cosmogenic nuclide chronology of millennial scale glacial advances during o isotope stage 2 in patagonia the terrestrial glacial record reflects past snowline variability and atmospheric temperature changes when combined with secure chronologies these data can be used to test models of ice age climate we present new in situ cosmogenic 1 0 be 2 6 al and 3 he exposure ages supported by limiting 4 0 ar 3 9 ar and 1 4 c ages for seven of the youngest moraines east of lago buenos aires argentina 46 5 s that were deposited by a large outlet glacier of the patagonian ice cap following a major glaciation that deposited extensive moraines prior to 109 ka paired 1 0 be 2 6 al ages indicate that the next youngest complex of moraines was deposited from 23 0 1 2 to 15 6 1 1 ka 1 during the last glaciation ice was at its maximum extent prior to 22 ka and at least five moraines were deposited in less than 10 k y these data are in good agreement with three 1 4 c ages of ca 16 ka from varved sediment banked on top of the youngest of these five moraines and limiting 3 he ages which range from ca 33 to 19 ka the most extensive ice marginal deposits preserved within the last 109 k y were formed during marine oxygen isotope stage 2 no moraines dating to stage 4 were found for stage 2 the distribution of ages at lago buenos aires is similar to cosmogenic nuclide based glacial chronologies from western north america in fact the structure of the last mid latitude south american ice age specifically the overall timing a maximum ice extent prior to 22 ka and deglaciation after 16 ka is indistinguishable from that of the last major glaciation in the northern hemisphere despite a maximum in southern hemisphere insolation during this period the similar mid latitude glacial history in both hemispheres implies that a global climate forcing mechanism such as atmospheric cooling as opposed to oceanic redistribution of heat synchronizes the ice age climate on orbital time scales

extensive mountain glaciation in central patagonia during marine isotope stage 5 abstract the timing and magnitude of glacial advances throughout a glacial cycle can give insight on the underlying drivers of climate change our knowledge of glacial activity early in a glacial cycle however is limited by incomplete preservation of the geomorphological record here we present a b 10 e dated glacial chronology from early in the last glacial cycle from the belgrano valley east of monte san lorenzo in central patagonia our chronology reveals the most extensive glacial advance of the last glacial cycle occurred at 75 ka at the end of marine isotope stage 5 a second less extensive advance occurred at 25 ka during the global last glacial maximum the topographic setting is such that ice growth would have initiated on and around the san lorenzo massif at the start of the glacial cycle we suggest reduced southern hemisphere summer insolation at the time played a significant role in driving this early advance the comparatively smaller glacier extent during the global last glacial maximum is likely a consequence of the build up of the full patagonian ice sheet which would have caused ice divide migration ice flow re routing and increased aridity on its lee side

origin and significance of calcium carbonate in soils of southwestern patagonia abstract a soil chronosequence spanning the last 0 76 1 0 ma shows a progressive increase in calcium carbonates based on 1 thickness of the bk bck horizons 2 maximum carbonate stage 3 profile accumulation of pedogenic carbonates and 4 mass flux of ca from a geochemical mass balance we favor a dust origin of the carbonates because 1 the till parent materials contain low amounts of caco3 2 there is minimal evidence for weathering of ca bearing minerals in the soil 3 the amount of caco3 in the profile is far in excess of what could be released by weathering 4 dust collected from the study area is enriched in caco3 and 5 a source area for the carbonates was identified although there likely were changes in dust deposition rates during the quaternary our calculations suggest that the current deposition rate of 0 18 g caco3 m 2 yr 1 is comparable to the long term profile accumulation rate of 0 16 g caco3 m 2 yr 1 230th u disequilibrium ages of carbonate pendants are consistent with cosmogenic surface exposure ages indicating that this method has potential for dating other geomorphic surfaces in patagonia cryogenic processes have affected many of the pedons particularly during the last glacial maximum

the last glaciation in central magellan strait southernmost chile abstract glacial landforms and drift stratigraphy in central magellan strait southernmost chile document repeated fluctuations during the last glacial cycle of outlet lobes from an ice cap centered over the southern andes the lobes developed comparatively low gradient profiles because of low basal shear stresses over soft deformable beds and this made them sensitive to even small scale changes in the mass balance such low profiles and rapid calving in deep proglacial lakes during deglaciation may have made the magellan ice lobe particularly responsive to climatic fluctuations during the last glacial cycle and to advance and retreat over considerable distances study of the glacial landforms and drift stratigraphy has led to the identification of at least five glacier advances to limits at and south of the segunda angostura fragments of mollusc shells contained in basal till indicate marine incursions between some advances thus documenting extensive deglaciation a partial chronology based on amino acid studies and radiocarbon dating suggests that five of these advances occurred during the last glacial cycle the most extensive advances may have culminated during substages of marine isotope stage 5 substage 5b or 5d and or during stage 4 slightly less extensive advances occurred between ca 28 000 and 14 000 yr b p

reply to vogt s comments on the paper fibrous clay mineral formation and soil evolution in aridisols of northeastern patagonia argentina by p j bouza m simon j aguilar h del valle and m rostagno

late holocene climatic fluctuations and soil genesis in southern patagonia effects on the archaeological record geoarchaeological research conducted at five localities in southern patagonia and tierra del fuego identified a mollisol within late holocene aeolian and colluvial deposits associated with archaeological material the mollisol s origin and development are related to an increase in humidity c 1000 bp following an episode of severe drought during the medieval warm period corroborating data is supplied from dendroclimatic and pollen studies a drastic reduction in frequency of artefact distribution recorded at the sites studied corresponds to this pedologic event suggesting a greater human presence at these sites during earlier regional scale arid conditions however the paucity of archaeological remains may also be the result of the low resolution of cultural evidence following the pedologic development due to superimposition over previous archaeological deposits

two step deglaciation at the oxygen isotope stage 6 5e transition the zeifen kattegat climate oscillation comparison of marine lacustrine and terrestrial records from twenty four sites suggests the existence of a younger dryas type climate oscillation just prior to the oxygen isotope stage 6 5e boundary these records include results from biostratigraphic pedostratigraphic and speleothem studies as well as analyses of stable isotope compositions of marine records and ice cores the climate oscillation is named after the warm zeifen interstadial and the cold kattegat stadial the zeifen interstadial may be related to a major meltwater pulse in the baffin bay labrador sea norwegian sea region the climate oscillation is presumably in part a result of a variation in ocean circulation especially in the strength of the north atlantic drift but changes in the atmospheric circulation also played an important role the geographically widespread distribution of the oscillation suggests that the two step deglaciation influenced both the northern and southern hemispheres c 1996 elsevier science ltd

the kamikatsura event in the gold hill loess alaska 1 as part of a broader geological study of loess palaesol sequences in alaska the paleomagnetism of a section at gold hill near fairbanks has been investigated samples were collected at 5 cm intervals through a 5 m loess paleosol loess sequence detailed alternating field demagnetization of the natural remanent magnetization yields excellent results average mad 2 the brunhes matuyama b m polarity transition is present at the level of the paleosol which was formedduringoxygenisotopestage19 asystematicperturbation in both declination and inclination occurs 1 0 1 5 m belowtheb mboundary thecorrespondingvirtualgeomagnetic poles define a track centred on the 60 w meridian from high southerly to equatorial latitudes and back again this is in very good agreement with results from a sequence of lava flows on the island of maui that are regarded as a record of the kamikatsura event the alaskan results thus confirm the reality of this geomagnetic feature and simultaneously provide a firm chronological control point for ongoing geological investigations mineral magnetic experiments indicate that the remanence of the gold hill loess is dominated by magnetite and or maghemite with no subsequent chemical overprinting by hematite and or goethite citation evans m e b j l jensen v a kravchinsky and d g froese 2011 the kamikatsura event in the gold hill loess alaska geophys res lett 38 l13302 doi 10 1029 2011gl047793

glaciations in patagonia and tierra del fuego during the ensenadan stage age early pleistocene earliest middle pleistocene while the ensenadan stage age ca 2 1 to 0 5 ma was characterized by certain mammal associations in the pampean plains the andean ranges of patagonia and tierra del fuego their piedmont areas and in some cases the adjacent lowlands were undergoing a well defined alternating sequence of glacial and interglacial stages driven by the regional climate of southernmost south america and antarctica this paper reviews the available geographical geological and chronological evidence of glaciation during the ensenadan stage age with perhaps more than 15 distinct glacial events including the great patagonian glaciation gpg and other cold episodes that took place before and after it finally a tentative correlation of patagonian glacial episodes and the pampean biostratigraphic stages based on radiometric dating and paleomagnetic studies is herein presented

stratigraphy and palaeoclimatic significance of late quaternary loess palaeosol sequences of the last interglacial glacial cycle in central alaska abstract loess is one of the most widespread subaerial deposits in alaska and adjacent yukon territory and may have a history that goes back 3 ma based on mineralogy and major and trace element chemistry central alaskan loess has a composition that is distinctive from other loess bodies of the world although it is quartz dominated central alaskan loess was probably derived from a variety of rock types including granites metabasalts and schists detailed stratigraphic data and pedologic criteria indicate that contrary to early studies many palaeosols are present in central alaskan loess sections the buried soils indicate that loess sedimentation was episodic or at least rates of deposition decreased to the point where pedogenesis could keep ahead of aeolian input as in china loess deposition and pedogenesis are likely competing processes and neither stops completely during either phase of the loess soil formation cycle loess deposition in central alaska took place before and probably during the last interglacial period during stadials of the mid wisconsin period during the last glacial period and during the holocene an unexpected result of our geochronological studies is that only moderate loess deposition took place during the last glacial period our studies lead us to conclude that vegetation plays a key role in loess accumulation in alaska factors favouring loess production are enhanced during glacial periods but factors that favour loess accumulation are diminished during glacial periods the most important of these is vegetation boreal forest serves as an effective loess trap but sparsely distributed herb tundra does not thus thick accumulations of loess should not be expected where tundra vegetation was dominant and this is borne out by modern studies near the treeline in central alaska much of the stratigraphic diversity of north american loess including that found in the central lowlands the great plains and alaska is explained by a new model that emphasizes the relative importance of loess production factors versus loess accumulation factors

global changes in intensity of the earth s magnetic field during the past 800kyr recent advances in palaeomagnetic and dating techniques have led to increasingly precise records of the relative intensity of the earth s past magnetic field at numerous field sites the compilation and analysis of these records can provide important constraints on changes in global magnetic field intensity and therefore on the earth s geodynamo itself a previous compilation for the past 200 kyr integrated 17 marine records into a composite curve1 with the geomagnetic origin of the signal supported by an independent analysis of 10be production made on different cores2 the persistence of long term features in the earth s magnetic intensity or the existence of long term periodic changes cannot however be resolved in this relatively short time span here we present the integration of 33 records of relative palaeointensity3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 into a composite curve spanning the past 800 kyr we find that the intensity of the earth s dipole field has experienced large amplitude variations over this time period with pronounced intensity minima coinciding with known excursions in field direction reflecting the emergence of non dipole components no stable periodicity was found in our composite record and therefore our data set does not support the hypothesis that the earth s orbital parameters have a direct and strong influence on the geodynamo

upper level structure of oklahoma tornadic storms on 2 may 1979 i radar and satellite observations abstract this paper discusses the observational characteristics of the upper level structure of severe tornadic storms in oklahoma on 2 may 1979 during sesame the data analyzed consist of limited scan goes east and west visible infrared 11 m and stereo satellite data dual doppler radar observations and special storm scale soundings the time histories of stereo cloud top height minimum equivalent blackbody temperature tbb and radar reflectivity are followed for three severe storms over a several hour period two of the storms are tornadic cloud top ir growth rates and vertical velocities of the storms are computed and found to have maxima which fall into adler and fenn s severe storm classification for one of the storms there is an interesting coupling between cloud top parameters and low level radar echoes the other tornadic storm showed no unique relationship hail damage began shortly after tropopause penetration by thee storms two major ir cold areas associated with the leading downwind

characterisation of transport processes and sedimentary deposits by statistical end member mixing analysis of terrestrial sediments in the donggi cona lake catchment ne tibetan plateau abstract unmixing of grain size distributions with multivariate statistical analysis gives indications of the main sediment transport processes and related environmental conditions in an area we performed end member mixing analysis emma of sedimentological data from 912 terrestrial sediment samples collected in the donggi cona catchment north eastern tibetan plateau up to the present this is the largest sedimentological dataset on the tibetan plateau emma resulted in the characterisation of three end members that explain 88 of the variance within the dataset the end members all represent aeolian deposits the first end member em 1 represents very fine dune sediments that were deflated from a former lake system em 2 represents medium sand deposits that were blown out from playa and alluvial fan sediments em 3 represents fine loess like sediments mainly found at higher elevations different transformations adding of a fourth end member and adding of up to 200 loess samples do not change the composition of the end members demonstrating the robustness of the model emma allows the synchronous interpretation of very large datasets resulting in a general characterisation of sediment transport in a particular area performing emma on the dataset demonstrates the importance of aeolian transport in this part of the world

mid latitude trans pacific reconstructions and comparisons of coupled glacial interglacial climate cycles based on soil stratigraphy of cover beds abstract south westland new zealand and southern chile are two narrow continental corridors effectively confined between the pacific ocean in the west and high mountain ranges in the east which impart significant influence over regional climate vegetation and soils in both these southern mid latitude regions evidence for extensive and repeated glaciations during cold phases of the quaternary is manifested by arrays of successively older glacial drift deposits with corresponding outwash plain remnants in south westland these variably aged glacial landforms are mantled by layered multisequal soils characterised by slow loess accretion and pedogenesis in an extreme leaching and weathering environment these cover bed successions have undergone repeated coupled phases of topdown and upbuilding soil formation that have been related to fluctuating cycles of interglacial warm and glacial cold climate during the quaternary in this study we recognise multisequal soils overlying glacial landforms in southern continental chile but unlike the spodic podzolic soil sequences of south westland these are of dominantly volcanigenic andic provenance and are very similar to multisequal soils of andic provenance that predominate in and adjacent to areas of rhyolitic to andesitic volcanism in north island new zealand here we develop a soil stratigraphic model to explain the observed occurrence of multisequal soils mantling dominantly glacial landforms of southern continental chile based on proxy data from southern chile we propose that persistent vegetation cover and high precipitation on the western side of the andes during colder than present episodes tended to suppress the widespread production of glacially derived loessial materials despite the pervasive occurrence of glacial and glacio fluvial deposits that have frequently inundated large tracts of this landscape during the quaternary given the lack of loess cover beds that have traditionally assisted in the relative dating of glacial episodes prior to the late quaternary surface exposure dating techniques could provide another chronological alternative to address this issue however there have been two main obstacles to successfully apply this dating technique in patagonia first minimum exposure ages may be obtained on moraines older than the last glacial cycle due to erosion although dating outwash plains is more robust second on the wet western side adjacent to the andes persistent vegetation cover during both glacial and post glacial times as well as widespread inundation by volcanic mass flows appear preventive we make a case that soil genesis within this region appears to be dominated by a constant flux of intermittently erupted andean sourced tephra which has continued to upbuild soils at the ground surface separated by intervals where topdown weathering processes are intensified as already demonstrated by new zealand studies multisequal soil successions have a clear implied connection to coupled glacial and interglacial climate cycles of the quaternary on this basis similar sequences in northwest patagonia provide a relatively untapped archive to enable quaternary glacial and environmental changes in this pervasively glaciated volcanic region to be constructed

pleistocene climates in china dated by magnetic susceptibility the magnetic susceptibility of loess and interbedded soils in central china varies with the degree of pedogenesis and serves as a proxy measure of climate the concentration of magnetic minerals in the sediment is inversely proportional to sedimentation rates throughout the brunhes epoch susceptibility measurements combined with the reversal stratigraphy provide a time scale that is independent of astronomic chronology on this scale the susceptibility record closely parallels the oxygen isotope fluctuations in deep sea sediments suggesting a close interdependence of the chinese dust falls the volume of land based ice and global climate

150 000 years of loess accumulation in central alaska abstract the halfway house site in interior alaska is arguably the most studied loess deposit in northwestern north america the site contains a complex paleomagnetic and paleoenvironmental record but has lacked the robust chronologic control that would allow its full potential to be exploited detailed reexamination of stratigraphy paleomagnetics and tephrostratigraphy reveals a relatively complete marine isotope stage mis 6 to holocene record constrained by the old crow 124 10 ka vt 106 10 ka sheep creek klondike ca 80 ka dominion creek 77 8 ka and dawson ca 30 2 cal ka bp tephras we show two well developed paleosols formed during marine isotope stages mis 5e and 5a while mis 5c and 5b are either poorly represented or absent the new tephrostratigraphy presented here is the most complete one to date for the late pleistocene and indicates mis 5 sediments are more common than previously recognized a magnetic excursion within the sediments is identified as the post blake excursion 94 1 7 8 ka providing independent age control and adding to the increasing body of evidence that alaskan loess is a detailed recorder of variations of the earth s magnetic field over time a high resolution magnetic susceptibility profile placed into this new chronostratigraphic framework supports the hypothesis that wind intensity is the main variable controlling fluctuations in susceptibility correlation of the susceptibility record to global marine 18o records is complicated by highly variable accumulation rates we find the lowest rates of accumulation during peak warm and cold stages while abrupt increases are associated with periods of transition between marine isotope sub stages building on previous accumulation models for alaska surface roughness is likely a leading variable controlling loess accumulation rates during transitions and peak cold periods but the negligible accumulation during mis 5e and 5a suggests that loess production was exceedingly low negating the role of surface roughness this interplay of variables leads to optimal conditions for loess accumulation during transitions between isotope stages and to a somewhat lesser extent stadials and interstadials

40ar 39ar and k ar chronology of pleistocene glaciations in patagonia during the pleistocene east of lago buenos aires argentina at 46 5 s at least 19 terminal moraines were deposited as piedmont glaciers from the patagonian ice cap advanced onto the semi arid high plains adjacent to the southern andes exceptional preservation of these deposits offers a rare opportunity to document ice cap fluctuations during the last 1 2 m y 4 0 ar 3 9 ar incremental heating and unspiked k ar experiments on four basaltic lava flows interbedded with the moraines provide a chronologic framework for the entire glacial sequence the 4 0 ar 3 9 ar isochron ages of three lavas that overlie till 90 km east of the cordillera at lago buenos aires and another 120 km from the andes along rio gallegos at 51 8 s that underlies till strongly suggest that the ice cap reached its greatest eastward extent ca 1100 ka at least six moraines were deposited within the 256 k y period bracketed by basaltic eruptions at 1016 10 ka and 760 14 ka similarly six younger more proximal moraines were deposited during an 651 k y period bracketed by an underlying 760 14 ka basalt and the 109 3 ka cerro volcan basalt flow that buried all six moraines coupled with in situ cosmogenic surface exposure ages of moraine boulders the 109 ka age of cerro volcan implies that moraines deposited during the penultimate local glaciation correspond to marine oxygen isotope stage 6 further westward toward lago buenos aires six additional moraines younger than the cerro volcan basalt flow occur surface exposure dating of boulders on these moraines combined with the 1 4 c age of overlying varved lacustrine sediment indicates deposition during the last glacial maximum lgm 23 16 ka although antarctic dust records signal an important patagonian glaciation at 60 40 ka moraines corresponding to marine oxygen isotope stage 4 are not preserved at lago buenos aires apparently these were overrun and obliterated by the younger ice advance at 23 ka notwithstanding the overall pattern of glaciation in patagonia is one of diminishing eastward extent of ice during successive glacial advances over the past 1 m y we hypothesize that tectonically driven uplift of the patagonian andes which began in the pliocene yet continued into the quaternary in part due to subduction of the chile rise spreading center during the past 2 m y maximized the ice accumulation area and ice extent by 1 1 ma subsequent deep glacial erosion has reduced the accumulation area resulting in less extensive glaciers over time

environmental assessment of 1991 hudson volcano eruption ashfall effects on southern patagonia region argentina the august 1991 eruption of the hudson volcano in the southern andean volcanic zone affected an area of 1000 km in radius to the east in the argentine patagonic meseta the thickness of ash ranged from 20 cm in the andean area to less than 1 mm in the atlantic coast zone wind storms reactivated the ash deposits together with terrigenous material more than one year after the eruption in order to assess the potential risk of the ash analyses of concentration size mineralogical composition toxic elements and irritating effects of gases were performed in all samples the percentage of particles of the 2 to 5 m range is below the toxic threshold level trace elements are below the toxic threshold concentration for humans and animals the major impact of the ashfall was on sheep herds about one third of them were lost in the areas close to the volcano soil incorporated the ash layers and a fast recovery of orchards was reported two years later rivers were loaded with sediment in the immediate aftermath but one year later returned to previous conditions along the shores of the buenos aires lake a fresh tephra layer can be distinguished

the vesicular layer and carbonate collars of desert soils and pavements formation age and relation to climate change abstract the vesicular fine grained a horizon av is the widespread ubiquitous surficial horizon of desert soils in diverse landforms and parent materials of varying ages now known to form mostly through accumulation of eolian dust recent studies show that dust accumulation and concomitant soil development are genetically linked to stone pavement formation changes in the magnitude of eolian activity and effective leaching related to quaternary climatic changes are also hypothesized to have influenced the evolution of the av horizon numerical modeling geochronologic and field laboratory studies elucidate the nature of pedogenic processes controlling compositional evolution of av how the changing av horizon increasingly influences soil infiltration and carbonate translocation and accumulation and the control that clasts of the evolving pavement exert on pedogenic processes results of a model that determines soil bulk chemical composition based on mixing of estimated proportions of externally derived eolian material and parent materials imply that the evolution of the soil bulk composition is strongly influenced by av horizon formation the early development of a weakly to moderately developed av horizon directly over gravelly parent material in late and middle holocene soils moderately influences soil infiltration but significant leaching of very soluble materials and some carbonate in dust are permitted in older pleistocene soils however the texturally more mature av and underlying cumulic nongravelly horizons more strongly limit the rate and depth of leaching and soil bulk composition therefore more closely approximates a simple mixture of dust and parent material other aspects of av horizon development and its relations to the pavement are evaluated through studies of pavement clasts with coatings of soil carbonate referred to as carbonate collars development of a numerical model that integrates soil hydrology a co2 production diffusion model calcite kinetics and thermodynamic considerations composition and thermal characteristics of pavement clasts and the textural and structural properties of the surface horizon provides the basis for testing a hypothesis of collar formation model results combined with results of 13c and 18o analyses of collar carbonate demonstrate how precipitation of calcite on pavement clasts and within the av is favored at a depth much shallower than that indicated by the classic carbonate depth climate relationship of jenny and leonard jenny h j leonard c d 1935 functional relationships between soil properties and rainfall soil science 38 363 381 and arkley arkley r j 1963 calculations of carbonate and water movement in soil from climatic data soil science 96 239 248 or simulated by numerical models of carbonate accumulation simultaneous development of thick carbonate collars and the av horizon requires the sustained pavement clast av horizon coupling for at least centuries to possibly millennia new thermoluminescence ages also indicate that much of the av horizon formed in the holocene and that it is certainly much younger than the older pleistocene pavements this supports the previously proposed hypothesis that increased dust flux during the pleistocene to holocene transition triggered and or greatly accelerated av horizon development an understanding of the genesis of collars provides not just an understanding of how carbonate can accumulate in surface environments but it also provides important clues into processes of pavement evolution and preservation of av horizons during long glacial periods the av horizon is not merely an insignificant surficial zone of recent dust accretion instead its development profoundly influences the genesis of desert soils and pavements

quaternary soils and dust deposition in southern nevada and california eoliandustconstitutesmuchofthepedogenic material in late pleistocene and holocene soils of many arid regions of the world comparisonofthecompositionsand influx rates of modern dust with the eolian component of dated soils at 24 sites in southern nevada and california yields informationon 1 thecompositionandinflux rate of dust in late pleistocene and holocene soils 2 paleoclimate and its effects on the genesis of aridic soils especially with regard to dustfall events 3 the timing and relative contribution of dust from playa sources versus alluvial sources and 4 the effects of accumulation of dust in soil horizons the 2mmfractionsofaandbhorizons of soils formed on gravelly alluvial fan deposits in the study area are similar to moderndustingrainsize contentofcaco3and salt majoroxides andclaymineralogy thus they are interpreted to consist largely of dust the major oxide compositions of the shallow soil horizons are nearly identical to that of the modern dust but the compositions of progressively deeper horizons approachthatoftheparentmaterial theclay mineralogyofmoderndustatagivensiteis similar to that of the av horizons of nearby holocene soils but is commonly different from the mineralogies of deeper soil horizonsandoftheavhorizonsofnearbypleistocenesoils theseresultsareinterpretedto indicate that dust both accumulates and is transformed in av horizons with time changes in soil accumulation rates provide insights into the interplay of paleoclimate dustsupply andsoil formingprocesses modern dust deposition rates are more than large enough to account for middle and late holocene soil accumulation rates at nearly all sites however the early holocene soil accumulation rates in areas near late pleistocene pluvial lakes are much higher than modern rates and clearly indicate a dust deflation and deposition event that caused rapid formation offine grained shallow soil horizons on uppermost pleistocene and lower holocene deposits we interpret late pleistocene soil accumulation rates to indicate that dust deposition rates were low during this period but that increased effective moisture during the late wisconsinan favored translocation of clay andcaco3fromnearthesurfacetodeeper inthesoilprofile pre latepleistocenerates are very low in most areas mainly due to a pedogenic threshold that was crossed when accumulations of silt clay and caco3 began to inhibit the downward transport of eolian material but in part due to erosion

cosmogenic nuclide chronology of pre last glacial maximum moraines at lago buenos aires 46 s argentina at lago buenos aires argentina 10 be 26 al and 40 ar 39 ar ages range from 190 000 to 109 000 yr for two moraines deposited prior to the last glaciation 23 000 16 000 yr ago two approaches maximum boulder ages assuming no erosion and the average age of all boulders and an erosion rate of 1 4 mm 10 3 yr both yield a common estimate age of 150 000 140 000 yr for the two moraines the erosion rate estimate derives from 10 be and 26 al concentrations in old erratics deposited on moraines that are n760 000 yr old on the basis of interbedded 40 ar 39 ar dated lavas the new cosmogenic ages indicate that a major glaciation during marine oxygen isotope stage 6 occurred in the mid latitude andes the next five youngest moraines correspond to stage 2 there is no preserved record of a glacial advance during stage 4 the distribution of dated boulders and their ages suggest that at least one major glaciation occurred between 760 000 and n200 000 yr ago the mid latitude patagonian glacial record which is well preserved because of low erosion rates indicates that during the last two glacial cycles major glaciations in the southern andes have been in phase with growth and decay of northern hemisphere ice sheets especially at the 100 000 yr periodicity thus glacial maxima are global in nature and are ultimately paced by small changes in northern hemisphere insolation d 2005 university of washington all rights reserved

lake level stratigraphy and geochronology revisited at lago lake cardiel argentina and changes in the southern hemispheric westerlies over the last 25 ka abstract paleoshorelines around lago lake cardiel in southern argentina s48 9 w71 3 275 m record substantial changes in lake area over the past 25 ka our results combined with previous research show that during the last glacial maximum or lgm 23 21 ka the lake stood at near modern levels but had nearly dried up by 13 ka between 11 3 and 10 1 ka the lake reached its highest point 54 58 m and greatest extent in at least the last 40 ka lake levels dropped thereafter and experienced two lower lake periods 8 5 7 5 ka and 5 3 3 ka and two higher lake periods 7 4 6 and 5 2 ka in the last 3 5 ka the lake has remained generally near or slightly above its present level the depth and surface area of lago cardiel are controlled mainly by precipitation onto the lake and surrounding catchment air and water temperature and wind speed related to local strength of the southern hemispheric westerlies shw our lake level reconstruction combined with evidence from other studies suggest that on average the core of the shw was located well to the north 55 s during the hydrologic maximum of cardiel in the early holocene the lower phases of the lake at 20 0 11 5 8 5 7 5 and 5 0 3 3 ka generally correspond to cold conditions in other records when we infer that the shw were strongly focused around the latitudes of cardiel at 49 s

early stage development of selected soil properties along the proglacial moraines of skaftafellsjokull glacier se iceland abstract soil development was studied along a chronosequence in 2010 in a proglacial environment in se iceland we investigated morphological physical chemical and mineralogical changes in the soil representing over 120 year period in total 54 sampling sites were distributed along three moraines deposited in 1890 1945 and 2003 for comparison samples were collected from a nearby downy birch betula pubescens ehrh forest representing soils in a mature ecosystem likely to establish on the moraines in the future after 120 years since deglaciation and formation of ac horizon sequence bulk density decreased from 1 36 g cm 3 to 1 07 g cm 3 concentrations of soil organic carbon soc and total nitrogen n increased with time from being zero up to 1 77 of soc and 0 10 of n soil ph h2o declined rapidly and was the only soil property that attained a steady state compared to that under the birch forest the concentration of oxalate extractable al and fe increased over time although at a slower rate of change compared to that for other soil properties freshly exposed moraines contained a considerable amount of the extractable elements indicating a relative abundance of poorly crystalline al and fe phases in the subglacial moraines the data support the conclusion that after 120 years of soil formation proglacial soils are still young and may yet need one or two centuries to develop properties typical of well drained volcanic soils

soil development along primary succession sequences on moraines of hailuogou glacier gongga mountain sichuan china abstract soil properties related to soil development were measured in six profiles over approximately 180 years of soil development on recessional moraines of the hailuogou glacier sichuan of southwestern china it is hypothesized that soil development is strictly time dependent field and laboratory work indicate that as soil develops from initially coarse gravel outwash the properties undergo a progressive physical and chemical change such that there is a considerable profile differentiation between the youngest and the oldest soils the ph is also highly stratified it decreases with time from 8 5 to 4 2 in the upper mineral soil and increases with depth in all profiles accumulation of soil organic c and n increases with time but the rates of accumulation become slower with time within the investigated timespan soil c and n accumulated to a considerable level of 3 5 and 0 6 kg m2 respectively with mean annual rates of 28 g m2 for carbon and 3 5 g m2 for nitrogen the rapid accumulation of organic c and n accelerates the processes of soil formation but the content of organic c and n did not reach a steady state during the observed timespan the accumulation of soil organic matter results in increased acid production and in the chemical weathering of minerals that promote formation and translocation of the clay fraction and leaching of carbonate it is also directly responsible for development of soil properties such as cation exchange capacity cec and bulk density

effects of climate change on soils in glacial deposits wind river basin wyoming abstract soil chronofunctions are often quasilinear but those relationships may be only gross fortuitous generalizations that ignore changes in soils resulting from climatic and other cyclic external influences that govern soil formation or soil degradation in the rocky mountains soil development has been extensively used to estimate the age of sediments but the number of soils is usually few and large ranges in values for soil data may be dismissed as normal variation in a detailed study of soils in the wind river range and wind river basin characteristics of near surface horizons do not follow age trends however the underlying carbonate bearing horizons do have age related characteristics this soil paradox may be related to glacial interglacial cycles in which 1 wind erodes near surface horizons and then provides new parent material and 2 cryoturbation disrupts carbonate horizons remobilizing carbonate and changing carbonate morphology but with only minimal loss of carbonate from the soil

loess of southern south america abstract loess and loessoid loess like reworked loess sediments extend across the chaco pampean plains and the nw mountain environments of argentina and in neighbouring countries paraguay brazil uruguay bolivia loessoid sediments are much more abundant than primary loess the beginning of the loessoid sedimentation cycle was related to a phase of late miocene orogeny in the andes the plio pleistocene record is mostly composed of loessoid sediments modified by pedogenesis which produced welded palaeosols the late pleistocene holocene loess record reveals a heterogeneous composition across the region coarse textures and an andean derived volcanic composition prevail in the southern pampas finer textures and material coming from the andes and the other two sources sierras pampeanas and the parana basin characterize the loess deposits of the northern pampas and the eastern chaco a southern patagonian source is also suggested for the mountain valley loess of tucuman although a western andean provenance has been proposed it is believed that the material in the western chaco was derived from the bolivian andes loess deposition was related to a multistage transport mechanism involving fluvial and aeolian processes inferred westerly and southwesterly wind directions as dominant carriers of the aeolian deposits are in agreement with westerly palaeowind simulations using climate models however the role played by westerly tropospheric winds and northerly winds remains to be established

odp site 1063 bermuda rise revisited oxygen isotopes excursions and paleointensity in the brunhes chron an age model for the brunhes chron of ocean drilling program odp site 1063 bermuda rise is constructed by tandem correlation of oxygen isotope and relative paleointensity data to calibrated reference templates four intervals in the brunhes chron where paleomagnetic inclinations are negative for both u channel samples and discrete samples are correlated to the following magnetic excursions with site 1063 ages in brackets laschamp 41 ka blake 116 ka iceland basin 190 ka pringle falls 239 ka these ages are consistent with current age estimates for three of these excursions but not for pringle falls which has an apparent age older than a recently published estimate by 28 kyr for each of these excursions termed category 1 excursions virtual geomagnetic poles vgps reach high southerly latitudes implying paired polarity reversals of the earth s main dipole field that apparently occurred in a brief time span 2 kyr in each case several times shorter than the apparent duration of regular polarity transitions in addition several intervals of low paleomagnetic inclination low and negative in one case are observed both in u channel and discrete samples at 318 ka mis 9 412 ka mis 11 and in the 500 600 ka interval mis 14 15 these category 2 excursions may constitute inadequately recorded category 1 excursions or high amplitude secular variation

soil forming rates and processes on quaternary moraines near lago buenos aires argentina thirty four pedons on four moraine groups spanning the last 1 myr are used to investigate mechanisms and rates of soil development in santa cruz province argentina all soils are coarse loamy mesic typic haplocalcids or calcic haploxerolls occurring under short grass shrub steppe in a semi arid climate the dominant soil forming processes are the accumulation of organic matter carbonate and clay sized particles organic carbon accumulates rapidly in these soils but significantly higher amounts in the oldest two moraine groups are likely the result of slight differences in soil forming environment or grazing practices accumulation rates of carbonate and clay decrease with age suggesting either decreased influx in the earliest part of the record or attainment of equilibrium between influx and loss there are no changes in soil redness and preservation of weatherable minerals in the oldest soils indicates there is little chemical weathering in this environment measured dust input explains the accumulation of both clay and carbonate we present a carbonate cycling model that describes potential sources and calcium mobility in this environment calibration of rates of soil formation creates a powerful correlation tool for comparing other glacial deposits in argentina to the well dated moraines at lago buenos aires

regional mid pleistocene glaciation in central patagonia abstract southern south america contains a glacial geomorphological record that spans the past million years and has the potential to provide palaeoclimate information for several glacial periods in earth s history in central patagonia two major outlet glaciers of the former patagonian ice sheet carved deep basins 50 km wide and extending over 100 km into the andean plain east of the mountain front a succession of nested glacial moraines offers the possibility of determining when the ice lobes advanced and whether such advances occurred synchronously the existing chronology which was obtained using different methods in each valley indicates the penultimate moraines differ in age by a full glacial cycle here we test this hypothesis further using a uniform methodology that combines cosmogenic nuclide ages from moraine boulders moraine cobbles and outwash cobbles 10 be concentrations in eighteen outwash cobbles from the moreno outwash terrace in the lago buenos aires valley yield surface exposure ages of 169 269 ka we find 10 be inheritance is low and therefore use the oldest surface cobbles to date the deposit at 260 270 ka which is indistinguishable from the age obtained in the neighbouring lago pueyrredon valley this suggests a regionally significant glaciation during marine isotope stage 8 and broad interhemispheric synchrony of glacial maxima during the mid to late pleistocene finally we find the dated outwash terrace is 70 100 ka older than the associated moraines on the basis of geomorphological observations we suggest this difference can be explained by exhumation of moraine boulders