integrated hydrogeological and geophysical study of depression focused groundwater recharge in the canadian prairies 1 in the northern prairie region of north america numerous seasonal wetlands and ephemeral ponds form as snowmelt water is trapped in small topographical depressions a detailed hydrogeological investigation is combined with electrical resistivity imaging eri to evaluate the roles of the wetlands and ponds on depression focused groundwater recharge at the st denis national wildlife area in saskatchewan canada the analysis of groundwater samples indicated two distinct geochemical zones a zone of salt leaching under wetland 109 and zones of salt accumulation under the adjacent uplands two intermediate zones were identified as partially leached or mixed leached unleached and premodern or mixed saline nonsaline water the resistivity images of the areas around 109 were classified using the correlation between eri derived electrical conductivity ec and the groundwater ec the eri data clearly showed that depression focused recharge occurs under all depressions regardless of size leaching is observed to the depth of a regional intertill aquifer indicating that depression focused recharge contributes to the regional groundwater system the eri data also revealed the complex pattern of salt distribution that could not have been recognized by hydrogeological observations alone the complex distribution of salts appears to be caused by interaction between wetlands and variations in topography index terms 1829 hydrology groundwater hydrology 1045 geochemistry low temperature geochemistry keywords depression focused recharge electrical resistivity imaging groundwater recharge prairie wetland

the late devensian 22 000 bp irish sea basin the sedimentary record of a collapsed ice sheet margin the late devensian 20 ka bp glacial geology of the irish sea basin 4000 km2 is an event stratigraphy recording the entry of marine waters into a glacio isostatically depressed basin and the rapid retreat of the irish sea glacier as a tidewater ice margin marine limits occur up to 140 m o d across much of the central basin the ice margin was uncoupled from its bed exposing a subglacially scoured topography to glaciomarine processes the irish sea glacier was a major drainage conduit of the last british ice sheet calving of the marine ice margin resulted in fast flow surging of ice streams recorded by drumlin fields around the northern basin margin and tunnel valleys rapid evacuation of the basin may have stranded large areas of dead ice in peripheral zones e g cheshire shropshire lowlands and initiated the collapse of the ice sheet thick wedges of ice contact glaciomarine sediments were deposited during ice retreat as morainal bank complexes by successive tidewater ice margins stabilized at pinning points around the irish sea coast where morainal banks occur on the seaward side of drumlin swarms there is a clear sequential relationship between rapid ice loss from calving ice margins the development of fast flowing ice streams drumlinization and the pumping of subglacial sediment to tidewater raised delta complexes are locally associated with marine limits along the high relief coastal margins of wales east central ireland and the lake district associated valley infill complexes record downslope resedimentation of heterogenous sediments into the marine environment during ice retreat co eval offshore deposits are represented by well stratified glaciomarine complexes that infill a subglacially scoured topography that shows networks of tunnel valleys glaciomarine mud drapes occur well to the south of the maximum limit of grounded ice in the basin e g north devon scilly islands southern ireland the age of these distal sediments previously mapped as pre devensian tills is constrained by amino acid ratios basin rebound following deglaciation was rapid with over 100 m recovery in 3 ka and was followed by a low marine still stand peat accumulating in offshore areas now as much as 55 m below sea level has been drowned by the postglacial eustatic rise in sea level the glacio sedimentary model identified in this paper involving rapid ice retreat and related sedimentation triggered by rising relative sea level suggests that isotatic downwarping is an important mechanism for deglaciating continental shelves

chemical heterogeneity in diffusion dominated aquitards 1 high resolution measurements of the three dimensional 3 d variability in pore water electrical conductivity ec were obtained at a clay rich aquitard research site the king site 120 m 70 m area in southern saskatchewan canada using direct push probing technology n 35 boreholes these measurements revealed complex lateral heterogeneity in the subsurface salt distributions which raised questions on the validity of the commonly used approach of transposing chemical data from distributed piezometers onto 1 d depth profiles for interpretation and solute transport modeling two dimensional numerical modeling simulations demonstrated that distributed nonuniform salt inputs have existed at the top of the unoxidized till aquitard for the past 3 5 kyr the source of the nonuniform salt inputs is unclear but may be due to either variations in microtopography 0 5 m or variable penetration depth of surface fractures a suite of generic solutions was developed to estimate the critical depth required to obtain chemical homogeneity in aquitards with nonuniform solute inputs and diffusion as the dominant transport mechanism these solutions are presented for a range of sinusoidal input functions with varying amplitudes magnitudes and wavelengths the solutions indicate ec distributions at the king site should be laterally uniform below a depth of around 20 m bg which is consistent with observed ec values at the site this study shows that aquitards with nonuniform salt inputs at their upper boundary are chemically heterogeneous above some critical depth and thus require careful attention when modeling solute transport processes within them

a multiscale study of the permeability of a thick clayey till we describe and evaluate two previously undocumented methods of bulk permeability k determination and compare results obtained with results of conventional smaller scale tests on the same thick clayey till deposit analysis of the downward propagation of seasonal water table fluctuations yielded bulk k of approximately 10 10 m s 1 in close agreement with results of laboratory consolidation and permeameter tests slug tests and distribution of vertical hydraulic gradient with depth in the deposit this agreement suggests that for such materials high gradient tests conducted at small scales of distance and time can provide reasonable estimates of bulk k the results also imply groundwater residence times in the till of thousands of years the flow pattern observed near a large excavation in the till was consistent with the initial recoveries of piezometers installed in much smaller boreholes assuming perturbation of hydraulic head in the formation due to borehole excavation time scales of these perturbations which prevent interpretation of measured hydraulic head using conventional well hydraulic methods varied from months to tens of years

sources and dynamics of sulfur in weathered till western glaciated plains of north america abstract at three sites in the western glaciated plains warman and luck lake in saskatchewan canada and bow river in alberta canada thick 30 m till sequences contain 0 3 0 8 s by dry weight in the unweathered zone depths 2 5 15 m 65 90 of this s is cr reducible pyrite the remainder largely organic s is enriched in 34 s by 6 12 relative to the pyrite at the bow river site both pyrite and organic s are enriched in 34 s by up to 9 relative to samples of the same fractions from the warman and luck lake sites this may reflect a higher content of non marine parent material in southern alberta till at the warman site the sources and dynamics of sulfur in the weathered zone were investigated during weathering of the floral formation till sulfate was produced by the oxidation of pyrite and to a lesser extent by mineralization of organic s based on the distribution of so 4 in the landscape at warman three settings have been distinguished upland leached channel depression and saline ring the upland setting has a 9 m thick weathered zone which contains abundant so 4 mainly as secondary gypsum sulfate has been leached downward from the upper 2 m creating a peak accumulation of gypsum at 3 m sulfate has been leached from the entire 2 5 m deep weathered zone in the channel depression setting by seasonal infiltration of snow melt and lateral flow in contrast at 3 4 m depth in the weathered zone at the edge of the channel so 4 has accumulated as a saline ring here the gypsum s is up to 1 of the soil dry weight in the weathered zone of upland and saline ring settings the 34 s values of the so 4 in sediment extracts water soluble and groundwater 13 1 to 9 0 are very similar to those of the total s 12 0 to 11 4 and pyrite s 16 0 to 10 1 of unweathered floral formation till this indicates an in situ weathering source of the so 4 in contrast the 34 s of so 4 in sediment extracts and groundwater from the leached weathered zone of the upland and channel depression settings 7 7 to 4 5 is enriched in 34 s relative to unweathered floral formation till s this enrichment may be attributed to either 1 isotope fractionation during oxidation of pyrite and or 2 mineralization of residual organic s which is 34 s enriched after pyrite was weathered away

hydrogeology of two saskatchewan tills i fractures bulk permeability and spatial variability of downward flow groundwater flow patterns were compared and contrasted in two deposits of clayey till of different thicknesses both of which overlie regional aquifers in a flat upland recharge area analysis of 67 field and laboratory hydraulic conductivity determinations indicated that conductive fractures in the unoxidized zone of the thinner till dalmeny site give rise to an isotropic bulk permeability of approximately 5 10 9 ms 1 which is two orders of magnitude greater than the bulk permeability of unoxidized till in the thicker deposit warman site vertical pore water velocities estimated using hydraulic and isotopic evidence vary greatly at dalmeny and appear to be of the order of 8 m in 10 000 yr at warman the association of vertical groundwater flux depth to water table and depth of oxidized zone at a given location is referred to as the flow regime there spatially detailed water level monitoring and test drilling indicated substantial variation of the flow regime at dalmeny on a horizontal scale of tens of meters no such variation exists at warman the differentiation of the flow regime at dalmeny is due to higher till permeability which permits a spatially variable response to microtopographically focussed infiltration of surface water recognition of the causes and symptoms of flow regime variability beneath flat till landscapes has implications for environmental assessment procedures agricultural practices wetland management and waste disposal

use of vertical profiles of δ18o to constrain estimates of hydraulic conductivity in a thick unfractured aquitard vertical distributions of 18o were used to constrain hydraulic conductivity k in a thick unfractured aquitard previous investigations utilizing permeability tests at a variety of scales keller et al 1989 indicated that bulk k at the site ranges from 3 5 0 11 m s to 1 2 10 10 m s advective displacements calculated on the basis of these k values lead to a wide range of predicted distributions of natural tracers after 11 000 years comparison of 18o distributions and simulated advection diffusion profiles provide a more precise constraint on advective displacement and hence on k the simulations cast in terms of a peclet number p v2t d ranging in value from 0 to 12 indicate that transport is diffusion controlled and that k is actually less than 1 2 10 11 m s p greater than 0 1 k 1 2 10 11 m s overestimates transport this result indicates that conventional permeability tests in very tight media tend to overestimate k in practical terms advective transport at the site is negligible and transport can be simulated with diffusion only p o

human responses to middle holocene climate change on california s channel islands abstract high resolution archaeological and paleoenvironmental records from california s channel islands provide a unique opportunity to examine potential relationships between climatically induced environmental changes and prehistoric human behavioral responses available climate records in western north america 7 3 8 ka indicate a severe dry interval between 6 3 and 4 8 ka embedded within a generally warm and dry middle holocene very dry conditions in western north america between 6 3 and 4 8 ka correlate with cold to moderate sea surface temperatures sst along the southern california coast evident in ocean drilling program odp core 893a b santa barbara basin an episode of inferred high marine productivity between 6 3 and 5 8 ka corresponds with the coldest estimated ssts of the middle holocene otherwise marked by warm low productivity marine conditions 7 5 3 8 ka the impact of this severe aridity on humans was different between the northern and southern channel islands apparently related to degree of island isolation size and productivity of islands relative to population fresh water availability and on going social relationships between island and continental populations northern channel islanders seem to have been largely unaffected by this severe arid phase in contrast cultural changes on the southern channel islands were likely influenced by the climatically induced environmental changes we suggest that productive marine conditions coupled with a dry terrestrial climate between 6 3 and 5 8 ka stimulated early village development and intensified fishing on the more remote southern islands contact with people on the adjacent southern california coast increased during this time with increased participation in a down the line trade network extending into the western great basin and central oregon genetic similarities between middle holocene burial populations on the southern channel islands and modern california uto aztecan populations suggest middle holocene movement of people at this time from southern california desert environs westward to the southern islands a migration perhaps stimulated by increased continental aridity

pine nut use in the early holocene and beyond the danger cave archaeobotanical record abstract nuts of limber pine pinus flexilis from early holocene strata in danger cave utah are distinguishable by seed coat sculpturing from pine nuts of single needled pinyon pinus monophylla which occur in strata dating bp owls and other taphonomic agents may deposit pine nuts in archaeological sites but the morphology of the pine nuts in danger cave strongly indicate they were deposited by human foragers who brought small quantities with them for food for at least the last 7500 years large scale transport of pine nuts to danger cave from distant hinterlands is unlikely however the seamless transition from limber pine to pinyon pine nuts in the danger cave record suggests that foragers who had utilized limber pine as a food resource easily switched to using pinyon pine nuts when pinyon pine migrated into the region at the close of the early holocene

hydrogeochemistry of a clayey till 2 sources of co2 the spatial distributions of inorganic and organic carbon in gas aqueous and solid phases were studied in an 18 m thick surficial deposit of fractured clayey calcareous till large pco2 increases were observed with increasing depth at the bottoms of vadose zones from which solid organic carbon had been depleted hydrochemical reaction simulations indentified a reaction path consistent with pco2 o2 major element chemistry 13c and 14c isotope observations this path is open to a biogenic co2 reservoir with pco2 higher than and 14c composition considerably different from that of the soil zone such co2 reservoirs occurring in deep vadose shallow saturated zones and thus isolated by overlying sediments from temperature fluctuations which limit soil zone respiration may be common in the western glaciated plains as evidenced by prevalence of hard high pco2 waters in the region s intertill aquifers carbon 14 data suggest that in the till both dissolved organic c and dissolved inorganic c have two sources soil organic matter and kerogen in the till matrix regardless of source s initial 14c activities of both aqueous c pools at the water table are diluted substantially relative to the actual residence time of the water unappreciated this could cause large relative errors in the calculation of radiocarbon based groundwater age dates

hydrogeochemistry of a clayey till 1 spatial variability the spatial variability of hydrogeochemical processes was studied within an 18 m thick unit of clayey till beneath a flat prairie landscape models of major element mass transfer constrained by chemical mineralogical and isotopic measurements on waters and solids were developed for two end member water quality types occurring within the unit the observed pattern of chemical variation which is predominantly lateral on a scale of tens of meters is caused by microtopographically controlled differences in the ratio of vertical water flux to oxidation rate associated with depression focused recharge such variation is to be expected where dynamic flow regimes develop in thin surficial tills containing chemically reduced constituents observed depletions of major elements from oxidized zones of the till support the mass transfer models and demonstrate that the time scales of persistence of hydrogeochemical variability in the till and of water quality evolution in the aquifer beneath range from 104 to 105 year na and s concentrations in such aquifers will depend primarily on ratios of influxes of end member water quality types from the till above while ca mg and inorganic c concentrations will remain high as long as partial pressures of co2 in the till remain high co2 generation in the till is discussed in the companion paper keller this issue

a landslide in till near warman saskatchewan canada little information is available about typical shear strength parameters of tills in southern saskatchewan even though till is the most common earth material used for construction in this region the warman landslide in the south saskatchewan river valley provides some insight into the shear strength characteristics of a till and the results are compared with laboratory tests the till is from the upper till of the sutherland group which has a high clay content relative to the underlying and overlying tills a back analysis of the landslide produced 27 assuming c 0 comparison with laboratory test data and results from a similar landslide near lebret saskatchewan suggests that 22 5 with c 7 kpa may be appropriate residual shear strength parameters a rising water table appears to have been the main contributing factor to instability between 1969 and 1984 there is a possibility however that at the 1 50 return interval for flood levels on the river erosion at the toe of the landslid

controls on the distribution of major ions in pore waters of a thick surficial aquitard transport and geochemical processes controlling the chemical and isotopic composition of pore waters in the upper 45 m of a thick surficial clay rich till battleford formation were studied the upper 3 m of the till is oxidized and fractured the remaining 77 m of the till the aquitard is nonfractured and unoxidized concentrations of total dissolved solids so42 na mg2 and k decrease with depth through the unoxidized zone to a depth of about 15 m below ground below which the concentrations remain constant a similar trend was observed for alkalinity however the decrease in concentration occurs over 20 m in contrast to these ions ca2 concentrations increase with depth through the upper 20 m unoxidized zone below which the concentrations remain relatively constant the distribution of dissolved ions shows the presence of two end members elevated solute concentrations in the oxidized zone attributed to geochemical weathering that occurred since the start of the holocene and connate pleistocene age water at depths between 20 and 45 m abiotic and biotic geochemical reaction rates in the aquitard were shown to be extremely slow or not occurring

influence of till provenance on regional groundwater geochemistry abstract a regional groundwater geochemistry study was conducted in the paskapoo formation of southern alberta canada our study area focused on a region where two continental ice sheets the cordilleran and laurentide met the glacial deposits transported by these ice sheets have different bulk characteristics reflective of the bedrock of the source region of the ice recharge through these two different glacial deposits generates distinctly different water geochemistry within the underlying paskapoo formation such that bedrock aquifer acquires a geochemical signature of the immediately overlying glacial deposits through which recharge occurs oxidation of pyrite in laurentide till generates high sulphate groundwater and associated acid generation leads to enhanced mineral weathering this generates high tds high na so4 groundwater in underlying bedrock aquifers this process appears transitory where thin laurentide drift deposits are completely oxidized and have reduced capacity to generate high sulphate water the same bedrock underlying carbonate dominated cordilleran drift deposits have low tds ca hco3 groundwater

a case study to assess the potential for saline soil development due to irrigation abstract with the help of a generalized conceptual model for the formation of saline soil we examine whether irrigation proposed for an area near lethbridge alberta will compound an existing salinity problem the geology of the site is characterized by weathered and non weathered tills which overlie cretaceous bedrock locally preglacial sands and gravels occur along the axes of two bedrock valleys beneath the site piezometric data define local groundwater flow from west to east following the regional topographic slope however the depth to the water table is extremely variable and controlled by the preglacial sand and gravel unit the existing problem of soil salinity which is restricted to the western part of the study area is caused by the high water table and large quantities of dissolved mineral mass in the groundwater in the central and eastern part of the area the water table occurs at depths greater than 20m and saline soils have not formed flow modeling along a two dimensional cross section confirms that the water table configuration and hence the distribution of saline soils is controlled by the preglacial deposits indications are that excess recharge due to irrigation will not result in a water table rise unless the quantity involved is considerably larger than the natural rate of recharge thus irrigation will not contributed to a marked increase in the size of the area affected by the saline soil

early holocene pinyon pinus monophylla in the northeastern great basin fine grained excavation and analysis of a stratigraphic column from danger cave northeastern great basin suggests prehistoric hunter gatherers were collecting and using singleleaf pinyon pinus monophylla near the site for at least the last 7500 yr human use of the cave began after the retreat of lake bonneville from the gilbert level shortly before 10 000 yr b p in stratum 9 culturally deposited pine nut hulls appear in the sequence by about 7900 yr b p and are continuously present thereafter a hull fragment in stratum 10 is directly dated to 7410 120 yr b p these dates are at least 2000 yr earlier than expected by extrapolation to macrofossil records from the east central and central great basin and necessitate some revision of current biogeographical models of late quaternary pinyon migration

fracture permeability and groundwater flow in clayey till near saskatoon saskatchewan field and laboratory studies of a clayey unweathered glacial till have shown that its bulk permeability exceeds its matrix permeability by two orders of magnitude such findings are common for weathered till but are rare for unweathered till and have important implications for groundwater recharge and contaminant transport the till in question is 6 m thick and appears to be unweathered and unfractured it is overlain by 12 m of weathered and highly fractured till results of consolidation tests on the unweathered till indicate a mean vertical hydraulic conductivity of 3 5 10 11 m s 1 and a mean specific storage of 1 3 10 4 m 1 results of slug tests yield a horizontal hydraulic conductivity of about 5 10 9 m s 1 drawdowns in the till in response to pumping from the aquifer below indicate a vertical hydraulic diffusivity of 4 5 10 5m2 s 1 the slug test results combined with specific storage results from consolidation tests indicate a similar value for horizontal hydraulic diffusivity of 4 10

gravity anomaly at a pleistocene lake bed in nw alaska interpreted by analogy with greenland s lake taserssauq and its floating ice tongue a possible example of a very deep glacial excavation is provided by a distinctive gravity low located at the front of a valley glacier that once flowed into glacial lake aniuk formerly lake noatak in the western brooks range geologic and geophysical data suggest that sediments or ice filling a glacially excavated valley are the most probable cause of the 30 50 mgal anomaly reasonable choices of geometric models and density contrasts indicate that the former excavation is now filled with a buried ice thickness of 700 m or sediment thicknesses greater than 1 km comparable anomalies are not known for other glaciated lacustrine valleys however many fiords do exceed 1 km in depth and crary found one nearly 2 km deep in antarctica in studying this fiord he suggested the probable increased efficiency of excavation directly behind the point where an outlet glacier becomes afloat to form the ross ice shelf and where it thus has a vertical component of motion and a mechanism for debris removal floating glacier ice tongues are now rare in the arctic but they exist in maritime parts of northern ellesmere island and greenland studies of ice movement environment and morphology of another large floating glacier tongue in a perennially frozen lake in the angiussaq mountains of northern greenland suggest that pleistocene lake aniuk could have had a similar environment water temperature and near stable water level and that it could have maintained both a floating polar glacier tongue and a perennial ice cover no direct evidence of efficient excavation was observed in greenland but efficient glacial erosion behind a floating polar ice tongue could explain the excavation that caused the alaskan gravity anomaly

hydrogeology of two saskatchewan tills ii occurrence of sulfate and implications for soil salinity abstract the occurrence of sulfate salts in groundwater and solids was documented at two sites named dalmeny and warman where clayey tills overlie regional aquifers at dalmeny the till is thinner and approximately two orders of magnitude more permeable than at warman samples for sulfur and sulfate determinations were collected to depths of approximately 14 m and at horizontal spacings of a few tens of meters large numbers of indirect measurements of bulk salt content were obtained with a noncontacting earth conductivity meter results showed that the bulk sulfur and sulfate contents of solids could not in general be adequately characterized with point or grab samples from boreholes at dalmeny measurements representing larger averaging volumes revealed a spatially intricate pattern of sulfate abundance and depletion which extends vertically through the oxidized and unoxidized zones of the till to the underlying aquifer similar measurements at warman suggest that sulfate variability there is limited to the oxidized zone these findings and the observed coincidence of sulfate patterns with the groundwater flow patterns documented in part i2 show that the bulk permeability of the till controls the manner in which the subsurface sulfate reservoir is affected by microtopographic focussing of surface water input conceptual analysis of the responses of these systems to various land management practices indicates that where tills are relatively permeable these practices would primarily affect the quality of groundwater recharge to underlying aquifers where tills have low permeability the same practices would have no effect on aquifer water quality but they would affect the potential for surface and soil salinization

origin and distribution of sulfate in a fractured till in southern alberta canada glacial till in a 22 km sup 2 area of the interior plains region of southern alberta canada consists of an upper brown gypsiferous weathered zone up to 20 m thick and a lower discontinuous grey nonweathered zone up to 25 m thick although the total sulfur content of the two till zones is the same 0 34 the mean total sulfate content of the weathered till 4 0 mg g sup 1 exceeds that the nonweathered till 0 8 mg g sup 1 similarities suggest that all so sub 4 sup 2 in the nonweathered till and 20 of the sulfate in the weathered till was derived from sulfate rich bedrock fragments incorporated in the till during deposition laboratory experiments and delta sup 18 o and delta sup 34 s analyses of total so sub 4 sup 2 and the sulfur forms in the two zones show that the majority of the sulfate in the weathered till was derived from the oxidation of organic s at some time after the till was deposited mass balance and flux calculations indicate that this oxidation occurred under partially saturated conditions groundwater flow simulations suggest that the water table was much lower and that a thick partially saturated zone was possible during the drier altithermal period 11 000more to 3000 years b p the following chemical processes account for the major ions that are found in the groundwater but were generated when the partially saturated zone existed the oxidation of reduced s produced so sub 4 sup 2 and h sup the h sup reacted with carbonate minerals under elevated p sub co2 with ca sup 2 loss by exchange for na sup and gypsum precipitation volume shrinkage in the weathered till resulting from these geochemical processes may have enhanced the development of fractures and caused the associated increased hydraulic conductivity less

late quaternary environments in ruby valley nevada abstract palynological data from sediment cores from the ruby marshes provide a record of environmental and climatic changes over the last 40 000 yr the modern marsh waters are fresh but no deeper than 3 m a shallow saline lake occupied this basin during the middle wisconsin followed by fresh and perhaps deep waters by 18 000 to 15 000 yr b p no sediments were recovered for the period between 15 000 and 11 000 yr b p possibly due to lake desiccation by 10 800 yr b p a fresh water lake was again present and deeper than modern conditions lasted until 6800 yr b p the middle holocene was characterized by very shallow water and perhaps complete desiccation the marsh system deepened after 4700 yr b p and fresh water conditions persisted until modern times vegetation changes in ruby valley were more gradual than those seen in the paleolimno logical record sagebrush steppe was more widespread than at present through the late pleistocene and early holocene giving way somewhat to expanded shadscale vegetation between 8500 and 6800 yr b p shadscale steppe contracted by 4000 yr b p but had greater than modern coverage until 1000 to 500 yr ago pinyon juniper woodland was established in the southern ruby mountains by 4700 yr b p

carbon dioxide respiration in the deep vadose zone implications for groundwater age dating in the deep vadose zone at the dalmeny site subsurface gas samples were collected and analyzed for co2 and the 13c and 14c ratios of that co2 high concentrations of co2 depleted in 14c near the water table necessitate the use of an open system model of calcite dissolution to match observed dissolved inorganic carbon 14c ratios just below the water table groundwater age dating models assuming closed system calcite dissolution predict incorrect groundwater age dates at the dalmeny site these results and our field observations suggest that such errors may generally occur where deep vadose generation of nonmodern co2 is not accounted for in groundwater age dating exercises

great salt lake and precursors utah the last 30 000 years sediment cores up to 6 5 m in length from the south arm of great salt lake utah have been correlated radiocarbon ages and volcanic tephra layers indicate a record of greater than 30 000 years a variety of approaches have been employed to collect data used in stratigraphic correlation and lake elevation interpretation these include acoustic stratigraphy sedimentologic analyses mineralogy geochemistry major element c o and s isotopes and organics paleontology and pollen the results indicate that prior to 32 000 year b p an ephemeral saline lake playa system was present in the basin the perennial lake which has occupied the basin since this time rose in a series of three major steps the freshest water conditions and presumably highest altitude was reached at about 17 000 year b p the lake remained fresh for a brief period followed by a rapid increase in salinity and sharp lowering in elevation to levels below that of the present great salt lake the lake remained at low elevations and divided at times into a north and south basin until about 8 000 year b p since that time with the exception of two short rises to about 1290 m the lake level has remained near the present elevation of 1280 m

late quaternary environments and biogeography in the great basin abstract plant and animal remains found in packrat neotoma spp middens and cave fill from the eastern and southern great basin region reveal the presence of subalpine conifers and boreal mammals at relatively low elevations during the late wisconsin limber pine pinus flexilis and bristlecone pine p longaeva were important in the late pleistocene plant communities throughout this region spruce picea cf engelmannii and common juniper juniperus communis were present in some of the more northerly localities and douglas fir pseudotsuga menziesii and white fir abies concolor were present in southern and eastern localities single needle pinyon pine pinus monophylla common across this region today was apparently not present north of the sheep range of southern nevada during the late wisconsin pikas ochotona cf princeps small boreal mammals present in only a few great basin mountain ranges today were common throughout the region heather voles phenacomys cf intermedius have been found in two cave fill deposits in nevada though they are unknown in the great basin today limber and bristlecone pines are generally restricted to rocky substrates in modern subalpine habitats in the great basin and this may also have been the case when these plants grew at lower elevations during the late wisconsin subalpine conifers were present on the rock outcrops sampled by the packrat middens but shrub communities perhaps dominated by sagebrush artemisia spp may have been present on alluvial valley bottom substrates forested habitats would thus have been isolated habitat islands as they are today boreal small mammals including pikas and heather voles were able to colonize the great basin mountain ranges during the late pleistocene we suggest that these mammals were able to survive in the intervening valley bottoms under a cool summer climatic regime and that continuous forest or woodland corridors were not necessary for migration

a diachronic perspective on great basin projectile point morphology from veratic rockshelter idaho abstract veratic rockshelter 10cl3 located in the birch creek valley on the northern border of the snake river plain has long been considered among the most significant prehistoric sites in southeastern idaho initially excavated by earl swanson in 1961 this site produced over a thousand stone tools from stratified contexts including hundreds of diagnostic projectile points ranging from the late paleoindian to the late prehistoric period from 13 cultural horizons this paper provides a new evaluation of the geochronology of the site using 18 new ams radiocarbon dates acquired from charcoal features sampled during the original excavation these new ages are then compared with metric analyses of diagnostic projectile points from the existing assemblage to examine diachronic variability and morphological discreteness in this artifact class to tie them to existing snake river plain and intermountain west projectile point typologies as well as answer questions about late paleoindian and archaic spear and dart point variability results indicate that 1 western stemmed tradition points at veratic date to significantly later than previously thought 9500 10 000 cal b p and have a relatively broad spectrum of morphological variability 2 elko and northern side notched points found in a middle holocene horizon 6000 cal b p are morphologically distinct from each other supporting the concept of an elko long chronology 3 elko corner notched and eared northern side notched stemmed indented base including gatecliff and possibly pinto forms humboldt and salmon river points were found together in multiple middle holocene components at veratic indicating a period of greater variability that ended with the onset of the late holocene by 3200 cal b p after which only elko corner notched forms continued

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

water and solute transfer between a prairie wetland and adjacent uplands 2 chloride cycle the quality of water in lakes and wetlands depends on the exchange of solutes with adjacent uplands in many prairie wetlands the input of water is dominated by snowmelt runoff and the outputis dominated by groundwater flow we use chloride as a tracer to quantify the mass transfer processes associated with surface runoff and groundwater flow between a wetland in saskatchewan canada and the surrounding upland snowmelt runoff transports 4 5 kg yr 1 of chloride from the upland to the wetland most of this chloride infiltrates under the wetland and moves laterally to the upland with shallow groundwater under the upland chloride moves upward in the vadose zone with soil water and accumulates near the surface as water is consumed by evapotranspiration part of this chloride mixes with snowmelt runoff and moves back to the wetland therefore chloride is cycled between the wetland and the upland at an approximate rate of 5 kg yr 1 the chloride cycle occurs within 5 6 m of the ground surface a small amount of chloride escapes from the cycle with the downward flow of groundwater into the deep aquifer the estimated flux of chloride leaving the cycle is 0 1 0 6 kg yr 1 which is of the same order of magnitude as the rate at which the catchment receives atmospheric deposition of chloride because the atmospheric input is reasonably well known over the prairie region the concentration of chloride in groundwater under recharge wetlands can be used to estimate the recharge rate of deep aquifers

hydrogeology and hydrochemistry of an aquifer aquitard system within glacial deposits saskatchewan canada abstract the hydrology and hydrochemistry of an aquifer aquitard system within glacial drift has been studied utilizing data for the aquitard as well as the aquifer the study area lies in the western glaciated plains near saskatoon saskatchewan canada hydrological and chemical processes within the overlying till control the recharge rate major ion chemistry and isotopic composition of the water in the aquifer the bedrock is hydraulically isolated from the system and does not affect the groundwater chemistry reaction products generated in the till are fed into the aquifer by advection and diffusion the aquifer acts as a chemically inert lateral transmission and mixing zone hydrochemical patterns in the aquifer are regional in extent and appear to be related to the geochemical conditions within the till and the flow pattern in the aquifer the system is evolving geochemically on a time scale of thousands of years

permafrost heat flow and the geothermal regime at prudhoe bay alaska temperature measurements through permafrost in the oil field at prudhoe bay alaska combined with laboratory measurements of the thermal conductivity of drill cuttings permit an evaluation of in situ thermal properties and an understanding of the general factors that control the geothermal regime a sharp contrast in temperature gradient at approx 600 m represents a contrast in thermal conductivity caused by the downward change from interstitial ice to interstitial water at the base of permafrost under near steady state conditions interpretation of the gradient contrast in terms of a simple mode for the conductivity of an aggregate yields the mean ice content approx 39 and thermal conductivities for the frozen and thawed section 8 1 and 4 7 mcal cm s sup 0 c respectively these results yield a heat flow of approx 1 3 hfu which is similar to other values on the alaskan arctic coast the anomalously deep permafrost is a result of the anomalously high conductivity of the siliceous ice rich sediments curvature in the upper 160 m of the temperature profiles represents a warming of approx 1 8 sup 0 c of the mean surface temperature and a net accumulation of 5 6 kcal cm sup 2 by the solid earth surface during the last 100 years or so rising sea levelmore and thawing of ice rich sea cliffs probably caused the shoreline to advance tens of kilometers in the last 20 000 years inundating a portion of the continental shelf that is presently the target of intensive oil exploration a simple conduction model suggests that this recently inundated region is underlain by near melting ice rich permafrost to depths of 300 500 m its presence is important to seismic interpretations in oil exploration and to engineering considerations in oil production with confirmation of the permafrost configuration by offshore drilling heat conduction models can yield reliable new information on the chronology of arctic shorelines less