationships between vegetation fire and human occupations during the last 3 cal ka

geochemical investigations of saltwater intrusion into the coastal carbonate aquifer of mallorca spain abstract coastal aquifers often display seawater intrusion resulting in the formation of a salty water wedge progressing inland this study investigates the mass transfers in the mixing zone at the freshwater seawater interface where the water is out of equilibrium with the rock forming carbonates investigations were conducted in two boreholes separated by 5 m at the ses sitjoles test site mallorca island spain where repeated electrical conductivity logs of the formation and the saturating fluid as well as regular pore water sampling and permanent downhole multi parameter monitoring of the water were performed over a period of 9 a in the mixing zone the significant acidification the calcite saturation index profile and the ca concentration profile cannot be explained by conservative mixing nor by dissolution precipitation reactions only conversely the analysis of organic c content and of the distinctly different time resolved ph profiles measured in the two boreholes suggests the development of perennial biomass that triggers calcite dissolution moreover the presence of biomass seems to be correlated with the permeability and vertical connectivity at the meter scale it is speculated that the mechanism could be self activated because the microbiological activity induces calcite dissolution and tends to increase porosity and permeability that favors biomass development

lake and inland dunes as interconnected systems the story of lake tresssee and an adjacent dune field schleswig holstein north germany the specific aim of the study was to investigate how four adjacent geomorphological systems a lake a dune field a small alluvial fan and a slope system responded to the same impacts lake tre

environmental changes during the holocene climatic optimum in central europe human impact and natural causes abstract the priority programme changes of the geo biosphere aimed to reconstruct the environmental history of central europe with emphasis on the time interval from 9000 to 5500 cal bp time slice ii coinciding with the holocene climatic optimum during this period the onset of human activities such as settlement agriculture and animal husbandry caused environmental changes studies of different landscape units in germany were carried out to identify these anthropogenically induced changes and to distinguish them from natural effects on the environmental system the investigated archives included laminated lake sediments fluvial sediments colluvia and soils speleothems peat and coastal sediments the different archives were examined using refined research methods including a variety of sedimentary and geochemical analyses together with pollen analysis and dating methods for the establishment of a reliable chronology the results of the various research groups are summarised and critically discussed based on these results the climatic optimum can be subdivided into three periods 1 the early atlantic from 9000 to 7500 cal bp with negligible human impact and stable environmental conditions 2 the late atlantic during early and middle neolithic from 7500 to 6300 cal bp with pollen evidence for vegetation changes but only negligible changes detectable in other proxy records and 3 the late atlantic during the younger neolithic jungneolithikum after 6300 cal bp with human impact observed in many archives and proxy records especially in the pollen record but also in lacustrine and fluvial sediments during the whole climatic optimum natural causes such as minor shifts of temperature did not induce substantial environmental changes though some changes such as temporary droughts may have facilitated and amplified the observed human impact

climate and local controls of long term vegetation dynamics in northern patagonia lat 41 s abstract patagonian vegetation has dramatically changed in composition and distribution over the last 16 000 yr although patterns of vegetation change are relatively clear our understanding of the processes that produce them is limited high resolution pollen and charcoal records from two lakes located at lat 41 s provide new information on the postglacial history of vegetation and fire activity at the forest steppe ecotone and help clarify the relative importance of local and regional drivers of late holocene ecological change our results suggest that late glacial parkland was colonized by shrubs at ca 11 200 cal yr bp and this vegetation persisted until 4900 cal yr bp when increased humidity allowed for the establishment of nothofagus forest the late holocene is characterized by oscillations in forest dominance largely driven by changes in humidity possibly associated with the onset or strengthening of enso in the last 4900 yr humid periods 4900 3800 and 2850 1350 cal yr bp have promoted nothofagus forest whereas drier times 3800 2850 and 1350 450 cal yr bp have favored austrocedrus expansion at intermediate moisture levels however the lower forest supported both taxa and fire became an important control of community composition with severe infrequent fires facilitating nothofagus regeneration and high fire frequency and intensity supporting austrocedrus

abrupt vegetation changes during the last glacial to holocene transition in mid latitude south america a pollen record from the huelmo site ca 41 30 s shows that vegetation and climate changed at millennial time scales during the last glacial to holocene transition in the mid latitude region of western south america the record shows that a nothofagus parkland dominated the landscape between 16 400 and 14 600 14c yr bp along with magellanic moorland and cupressaceous conifers evergreen north patagonian rainforest taxa expanded in pulses at 14 200 and 13 000 14c yr bp following a prominent rise in nothofagus at 14 600 14c yr bp highly diverse closed canopy rainforests dominated the lowlands between 13 000 and 12 500 14c yr bp followed by the expansion of cold resistant podocarps and nothofagus at ca 12 500 and 11 500 14c yr bp local disturbance by fire favoured the expansion of shade intolerant opportunistic taxa between 10 900 and 10 200 14c yr bp subsequent warming pulses at 10 200 and 9100 14c yr bp led to the expansion of thermophilous summer drought resistant valdivian rainforest trees until 6900 14c yr bp our results suggest that cold and hyperhumid conditions characterised the final phase of the last glacial maximum lgm between 16 400 and 14 600 14c yr bp the last ice age termination commenced with a prominent warming event that led to a rapid expansion of north patagonian trees and the abrupt withdrawal of andean ice lobes from their lgm positon at ca 147 000 14c yr bp hyperhumid conditions prevailed between 16 400 and 13 000 14c yr bp what we term the extreme glacial mode of westerly activity this condition was brought about by a northward shift and or intensification of the southern westerlies the warmest driest conditions of the last glacial interglacial transition occurred between 9100 and 6900 14c yr bp during this period the westerlies shifted to an extreme interglacial mode of activity via a poleward migration of stormtracks our results indicate that a highly variable climatic interval lasting 5500 14c years separate the opposite extremes of vegetation and climate during the last glacial interglacial cycle i e the end of the lgm and the onset of the early holocene warm and dry period copyright 2003 john wiley sons ltd

evolution of isolated caves in porous limestone by mixing of phreatic water and surface water at the water table of unconfined aquifers a model approach summary when water from the surface e g from a lake flows through porous carbonate rocks down along some region with high hydraulic conductivity and encounters the water table of a phreatic aquifer both waters mix by diffusion along their boundary in a carbonate aquifer where both surface and phreatic waters are saturated with respect to calcite mixing corrosion causes renewed dissolution of the carbonate rock in the diffusional mixing zone extending from the boundary separating the phreatic water from the surface water encountering it a numerical model is presented from which the initial change of porosity in such a diffusional mixing zone is obtained the initial change of porosity d dt 0 is proportional to m x y 2 and d2 ceq m dm2 m x y is the spatial distribution of the mixing ratio m vsur vsur vphr and the vs assign the corresponding volumes of surface and phreatic water d2 ceq dm2 is the second derivative of ceq the renewed dissolution capacity of the mixed solution it has been calculated for three geochemical scenarios with differing co2 concentrations of surface and phreatic water by use of phreeqc 2 the spatial distribution m x y is obtained by using modflow and mt3dms in a modeling domain with constant hydraulic conductivity for various flow velocities of the phreatic aquifer from the results the time scale of cave evolution is estimated passages of dimensions of about one meter in width and several 10 cm in height extending in length along the border line where surface and phreatic water meet can be created in time scales of 10 000 years these caves are horizontal with blind ending passages and resemble closely to the isolated caves observed in central west florida for more realistic modeling we have used a geostatistical local distribution of hydraulic conductivities in the modeling domain for a correlation length of 1 of the length of modeling domain the spatial distribution extends deeper into the flow direction when the correlation length is increased by a factor of 10 flow focusing distorts the diffusional mixing zone and enhances the creation of porosity

late holocene inland dune activity in the uk a case study from breckland east anglia inland dune fields found in breckland east anglia uk have previously been correlated with the widespread late devensian coversands of the region and a seventeenth century sandflood which is known to have inundated the village of santon downham a programme of optically stimulated luminescence and radiocarbon dating undertaken on the dunes at wangford warren and santon downham reveals that episodic aeolian activity has taken place during the last 7000 years five sand depositional phases on breckland dunes are identified c 6500 c 1600 1100 c 500 c 400 335 and from c 200 30 years before present between c 2120 1840 years ago and within the period 1100 300 years ago quiescent periods allowed the development of fen peat and soils local controlling factors on aeolian activity in breckland appear to be related to anthropogenic activities and livestock sheep and rabbits reducing vegetation cover and decreased precipitation and sea levels which led to lowering of water tables breckland aeolian activity when compared to the national and sub continental holocene aeolian activity record shows a high level of concordance the underlying forcing factor for late holocene dune activity in the uk and elsewhere in europe appears to be climatic instability in the north atlantic associated with both the little ice age and previous similar events which led to increased storminess climatic variability and lower temperatures

millennial scale variability in southern hemisphere westerly wind activity over the last 5000 years in sw patagonia abstract here we report results from a high resolution palynological record and stratigraphic geochronologic data related to a neoglacial event in torres del paine national park southern chile 51 s 71 w to investigate climatic variations in southwest patagonia during the last 5000 years the record reveals a stepwise expansion of nothofagus dominated woodlands and forests with discrete pulses at 4400 2900 1300 and 570 cal yr bp superimposed upon this trend we identify a relative opening of the woodlands between 4100 2900 and 2300 1300 cal yr bp closed canopy forests dominated the landscape between 570 60 cal yr bp followed by a rapid decline at the end of the 19th century that coincided with intense fire activity and the appearance of rumex cf acetocella an exotic species introduced by european settlers we interpret these changes as variations in the intensity and or position of the southern margin of the westerly winds which culminated with a net eastward shift of the forest steppe ecotone during the little ice age we propose that millennial scale changes in either the latitudinal position and or the overall strength of the southern westerlies may be responsible for vegetation changes fire occurrence and the dynamic behavior of patagonian glaciers during the last 5000 years because the modern maximum in near surface wind velocities and precipitation is located between 48 and 50 s we suggest that the core of the southern westerlies may have achieved this modern position 570 years ago

reactive transport modeling of calcite dissolution in the fresh salt water mixing zone abstract dissolution of calcite in the saltwater mixing zone of coastal carbonate aquifers has been the subject of numerous studies they conclude that dissolution is driven by mixing of freshwater and saltwater which may lead to undersaturation even if both end members are saturated however as transport in the mixing zone is rather complex a fully coupled reactive transport model is needed to properly understand the interplay between transport and chemistry we perform 1 and 2d simulations to gain insight into the processes controlling dissolution rate exploring its sensitivity to the chemistry of end members and the dispersivity of the medium we conclude that the results of sanford and konikow sanford w e konikow l f 1989 simulation of calcite dissolution and porosity changes in saltwater mixing zones in coastal aquifers water resources research 25 655 667 which used a two step method solely transporting the amount of calcite dissolved are essentially correct but their solution is essentially kinetic with a rate dependent on the time increment used the 1d simulations allow us to show that maximum dissolution rates do occur neither at the location nor for the end members of maximum undersaturation for non reactive mixing in the 1d case enhanced transport at the freshwater end causes dissolution to concentrate there however in the 2d case representative of coastal aquifers maximum dissolution occurs at the saline side near the discharge zone because of a very active convection cell that develops there which enhances mixing and thus reaction rates this mechanism may explain observations at blue holes and should display a positive feedback with dissolution causing an increase in permeability that would lead to increased seawater flux and mixing thus enhancing further dissolution

surface modification on bone trampling versus butchery abstract previous researchers have reported difficulties in distinguishing between surface marks on bone formed by sedimentary abrasion and those inflicted while butchering trampling by large ungulates and humans has been credited with producing pseudocut marks natural alterations to the bone that mimic cultural ones the purposes of this research are 1 to re examine trampling as a taphonomic process and 2 to suggest criteria useful for distinguishing sedimentary abrasion including trampling from butchery macroscopic and microscopic comparison of experimentally trampled bones and those which have had soft tissue removed with a flint tool demonstrate significant differences between the surface modifications produced by the two processes

carbonate dissolution and precipitation in coastal environments laboratory analysis and theoretical consideration 1 we have conducted laboratory experiments to examine caco3 dissolution and precipitation in saltwater freshwater mixing zones with a view to understanding and predicting porosity changes in coastal environments mixing of seawater or saline subsurface water with fresh water can be of major importance in the chemical diagenesis of carbonate rocks and sediments we used artificial seawater and nacl solutions of different concentrations under different co2 partial pressures and with different mixing ratios two dimensional flow cells filled with glass beads and crushed calcium carbonate rock were used to measure calcium carbonate precipitation and dissolution respectively an important feature of these experiments is that the results are shown to agree well with a relatively simple transport theory describing mineral precipitation dissolution that results from the nonlinear dependence of caco3 saturation upon electrolyte concentration the theory demonstrates that the rate of dissolution or precipitation depends on the curvature and sign of the solubility as a function of salinity the square of the salinity gradient and the macroscopic dispersion coefficient the theory is largely scale independent and depends upon field parameters that can be determined analysis of data from three field sites yucatan peninsula bermuda and mallorca demonstrates excellent agreement between field observations and theory

heterogeneous distributions of co 2 may be more important for dissolution and karstification in coastal eogenetic limestone than mixing dissolution mixing dissolution a process whereby mixtures of two waters with different chemical compositions drive undersaturation with respect to carbonate minerals is commonly considered to form cavernous macroporosity e g flank margin caves and banana holes in eogenetic karst aquifers on small islands macroporosity commonly originates when focused dissolution forms globular chambers lacking entrances to the surface suggesting that dissolution processes are decoupled from surface hydrology mixing dissolution has been thought to be the primary dissolution process because meteoric water would equilibrate rapidly with calcium carbonate as it infiltrates through matrix porosity and because pco2 was assumed to be homogeneously distributed within the phreatic zone here we report data from two abandoned well fields in an eogenetic karst aquifer on san salvador island bahamas that demonstrate pco2 in the phreatic zone is distributed heterogeneously the pco2 varied from less than log 2 0 to more than log 1 0 atm over distances of less than 30 m generating dissolution in the subsurface where water flows from regions of low to high pco2 and cementation where water flows from regions of high to low pco2 using simple geochemical models we show dissolution caused by heterogeneously distributed pco2 can dissolve 2 5 to 10 times more calcite than the maximum amount possible by mixing of freshwater and seawater dissolution resulting from spatial variability in pco2 forms isolated globular chambers lacking initial entrances to the surface a morphology that is characteristic of flank margin caves and banana holes both of which have entrances that form by erosion or collapse after cave formation our results indicate that heterogeneous pco2 rather than mixing dissolution may be the dominant mechanism for observed spatial distribution of dissolution cementation and macroporosity generation in eogenetic karst aquifers and for landscape development in these settings copyright 2015 john wiley sons ltd

the existence of open areas during the mesolithic evidence from aeolian sediments in the elbe jeetzel area northern germany abstract traditionally mesolithic hunter gatherer cultures are supposed to have lived in a primeval forest environment with a closed vegetation cover during the early and mid holocene it is not until the onset of subsequent neolithic agricultural societies that the development of more expansive open areas is assumed therefore our perception of the mesolithic economy in the european lowlands is highly affected by the idaea of adaptation to dense forest environments and a very stable system of resource exploitation however recent palaeoenvironmental studies provide evidence that areas of open landscapes must have existed at least temporarily during the mesolithic and evoke the question whether human impact may be accountable for this re activation of late glacial inland dunes may serve as an indicator for vegetation clearances using both optically stimulated luminescence osl and 14 c dates from five inland dune sites with traces of mesolithic activity in the elbe jeetzel area n germany we prove that asynchronous events of aeolian sedimentation persisted during the mesolithic especially during the older mesolithic around 9000 a and the late mesolithic from 7000 a and 6000 a there is no evidence that holocene climatic deteriorations like the 8 2 ka event had an effect on the intensity of aeolian sedimentation we conclude that either natural factors or mesolithic human impact or most likely a combination of both must have been a major driving force for the creation of open areas and thus ongoing aeolian activity while supra regional climatic causes seem less probable a prominent younger phase of human induced aeolian activity was identified during the late neolithic

pleistocene glaciation in the southern lake district of chile relative age criteria permit deposits of successive andean glacier advances in the southern lake district of chile to be divided into four mappable drift sheets the oldest two of which overlie tertiary bedrock along the eastern flank of the cordillera de la costa only the youngest drift llanquihue is datable by radiocarbon during the most extensive ice advance of the last glaciation the lago llanquihue glacier was about 95 km long and reached an estimated maximum thickness of between 1000 and 1300 m glacier equilibrium lines at that time lay about 1000 m below their present level and rose eastward with a gradient of about 5 m km successive ice advances in the lago llanquihue basin which resulted in construction of end moraines and associated outwash plains beyond the lake margin culminated sometime before about 20 000 yr ago and between 20 000 and 19 000 yr ago a later readvance inferred from the sedimentary record of lake level fluctuations in the basin had begun by about 15 000 yr ago and culminated shortly after 13 000 yr ago a comparable but less closely dated record of ice advances is found northwest of seno reloncavi and on isla chiloe deglaciation following the latest advance is likely to have been rapid for the major glacier lobes fronted on deep water bodies that would have promoted extensive calving

late quaternary vegetation of southern isla grande de chiloe chile late glacial holocene forest history of southern isla chiloe latitude 43 10 s was reconstructed on the basis of pollen analysis in three profiles laguna soledad laguna chaiguata puerto carmen prior to 12 500 yr b p pollen records are dominated by plant taxa characteristic of open habitats zone i from 12 500 yr b p to the present tree species predominate in the pollen records zones ii v between 12 500 and 9500 yr b p ombrophyllous taxa nothofagus podocarpus nubigena myrtaceae fitzroya pilgerodendron and drimys are frequent in all pollen diagrams suggesting a wetter and colder climate than the present between 9000 and 5500 yr b p valdivian forest elements such as nothofagus dombeyi type weinmannia and eucryphia caldcluvia dominate indicating a period of drier and warmer climate from 5500 yr b p onward the expansion of mixed north patagonian subantarctic forest elements and the increased frequence of tepualia suggest increased rainfall and temperatures oscillating around the modern values the change from open to forest vegetation ca 12 500 yr b p probably represents the most pronounced climatic change in the record and can be interpreted as the glacial postglacial transition in the study area

climatic controls of holocene fire patterns in southern south america holocene fire climate vegetation linkages are mostly understood at individual sites by comparing charcoal and pollen records with other paleoenvironmental proxy and model simulations this scale of reconstruction often obscures detection of large scale patterns in past fire activity that are related to changes in regional climate and vegetation a network of 31 charcoal records from southern south america was examined to assess fire history along a transect from subtropic to subantarctic biomes the charcoal data indicate that fire activity was greater than present at ca 12 000 cal yr bp and increased further and was widespread at 9500 cal yr bp fire activity decreased and became more spatially variable by 6000 cal yr bp and this trend continued to present atmospheric circulation anomalies during recent high fire years show a southward shift in westerlies and paleoclimate model simulations and data syntheses suggest that such conditions may have prevailed for millennia in the early holocene when the pole to equator temperature gradients were weaker and annual temperatures were higher than present in response to orbital time scale insolation changes

the late glacial pedogenesis interrupted by aeolian activity in central poland records from the lake gościąz catchment abstract an interdisciplinary study was undertaken to reconstruct the late glacial fluvioglacial and aeolian sediment transformations with a particular focus on soil forming processes the studies included complex pedological research physical and chemical properties x ray diffraction xrd analysis of clay minerals and optically stimulated luminescence osl dating on soil deposit sequences developed within the aeolian landscape of inland dunes in the lake go ci z catchment central poland late glacial buried bwb soil horizons are known as finow soils this paleosol was identified in the central part of inland dunes in vertical perspective developed from aeolian material deposited on fluvioglacial sediments the average content of silt and clay in this paleosols ranged from 7 3 to 41 1 and from 6 7 to 12 6 respectively in other soil horizons within profiles the average content of these granulometric fractions was about 3 and 1 5 respectively the dominance of dioctahedral vermiculite and the higher content of free iron oxides especially oxalate form and aluminium within bwb horizons indicates their pedogenic origin the osl dates suggested that finow soil fossilization began along with the development of aeolian processes in the late glacial cold periods the older dryas and the younger dryas while finow soil development took place in the warmer periods of the late glacial bolling allerod these results were consistent with data from germany other stands in northern poland and the tomsk priobye region se western siberia

climatic inferences from glacial and palaeoecological evidence at the last glacial termination southern south america there is uncertainty about the interhemispheric timing of climatic changes during the last glacial interglacial transition different hypotheses relying on different lines of evidence point variously to the northern hemisphere leading the southern hemisphere and vice versa or to synchrony between the hemispheres southern south america is well placed to test the various alternatives using both glacial and palaeoecological evidence we argue here from a synthesis of key proxy records that there was a sudden rise in temperature that initiated deglaciation sychronously over 16 of latitude at 14 600 14 300 14 c yr bp 17 500 17 150 cal yr there was a second step of warming in the chilean lake district at 13 000 12 700 14 cy r bp 15 650 15 350 cal yr which saw temperatures rise to close to modern values a third warming step particularly clear in the south occurred at ca 10 000 14 c yr bp 11 400 cal yr the latter achieving holocene levels of warmth following the initial warming there was a lagged response in precipitation as the westerlies after a delay of ca 1600 yr migrated from their northern glacial location to their present latitude which was attained by 12 300 14 cy r bp 14 300 cal yr the latitudinal contrasts in the timing of maximum precipitation are reflected in regional contrasts in vegetation change and in glacier behaviour the large scale of a 80 km glacier advance in the strait of magellan at 12 700 10 300 14 c yr bp 15 350 12 250 cal yr which spans the antarctic cold reversal and the younger dryas was influenced by the return of the westerlies to southern latitudes the delay in the migration of the westerlies coincides with the heinrich 1 iceberg event in the north atlantic the suppressed global thermohaline circulation at the time may have affected sea surface temperatures in the south pacific and the return of the westerlies to their present southerly latitude only followed ocean reorganisation to its present interglacial mode copyright 2000 john wiley sons ltd

modelling karst aquifer evolution in fractured porous rocks abstract the removal of material in soluble rocks by physical and chemical dissolution is an important process enhancing the secondary porosity of soluble rocks depending on the history of the soluble rock dissolution can occur either along fractures and bedding partings of the rock in the case of a telogenetic origin or within the interconnected pore space in the case of eogenetic origin in soluble rocks characterised by both fractures and pore space dissolution in both flow compartments is possible we investigate the dissolution of calcite both along fractures and within the pore space of a limestone rock by numerical modelling the limestone rock is treated as fractured porous aquifer in which the hydraulic conductivity increases with time both for the fractures and the pore spaces we show that enlargement of pore space by dissolution will accelerate the development of a classical fracture dominated telogenetic karst aquifer breakthrough occurs faster in the case of a pore controlled aquifer as in eogenetic rocks enlargement of pores results in a front of enlarged pore spaces migrating into the karst aquifer with more homogeneous enlargement around this dissolution front and later breakthrough

aeolian sands and buried soils in the mecklenburg lake district ne germany holocene land use history and pedo geomorphic response abstract the present study is a pedo geomorphic approach to reconstructing holocene aeolian sand dynamics in the mecklenburg lake district ne germany stratigraphical sedimentological and soil research supplemented by morphogenetic interpretations of the genesis of dunes and aeolian sands are discussed a complex late holocene aeolian stratigraphy within a drift sand area was developed at the shore of lake muritz the results were confirmed using palynological records archaeological data and regional history accelerated aeolian activity was triggered by the intensification of settlement and land use activities during the 13th and in the 15th to 16th century ad after a period of stability beginning with population decline during the thirty years war and continuing through the 18th century a final aeolian phase due to the establishment of glassworks was identified during the 19th century ad we assume a direct link between holocene aeolian dynamics and human activities prehistoric holocene drift sands on terrestrial sites have not been documented in the mecklenburg lake district so far this might be explained either by erosion and incorporation of older aeolian sediments during younger aeolian phases and or a lower regional land use intensity in older periods of the holocene the investigated drift sands are stratigraphically and sedimentologically characterised by a high degree of heterogeneity reflecting the spatial and temporal variability of holocene human impact

formation of aeolian dunes on anholt denmark since ad 1560 a record of deforestation and increased storminess abstract sand dunes on the island of anholt denmark in the middle of kattegat form a relatively barren temperate climate aeolian system locally termed the desert the dunes have developed on top of a raised beach ridge system under the influence of dominant winds from westerly directions they are relatively coarse grained with an average mean grain size of 480 m the last phase of aeolian activity and dune formation on anholt started after ad 1560 when the local pine forest was removed historical sources report intense sand mobilization in the 17th century and new optically stimulated luminescence osl dates indicate that dune formation continued until the end of the 19th century this period of sand drift and dune formation took place during the later part of the little ice age which is characterized by increased summer storminess in large parts of nw europe dune stabilization in the beginning of the 20th century probably records a temporary decrease in storminess ground penetrating radar mapping of the internal structures in two dunes in the western part of the desert a parabolic dune and a linear dune indicates the importance of north westerly storm winds during dune formation

reactive henry problem effect of calcite dissolution on seawater intrusion freshwater stored in a coastal aquifer is extensively extracted through pumping wells due to high water demand in coastal area touristic industrial and public use to enhance freshwater security and to avoid contamination of water reserves seawater intrusion becomes a topic of great interest for hydrogeologists during the last few decades hydrogeologists have provided a deeper understanding of the prediction processes investigative tools and management of such systems the majority of the studies quantifies these hydrogeological systems using traditional density dependent flow and transport models and does not consider the effect of the chemical reactions interdependence of density dependent flow and chemical reactions and their effects on the porosity and permeability is the most important key toward a reliable modeling of these complex systems seawater intrusion can increase by the solid matrix dissolution processes in the saltwater freshwater mixing zone in the case of a coastal carbonate aquifer the dissolution of such rocks can easily induce a development of porosity and permeability as a result of the mixing processes the increase of permeability would enhance further seawater flux to the freshwater side in this work a relatively complete modeling scheme is presented to quantify and predict this risk the modeling of such a problem requires a set of highly nonlinearly coupled equations in this regard geodens code used in this work can solve these equations by a finite element procedure it can handle density dependent flow transport and geochemical reactions in porous media its main purpose is to represent the physicochemical processes in the subsurface system the code is used to simulate the effect of calcite dissolution during seawater intrusion in a coastal carbonate homogeneous aquifer

changing fire regimes in the temperate rainforest region of southern chile over the last 16 000 yr abstract a high resolution macroscopic charcoal record from lago melli 42 46 s 73 33 w documents the occurrence of forest fires in the lowlands of isla grande de chiloe southern chile over the last 16 000 yr our data suggest that fire activity in this region was largely modulated by the position intensity of the southern westerlies at multi millennial time scales fire activity was infrequent or absent between 16 000 11 000 and 8500 7000 cal yr bp and was maximal between 11 000 8500 and 3000 0 cal yr bp a mosaic of valdivian north patagonian rainforest species started at 6000 cal yr bp along with a moderate increase in fire activity which intensified subsequently at 3000 cal yr bp the modern transition between these forest communities and the occurrence of fires are largely controlled by summer moisture stress and variability suggesting the onset of high frequency variability in summer precipitation regimes starting at 5500 cal yr bp because negative anomalies in summer precipitation in this region are teleconnected with modern el nino events we propose that the onset of el nino like variability at 5700 6200 cal yr bp led to a reshuffling of rainforest communities in the lowlands of isla grande de chiloe and an increase in fire activity

age and sedimentary record of inland eolian sediments in lithuania ne european sand belt we present a study based on four inland eolian locations in eastern central and southeastern lithuania belonging to the northeastern part of the european sand belt esb although there have been several previous studies of the esb this north eastern extension has not been investigated before in any detail the sedimentary structural textural features are investigated and a chronology was derived using optically stimulated luminescence on both quartz and feldspar the sedimentary structures and the rounding and surface characteristics of the quartz grains argue for a predominance of eolian transport additionally some structural alternations and a significant contribution of non eolian grains are interpreted as inherited local glacial glaciofluvial bearing lithologies three main glaciolacustrine eolian phases are distinguished based on the position in the landscape and the luminescence ages 1 an older eolian series around 15 to 16 ka possibly correlated with the cold gs 2a event according to the grip stratigraphy and 2 a younger eolian series around 14 0 ka possibly representing the gi id and 1c events the older eolian series is underlain by 3 a glaciolacustrine eolian series for which the period of deposition remains uncertain due to the significant discrepancy between the ages based on quartz and feldspar c 2015 university of washington published by elsevier inc all rights reserved less

paleoenvironment and stratigraphy during the last glacial in the belgian dutch border region the weichselian deposits of the flat dutch belgian coversand area are characterized by highly varying facies types the geomorphological location and the role of water during the deposition and the transportation of the original eolian sediments may fully explain the texture and sedimentary structures of the lithostratigraphic units directly deposited eolian loams and sands on the dry interfluves contrast with the same but reworked sediments in wet valleys and depressions the formation of periglacial phenomena is also dependent on the geomorphologic lithologic and hydrologic conditions the occurrence of peaty beds is restricted to wet environments without precise climatic significance the pleniglacial sequence is subdivided into early and late pleniglacial stades both characterized by partial permafrost conditions interrupted by a middle pleniglacial interstadial complex with clearly milder conditions

osl dating of coarse grain fluvial quartz using single aliquot protocols on sediments from ne peloponnese greece abstract optical ages of quartz extracts in holocene sediments from the north eastern peloponnese greece are reported the single aliquot regenerative dose protocol proposed by murray and wintle 2000 radiation measurements 32 57 73 was used to estimate the equivalent dose in these samples a large inter aliquot scatter in d e values was observed for all samples this is ascribed to heterogeneous bleaching of the samples at deposition to estimate a d e for age calculation a technique is suggested based on the analysis of the d e scatter obtained from nine different quartz samples which were artificially bleached and irradiated this procedure is especially useful when the sample quantity is limited the optical age estimates increase with sampling depth an average aggradation rate of 1 5 mm yr is derived using the osl ages this value is consistent with the known uplift rate of 1 2 mm yr

macro and micro scale study and chronology of late weichselian aeolian sediments in estonia north eastern european sand belt patchy aeolian landforms representing the ne part of the european sand belt occur in ne estonia between the gulf of finland and lake peipsi the dunes are restricted to the former glacial lakebed thus lying directly in contact with glaciolacustrine sediments and have so far prompted different opinions regarding their genesis and age this study aims to answer these open questions regarding the age and origin of these landforms and to provide information on the associated past sedimentary processes to achieve this we combine macro scale sedimentary structures and ground penetrating radar survey and micro scale grain size shape and character of quartz grain surfaces and mineral composition studies with optically stimulated luminescence dating the glaciolacustrine fines in the study area are wavy stratified with the occurrence of mica horizons and prevalence of quartz sand grains with aeolian characteristics therefore these sediments argue for near standing low energy water conditions in the glacial lake where allochthonous material was delivered by wind a fall in the lake level and the occurrence of dry land on the northern coast of the regressive late weichselian lake peipsi favoured aeolian activity from ca 13 5 to 10 5 ka in the region the aeolian accumulation was brief as apparent from the results of the micro scale study and lacks evidence of sediment recycling only easily removable mica was deflated at the end of the aeolian depositional phase aeolian activity terminated ca 10 5 ka due to a rising groundwater level that is apparent from the onset of paludification in the region

the last glacial holocene transition in southern chile warming at the last glacial termination in the north atlantic region was interrupted by a period of renewed glacial activity during the younger dryas chronozone ydc the underlying mechanism of this cooling remains elusive but hypotheses turn on whether it was a global or a north atlantic phenomenon chronological sedimentological and palaeoecological records from sediments of small lakes in oceanic southern chile demonstrate that there was no ydc cooling in southern chile it is therefore likely that there was little or no cooling in southern pacific surface waters and hence that ydc cooling in the north atlantic was a regional rather than global phenomenon

hydrogeochemistry of grand cayman british west indies implications for carbonate diagenetic studies abstract groundwater in the dolostone aquifers of the bluff group oligocene miocene on grand cayman is divided into fresh lightly and highly brackish and saline type i and ii zones according to chemical characteristics that were determined during a 3 year 1985 1988 monitoring program brackish and type i saline waters display the greatest variation in chemical properties whereas the type ii saline water has the most stable chemical characteristics most groundwaters from these dolostone aquifers are thermodynamically capable of precipitating calcite and or dolomite the saturation indices for these minerals however vary through time and space even in the context of small water lens simple mixing of fresh and sea water cannot explain the chemistry of the water found in the joint and karst controlled dolostone aquifers of grand cayman deviation from a simple mixing model is due to variations caused by tidal fluctuation the rate of rain water recharge influx of ca rich groundwater from the surrounding limestone aquifers influx of co 2 rich surface water from sinkholes and swamps and water rock interactions dissolution and precipitation of calcite and dolomite sustained groundwater abstraction from a lens can significantly alter the hydrochemistry of the water lens this suggests that hydrochemical characterization of small fresh water lenses like those on grand cayman cannot be based on spot or short term sampling interpretation of such fluids in terms of calcite dolomite precipitation and or dissolution must be treated with caution if the data base has not been derived from long term monitoring

deglacial and postglacial climate history in east central isla grande de chiloe southern chile 43 s abstract palynologic and stratigraphic data from laguna tahui 42 50 s 73 30 w indicate cool temperate and humid conditions there between 14 000 and 10 000 14c yr b p followed by warmer and drier than present conditions between 10 000 and 7000 14c yr b p and subsequent cooling and rise in precipitation over the last 5800 14c yr the thermophilous valdivian trees eucryphia cordifolia and caldcluvia paniculata reached their maximum abundance during the early holocene warm dry phase 10 000 7000 14c yr b p followed by a rise in lake levels and reexpansion of north patagonian conifers starting at 7000 and 5800 14c yr b p respectively variations in the stratigraphic and geographic distribution of temperate rainforests in southern chile suggest multimillennial trends in temperature and westerly activity which are spatially and temporally coherent with paleoclimate records from neighboring regions climate variability at millennial and submillennial time scales may account for the establishment and persistence of fine scale mosaics of valdivian and north patagonian rainforest species in low to mid elevation communities since 5800 14c yr b p

lake belau and its catchment northern germany a key archive of environmental history in northern central europe since the onset of agriculture the environmental history since the onset of agriculture was reconstructed from sediments and soils in the catchment area of lake belau schleswig holstein northern germany the established chron

historical soil erosion by water in germany scales and archives chronology research perspectives abstract the published record of historical soil erosion by water in germany as deduced from dated slope deposits n 306 alluvial sediments n 120 and lake sediments is summarized in this paper the number of sediments investigated reflects the state of knowledge chronology of historical soil erosion and to a certain degree the intensity of the human impact on german landscapes during the holocene even though few data of calculated historical soil erosion intensities exist an estimation of historical soil erosion in germany combining the available data has been calculated soil erosion in germany occurred first locally during the early holocene probably triggered by climatic variability from the neolithic onward the record reflects the human impact according to agricultural land use the observed variability indicates phases of weaker and regained intensity of agricultural land use in germany few records characterise the early and middle bronze age ca 2000 1600 bc and the migration period and the early medieval times ca 400 1000 ad surprisingly for the roman emperor times ca 1 400 ad a decreasing number of soil sediments is recorded even when the data from southern germany is examined separately phases characterised by an increase in soil erosion were the late bronze age and pre roman iron age ca 1600 bc 1 ad the high and late medieval times ca 1000 1350 ad and the modern times ca 1500 ad until today some extraordinary heavy precipitation events late 18th early 19th first half of 14th century pre roman iron age topped the even high soil erosion intensities research gaps as well as potential for future research as derived from the available data are outlined

fire and vegetation history from the coastal rain forest of the western oregon coast range high resolution charcoal and pollen analyses were used to reconstruct a 4600 yr long history of fire and vegetation near taylor lake in the wettest forests of coastal oregon today fires in these forests are rare because the season of ignition does not coincide with months of dry fuels from ca 4600 to 2700 cal yr b p fire episodes occurred at intervals of 140 30 yr while forest vegetation was dominated by disturbance adapted taxa such as alnus rubra from ca 2700 cal yr b p to the present fire episodes have become less common occurring at intervals of 240 30 yr and firesensitive forest taxa such as tsuga heterophylla and picea sitchensis have become more prominent fire occurrence during the midholocene was similar to that of the more xeric forests in the eastern coast range and suggests that summer drought was widespread after ca 2700 cal yr b p a decrease in fire episode frequency suggests that cooler conditions and possibly increased summer fog allowed the establishment of present day picea sitchensis forests within the watershed these results provide evidence that fire has been an important disturbance agent in the coast range of oregon and variations in fire frequency and climate have led to the establishment of present day forests c 2002 university of washington

17 000 years of vegetation fire and climate change in the eastern foothills of the andes lat 44 s abstract paleoenvironmental records from patagonia reveal the importance of latitude longitude and elevation in shaping the response of vegetation to climate change we examined the vegetation fire and watershed history from two sites at lat 44 s as inferred from pollen charcoal and lithologic data these reconstructions were compared with independent paleoenvironmental records to better understand ecosystem dynamics along the southeastern andes lat 41 50 s our results show that at lat 44 s late glacial heath steppe was colonized by trees at 14 200 cal yr bp and forests became more closed at 11 500 cal yr bp differences in forest cover between the two sites were likely due to elevation dependent disparities in humidity and fire north of lat 44 s increasing precipitation favored initial forest development at 16 500 cal yr bp while dry conditions restricted tree expansion in the south until 7000 cal yr bp the time transgressive pattern is attributed to a gradual southward shift in the southern westerlies resulting from deglaciation and increasing annual insoltion present day vegetation developed at all latitudes during the middle to late holocene when the core of the southern westerlies reached its modern position 50 s asynchronous forest expansions north and south of lat 45 s between 5000 and 3000 cal yr bp are ascribed to centennial cycles of contraction and expansion of the southern westerlies which led to seasonal variations in precipitation at the core and northern border of the wind belt synchronous oscillations in tree abundance along the eastern andes prevailed during the last 3000 years decreased forest cover at all latitudes between 2500 and 1500 cal yr bp is concurrent with la nina like conditions and high solar irradiance these climate drivers likely decreased effective moisture and favored fires at all latitudes

late quaternary 15 ka to present development of a sandy landscape in the mol area campine region north east belgium the geomorphological analysis of two sections cut into a sandy landscape in north east belgium enabled the establishment of a chronology for a sequence of events during the last 15 ka that illustrate the polycyclical nature of the evolution of such landscapes field descriptions analytical sediment and soil characterization and pollen analysis are combined with the optically stimulated luminescence dating method to unravel the recent geomorphological history of the investigated site the principal results include apparently discontinuous sand deposition between 15 and 12 ka landscape stabilization and podzol formation between 12 and 1 ka the development of a drift sand landscape between 650 and 200 a and renewed stabilization over the last two centuries the results are discussed in the light of climate land use and vegetation changes and compared with findings at similar sites in the european sand belt

stratigraphy and age of colluvial deposits indicating late holocene soil erosion in northeastern germany abstract in the focus of this study are the sedimentary characteristics chronology magnitude and causes of past soil erosion dynamics of an agriculturally intensively used glacial lowland landscape from the mesoscale quillow river catchment sedimentary sections bearing colluvial sediments from different landforms were analysed to explore their geoarchive potential and to establish a local chronology of late holocene soil erosion sections from footslopes contain a rather simple stratigraphy with one topping colluvial horizon of up to 1 m thickness burying a palaeosol in contrast glacial kettle holes preserve more complex sequences partly having several colluvial layers with intercalating palaeosols the most complex stratigraphy is associated with a kettle hole being the ultimate sediment trap for a dendritic gully system forming a 4 m thick sequence of alternating peat and colluvial layers thirty osl ages and 13 radiocarbon ages are used to reconstruct phases of soil erosion potentially human induced soil erosion which is corroborated by local archaeological and palynological data can be traced back to the last c 4000 years the oldest colluvial deposits date back to the late bronze age most datings however cluster within the last 600 years with a peak in the last 200 years ascribing the main phase of local soil erosion to the recent past thus although numerous archaeological finds are detected in the catchment since the neolithic considerable agricultural soil erosion does not occur before the last millennium a compilation of osl chronologies based on colluvial sediments from other regions in central europe shows a more complex erosion history there with a pronounced two or three phased distribution of ages primarily dating into the last c 4000 5000 years this study underlines that in northeastern central europe human impact on landscapes was effective apparently at a later stage as compared to some adjacent regions

the human impact in geomorphology 50 years of change abstract concern with the human impact in geomorphology has a long history what is new is that since 1969 a number of developments have taken place that have led to an increasing realisation of its importance these developments are in four main areas i intellectual and policy related ii technological developments that alter geomorphological processes iii demographic trends and iv the proliferation of techniques for the study of landform and process change there has been a realisation of the role of humans in landscape transformation in ancient times the human impact has developed through time but particularly notable are the potential early effects of fire extinctions and deforestation on geomorphological processes the spread of european agriculture particularly in the nineteenth century transformed erosion and sedimentation rates in many parts of the world notwithstanding the importance of some of these changes in prehistoric and historic times recent researches have demonstrated that humans have become an increasingly important agent of geomorphological change during the period of the great acceleration of the past five or six decades the interest in global warming that has developed since the early 1980s has created considerable interest in its consequences for a range of geomorphological phenomena it is also becoming apparent that anthropogenic geomorphological change is having an impact on the earth system as a whole finally geomorphologists have taken an increasing interest in how they can make an impact in the field of landscape conservation

postglacial vegetation climate and fire history along the east side of the andes lat 41 42 5 s argentina abstract the history of the low elevation forest and forest steppe ecotone on the east side of the andes is revealed in pollen and charcoal records obtained from mid latitude lakes prior to 15 000 cal yr bp the vegetation was characterized by steppe vegetation with isolated stands of nothofagus the climate was generally dry and the sparse vegetation apparently lacked sufficient fuels to burn extensively after 15 000 cal yr bp a mixture of nothofagus forest and shrubland steppe developed fire activity increased between 13 250 and 11 400 cal yr bp contemporaneous with a regionally defined cold dry period huelmo mascardi cold reversal the early holocene period was characterized by an open nothofagus forest shrubland mosaic and fire frequency was high in dry sites and low in wet sites the data suggest a sharp decrease in moisture eastward from the andes a shift to a surface fire regime occurred at 7500 cal yr bp at the wet site and at 4400 cal yr bp at the dry site preceding the expansion of austrocedrus by 1000 1500 yr the spread of austrocedrus is explained by a shift towards a cooler and wetter climate in the middle and late holocene the change to a surface fire regime is consistent with increased interannual climate variability and the onset or strengthening of enso the present day mixed forest dominated by nothofagus and austrocedrus was established in the last few millennia

late weichselian fluvio aeolian sands and coversands of the type locality grubbenvorst southern netherlands sedimentary environments climate record and age the weichselian late pleniglacial and lateglacial aeolian stratigraphy older coversand i beuningen gravel bed older coversand ii younger coversand i usselo soil younger coversand ii in the southern netherlands has been reinvestigated in its type locality grubbenvorst sedimentary environments have been reconstructed and related to their climatic evolution based on periglacial structures in addition 22 optically stimulated luminescence osl ages have been determined that provide an absolute chronology for the climatic evolution and environmental changes of the coversand area from this work it appears that prior to 25 ka fluvial deposition by the maas dominated after 25 ka fluvial activity reduced and deposition occurred in a fluvio aeolian environment with continuous permafrost older coversand i this depositional phase was dated between 25 2 2 0 and 17 2 1 2 ka the upward increase of aeolian activity and cryogenic structures in this unit is related to an increase of climatic aridity and a decrease in sedimentation rate during the last glacial maximum lgm the beuningen gravel bed that results from deflation with polar desert conditions and that represents a stratigraphic marker in northwestern europe was bracketed between 17 2 1 2 and 15 3 1 0 ka based on this age result a correlation with heinrich event h1 is suggested permafrost degradation occurred at the end of this period optical ages for the older coversand ii unit directly overlying the beuningen gravel bed range from 15 3 1 0 ka at the base to 12 7 0 9 ka at the top thus this regionally important older coversand ii unit started at the end of the late pleniglacial and continued throughout the early lateglacial its formation after the late pleniglacial lp maximum cold and its preservation are related to rapid climatic warming around 14 7 ka cal bp the allerod age of the usselo soil was confirmed by the optical ages copyright 2007 john wiley sons ltd

climate fire and vegetation between about 13 000 and 9200 14c yr b p in the chilean lake district abstract a pollen record from lago condorito 41 45 s 73 07 w shows that north patagonian rain forest taxa predominated between about 13 000 and 12 200 14c yr b p in the lowlands of southern chile near the city of puerto montt this was followed by the expansion and persistence of the conifer podocarpus nubigena between 12 200 and 9900 14c yr b p trees favored by disturbance expanded between 11 200 and 9900 14c yr b p concurrent with sharp and sustained increases of microscopic charcoal particles taxa of low elevation rain forests expanded and became more diverse in pulses centered at 9900 and 9000 14c yr b p following the disappearance of p nubigena these data suggest conditions approaching modern climate between about 13 000 and 12 200 14c yr b p the climate cooled between 12 200 and 9900 14c yr b p then quickly warmed to interglacial conditions stand replacing fires occurred near lago condorito between 11 200 and 9900 14c yr b p under cool temperate humid conditions the proximity and reported antiquity of the monte verde archeological site raise the possibility that these fires were set by human activities

evolution of porosity in the saltwater freshwater mixing zone of coastal carbonate aquifers an alternative modelling approach summary dissolution of calcium carbonate in the saltwater freshwater mixing zone in carbonate islands and coastal aquifers up to now has been treated by coupling geochemical equilibrium programmes to a reactive transport model the result is a complex nonlinearly coupled set of differential transport advection equations which need high computational efforts if dissolution rates of calcite are sufficiently fast such that one can assume the solution to be in equilibrium with respect to calcite a highly simplified modelling approach can be used by use of the concept of phillips in his book flow and reactions in permeable rock cambridge university press new york 1991 and its more general formulation by de simoni et al de simoni m carrera j sanchez vila x guadagnini a 2005 a procedure for the solution of multicomponent reactive transport problems water resource research 41 w11410 it is possible to decouple the complex set of equations to calculate initial changes of porosity in the rock matrix one needs solely to solve the advection transport equation for salinity s current codes on density driven flow such as seawat can be used to obtain the dissolution capacity of the mixed saltwater freshwater solution the calcium equilibrium concentration c eq s is obtained as a function of salinity by phreeqc 2 initial porosity changes can then be calculated by a simple analytical expression of the gradient of the spatial distribution s x y of salinity the distribution of flow fluxes q x y and the second derivative of the calcium equilibrium concentration c eq s with respect to salinity s this approach does no longer require large dispersivities on the order of meters but reasonable results are obtained with dispersivity on the scale of the pore size of the porous rock which correctly describes mixing on the molecular scale the method is applied to a simple 1 d domain without convective flow and a constant gradient of salinity as presented by rezaei et al rezaei m sanz e raeisi e ayora c vazquez sune e carrera j 2005 reactive transport modeling of calcite dissolution in the fresh saltwater mixing zone journal of hydrology 311 1 4 282 298 our results exhibit a sharper dissolution zone close to the freshwater side of the domain which is caused by the properties of the second derivative of c eq s recently singurindy et al water resources research 40 2004 and correction in water resources research 41 2005 performed dissolution experiments in a saltwater freshwater mixing zone in a sandbox the results from our model simulations are in good agreement to their experimental data finally the modelling approach is employed to porosity evolution in homogeneous and heterogeneous carbonate islands the results are in general agreement to earlier work due to the properties of the second derivative however the regions of active dissolution are restricted to more narrow regions

ice age vegetation and climate of subtropical chile abstract vegetation and climate of subtropical chile over the past 50 000 yr are reconstructed from pollen spores and other microfossils contained in a 10 7 m section of lacustrine deposits of laguna de tagua tagua 34 30 s 71 10 w controlled by 14 radiocarbon age determinations five pollen assemblages covering stratigraphic zones in the section represent plants on the upland and species inhabiting the lake basin surface pollen spectra from 58 stations approximately 30 40 s form an adjunct for interpreting past vegetation and climate from the fossil record temperature semi humid woodland of southern beech nothofagus dombeyi type and podocarp prumnopitys andina was apparently established about laguna de tagua tagua during the pleistocene contrasting existing semi arid broad sclerophyllous vegetation the woodland was extensive about the lake at the time of the last glacial maximum 25 000 14 000 yr b p and earlier 43 000 34 000 yr b p pollen from the families chenopodiaceae and amaranthaceae which characterize intervals of the pleistocene centered around 33 000 and 43 000 yr b p and the holocene suggests intervening episodes of relative aridity lake level fluctuations appear to follow the late quaternary climatic pattern implied by pollen assemblage data water in the lake was relatively high during development of southern beech podocarp woodland whereas during intervals of chenopod amaranth dominance lake levels were comparatively low excess precipitation over evaporation which during the pleistocene favored development of woodland of beech and podocarp is attributed to greater storm frequency conditions were apparently governed by strengthening of atmospheric circulation in the belt of southern westerly winds in the late glacial the temperate and more humid ice age climate with limited seasonality underwent transition to a subtropical semi arid mediterranean type that identifies the postglacial fluctuations in intensity of the southern westerlies marked by latitudinal movement of the polar front can account for past vegetation changes at laguna de tagua tagua

late quaternary landscape development at the margin of the pomeranian phase mis 2 near lake wygonin northern poland abstract in central europe late quaternary landscapes experienced multiple phases of geomorphologic activity in this study we used a combined geomorphological pedological sedimentological and palynological approach to characterize landscape development after the last glacial maximum lgm near lake wygonin in northern poland the pedostratigraphical findings from soil pits and drillings were extrapolated using ground penetrating radar gpr and electric resistivity tomography ert during the pomeranian phase glacial and fluvioglacial processes dominated the landscape near lake wygonin at the end of the glacial period periglacial processes became relevant and caused the formation of ventifacts and coversands containing coated sand grains at approximately 15 290 14 800 cal yr bp a small pond formed in a kettle hole profile bwi 2 the lacustrine sediments lack eolian sand components and therefore indicate the decline of eolian processes during that time the increase of juniperus and rock rose helianthemum in the pollen diagram is a prominent marker of the younger dryas at the end of the younger dryas a partial reshaping of the landscape is indicated by abundant charcoal fragments in disturbed lake sediments no geomorphologic activity since the beginning of the holocene is documented in the terrestrial and wetland archives the anthropogenic impact is reflected in the pollen diagram by the occurrence of rye pollen grains secale cereale and translocated soil sediments dated to 1560 1410 cal yr bp proving agricultural use of the immediate vicinity with the onset of land use gully incision and the accumulation of colluvial fans reshaped the landscape locally since 540 460 cal yr bp further gully incision in the steep forest tracks has been associated with the intensification of forestry outside of the gully catchments the weakly podzolized rubic brunic arenosols show no features of holocene soil erosion

quaternary aeolian activity of eastern europe a poland case study abstract the emergence of the pleistocene aeolian processes and their intensity was revealed through morphoscopy the observation and analysis of quartz grain shape and microtexture sediments from 39 cored boreholes and three outcrops located in central and eastern poland were analysed using methodology developed in 1942 by cailleux to identify past wind action this method is based on the recognition of the degree of roundness observed on quartz grains along with their surface typology matt or shiny the obtained results allowed us to separate seven distinct periods where the content of quartz grains with matt surfaces and varying degrees of roundness increased indicating the presence of an aeolian environment these processes were different in their nature and intensity with the wind action periods varying from long lasting and very intense identified across the entire research area to periods with low intensity and local wind action events these periods can be correlated with the advance of oldest glacials the narevian nidanian mis 36 34 mis 22 the sanian 1 mis 16 the sanian 2 mis 12 the advance and retreat of the odranian ice sheet mis 6 maximum stadial and the odranian glaciation mis 6 post maximum stadial wartanian these aeolian processes lead to the formation of coversands and fluvial sediments that are rich in aeolianized grains

fossil beetles from pilauco south central chile an upper pleistocene paleoenvironmental reconstruction abstract a new assemblage of fossil beetles of upper pleistocene age dated between 15 754 and 14 697 cal yr bp is described and interpreted based on cluster analysis in this study we present an analysis on the taxonomic composition and the paleoenvironmental implication of the fossil beetle assemblage in the archaeo paleontological site of pilauco in osorno south central chile 40 34 s 73 07 w around 17 370 cal yr bp at the onset of deglaciation the old damas river abandoned its alluvial plain afterwards wetlands grew up by deposition of peat and colluvial sediments the fossil beetles were deposited in the pb 7 layer where human artefacts and vertebrate remains have been found in the same spatial and temporal context the assemblage includes 13 families documented by 285 skeletal remains of fossil beetles ten ecological groups were identified and related to riparian epigean nothofagus sp forests and lotic environments such as streams and ponds dung and fungi beetles were also part of the fossil assemblage pollen and carpological investigations in the same strata point towards the presence of wetlands and evergreen north patagonian rainforest communities in the pilauco site during the upper pleistocene however this study reveals that the pilauco fossil beetles do not completely conform to any of the known modern assemblages therefore we interpret that the fossil beetle assemblage from pilauco is the result of the coexistence of different small pockets of habitats in a reduced spatial setting during a period of deep environmental anthropic changes at the end of the last glaciation the carabids and dung beetles from these beds indicate that the wetlands may have undergone dry conditions for undetermined periods of time finally we compare nearly contemporaneous beetle assemblages of the sites pilauco and monte verde ii to discuss differences and similarities between the sites

variation in holocene el nino frequencies climate records and cultural consequences in ancient peru analysis of mollusks from archaeological sites on the north and central coasts of peru indicates that between ca 5800 and 3200 2800 cal yr b p el nino events were less frequent than today with modern rapid recurrence intervals achieved only after that time for several millennia prior to 5 8 ka el nino events had been absent or very different from today the phenomena called el nino have had severe consequences for the modern and colonial historically recorded inhabitants of peru and el nino events also influenced prehistoric cultural development the onset of el nino events at 5 8 ka correlates temporally with the beginning of monumental temple construction on the peruvian coast and the increase in el nino frequency after 3 2 2 8 ka correlates with the abandonment of monumental temples in the same region

obsidian sources and distribution in patagonia southernmost south america abstract obsidian artifacts occur in some of the earliest occupied late pleistocene archaeological sites in patagonia such as pilauco 15 500 cal bp in south central chile and cerro tres tetas 12 100 cal bp in santa cruz argentina and they are very common in numerous early holocene sites trace element analysis of artifacts from these sites indicate long distance 300 to 1000 km transport of obsidian from nine different sources two of these sources chaiten ch and nevados de sollipulli ns are associated with active andean volcanoes in southern chile one around seno otway so occurs in the miocene volcanic belt in the southernmost andes the six others portada covunco pc cerro de la planicies lago lolog cp ll sacanana s telsen sierra negra t sn pampa del asador pda and cordillera baguales cb occur east of the andes in argentina geologic ages of these obsidians range from 17 8 ma sacanana to recent chaiten obsidian from each of these sources is generally homogeneous and chemically distinct from all the other sources those from the chilean andes are subalkaline in composition while those from the pampas of argentina east of the andes are alkaline and peralkaline chaiten obsidian occurs in marine culture sites along the pacific coast as far as 400 km to the north and south of this volcano and a few samples has been found 900 km to the southeast along the atlantic coast presumably transported there in a canoe green obsidian from seno otway was also exploited dominantly by marine cultures but occurs as well in terrestrial hunter gatherer sites such as pali aike and fell s caves from which junius bird first reported in 1938 prehistoric obsidian artifacts in patagonia distinctive black and red banded tiger striped obsidian from portada covunco has also been transported 500 km east to the atlantic coast as well as west into chile and to mocha island off the pacific coast perhaps because of its aesthetic appeal black alkaline obsidian from pampa del asador which includes at least four chemically distinct types has been distributed by terrestrial hunter gatherers 800 km northeast to the atlantic coast and south to tierra del fuego as well as west into chile the wide distribution 300 km of obsidian from each of these nine sources well beyond the range considered probable for direct procurement by patagonian terrestrial hunter gatherers 200 km implies the possibility of a considerable amount of cultural interaction among the prehistoric peoples of patagonia throughout the holocene

anthropogenic influence on rates of aeolian dune activity within the northern european sand belt and socio economic feedbacks over the last 2500 years in north western europe pleistocene sand sheets have been reactivated during phases of holocene deforestation and agricultural land use although there are temporal overlaps between anthropogenic activity and sand sheet reactivation the root cause and subsequent feedbacks between aeolian activity and societal response remain largely unknown here we seek to establish cause and effect by examining the detailed co variation in both timing and magnitude of aeolian and anthropogenic activity through the quantification of holocene dune sediments in combination with archaeological and pollen records these records indicate a series of complex phases of aeolian activity followed by landscape stabilization which we attribute primarily to changing patterns of human impact we find that a steady increase in dune deposition rates in the medieval period corresponds to an increase in settlement activity and deforestation ad 1000 1500 at their peak medieval deposition rates were 3 4 times larger than during th

late pleistocene ecological environmental and climatic reconstruction based on megafauna stable isotopes from northwestern chilean patagonia abstract stable isotope analyses have been performed on the bioapatite 13 c 18 o and collagen 13 c 15 n of four late pleistocene south american megafaunal taxa notiomastodon platensis equus andium cf hemiauchenia paradoxa and xenarthra indet to evaluate paleoclimatic and paleoenvironmental conditions as well as paleoecological features of this time period the analyzed megafauna was found at several locations in the northwestern chilean patagonia 38 42 s 74 71 w the bioapatite 13 c values indicated the presence of c 3 vegetation ranging from forestal to woodland areas the collagen 15 n values pointed to temperate and humid ecosystems and to the consumption of shrubs trees grasses and sedges mean annual temperatures estimated from bioapatite 18 o po4 values show a similarity to modern temperatures and suggested that the megafauna under study may have lived during warm stages interstadials of the late pleistocene when comparing our results with those obtained from other south american regions we find that the diet of this particular chilean megafauna appears to have been more influenced by resource availability than by the potential dietary range of the taxa

the late pleistocene pilauco site osorno south central chile abstract paleontological and archaeological sites have frequently been found in open locations of the intermediate depression of south central chile this paper presents the results of two field sampling seasons carried out at the pilauco site ca 39 s and compares them with those of three well known sites in chile quereo tagua tagua and monte verde ca 32 34 and 41 s respectively stratigraphic data collected at pilauco and the resulting radiocarbon age model suggest that before 12 540 90 bp the old damas river eroded an older volcaniclastic hill which was followed by a bog formation in an ox bow lake the site was developing up to 11 004 186 bp the date of the youngest vertebrate fossil two younger peat beds seal the site as in tagua tagua and monte verde gomphotheres are the most represented megafauna fossils of equidae camelidae cervidae mephitidae muridae myocastoridae and xenarthra are also found in pilauco as a whole 718 bones 30 teeth and 11 coprolites represent the extinct and extant vertebrates preliminary taphonomic results suggest action of various agents in the bones i e trampling root etching abrasion and carnivore gnawing the spatial analysis suggests the transfer of smaller anatomical units e g bones of camelids and horses and the rearrangement of some pieces comparatively large e g gomphothere bones similar to the present day north patagonian landscape the area where pilauco site is located had a variety of animal resources plants and stones in an ecotone between hills floodplains and wetlands a total of 101 lithics were recorded basalt and quartzite were collected from nearby fluvial deposits and dacitic obsidian from the local volcaniclastic deposits debitage is the most represented lithic item 75 cores and marginal edge trimmed artifacts represented 12 and 13 respectively artifacts and flakes are spatially and temporality associated in the same pb 7 bed with high bone concentrations in some specific areas between 361 and 424 cm of local altitude this industry is characterized by a recurrent lithic expedite technology with production of flakes and chips which mastered marginal retouches over the bifacial trimming this seems to be connected to strategic conditions of high resource diversity especially of human groups with a high or medium mobility across land pilauco represents a site contemporaneous to monte verde related as well to the first human occupation in the southern cone of south america but with higher mammal diversity

palaeosols and their cover sediments of a glacial landscape in northern central europe spatial distribution pedostratigraphy and evidence on landscape evolution abstract knowledge of the distribution types and properties of buried soils i e palaeosols is essential in understanding how lowlands in northern central europe have changed over past millennia this is an indispensable requirement for evaluating long term human impact including soil erosion and land cover dynamics in the serrahn area 62 km2 a young glacial landscape representative for northeastern germany and part of the muritz national park 26 pedosedimentary sections were documented and analysed to this end a multiproxy approach was applied using pedology micromorphology geochronology and palaeoecology statistical and spatial analyses of c 5200 soil profiles of which 10 contain palaeosols show that buried soils cover an area of 5 7 km2 i e 9 of the area studied most palaeosols are cambisols arenosols and gleysols palaeosols are mainly covered by aeolian and colluvial sands as well as by lacustrine sands and peat radiocarbon and luminescence dating together with palynological and anthracological data reveal that former land surfaces were dominantly buried through erosion triggered by human activity in the late holocene in addition but to a clearly smaller extent lateglacial early holocene palaeosols and cover sediments occur following medieval clear cutting and intensive land use the study area is today again widely forested the high share of buried land surfaces detected here is expected to be representative for the hilly glacial landscapes even in the wider region i e in northern central europe and should be considered in soil mapping soil carbon budgeting and assessments of past human impact

the fate of co2 derived from thermochemical sulfate reduction tsr and effect of tsr on carbonate porosity and permeability sichuan basin china abstract this article discusses the role of methane in thermochemical sulfate reduction tsr the fate of tsr derived co2 and the effect of tsr on reservoir porosity and permeability and the causes of the anomalously high porosity and permeability in the lower triassic soured carbonate gas reservoirs in the northeast sichuan basin southwest china the lower triassic carbonate reservoirs were buried to a depth of about 7000 m and experienced maximum temperatures up to 220 c before having been uplifted to the present day depths of 4800 to 5500 m but they still possess porosities up to 28 9 and permeabilities up to 3360 md the present day dry gas reservoirs evolved from a paleo oil accumulation and experienced varying degrees of tsr alteration as evidenced from the abundant sulfur rich solid bitumens and varying h2s and co2 concentrations tsr occurred mainly within the oil and condensate wet gas windows with liquid hydrocarbons and wet hydrocarbon gases acting as the dominant reducing agents responsible for sulfate reduction sulfur rich solid bitumen and h2s generation and calcite precipitation methane dominated tsr was a rather late event and had played a less significant role in altering the reservoirs intensive h2s and co2 generation during tsr resulted in calcite cementation rather than carbonate dissolution which implies that the amount of water generated during tsr was volumetrically insignificant 13c depleted co2 derived from hydrocarbon oxidation preferentially reacted with ca2 to form isotopically light calcite cements and the remaining co2 re equilibrated with the 13c enriched water rock systems with its 13c rapidly approaching the values for the host rocks which accounted for the observed heavy and relatively constant co2 13c values the carbonate reservoirs suffered from differential porosity loss by tsr involved solid bitumen generation and tsr induced calcite and pyrite precipitation intensive tsr significantly reduced the porosity and permeability of the intervals expected to have relatively high sulfate contents the evaporative platform dolostones and the platform margin shoal dolostones immediately underlying the evaporative facies early oil charge and limited intensity of tsr alteration together with very low phyllosilicate content and early dolomitization accounted for the preservation of anomalously high porosities in the reservoirs above the paleo oil water contact a closed system seems to have played a special role in preserving the high porosity in the gas zone reservoirs below the paleo oil water contact the closed system which is unfavorable for deep burial carbonate dissolution and secondary porosity generation was favorable for the preservation of early formed porosity in deeply buried carbonates especially sucrosic and vuggy dolostones have a high potential to preserve such porosity

radiocarbon chronology of the last glacial maximum and its termination in northwestern patagonia abstract we examine the timing and magnitude of the last glacial maximum lgm and the last glacial termination lgt in northwestern patagonia situated in the middle latitudes of south america our data indicate that the main phase of the lgt began with abrupt warm pulses at 17 800 and 17 100 cal yrs bp accompanied by rapid establishment of evergreen temperate rainforests and extensive deglaciation of the andes within 1000 years this response shows that south american middle latitude temperatures had approached average interglacial values by 16 800 cal yrs bp the temperature rise in northwestern patagonia coincides with the beginning of major warming and glacier recession in the southern alps of new zealand at southern mid latitudes on the opposite side of the pacific ocean from this correspondence the warming that began at 17 800 cal yrs bp appears to have been widespread in middle latitudes of the southern hemisphere accounting for at least 75 of the total temperature recovery from the lgm to the holocene moreover this warming pulse is coeval with the first half of the heinrich stadial 1 hs1 in the north atlantic region hs1 featured a decline of north atlantic meridional overturning circulation a southward shift of the westerly wind belt in both hemispheres and of the intertropical convergence zone as well as a weakening of the asian monsoon along with the initiating trigger identifying the mechanisms whereby these opposing climate signals in the two polar hemispheres interacted whether through an oceanic or an atmospheric bipolar seesaw or both lies at the heart of understanding the lgt

selective blackening of bioclasts via mixing zone aragonite neomorphism in late triassic limestone zlatibor mountains serbia a peculiar facies of the norian rhaetian dachstein type platform carbonates which contains large amounts of blackened bioclasts and dissolutional cavities filled by cements and internal sediments occurs in the zlatibor mountains serbia microfacies investigations revealed that the blackened bioclasts are predominantly solenoporaceae with a finely crystalline originally aragonite skeleton of fine cellular structure blackening of other bioclasts also occurs subordinately solenoporacean dominated reefs developed behind the platform margin patch reef tract were the main source of sand sized detritus the blackened and other non blackened bioclasts are incorporated in automicrite cement radiaxial fibrous calcite cements in the dissolutional cavities are also black dark grey or white reworked black pebbles were reported from many occurrences of peritidal deposits in those cases the blackening took place under pedogenic meteoric diagenetic conditions in contrast in the inner platform deposits of the ilidz ya limestone the blackening of bioclasts occurred in a marine meteoric mixing zone as indicated by petrographic features and geochemical data of the skeleton replacing calcite crystals attributes of mixingzone pore waters were controlled by mixing corrosion different solubility of carbonate minerals and microbial decomposition of organic matter in the moderate energy inner platform environment large amounts of microbial organic tissue were accumulated and subsequently decomposed triggering selective blackening in the course of early shallow burial diagenesis the d 18 o and d 13 c values of the mixing zone precipitates and replacive calcite do not produce a linear mixing trend variation mainly resulted from microbial decomposition of organic matter that occurred under mixing zone conditions the paragenetic sequence implies cyclic diagenetic conditions that were determined by marine meteoric and mixing zone pore fluids the diagenetic cycles were controlled by sea level fluctuations of moderate amplitude under a semi arid to semi humid climate

particle motion and the theory of charcoal analysis source area transport deposition and sampling principles from particle motion physics were applied to recurring problems of the interpretation of stratigraphic charcoal data 1 fires within catchments of lakes often produce no record in fossil charcoal curves and 2 periods characterized by no local fire e g 20th century fire suppression often display as much charcoal as times when local fire was frequent quantitative theory on source area transport deposition and sampling of charcoal shows the relationship between particle sizes counted by alternative methods of charcoal analysis pollen slides for particles 5 80 m in diameter petrographic thin sections for particles 50 10 000 m diameter and charcoal diagrams the relationship between diameter and critical and deposition velocities results in fundamental aerodynamic differences between the sizes of particles quantified by the two methods charcoal recorded on pollen slides is of a size that is difficult to lift but once entrained it remains in suspension thin section charcoal is lifted at relatively low wind velocities but it is not suspended at normal surface wind speeds thermal buoyancy during fire lofts charcoal above the forest canopy depending on particle size and wind speed pollen slide charcoal sizes are underrepresented near the fire because they remain in suspension and are preferentially exported from the burn area thin section charcoal is convected to lower heights on average and is deposited nearby following fire thin section charcoal is redistributed locally by wind and thus may enter lakes because of cohesive forces and aerodynamics more pollen slide charcoal remains on the ground and less enters lakes source areas for pollen slide charcoal are subcontinental to global and diagrams of pollen slide charcoal are biased toward nonlocal charcoal they can be used to interpret importance of fire for broad spatial and temporal scales thin section charcoal represents the catchment fire regime simulation models that generate charcoal during fire mix sediments and then sample at specified intervals indicate that 1 in the absence of sediment mixing the pollen slide method should consistently resolve individual fires that occur with an expectation of 30 50 yr 2 unless samples are continuous neither method will produce useful estimates of fire frequency and 3 even a modest amount of sediment mixing will obscure the signal

chronological database for southern chile 35 30 42 s 33000 bp to present human implications and archaeological biases abstract a chronological database of 398 dates 247 14 c dates 148 thermoluminescence dates and 3 obsidian hydration dates covering the early peopling period up to the present is presented for southern chile this information is used to assess both the paleodemography understood as human population dynamics in the past and the archaeo demography understood as the research dynamics of archaeologists in the present of that region from the early peopling up to the late archaic information is geographically and chronologically scarce and scattered the exception being the coast for this latter area it is possible to posit the existence of an occupation hiatus extending from at least around 3400 cal bp to around 2350 cal bp after this latter date a regional incremental trend is evident along with the earliest presence of ceramics as well as evidence of probable horticultural practices on the other hand the coast compared to the valley and cordillera has been the most active area for archaeological research and dating since the 1990s this database as a whole helps to expose research biases and current gaps in order to improve and expand our knowledge of the long history of southern chile s human occupation

seasonality of the enso related rainfall variability in central chile and associated circulation anomalies the seasonality of the enso rainfall relationship in central chile 308 418s and associated circulation anomalies are studied using correlation and compositing techniques during el nino episodes there is a tendency for the occurrence of above average precipitation between 308 and 358s in winter june july august jja and from 358 to 388s in late spring october november on while rainfall deficit is typically observed from around 388 to 418s during the following summer january february march jfm when el nino reaches its maximum development opposite rainfall anomalies are characteristic during la nina events this study confirms results from previous investigations indicating that enhanced blocking activity over the amundsen bellings hausen seas area in the southeastern se pacific during el nino is a key feature explaining the wet conditions in winter it is also shown that the same circulation anomaly explains the relatively wet conditions in late spring in the 358 388s region during el nino episodes furthermore the southward displacement from winter to late spring of the area with significant enso related rainfall anomalies seems associated with the seasonal migration of the boundary separating the region under the influence of the subtropical domain from the extratropical domain where the westerly regime and associated disturbances prevail blocking episodes in the se pacific during el nino seem to be part of a wave structure particularly intense during spring characterized by a sequence of positive and negative quasi barotropic height anomalies stretching southeastward from the equator toward the se pacific and back to the southwestern atlantic on the other hand anomalously dry conditions in winter and late spring during la nina are favored by long lasting and intense ridges at subtropical latitudes over the se pacific and south america resulting in a southward migration of the midlatitude storm tracks in summer a higher frequency of ridges in the southern tip of the south america during el nino episodes presumably contributes to reinforcement of the southern edge of the subtropical anticyclone in the se pacific which at this time of the year reaches its southernmost position resulting in the annual rainfall minimum on the other hand an increased frequency of cyclonic circulation anomalies crossing the southern tip of the continent is associated with relatively wet conditions in southern central chile particularly during la nina events