impact of volcanic processes on the cryospheric system of the peteroa volcano andes of southern mendoza argentina abstract soil temperatures of the active volcanic complex peteroa situated in the cordillera principal between chile and argentina at 35 15 s and 70 35 w approximately were monitored in the area and local geomorphology periglacial geomorphology presence of permafrost and cryoforms was studied the present contribution also resulted in a comparison of two consecutive analyses of the volcano peak carried out with special thermocameras agema tvh 550 fur p660 in order to study the thermal range of different hot and cold sites selected in 2009 the thermocameras were used ascending by foot and also during flights with a cessna 180 a night expedition to the volcanic avalanche caldera at up to 3900 m asl approximately completed the monitoring activity of 2010 hot zones were associated to present volcanism and cold zones to the presence of glacier ice and shadowy slopes with possible presence of permafrost identifying and mapping uncovered and covered ice was possible with the help of monitoring and geomorphological interpretation related to the upper englacement which is severely affected by volcanism glaciers are retreating toward the north or approaching the rims of the volcanic avalanche caldera leaving islands of ice associated with superficial permafrost the cryogenic area with slope permafrost was identified through active protalus and sedimentary cryogenic slopes craters have undergone considerable thermal changes in comparison to the year 2009 and new much more vigorous fumaroles have appeared in hot areas detected in 2009 following a tendency toward the west new subaquatic heat columns that appeared in crater 3 crater walls and glaciated areas vanished supplying cold water and thus contributing to the formation of a new lake in crater 4 a possible post seismic shift of the volcanic activity may provide geodynamical evidence of the changes registered in other areas after the earthquake of 27 february 2010

quantifying regional groundwater flow between continental intercalaire and djeffara aquifers in southern tunisia using isotope methods large scale interaction between the continental intercalaire and the djeffara aquifer systems in the southeast of tunisia has been investigated with the aid of chemical and isotopic tracers two distinct groundwater types have been identified 1 the continental intercalaire groundwater characterized by elevated temperatures 50 61 4 c low 18o 8 4 to 7 87 and 2h 67 2 to 59 values and negligible radiocarbon content both testifying its great age dating from the late pleistocene period and 2 the djeffara groundwater with distinctly heavier isotopic composition 18o 8 31 to 5 80 2h 65 9 to 31 9 the djeffara groundwaters reveal a distinct changes of physico chemical and isotopic parameters near el hamma faults in the northwestern part of the djeffara basin these changes could possibly be explained by a vertical leakage from the continental intercalaire aquifer through el hamma faults the mixing proportions inferred from stable isotope mass balance prove that the contribution of the continental intercalaire to the recharge of djeffara aquifer is very significant and may reach 100 in the el hamma region and in the northern part of gabes isotope tracers strongly suggest that recent recharge to the djeffara aquifer system is very limited its current yield particularly in its central and northern parts can be maintained only thanks to large scale underground inflow from the continental intercalaire aquifer system which carries late pleistocene palaeowater consequently current exploitation of groundwater resources of the djeffara aquifer has non sustainable character

volcano ice interactions precursory to the 2009 eruption of redoubt volcano alaska abstract in late summer of 2008 after nearly 20 years of quiescence redoubt volcano began to show signs of abnormal heat flow in its summit crater in the months that followed the excess heat triggered melting and ablation of redoubt s glaciers beginning at the summit and propagating to lower elevations as the unrest accelerated a variety of morphological changes were observed including the creation of ice cauldrons areas of wide spread subsidence punctures in the ice carved out by steam and deposition from debris flows in this paper we use visual observations satellite data and a high resolution digital elevation model of the volcanic edifice to calculate ice loss at redoubt as a function of time our aim is to establish from this time series a proxy for heat flow that can be compared to other data sets collected along the same time interval our study area consists of the drift glacier which flows from the summit crater down the volcano s north slope and makes up about one quarter of redoubt s total ice volume of 4 km 3 the upper part of the drift glacier covers the area of recent volcanism making this part of ice mass most susceptible to the effect of volcanic heating moreover melt water and other flows are channeled down the drift glacier drainage by topography leaving the remainder of redoubt s ice mantle relatively unaffected the rate of ice loss averaged around 0 1 m 3 s over the last four months of 2008 accelerated to over twenty times this value by february 2009 and peaked at greater than 22 m 3 s just prior to the first major explosion on march 22 2009 we estimate a cumulative ice loss over this period of about 35 million cubic meters m m 3

holocene lake level trends in the rocky mountains u s a abstract the availability of water shapes life in the western united states and much of the water in the region originates in the rocky mountains few studies however have explicitly examined the history of water levels in the rocky mountains during the holocene here we examine the past levels of three lakes near the continental divide in montana and colorado to reconstruct holocene moisture trends using transects of sediment cores and sub surface geophysical profiles from each lake we find that mid holocene shorelines in the small lakes 4 110 ha were as much as 10 m below the modern lake surfaces our results are consistent with existing evidence from other lakes and show that a wide range of settings in the region were much drier than today before 3000 2000 years ago we also discuss evidence for millennial scale moisture variation including an abruptly initiated and terminated wet period in colorado from 4400 to 3700 cal yr bp and find only limited evidence for low lake stands during the past millennium the extent of low water levels during the mid holocene which were most severe and widespread ca 7000 4500 cal yr bp is consistent with the extent of insolation induced aridity in previously published regional climate model simulations like the simulations the lake data provide no evidence for enhanced zonal flow during the mid holocene which has been invoked to explain enhanced mid continent aridity at the time the data including widespread evidence for large changes on orbital time scales and for more limited changes during the last millennium confirm the ability of large boundary condition changes to push western water supplies beyond the range of recent natural variability

shallow magma transport for the 2002 3 mt etna eruption inferred from thermal infrared surveys abstract the 26 october 2002 28 january 2003 eruption of mt etna volcano was characterised by lava effusion and by an uncommon explosivity along a 1 km long eruptive fissure on the southern upper flank of the volcano the intense activity promoted rapid growth of cinder cones and several effusive vents analysis of thermal images recorded throughout the eruption allowed investigation of the distribution of vents along the eruptive fissure and of the nature of explosive activity the spatial and temporal distribution of active vents revealed phases of dike intrusion expansion geometric stabilization and drainage these phases were characterised by different styles of explosive activity with a gradual transition from fire fountaining through transitional phases to mild strombolian activity and ending with non explosive lava effusion here we interpret the mechanisms of the dike emplacement and the eruptive dynamics according to changes in the eruptive style vent morphology and apparent temperature variations at vents detected through thermal imaging this is the first time that dike emplacement and eruptive activity have been tracked using a handheld thermal camera and we believe that its use was crucial to gain a detailed understanding of the eruptive event

late quaternary environmental change in the bonneville basin western usa abstract excavation and analyses of small animal remains from stratified raptor deposits spanning the last 11 5 ka together with collection and analysis of over 60 dated fossil woodrat midden samples spanning the last 50 ka provide a detailed record of changing climate in the eastern great basin during the late pleistocene and holocene sagebrush steppe dominated the northern bonneville basin during the full glacial suggesting that conditions were cold and relatively dry in contrast to the southern basin which was also cold but moister limber pine woodlands dominated 13 11 5 ka indicating increased dryness and summer temperatures 6 7 c cooler than present this drying trend accelerated after 11 5 ka causing lake bonneville to drop rapidly eliminating 11 species of fish from the lake from 11 5 8 2 ka xerophytic sagebrush and shadscale scrub replaced more mesophilic shrubs in a step wise fashion a variety of small mammals and plants indicate the early holocene was 3 c cooler and moister than at present not warmer as suggested by a number of climatic models the diversity of plants and animals changed dramatically after 8 2 ka as many species disappeared from the record some of the upland species returned after 4 ka and great salt lake became fresh enough at 3 4 and 1 2 ka to support populations of utah chub

birth growth and morphologic evolution of the laghetto cinder cone during the 2001 etna eruption we have undertaken detailed observations of the formation of the laghetto cinder cone a new cone that formed during a 2 week period of intense activity in piano del lago on the upper slopes of mount etna in summer 2001 we describe the events leading to the formation of a small graben the formation of pit craters on the base of the graben the onset of phreatomagmatic activity a transition to intense strombolian activity and a return to phreatomagmatic activity as the eruption came to an end we discuss the reasons for these transitions and describe the morphological development of the cone during these events arcuate cracks on the southern part of the cone were related to withdrawal of magma at the end of the eruption other slope instabilities that developed during the eruption include the formation of small radial grain flows on the outer flanks of the cone and the collapse into the crater of part of the crater rim some of the failure planes we observed were first identified using a flir tm 695 thermal infrared camera this is the first time that infrared thermography has been used to detect instability of volcanic structures results obtained during this test case demonstrate that thermal cameras are a very useful tool for studies of volcanic instability

a paleotemperature record derived from dissolved noble gases in groundwater of the aquia aquifer maryland usa low 14c activities in groundwater of the confined part of the aquia aquifer in southeastern maryland suggest that most of this water infiltrated at least 30 000 years ago however radiocarbon contents of the dissolved inorganic carbon seem to be affected by isotopic exchange possibly with secondary calcite deposits in the formation leading to overestimated 14c ages whereas the geochemistry of the aquia aquifer complicates the application of the widely used 14c dating method the accumulation of radiogenic he seems to provide a viable alternative for establishing a chronology the quasi linear increase of he concentrations with flow distance observed in the aquia aquifer can be explained entirely by accumulation of in situ produced radiogenic he u and th concentrations in aquia sand were measured in order to determine the accumulation rate of 4he with sufficient confidence to establish a he time scale concentrations of dissolved atmospheric noble gases were used to derive mean annual ground temperatures at the time of infiltration these noble gas temperatures ngts clearly show the presence of water that infiltrated under much cooler conditions than at present ngts are correlated with chloride concentrations corroborating the hypothesis that chloride variations in this aquifer constitute a climate signal in contrast the stable isotope ratios 180 and d do not provide a clear record of past climatic changes in the aquia aquifer and the correlation between ngts and stable isotope ratios is weak the ngt record suggests that mean annual temperatures in this midlatitude coastal site during the last glacial maximum lgm were 9 0 0 6 c colder than during the holocene this difference is slightly lower than estimates derived from pollen data for this region but considerably larger than the rather uniform cooling of about 5 c indicated by noble gas studies in more southern locations of north america the larger cooling is ascribed to the influence of the laurentide ice sheet which at its maximum extension came as close as 250 km to our study site

holocene fire occurrence and alluvial responses at the leading edge of pinyon juniper migration in the northern great basin usa abstract fire and vegetation records at the city of rocks national reserve ciro south central idaho display the interaction of changing climate fire and vegetation along the migrating front of single leaf pinyon pinus monophylla and utah juniper juniperus osteosperma radiocarbon dating of alluvial charcoal reconstructed local fire occurrence and geomorphic response and fossil woodrat neotoma middens revealed pinyon and juniper arrivals fire peaks occurred 10 700 9500 7200 6700 2400 2000 850 700 and 550 400 cal yr bp whereas 9500 7200 6700 4700 and 1500 1000 cal yr bp are fire free wetter climates and denser vegetation fueled episodic fires and debris flows during the early and late holocene whereas drier climates and reduced vegetation caused frequent sheetflooding during the mid holocene increased fires during the wetter and more variable late holocene suggest variable climate and adequate fuels augment fires at ciro utah juniper and single leaf pinyon colonized ciro by 3800 and 2800 cal yr bp respectively though pinyon did not expand broadly until 700 cal yr bp increased fire related deposition coincided with regional droughts and pinyon infilling 850 700 and 550 400 cal yr bp early and late holocene vegetation change probably played a major role in accelerated fire activity which may be sustained into the future due to pinyon juniper densification and cheatgrass invasion

deciphering interaction of regional aquifers in southern tunisia using hydrochemistry and isotopic tools groundwater is the most important source of water supply in southern tunisia previous hydrogeologic and isotopic studies carried out in this region revealed the existence of two major aquifer systems the complex terminal ct and the continental intercalaire ci turonian carbonates constitute one of the major aquifer levels of the ct multilayered aquifer it extends over most of southern tunisia and its hydrodynamic regime is largely influenced by tectonics lithology and recharge conditions forty eight groundwater samples from the ci and turonian aquifers were collected between january and april 2004 for chemical and isotopic analyses hydrochemistry and isotopic tools were combined to get an insight into the processes controlling chemical composition of groundwater and wide scale interaction of these two aquifer systems analysis of the dissolved constituents revealed that several processes control the observed chemical composition i incongruent dissolution of carbonate minerals ii dissolution of evaporitic minerals and iii cation exchange dissolution alone cannot account for the observed high supersaturation states of groundwater with respect to calcite and dolomite the observed supersaturation is most probably linked to geogenic co2 entering water bearing horizons of the ct and ci aquifers via deep tectonic faults and discontinuities and subsequent degassing in the exploitation wells presence of geogenic co2 in the investigated region was confirmed by c isotope data of the dic reservoir the radiocarbon content of the turonian samples varied between 9 5 and 43 pmc for ci samples generally lower values were recorded between 3 8 and 22 5 pmc stable isotope composition of turonian groundwater samples varied from 8 3 to 5 3 for d 18 o and from 60 to 25 for d 2 h the corresponding ranges of d values for the continental intercalaire samples were from 8 9 to 6 9 for d 18 o and from 68 2 to 45 7 for d 2 h stable isotope composition of groundwater representing ct and ci aquifers

origin of the groundwater salinity and geochemical processes in detrital and carbonate aquifers case of chougafiya basin central tunisia summary comprehensive investigations of groundwaters were performed in the detrital and carbonate aquifers of the chougafiya basin central tunisia in the present review hydrochemistry and isotopic tools were combined to get an insight into the processes controlling mineralization recharge conditions flow pattern of groundwater and c chemistry in the investigated hydrological system analysis of the dissolved constituents revealed that several processes controlled the observed chemical composition i the dissolution of evaporitic minerals ii cation exchange reactions iii sulfate reduction under anaerobic conditions iv incongruent dissolution of carbonate minerals calcite dolomite coupled with gypsum dissolution and calcite precipitation and v silicates weathering data inferred from 18o and deuterium isotopes in groundwater samples indicated recharge with modern rainfall water characterized by lower 18o and 2h values is interpreted as recharged by non evaporated rainfall originating from mediterranean and atlantic air masses however water with relatively enriched 18o and 2h contents is thought to reflect the occurrence of an evaporation process related to the long term practice of flood irrigation the radiogenic 3h isotope data provided insight into the presence of two recharge periods in the investigated groundwaters waters with 3h contents of 1 tu clearly suggested the occurrence of a contemporaneous recharge probably during the last two decades carbon isotopes provided some insights into the timescales of groundwater flow but mainly revealed that main sources of c are active in the system these are likely dissolved biogenic co2 carbonate dissolution and incongruent reaction of the carbonate matrix mean residence times were determined after correction of the initial activities for dead c from the rock matrix and suggest ages ranging from the present day to the holocene in both upper cretaceous and mio pliocene groundwaters

geochemistry of the active azufre planchon peteroa volcanic complex chile 35 15 s evidence for multiple sources and processes in a cordilleran arc magmatic system

geochemistry and14c dating of groundwaters from jurassic aquifers of north aquitaine basin france twenty seven samples from a confined lower middle jurassic aquifer and an unconfined oxfordian aquifer of the north aquitaine basin france have been analysed for their major elements br 18o 2h 13c and14c contents hydrochemistry indicates 1 a dissolution of carbonate and anhydrite near the recharge zone and 2 a dilution of a saline water derived from a seawater halite mixing in the deeper part of the aquifer the mixing is also visible in a 18o vs cl diagram in which two different groups appear recent waters and old waters indicating a mixing process between fresh and saline groundwaters the composition of the saline water is likely to be 34 100 11 200 ppm in cl 70 20 ppm in br and more than 3 5 07 vs smow in18o 13c contents indicate 1 a c exchange with caco3 matrix for groundwaters near the recharge zone and 2 a participation of organic matter in the deep part of the aquifer residence times for waters near the area of the aquifer outcrop correspond to holocene and late pleistocene periods the depletion in stable isotopes of 10 to 15 000 y b p waters show a late glacial period infiltration to the aquifer after a distance of about 10 km in the aquifer the14c activities are 0 pmc showing the presence of old groundwaters

combining ash analyses with remote sensing to identify juvenile magma involvement and fragmentation mechanisms during the 2018 19 small eruption of peteroa volcano southern andes abstract the planchon peteroa volcanic complex ppvc is located on the border of chile and argentina and is one of the most active volcanic systems in the andes holocene activity has included magma water interaction with an evolving series of crater lakes mainly sourced from peteroa volcano this study examines data from the 2018 19 eruption together with the volcanic history of the ppvc to elucidate the complex interplay between magmatic activity and summit water and ice from february 2016 to mid 2019 three seismic swarms occurred in the ppvc preceding the explosive eruption from september 2018 to april 2019 the activity originated from a small vent nested within the easternmost crater the most active portion of the complex peteroa the explosions interacted with a crater lake producing ash plumes up to 2 km above the crater and building a small tephra cone to investigate the eruption mechanisms we performed remote sensing analysis of plume dispersal thermal anomalies and ground deformation and characterized the volcanic products including grain size componentry morphology internal textures composition and mineralogy our results suggest that the precursory seismicity beginning in 2016 was related to the intrusion of a new magma batch that reached the surface during the 2018 19 eruption the eruption was also preceded by thermal anomalies geomorphic changes and increased hydrothermal activity at the surface though without any ground deformation recognized through radar interferometry insar the eruption initially produced predominantly recycled ash phreatic activity then evolved to increasing proportions of juvenile magma phreatomagmatic by april 2019 the juvenile clasts had a trachyandesite composition 59 wt sio2 with vesicular and dense scoria containing plagioclase and pyroxene the ash surfaces show external quenching cracks and step fractures consistent with phreatomagmatic fragmentation within the active crater lake textural characteristics also point to a slowly ascending batch of magma that was relatively viscous by the time it interacted with water in the crater lake notably these juvenile particles are distinctive from the pre 2018 products ash erupted from 2010 11 did not contain recognizable juvenile material and is inferred to have been a mainly phreatic eruption our findings suggest that the interplay between phreatic and phreatomagmatic eruptions fed by small magma batches intruding at shallow levels characterize much of the eruptive behavior of the ppvc during the last three decades multi parametric assessment is a powerful tool to discriminate between phreatic and phreatomagmatic eruptions

variations in fire frequency and climate over the past 17 000 yr in central yellowstone national park a 17000 yr fire history from yellowstone national park demonstrates a strong link between changes in climate and variations in fire frequency on millennial time scales the fire history reconstruction is based on a detailed charcoal stratigraphy from cygnet lake in the rhyolite plateau region macroscopic charcoal particles were tallied from contiguous 1 cm samples of a 6 69 m long core and the data were converted to charcoal accumulation rates at evenly spaced time intervals intervals of high charcoal accumulation rates were interpreted as local fire events on the basis of information obtained from modern charcoal calibration studies in the yellowstone region the record indicates that fire frequency was moderate 4 fires 1000 yr during the late glacial period reached highest values in the early holocene 10 fires 1000 yr and decreased after 7000 calendar yr b p the present fire regime 2 3 fires 1000 yr was established in the past 2000 yr the charcoal stratigraphy correlates well with variations in july insolation through time which suggests that regional climate changes are responsible for the long term variations in fire frequency in the early holocene summer insolation was near its maximum which resulted in warmer effectively drier conditions throughout the northwestern united states at this time the fire frequency near cygnet lake was at its highest after 7000 calendar yr b p summer insolation decreased to present values the regional climate became cooler and wetter and fires were less frequent the cygnet lake record suggests that long term fire frequencies have varied continuously with climate change even when the vegetation has remained constant

the little ice age glacier advance in the central andes 35 s argentina abstract this paper documents the occurrence of the little ice age lia in the el azufre and el penon glaciers at 35 s and in the las choicas and las damas glaciers at 34 55 s in the headwaters of the rio grande basin in the central andes of argentina moraine morphology stratigraphic relationships radiocarbon ages obtained from peat on these glacial deposits and the proximity to the active glaciers enabled us to reconstruct the lia advance in this area the lia maximum advance occurred between cal yr 1550 and 1720 ad and a readvance occurred around cal yr 1830 ad in addition glacier fluctuations of the las vacas and gussfeltd glaciers 33 s and el penon and el azufre glaciers were documented from the end of the 19th century to the present based on historical and aerial photographs and satellite images the glaciers showed a marked retreat during 1894 2007 minor readvances occurred in the 1980s and 1990s which could be related with strong warm enso events during these decades our results are consistent with observations made by other authors in the region

renewal rate estimation of groundwater based on radioactive tracers 3h 14c in an unconfined aquifer in a semi arid area iullemeden basin niger abstract estimation of groundwater recharge in arid and semi arid areas is difficult due to the low amount and variability of recharge a combination of radiotracers investigation based on simple mixing models allows direct investigation of relatively long term renewal rates of an aquifer the recharge process of the shallow continental terminal aquifer in the iullemeden basin niger was investigated using a geochemical and isotopic approach this study investigates the area in the one degree square of nianey 13 14 n 2 3 e in this area recharge is highly heterogeneous and mainly occurs through a drainage system of temporary streams and pools during the rainy season heterogeneity of the recharge is reflected through the wide variation in electrical conductivity and oxygen 18 content of the groundwater the carbon 14 activity range for most of the groundwater falls between 69 and 126 pmc showing pre and post aerial thermonuclear test recharge two renewal rate models have been investigated the first one models a well mixed reservoir and the second one is derived from a piston flow model in which mixing is in equal proportions major ions in tritium data analyses allow exclusion of non representative samples and confirm the carbon 14 renewal rate estimations both models give similar results for the relatively low renewal rate investigated in the area using carbon 14 the mean annual rates of groundwater renewal range from 3 to 0 03 of the aquifer volume with a median of 0 1 assuming the median is representative of the overall renewal rate of the area the recharge rate is in the order of 5 mm a 1 the shallow aquifer recharge extends from the last small humid period around 4000 a up to now high recharge rates are found in depressions whereas low recharge occurs below the plateaux

carbon isotopes to constrain the origin and circulation pattern of groundwater in the north western part of the bohemian cretaceous basin czech republic abstract the bohemian cretaceous basin represents a complex hydrogeological system composed of several aquifers with very favourable hydrogeological properties these aquifers have been exploited for many years the sustainability of such resources might be guaranteed by well organised water management which requires a detailed knowledge about the functioning of the hydrogeological system although many efforts have previously been made to evaluate groundwater residence time the many intricate geochemical processes complicate groundwater dating the current study clarifies the functioning of this complex hydrogeological basin using hydrogeochemical and isotopic investigations chemical data and a combination of 13 c and 14 c isotopes within the cenomanian and the turonian layers indicate groundwater interactions with deep seated co 2 rock matrix surface waters and fossil organic matter very depleted 13 c values average 13 c 13 4 suggest interactions with fossil organic matter whereas enriched values account for the interaction with deep co 2 gas ascending from the upper mantle via the numerous faults and fractures and also to a lesser extent from calcite dissolution geochemical processes that take place in the system cause a clear depletion in 14 c that greatly complicates groundwater residence time evaluation different dilution correction models have been applied considering the different c origins the stable isotope content mainly 18 o values indicates both the contribution of modern precipitation and the partial infiltration of palaeowaters during colder climatic conditions from the end of the pleistocene the apparent 14 c groundwater ages range from modern to 11 1 ka bp which suggests some post glacial infiltration from melting ice sheets finally all the acquired information was used to propose a conceptual model of c origin within the basin

the predominance of post wildfire erosion in the long term denudation of the valles caldera new mexico nsf ear 0724958 ear 1331408 valles caldera national preserve gsa graduate student research grant

osl chronology of middle to late holocene aeolian activity in the st anthony dune field southeastern idaho usa abstract late quaternary aeolian dune systems in the great plains and western u s are valuable archives of past climate variability this study investigates the st anthony dune field located in the eastern portion of the snake river plain in southern idaho the current semi arid climate of the region allows for a central core of active dunes that is approximately 450 km 2 in area and includes compound crescentic blowout falling and climbing dunes that range in height from 15 to 121 m the surrounding region is characterized by 20 000 km 2 of relic parabolic linear and complex linear dunes that are currently fixed by vegetation this study examined nine samples collected from the fixed dunes that surround the active core of the st anthony dune field optically stimulated luminescence osl dating results indicate that these fixed dunes were mobile and actively accreting 6 6 ka middle holocene and 1 0 2 0 ka late holocene evidence for activation of a large region currently occupied by stable dunes suggests these periods were characterized by hydrologic deficit and or warmer climate conditions than currently exists this research provides new information regarding the depositional timing of the st anthony dunes and assists in providing evidence of palaeo climatic conditions for the eastern snake river plain during the middle to late holocene

holocene climatic instability a prominent widespread event 8200 yr ago the most prominent holocene climatic event in greenland ice core proxies with approximately half the amplitude of the younger dryas occurred 8000 to 8400 yr ago this holocene event affected regions well beyond the north atlantic basin as shown by synchronous increases in windblown chemical indicators together with a significant decrease in methane widespread proxy records from the tropics to the north polar regions show a short lived cool dry or windy event of similar age the spatial pattern of terrestrial and marine changes is similar to that of the younger dryas event suggesting a role for north atlantic thermohaline circulation possible forcings identified thus far for this holocene event are small consistent with recent model results indicating high sensitivity and strong linkages in the climatic system

spatiotemporal variability of the precipitation dipole transition zone in the western united states 1 el nino southern oscillation related hydroclimatic variability in the western united states is characterized by a north south dipole pattern of precipitation anomalies with opposing signs here i use a high resolution dataset to analyze spatiotemporal patterns in the transition zone between the centers of opposite association results indicate that the transition zone is spatially limited west of the continental divide consisting of a narrow zone within the 40 42 n latitude band and portions of eastern washington eastern oregon and western colorado the transition zone was narrower when the southern oscillation index and the pacific decadal oscillation pdo were in a constructive phase and during the negative atlantic multidecadal oscillation phase although the transition zone has remained remarkably stationary across the great basin shifts likely pdo related have occurred over time in the west coast states implications for water resource planning in river basins underlying the transition zone vary by region

mount mazama eruption calendrical age verified and atmospheric impact assessed geochemical identification of mount mazama ash in the greenland ice sheet project 2 gisp2 ice core gives a calendrical age of 7627 150 cal yr b p 5677 150 b c for the eruption thus providing a more accurate early holocene stratigraphic time line than previously available the gisp2 record of volcanically derived sulfate suggests a total stratospheric aerosol loading between 88 and 224 mt spread over an 6 yr period following the eruption of mount mazama taking into account the likelihood of some tropospheric aerosol transport to greenland realistic estimates of the resulting atmospheric optical depth range from 0 6 to 1 5 these values may have produced a temperature depression of 0 6 to 0 7 c at mid to high northern latitudes for 1 3 yr after the eruption these results indicate that the 5677 b c eruption of mount mazama was one of the most climatically significant volcanic events of the holocene in the northern hemisphere we also calculate a maximum stratospheric cl release of 8 1 mt by the eruption which may have led to substantial stratospheric ozone depletion

vegetative and climatic controls on holocene wildfire and erosion recorded in alluvial fans of the middle fork salmon river idaho the middle fork salmon river watershed spans high elevation mixed conifer forests to lower elevation shrub steppe in recent decades runoff from severely burned hillslopes has generated large debris flows in steep tributary drainages these flows incised alluvial fans along the mainstem river where charcoal rich debris flow and sheetflood deposits preserve a record of latest pleistocene to holocene fires and geomorphic response through deposit sedimentology and 14c dating of charcoal we evaluate the processes and timing of fire related sedimentation and the role of climate and vegetation change fire related deposits compose 66 of the total measured fan deposit thickness in more densely forested upper basins versus 33 in shrub steppe dominated lower basins fires during the middle holocene 8000 5000 cal yr bp mostly resulted in sheetflood deposition similar to modern events in lower basins decreased vegetation density during this generally warmer and drier period likely resulted in lower sev

geochemistry of fluid discharges from peteroa volcano argentina chile in 2010 2015 insights into compositional changes related to the fluid source region s abstract this study presents the first geochemical data of fluid discharges collected from february 2010 to march 2015 from the planchon peteroa azufre volcanic complex ppavc located in the transitional southern volcanic zone tsvz at the border between argentina and chile during the study period from january 2010 to july 2011 peteroa volcano experienced phreatic to phreatomagmatic eruption possibly related to the devastating maule earthquake occurred on february 27 2010 the compositional dataset includes low temperature from 43 2 to 102 c gas discharges from i the summit of peteroa volcano and ii the se flank of azufre volcano both marked by a significant magmatic fluid contribution as well as bubbling gases located at the foothill of the peteroa volcanic edifice which showed a chemical signature typical of hydrothermal fluids in 2012 strong compositional changes affected the peteroa gases from the summit area the acidic gas species especially so 2 increased suggesting an input of fluids from magma degassing nevertheless the r ra and 13 c co 2 values decreased which would imply an enhanced contribution from a meteoric hydrothermal source in 2014 2015 the chemical and isotopic compositions of the 2010 2011 gases were partially restored the anomalous decoupling between the chemical and the isotopic parameters was tentatively interpreted as produced by degassing activity from a small batch of dacitic magma that in 2012 masked the compositional signature of the magmatic fluids released from a basaltic magma that dominated the gas chemistry in 2010 2011 this explanation reliably justifies the observed geochemical data although the mechanisms leading to the change in time of the dominating magmatic fluid source are not clear at this regard a geophysical survey able to provide information on the location of the two magma batches could be useful to clarify the possible relationships between the compositional changes that affected the peteroa fluid discharges and the 2010 2011 eruptive activity

predicting the probability and volume of postwildfire debris flows in the intermountain western united states empirical models to estimate the probability of occurrence and volume of postwildfire debris flows can be quickly implemented in a geographic information system gis to generate debris flow hazard maps either before or immediately following wildfires models that can be used to calculate the probability of debris flow production from individual drainage basins in response to a given storm were developed using logistic regression analyses of a database from 388 basins located in 15 burned areas located throughout the u s intermountain west the models describe debris flow probability as a function of readily obtained measures of areal burned extent soil properties basin morphology and rainfall from short duration and low recurrence interval convective rainstorms a model for estimating the volume of material that may issue from a basin mouth in response to a given storm was developed using multiple linear regression analysis of a database from 56 basins burned by eight fires this model describes debris flow volume as a function of the basin gradient aerial burned extent and storm rainfall applications of a probability model and the volume model for hazard assessments are illustrated using information from the 2003 hot creek fire in central idaho the predictive strength of the approach in this setting is evaluated using information on the response of this fire to a localized thunderstorm in august 2003 the mapping approach presented here identifies those basins that are most prone to the largest debris flow events and thus provides information necessary to prioritize areas for postfire erosion mitigation warnings and prefire management efforts throughout the intermountain west

fire storms and erosional events in the idaho batholith in late december 1996 the south fork payette river basin in west central idaho experienced a prolonged storm that culminated on january 1 1997 with intense rain on melting snow that triggered slide failures producing debris flows and sediment charged floods failures occurred in saturated cohesionless grussy colluvium derived from weathered idaho batholith granitic rocks many failures along the south fork payette river originated in ponderosa pine forests burned in the 1989 stand replacing lowman fire an example is the 0 49 km 2 jughead creek basin where a single large colluvial failure produced almost 40 of the total volume eroded from the basin and generated a massive and rapid debris flow failures also occurred in steep unburned and unforested drainages such as hopkins creek in this south facing 0 58 km 2 basin 15 colluvial hollows failed but no single failure produced more than 10 of the total eroded volume sediment transport in hopkins creek occurred by prolonged sediment charged sheetflooding despite vegetation differences sediment yields from the geomorphically similar hopkins creek 42 000 mg km 2 and jughead creek 44 000 mg km 2 basins were quite similar these 1997 erosion events are equivalent to several thousand years of sediment yield at low rates 2 7 30 mg km 2 year 1 measured by short term sediment trapping and gauging in idaho batholith watersheds if similar large events were solely responsible for sediment export recurrence intervals ris of several hundred years would account for higher sediment yields averaged over 10 4 year from idaho batholith watersheds dating of small fire induced sheetflooding events in an early holocene tributary junction fan of jughead creek indicates that frequent small sedimentation events ri 33 80 year occurred between 7400 and 6600 cal year bp with an average yield not greatly exceeding 16 mg km 2 year 1 compared with the holocene average erosion rates during that 800 year period were unusually low suggesting that sediment yields have not been constant over time and that climatic variations and related fire regime changes may exert a strong influence on the probability of major erosional events copyright 2001 john wiley sons ltd

humidity changes in southern tunisia during the late pleistocene inferred from u th dating of mollusc shells abstract calcareous deposits mainly consisting of mollusc shell accumulations which have been dated by the u th disequilibrium method mark the shorelines of paleolake highstands in the great chotts area of southern tunisia the 5 sites studied consist of discontinuous accumulations of fossils of marine like organisms e g cerastoderma glaucum melania tuberculata melanopsis praemorsa cerithium rupestre u th isochron plots and age frequency histograms for 39 shell samples are reported here limited variations for u content and 234u 238u activity ratios ar of shells support the hypothesis of closure of the geochemical system with respect to this element it is remarkable that 234u 238u ar of shells collected in chott fejej or chott jerid are clustered around different values reflecting probably different groundwater recharge from the continental intercalaire ci or complexe terminal ct aquifers furthermore waters collected near wadi el akarit show 234u 238u ar values comparable to those observed for shells 14c determinations made on aliquots of some of these samples suggested an age distribution between 18 and 34 ka bp the u th data of these 39 shell samples imply that 4 distinct flood episodes of these lakes occurred at about 30 95 100 130 150 and 180 200 ka for the episode centred around 30 ka the frequency histogram of ages shows a multimodal age group that could represent the existence of several humid pulses rather than a unique event moreover the comparison of 13c and 18o with those of older humid pleistocene phases when very large palaeolakes have been recorded suggests that these young carbonate shells are not related to a true highstand lake it is suggested that they represent a period of less humid climatic conditions with carbonate accumulation in minor water ponds in which intensive biological activity could have taken place it should be noted that this period was less arid than the present

holocene seasonal variability inferred from multiple proxy records from crevice lake yellowstone national park usa article i nfo a 9400 yr old record from crevice lake a semi closed alkaline lake in northern yellowstone national park was analyzed for pollen charcoal geochemistry mineralogy diatoms and stable isotopes to develop a nu anced understanding of holocene environmental history in a region of northern rocky mountains that re ceives both summer and winter precipitation the limited surface area conical bathymetry and deep water 31 m of crevice lake create oxygen deficient conditions in the hypolimnion and preserve annually laminated sediment varves for much of the record pollen data indicate that the watershed supported a closed pinus dominated forest and low fire frequency prior to 8200 cal yr bp followed by open parkland until 2600 cal yr bp and open mixed conifer forest thereafter fire activity shifted from infrequent stand replacing fires initially to frequent surface fires in the middle holocene and stand replacing events in recent centuries low values of 18 o suggest high winter precipitation in the early holocene followed by steadily drier conditions after 8500 cal yr bp carbonate rich sediments before 5000 cal yr bp imply warmer summer conditions than after 5000 cal yr bp high values of molybdenum mo uranium u and sulfur s indicate anoxic bottom waters before 8000 cal yr bp between 4400 and 3900 cal yr bp and after 2400 cal yr bp the diatom record indicates extensive water column mixing in spring and early summer through much of the holocene but a period between 2200 and 800 cal yr bp had strong summer stratification phosphate limita tion and oxygen deficient bottom waters together the proxy data suggest wet winters protracted springs and warm effectively wet summers in the early holocene and less snowpack cool springs warm dry sum mers in the middle holocene in the late holocene the region and lake experienced extreme changes in win ter spring and summer conditions with particularly short springs and dry summers and winters during the roman warm period 2000 cal yr bp and medieval climate anomaly 1200 800 cal yr bp long springs and mild summers occurred during the little ice age and these conditions persist to the present although the proxy data indicate effectively wet summer conditions in the early holocene and drier conditions in the middle and late holocene none point specifically to changes in summer precipitation as the cause in stead summer conditions were governed by multi seasonal controls on effective moisture that operated over multiple time scales

the effect of holocene temperature fluctuations on the evolution and ecology of neotoma woodrats in idaho and northwestern utah abstract animals respond to climatic change by adapting or by altering distributional patterns how an animal responds is influenced by where it is positioned within its geographic range the probability of extirpation is increased near range boundaries here we examine the impact of holocene climatic fluctuations on a small mammalian herbivore the bushy tailed woodrat neotoma cinerea at five locations within south central idaho and northwestern utah previous work demonstrated that woodrats adapt to temperature shifts by altering body size we focus here on the relationship between body mass temperature and location within the geographic range body mass is estimated by measuring fossil fecal pellets a technique validated in earlier work overall we find the predicted phenotypic response to climate change animals were larger during cold periods and smaller during warmer episodes however we also identify several time periods when changes in environmental temperature exceeded the adaptive flexibility of n cinerea a smaller bodied species the desert woodrat n lepida apparently invaded lower elevation sites during the mid holocene despite being behaviorally and physically subordinate to n cinerea analysis of contemporary patterns of body size and thermal tolerances for both woodrat species suggests this was because of the greater heat tolerance of n lepida the robust spatial relationship between contemporary body size and ambient temperature is used as a proxy to reconstruct local climate during the holocene

recharge and paleo recharge of groundwater in different basins in tunisia abstract assessment of the recharge is of strategic importance for a sustainable development of the aquifer resource especially in arid and semi arid areas this study synthesizes and compares the results of isotope hydrology investigations obtained for different aquifer systems in tunisia the 2h 18o values and 14c and 3h contents are distinct in unconfined and confined groundwater and vary from northern to southern parts of tunisia reflecting different recharge conditions low 2h and 18o values of deep confined groundwater in the southern and central parts agrees with groundwater residence times that suggest an important phase of recharge during the holocene and pleistocene under paleo climatic conditions that are quite humid from the current the study of paleo groundwater signals of these aquifers indicates that the transition from the end of the pleistocene to the holocene is associated with a much humid climate to give a widespread age signal in southern and central deep groundwater in tunisia furthermore the current climatic conditions are the determining factors in the recharge process of tunisia aquifers so they allow only very low recharge rates of most aquifers as a result paleo water is dominating in many groundwater basins particularly where the extraction of water exceeds the present recharge

correcting temporal frequency distributions for taphonomic bias in this paper we expand upon a prior study surovell t a brantingham p j 2007 a note on the use of temporal frequency distributions in studies of prehistoric demography journal of archaeological science 34 1868 1877 that explored the problem of taphonomic bias taphonomic bias refers to the tendency for younger things to be over represented relative to older things in the archaeological record due to the operation of destructive processes like erosion and weathering using a database of radiocarbon dated volcanic deposits from bryson r u bryson r a ruter a 2006 a calibrated radiocarbon database of late quaternary volcanic eruptions earth discussions 1 123 124 we develop an empirical model of taphonomic bias in contrast to our prior study in which we modeled taphonomic bias as an exponential function wherein the likelihood of site loss remains constant through time we argue that the probability of site destruction actually decreases with site age we further demonstrate how this model can be used to correct temporal frequency distributions and extract demographic histories we illustrate this approach using databases of radiocarbon dates from rockshelter and open air sites in the bighorn basin wyoming usa and mammoths and humans in siberia russia

high resolution satellite and airborne thermal infrared imaging of precursory unrest and 2009 eruption at redoubt volcano alaska abstract a combination of satellite and airborne high resolution visible and thermal infrared tir image data detected and measured changes at redoubt volcano during the 2008 2009 unrest and eruption the tir sensors detected persistent elevated temperatures at summit ice melt holes as seismicity and gas emissions increased in late 2008 to march 2009 a phreatic explosion on 15 march was followed by more than 19 magmatic explosive events from 23 march to 4 april that produced high altitude ash clouds and large lahars two or three lava domes extruded and were destroyed between 23 march and 4 april after 4 april the eruption extruded a large lava dome that continued to grow until at least early july 2009

coseismic slip distribution of the february 27 2010 mw 8 8 maule chile earthquake 1 static offsets produced by the february 27 2010 mw 8 8 maule chile earthquake as measured by gps and insar constrain coseismic slip along a section of the andean megathrust of dimensions 650 km in length 180 km in width gps data have been collected from both campaign and continuous sites sampling both the near field and far field alos palsar data from several ascending and descending tracks constrain the near field crustal deformation inversions of the geodetic data for distributed slip on the megathrust reveal a pronounced slip maximum of order 15 m at 15 25 km depth on the megathrust offshore lloca indicating that seismic slip was greatest north of the epicenter of the bilaterally propagating rupture a secondary slip maximum appears at depth 25 km on the megathrust just west of concepcion coseismic slip is negligible below 35 km depth estimates of the seismic moment based on different datasets and modeling approaches vary from 1 8 to 2 6 1022 n m our study is the first to model the static displacement field using a layered spherical earth model allowing us to incorporate both near field and far field static displacements in a consistent manner the obtained seismic moment of 1 97 1022 n m corresponding to a moment magnitude of 8 8 is similar to that obtained by previous seismic and geodetic inversions

early holocene change in atmospheric circulation in the northern great plains an upstream view of the 8 2 ka cold event elk lake in northwestern minnesota contains numerous proxy records of climatic and environmental change contained in varved sediments with annual resolution for the last 10 000 years these proxies show that about 8200 calendar years ago 8 2 cal ka 7300 radiocarbon years elk lake went froma well stratified lake that was wind protected in a boreal forest to a wellmixed lake in open prairie savanna receiving northwesterly wind blown dust probably from the dry floor of lake agassiz this change in climate marks the initiation of the widely recognized mid holocene altithermal in central north america the coincidence of this change with the so called 8 2 cal ka cold event recognized in ice core and other records fromthe circum north atlantic and thought by some to be caused by catastrophic discharge of freshwater from proglacial lakes agassiz and ojibway suggests that the two events might be related our interpretation of the elk lake proxy records and of other records from less accurately dated sites suggests that change in climate over north america was the result of a fundamental change in atmospheric circulation in response to marked changes in the relative proportions of land water and especially glacial ice in north america during the early holocene this change in circulation probably post dates the final drainage of proglacial lakes along the southern margin of the laurentide ice sheet and may have produced a minor perturbation in climate over greenland that resulted in a brief cold pulse detected in ice cores r 2002 elsevier science ltd all rights reserved

late holocene relationships among fire climate and vegetation in a forest sagebrush ecotone of southwestern idaho usa the forest sagebrush ecotone is characterized by a more arid climate than forested regions therefore establishing fire histories using traditional methods e g fire scars from trees charcoal in lake sediments is problematic this study uses radiocarbon dating of charcoal preserved in alluvial deposits to reconstruct a record of fire and geomorphic response in southwestern idaho samples indicate three primary periods of fire related activity 4400 4000 2000 1400 and 650 400 cal yr bp charcoal macrofossil identification and comparison with other regional records indicate this area has likely alternated between a fuel limited system fires limited by lack of fuels and a moisture limited system fires limited by too much moisture with changes in holocene climate over the past 2000 yr samples from this site indicate most fires occurred during wetter times than the record average during overall wetter periods e g little ice age lia 600 100 cal yr bp tree density may have increased

changes in fire regimes since the last glacial maximum an assessment based on a global synthesis and analysis of charcoal data fire activity has varied globally and continuously since the last glacial maximum lgm in response to long term changes in global climate and shorter term regional changes in climate vegetation and human land use we have synthesized sedimentary charcoal records of biomass burning since the lgm and present global maps showing changes in fire activity for time slices during the past 21 000 years as differences in charcoal accumulation values compared to pre industrial there is strong broad scale coherence in fire activity after the lgm but spatial heterogeneity in the signals increases thereafter in north america europe and southern south america charcoal records indicate less than present fire activity during the deglacial period from 21 000 to 11 000 cal yr bp in contrast the tropical latitudes of south america and africa show greater than present fire activity from 19 000 to 17 000 cal yr bp and most sites from indochina and australia show greater than present fire activity from 16 000 to 13 000 cal yr bp many sites indicate greater than present or near present activity during the holocene with the exception of eastern north america and eastern asia from 8 000 to 3 000 cal yr bp indonesia and australia from 11 000 to 4 000 cal yr bp and southern south america from 6 000 to 3 000 cal yr bp where fire activity was less than present regional coherence in the patterns of change in fire activity was evident throughout the post glacial period these complex patterns can largely be explained in terms of large scale climate controls modulated by local changes in vegetation and fuel load

holocene periodicity in north atlantic climate and deep ocean flow south of iceland climate fluctuations during the past millennium are relatively well documented1 on a longer timescale there is growing evidence of millennial scale variability of holocene climate at periodicities of 2 500 and 950 years possibly caused by changes in solar flux 2 3 and 1 500 years maybe related to an internal oscillation of the climate system 4 5 6 but the involvement of deep water masses in these holocene climate changes has yet to be established here we use sediment grain size data from the iceland basin to reconstruct past changes in the speed of deep water flow the study site is under the influence of iceland scotland overflow water isow the flow of which is an important component of the thermohaline circulation that modulates european climate flow changes coincide with some known climate events the little ice age and the mediaeval warm period and extend over the entire holocene epoch with aquasi periodicity of 1 500 years the grain size data indicate afaster isow flow when the climate of northern europe is warmer however a second mode of operation is observed in the early holocene when warm climate intervals are associated with slower isow flow at that time the melting remnant of land based glacial age ice may have provided a sufficient source of fresh water to the ocean to reduce isow flow south of iceland

north south precipitation patterns in western north america on interannual to decadal timescales the overall amount of precipitation deposited along the west coast and western cordillera of north america from 258 to 558n varies from year to year and superimposed on this domain average variability are varying north south contrasts on timescales from at least interannual to interdecadal in order to better understand the north south precipitation contrasts their interannual and decadal variations are studied in terms of how much they affect overall precipitation amounts and how they are related to large scale climatic patterns spatial empirical orthogonal functions eofs and spatial moments domain average central latitude and latitudinal spread of zonally averaged precipitation anomalies along the westernmost parts of north america are analyzed and each is correlated with global sea level pressure slp and sea surface temperature series on interannual defined here as 3 7 yr and decadal 7 yr timescales the interannual band considered here corresponds to timescales that are particularly strong in tropical climate variations and thus is expected to contain much p

wildfire related debris flow initiation processes storm king mountain colorado a torrential rainstorm on september 1 1994 at the recently burned hillslopes of storm king mountain co resulted in the generation of debris flows from every burned drainage basin maps 1 5000 scale of bedrock and surficial materials and of the debris flow paths coupled with a 10 m digital elevation model dem of topography are used to evaluate the processes that generated fire related debris flows in this setting these evaluations form the basis for a descriptive model for fire related debris flow initiation the prominent paths left by the debris flows originated in 0 and 1st order hollows or channels discrete soil slip scars do not occur at the heads of these paths although 58 soil slip scars were mapped on hillslopes in the burned basins material derived from these soil slips accounted for only about 7 of the total volume of material deposited at canyon mouths this fact combined with observations of significant erosion of hillslope materials suggests that a runoff dominated process of progressive sediment entrainment by surface runoff rather than infiltration triggered failure of discrete soil slips was the primary mechanism of debris flow initiation a paucity of channel incision along with observations of extensive hillslope erosion indicates that a significant proportion of material in the debris flows was derived from the hillslopes with a smaller contribution from the channels because of the importance of runoff dominated rather than infiltration dominated processes in the generation of these fire related debris flows the runoff contributing area that extends upslope from the point of debris flow initiation to the drainage divide and its gradient becomes a critical constraint in debris flow initiation slope area thresholds for fire related debris flow initiation from storm king mountain are defined by functions of the form acr tan 3 s where acr is the critical area extending upslope from the initiation location to the drainage divide and tan is its gradient the thresholds vary with different materials

a record of lateglacial holocene environmental change from a high elevation site in the intermountain west usa records of past vegetation and fire history can be complicated by changes in the depositional environment of a sampling location however these changes can alternatively be used as a measure of climate variability our study site ca 18 0 cal ka bp record from little brooklyn lake wyoming located near the crest of the snowy range records three moisture states initially the lake was likely a glacier fed pond indicated by the presence of pediastrum algae colonies around 13 0 cal ka bp this pond transitioned to a meadow environment suggested by the loss of pediastrum algae colonies and slow sedimentation rates meadow conditions were maintained until ca 5 0 cal ka bp when pediastrum algae colony abundance increased indicating the formation of a shallow lake from 18 0 to ca 5 0 cal ka bp the pollen record is suggestive of alpine vegetation conditions with relatively high spruce and herbaceous taxa low charcoal influx also characterizes the period between 18 0 and 5 0 cal ka bp after 5 0 cal ka bp the coincidence of the formation of shallow lake and pollen data indicating a shift to a spruce and fir forest suggests an increase in effective moisture fire remained rare in this basin over the entire record however once the lake established sedimentation rates and charcoal influx increased copyright 2013 john wiley sons ltd

episodic flooding of estuarine environments in response to drying climate over the last 6000 years in baffin bay texas abstract recent studies along the northwestern gulf of mexico document rapid centennial scale landward retreat or back stepping of estuarine environments up to 20 km ca 8 0 ka 4 8 ka and 2 6 ka if such rapid changes in coastal environments occurred today along the urbanized coast of the gulf of mexico major economical and ecological loss would occur although the 8 0 ka event occurs at a time of increased rates of sea level rise the latter two do not leading to the hypothesis that they may be the result of past climate change in this study 121 cores 4 3 km of high resolution seismic profiles and 53 radiocarbon dates are utilized to characterize the stratigraphic architecture and constrain the timing of stratigraphic flooding surfaces in the estuarine fill of upper baffin bay texas over the last 6 ky five flooding surfaces which formed between 1 1 1 0 ka 2 7 2 1 ka 3 8 3 0 ka 5 2 4 9 ka and 6 5 5 7 ka occur within error of drying in southern texas driven by warming in the north atlantic and recorded in independent paleoclimate archives we suggest that these flooding surfaces which occurred when sea level in the gulf of mexico was rising

volcano surveillance using infrared cameras abstract volcanic eruptions are commonly preceded accompanied and followed by variations of a number of detectable geophysical and geochemical manifestations many remote sensing techniques have been applied to tracking anomalies and eruptive precursors and monitoring ongoing volcanic eruptions offering obvious advantages over in situ techniques especially during hazardous activity whilst spaceborne instruments provide a distinct advantage for collecting data remotely in this regard they still cannot match the spatial detail or time resolution achievable using portable imagers on the ground or aircraft hand held infrared camera technology has advanced significantly over the last decade resulting in a proliferation of commercially available instruments such that volcano observatories are increasingly implementing them in monitoring efforts improved thermal surveillance of active volcanoes has not only enhanced hazard assessment but it has contributed substantially to understanding a variety of volcanic processes drawing on over a decade of operational volcano surveillance in italy we provide here a critical review of the application of infrared thermal cameras to volcano monitoring following a summary of key physical principles instrument capabilities and the practicalities and methods of data collection we discuss the types of information that can be retrieved from thermal imagery and what they have contributed to hazard assessment and risk management and to physical volcanology with continued developments in thermal imager technology and lower instrument costs there will be increasing opportunity to gather valuable observations of volcanoes it is thus timely to review the state of the art and we hope thereby to stimulate further research and innovation in this area

recharge and paleorecharge of the deep groundwater aquifer system in the zeroud basin kairouan plain central tunisia abstract the multilayered aquifer of zeroud basin is characterized by the hydrodynamic complexity due to natural geology and anthropogenic management features stable and radioactive isotope data have been used to investigate the origin of the groundwater and its recharge area and to understand the deep groundwater system within the southern kairouan sedimentary basin most of the stable isotopic data indicate that most deep groundwater samples derived either from meteoric water or from the zeroud river and were not affected by any significant degree of evaporation during recharge current tritium concentration in the groundwater is very low however it proved useful in the qualitative identification of modern recharge and mixing of recent and old groundwater radiocarbon deduced ages range from more than 30 000 years to modern a modern recharge characterizes the deep aquifer upstream of the basin the groundwater with ages range from more than 30 000 years and depleted of heavy isotopes are found in the deeper aquifer aquifer b downstream of the basin and could be inherited from paleorecharge

15 000 years of vegetation change in the bonneville basin the blue lake pollen record abstract this paper contributes to the emerging picture of late pleistocene and holocene environmental change in the bonneville basin western north america through analysis of pollen and sediments from the blue lake marsh system a major wetland area located on the western margin of the great salt lake desert analyses of data obtained from the upper 4 m of the blue lake core suggest that during the latest pleistocene when lake bonneville covered the blue lake site pine and sagebrush dominated terrestrial plant communities these steppe woodland taxa declined in abundance after 12 cal ka bp wetland plant communities developed at or nearby blue lake by 11 9 cal ka bp and bulrush dominated marshes were established no later than 10 8 cal ka bp the blue lake wetlands largely desiccated during a dry and warm early middle holocene 8 3 6 5 cal ka bp climatic amelioration starting 6 5 cal ka bp is marked principally by a local return of marshes at the expense of playa and grass meadow communities and a regional increase in sagebrush relative to other dryland shrubs singleleaf pinyon pine migrated into the nearby goshute mountains after 8 cal ka bp late holocene fluctuations include cool intervals from 4 4 to 3 4 and 2 7 to 1 5 cal ka bp and warmer conditions from 3 4 to 2 7 cal bp and after 1 5 cal ka bp

holocene thermal maximum in the western arctic 0 180 w the spatio temporal pattern of peak holocene warmth holocene thermal maximum htm is traced over 140 sites across the western hemisphere of the arctic 0 180 w north of 60 n paleoclimate inferences based on a wide variety of proxy indicators provide clear evidence for warmer than present conditions at 120 of these sites at the 16 terrestrial sites where quantitative estimates have been obtained local htm temperatures primarily summer estimates were on average 1 6 0 8 c higher than present approximate average of the 20th century but the warming was time transgressive across the western arctic as the precession driven summer insolation anomaly peaked 12 10 ka thousands of calendar years ago warming was concentrated in northwest north america while cool conditions lingered in the northeast alaska and northwest canada experienced the htm between ca 11 and 9 ka about 4000 yr prior to the htm in northeast canada the delayed warming in quebec and labrador was linked to the residual laurentide ice sheet which chilled the region through its impact on surface energy balance and ocean circulation the lingering ice also attests to the inherent asymmetry of atmospheric and oceanic circulation that predisposes the region to glaciation and modulates the pattern of climatic change the spatial asymmetry of warming during the htm resembles the pattern of warming observed in the arctic over the last several decades although the two warmings are described at different temporal scales and the htm was additionally affected by the residual laurentide ice the similarities suggest there might be a preferred mode of variability in the atmospheric circulation that generates a recurrent pattern of warming under positive radiative forcing unlike the htm however future warming will not be counterbalanced by the cooling effect of a residual north american ice sheet

a process for fire related debris flow initiation cerro grande fire new mexico in this study we examine factors that pertain to the generation of debris flows from a basin recently burned by wildfire throughout the summer 2000 thunderstorm season we monitored rain gauges channel cross sections hillslope transects and nine sediment runoff traps deployed in a steep 0 15 km 2 basin burned by the may 2000 cerro grande fire in new mexico debris flows were triggered in the monitored basin during a rainstorm on july 16 2000 in response to a maximum 30 min rainfall intensity of 31 mm h 1 return period of approximately 2 years eleven other storms occurred before and after the july storm these storms resulted in significant runoff but did not generate debris flows the debris flows generated by the july 16 storm initiated on a broad open hillslope as levee lined rills the levees were composed of gravel and cobble sized material supported by an abundant fine grained matrix debris flow deposits were observed only on the hillslopes and in the first and second order drainages of the monitored basin no significant amounts of channel incision were measured following the passage of the debris flows indicating that most of the material in the flows originated from the hillslopes sediment runoff concentrations of between 0 23 and 0 81 kg l 1 with a mean of 0 42 kg l 1 were measured from the hillslope traps following the debris flow producing storm these concentrations however were not unique to the july 16 storm the materials entrained by the july 16 storm contained a higher proportion of silt plus clay sized materials in the 2 mm fraction than the materials collected from storms that produced comparable sediment runoff concentrations but not debris flows the difference in materials demonstrates the critical role of the availability of fine grained wood ash mantling the hillslopes in the runoff dominated generation of post wildfire debris flows the highest sediment runoff concentrations again not unique to debris flow production were produced from maximum 30 min rainfall intensities greater than 20 mm h 1

late pleistocene to early holocene lake level and paleoclimate insights from stansbury island bonneville basin utah abstract this paper reports on recent multiproxy research conducted to determine the chronology of lake level fluctuations recorded in sediments from a natural exposure at a classic bonneville basin site grain size carbonate percentage magnetic susceptibility amount of charcoal and diatom community composition data were collected from the 16 lacustrine units that compose the 122 cm stratigraphic column in stansbury gulch trends observed in the measured proxies reveal several significant changes in lake level and thereby effective moisture over the approximately 14 500 yr time span represented by the sediments results 1 verify the effectiveness of the multiproxy approach in bonneville basin studies which has been underutilized in this region 2 reaffirm the double nature of lake bonneville s stansbury oscillation 3 suggest a previously undocumented post gilbert highstand of great salt lake and 4 identify possible teleconnections between climate events in the bonneville basin and events in the north atlantic at about 20 500 and 7500 14c yr bp

geochemistry and residence time estimation of groundwater from miocene pliocene and upper cretaceous aquifers of southern tunisia abstract miocene pliocene and upper cretaceous formations in tunisia contain one of the most productive artesian aquifers in the country they consist of mio pliocene sands and senonian turonian carbonates intensive pumping in kebili and nefzaoua regions over the past decades resulted in gradual lowering of water table at the rate of approximately 0 85 m y 1 forty two groundwater samples have been collected from different sectors of the studied aquifers for chemical and isotopic analyses the observed large spatial variability of chemical composition of groundwater in the study area is most probably linked to two processes i dissolution of dolomite and gypsum combined with calcite precipitation dedolomitisation and ii partial evaporation of water the first process plays an important role in the study area due to abundance of evaporites partial evaporation occurs in the upper part of the unsaturated zone during infiltration especially for groundwater sampled in the kebili and djerid regions apart from these processes there are others which influence the salinity of the aquifers in the mio pliocene aquifer which behaves as an open system to gases and which receives inputs of co2 gas derived from intensive tectonic activity in the area the interaction of carbon dioxide with carbonate matrix of the aquifer produces an increase in the alkalinity of water in the senonian and turonian aquifers the process of dedolomitisation evolves in a closed system with respect to co2 gas ca2 na cation exchange and halite dissolution processes are also important stable isotope composition of water 18o 2h indicates that the recharge occurs from the dahar upland the 14c activity varies between 89 5 1 5 and 3 7 2 1 pmc the 13c content in the total dissolved inorganic carbon tdic range between 13 9 and 3 6 the calculated concentrations of 13c in the co2 gas in equilibrium with the tdic vary between 22 and 11 indicating two sources of carbon in the solution carbonate matrix 13c 2 and soil co2 13c from 25 to 21 for the cultivated areas mean residence times of water have been determined after correction of the initial 14c activities for 14c dilution processes including carbonate dissolution calcite precipitation and cation exchange the dilution processes were quantified on the basis of geochemical and 13c mass balance equations the calculated mean residence times of water confirm modern recharge from dahar upland and the mountains surrounding depressions and indicate the presence of paleowaters in the east and south west region and in the discharge zone

lake bonneville fluctuations and global climate change lake bonneville the largest late pleistocene closed basin lake in the north american great basin fluctuated widely in response to changes in climate the geochemistry and mineralogy of endogenic calcium carbonate deposited in deep water and stratigraphic studies of shore zone deposits provide evidence of millennial scale lake level fluctuations that had amplitudes of about 50 m between 30 and 10 ka falling lake events occurred at 21 18 5 19 17 5 16 15 5 14 13 and 10 ka radiocarbon years synchronously with the terminations of heinrich events h1 and h2 and other smaller scale iceberg rafting events a b c and younger dryas in the north atlantic ocean the lake bonneville results thus support other climate records that suggest that late pleistocene millennial scale climate change was global in extent the size and shape of the northern hemisphere ice sheets which determined the mean positions of storm tracks may have been the primary control on late pleistocene water budgets of great basin lakes

paleohydrologie isotopique de l oued el akarit sud tunisie au pleistocene superieur et a l holocene previous data from gobert and howe coque and page on the upper quaternary deposits from wadi el akarit are expanded through radiocarbon and stable isotope measurements 18c and 13c from carbonates 18o and 34s from sulphates these new results report on detailed stratigraphic profiles and indicate fluviatile and palustrine environments during the late pleistocene vegetal dams linked to spring activity caused water stagnation fine grained sediments were deposited with appreciable amounts of organic matter which locally developed into some peaty levels in the upper part of the typical cross section located on the left bank about 100 m upstream of the railway bridge pleistocene deposits show a palustrine carbonate crust this formation is attributed to the drainage induced by the major marine regression at glacial maximum during the holocene stagnation periods still occurred interrupted by flood episodes marked by bottom transport and coarse deposits in the typical cross section deposits are well drained and oxidized however downstream a stagnation episode takes place with a rich malacofauna dominated by cerastoderma cardium the uneven distribution of rainfall is documented by the alternation of fine and coarse deposits and it is accentuated by the climatic evolution toward aridity which results in the formation of a gypsum crust after 4000 yr bp later exceptional floods removed sediments from the wadi channel cutting the upper quaternary deposits for about 13 m along the central course of the wadi radiocarbon ages on carbonates are discussed according to various possible origins of total dissolved carbon atmospheric co2 organic activity in the basins and aquifer supply a simple exchange mixing model between aquifer bicarbonate and atmospheric co2 is used for calculations of initial carbonate activities chemical isotopic and hydraulic steady states are assumed in this treatment present day 14c and 13c contents of aquifer bicarbonate are thus adopted for past values the model leads to acceptable corrected ages for pleistocene carbonate samples corrected ages are younger than apparent ages by a few thousands of years and become consistent with ages given by organic matter from nearby levels however holocene samples appear overcorrected their crystallization appears to be controlled by modern organogenic co2 holocene 14c ages are probably correct 18o contents of carbonate indicate a continental origin for environmental water nodules and carbonate concretions crystallized in bottom sediments through upward leakage of confined aquifers they show 18o contents compatible with present day stable isotope compositions of artesian springs this supports the concept of a good time constancy in stable isotope contents shell carbonate values indicate a variable evaporation rate from the same initial waters 18o and 34s contents of gypsums are also compatible with aqueous sulphates from springs the data set falls within the range of permo triassic sulphate and suggests deep hydraulic connections within aquifer systems the entire formation appears to be of continental origin the occurence of cardium rich basins can only be attributed to the initial salinity of springs waters 7 9 g 1 1 sightly increased by evaporation this signifies that one can not deduce any tectonic uplift from their location with respect to sea level

hydrogeochemical processes affecting groundwater in an irrigated land in central tunisia detailed hydrogeochemical investigation has provided new information concerning the major factors and mechanisms controlling the groundwater chemistry of chougafiya basin the hydrogeochemical characteristics of groundwaters comprise three main types cl so4 ca cl so4 na and cl na hydrochemical characteristics based on the bivariate diagrams of major cl so42 no3 hco3 na mg2 k and ca2 and some trace br and sr2 ions mineral saturation indices and hierarchical cluster analysis indicate different origins of groundwater mineralization the water rock interaction dissolution of evaporitic minerals followed by cation exchange reactions with clay minerals constitute the main processes that control groundwater salinization however the chemical composition of brackish groundwater in the central and southern parts of the study area is influenced by a mixing process with sabkhas salt groundwater the mixing proportions inferred from chloride mass balance prove that the contribution of sabkhas groundwater to quaternary aquifer ranges between 2 7 and 9 1 these intrusion rates reflect the progress of the saltwater freshwater interface which is mainly controlled by the piezometric level variation and the distance to the sabkhas

groundwater salinization processes in shallow coastal aquifer of djeffara plain of medenine southeastern tunisia urban and industrial development and the expansion of irrigated agriculture have led to a drastic increase in the exploitation of groundwater resources the over exploitation of coastal aquifers has caused a seawater intrusion and has seriously degraded groundwater quality the shallow coastal aquifer of the djeffara plain southeastern tunisia constitutes an example of water resource suffering an intensive and uncontrolled pumping for irrigation intensive exploitation of the aquifer and climate aridity caused a decrease in piezometric level and an increase in salinity according to the hydrochemical data cl so4 2 no3 hco3 br ca2 mg2 na k and the stable isotope composition oxygen 18 and deuterium content groundwater salinization in the investigated system is caused by three main processes i salts dissolution especially in the central part of jerba and around medenine plain ii evaporation process and iii seawater intrusion which caused the increase in salinity in the peninsula of el jorf in jerba and in the north of ben gardane

fire and alluvial chronology in yellowstone national park climatic and intrinsic controls on holocene geomorphic processes we employed a systemwide approach a large and robust set of radiocarbon ages and modern process analogs to interpret the holocene history of forest fire related sedimentation and overall alluvial activity in northeastern yellowstone national park debris flow and flood events following the 1988 fires provided facies models for interpreting the stratigraphic record of fire related sedimentation within valley side alluvial fans of soda butte creek fire related deposits make up approximately 30 of the late holocene fan alluvium fifty 14 c ages on fire related events cluster within the intervals of 3300 2900 2600 2400 2200 1800 and 1400 800 yr b p and suggest earlier episodes of large fires and fan aggradation around 7500 5500 and 4600 4000 yr b p a major pulse of fire related debris flow activity between 950 and 800 yr b p coincided with the height of the widely recognized medieval warm period ca a d 1050 1200 instrumental climate records over the last 100 yr in yellowstone imply that the intensity and interannual variability of summer precipitation are greater during warmer periods enhancing the potential for severe short term drought major forest fires and storm generated fan deposition along lower soda butte creek fill cut terrace treads were created by lateral migration of channels and accumulation of overbank sediments ca 8000 yr b p terrace level t1a 7000 5600 t1b 3100 2600 t2 2000 1300 t3 and post 800 yr b p t4 these periods coincide with overbank sedimentation on slough creek and the lamar river but alternate with intervals of fire related fan deposition implying a strong climatic control local paleoclimatic data suggest cooler effectively wetter conditions during terrace tread formation in warmer drier intervals reduced average runoff in axial streams results in meander belt narrowing concurrent channel incision may be caused by infrequent large floods greater resistance to downcutting however allowed fewer terraces to be formed along slough creek and the lamar river alluvial systems in northeastern yellowstone show a clear response to millennial scale climatic cycles wherein alluvial fans aggrade and prograde over flood plains in drier periods axial streams widen their flood plains and trim back the fans during wetter periods small scale climatic fluctuations of the holocene thus had substantial impact on postglacial landscapes in northeastern yellowstone

contrasting climatic histories for the snake river plain idaho resulting from multiple thermal maxima abstract ten sites near the snake river plain have consistent differences in their climatic histories sites at low elevation reflect the early holocene xerothermic of the pacific northwest whereas most climatic chronologies at high elevation indicate maximum warmth or aridity somewhat later ca 6000 yr ago this elevational contrast in climatic histories is duplicated at three sites from the central snake river plain for sites in such close proximity the different chronologies cannot be explained by changes in atmospheric circulation during the late quaternary rather the differences are best explained by the autecology of the plants involved and the changing seasonal climate the seasonal climatic sequence predicted by multiple thermal maxima explains the high and low elevation chronologies during the early holocene maximum insolation and intensified summer drought in july forced low elevation vegetation upward however moisture was not a limiting factor at high elevation where vegetation moved upward in response to increased length of growing season coincident with maximum september insolation 6000 yr ago