quaternary aminostratigraphy of mississippi valley loess five pleistocene loess units in the mississippi valley that contain terrestrial gastropod fossils are differentiated by amino acid ratios aile ile values in the total acid hydrolysate of the fossil terrestrial gastropods hendersonia occulta catinella and succinea late wisconsin peoria loess which has been independently dated by radiocarbon and thermoluminescence methods is identified by alle ile values in fossil gastropods which progressively increase from northern illinois to southern louisiana early to middle wisconsin roxana silt is characterized by alle ile values in hendersonia only slightly greater and values in catinella and succinea distinctly greater than those of the peoria loess aiie ile values in hendersonia suggest that the chinatown silt informal term in illinois and the loveland silt in arkansas are the same age independent geologic evidence suggests that they predate the sangamon last interglacial aile ile values in hendersonia from the sicily island loess informal term in louisiana indicate that it is significantly older than the loveland silt and the chinatown silt the oldest loess unit recognized by alle ile values in hendersonia from the mississippi valley is the county line silt informal term in illinois the study shows that amino acid ratios in fossil gastropods from loess are an extremely valuable relative age indicator and provide a means of long distance correlation of midcontinent loess deposits

amino acid estimates of latitudinal temperature gradients and geochronology of loess deposition during the last glaciation mississippi valley united states principles of amino acid paleothermometry are used to estimate paleotemperatures and latitudinal temperature gradients for the period during and following the last glacial maximum in the mississippi valley gastropod shells were collected from the peoria loess for amino acid analysis and arrhenius parameters of isoleucine epimerization were determined experimentally for the gastropod genera catinella and hendersonia there are 37 radiocarbon and 5 thermoluminescence ages that constrain the paleotemperature estimates and provide additional chronological data for loess deposition in the region amino acid paleotemperature estimates suggest that the north south temperature gradient was significantly depressed in the mississippi valley for a considerable period during the past 25 k y effective diagenetic temperature estimates indicate that at some time during or following the last glaciation the effective temperature gradient was 0 3 0 6 c degree of latitude which is significantly lower than the modern mean annual air temperature gradient of 0 9 c degree of latitude calculated effective paleotemperatures for three localities in tennessee and mississippi suggest that temperatures were 7 13 c lower than present during the period from ca 24 to 16 ka in the lower mississippi valley these results provide additional evidence for a significant cooling in southern united states continental temperatures during the last glacial maximum

a full glacial biota from southeastern iowa usa wisconsinan full glacial silts filling a swale exposed in conklin quarry johnson co iowa contain a large and diverse biota that includes pollen bryophytes vascular plant macrofossils small mammals molluscs and insects radiocarbon dates on wood from the top middle and bottom of the swale fill respectively were 16710 270 17 170 205 and 18090 190 yr bp the pollen diagram is dominated by picea spruce pinus pine and cyperaceae sedge and it records low pollen accumulation rates plant macrofossils include a number of tundra species along with picea and larix larch needles and small pieces of wood the insect fauna contains many species now confined to the forest tundra transition zone of northwestern yukon and alaska small mammals include the tundra indicators dicrostonyx collared lemming and probably microtus miurus singing vole together with boreal forest taxa the molluscs include extinct and relict species and show the widest range in present geographic distribution but rocky mountain and especially northern elements predominate in the swale fill all these lines of evidence lead to consistent palaeoclimato logical interpretation and palaeoecological reconstruction the dominant habitats represented by the biota and sedimentary environment collectively included open calcareous silty to sandy or gravelly upland sites minerotrophic fens wetlands pond or stream side clayey to sandy shores and shallow possibly ephemeral cold clear water ponds mean july temperatures were probably 11 to 13 c cooler than at present the biota indicates that a picea larix krummholz with extensive tundra openings was present in southeastern iowa between 18090 and 16710 yr bp

a baseline survey of the distribution and origin of platinum group elements in contemporary fluvial sediments of the kentish stour england the extensive anthropogenic use of the platinum group elements pge ru rh pd os ir and pt is the main factor responsible for the widespread dispersion of these elements throughout the environment significant quantities of the pge enter fluvial systems via road runoff storm drains and wastewater and sewage treatment systems and may accumulate in fluvial sediments by physical and chemical processes a baseline survey of contemporary fluvial sediments in the kentish stour river east kent england has been undertaken to document the sources and distribution of anthropogenic pge in an attempt to constrain some of the physical and chemical parameters that may influence the distribution of these elements the geology of the catchment of the kentish stour is dominated by carbonate and silicate sedimentary rocks and the river passes through urban and rural land and receives inputs of waste from sewage works nine sedimentary rocks 4 motorway runoff sediments and 22 river sediments were analysed for pge by nis fire assay preconcentration and icp ms the highest element abundances occur in the motorway runoff sediments maximum total pge content of 55 ng g whilst the lowest values were recorded in the sedimentary rocks where some samples contain pge at concentrations below the limit of detection the total pge content of the river sediments ranged from 0 4 to 10 8 ng g the distribution and variation in concentrations and ratios of the pge in the contemporary fluvial sediments of the kentish stour correspond strongly with land use changes urban versus rural and with points of discharge from sewage works the absence of a pure catalytic converter signature in the river sediments however indicates that source signatures may be mixed in sewage works or that pge may chemically fractionate in the fluvial environment

palaeoenvironmental reconstructions using the modern analogue technique the effects of sample size and decision rules palaeoenvironmental information is often extracted from pollen records using the modem analogue technique mat it is largely unknown how sensitive the mat is to subsampling induced variation in pollen assemblages or to the decision rules used to reconstruct climate and vegetation we examine these issues in a monte carlo framework in which simulated pollen assemblages at eight count sizes were created from four fossil pollen assemblages simulated and fossil assemblages are compared with modern data sets at squared chord distance cut off values between 0 05 and 0 55 to 1 quantify count size induced variation in pollen assemblages and 2 determine how count size induced variation affects analogue selection and climate reconstruction the effects of sample size and decision rules on vegetation reconstructions are examined using two analogue selection schemes and two levels of minimum required analogues the results show that decision rules have as much impact on reconstruction precision and accuracy

aminostratigraphic correlation and geochronology of two quaternary loess localities central mississippi valley abstract amino acid epimeric aile ile values from terrestrial molluscs are used to define and correlate three aminozones in loess sequences exposed across the central mississippi valley in arkansas and tennessee three superposed aminozones are defined at wittsburg quarry arkansas primarily using aile ile values from total hydrolysates of the gastropod genus hendersonia peoria loess aile ile 0 07 0 01 roxana silt 0 14 0 02 and a third loess 0 28 0 06 loess units at wittsburg quarry can be correlated on lithologic characteristics eastward across the mississippi valley to the old river section near memphis tennessee however only one loess unit is fossil bearing peoria loess aile ile 0 05 at that section radiocarbon analyses of charcoal from the upper roxana silt ca 26 000 to 29 000 yr old and mollusc shell carbonate from the basal roxana silt ca 39 000 yr old are used to calibrate amino acid epimeric data for the central mississippi valley these data applied to the apparent parabolic kinetic model of r m mitterer and n kriausakul 1989 quaternary science reviews 8 353 357 suggest an illinoian 120 000 yr age for the third loess in the central mississippi valley that is correlative with part of the loveland loess in illinois and iowa

late pleistocene evolution of the lower mississippi river valley southern missouri to arkansas the mississippi river served as the principal conduit for meltwaters discharging from the southern margins of north american ice sheets the northern half of the mississippi river alluvial valley in missouri and arkansas can be subdivided into two distinct channel courses the western and eastern lowlands which are separated by crowleys ridge the eastern lowlands contain two entry points the bell city oran and thebes gaps the latter is a narrow bedrock gorge that contains the modern river this paper summarizes a model for evolution of channel courses in the western and eastern lowlands during the illinoian and wisconsin glacial stages for the western lowlands stratigraphic relations between loess units and subjacent fluvial deposits show that major continuous terrace surfaces or valley trains are illinoian or late wisconsin in age investigations of tributary valley fills further show the western lowlands were deeply incised during the early to middle wisconsin stage then aggraded during the late wisconsin stage to such an extent that tributary valleys were backfilled with slackwater deposits moreover analysis of loess thinning and fining trends shows that early to middle wisconsin roxana silt and the late wisconsin peoria loess covers on western lowlands valley trains were derived from deflation of valley trains in the eastern lowlands we conclude that the western lowlands were the primary mississippi river course during illinoian deglaciation but were abandoned shortly thereafter then episodically reoccupied during the late wisconsin stage for the eastern lowlands course valley trains of early to middle wisconsin age are not preserved with the exception of a small remnant where the mississippi river broke through a gap in the southern margins of crowleys ridge and reentered the western lowlands all valley trains in the eastern lowlands are late wisconsin age a series of discontinuous terrace surfaces in the bell city oran gap represent dissected remnants of the primary late wisconsin full glacial and early late glacial course of the mississippi river or combined mississippi and ohio rivers whereas younger continuous braided stream surfaces in the bell city oran and thebes gap courses represent valley trains of latest wisconsin and earliest holocene age hence the bell city oran gap was the primary course during the entire wisconsin stage and the thebes gap was permanently occupied in earliest holocene time as much as 5 m difference in elevation between successive late wisconsin terrace surfaces of the eastern lowlands indicates that valley trains were rapidly constructed incised and abandoned in response to fluctuations in the delivery of meltwater and outwash from the former ice margin moreover a variety of data indicates that deglacial meltwater floods were commonly of sufficient magnitude to overflow from the primary course in the bell city oran gap throughout the late wisconsin substage floodwaters overflowed into the western lowlands constructed a series of secondary valley trains and filled tributary valleys with slackwater deposits during the latest wisconsin stage perhaps in association with the drainage of glacial lake agassiz floodwaters overflowed into the western lowlands and broke through the thebes gap the charleston fan represents the initial deposits of the thebes gap course following deposition of a large crevasse splay at the western lowlands entrance that course was no longer active but flow was routed through the thebes gap during periods of high magnitude flooding until the bell city oran gap was abandoned and the thebes gap course was permanently occupied during earliest holocene time

vegetation and environment in eastern north america during the last glacial maximum abstract knowledge of the vegetation and environment of eastern north america during the last glacial maximum lgm is important to understanding postglacial vegetational and biogeographic dynamics assessing climate sensitivity and constraining and evaluating earth system models our understanding of lgm conditions in the region has been hampered by low site density problems of data quality particularly dating and the possibility that lgm vegetation and climate lacked modern analogs in order to generate improved reconstructions of lgm vegetation and environment we assembled pollen and plant macrofossil data from 21 and 17 well dated lgm sites respectively all sites have assemblages within the lgm timespan of 21 000 1500 calendar yr bp based on these data we prepared maps of isopolls macrofossil presence absence pollen analogs biomes inferred mean january and july temperatures and mean annual precipitation for the lgm tundra and open picea dominated forest grew along the laurentide ice sheet with tundra predominantly in the west in the east pinus dominated vegetation mainly p banksiana with local p resinosa and p strobus occurred extensively to 34 n and possibly as far south as 30 n picea glauca and a now extinct species p critchfieldii occurred locally picea dominated forest grew in the continental interior with temperate hardwoods quercus carya juglans liriodendron fagus ulmus growing locally near the lower mississippi valley at least as far north as 35 n picea critchfieldii was the dominant species in this region the florida peninsula was occupied by open vegetation with warm temperate species of pinus eastern texas was occupied by open vegetation with at least local quercus and picea extensive areas of peninsular florida and the continental interior had vegetation unmatched by any modern pollen samples the paleovegetational data indicate more extensive cooling in eastern north america at the lgm than simulated by either the ncar ccm0 or ccm1 climate models the occurrence of cool temperate conifers and hardwoods as far north as 34 35 n however indicates less severe cooling than some previous reconstructions paleoclimate inferences for the lgm are complicated by lowered atmospheric co 2 concentrations which may be responsible for the open nature and dominance of conifers in lgm vegetation

loess stratigraphy of the lower mississippi valley abstract loesses of the lower mississippi valley lmv are world famous sir charles lyell 1847 hilgard 1860 stafford 1869 call 1891 and mabry 1898 thought the lmv loess was a single water deposit although double submergence was noted by call 1891 and salisbury 1891 shimek 1902 and emerson 1918 recognized lmv loess as a wind deposit which came from the valley although wind deposited loess gained wide acceptance russell 1944a published his controversial theory of loessification which entailed weathering of backswamp deposits downslope movement and recharge by carbonates to form loess wascher et al 1947 identified three lmv loesses mapped distributions and strongly supported eolian deposition leighton and willman 1950 identified four loesses and supported eolian deposition as did krinitzsky and turnbull 1967 and snowden and priddy 1968 but krinitzky and turnbull questioned the deepest loess daniels and young 1968 and touchet and daniels 1970 studied the distribution of loesses in south central louisiana west et al 1980 and rutledge et al 1985 studied the source areas and wind directions which deposited the loesses on and adjoining crowley s ridge b j miller and co workers miller et al 1985 1986 miller and alford 1985 proposed that the loveland silt was early wisconsin rather than illinoian age and advanced the name sicily island loess they proposed the underlying loess was illinoian and advanced the name crowley s ridge we termed the loesses from the surface downward peoria loess roxana silt loveland sicily island loess crowley s ridge loess and marianna loess researchers agree that the surfical peoria loess is late wisconsin and the roxana silt is late to middle wisconsin but little agreement exists on the age of the older loesses pye and johnson 1988 proposed early wisconsin for the loveland sicily island mckay and follmer 1985 suggested this loess correlated with a loess under illinoian till clark et al 1989 agreed on crowley s ridge but suggested the loveland sicily island loess on sicily island was older mirecki and miller 1994 and millard and maat 1994 suggested an illinoian age for the loveland sicily island loess miller and co workers suggested as did pye and johnson 1988 an illinoian age for the crowley s ridge loess mckay and follmer 1985 suggested it correlated with a loess under kansan till stratigraphy indicates the marianna is the older of the five loesses researchers identified loess on both the east and west side of the lmv as well as on higher terraces within the valley many researchers assumed unaltered loesses were commonly yellowish brown and silts or silt loams west et al 1980 miller et al 1986 the nonclay fraction of unweathered lmv loesses was dominated by quartz followed corresponding author by carbonates mainly dolomites followed by feldspars and micas clays were dominated by montmorillonite followed by micaceous minerals kaolinite and vermiculite miller et al 1986 soils in the crowley s ridge loess are most developed followed by the soils in the loveland sicily island which are more developed than the modern soils in the peoria loess soils in the roxana and marianna loesses are least developed and the farmdale soil of the roxana is the weaker of the two miller et al 1986 there is certainly overlapping range in the degree of soil development in the various loesses

age and significance of fossil white spruce picea glauca tunica hills louisiana mississippi abstract radiocarbon dates indicate a farmdalian through woodfordian age for fossil white spruce picea glauca in the tunica hills a greater time span than previously documented these dates furthermore require revision of the ages of fluvial terrace deposits in the region spruce bearing terrace 1 sediments previously regarded as late woodfordian to holocene age are of farmdalian to late holocene age terrace 2 sediments previously assigned a sangamonian or farmdalian age are of probable altonian age plant fossils in terrace 1 sediments represent two climatically and temporally distinct assemblages a cool temperate farmdalian woodfordian assemblage dominated by white spruce but including deciduous hardwoods suggestive of an oak hickory association and a warm temperate holocene assemblage composed of southern hardwoods and nonarboreal species representative of the modern flora of the tunica hills locally fossils of white spruce have been reworked into younger terrace 1 sediments containing the warm temperate plant assemblage the transition from the cool temperate flora to the modern warm temperate flora in the tunica hills probably occurred around 12 000 yr b p

assessment of multiple sources of anthropogenic and natural chemical inputs to a morphologically complex basin lake mead usa abstract lakes with complex morphologies and with different geologic and land use characteristics in their sub watersheds could have large differences in natural and anthropogenic chemical inputs to sub basins in the lake lake mead in southern nevada and northern arizona usa is one such lake to assess variations in chemical histories from 1935 to 1998 for major sub basins of lake mead four sediment cores were taken from three different parts of the reservoir two from las vegas bay and one from the overton arm and virgin basin and analyzed for major and trace elements radionuclides and organic compounds as expected anthropogenic contaminant inputs are greatest to las vegas bay reflecting inputs from the las vegas urban area although concentrations are low compared to sediment quality guidelines and to other usa lakes one exception to this pattern was higher hg in the virgin basin core the virgin basin core is located in the main body of the lake colorado river channel and is influenced by the hydrology of the colorado river which changed greatly with completion of glen canyon dam upstream in 1963 major and trace elements in the core show pronounced shifts in the early 1960s and in many cases gradually return to concentrations more typical of pre 1960s by the 1980s and 1990s after the filling of lake powell the overton arm is the sub basin least effected by anthropogenic contaminant inputs but has a complex 137 cs profile with a series of large peaks and valleys over the middle of the core possibly reflecting fallout from nuclear tests in the 1950s at the nevada test site the 137 cs profile suggests a much greater sedimentation rate during testing which we hypothesize results from greatly increased dust fall on the lake and virgin and muddy river watersheds the severe drought in the southwestern usa during the 1950s might also have played a role in variations in sedimentation rate in all of the cores

deglacial hydroclimate of midcontinental north america abstract during the last deglaciation temperatures over midcontinental north america warmed dramatically through the bolling allerod underwent a cool period associated with the younger dryas and then reverted to warmer near modern temperatures during the early holocene however paleo proxy records of the hydroclimate of this period have presented divergent evidence we reconstruct summer relative humidity rh across the last deglacial period using a mechanistic model of cellulose and leaf water 18o and d combined with a pollen based temperature proxy to interpret stable isotopes of sub fossil wood midcontinental rh was similar to modern conditions during the last glacial maximum progressively increased during the bolling allerod peaked during the younger dryas and declined sharply during the early holocene this rh record suggests deglacial summers were cooler and characterized by greater advection of moisture laden air masses from the gulf of mexico and subsequent entrainment over the mid continent by a high pressure system over the laurentide ice sheet these patterns help explain the formation of dark colored cumulic horizons in many great plains paleosol sequences and the development of no analog vegetation types common to the midwest during the last deglacial period likewise reduced early holocene rh and precipitation correspond with a diminished glacial high pressure system during the latter stages of ice sheet collapse

relationship of two lacustrine ostracode species to solute composition and salinity implications for paleohydrochemistry nonmarine ostracode species are indicative of the physical and chemical nature of lacustrine environments although salinity has traditionally been regarded as one of the more important parameters that affect the occurrence patterns of lacustrine ostracodes examination of the solute composition and salinities of the lakes where limnocythere sappaensis and l staplini live reveals that solute composition and not salinity is the most critical factor that controls their occurrence the occurrence of these taxa in the modern world is mutually exclusive l sappaensis lives in water that is enriched in na hco 3 and depleted in ca 2 l staplini lives in water that is enriched in various combinations of na mg 2 ca 2 cl and is depleted in hco 3 these solute compositions are the product of the mineral fractionation processes described by eugster and hardie the positive correlation between these two species occurrences and the mineralogic fractionation processes suggests that these taxa may be used as reliable paleohydrochemical indicators studies in progress dealing with other ostracode taxa suggest that saline lacustrine ostracodes can provide a precise method for reconstructing paleohydrochemistry

stratigraphy and chronology of mississippi valley loess in western tennessee the stratigraphy and chronology of loess deposits in the mississippi valley provide an important proxy record of the number and timing of glacial advances into the upper mississippi drainage basin the stratigraphy of loess and paleosols from two exposures in northwestern tennessee reveals three major loess units that are correlated with the loveland loess roxana silt and peoria loess from oldest to youngest detailed measurements of clay and secondary pedogenic iron contents suggest that the loveland loess may consist of multiple loess units which have been pedogenically welded to one another to form a composite sangamon soil the mineralogy of the coarse silt fraction from one exposure reveals both primary mineralogical differences between the peoria loess and the roxana silt and pedogenic overprinting by the sangamon soil grain size and iron data suggest that the degree of pedogenic alteration increases from west to east away from the loess source area which probably reflects the role of sedimentation rate on the degree of pedogenic alteration of loess however only the peoria loess shows the expected exponential eastward decrease in thickness the thickness of older loess units appears to be controlled more by the occurrence of localized erosion than by distance from source area most samples are resistant to solar resetting of the thermoluminescence signal which if unrecognized could yield thermoluminescence ages that significantly underestimate the true age of the deposits the best match between thermoluminescence age using the total bleach method and radiocarbon age of the peoria loess and roxana silt is achieved when either long durations of optical bleaching by sunlight 32 hr or artificial ultraviolet uv light are applied to define the residual thermoluminescence level partial bleach analysis indicates that long duration optical bleaching by sunlight or uv lamp bleaching does not systematically overbleach samples of peoria loess and roxana silt three thermoluminescence age estimates between 38 4 1 and 53 5 ka from the basal half of the roxana silt and six age estimates between 18 2 and 25 3 ka from the basal half of the peoria loess are consistent with numerous finite radiocarbon dates from around the central mississippi valley thermoluminescence age estimates suggest that the oldest of the intra loveland loess units is 127 12 ka one age and may have been deposited during marine oxygen isotope stage 6 the younger two of these loess units were deposited between 113 10 and 70 6 ka three ages this latter age range for loess that underlies the top of the presumed sangamon soil is problematic because it requires that pedogenesis may have begun as late as approximately 70 ka moreover loess deposited between about 120 and 70 ka suggests that the southern margin of the laurentide ice sheet was within some part of the upper mississippi valley during this interval this conflicts with some glacial geologic evidence but it is consistent with global sea level and 18o records of ice volume which indicate several intervals of moderate glaciation during this time

late quaternary paleoecology and paleoenvironments of the central mississippi alluvial valley a radiocarbon dated sediment core from powers fort swale located in the western lowlands of southeastern missouri provides sedimentological and palynological evidence for dynamic changes in fluvial regime and vegetation in the central mississippi alluvial valley during the late pleistocene and holocene intervals during the late wisconsinan glacial maximum glacial meltwater carried by the mississippi river maintained active braided streams sand grains in full glacial and late glacial sediments of powers fort swale show evidence of reworking by eolian activity with late pleistocene formation of sand dunes continuing until 11 600 yr b p within the western lowlands the sedimentological sequence indicates a progressive stepwise loss of glacial meltwater and coarse sediment supply during the late glacial interval resulting in abandonment of braided stream terraces the initial partial diversion of mississippi river flow occurred in the late glacial interval possibly as early as 16 300 yr b p as the mississippi river shifted from the western lowlands through the bell city oran gap in crowleys ridge and into the eastern lowlands by 14 500 yr b p the complete diversion of meltwater through this gap coincided with a change in the powers fort sediment core from a spruce dominated to an oak dominated pollen assemblage at 11 500 yr b p sedimentological changes reflected a changeover to a meandering river regime the transition to pollen assemblages characteristic of holocene temperate swamp forest occurred at 9500 yr b p

extinction and survival of plant life following the cretaceous tertiary boundary event western interior north america the palynological cretaceous tertiary boundary is recognized in the northern part of the western interior by the abrupt disappearance of a few characteristic cretaceous pollen genera principally proteacidites and aquilapollenites in the southern part the boundary is recognized by the disappearance of a somewhat different group of pollen proteacidites tilia wodehousei and trisectoris the abrupt change in both regions takes place precisely at the stratigraphic horizon at which boundary clay layers containing anomalously high concentrations of iridium interpreted to be the result of an asteroid impact are found although some characteristic cretaceous taxa apparently became extinct others were minimally affected by this boundary event and reappear in strata above however all the principal cretaceous pollen genera though not species that disappear regionally have been reported from tertiary rocks in other parts of north america differential apparent extinction and or survival reflects a pronounced temporary disruption of plant life immediately after the event some cretaceous plants must have persisted in refugia to have provided the propagules for the rapid recovery of the flora no massive total extinction of plant genera at the end of the cretaceous can be seen from the palynologic record

developing the scientific framework for urban geochemistry abstract urban geochemistry is a unique discipline that is distinguished from general geochemistry by the complex infrastructure and intense human activities associated with concentrated population centers as stated by thornton 1991 this subject is concerned with the complex interactions and relationships between chemical elements and their compounds in the urban environment the influence of past and present human and industrial activities on these and the impacts or effects of geochemical parameters in urban areas on plant animal and human health urban areas present special challenges to geochemists attempting to understand geochemical states and fluxes on the 5 6 of august 2014 the first meeting of the reorganized urban geochemistry working group of the international association of geochemistry iagc was held in columbus ohio united states two goals of the meeting were to develop the overall scope and a general definition of urban geochemistry five grand themes were developed 1 recognizing the urban geochemical signature 2 recognizing the legacy of altered hydrologic and geochemical cycles in urban environments 3 measuring the urban geochemical signature 4 understanding the urban influence on geochemical cycles from the continuous development and erosion of physical infrastructure and episodic perturbations and 5 relating urban geochemistry to human and environmental health and policy after synthesizing the discussion of these themes we offer the following perspective on the science of urban geochemistry building on the work of thornton 1991 urban geochemistry as a scienti c discipline provides valuable information on the chemical composition of environments that support large populations and are critical to human health and well being research into urban geochemistry seeks to 1 elucidate and quantify the sources transport transformations and fate of chemicals in the urban environment 2 recognize the spatial and temporal including legacies variability in these processes and 3 integrate urban studies into global perspectives on climate change biogeochemical cycles and human and ecosystem health we hope that this discussion will encourage other geochemists to engage in challenges unique to urban systems as well as provide a framework for the future of urban geochemistry research

historical developments and recent advances in amino acid geochronology applied to loess research examples from north america europe and china abstract amino acid geochronology provides important chronostratigraphic insight in the regional correlation and paleoclimatic evaluation of loess paleosol sequences in the midwestern us throughout western central and eastern europe and in china in general loess of the last four glacial cycles corresponding to marine oxygen isotope stages ois 2 4 6 8 and 10 respectively can be distinguished on the basis of alloisoleucine isoleucine a i ratios measured in fossil gastropod shells preserved in the loess the racemization reaction is much slower in older samples resulting in decreased temporal resolution in the midwestern us and europe it is not possible to confidently subdivide the last glacial cycle on the basis of aminostratigraphic data however in china where effective temperatures were higher during the late pleistocene loess above and below l1ss1 the ois 3 interstadial paleosol can be distinguished using amino acid racemization data with improvements in analytical methods multiple amino acid d l enantiomers are now being measured using reverse phase liquid chromatography aspartic acid racemizes at a higher rate than the traditionally measured alloisoleucine isoleucine diastereomers and can be measured more rapidly this development offers hope for better temporal resolution and enhanced stratigraphic subdivision of loess units than has been achieved previously

paleoecology of central kentucky since the last glacial maximum pollen grains and spores plant macrofossils and sponge spicules from a 7 2 m sediment core from jackson pond dating back to 20 000 yr b p are the basis for new interpretations of vegetational limnological and climatic changes in central kentucky during the full glacial interval 20 400 to 16 800 yr b p upland vegetation was closed spruce forest with jack pine as a subdominant aquatic macrophyte and sponge assemblages indicate that the site was a relatively deep open pond with low organic productivity during late glacial time 16 800 to 11 300 yr b p spruce populations continued to dominate while jack pine declined and sedge increased as the vegetation became a more open taiga like boreal woodland between 11 300 and 10 000 yr b p abundances of spruce and oak pollen oscillated reciprocally possibly reflecting the younger dryas oscillation as boreal taxa underwent a series of declines and increases at the southern limit of their ranges before becoming extirpated and replaced by deciduous forest in the early holocene 10 000 to 7300 yr b p a mesic deciduous woodland developed it was replaced by xeric oak hickory forest during the middle holocene between 7300 and 3900 yr b p grass increased after 3900 yr b p indicating that the presettlement vegetation mosaic of mixed deciduous forest and prairie the kentucky barrens became established in central kentucky after the hypsithermal interval sponge spicules increased in number during the holocene reflecting reduced water depths in the pond sediment infilling as well as climatic warming and the expansion of fringing shrub thickets increased nutrient and habitat availability for freshwater sponges

a multi proxy palaeoecological and palaeoclimatic record within full glacial lacustrine deposits western tennessee usa the fulton section along the mississippi river in western tennessee usa is a 1 km continuous exposure 20 m vertically of quaternary fluvial and lacustrine deposits inset within eocene sediments and buried by thick loess fossiliferous slackwater lake sediments record maximum aggradation during the last two major glaciations with deposition between ca 190 140 ka and q1 24 18 14 c ka bp based on amino acid and radiocarbon chronology respectively during the onset of full glacial conditions ca 24 22 14 c ka bp a relatively permanent shallow lake environment is indicated by ostracodes aquatic molluscs and both pollen and macrofossils of aquatic plants by 21 8 14 c ka bp increasing emergent plants amphibious gastropods pomatiopsis and heavier d 18 o compositions suggest marsh like conditions in a periodically drying lake the surrounding uplands consisted of picea pinus woodlands mixed with cool temperate hardwoods e g quercus populus carya grasses and herbs more open conditions ensued ca 20 14 c ka bp with loess and slopewash gradually infilling the former lake by 18 14 c ka bp modern analogue analyses of ostracodes and palaeontological evidence imply a full glacial climate similar to today s mixed boreal zone in central minnesota usa about 98c cooler in mean annual temperature than present day western tennessee copyright 2009 john wiley sons ltd

the timing and nature of late quaternary vegetation changes in the northern great plains usa and canada a re assessment of the spruce phase abstract this paper revises the chronology for the northward migration of picea glauca white spruce across the northern great plains following the recession of the laurentide ice sheet and reinterprets the species composition and structure of the late glacial vegetation on the basis of pollen and plant macrofossil analysis the timing of spruce migration is based on 26 14 c ages obtained from picea macrofossils the date for the appearance of white spruce in southern south dakota usa remains unchanged 12 600 14 c yr bp ca 15 000 cal yr bp but its arrival in southern saskatchewan canada by 10 300 14 c yr bp ca 12 100 cal yr bp is about 1500 years later than previously estimated based on an organic sediment date picea glauca thus migrated northwards at an average rate of 0 38 km 14 c year 0 30 km calendar year significantly slower than the previously published rate of 2 km 14 c year white spruce trees probably inhabited lake shorelines whereas prairie parkland and boreal plants occupied both lowlands and uplands forming an open white spruce parkland this interpretation differs from a previous reconstruction of a boreal type spruce forest and thus offers another paleoclimatic interpretation precipitation was probably low and summer temperatures relatively mild averaging about 19 c

the contribution of agricultural and urban activities to inorganic carbon fluxes within temperate watersheds abstract the lateral transport of bicarbonate as dissolved inorganic carbon dic to the oceans is an integral component of the global carbon budget and can represent the sequestration of co 2 from the atmosphere recently studies have implicated land use change in particular agricultural development as an accelerator of bicarbonate export however due to the co variation of land use bedrock and surficial geologies and the relationship between bicarbonate export and climate the impact of anthropogenic activities on dic export remains an important research question in order to examine the land use controls on dic export from small temperate watersheds we sampled 19 streams draining catchments of varying land uses with similar bedrock and surficial geologies in addition to an agricultural effect there was a strong correlation between the percent of watershed in urban development and dic concentrations and dic yields urban watersheds exported 7 8 times more dic than their nearby forested counterparts and 2 0 times more dic than nearby agricultural catchments isotopic data suggest that excess dic export from altered systems results from increased chemical weathering enhanced co 2 production within urban green spaces and as a result of organic matter loading from septic systems and leaky sewer lines furthermore we found that nitrogen additions e g fertilizers and manure are aiding in the dissolution of lime increasing the total export of dic from agricultural watersheds calculated anthropogenic loading rates ranged from 0 43 to 0 86 mol c m 2 yr 1 these loading rates suggest that a significant portion of global dic export might be attributable to human activities although the impacts on co 2 sequestration are difficult to determine

cyanobacteria proliferation in the cenomanian turonian boundary interval of the apennine carbonate platform immediate response to the environmental perturbations associated with oae 2

late wisconsinan vegetation and environment of the tunica hills region louisiana mississippi abstract pollen plant macrofossil and radiocarbon dating studies of seven exposures of fluvial sediments in the tunica hills region of southeastern louisiana and southwestern mississippi provide new information on late wisconsinan vegetation flora and environment of the region the assemblages date between 25 250 and 17 530 yr b p pollen and macrofossil assemblages are dominated by picea which comprises 40 70 of the pollen assemblages abies and larix pollen and macrofossils are absent in contrast to sites to the north in the central mississippi valley deciduous hardwoods quercus fagus fraxinus carya juglans nigra acer ulmus are minor components of both pollen and macrofossil assemblages radiocarbon dates of picea and quercus wood indicate that these two genera grew contemporaneously in the region regional upland forests were dominated by picea picea cones and cone fragments are not typical of any extant north american species and probably represent either an extinct species or an extinct variety or subspecies of picea glauca late wisconsinan climate of the region was cooler than present but not necessarily as cool as implied by p glauca or other boreal taxa

environmental geochemistry 40years research at imperial college london uk abstract this paper reviews the development of multi purpose geochemical mapping and the progress of research in applied environmental geochemistry and health at imperial college over the past 40 years with funding from the research councils uk government eu industry and ngos research has provided the basis for postgraduate training in areas ranging from the applications of geochemistry to plant agricultural livestock and wildlife nutrition to evaluating contamination from metalliferous mining and smelting understanding the chemical nature of the urban environment and relationships between geochemistry and human health and disease examples include 1 the influence of mo in marine black shales on the cu nutrition of grazing cattle and sheep 2 the importance of soil ingestion on trace element intake and metabolism and metal exposure in farm livestock 3 the impacts of soil contamination from historical metalliferous mining and smelting on agriculture and human exposure to metals including potential health problems from cd at shipham and from as in sw england 4 the growth of urban geochemistry and the importance of pb in the urban environment 5 the health impacts due to hg losses from the informal sector au mining in brazil and 6 health issues relating to f excess and se deficiency in china

quaternary highstands in bear lake valley utah and idaho surficial deposits in bear lake valley utah and idaho demonstrate that bear lake and its surrounding wetlands expanded and contracted several times during the quaternary period deposits in 40 outcrops and the geomorphology of the valley were studied to reconstruct the water level history temporal control was provided by amino acid geochronology on 29 samples of aquatic mollusks calibrated by 14 c dating and tephrochronology samples of three molluscan genera were heated and analyzed to determine intergeneric differences in aspartic asp and glutamic glu acid racemization the covariance of asp and glu racemization in these genera was used to identify aberrant amino acid analyses the rate of glu racemization was calibrated by using a parabolic model that was used to estimate sample ages although the paucity of exposures uncertainty of the depositional setting and postdepositional uplift of deposits hamper an accurate reconstruction of water level in bear lake valley several conclusions can be drawn during the middle pleistocene lacustrine or wetland environments in northern bear lake valley may have extended up to 1830 masl meters above sea level 6000 ft twice between ca 1000 100 ka bear hollow phase during the late pleistocene the shoreline of bear lake transgressed at least three times 1 to 1817 masl 5960 ft at 47 39 cal calendar year corrected ka jensen spring phase 2 to 1814 masl 5950 ft at ca 16 15 cal ka raspberry square phase and 3 to 1814 masl at ca 9 cal ka willis ranch phase bear river currently bypasses bear lake but flowed into the lake during highstands and allowed the water level to rise to the valley threshold at nounan narrows water levels have lowered to 1806 masl 5923 ft since the middle pleistocene likely because of downcutting by bear river at nounan narrows because downcutting at nounan narrows controls the maximum attainable water level in bear lake valley effects of climate change on lake level are limited and bear lake may actually have been smaller than today when lake bonneville transgressed to its maximum shoreline during the last glacial maximum

an environmental tolerance index for ostracodes as indicators of physical and chemical factors in aquatic habitats abstract continental ostracode occurrences reflect salinity solute composition temperature flow conditions and other environmental properties of the water they inhabit their occurrences also reflect the variability of many of these environmental parameters environmental tolerance indices etis offer a new way to express the nature of an ostracode s environment as defined herein etis range in value from zero to one and may be calculated for continuous and binary variables for continuous variables such as salinity the eti is the ratio of the range of values of salinity tolerated by an ostracode to the total range of salinity values from a representative database in this investigation the database of continuous variables consists of information from 341 sites located throughout the united states binary etis indicate whether an environmental variable such as flowing water affects ostracode presence or absence the binary database consists of information from 784 sites primarily from illinois usa etis were developed in this investigation to interpret paleohydrological changes implied by fossil ostracode successions eti profiles may be cast in terms of a weighted average or on presence absence the profiles express ostracode tolerance of environmental parameters such as salinity or currents tolerance of a wide range of values is taken to indicate shallow water because shallow environments are conducive to thermal variability short term water residence and the development of currents from wind driven waves

provenance age and environment of mid wisconsinan slackwater lake sediment in the st louis metro east area usa abstract valleys tributary to the mississippi river contain fossiliferous slackwater lake sediment equality formation deposited in response to aggradation of the mississippi river valley during the last glaciation in the st louis metro east area the lower part of the equality formation is primarily laminated fossiliferous silt and clay deposited from about 44 150 to 24 310 14c yr b p the upper equality formation is primarily very fine sand to silt deposited from about 21 200 to 17 000 14c yr b p among the four cores that sample this succession in the st louis metro east area core mnk 3 38 64en 90 01ew was selected for detailed study three sources are distinguished by the following characteristics 1 gray smectite quartz se rich feldspar poor material of the des moines wadena and james lobes 2 reddish brown kaolinite cu fe rich sediment of the superior and rainy lobes and 3 brown illite dolomite sr rich sediment of the lake michigan and green bay lobes the earliest sediments 44 150 to 41 700 14c yr b p were derived from the central and western provenances and are chronocorrelative with the lower roxana silt a hiatus occurred from about 41 700 to 29 030 14c yr b p when much of the middle roxana silt meadow member was deposited on adjacent uplands the youngest sediment includes evidence of heightened activity of the superior lobe at about 29 000 14c yr b p the lake michigan and green bay lobes from about 25 000 to 24 000 14c yr b p and the wadena des moines james lobes at about 21 000 14c yr b p

sources of sulfur in the nandong underground river system southwest china a chemical and isotopic reconnaissance abstract sulfur isotopic compositions 34s and major ions were measured in groundwater and surface waters in order to elucidate the source s of elevated so 4 2 content in some of these waters in the nandong underground river system nurs located in an agricultural and urbanization dominated area in sw china the major chemical composition of analyzed groundwater and surface water from nurs was characterized by ca hco3 or ca mg hco3 type in forested and grass land areas and ca cl no3 so4 or ca mg cl no3 so4 type in urban and agricultural areas respectively the anomalously high so 4 2 concentrations in waters collected from urban and agricultural areas indicated a likely anthropogenic origin for so 4 2 the groundwater collected from forested and grass land areas was characterized by relatively low 34 s so 4 2 from 1 7 to 4 3 and low so 4 2 concentrations of less than 10 mg l 1 consistent with an origin for so 4 2 in these waters from a mixture of rainfall derived so 4 2 and so 4 2 from oxidation of bedrock sulfide high so 4 2 groundwater and surface water 20 mg l 1 collected from urban areas was characterized by elevated 34 s so 4 2 from 8 3 to 12 1 compared to lower 34 s so 4 2 in samples from cultivated land areas 3 7 to 6 4 indicating that the so 4 2 in these two groups of waters resulted from different anthropogenic sources the s isotopic composition of so 4 2 in urban areas is consistent with addition of so 4 2 from detergent sewage whilst in cultivated land areas isotope composition indicates that additional so 4 2 could be derived from fertilizers and or increased oxidation of sulfide

evidence of late glacial runoff in the lower mississippi valley abstract thousands of cubic kilometers of massive coarse grained glacial outwash underlie the alluvial plain of the lower mississippi valley between cairo illinois and the gulf of mexico however valley trains deposited by braided streams characterize less than one third of the valley area and those attributable to runoff from the laurentide ice sheet cover less than 15 000 km2 mostly in the st francis basin segment of the valley there they form a series of subdued terraces that reflect episodes of meltwater release and possibly catastrophic flood events radiocarbon dated sediment cores establish that the initial runoff entered the basin about 16 3 ka bp and continued without a significant lull for about 5000 years the distribution of archeological sites tends to support an effective brief cessation of runoff to the valley about 11 0 ka bp when meltwater is thought to have been diverted from the mississippi river valley to the st lawrence valley both radiocarbon dates and archeological evidence document a final pulse of outwash to the lower mississippi valley about 10 0 ka bp when the mississippi river occupied thebes gap near cairo and created the charleston fan all outwash deposition ended and the river adopted a meandering regime not later than 9 8 ka bp

radiocarbon calibration curve spanning 0 to 50 000 years bp based on paired 230 th 234 u 238 u and 14 c dates on pristine corals abstract radiocarbon dating is the most widely used dating technique in the world recent advances in accelerator mass spectrometry ams and sample preparation techniques have reduced the sample size requirements by a factor of 1000 and decreased the measurement time from weeks to minutes today it is estimated that more than 90 percent of all measurements made on accelerator mass spectrometers are for radiocarbon age dates the production of 14 c in the atmosphere varies through time due to changes in the earth s geomagnetic field intensity and in its concentration which is regulated by the carbon cycle as a result of these two variables a radiocarbon age is not equivalent to a calendar age four decades of joint research by the dendrochronology and radiocarbon communities have produced a radiocarbon calibration data set of remarkable precision and accuracy extending from the present to approximately 12 000 calendar years before present this paper presents high precision paired 230 th 234 u 238 u and 14 c age determinations on pristine coral samples that enable us to extend the radiocarbon calibration curve from 12 000 to 50 000 years before present we developed a statistical model to properly estimate sample age conversion from radiocarbon years to calendar years taking full account of combined errors in input ages and calibration uncertainties our radiocarbon calibration program is publicly accessible at http www radiocarbon ldeo columbia edu along with full documentation of the samples data and our statistical calibration model

aminostratigraphy of pliocene pleistocene high sea level deposits nome coastal plain and adjacent nearshore area alaska amino acid epimerization ratios aile ile measured in 295 fossil molluscan shells of 3 genera provide a basis to evaluate the number and relative timing of high sea level events represented by deposits blanketing the nome coastal plain and adjacent nearshore area northwestern alaska frequency distribution analysis along with a new approach that relies on the ranked data distribution was used to identify clusters aminozones in the aile ile data each of which presumably represents a discrete period of marine inundation of the study area six periods of high relative sea level were distinguished some are recognized only by redeposited shells rather than in situ bio or lithostratigraphic units the oldest period is represented by shells recovered from the deepest sections of two offshore boreholes aile ile ratios in these shells 1 0 are much higher than in any found onshore and probably date to the late miocene early pliocene the oldest aminozone lies below nonfossiliferous sediments which in turn are overlain by glacigenic and marine deposits containing largely fragmented shells with aile ile ratios ranging from 0 35 to 0 65 this range coincides with aile ile ratios from various onshore deposits previously ascribed to the middle pliocene 3 m y beringian transgression ratios in this range can be subdivided into three evenly spaced aminozones each of which may represent multiple short duration 10 4 yr high sea stands separated by a longer period 10 5 yr sea level oscillation on the basis of a new empirical model of parabolic epimerization kinetics and an assumed age of 3 2 m y for the oldest beringian aminozone the approximate age of the initial submergence of bering strait the estimated length of time represented by the three beringian aminozones is between 0 5 and 1 7 m y the youngest beringian highstand was followed in the late pliocene or early pleistocene by a lengthy period of nonmarine deposition during which local valley glaciers advanced onto the coastal plain at least once relative sea level apparently did not again surpass that of today until the middle pleistocene anvilian transgression the oldest higher than present stand of the pleistocene yet considerably younger than previously thought glaciers overran the nome coastal plain at least once following the anvilian transgression incorporating abundant shells into their drift the drift is notched by a shoreline formed during the pelukian transgression of the last interglaciation although well represented onshore no pelukian deposits have been found offshore

the role of grain dissolution and diagenetic mineral precipitation in the cycling of metals and phosphorus a study of a contaminated urban freshwater sediment this paper describes the detrital mineralogy early diagenetic reactions and authigenic mineral precipitates for freshwater contaminated sediments deposited in an urban water body the salford quays of the manchester ship canal greater manchester uk these sediments contain a mix of natural and anthropogenic detrital grains detrital grains are dominated by quartz and clay grains whilst anthropogenic grains are dominated by metal rich glass grains concentrated at a depth of 12 17 cm in the sediment as a result of historical inputs sediment porewaters contain significant concentrations of fe mn zn and phosphate bacterial fe iii and mn iv reduction are hypothesised to supply fe2 and mn2 to porewaters with phosphate released from fe oxide reduction or organic matter oxidation petrographic observations indicate that the metal rich glass grains are undergoing chemical dissolution during early diagenesis supplying fe and zn to porewaters the most abundant authigenic mineral in the sediments is vivianite fe3 po4 2 8h2o containing a significant level of redlingite with minor framboidal pyrite fes2 electron microprobe analysis shows the vivianite to contain zn cu and pb suggesting that vivianite acts as a long term sink for these metals in this sediment this implies that authigenic vivianite in freshwater sediments may act as a long term sink for metals in a similar manner to sulphides in marine sediments this study highlights that the nature of detrital and diagenetic mineralogy in addition to porewater and sediment chemistry needs to be considered in assessing contaminated sediments

roxana silt of the upper mississippi valley lithology source and paleoenvironment significant lithological differences exist between the middle wisconsinan roxana silt loess of the upper mississippi valley the valley north of 41 5 and that of the type area near st louis missouri primary differences are that the upper mississippi valley roxana silt is much thinner finer textured and more weathered than that of the type area extrapolation of radiocarbon dates brackets sedimentation of upper mississippi valley roxana silt between 55 and 27 ka which is in close agreement with dates from the type area radiocarbon dates and paleobotanical data indicate that the upper mississippi valley roxana silt accumulated at a maximum long term average sedimentation rate of about 7 cm 1 000 yr within a boreal forest environment whereas the type area roxana silt accumulated at a maximum long term average sedimentation rate of about 60 cm 1 000 yr within a prairie like environment multiple regression analysis shows that more than 75 of the variance in thickness and texture between the upper mississippi valley roxana silt and that of the type area is explained by parameters of source valley width source valley azimuth and distance of the depositional site from the source valley this indicates that although the lithologic characteristics and sedimentation rates between the two regions are quite different they are consistent with a unified loess sedimentation sys tem linked to the ancient mississippi river valley a proglacial source for the roxana silt and a middle wisconsinan advance of the lauren tide ice sheet is a topic of scientific debate because recent findings show a lack of roxana correlative till deposits in the midwest alternative hypotheses include a glaciolacustrine source a regional slope erosion source and a cold climate desert dust source tests of these hypotheses support a proglacial origin for the roxana silt multiple regression analysis of loess thickness and texture along with paleobotanical evidence indicates that the roxana silt was blown from the ancient mississippi valley rather than from a cold climate desert source or from flood plains linked to a glaciolacustrine source geochemical and mineralogical composition of the upper mississippi valley roxana silt compared to out wash derived peoria loess indicates that detritus from regional hillslope erosion is not a unique component of the roxana silt combined data indicate that the midcontinental roxana silt was derived as loess blown from flood plains of middle wisconsinan proglacial rivers between 55 and 27 ka

isotopic composition of sulfate as a tracer of natural and anthropogenic influences on groundwater geochemistry in an urban sandstone aquifer birmingham uk abstract development and management of urban groundwater resources is limited in practice by a lack of knowledge of the nature distribution and sources of groundwater contamination in an urban aquifer that may have had complex land use and abstraction history sulfate is associated with many of the solute sources to urban groundwater and in this study the use of dual isotope 18o and 34s fingerprinting of so 4 2 in groundwater to assess the contribution of different sources to urban groundwater is investigated groundwater 70 locations and surface water samples from the city of birmingham on the triassic sherwood sandstone aquifer have been analyzed for inorganic chemical and so 4 2 isotopic composition isotopic compositions of so 4 2 associated with various solute sources have also been determined sulfate derived from pyrite oxidation during recharge through quaternary drift deposits is characteristically depleted in 18o and 34s compared to other sources and is ubiquitous in unconfined zone groundwater though the contribution from this source has increased markedly following draw down induced by abstraction from the aquifer in unpolluted groundwaters other so 4 2 sources are dissolution of evaporite minerals confined zone and rainfall unconfined zone unfortunately so 4 2 isotopic composition cannot distinguish between made ground i e artificial man made ground usually demolition waste and sewage sources of so 4 2 which constitute the major contributions to so 4 2 in polluted urban groundwater at most sites contributions of so 4 2 from spilt industrial acids do have a distinctive isotopic composition seen at many metal working and former metal working sites estimates of solute contributions derived from these sources derived in this way provide a useful check on the calibration of aquifer and pollutant flux recharge models for urban groundwater

paleopedology plus tl 10be and 14c dating as tools in stratigraphic and paleoclimatic investigations mississippi river valley u s a thick 35 m loess deposits are present on ridges and high bluffs in the northern half of the lower mississippi valley lmv u s a detailed descriptions of the loess sections and pedologic physiochemical and mineralogic analyses and tl 14c and 10be age determinations allow preliminary paleoclimatic reconstructions for the late quaternary of central north america no age data are available for the oldest fifth loess 10be and tl age data suggest a 250 200 ka age for the fourth or crowleys ridge loess and indicate that the loveland or third loess is time equivalent to oxygen isotope stage 6 190 120 ka a weakly developed paleosol is present in the basal half of the loveland the sangamon geosol is present in the upper 5 m and represents all of oxygen isotope stage 5 130 60 ka it formed in a climate as warm as but drier and or with greater variation in precipitation than the present the roxana silt second loess was deposited during oxygen isotope stages 4 and 3 65 26 ka the early wisconsinan interglacial glacial transition represented by the sangamon geosol and the unnamed paleosol in the basal roxana silt was slow the paleoclimate during the 35 k yr of roxana deposition was cool to cold and wet age and pedologic data indicate that deposition of the peoria loess the youngest began around 25 ka when the area s climate changed abruptly from cool or cold and wet to cold and dry with periods of sustained high winds