climate and collapse agro ecological perspectives on the decline of the tiwanaku state abstract after approximately 700 years of growth and colonial expansion the tiwanaku state disintegrated as a regional political force in the south central andes between c ad 1000 1100 this paper examines the collapse of the state of tiwanaku through the lens of its agricultural history we argue that the proximate cause of tiwanaku s decline as a politically integrated expansive state society was the deterioration and ultimate abandonment of its regional scale agricultural systems both in its core area in the andean altiplano and in its economic colonies in the lower altitude yungas zones we present evidence that the collapse of tiwanaku intensive agriculture was triggered by regional change in climatic conditions recorded in highly resolved palaeoenvironmental data derived from the quelccaya ice cap of southern peru and in sediment cores from lake titicaca our analysis of the quelccaya data documents a radical climate change in the south central andes during the post ad 1000 era in the form of a statistically significant decrease in mean precipitation level that persisted until c ad 1400 by defining vulnerability classes for various agricultural technologies used in different regions of the tiwanaku state we then relate this palaeoclimatic data to performance of specific core area and colonial tiwanaku agricultural systems we demonstrate that chronic drought conditions led to sequential collapse of these distinct agricultural systems irrigation based agriculture in tiwanaku colonies at lower altitude failed first followed by groundwater dependent raised field systems in the altiplano agricultural and settlement pattern changes in the post ad 1000 period are correlated with the palaeoenvironmental data to present an integrated view of the coupling of climate and cultural process the full implications of the agro ecological collapse model presented here reach well beyond an explanation for the decline of tiwanaku alone

spatial arrangement of soil mantle in glacis de buenavista mexico as a product and record of landscape evolution abstract factors controlling spatial soil organization have recently attracted the attention of soil scientists because they can contribute to regional management of soil resources we present here a case study in the glacis de buenavista mexico an extended volcanic piedmont in order to develop an integral understanding of its soil cover as a product and at the same time as a record of the main stages of landscape evolution three phenomena were considered luvisol and vertisol type soils and pedosediments all of them analyzed in terms of their development degree clay content macro and micromorphology selective extractions of fe fe d fe o silicon si o and aluminum al o weathering index and clay mineralogy luvisols represented in the ahuatenco mexicapa and buenavista sections are located in the northern and central part of the area they are red clayey polygenetic soils that show strong weathering with high kaolinitic clay content and high weathering index values clay illuviation and reductomorphic processes combined with vertic features in some parts of the profiles vertisols dominate the central and southern portion of the glacis they exhibit cracking angular blocks with wedge like shapes slickensides and stress cutans the pedogenesis of the vertisol type is clearly associated with the presence of smectitic minerals in the clay fraction as a product of neoformation factors controlling this pedodiversity are relief which affects bioclimatic differentiation within the studied landsurface and defines the lateral redistribution of moisture and dissolved substances and time luvisols represent a longer pedogenetic phase that started in the late pleistocene according to the age of buried paleosols while vertisols mainly originated in the late holocene according to the age of buried organic horizons pedosediments are located in the central area of the glacis here past and present geomorphic processes interact to produce the greatest soil diversity the recent human induced erosion partly destroyed polycyclic luvisols and exposed ancient subsurface pedosedimentary strata at the same time it produced patches of unconsolidated pedosediments consisting mostly of redeposited luvisol materials

geochemical and anthropogenic enrichments of mo in sediments from perennially oxic and seasonally anoxic lakes in eastern canada abstract we measured the vertical distributions of mo fe mn sulfide sulfate organic carbon major ions and ph in sediment porewater from one perennially oxic and three seasonally anoxic lacustrine basins in eastern canada as well as those of mo acid volatile sulfide fe mn al organic c 210pb and 137cs in sediment cores from the same sites the only input of anthropogenic mo to these lakes comes from atmospheric deposition the relatively monotonous distribution of mo in the porewater of three seasonally anoxic basins suggests that mo is not redistributed in the sedimentary column during periods of anoxia in contrast porewater mo profiles obtained at three sampling dates in a perennially oxic basin display sharp mo peaks below the sediment water interface indicating redistribution subsequent to deposition modeling of these latter porewater mo profiles with a diagenetic reaction transport equation coupled to comparisons among the various porewater and solid phase profiles reveal that mo is released at 1 2 cm depth as a consequence of the reductive dissolution of fe oxyhydroxides and scavenged both at the vicinity of the sediment water interface by re adsorption onto authigenic fe oxyhydroxides and deeper in the sediments where dissolved sulfide concentrations are higher the estimated rate constant for the adsorption of mo onto fe oxyhydroxides is 36 45 cm3 mol 1 s 1 diagenetic modeling indicates that authigenic mo in sediments of the perennially oxic basin represents about one third of the total solid phase mo in the first cm below the sediment water interface and only one tenth below this horizon if we assume that no authigenic mo is accumulated in the seasonally anoxic lake sediments we conclude that the sediment mo concentrations which are up to 3 16 times higher than the average lithogenic composition depending on the lake are mainly due to atmospheric deposition of anthropogenic mo and not to the formation of authigenic mo phases reconstructed historical records of the atmospheric mo deposition indicate maximum values in the 1970s and 1980s and significant decreases since then emissions to the atmosphere associated with the smelting of non ferrous ores and coal combustion appear to be the most important sources of anthropogenic mo

dating methods and geomorphic evidence of palaeoenvironmental changes at the eastern margin of the south peruvian coastal desert 14 30 s before and during the little ice age abstract the atacama desert is known to be one of the driest places on earth however in the study area between ica and nasca south peru 75 76 w 14 15 s palaeoclimate proxies show several semi arid phases during the holocene a more humid period during the early holocene favoured an open grass land which allowed the accumulation of desert loess eitel b hecht s machtle b schukraft g kadereit a wagner g kromer b unkel i reindel m 2005 geoarchaeological evidence from desert loess in the nazca palpa region southern peru palaeoenvironmental changes and their impact on pre columbian cultures archaeometry 47 137 158 the paracas and nasca cultures existing in that region between the 9th century bc and 7th century ad had propitious conditions to evolve and to settle close to the rivers fed by the monsoonal precipitation in the cordillera occidental culminating aridity after 600 ad might have caused the collapse of the nasca civilization the onset of semi arid climate towards the end of the late intermediate period 14th century ad allowed a reoccupation of the area here we present 14c and osl data from sediments of river terraces a debris flow and loess snails scutalus sp indicating appreciable geomorphic activity between 1390 and 1714 cal ad this phase is isochronous to the little ice age period on the northern hemisphere and to an increase in the ice accumulation on the quelccaya glacier in the peruvian altiplano thompson l g mosley thompson e bolzan j f koci b r 1985 a 1500 year record of tropical precipitation in ice cores from the quelccaya ice cap peru science 229 971 973

soil chronosequence and geomorphology in a semi arid valley in the andes of southern peru abstract soil development particularly in relation to relative age of geomorphic surfaces was studied in a high altitude valley on the semi arid western side of the andes in southern peru seven major fluvial surfaces in the colca valley were recognized including floodplains stream terraces and fans associated with the rio colca and its tributaries soils were also briefly examined on pleistocene andesite flows within the valley and on high volcanic plateaus surrounding the valley field and laboratory work indicate that most soils on stable surfaces above the floodplain are mollisols and that there is a consistent pattern of increasing subsurface horizon development on successively higher and older fluvial surfaces from 3300 to 3800 m elevation a developmental sequence of argillic horizons duripans and carbonate accumulation is present on these fluvial surfaces soils on the oldest fluvial surfaces exhibit strongly developed argillic horizons underlain by calcic horizons and strongly cemented duripans that contain illuvial carbonate and clay substantial development of these horizons also occurs on colluvial surfaces with slopes up to at least 65 relative depths of subsurface horizons on steeper colluvial surfaces differ from those on gently sloping fluvial surfaces in that argillic horizons and duripans are amalgamated this study indicates that significant chemical weathering and strong subsurface pedogenesis occur in high altitude mountainous environments within the tropics in contrast to findings at high altitudes in other climatic zones

a 350014c yr high resolution record of water level changes in lake titicaca bolivia peru abstract sediment cores collected from the southern basin of lake titicaca bolivia peru on a transect from 4 6 m above overflow level to 15 1 m below overflow level are used to identify a new century scale chronology of holocene lake level variations the results indicate that lithologic and geochemical analyses on a transect of cores can be used to identify and date century scale lake level changes detailed sedimentary analyses of subfacies and radiocarbon dating were conducted on four representative cores a chronology based on 60 accelerator mass spectrometer radiocarbon measurements constrains the timing of water level fluctuations two methods were used to estimate the14c reservoir age both indicate that it has remained nearly constant at 25014c yr during the late holocene core studies based on lithology and geochemistry establish the timing and magnitude of five periods of low lake level implying negative moisture balance for the northern andean altiplano over the last 3500 cal yr between 3500 and 3350 cal yr b p a transition from massive inorganic clay facies to laminated organic matter rich silts in each of the four cores signals a water level rise after a prolonged mid holocene dry phase evidence of other significant low lake levels occurs 2900 2800 2400 2200 2000 1700 and 900 500 cal yr b p several of the low lake levels coincided with cultural changes in the region including the collapse of the tiwanaku civilization

allophane imogolite and gibbsite in coatings in a costa rican andisol abstract neoformation of allophane imogolite and gibbsite has been studied extensively in soils in humid climates but little is known about their micro distribution patterns such information may provide insight about the conditions at the micro site scale responsible for their formation and disappearance our study describes amorphous and crystalline coatings in a melanudand on a 18 000 yr old andesitic lava in costa rica fine textured white to yellow coatings could be observed in the b c and r horizon in the field in thin sections the coatings are translucent and isotropic in plane polarized light ppl indicating that they consist of amorphous material in the b horizon under crossed polarized light isotropic coatings show a gradual transition towards crystalline outer margins and spots while in ppl such transition cannot be observed suggesting a genetic relationship submicroscopical analyses reveal that the amorphous coatings in the r and c horizon consist of allophanic material with a molar al si ratio of 0 9 those in the b horizon consist of allophanic material and imogolite with a molar al si ratio of 1 4 the amorphous coatings resulted from precipitation of al and si liberated upon weathering of primary minerals in an initial stage of lava weathering the crystalline coating parts in the b horizon consist of gibbsite and represent the ultimate stage of mineral neoformation the different coating composition in the soil horizons is the result of different leaching conditions at a macro and micro scale care should be taken to compare results obtained at different sampling scales with different analytical methods

soil land use and landform relationship in the precambrian lowlands of northern ethiopia abstract soil landscape and vegetation pattern at a detailed scale 1 20 000 is non existent in the precambrian dominated lowlands 500 1500 m above sea level of northern ethiopia current studies at a detailed scale in the region have focused on the basalt and mesozoic rock limestone and sandstone dominated highland 2300 m above sea level areas the aim of this research was therefore to explain the soil distribution as a function of lithology land use and landform and to develop a methodology for up scaling to similar environments this study was conducted at aqushala watershed in the precambrian rock dominated avergelle lowlands the research was done based on a discrete model of spatial variation dmsv soil units identified 1 in the metamorphosed black limestone formation are vertic endoleptic calcisol humic at the upper slope plateau both vertic endoleptic cambisol calcaric humic and vertic leptosol calcaric humic at the middle slope hill hypercalcic calcisol at the foot slope and grumic vertisol calcaric humic at the lower slope valley bottom majority of the soil units were under cultivation 2 in the schist and slate formations are leptosol calcaric humic both at the upper slope and at the foot slope positions regosol calcaric over hypercalcic calcisol at the mid slope position and fluvisol calcaric humic at the valley bottom and 3 in the green reddish gray metamorphosed banded marl formation are leptic calcisol at the upper slope haplic calcisol at the foot slope and fluvisol calcaric humic at the valley bottom the model was tested in the taget control watershed and was 73 successful so if this model is used it can help a lot in every aspect of agricultural or natural resource management and planning processes

quaternary normal and reverse faulting and the state of stress in the central andes of south peru field studies in the andes of southern peru show that in the high andes and pacific lowlands quaternary and recent faults are normal this extensional tectonics postdates compressional deformations of pliocene early quaternary age in the sub andes the observed deformations are compressional they affect early quaternary deposits some of the faults separate quaternary deposits from the bedrock and thus are clearly of tectonic origin and not landslide effects striations on the fault planes indicate n s trending extension in the high andes and pacific lowlands the total amount of crustal stretching is small probably of the order of 1 during the last 1 2 m y in the sub andes folds and faults affecting neogene and early quaternary deposits result from n s shortening nevertheless it is supposed that this n s shortening is of early quaternary age the present day compression probably strikes e w judging from focal mechanisms in the sub andes of central peru southern bolivia and northwest argentina data from structural analysis of faults and from earthquake focal mechanisms allow us to surmise the state of stress in the andes of southern peru the high andes and pacific lowlands subjected to n s trending extension are bounded by two zones of e w trending compression the sub andes to the east and the contact between the convergent nazca and south america plates to the west in our model the maximum horizontal compressive stress trajectory hmax is roughly parallel with the e w convergence between the two plates hmax corresponds to 1 in the sub andes and to 2 in the high andes the latter situation is caused by the elevated mass of the high andes where zz the vertical stress is inferred to be 1 thus the third principal stress axis being orthogonal to the other two axes it is oriented n s allowing extension to occur in that direction on the other hand in the sub andes zz is 3 and horizontal e w shortening occurs the state of stress in the andean continental crust above the 30 dipping slab appears to be different from that in the andes of central peru situated above the flat subducting segment in this region compressional deformantion affect a wider part of the cordillera

pedosedimentary cultural and environmental significance of paleosols within pre hispanic agricultural terraces in the southern peruvian andes paleosols were exposed in sections through four abandoned pre hispanic agricultural terraces surrounding an infilled mire basin in the southern peruvian andes the two paleosols beneath the tocotoccasa terrace represent the original natural solum and a later soil formed after construction of the agricultural terrace probably during the early middle horizon cultural period 615 695 ad the soil at the current surface developed subsequent to the building up and reconstruction of the terrace possibly during the late late intermediate period 1200 1400 ad micromorphology revealed an unexpected abundance of clay coatings within the upper terrace paleosol and surface terrace soil a phenonemon attributed to the migration and or accumulation of neoformed clay produced from the weathering of very unstable volcanic clasts perhaps fuelled by arid humid climatic oscillations and or seasonal input of irrigation waters the paleosols at tocotoccasa could not be correlated with any degree of confidence with those beneath the other three terraces due to differences in pedosedimentary properties and uncertainties over chronological controls thus it seems likely that either the terraces were re constructed and utilised over different cultural periods or that there is significant variation in the extent of weathering of material used for reconstruction of the terraces unfortunately it cannot be ascertained from the data available whether the terraces were abandoned for any significant period of time prior to reconstruction and if so whether this was a regional phenomenon related to climate social or economic changes

weathering and clay mineral formation in two holocene soils and in buried paleosols in tadjikistan towards a quaternary paleoclimatic record in central asia abstract the upper part of the karamaydan section tadjikistan shows the most detailed loess paleosol sequence yet known for the brunhes chron and the central and lower parts of the chashmanigar section provide similar detail for most of the matuyama chron to enable paleoclimates to be deduced the primary and secondary minerals in the silt and clay fractions must be determined separately to evaluate the type and intensity of mineral weathering and clay mineral formation to distinguish between inherited and pedogenetically formed clay minerals the original petrographic homogeneity of the parent material from which a soil developed must be established the main sources of pedogenic clay minerals are phyllosilicates in the silt fractions illites and vermiculites are the dominant pedogenetically formed clay minerals in the b or bt horizons of the holocene climaphytomorphic soils and in all paleosols s and pedocomplexes pk in karamaydan and chashmanigar except s xvii in which large amounts of smectites were formed there is little difference in the type and amount of pedogenic clay mineral formation between the holocene soils and the paleosols in the brunhes epoch at karamaydan as well as during most of the matuyama epoch at chashmanigar these results indicate that the climates of the interglacials represented by the b or bt horizons of the buried paleosols of young mid and old pleistocene age were similar to that of the holocene

soils of the main ethiopian rift valley escarpment a transect study abstract the mountainous environment of the ethiopian highlands has a great variety of ecotopes and thus demands great flexibility in land management different climatic conditions and landscape positions induce different soil forming processes leading to various soil types with specific risks and potentials the present study portrays a soil sequence of the central section of the main ethiopian rift valley from the footslopes of the eastern escarpment to the marginal volcano structures six profiles under natural vegetation are described for classification according to the usda soil taxonomy and world reference base for soil resources classification systems and special site characteristics are discussed the acacia savannah of the footslopes 1900 m a s l is characterized by vertisols mazic vertisols aridic haplusterts with often pronounced effects of seasonal waterlogging all other soils are well drained and reflect the general increase in rainfall with elevation and slope causing a decline in topsoil ph and a change from cation rich clay soils of the podocarpus dominated forest at 2300 m a s l mollic nitisols typic palehumults to strongly leached humic umbrisols humic dystrudepts of the hagenia dominated forest around 2600 m a s l the highland savannah plain 2700 m a s l with a drier and cooler environment has typically mollic cambisols dystric haplustepts which are less leached and have a rather brownish colour at 2900 m a s l niti umbric alisols andic hapludalfs are found in the hypericum forest at the midslopes of the marginal volcanoes receiving high rainfall whereas soil development is at a more initial state in the erica dominated forest at 3200 m a s l umbric andosols alic hapludands clay mineral composition is kaolinite dominated for the upper five profiles with a high proportion of poorly crystalline components in the upper savannah and the volcano upslopes the lowermost profile probably has a polygenetic origin indicated by an abrupt change from a smectitic to a kaolinitic composition in the subsoil soil development on quite homogeneous bedrock appears essentially controlled by relief and climate underlining the suitability of the region as a model area for in depth gradient studies on ecosystem processes and land use

soil catena variation along an alpine climatic transect northern peruvian andes abstract morphological and chemical properties of soils developed on end moraines of mostly quartzitic and granitic composition in the puna region of the northern peruvian andes vary with slope position and climate soil development was assessed on two catenas of similar age range 8 12 ka in two different precipitation zones at summit backslope and footslope positions soil properties that show trends downslope and with increased rainfall are greater clay content greater organic carbon content and greater pedogenic fe content in addition ph is lower in the higher rainfall area eolian material mixed loess forms the surface layer a horizon and may be responsible for the remarkable slope stability in the area it is suggested that mixed loess provided material for chemical alteration and translocation of clay and fe vertically and downslope in quartz rich parent materials soil data suggest that the amount of climate change during the holocene is limited it is doubtful if the climate at the wetter end of the transect ever existed at the drier end

the role of pedogenesis in palaeosols of mexico basin and its implication in the paleoenvironmental reconstruction abstract most of the paleoenvironmental information for the basin of mexico comes from sedimentary proxies which unfortunately are incomplete for the terminal pleistocene and the holocene in this paper we present a temporal and spatial reconstruction of past soil cover in the south and north of the basin of mexico during the mis 2 and 1 marine isotope stage 2 and 1 palaeosol profiles were selected from three locations cuicuilco copilco and avon in the south basin and compared with soils studied in the teotihuacan valley pachuca and texcoco at north of the basin the results show that the pleistocene soil cover is more homogeneous dominated by the presence of luvisol type soils with secondary carbonates dated to around 20 000 cal yr bp during the holocene the soil distribution changes with andosols developing in the south while vertisols and calcisols form in the north the new soil distribution reflects differing climate conditions during the holocene conditions which characterize the basin today the andosol cover in south basin however represents the result of short term pedogenesis andosols are considered high quality soils that were attractive to settlers and were a factor in the development of sedentary villages

rates of pedogenic processes in volcanic landscapes of late pleistocene to holocene age in central mexico abstract the transmexican volcanic belt and its many volcanic fields of different ages offer good opportunities to study soil development on volcanic tephra of intermediate to basaltic composition we studied a soil chronosequence within the sierra chichinautzin volcanic field scvf south of the basin of mexico and aimed to establish the rates of pedogenic processes this field has been active for around 50 000 years and produced 221 cinder cones with their respective lava flows we selected 11 sites located on 14 c dated lava flows of ages between 1800 and 30 500 bp at 3100 3200 m above sea level covered with pine fir forest with an ustic soil moisture regime and an isomesic soil temperature regime we also included a younger site 1000 bp and three older sites 100 000 years two at 3100 masl and one at 2600 masl from nearby volcanic fields to widen the time frame of the chronosequence soil profile samples were analysed for total organic carbon as well as for mineral neoformations related to clay contents selective chemical extractions and x ray diffraction analyses within the scvf the total soil thickness carbon accumulation and al si and fe extracted with acid ammonium oxalate increased linearly with age on surfaces up to 10 000 years old at rates of 19 cm ky 1 4 1 kg c m 2 ky 1 4 6 kg al 2 7 kg si and 2 kg fe m 2 ky 1 respectively crystalline clay and iron oxide formation reach a maximum at the oldest site located at 2600 masl of 1650 kg clay m 2 and 70 kg fe d m 2 their increase is linear up to ages of 10 000 years at rates of 22 kg clay m 2 ky 1 and 2 8 kg fe d m 2 ky 1 thereafter the rates are much slower allophane and allophane like minerals dominate in the clay fraction at all sites of the chronosequence and small amounts of halloysite can be identified in soils older than 6200 years while kaolinite was only identified at the three oldest sites 100 000 years the linear increases of all indicators of pedogenesis in the first 10 000 years are presumably driven by recurrent tephra deposition during this time frame thereafter erosion and colluviation processes seem to disturb pedogenesis changing its rates and redistributing its products in the landscape

subdivision of late pleistocene moraines in the cordillera blanca peru based on rock weathering features soils and radiocarbon dates abstract the progressive development of unusual rock weathering features and soils and minimum limiting radiocarbon dates provide a basis for subdividing four groups of late pleistocene moraines on the west side of the cordillera blanca northern peru 9 20 1 000 s 77 10 77 30 w boulders on the youngest late pleistocene moraines have 10 to 14 cm tall weathering posts soils on these moraines yield mean profile development index pdi values of 0 05 0 04 1 these moraines date between ca 13 500 and 9700 500 yr b p older than previously postulated the next older moraines have boulders with weathering post heights between 20 and 25 cm and soils with pdi values of 0 08 0 07 and were deposited prior to 13 280 190 yr b p probably during the last glacial maximum marine isotope stage 2 moraines from an older glaciation have boulders with weathering posts between 39 and 50 cm high soils that yield pdi values of 0 21 0 07 and are older than 19 700 340 yr b p boulders on moraines from a still older glaciation have lost ca 50 of their above ground volume and have weathering posts between 62 and 70 cm high pdi values for soils on these moraines are 0 32 0 06 linear and logarithmic models of weathering post and soil development with time are used to estimate minimum and maximum ages for the two oldest moraine groups linear models suggest that the second oldest moraines are between ca 20 500 and 46 500 yr b p and that the oldest moraines are between ca 29 000 and 72 000 yr b p in contrast logarithmic models suggest ages of greater than ca 75 500 yr b p and greater than ca 500 000 yr b p respectively

comparison of soils in midwestern united states and western europe with the interglacial record abstract paleosols that formed primarily before the last glaciation cannot be adequately explained by a model of holocene like interglacial periods of about 10 000 yr in length which has been inferred from the marine 18 o 16 o record geological and palynological evidence from terrestrial midlatitude sites suggests that temperate conditions conducive to soil formation existed for periods greatly in excess of 10 000 yr during the middle and late pleistocene available data on soils formed during this interval from western europe and midwestern united states are best explained by relatively long interglaciations or the development of composite soils over a number of temperate periods climatic contrasts between the interglaciations appear to have been overemphasized widespread assumptions regarding greater warmth in interglaciations prior to the present one are generally unproven in the absence of precise dating progress in relating paleosols to fragmentary local records of quaternary climatic changes will be achieved by detailed analytical techniques such as soil micromorphology

late pleistocene and holocene paleoenvironments of chalco lake central mexico abstract in order to establish paleoenvironmental conditions during the late quaternary four cores from the basin of mexico central mexico were drilled in chalco lake located in the southeastern part of the basin the upper 8 m of two parallel cores were studied using paleomagnetic loss on ignition pollen and diatom analyses based on 11 14c ages the analyzed record spans the last 19 000 14c yr b p volcanic activity has affected microfossil abundances both directly and indirectly resulting in absence or reduction of pollen and diatom assemblages important volcanic activity took place between 19 000 and 15 000 yr b p when the lake was a shallow alkaline marsh and an increase of grassland pollen suggests a dry cold climate during this interval abrupt environmental changes with increasing moisture occurred from 15 000 until 12 500 yr b p the lake level increased and the pollen indicates wetter conditions the highest lake level is registered from 12 500 to ca 9000 yr b p the end of the pleistocene is characterized by an increase in humidity from 9000 until ca 3000 yr b p chalco lake was a saline marsh and the pollen record indicates warmer conditions after 3000 yr b p the lake level increased and human disturbance dominates the lacustrine record

climate variation and the rise and fall of an andean civilization paleolimnological and archaeological records that span 3500 years from lake titicaca and the surrounding bolivian peruvian altiplano demonstrate that the emergence of agriculture ca 1500 b c and the collapse of the tiwanaku civilization ca a d 1100 coincided with periods of abrupt profound climate change the timing and magnitude of climate changes are inferred from stratigraphic evidence of lake level variation recorded in14c dated lake sediment cores paleo lake levels provide estimates of drainage basin water balance archaeological evidence establishes spatial and temporal patterns of agricultural field use and abandonment prior to 1500 b c aridity in the altiplano precluded intensive agriculture during a wetter period from 1500 b c to a d 1100 the tiwanaku civilization and its immediate predecessors developed specialized agricultural methods that stimulated population growth and sustained large human settlements a prolonged drier period ca a d 1100 1400 caused declining agricultural production field abandonment and cultural collapse

pedogenic gradients for iron and aluminum accumulation and phosphorus depletion in arctic and alpine soils as a function of time and climate pedogenically significant chemical extracts of iron aluminum and phosphorus are related mainly to time in chronosequences from baffin island canadian arctic the alpine sierra nevada and wind river range western united states the alpine khumbu glacier area himalaya nepal and the alpine southern alps new zealand based on the accumulation index for fe and al and the depletion index for p in each region the following ranking of chemical pedogenic development is obtained southern alps khumbu glacier area wind river range sierra nevada coastal baffin island inland baffin island the ranking mainly follows regional climate with the greatest accumulation and depletion to the warmest and wettest environment and the least accumulation and depletion in the coldest and driest environment

weathering of upper quaternary tephras in new zealand 2 clay minerals and their climatic interpretation abstract forty two tephra beds that have successfully mantled the landscape during 250 000 yr at ahuroa road te kuiti new zealand have each in turn been weathered to allophane and halloysite al rich allophane proto imogolite allophane dominates in all beds except four which have greater amounts of halloysite allophane and halloysite appear to have been stable for the past 250 000 yr and the nature of the parent tephra has not influenced the type of clay formed the analytical data show that the sequence can be sub divided into two sections at bed ah 33 three quarters of the way up the sequence beds in the upper section are younger than 70 000 yr b p and have lower allophane lower total clay higher rates of accumulation and show poor colour contrast the lower section beds have high allophane high total clay lower rates of accumulation and strong colour contrast the allophane rich beds are considered to have weathered under conditions of warm temperature and moderate to high rainfall high si leaching situations during interglacial periods three of the four halloysite rich beds are considered to have weathered under low rainfall conditions low si leaching situations occurring during colder or glacial periods the last halloysite rich bed is found at the base of the sequence here halloysite is considered to have formed as a result of si enrichment when percolating waters perched in the coarse basal bed

description and classification of soils of the high elevation grasslands of central peru abstract little has been reported on the soils of the high elevation grassland known as the puna of peru the objectives of this study were to characterize and classify some of these little known soils on a 17000 ha area in the puna as part of a vegetation inventory morphological and chemical descriptions of eleven soils are presented soils differed mainly because of distinctions in topographic position slope and parent material topographic position strongly influenced moisture regimes of the soils which were grouped according to occurrence floodplains upland depressions glaciated uplands and unglaciated mountain slopes parent materials were alluvium glacial till siltstone residuum and colluvium derived from andesite limestone and siltstone the mineral soils had histic mollic umbric or ochric epipedons all upland mineral soils had argillic horizons upper profile horizons commonly had ph values between 4 and 5 high cec values in the upper horizons are attributed to high quantities of organic matter or amorphous clays derived from volcanic ash falls or both soils were tentatively placed in five taxa 1 mollic cryoboralfs 2 argic pachic cryoborolls 3 argic cryoborolls 4 typic cryohemists and 5 typic cryaquents

pre industrial human and environment interactions in northern peru during the late holocene the result of long term environmental and human interaction is a variety of potential human responses to major natural crises population aggregation or dispersal changes in economic strategies an

holocene pedogenesis along a chronotoposequence of soils from the altiplano to the cordillera real bolivian andes abstract the high mountains of central andean represents one of the most diverse and heterogeneous landscape of south america with very contrasting climates across an east west gradient that remains poorly investigated in terms of late quaternary soil formation climatic forces within a diverse pedogeomorphological framework generates a complex geoenvironmental scenario extremely susceptible to climatic changes from the high aridic bolivian altiplano to moist periglacial regions at high mountain and from these to the tropical rainforest downslope one finds soil chronosequences and different ecosystems the objective of this work was to describe and interpret chronological morphological physical chemical and mineralogical attributes of 18 profiles along a long and representative east west transect through the cordillera real at altitudes varying between 1800 and 5030 m a s l the parent material is lithologically diverse ranging from till fluvio glacial talus and loess sediments most soils show a sequence of o a c and c r with high organic carbon contents at surface and subsurface forming umbric horizons buried polycyclic organic layers are common and the 14c dating reveals a sequence of processes as one moves away from the glaciated peaks varying from 1500 to 6000 years bp the occurrence of paleo peatlands and past and present day hydromorphic areas bofedales result in widespread melanization trend with histic horizons and histosols formation in the bottomlands the relict degraded state of bofedales indicates a reduction of waterlogging in the altiplano in the late holocene resulting in increasing water shortage inceptisols occur at the high mountain sector under periglacial conditions and high slope instability and solifluxion in general soils are acid or high acid with low base saturation and high al saturation high mountain tundra soils at 5020 m are exclusively developed on moraines of resistant granodiorite and have low clay content and less mineralogical diversity soils at the western slope were affected by the last glaciation and show more diverse mineralogy with cryogenic features under dry open vegetation puna on the other hand soils at the eastern slope are associated with a greater climatic variation varying mineralogical attributes greater organic carbon mineralization and formation of organometallic complexes although most soils show influence of non crystalline minerals such as allophanes and amorphous fe oxides andic soil properties were apparently absent

climate variability on the yucatan peninsula mexico during the past 3500 years and implications for maya cultural evolution climate variability on the yucatan peninsula during the past 3500 yrs is reconstructed from the measurement of 18o in monospecific ostracods and gastropods in a 6 3 m sediment core from lake punta laguna mexico this late holocene record is divided into three periods based on changes in mean 18o values from 3310 to 178514c yr b p period i low mean 18o values indicate relatively wet conditions i e low evaporation to precipitation ratio e p mean oxygen isotopic values increased 178514c yr b p and the interval between 1785 and 93014c yr b p period ii was distinctly drier than the periods before or after the climate during the latter part of period ii was persistently dry with exceptionally arid events centered at 1171 1019 and 94314c yr b p equivalent to 862 986 and 1051 a d this interval of frequent drought was recorded at several other localities in mexico and central america and coincided with the collapse of classic maya civilization following the last arid event 18o values decreased abruptly at 93014c yr b p beginning of period iii signaling a return to wetter conditions that have generally prevailed to the present with the exception of a dry episode centered at 55914c yr b p 1391 a d the paleoclimatic record from punta laguna provides evidence that multi decadal and millennial scale changes ine poccurred on the yucatan peninsula during the late holocene these wet dry episodes may have influenced cultural evolution in mesoamerica

paleoenvironmental catastrophies on the peruvian coast revealed in lagoon sediment cores from pachacamac abstract paleoenvironmental reconstruction combining data from diatom pollen macrophytic and archaeological analyses had not been attempted previously for coastal peru we analyzed two radiocarbon dated sediment cores extracted from the sacred urpi kocha lagoon at the pre hispanic religious center of pachacamac ca ad 350 1533 near lima to characterize the paleoenvironment of the site the data reveal an environmental history characterized by alternating periods of severe drought and catastrophic flood recurrent pulses with distinctive sediment diatom pollen and macrophytic characteristics reflecting variations in water depth substrate turbidity and salinity usually contain a thick basal sandy storm deposit overlain by thin organic accumulations of peat gyttja and snails the most intense of these disturbance pulses when correlated with pollen plant macrofossils radiocarbon dates and regional proxy data provide local evidence of four major floods associated with sustained catastrophic el nino events tsunamis and or severe storms in the andean highlands over the last 2000 years

holocene soil chronofunctions southern alps new zealand abstract field and laboratory data for two soil chronosequences from the high country of the south island of new zealand suggest rapid soil formation rates the areas studied are the ben ohau range and the mt cook area where mean annual precipitation is about 1 and 4 m respectively most soil ages are estimated from the thicknesses of rock weathering rinds soil chronofunctions are derived for indices that depict field profile and color development and a modified index of profile anisotropy for laboratory data out of a possible 21 chronofunctions 16 are statistically significant at the 0 05 level and 8 are from each area most 13 of the chronofunctions best fit a power model and the remaining ones are split between linear 2 and exponential 1 models although problems exist in the purity of the chronosequences because other soil forming factors are not constant duration of pedogenesis seems to be the most significant factor in explaining the trends despite the large differences in mean annual precipitation between the two areas many of the derived curves for property vs time are quite similar

late holocene paleopedological records contained in tephra from el chichon volcano chiapas mexico abstract high rates of pedogenesis on unconsolidated volcanic materials imply the accelerated generation of the soil memory the purpose of this research was to extract the high resolution centennial scale paleopedological records from the late holocene paleosols of the el chichon volcano formed during the last 2000 years we studied buried monogenetic andosols on the dated tephras and a pedocomplex formed from a set of thin ash layers deposited on older acrisol derived from shales particle size distribution dcb extractable fe oxalate extractable fe al and si sand and clay mineralogy organic carbon content and stable c isotope composition in humus were evaluated and interpreted as the elements of the soil memory however some differences were found in properties of two buried soils especially in the kind of a horizons we attribute such differences of individual andosols to be caused by ancient human impact because it has been demonstrated that humid conditions persisted during the last 1300 years thus the drought that was supposed to provoke the collapse of the maya civilization at the end of i millennium a d should have been a short term event below the resolution of this paleopedological record the andic acrisol pedocomplex demonstrated the domination of the humid tropical climate over longer time intervals probably major part of the holocene with possible minor dry episodes

use of soils and palaeosols on volcanic materials to establish the duration of soil formation at different chronological scales abstract in this paper we present an overview of the mexican volcanic palaeosol sequences as a valuable tool to establish the duration of soil formation at different chronological scales we have selected four study cases which cover time intervals from decennial centennial to millennial pedogenesis the first case corresponds to the soils in el chichon volcano where the short interval between the eruptions gives the opportunity to study the soil formation in periods less than 500 years in this interval the transformation from regosol to andosol is observable in el nevado de toluca pedogenesis of longer duration 4000 to 6000 y characterizes a vitric andosol stage in this area the transformation of andosol to luvisol is also shown in periods longer than 10 000 years the third study case corresponds to the tlaxcala palaeosol sequence where pedogenesis in intervals from 10 000 to 100 000 years is observable in this case no andosols are present and a complete set of luvisols showing different properties is found this differentiation is not only related to the duration of the pedogenesis but also to the climatic conditions which lead to changes in specific properties clay content weathering of the primary minerals fed content in this way these soils are valuable for palaeoenvironmental reconstruction the fourth case is related to faster pedogenesis in the volcanic regions of mexico where highly developed luvisols are found formed in intervals less than 15 000 y in this case the influence of a pre weathered volcanic material as a source of clay allows the rapid transformation

hazard risk and agrarian adaptations in a hyperarid watershed el nino floods streambank erosion and the cultural bounds of vulnerability in the andean middle horizon abstract peru s osmore drainage also known as the moquegua valley is one of the driest regions on earth yet agricultural development has supported complex societies in the basin for almost 4000 yrs because of canal construction and irrigation we compare the distinct agrarian and settlement systems of three coeval archaeological cultures in this arid region huaracane wari and tiwanaku and how each adapted or failed to adapt to geomorphic and climatic hazards systematic settlement pattern survey and radiocarbon dating along with geomorphological analysis of flood history and riverine processes permit detailed discussion of agrarian strategies during the formative 1800 bc ad 500 and middle horizon ad 500 1000 periods with distinct settlement niches in terms of agricultural practices and longitudinal position in the drainage and lateral location relative to the floodplain these adaptive strategies each manifest distinct bounds of adaptability to natural hazard climate events and social stressors and thus varying risk profiles besides the continual risk associated with sustained droughts the atacama and peruvian coastal desert and culturally connected highland altiplano are also vulnerable to the vagaries of the el nino southern oscillation enso leading to catastrophic floods in the mid valley during warm phase ensos in tandem with simultaneous hazards in other regions inhabited by these transregional cultures by comparing the archaeological record of wari huaracane and tiwanaku culture settlements with geomorphic signatures of catastrophic el ninos we show that the viability of each cultural sequence depended on specific relationships to floodplain streambank erosion construction and reworking over multiple time scales

late quaternary tephra derived paleosols in central italy s carbonate apennine range stratigraphical and paleoclimatological implications abstract detailed stratigraphical pedological and geochronological 14c dating research was carried out on numerous sections located in the carbonate apennine range of central italy two paleosols late pleistocene pedomarker a and holocene pedomarker b in age were recognized as having developed from air fall pyroclastic material given their special properties and widespread distribution both soils represent valuable markers in the late quaternary stratigraphy of central italy information about the climatic conditions that have influenced their pedogenesis through time has been obtained pedomarker a formed under temperate wet conditions related to the last interstadial fluctuations of the pleniglacial its development ceased after ca 30 ka because of the onset of last glacial maximum dry cold conditions pedomarker b formed at the beginning of the holocene under udic and perudic soil moisture regimes its development ceased in some localities because of a change towards a drier climate after ca 4 5 ka petrographic and geochemical characteristics of the parent materials are discussed and correlations with the campanian ignimbrite pedomarker a and neapolitan yellow tuff pedomarker b both related to activity in the phlegrean fields are proposed

a pedogeographical view of volcanic soils under cold humid conditions the commander islands abstract we studied two representative profiles at the bering island the commander archipelago in the north of the pacific ocean the soils developed in the material of predominantly volcanic origin under cold humid marine climate one of the soils was classified as an andosol and the other as an albic podzol the two soils showed certain similarity in the morphology and properties thus supporting the hypothesis of their common pedogenetic origin the study of the composition of a coating of a sand grain indicated complex path of the genesis of the soils initially the coatings have been formed by allophanes with fe humus complexes then by allophanes with humus and then by fe humus and al humus components the analysis of the total elemental composition the distribution of the size fractions and the previously reported data on the mineralogical composition of the soils allowed suggesting a significant contribution of the external volcanic ash from the kamchatka peninsula in the genesis of the soils of the commander islands most probably the whitish layer includes acid volcanic glass transported by the wind the soils of the sub mountainous areas lack whitish layers because of erosion however the soils under study do not represent mere mixtures of different ash layers the newly deposited material was evidently incorporated in the soil profile we conclude that volcanic soils are specific natural bodies where sedimentary processes should be taken into account along with the pedogenesis

isotopic evidence for anoxic pyrite oxidation and stimulation of bacterial sulphate reduction in marine sediments pore water sulphate concentrations show marked increases at depths 50 m at odp sites 888 and 890 889 from the cascadia margin accretionary wedge in the uppermost 10 m sulphate concentrations decrease with depth and sulphate 34 s and 18 o increase as sulphate is removed by bacterial sulphate reduction isotopic data show that sulphate formed below 50 m results from oxidation of early diagenetic pyrite and that oxygen in the sulphate molecules is derived from pore water fe 3 in the sediment is the probable oxidizing agent the increased sulphate concentrations stimulate bacterial sulphate reduction at depths of 70 250 m and are thus important in sustaining deep bacterial activity

climatic and tectonic controls on pedogenesis and landscape evolution in a quaternary intramontane basin val d agri basin southern apennines italy abstract paleopedological studies of alluvial systems in intramontane valley settings provide useful tools for understanding the interaction of tectonics climate and local base level changes in controlling alluvial dynamics an example is reported from the quaternary alluvial deposits of the val d agri basin in southern italy which were accreted in response to cycles of deposition pedogenesis and erosion several buried weathering profiles representative of the main stratigraphic unconformities were characterized by field description and micromorphological analyses the profiles appear to be truncated at the top by intense erosion the main pedological features and their formative processes occurred polycyclically attesting to different and relict pedogenetic phases that are not in equilibrium with present day environmental conditions we interpret the weathering profiles as paleosols that developed mainly during pleistocene interglacial periods the peri glacial phases mainly caused erosion of devegetated slopes and soil truncation processes all of the paleosols in the val d agri basin offer useful information on the chronological reconstruction of climatic phases and the associated sequence of pedogenetic events during the quaternary in the mediterranean region

an integrated socio environmental approach to the study of ancient water systems the case of prehistoric hohokam irrigation systems in semi arid central arizona usa water systems lie at the interface between nature and culture and in that perspective are a rich but under explored research object their temporalities construction maintenance abandonment represent an image of a social cultural economic and political context as well as changing environmental conditions this socio environmental signature recorded in the spatial organization sedimentary fill and profile of hydraulic structures can be reconstructed by means of a systemic cross disciplinary approach geoarchaeology chronology and paleoenvironment the principle and limits of the methods applied to this research object are presented and discussed in this paper while they can be applied to different environmental contexts they will be presented through the example of hohokam irrigation systems in the semi arid phoenix basin arizona where this approach has been applied as a whole as water systems are structural elements of the spatial and socio political organization of societies this approach will provide elements to discuss the relative impact of human and or environmental factors on landscape change and cultural shifts and measure the long term vulnerability and resilience of agricultural communities to regional environmental changes

rates and processes of soil development on quaternary terraces in cajon pass california field and laboratory analyses of soils on 11 well dated fluvial terraces spanning the past 0 5 m y demonstrate that a threshold governs changes in several morphological and chemical characteristics of increasingly older soils correlations with respect to time among iron species soil morphology and soil silt and clay demonstrate that the chronosequence at cajon pass reflects primarily an evolutionary largely time dependent trend and does not reflect differences in external factors such as climate most of the soil development on holocene terraces of the cajon pass area is due to physical incorporation of eolian dust and organic material into initially very permeable gravels this process decreases soil permeability and is conducive for an increase in the magnitude of chemical weathering latest pleistocene and older pleistocene soils have developed clay and authigenic iron oxide rich b horizons at the expense of organic matter rich a horizons and color b horizons as the extent of chemical weathering has increased this conversion of the soil from a noncolloidal system to a much more colloidal system takes place over a relatively short period of time 4 000 yr and is herein defined as a type of pedologic threshold in the cajon pass area the attainment of the threshold and subsequent development of the argillic b horizon of soils on latest pleistocene terraces occurred during the holocene thus the absence of argillic horizons in soils on holocene terraces is attributable to simply their younger age rather than to the pleistocene to holocene climatic change the threshold is a function of several variables including influx rate of eolian dust and initial soil permeability therefore the time required to attain the threshold will vary in chronose quences characterized by geomorphic or geographic settings that are different from conditions found in cajon pass

quantifying rates of methanogenesis and methanotrophy in lake kinneret sediments israel using pore water profiles full seasonal sets of chemical and isotope profiles from the pore water of lake kinneret sea of galilee israel were produced to study methanogenesis and methanotrophy processes and the couplings between methane ch4 sulfur and iron sulfate is depleted within the upper 10 cm of the sediment mainly by traditional bacterial sulfate reduction by organic matter maximum sulfate reduction rates calculated from sulfate concentration profiles are found at the water sediment interface 0 1 cm 2 1 4 3 10212 6 0 2 3 10212 mol cm23 s21 ch4 concentrations and modeling of dissolved inorganic carbon dic and its stable carbon isotope d13cdic suggest that maximum methanogenesis rates of 2 5 3 10213 6 1 5 3 10213 mol cm23 s21 occur at 5 12 cm depth in the sediments and that it ends at 20 cm of the produced ch4 50 75 is converted to gas bubbles of ch4 before it reaches the bottom water model results suggest the occurrence of anaerobic oxidation of ch4 aom in the deep sediments of the lake below the zone of methanogenesis methane ch4 is an important greenhouse gas with emissions from anthropogenic and natural sources roughly estimated to be around 350 and 120 tg c yr 21 tg 2 1 3 1012 g respectively wuebbles and hayhoe 2002 among the natural sources continental emissions contribute more than 70 wuebbles and hayhoe 2002 however the parameters controlling these emissions are not well understood therefore it is essential to resolve the rate of the processes behind ch4 emissions from continental systems this study aims at this objective investigating lacustrine environment using a geochemical approach ch4 in its natural sources is produced mainly through microbial processes methanogenesis chemical profiles in pore water of organic rich sediments indicate that various microbes use a series of electron acceptors during the remineralization of organic matter in the order of decreasing chemical potential and methanogenesis accounts for the last stage of the microbial respiration in stratified lakes developing an anoxic hypolimnion methanogenesis and sulfate reduction are key terminal

mineralogy of a soil chronosequence on andesitic lava in humid tropical costa rica abstract we studied a chronosequence of three soils developed on andesitic lavas in humid tropical costa rica in order to investigate mineralogical development and to evaluate the importance of time versus other soil forming factors morphological chemical and mineralogical methods were used to unravel evolution of the soils primary minerals in the

magnetic properties of lake sediments from lake chalco central mexico and their palaeoenvironmental implications lake chalco 99 0 w 19 5 n in the basin of mexico was formed during the pleistocene after the emplacement of the chichinautzin volcanic field that closed the former drainage system the lake sediment record has been influenced by a number of factors including glacial interglacial cycles local volcanism erosion of soils and anthropogenic disturbances the magnetic properties of the lake sediments and the associated tephra layers of the last 16500 yr have been studied it is found that the magnetic properties of the lake chalco sediments are very distinctive magnetic concentration varies by a factor of 1000 and magnetic stability also varies over an extremely wide range the predominant magnetic mineral is titanomagnetite in addition to an imperfect antiferromagnetic phase possibly goethite an unusually large range of coercivities is found in certain of the tephras down core variations in magnetic properties closely follow climatic environmental changes previously established by other proxy methods the late pleistocene and late holocene lake sediments display a higher concentration of magnetic minerals than the early middle holocene sediments in the non volcanic sediments fluctuations in the magnetic concentration reflect changes in both the intensity of erosion as represented by ferrimagnetic and paramagnetic minerals and by the maturing of soils as represented by geothite copyright 2000 john wiley sons ltd

iron isotope fractionation in sediments of an oligotrophic freshwater lake abstract in situ iron fe isotope compositions of pore water and solid bound fe phases were measured in sediments of an oligotrophic sulfate poor freshwater lake lake tantare quebec canada previous work has shown that dissimilatory fe iii reduction dir is the main fe reduction pathway in this setting hence the lake sediments provide a well characterized natural environment in which to assess the transferability of dir produced fe isotope fractionations obtained in laboratory model systems iron redox cycling within the sediments produces isotopically light pore water fe ii average 56 fe 2 1 0 6 and sorbed fe ii average 56 fe 1 2 0 2 compared to the fe iii oxyhydroxide average 56 fe 0 6 0 2 and tightly solid bound fe ii average 56 fe 0 3 0 2 sediment pools the apparent isotope fractionation factor between aqueous fe ii and fe iii oxyhydroxides of 2 6 0 5 derived for lake tantare sediments falls within the range reported for experimentally determined isotopic fractionations during dir our results yield the first comprehensive set of fe isotope signatures associated with microbially driven fe redox cycling obtained directly in sediments of an oligotrophic freshwater lake

fluvial history of the rio ilave valley peru and its relationship to climate and human history fluvial strata and landforms in the rio ilave valley peru document a history of holocene aggradation and downcutting that is correlative with regional climatic events and provides an environmental context for human occupation of the river valley periods of aggradation correspond to periods of high or rising level in lake titicaca and elsewhere on the altiplano and increased sediment accumulation in the rio ilave valley downcutting episodes correspond to periods of low level in lake titicaca and low or rapidly decreasing sedimentation rates in the ilave delta there are five terrace tracts t1 through t5 present in this southwestern lake titicaca tributary these tracts occur as both paired and unpaired terraces and have average heights from 1 4 to 24 3 m above the valley floor the major part of the fluvial sequence was deposited during the time period from prior to the last glacial maximum until about 8300 calendar years before present cal bp a period of generally high but variable precipitation on the altiplano and high water level in lake titicaca initial deposition aggradation was followed by successive downcutting to the t4 and t3 terrace surfaces initial downcutting began immediately after precipitation runoff and sediment load decreased while base level dropped it was followed by a period of episodic equilibrium and minor downcutting that included a prolonged period of soil formation between v8350 and 6780 cal bp the major pulses of downcutting likely occurred between v6000 and 4500 cal bp and were coincident with periods of decreased precipitation on the altiplano and decreasing levels of lake titicaca two final periods of infilling resulting in deposition of the t2 and t1 terrace sediments at v4000 to 2500 cal bp and v2000 to 1600 cal bp during periods of rising water level in lake titicaca lacustrine sedimentation in the rio desaguadero valley and increased sedimentation offshore the ilave delta were separated by brief equilibrium stages and a brief downcutting event this fluvial history when coupled with regional paleoclimatic data relates to the region s preceramic through tiwanakuperiod archeological records archeological evidence indicates that humans occupied the ilave valley as early as 10 000 cal bp the higher terraces t3 t4 and t5 were occupied for at least 5000 years but humans did not utilize the lower terraces t1 and t2 until after v4400 3700 cal bp our results confirm that these lower terraces would not have been available for either occupation or agriculture until after v4000 cal bp 2003 published by elsevier science b v

a 25 000 year tropical climate history from bolivian ice cores ice cores that were recovered from the summit of sajama mountain in bolivia provide carbon 14 dated tropical records and extend to the late glacial stage lgs oxygen isotopic ratios of the ice decreased 5 4 per mil between the early holocene and the last glacial maximum which is consistent with values from other ice cores the abrupt onset and termination of a younger dryas type event suggest atmospheric processes as the probable drivers regional accumulation increased during the lgs during deglaciation and over the past 3000 years which is concurrent with higher water levels in regional paleolakes unlike polar cores sajama glacial ice contains eight times less dust than the holocene ice which reflects wetter conditions and extensive snow cover

paleosols beneath a lava flow in the southern basin of mexico the effect of heat on the paleopedological record abstract volcanic activity affects past and present landscapes here we present a case study related to the heat impact of the xitle lava flow on the former soil cover the eruption occurred 1670 years b p in south mexico city the evaluated properties include those related to the soil memory used as tools of paleoenvironmental interpretation in volcanic paleosols macro and micromorphology color grain size distribution magnetic susceptibility and carbon and nitrogen contents changes of these properties by the heat influence are relevant for an adequate paleoenvironmental reconstruction two sites and three soil profiles are selected to show soil modifications by the volcanic activity the two sites represent the following 1 slightly transformed paleosol buried by the lava flow but separated from it by a 10 cm thick volcanic ash layer site cuicuilco enah 2 moderately and strongly transformed paleosols two profiles inside the copilco archeological zone one of the copilco profiles represents a buried paleosol with a very thin 3 cm ash layer on top at the contact with the lava the second profile is the most affected by the lava flow as it is directly beneath the lava all studied paleosols are sandy have a low amount of organic matter narrow c n ratios and very high values of magnetic susceptibility the strongest modifications are observed in the upper horizons which are in contact with the lava however the presence of the ash layer minimizes the heat effect despite the observed modifications it is possible to establish three cycles of soil formation in the paleolandscape the first and the oldest related to the development of a luvisol type soil indicates a longer time of landscape stability during the second cycle a pedosediment with a high concentration of artifacts was formed the last and the youngest cycle includes the ab and the aeb horizons present only in copilco they form by an andosol type pedogenesis which reflects a shorter time of soil development the presence of the aeb horizon is interpreted as the result of the degradation of the ab horizon either due to the heat effect of the lava or to cultivation and irrigation practiced by the pre hispanic communities

a quantitative comparison of soil development in four climatic regimes abstract a new quantitative soil development index based on field data has been applied to chronosequences formed under different climatic regimes the four soil chronosequences developed primarily on sandy deposits have some numeric age control and are located in xeric inland merced calif xeric coastal ventura calif aridic las cruces n mex and udic susquehanna valley pa soil moisture regimes to quantify field properties points are assigned for developmental increases in soil properties in comparison to the parent material currently ten soil field properties are quantified and normalized for each horizon in a given chronosequence including two new properties for carbonate rich soils in addition to the eight properties previously defined when individual properties or the combined indexes are plotted as a function of numeric age rates of soil development can be compared in different climates the results demonstrate that 1 the soil development index can be applied to very different soil types 2 many field properties develop systematically in different climatic regimes 3 certain properties appear to have similar rates of development in different climates and 4 the profile index that combines different field properties increases significantly with age and appears to develop at similar rates in different climates the soil development index can serve as a preliminary guide to soil age where other age control is lacking and can be used to correlate deposits of different geographical and climatic regions

sand coatings in paleosols evidence of weathering across the plio pleistocene boundary to modern times on mt kenya abstract a comparison of younger post olduvai paleosol horizons with older buried horizons of plio pleistocene age shows that primary and secondary minerals and organic molecules in sand coatings in these paleosols remain intact and provide a record of past weathering events from ir spectra concentrations of organic and some inorganic constituents within these coatings reveal supporting evidence of variable weathering trends from late pliocene to holocene time with some variability hematite and goethite concentrations in sand coatings parallel similar variable concentrations of secondary fe extractable concentrations previously determined for pre and post olduvai paleosols in these mt kenya sections negative correlations between metahalloysite and gibbsite previously determined to result from aggressive leaching of si from metahalloysite in paleosols tend to follow similar distributions in the sand coatings reported here similarly additions of gibbsite in selected paleosol horizons are followed by reductions of lesser concentrations of metahalloysite suggesting that individual horizons within paleosols have independent leaching histories different from the entire paleo pedon as with these paleosols analyzed previously quartz exists in greater proportion within sands recovered from ah and ahb horizons and this mineral has previously been considered to be sourced from the older surrounding african crust rather than from local neogene volcanic sources the presence of vermiculite in sand coatings previously not detected in mt kenya paleosols may be related to the presence of cedar stands juniperus procera within the timberline zone of the mountain a forest species clay mineral correlate that may relate to past forest biome evolution specifically in the pre olduvai paleosols the occurrence of vermiculite in these older paleosols a clay species with a known affinity for conifers birkeland 1999 may indicate a higher timberline during pre olduvai time the outcome of this analysis shows that certain horizons act as a singular open weathering system responding to the throughput of either meteoric or groundwater in selective ways to produce a range of weathering products sourced from primary minerals and selective allochthonous mineral inputs from near and far more importantly sand coatings are shown to provide important paleoenvironmental data parallel to that recovered from macro paleosol systems moreover the wealth of paleoenvironmental data recovered from sand coatings rivals that in weathering rinds and the combined data are applicable to other paleoenvironments both on earth and mars

buried a horizons in old bench terraces in les garrigues catalonia abstract a large part of les garrigues western catalonia is occupied by stone terraces locally known as bancals that were built up in the 18th century some soil surveys of the area noted the presence of buried thick a horizons with a well developed crumb structure and darker colour than the present day a horizons the objective of this study was to determine the conditions of the soil cover both at the time of the formation of these buried soils and at the onset of terracing the climate is semi arid and the landscape is defined by platforms and flat bottomed valleys four profiles were described from both slope and valley floor terraces and sampled for analyses a buried ahb horizon appears at various depths between 40 and 180 cm with thicknesses ranging from 35 to 160 cm probably due to earthworks since this depends on the position of the profile within the terrace many of these buried soils would correspond to phaeozems they are identified by an ahb having low values and chromas usually 4 or less a structure due to faunal activity 100 of the structural forms related to fauna either in the form of empty or infilled channels vermic qualifier and an organic matter content that is 1 7 3 3 which is higher but not significantly different than the som content of the present day topsoils p olsen is 1 6 ppm the present soils are non saline and highly calcareous 40 they show some calcium carbonate redistribution in the form of pseudomycelia and biogenic calcite charcoal is present in some of these buried horizons together with small ceramic fragments these buried horizons have several common micromorphological features a spongy highly porous structure due to high faunal activity frequent silt cappings charcoal fragments and biogenic carbonates queras in some cases the biogenic calcite has undergone dissolution and reprecipitated as micrite pollen assemblages of the buried horizons reveal a large forest cover mainly of oaks and pines which is also corroborated by the occurrence of quercus phytoliths but the presence of pollen of some deciduous crops such as cereals vitis vinifera and olea europaea at the top of the sequences points to a upper holocene origin of these soils the results from the charcoal study support the presence of perennial quercus and pines as well as shrubs in the period when the terraces were built the available information about present day similar soils indicates that the formation of these horizons took place under a moister milder climate in the past compared with the present one in the study area

cadmium deposition and mobility in the sediments of an acidic oligotrophic lake abstract a dated core from the profoundal zone in a pristine oligotrophic acidic lake was analyzed for cd as well as for al ca fe mg mn pb ti and total carbon and nitrogen overlying water and porewater samples were also obtained on six occasions at the same site and yielded vertical profiles of ph and dissolved cd ca fe mg mn sulfide so 4 2 organic and inorganic carbon concentrations these extensive porewater and sediment geochemical data were used together with information on infaunal benthos to decipher the sedimentary record of cd contamination depth variation of sediment ca concentrations indicate that the lake suffered from progressive acidification starting about 1950 the present day accumulation rate of cd j acc cd 5 4 0 4 10 11 mol cm 2 yr 1 in the sediments is the sum of the flux of cd deposited with settling particles j s cd 3 3 0 2 10 11 mol cm 2 yr 1 and the fluxes of dissolved cd across the sediment water interface due to molecular diffusion j d cd 1 8 0 3 10 11 mol cm 2 yr 1 bioturbation j b cd 1 1 0 2 10 14 mol cm 2 yr 1 and bioirrigation j i cd 0 27 0 05 10 11 mol cm 2 yr 1 biological mixing of the sediments was negligible the shape of the vertical profile of total cd concentration with depth in the sediment appears to be determined more by its input history than by post depositional mobilization and redistribution in the sediment column

characterization of a weathering sequence of soils derived from volcanic ash in cameroon taxonomic mineralogical and agronomic implications the characteristics of eight pedons developed in quaternary basaltic pyroclasts in western cameroon under humid tropical conditions are reported the soil weathering sequence consists of an andept tropept udalf udult association andic properties physico chemical characteristics and weathering stage clearly distinguish the taxonomic units the total reserve in bases trb and the clay content measured after adequate h2o dispersion with na resins both appear to be suitable weathering indices clay mineralogy of non andic soils shows direct relationships between interstratified halloysite smectite content cec of the clay fraction and weathering stage the weathering stage of the investigated soils is reflected not only in their components and classification but also in their nutrient status and banana crop performance

thallium diagenesis in lacustrine sediments dated sediment cores and porewaters from two canadian shield lakes located 40 km from quebec city l tantare and 25 km downwind from an important smelter in northwestern quebec l vose were analyzed for thallium and other geochemical variables atmospheric deposition is the only source of anthropogenic tl to these lakes the porewater tl concentration profiles in l tantare display a peak below the sediment water interface that suggests post depositional tl remobilization and transport to the overlying water and deeper sediments such a dissolved tl peak occurs just above the sediment water interface in l vose modeling the porewater tl profiles with a diagenetic reaction transport equation reveals a zone of dissolved tl production lying above a zone of tl consumption in l tantare sediments in contrast in l vose tl diffuses across the sediment water interface from the anoxic hypolimnion and is fixed to the surficial sediments the localization of the consumption zones the shape of the dissolved tl sulfide and iron profiles as well as calculations of saturation states are all consistent with the removal of tl from porewater by co precipitation with and or adsorption to fe sulfides the concentrations of tl removed from or added to sediments after their deposition i e diagenetic tl amount to up to 36 of measured sediment tl concentrations comparison of the reconstructed historical tl records with those of polycyclic aromatic hydrocarbons pahs and of pb originating from coal burning or from smelting activities indicate that coal combustion is the major source of atmospheric tl to l tantare and that an additional important tl source to l vose is the nearby smelter

late quaternary hydroclimatology of a hyper arid andean watershed climate change floods and hydrologic responses to the el nino southern oscillation in the atacama desert abstract although certain characteristics of the el nino southern oscillation enso are well known on contemporary timescales less is known about the magnitude frequency relationships of this atmospheric phenomenon on longer timescales or its relationship to widespread flooding especially in its core zone along the sub tropical andes where la nina or el nino episodes control regional hydroclimatology using a combination of stratigraphic evidence geochronologic dating 14c and osl stable isotope analyses and water geochemistry along the rio moquegua in the northern fringes of the atacama desert we assemble a paleoflood chronology for mainstem and tributary sections for the past ca 20 ka and ascertain the variation in enso frequency and magnitude because of the inherent watershed structure and regional hydroclimatology mid valley tributaries of the rio moquegua only flood during el nino episodes and thus provide an important proxy of extreme el ninos while mainstem stratigraphy records both la nina and el nino episodes el nino floods appear to have been pronounced during the late pleistocene and up to at least the younger dryas 12 000 cal yr bp while stratigraphic evidence of large el nino floods is lacking in tributary systems during the mid holocene flood stratigraphy in a 2 ka 7 m high terrace along the mainstem indicates an increased frequency and magnitude of large floods between ca 700 and 1610 ad as compared to the period from ca 160 bce to 700 ad with mega ninos occurring ca 1330 ad and ca 1650 ad water geochemistry and radiocarbon dating indicate that at least two major aquifers exist with wells and springs in the mid valley dating to 710 and 3100 14c yr bp respectively while water from a spring in the headwaters dates to 10 320 14c yr bp this range in dates suggests that groundwater flow in the mid valley is neither fossil water nor exclusively recharged from local precipitation while the older date for headwater sections suggests a more fossil groundwater source and lack of contemporary recharge the 18o similarity between groundwater in the mid valley and the regional meteoric water line mwl suggests a pacific moisture source and the role of el nino precipitation in recharging local aquifers thus el ninos and pacific sourced moisture are an important component of the regional hydroclimatology and the variation in enso frequency and intensity has significant social and hydrologic repercussions in these hyper arid settings

buried palaeosols of the nevado de toluca an alternative record of late quaternary environmental change in central mexico buried palaeosols of central mexico not previously analysed from a palaeopedological standpoint have helped to develop a reliable regional model of late quaternary climatic change this paper focuses upon morphological and micromorphological properties particle size distribution and extractable fe al and si of seven palaeosols named pt1 pt7 in the vicinity of the nevado de toluca volcano the characteristics of andic cambisol pt1 similar to those of modern soils in semi arid environments indicate a drier climate in the first half of the holocene humic andosols pt2 pt4 are analogous to modern volcanic soils of humid forest environments they show evidence that a moist palaeoclimate prevailed during marine oxygen isotope stages ois 2 and 3 luvisols pt5 and pt6 which are assumed to have formed at the end of marine ois 5 to marine ois 4 also indicate humid conditions we attribute the differences between andosols pt2 pt4 and luvisols pt5 pt7 to variations in the duration in the pedogenesis rather than to changes in palaeoclimate micromorphological features of andosol to luvisol transition confirm that these soils form an evolutionary sequence being for the most part consistent with lacustrine records the palaeosol properties do not reflect the episodes of drier climate during the last glacial maximum however as shown by diatom and palynological data from lake sediments mesoclimate variations and or incompleteness of soil memory reflecting mostly periods of humid pedogenesis probably provide the reason for this disagreement copyright 2001 john wiley sons ltd

palynological and magnetic susceptibility records of lake chalco central mexico abstract pollen and magnetic susceptibility data from a 11 27 m long core drilled in the central part of lake chalco 99 00 w 19 15 n located at the southeastern part of the basin of mexico are interpreted in terms of paleoenvironmental changes the record of this subtropical highland lake dated by radiocarbon methods spans approximately 24 000 yr b p and documents changes in climate vegetation lake level and volcanic activity seven palynozones were established by using the method of cluster analysis for correlation purposes zones 7 6 and 5 between 20 600 and 18 300 yr b p indicate reduced forests with extensive grasslands relatively high input of sediments by water discharge of surface streams and high lake level the evidences obtained in zone 4 between 18 300 and 17 500 yr b p suggest a dry and warm climate with xerophytic vegetation lower lake level and erosion rates zone 3 between 17 500 and 10 000 yr b p shows a trend to increasing moisture and cooler temperatures volcanic activity during this period is intense and strongly influences the natural environments at around 12 000 yr b p a clear expansion of forests and fulfillment of the lake recorded at the beginning of the holocene an oak forest expansion and a lowering of lake levels are initiated and by the mid holocene zone 2 subhumid temperate conditions are detected although lake level continues to be low the human impact is recorded in the last 4000 yr

weathering and soil forming processes under semi arid conditions in two mexican volcanic ash soils abstract weathering and neoformation of allophane imogolite and halloysite in volcanic ash soils have been studied extensively in humid climates but little data are available on these soils in arid and semi arid conditions weathering and soil formation under semi arid conditions on acid pyroclastics have been investigated in two profiles both at the micro site scale and on bulk samples xr microdiffractions and sem edx microanalysis were performed on soil thin sections chemical particle size xrd and mineral identification analysis were performed on conventional soil samples results show the interplay of various sub processes a intense division of the coarse minerals into small fragments 50 200 m in size b diagenesis of noncrystalline products in the zone of contact with the parent minerals c transformation of noncrystalline minerals into halloysite in the compact soil microstructures and preservation of the noncrystalline minerals in the topsoil d desiccation and condensation of the crystalline and noncrystalline minerals into microaggregates in the topsoil the results of these interacting weathering processes are silty loam soils with no cohesion and high susceptibility to wind erosion differences appearing between different analytical methods at different sampling scales need special precautions in explaining the results

organic matter mineralization in sediment of a coastal freshwater lake and response to salinization solid phase and pore water chemical data collected in a sediment of the haringvliet lake are interpreted using a multi component reactive transport model this freshwater lake which was formed as the result of a river impoundment along the southwestern coast of the netherlands is currently targeted for restoration of estuarine conditions the model is used to assess the present day biogeochemical dynamics in the sediment and to forecast possible changes in organic carbon mineralization pathways and associated redox reactions upon salinization of the bottom waters model results indicate that oxic degradation 55 denitrification 21 and sulfate reduction 17 are currently the main organic carbon degradation pathways in the upper 30 cm of sediment unlike in many other freshwater sediments methanogenesis is a relatively minor carbon mineralization pathway 5 because of significant supply of soluble electron acceptors from the well mixed bottom waters although ascorbate reducible fe iii mineral phases are present throughout the upper 30 cm of sediment the contribution of dissimilatory iron reduction to overall sediment metabolism is negligible sensitivity analyses show that bioirrigation and bioturbation are important processes controlling the distribution of organic carbon degradation over the different pathways model simulations indicate that sulfate reduction would rapidly suppress methanogenesis upon seawater intrusion in the haringvliet and could lead to significant changes in the sediment s solid state iron speciation the changes in fe speciation would take place on time scales of 20 100 years

andosol to luvisol evolution in central mexico timing mechanisms and environmental setting abstract surface and buried andosols and buried luvisols of the nevado de toluca late quaternary tephra paleosol sequence central mexico were studied to show whether these soils present an evolutionary sequence and to determine the pedogenic mechanisms and environmental factors involved in the evolutionary process micromorphological observations and mineralogical composition of fine sand and clay fractions were used to detect type and succession of soil forming process some of the buried andosols defined as intergrade andosols have a predominantly blocky structure humus depleted areas redoximorphic features and thin clay coatings in ah horizons clay fractions of buried andosols contain halloysite besides amorphous components whereas in modern andosols allophane is dominant luvisols have micro areas with granular structure and abundant phytoliths in the groundmass of bt horizons assumed to be the relict andosol features luvisol clay fractions are dominated by halloysite and kaolinite primary minerals show micromorphological weathering features in all studied soils being stronger in luvisols however even in luvisols sand fractions consist mostly of unstable volcanic silicates we hypothesise that the studied profiles form an evolutionary sequence andosols intergrade andosols luvisols the soil transformation is supposed to be linked to progressive crystallisation of 1 1 clay minerals comparing the nevado de toluca paleosol properties with the existing data on volcanic soil climo and chronesequences and assessing the regional paleopedological and lacustrine records of quaternary paleoclimates we concluded that wet dry climatic oscillations took place during the formation of the studied paleosols rapid crystallisation of 1 1 minerals occurred during dry phases which speeded up the andosol to luvisol transformation and made it independent from the primary mineral weathering status the andosol to luvisol transformation accelerated by climatic fluctuations is thought to be a common soil evolutionary pathway in the subtropical and tropical regions of recent volcanism which suffered contrasting precipitation oscillations in the quaternary

indications of pedogenesis in lower pleistocene tool bearing sediments in northern armenia and regional paleoclimatic reconstruction abstract indications of the early pleistocene paleopedogenesis were analyzed in multilevel sections of pedosediments at early acheulian sites within the lori plateau in northern armenia with the purpose of reconstructing the paleoclimatic conditions during the initial stage of early human occupation of this region at the study sites lithic tools typical of the acheulian technocomplex dating back to 1 4 1 9 ma were found the sections of studied pedosediments were shown to contain material from former paleosols that developed higher up the slope then were eroded and transported by colluvial processes presumably during catastrophic events and finally redeposided in an inverted order at the foot of the slope three evolutionary stages of lower pleistocene paleosols were identified which allow for paleoclimatic reconstruction of the initial stages of early human occupation of this region in the earliest chronointerval 1 9 1 77 ma vertic cambisols and colluvic regosols humic developed in the region in savanna like landscapes under sub tropical climatic conditions towards the end of this period 1 77 ma the climatic conditions remained sub tropical but became more humid with the development of stagnic cambisols and andosols with an abundance of redoximorphic features during the latest period studied between 1 77 and 1 4 1 5 ma the development of luvisols indicates a stronger leaching environment under a permanently humid climate with significant cooling early hominin communities had to adapt to the cooler environment to be able to continue their uninterrupted development into the middle pleistocene

simulation of the asian summer monsoons of 1987 and 1988 with a regional model nested in a global gcm state of the art general circulation models have deficiencies in simulating the observed amplitude and phase of the mean patterns of circulation and precipitation over the asian monsoon region they are also deficient in simulating the observed seasonal variations of circulation and precipitation averaged over the monsoon region to improve these simulations the national centers for environmental prediction regional eta model is nested in the center for ocean land atmosphere studies cola gcm the eta model is a gridpoint model with a horizontal resolution of 80 km and 38 layers in the vertical the eta model domain 30 8 1408e 308s 508n covers the asian monsoon region which includes the indian chinese and southeast asian monsoons the cola gcm is a sigma coordinate spectral model with rhomboidal truncation at 40 waves and 18 vertical levels the eta model is nested in the gcm such that its lateral boundary conditions and initial conditions are derived

spatial variability of environment change in the teotihuacan valley during the late quaternary paleopedological inferences the teotihuacan valley mexico has been the object of considerable interest because of its importance in the context of human history in america although archeological research has been extensively conducted to understand causes of the decline of teotihuacan culture no sufficient scientific evidence has been provided this paper is focused on paleopedological evidence especially properties that constitute soil memory in order to reconstruct the spatial distribution of environment variability during the late pleistocene and holocene three profiles that include modern soils and buried paleosols were studied in different geomorphic positions uplands cerro gordo site cg lower talus slope transition to valley bottom maseca ma and the mouth of the valley at the ancient border of the former texcoco lake this last site is near tepexpan te where some of the oldest human remains in mexico were recovered the oldest paleosol is at cg at 3000 m a s l it is dated at 22 000 yr bp and exhibits a truncated profile with a very well developed bt horizon dominated by kaolinite with phytoliths of c3 plants all of its features are related to a humid probably warm environment it was classified as a luvisol this paleosol is buried by another luvisol dated at 13 000 yr bp with morphological characteristics similar to the previous soil although clay mineralogy consists mostly of halloysite and a higher percentage of c4 plant phytoliths is apparent in ma the oldest paleosol was not recognized it is probable that the two paleosols found in cg merge into one at ma which shows strong redoximorphic features but high percentages of c4 plant phytoliths and halloysitic clays at the te site paleosols are less developed fluvisols modern soil cover also varies in relation to its geomorphic position in cg it is a phaeozem while in ma and te present day soils have carbonate accumulation we interpret prevailing conditions during the last glacial maximum in the teotihuacan valley to be humid with a tendency towards drying at the end of pleistocene dry conditions prevail in the valley today

the step mountain coordinate model description and performance for cases of alpine lee cyclogenesis and for a case of an appalachian redevelopment abstract the problem of the pressure gradient force error in the case of the terrain following sigma coordinate does not appear to have a solution the problem is not one of truncation error in the calculation of space derivatives involved thus with temperature profiles resulting in large errors an increase in vertical resolution may not reduce and is even likely to increase the error therefore an approach abandoning the sigma system has been proposed it involves the use of step mountains with coordinate surfaces prescribed to remain at fixed elevations at places where they touch and define or intersect the ground surface thus the coordinate surfaces are quasi horizontal and the sigma system problem is not present at the same time the simplicity of the sigma system is maintained in this paper design of the model silhouette averaged mountains properties of the wall boundary condition and the scheme for calculation of the potential to kinetic energy conversion are presented for an

mineral and organic components of the buried paleosols of the nevado de toluca central mexico as indicators of paleoenvironments and soil evolution abstract results of earlier studies of quaternary tephra paleosol sequences in central mexico revealed contradictions between paleopedological and lacustrine records to settle the contradictions selected quantitative characteristics of mineral and organic components of the paleosols pt1 pt7 from the nevado de toluca sequence were studied as independent paleoclimate proxies mineralogical composition of sand and clay fractions allows assessment of weathering and secondary mineral formation both being climate dependent processes stable carbon isotope ratios of humus and phytolith morphology indicate paleovegetation in all paleosols the sand fractions consist mainly of unstable volcanogenic minerals although the grains have weathering features short durations of pedogenesis are responsible for limited weathering status the clay fraction is dominated by halloysite and dehydrated halloysite in units pt1 pt4 which suggests drier periods during paleosol formation whereas major amounts of kaolinite in the units pt5 pt7 indicate extended humid pedogenesis 13c values of pt2 pt4 humus are intermediate between those characteristic of c3 and c4 plants phytolith assemblages which include both forms of c3 dominant and c4 minor quantities grasses agree with carbon isotope data these data indicate plant cover changes driven by wet dry paleoclimate oscillations the new results showing drier stages during the formation of late pleistocene paleosols pt2 and pt3 correct the primary interpretation of these units as indicating only humid pedogenesis and settles the contradiction between paleopedological and lacustrine records

lgm summer climate on the southern margin of the laurentide ice sheet wet or dry abstract regional climate simulations are conducted using the polar fifth generation pennsylvania state university psu ncar mesoscale model mm5 with a 60 km horizontal resolution domain over north america to explore the summer climate of the last glacial maximum lgm 21 000 calendar years ago when much of the continent was covered by the laurentide ice sheet lis output from a tailored ncar community climate model version 3 ccm3 simulation of the lgm climate is used to provide the initial and lateral boundary conditions for polar mm5 lgm boundary conditions include continental ice sheets appropriate orbital forcing reduced co2 concentration paleovegetation modified sea surface temperatures and lowered sea level the simulated lgm summer climate is characterized by a pronounced low level thermal gradient along the southern margin of the lis resulting from the juxtaposition of the cold ice sheet and adjacent warm ice free land surface this sharp thermal gradient anchors the midtropospheric

a micromorphological study of pedogenic processes in an evolutionary soil sequence formed on late quaternary rhyolitic tephra deposits north island new zealand abstract the influence of time as a soil forming factor was studied on an evolutionary sequence of five soils 1850 radiocarbo years bp ca 120 000 bp developed in rhyolitic tephra deposits in new zealand new micromorphological observations were combined with existing macromorphological chemical textural and clay mineralogical analyses to assess the extent of polygenesis in the soils the younger soils 1850 bp to ca 22 600 bp are characterised by initial weathering and little secondary mineral formation this status is expressed by abundant pumice fragments and fresh easily weatherable minerals as well as a low clay content with an isotropic character comminution and neoformation are the main pedological processes the older soils ca 120 000 bp are characterised by a high degree of alteration of primary minerals little or no pumice fragments clay illuviation gleying and a high clay content 80 consisting of a range of crystalline clay minerals including halloysite gibbsite kaolinite and vermiculite plus crystalline iron oxides evidence of polygenesis can be observed in the micromorphology of the older soils 1 the range of secondary minerals is the result of the integration and succession of soil forming processes through time 2 the accumulatory character of the tephra deposits has resulted in stronger weathering of the lower horizons than upper horizons because of continuous pedogenesis such polygenesis in the older soils supports the view that the older the soil the more polygenetic it is likely to be

testing soil fertility of prehispanic terraces at viejo sangayaico in the upper ica catchment of south central highland peru abstract this study presents a pilot geoarchaeological investigation of terraced agricultural systems near san francisco de sangayaico in the upper ica catchment of the southern peruvian andes it aims to assess the evidence for soil fertility associated with agricultural strategies practised throughout the prehispanic spanish colonial and modern occupations in this region a series of twenty two test pits were hand excavated through two terraced field systems and sampled to examine the changes in soil physical and chemical characteristics down profile and downslope this study provides the first geoarchaeological analyses of the agrarian soil system surrounding viejo sangayaico in the upper ica catchment results demonstrate that the soil system was much modified prior to the creation of the terrace systems probably about 900 years ago this system was characterised by a weakly acidic to slightly calcareous ph a consistent but low electrical conductivity reasonable but variable phosphorus content and a loamy soil texture with a component of weathered volcanic tonalite parent material the shallow terrace soil build up on the slopes investigated indicates that slope modification was as minimal as possible moreover the relatively low frequencies of organic material and phosphorus suggest that the terraces were not heavily fertilised in the past making the stability and management of the nutrient rich topsoil vital the results of these excavations and soil fertility analyses are situated within the context of the wider andean ethno historic and the archaeological record to address questions regarding how the terraces were built and maintained over time agricultural terraces undoubtedly mitigated the effects of slope erosion associated with cultivation but the terrace soil features observed at sangayaico do not appear to be the same as those documented in other geoarchaeological studies of andean terrace systems these contrasts may be accounted for by a combination of differing geological substrate and hydrological conditions as well as variable trajectories in past soil development erosion factors manuring field management practises and crop selection

soil formation in a quaternary terrace sequence of the allier limagne france macro and micromorphology particle size distribution chemistry abstract soil formation in a terrace chronosequence of nine gravelly quaternary terraces was studied based on macro and micromorphological mineralogical chemical and physical characteristics based on textural characteristics the c horizon of the youngest soil appears to be representative for the parent material of lower b and c horizons in the youngest soils and of all horizons in older soils the parent materials contain a volcanic and a granitic component with increasing age of soils the following stages of soil formation were observed holocene soils on lowest terraces show evidence for mixing of sedimentary layers by biological activity resulting in texturally homogeneous a and b horizons in the absence of periglacial processes soil formation in holocene and in late pleistocene terraces took place under continuously well drained conditions late pleistocene soils on higher terraces show effects of clay illuviation with prominent weathering features in a horizons middle and early pleistocene soils on the highest terraces were influenced by periglacial conditions and display effects of various cycles of soil forming processes alternated with periglacial processes increasing in complexity with age weathering of all minerals except quartz neoformation of clay and clay illuviation has resulted in distinct differentiation between sandy a and e horizons and a clayey b horizon periglacial processes during the quaternary weathering clay formation and clay illuviation have caused a considerable compaction and decreased water permeability this has resulted in imperfect drainage now reflected by abundant locally cemented iron and manganese oxide segregations in the surface horizon typical for surface water gley with evidence of ferrolysis ferrolysis the increased weathering of clay under influence of alternating oxidation reduction in the seasonally waterlogged surface soil may have further contributed to the marked textural change between a and e versus b horizons easily weatherable minerals observed in strongly leached surface layers of older end members of the terrace sequence might be attributed to aeolian volcanic inputs the holocene and late pleistocene soils are intensively used as arable land as a result of the continuously well drained conditions on account of the poor drainage the middle and early pleistocene soils are used mainly for grassland and forest

soil organic carbon stocks and forest productivity in volcanic ash soils of different age 1835 30 500 years b p in mexico abstract volcanic soils have a large potential for organic carbon storage and for forest growth in particular under moist temperate climate documenting both potentials may offer incentives for forest conservation and exploitation and for the allocation of bonds for environmental services we studied sites on lava flows of different ages 1835 4200 6200 8000 10 000 and 30 500 years b p covered by volcanic ashes within the sierra del chichinautzin volcanic field under pine or fir forest we analyzed the accumulation of organic carbon in the soils and its relation with the evolution of site quality forest productivity indicators and c storage in tree biomass we also studied the relation between soil c accumulation and different soil properties as soil ph clay contents and pyrophosphate extractable al and oxalate extractable al and si contents results show that carbon accumulation in the soil increases linearly with age within 1835 and 10 000 years old sites with a mean accumulation rate of 4 33 kg m 2 each 1000 years however between 10 000 and 30 500 years the amount of c stored decreases again by about 30 of the maximum soil c accumulation during the first 8000 years of the chronosequence site quality improves with soil development tree growth indexes approach stabilization at sites of ages between 10 000 and 30 500 years adult pine trees reach an accumulation of 27 kg c per tree each year during the first 10 000 years carbon accumulation in mineral surface horizons is associated with the formation of al bearing organo mineral complexes characterized by pyrophosphate extractions which seem to compete with the neoformation of short range order clay minerals as clay and al oxide formation progresses these soil variables contribute also to stabilize soil c although they are by far not as efficient as the organo mineral complexes

palaeoclimatic and archaeological evidence for a 200 yr recurrence of floods and droughts linking california mesoamerica and south america over the past 2000 years conspicuous grey clay rich flood deposits in the predominantly olive varved sediment in the central santa barbara basin california were dated via varve counting to c ad 212 440 603 1029 1418 and 1605 the 200 yr quasi periodicity and the timing of individual floods match time periods of known supraregional climatic changes and the documented 200 yr periodicity in palaeoclimate records elsewhere the floods of c ad 440 and ad 1418 occurred during global reorganizations of atmospheric circulation cold spells seem to have accompanied the floods of c ad 1029 and ad 1605 california floods and other palaeoclimate records suggest that expressions of regional climates are modulated by solar variability with a 200 yr periodicity our compilation of palaeoclimatic and mesoamerican and south american archaeological records provides evidence that palaeoenvironmental and cultural changes were often coincident within their respective dating uncertainties and occurred in 200 yr steps the matching patte

geomorphological study of the cafayate dune field northwest argentina during the last millennium abstract the cafayate depression is a dry valley located in the pre andean region of northwest argentina the area shows the development of a large dune field its significance has been established from geomorphological and mineralogical evidence grain shape characteristics and chronological data osl dating archaeological remains and historical data the dating results were between 1000 1100 ad to1740 1830 ad showing that the aeolian dynamics remained active during the last millennium it was not possible to identify stabilised phases marked by ruptures or paleosol development nevertheless other regional and local proxies from northwest argentina archaeological documentary etc were used to complete the interpretative framework to propose the paleoenvironmental evolution of the area in addition human activity and land use must be considered as a complementary factor affecting aeolian dynamics during the most recent stage