peat accumulation in northern wetlands abstract mean long term rates of peat accumulation are higher in boreal and temperate peat deposits than in subarctic regions of canada although peatlands are extensive in the subarctic climatic change probably accounts for the development of southern peatlands during the middle to late holocene and for the late holocene decline in growth of many subarctic peat deposits in northwestern peat deposits peat of wet sphagnum lawns and treed wetlands tended to accumulate more rapidly than peat of sphagnum hummocks and sedge fens long term net rates of carbon accumulation in canadian peatlands typically range from 10 to 35 g c m2 yr

charcoal analysis for paleoenvironmental interpretation a chemical assay a nitric acid digestion and ignition technique developed to measure relative frequencies of charcoal in lake and bog sediments measures the weight of charcoal relative to the dry weight of the sample percentage charcoal and gives results comparable to counting of microscopic charcoal differences in the two techniques caused by changes in sediment type were found especially in postsettlement and late glacial parts of cores charcoal values from sediments less than 100 yr old cannot be compared to older charcoal values unless wood charcoal and charcoal from fossil fuel burning are separated microscopically tests of this chemical assay on mixtures of known weights of charcoal leaves and sand give correlations between observed and expected values of 0 99 to 1 00

discussion on large sea small tides the late carboniferous seaway of nw europe roger higgs writes wells et al 2005 a b produced an innovative and thought provoking numerical model of tides in the late carboniferous seaway of nw europe predicting very low tidal ranges 1 m consistent with the scarcity of sedimentary evidence for weak tides reported in the corresponding rocks based on the model wells et al 2005 a argued intuitively that tidal range was minimum during glacioeustatic highstands and maximum during lowstands and transgressions i would argue the converse during highstands not only was the water volume mass greater leading potentially to larger tides but also any tide in the adjacent ocean would necessarily be passed into the seaway adding to the locally generated tide this is a weakness of the model the oceanic tidal influence was not incorporated for simplicity wells et al 2005 a p 418 in contrast during lowstands the seaway became a freshwater lake or chain of lakes perched at the level of the outflow sill and bordered by incised highstand prograded deltas and alluvial plains lake bude of higgs 1991 2004 disconnected from the global ocean the lake would have had an extremely low tidal range 5 cm as in all lakes because of the relatively small water volume talbot allen 1996 indeed no evidence for tides has been reported in lake bude deposits ross crackington and bude formations of ireland and england higgs 1991 2004 and references therein however given the scarce evidence reported elsewhere in the seaway sedimentary structures indicative of weak tidal currents e g ripples with foreset slack water mud drapes rhythmic lamination opposed ripples may eventually be discovered in the lake bude formations probably associated with the volumetrically minor shale bands with brackish and marine fossils higgs 1991 2004 representing transgressions and highstands when

a late pleistocene mid holocene noble gas and stable isotope climate and subglacial record in southern michigan 1 stable isotopes d 18o and 14c derived ages in the saginaw aquifer in southern michigan suggest subglacial meltwater contributions from the laurentide ice sheet of up to 36 in the late pleistocene following the last glacial maximum contributions of up to 74 from previous glaciation periods are observed together with the marshall record ma et al 2004 noble gas temperatures ngts and excess air ea from the saginaw aquifer capture for the first time the onset of the younger dryas 12 9 kyr bp with a 3 3 c cooling accompanied by drier conditions mid holocene mh climatic shifts are also identified with warming 2 9 c increased aridity starting at 5 4 kyr bp followed by reversal to cooler humid conditions at 4 1 kyr bp except for the last mh reversal the stable isotope record mimics the ngt and ea records contrasting trends displayed by 18o and deuterium excess in the last mh reversal suggests enhanced vapor transport from the gulf of mexico

numerical modeling of rising head permeability tests in monitoring wells after lowering the water level down to the screen to begin a rising head permeability test in a monitoring well mw the water level is lowered in the pipe if it is lowered down to the screen the recovery graph may differ from the theoretical straight line making it difficult to assess the mean field hydraulic conductivity a numerical analysis finite element method of this type of test considering the complete equations for saturated and unsaturated flow is presented the numerically obtained graphs are similar to those of real field tests in an aquitard when the filter pack is made of fine sand which retains water by capillarity the screen dewatering influence is hardly visible in the velocity graph and is undetected in the usual semilog graph in an aquitard when the filter pack cannot retain water by capillarity during dewatering the semilog graph presents two straight line portions the velocity graph a representation of the conservation equation helps to distinguish the early time interval when the groundwater fills the screen and

macrofossil and tree ring evidence for a long term forest succession and mid holocene hemlock decline abstract paludified dune fields in southern quebec provided a unique opportunity to analyze a mid holocene forest succession ranging from xero mesophilous forests to treed peatlands which registered the hemlock decline a major biostratigraphic event in eastern north america our fossil tree chronology established from 66 radiocarbon dates of tree stems indicates that white pine and hemlock were present at the study site about 6000 5700 yr b p hemlock reached a maximum 4900 4800 yr b p and then declined between 4600 and 3800 yr b p the species recovered around 3700 yr b p and then decreased when white pine and eastern latch dominated the site after 3000 yr b p and between 2600 and 2200 yr b p respectively tree ring signatures of fossil hemlocks suggest the continuous influence of biotic factors possibly insect defoliators throughout the record as shown by recurrent suppressed growth pattern microscopic examination of the hemlock fossil stems disclosed no evidence of fungal disease the hemlock decline was probably caused by regional posthypsithermal climatic changes toward moister conditions

from sink to volcanic source unravelling missing terrestrial eruption records by characterization and high resolution chronology of lacustrine volcanic density flow deposits lake inawashiro ko fukushima japan

the variability of holocene climate change evidence from varved lake sediments varved sediments from a lake near the present forest prairie border in northwestern minnesota provide an annual record of climate change for the last 10 400 years climate sensitive mineral chemical and biological components show that the mid holocene dry interval between 8500 and 4000 years ago is asymmetrical and actually consists of two distinct drier pulses separated by a moister interval that lasted about 600 years cyclic fluctuations with periods of several hundred years were abrupt and persistent throughout the holocene and are most clearly recorded within the two drier pulses

effects of installation of piezometers and wells on groundwater characteristics and measurements the results of a variable head permeability test can be used to check whether a piezometer or sampling well has been successfully sealed in the soil and to detect hydraulic short circuits and possible cross contamination between aquifers an improper seal is a well known cause of hydraulic short circuit in some instances also although the tubing has been sealed over its full length the water level in the pipe is not representative of the actual piezometric head an example shows that the values of hydraulic conductivity determined using several test methods varied in a 1 6 ratio before detection of a piezometric error the resulting correction reduced the variation in k to 12 the causes of hydraulic short circuits have been investigated using computer simulations it has been concluded that large errors recorded in the field are due to internal erosion of natural soils around the casing during drilling operations or development the hydraulic damage to soils is documented an analytical solution h

buried soils in a perched dunefield as indicators of late holocene lake level change in the lake superior basin abstract a stratigraphic analysis of buried soils within the grand sable dunes a dune field perched 90 m above the southern shore of lake superior reveals a history of eolian activity apparently linked with lake level fluctuations over the last 5500 yr a relative rise in the water plane of the nipissing great lakes initially destabilized the lakeward bluff face of the grand sable plateau between 5400 and 4600 14 c yr b p this led to the burial of the sable creek soil by eolian sediments derived from the bluff face subsequent episodes of eolian activity appear to be tied to similar destabilizing events high lake levels may have initiated at least four and perhaps eleven episodes of dune building as expressed by soil burials within the dunes intervening low lake levels probably correlate with soil profile development which varies from the well developed sable creek spodosol catena to thin organic layers containing in place stumps and tree trunks paleoecological reconstructions available for the area do not imply enough climatic change to account for the episodic dune activity burial of soils by fine fraction sediments links dune building episodes with destabilization of the lower lake facing bluff which is rich in fines

middle holocene dry period in the northern midwestern united states lake levels and pollen stratigraphy abstract four cores from lake mendota in the yahara river valley of south central wisconsin provide pollen charcoal and sediment stratigraphic evidence of a middle holocene dry period in the northern midwest the lake level was lower between about 6500 and 3500 yr b p indicating that runoff from the upper yahara river basin may have ceased during the drier seasons of the year derived estimates of precipitation between 6500 and 3500 yr b p indicate a decrease of about 10 down to about 700 mm from the present precipitation value of 800 mm a warming between 6500 and 3500 yr b p is also interpreted based on a change of vegetation from rich mesophytic forest before 6500 yr b p to quercus savanna with increased charcoal abundances after that time after 3500 yr b p a closed quercus forest and decreased charcoal suggest a cooler and wetter climate the qualitative paleoecological interpretations quantitative precipitation reconstructions based on pollen from the region including the lake mendota data and estimates of hydrologic budget based on lake level changes all show indications of a dry and warm middle holocene evidence from a large regional array of sites also supports these interpretations

holocene climatic change in the northern midwest pollen derived estimates mapping of holocene pollen data in the midwestern united states has revealed several broadscale vegetational changes that can be interpreted in climatic terms these changes include 1 the early holocene northward movement of the spruce dominated forest and its later southward movement after 3000 yr b p and 2 the eastward movement of the prairie forest border into southwestern wisconsin by 8000 yr b p and its subsequent westward retreat after 6000 yr b p when certain basic assumptions are met multiple regression models can be derived from modern pollen and climate data and used to transform the pollen record of these vegetational changes into quantitative estimates of temperature or precipitation to maximize the reliability of the regression equations we followed a sequence of procedures that minimize violations of the assumptions that underlie regression analysis reconstructions of precipitation during the holocene indicated that from 9000 to 6000 yr b p precipitation decreased by 10 to 25 over much of the midwest while mean july temperature increased by 0 5 to 2 0 c at 6000 yr b p precipitation was less than 80 of its modern values over parts of wisconsin and minnesota after 6000 yr b p precipitation generally increased while mean july temperature decreased in the north and increased in the south the time of the maximum temperature varies within the midwest and is earlier in the north and later in the south

pattern of southern laurentide ice sheet margin position changes during heinrich stadials 2 and 1 abstract with concerns over rising global temperatures ice sheet stability and implications for sea level rise the responses of former ice sheets to past climate change provide useful insights into linkages between the atmosphere cryosphere and oceans one example is the behavior of the laurentide ice sheet lis during heinrich stadials times of cooler sea surface temperature sst in the north atlantic using existing cosmogenic surface exposure ages varve chronologies radiocarbon ages and optically stimulated luminescence ages from the southern lis margin this report tests the hypothesis that the southern side of the lis advanced during times of surface cooling of the north atlantic this test reconstructs the timing of local glacial maxima and the times immediately pro and preceding them from multiple areas and compares them to the timing of heinrich stadial 2 hs2 26 6 23 6 ka and to the timing of heinrich stadial 1 hs1 19 3 15 3 ka during hs2 southern sector lobes new england region huron erie lobe lake michigan lobe green bay lobe and the chippewa lobe advanced towards their maximum position except for the des moines lobe for which there is no applicable data during hs1 these same lobes experienced substantial retreat but the des moines lobe advanced thus the southern laurentide margin behaved differently during the two heinrich stadials this pattern may be attributed to differing east west temperature gradients across north america and associated changes in atmospheric circulation

responses of floods to holocene climatic change in the upper mississippi valley abstract dimensions of holocene relict channels and sedimentological characteristics of point bars associated with these relict channels were used to reconstruct a holocene history of long term changes in magnitudes of 1 58 yr floods in upper mississippi valley watersheds of southwestern wisconsin the reconstructed record of floods shows relatively large and persistent nonrandom departures from contemporary long term average flood magnitudes the flood history indicates climatic changes that are broadly similar to climatic changes indicated from fossil pollen in the same region the holocene floods ranged from about 10 15 larger to 20 30 smaller than contemporary floods of the same recurrence frequency large floods were characteristic between about 6000 4500 and 3000 2000 yr b p and during a brief interval after 1200 yr b p small floods were common between about 8000 6500 4500 3000 and 2000 1200 yr b p these fluvial responses were found to be closely associated with a long term episodic mobility and storage of sediments in the wisconsin watersheds during periods of relatively large floods relatively rapid lateral channel migration either reworked or removed extensive tracts of valley bottom alluvium in contrast during periods of relatively small floods relatively slow lateral channel migration is apparent and the channel and floodplain system appear to have been relatively stable

sand bentonite liners predicting permeability from laboratory tests soil bentonite mixes are frequently used as impervious blankets in waste disposal projects numerous results of laboratory permeability tests are presented for sands containing up to 33 bentonite these results seem difficult to analyze because different testing methods have been used in which it is not easy to control certain parameters such as hydration period degree of saturation and swelling under low confining pressure hydraulic conductivity however can be obtained by using empirical equations that take into account the bentonite content porosity and degree of saturation of the sand alone when tested at its optimum modified proctor value in a permeameter this preliminary evaluation helps to select the soil to be tested then the laboratory test results can be used to predict the in situ hydraulic performance after due consideration of the variabilities in natural sand and bentonite content key words liner soil bentonite permeability laboratory field

holocene climatic change in morocco a quantitative reconstruction from pollen data annual precipitation july and january temperatures were reconstructed from a continuous holocene pollen sequence from the middle atlas morocco using the best modern analogues method the reconstructions show a clear difference between the early and late holocene from 10 ka to 6 5 ka the climate was drier and warmer than during the period since 6 5 ka the average value of annual precipitation was 870 mm until 6 5 ka then rose to 940 mm between 10 ka and 6 5 ka january and july temperatures were about 4 c higher than the present both temperatures show a marked decrease between 7 ka and 6 ka after 6 5 ka july and january temperatures fluctuated between 21 and 23 c and 2 5 and 5 c respectively january temperatures show a period of intermediate values 3 5 c between 4 ka and 5 5 ka the reconstructed climate values generally match palaeolimnological data from the same core which show five intervals of low lake level during the holocene they are also consistent with regional scale cohmap simulated palaeoclimate that shows contrasting patterns of rainfall variation between the northwesternmost part of africa and the intertropical band

paleohydrological implications of holocene peatland development in northern michigan daphne sphagnum peatlands provide data about local hydrologic changes in northern michigan during the holocene gleason bog started about 8000 yr b p as a shallow pond that supported rich fen vegetation after it was partly filled with peat and sand about 4000 yr b p the vegetation changed to oligotrophic bog at gates bog paludification starting about 3800 yr b p caused peat accumulation over sand without an initial pond phase the onset of peat accumulation at both sites is attributed to a rise in the water table resulting from the onset of cool and moist late holocene climates the water table of gleason bog is linked to the water level of adjacent douglas lake which may have undergone a simultaneous rise the results emphasize the individuality of hydrological conditions and hydroseral development in northern michigan peatlands q

14 000 years of sediment vegetation and water level changes at the makepeace cedar swamp southeastern massachusetts abstract data from a transect of four cores collected in the makepeace cedar swamp near carver massachusetts record past changes in deposition vegetation and water level time series of palynological data provide a 14 000 yr record of regional and local vegetation development a means for biostratigraphic correlation and dating and information about changes in water level differences in records among cores in the basin show that water level decreased at least 1 5 m between 10 800 and 9700 cal yr b p after which sediment accumulation was slow and intermittent across the basin for about 1700 yr between 8000 and 5600 cal yr b p water level rose 2 0 m after which slow peat accumulation indicates a low stand about the time of the hemlock decline at 5300 200 cal yr b p dry conditions may have continued after this time but by 3200 cal yr b p the onset of peat accumulation in shallow cores indicates that water level had risen to close to its highest postglacial level where it is today peat has accumulated across the whole basin since 3200 cal yr b p data from makepeace and the pequot cedar swamp near ledyard connecticut indicate an early holocene dry interval in southern new england that began 11 500 yr ago near the end of the younger dryas interval the dry conditions prevailed between 10 800 and 8000 cal yr b p and coincide with the arrival and later rise to dominance of white pine trees pinus strobus both regionally and near the basins our results indicate a climatic cause for the pine period in new england

palaeohydrological characteristics and palaeogeographic reconstructions of incised valley fill systems insights from the namurian successions of the united kingdom and ireland namurian carboniferous eustatic fluctuations drove the incision and backfill of shelf crossing valley systems located in humid subequatorial regions which are now preserved in successions of the united kingdom and ireland the infills of these valleys archive the record of palaeoriver systems whose environmental hydrological and palaeogeographic characteristics remain unclear a synthesis of sedimentological data from fluvial strata of 18 namurian incised valley fills in the united kingdom and ireland is undertaken to elucidate the nature of their formative river systems and to refine regional palaeogeographic reconstructions quantitative analyses are performed of facies proportions of geometries of incised valley fills and related architectural elements and of the thickness of dune scale sets of cross strata reconstruction of the size of the drainage areas that fed these valleys is attempted based on two integrative approaches flow depth estimations from dune scale cross set thickness statistics and scaling relationships of incised valley fill dimensions derived from late quaternary examples the facies organization of these incised valley fills suggests that their formative palaeorivers were perennial and experienced generally low discharge variability consistent with their climatic context however observations of characteristically low variability in cross set thickness might reflect rapid flood recession perhaps in relation to sub catchments experiencing seasonal rainfall variations in facies characteristics including inferences of flow regime and cross set thickness distributions might reflect the control of catchment size on river hydrology the degree to which is considered in light of data from modern rivers palaeohydrological reconstructions indicate that depth estimations from cross set thickness contrast with observations of barform and channel fill thickness and projected thalweg depths exceed the depth of some valley fills limitations in data and interpretations and high bedform preservation are recognized as possible causes with consideration of uncertainties in the inference of catchment size the palaeogeography of the valley systems has been tentatively reconstructed by integrating existing provenance and sedimentological data the approaches illustrated in this work can be replicated to the study of palaeohydrological characteristics and palaeogeographic reconstructions of incised valley fills globally and through geological time

late yeadonian upper sandstone group incised valley supply and depositional systems in the south wales peripheral foreland basin implications for the evolution of the culm basin and for the silesian hydrocarbon plays of onshore and offshore uk abstract the upper sandstone group of south wales has previously been interpreted as a simple nnw sse trending incised valley that was filled during the late yeadonian namurian g1b data presented in this study indicate a far more complex scenario the group is well developed in the pembrokeshire sub basin but it is absent from the main part of the south wales basin located to the east of the penlan axis the principal source area for sediment flux was the forebulge of the basin located to the north in lower palaeozoic foreland strata variscan flexural uplift of this source area and an accompanying rapid high magnitude fall in sea level produced a very high sediment budget thus during the late yeadonian lowstand of sea level massive amounts of sediment were being generated and transported via an incised valley system across the western part of the south wales peripheral foreland basin the location and orientation of the incised supply system and its related interfluves were controlled by intrabasinal synsedimentary variscan structures many of which were reactivated caledonian extensional faults during the succeeding sea level rise the incised valley was filled initially by fluvio deltaic sands and later by estuarine argillaceous sediments the implications of this combined tectonic sedimentological high resolution sequence stratigraphic model for the evolution of the late namurian crackington formation turbidites of the culm basin are discussed examples of silesian incised valley fill sandstone reservoirs developed in the east midlands oilfield and the southern gas basin are briefly summarised and their spatial and temporal distributions are appraised data generated from these case studies are assessed in terms of their use for the modelling of incised valley fill sequences in foreland basins and other tectonic settings

environmental change and its impacts on human settlement in the yangtze delta p r china abstract archaeological excavations and environment archaeology studies over many years in the yangtze delta region have provided exceptional information about climatic variations growth and demise of human civilization and human environment interactions the archaeological excavations show that the cultural layers of the neolithic sites are interrupted by barren layers without any cultural relics so called cultural interruptions which may be the result of harsh environmental conditions arid flooding extreme cold or warmth temporal and spatial analyses of 14c dates for buried trees peat shell ridges and neolithic sites show that environmental changes are responsible for the rise and fall of human civilization the progress of human civilization was interrupted at least 5 times in the yangtze delta matching 5 periods of high sea level peat accumulation and burial of trees the collapse of the liangzhu culture about 4000 bp was followed by the less developed maqiao culture and resulted from extreme environmental and hydrological conditions such as floods

return of the fan that never was westphalian turbidite systems in the variscan culm basin bude formation south west england thirty ve years ago harold reading stated 1963 p 69 the precise depositional environment of the bude sandstones is not easy to establish appropriately two of his former students are still arguing whether the environment was a storm affected shelf higgs 1986a 1987 1991 or a deep water fan burne 1969 1995 the paper by burne 1995 questions my shelf interpretation prompting this discussion burne and i agree that deposition took place offshore in a large westphalian lake with occasional marine connections based on faunal aspects and on the lack of evidence for emergence goldring seilacher 1971 lake bude of higgs 1986b 1994 we also agree that the majority of the sandstone beds are turbidites but whereas i argued for river fed turbidites on a shelf with storms accounting for both catastrophic rainfall hence sandy under ows and accompanying waves burne 1995 invokes slump generated turbidites on a deep water fan below storm wavebase the tectonic setting was the northern passive margin of a foreland basin higgs 1991 burne 1995 burne 1995 argues that all of the sedimentary structures interpreted by higgs 1991 as indicating shallow water deposition above storm wavebase can also occur in deep water turbidite settings these structures are quasi symmetrical ripples irregular cross lamination hummocky cross strati cation multidirectional tool marks and mud draped scours rare symmetrical wave ripples occur in the bude formation although burne 1995 p 130 points out that no convincing illustration of them has been published to date his italics in the following discussion i shall sequentially address these and other contentious issues raised by burne 1995 my intentions are threefold 1 to question the basis of burne s fan model 2 to reiterate evidence for my lake shelf model and 3 to explain that the shelf origin has been masked for decades by certain unusual facies characteristics including slurried and slumped beds formed in situ as seismites but widely misinterpreted as debris ows and slumps the shelf vs fan debate is not only interesting academically but also important economically because the easily accessible cliffs of bude are a magni cent natural laboratory in which to gather data for petroleum reservoir models

hydrologic changes in colorado during the mid holocene and younger dryas abstract the stratigraphy of upper big creek lake ubc an overflowing lake in northern colorado indicates that the lake responded to a series of hydroclimatic changes over the past 13 000 years modern sediments in eight comparator lakes from across wyoming and colorado facilitate the stratigraphic interpretation by showing that littoral sediments have exponentially higher sand content lower loss on ignition loi and lower net accumulation rates than off shore sediments sand layers in two near shore cores from ubc share the characteristics of the modern littoral sediments 80 sand 1 9 m below its outlet from 12 500 to 11 300 and from 7500 to 2100 cal yr bp ground penetrating radar gpr profiles consistent with the low water episodes show correlative sand layers and submerged wave cut scarps around the lake margin the stratigraphic features correlate with those formed in the comparator lakes during extensive droughts at 11 300 6900 6000 and 4800 3400 cal yr bp as well as a series of north south anti phased droughts between 5800 and 1200 cal yr bp lake closure at ubc amplified the local changes and demonstrates that climate changes can increase the extent of intermittent streamflow in the rocky mountains relative to today

comments on hybrid sediment gravity flows classification origin and significance from haughton davis mccaffrey and barker marine and petroleum geology 2009 26 1900 1918

paleoecology of a northern michigan lake and the relationship among climate vegetation and great lakes water levels abstract we reconstructed holocene water level and vegetation dynamics based on pollen and plant macrofossils from a coastal lake in upper michigan our primary objective was to test the hypothesis that major fluctuations in great lakes water levels resulted in part from climatic changes we also used our data to provide temporal constraints to the mid holocene dry period in upper michigan from 9600 to 8600 cal yr b p a shallow lacustrine environment characterized the mud lake basin a sphagnum dominated wetland occupied the basin during the mid holocene dry period 8600 to 6600 cal yr b p the basin flooded at 6600 cal yr b p as a result of rising water levels associated with the onset of the nipissing i phase of ancestral lake superior this flooding event occurred contemporaneously with a well documented regional expansion of tsuga betula pollen increased during the nipissing ii phase 4500 cal yr b p macrofossil evidence from mud lake suggests that betula alleghaniensis expansion was primarily responsible for the rising betula pollen percentages major regional and local vegetational changes were associated with all the major holocene highstands of the western great lakes nipissing i nipissing ii and algoma traditional interpretations of great lakes water level history should be revised to include a major role of climate

the 2000 r m hardy lecture full scale hydraulic performance of soilbentonite and compacted clay liners the results of laboratory and in situ permeability tests can be used to predict the total leakage rate of a soil bentonite or clay liner this prediction however ignores the large influence that minor defects may have on the total leakage in quebec hundreds of municipal wastewater ponds have been filled with water to measure their total leakage rate before approval the design criteria and the equations to be used for the full scale performance test are briefly reviewed with their capacities to detect hydraulic deficiencies several case histories are presented to illustrate various problems excessive leakage of a stable soil bentonite mix washing of bentonite in a soil bentonite mix internal erosion of a natural clay liner through an inadequate sand filter and effects of freezing on the total leakage of a clay liner key words liner clay bentonite permeability performance full scale test

quantitative estimates of temperature changes over the last 2700 years in michigan based on pollen data temperatures for the past 2700 yr are estimated using well dated pollen data from northwestern lower michigan the pollen data were sampled from sediment cores of four lakes along a 75 km transect with fine grained morainic soils around the two western lakes and sandy outwash soils around the lakes to the east climatic reconstructions based on the pollen data from the sandy sites show less temperature change than the reconstructions from the other sites because variations in the composition of the vegetation at the sandy sites are edaphically restricted one of the cores studied was dated by counting visible annual laminations varves the cores from the other lakes were dated based on three radiocarbon dates per core as well as the historically determined age of the settlement horizons all the time scales were cross checked using pollen stratigraphic correlation between the four sites a calibration function was developed using a network of modern pollen and climate data covering all of lower michigan based on this calibration function the 2700 yr reconstruction for marion lake indicates an estimated growing season temperature range of 1 3 c between extreme 30 yr means mild conditions persisted prior to ca a d 400 but a cold interval occurred between ca a d 500 and 800 the well marked warm period evident from ca a d 1000 to 1200 was the last time when temperatures were about equal to the 1931 1960 mean a prolonged longed cooling occurred after a d 1200 and reached 1 c below the 1931 1960 mean by the 1700s a warming of 0 5 c is indicated from ca a d 1750 to 1850 the estimated temperatures for the 1830s at marion lake agree with the instrumental data for that period and this provides some validation of the calibration function results

reconstruction of past lake levels and their relation to groundwater hydrology in the parkers prairie sandplain west central minnesota abstract the parkers prairie sandplain lies along the prairie forest border in west central minnesota an area with ample palynological evidence of significant environmental change during the late pleistocene and holocene past lake levels provide independent evidence of environmental change over the same temporal and spatial scales as pollen analysis we used the method established by digerfeldt 1986 1988 to determine the lowest past levels of three closed basin lakes in the sandplain the method uses a combination of evidence from macrofossils coarse minerogenic matter and organic matter from a transect of cores taken in the near shore region to reconstruct past lake levels lower than present carbonate content magnetic susceptibility and pollen content in the cores provided supplementary evidence and aided cross correlation among the cores each of the three lakes had its lowest level between about 7200 and 6700 yr b p lake levels ranged from 2 8 m to 6 2 m lower than modern levels the greatest lake level lowering occurred for the lake farthest from the river that drains the sandplain the least lake level lowering occurred for the lakes close to the river this spatial pattern of lake level lowering implies that a lowering of the regional water table caused by a reduction in groundwater recharge was the ultimate cause of the lower lake levels the results demonstrate that surface water hydrology is not the sole determinant of lake level and that there are possible dangers in paleoclimatic interpretations of past lake levels based on the assumption of hydrologic isolation of basins

the timing of regional lateglacial events and post glacial sedimentation rates from lake superior abstract we analyze both new and previously published paleomagnetic records of secular variation psv from lake superior sediment cores and compare these records to correlated rhythmite varve thickness records to determine post glacial sedimentation rates and to reassess the termination of glaciolacustrine varves in the basin the results suggest that offshore sedimentation rates have exhibited considerable spatial variation over the past 8000 years particularly during the mid holocene we attribute offshore mid holocene sedimentation changes to alterations in whole basin circulation perhaps precipitated by a greater dominance of the gulf of mexico air mass during the summer season nearshore bays are characterized by high sedimentation rates for at least 1000 years after varve cessation and during a period between around 4500 and 2000 cal bp after 2000 cal bp sedimentation rates subsided to earlier rates the increases between 4500 and 2000 cal bp are probably due to lake level fall after the nipissing ii highstand the older glaciolacustrine varve thickness records suggest that the influx of glacially derived sediment ended abruptly everywhere in the lake except near the lake nipigon inlets multiple sediment cores reveal 36 anomalously thick varves previously ascribed to the formation of the nakina moraine which were deposited just prior to varve cessation in the open lake the psv records support the observation that the cessation of these thick varves is a temporally correlative event occurring at 9035 170 cal bp calibrated years before 1950 ca 7950 8250 14 c bp this date would correlate to the eastern diversion of lake agassiz and glacial meltwater into lake ojibway

mapped plant macrofossil and pollen records of late quaternary vegetation change in eastern north america abstract macrofossil presence absence maps and isopoll maps in 3000 year intervals show how ranges and abundance maxima for 12 eastern north american tree and shrub taxa picea p glauca p mariana larix laricina abies balsamea tsuga canadensis pinus strobus p resinosa p banksiana betula papyrifera b alleghaniensis b series humiles have changed from the last glacial maximum to the present the macrofossil maps corroborate patterns shown by the isopoll maps and provide spatial detail and taxonomic resolution the macrofossils confirm the inference from pollen data that unglaciated southeastern north america was cooler during the last glacial maximum 18 and 15 ka than simulated by the cohmap experiments with the ncar ccm0 general circulation model the geographic distribution of macrofossil occurrences during the late glacial 12 and 9 ka indicate that migration lag of boreal species did not occur at regional to subcontinental scales and that pollen assemblages lacking modern analogs resulted from climate gradients lacking modern analogs early holocene 9 and 6 ka macrofossil maps show rapid northward expansion of tree species ranges into deglaciated regions the data also show modest contractions of northern range limits of temperate species and expansions of southern range limits of boreal species in response to cooling trends during the late holocene 3 and 0 ka comparison of modern macrofossil maps of nine of these taxa with corresponding range maps confirm that the macrofossils record the geographic ranges accurately comparison of the modern macrofossil maps with maps of tree growing stock volume shows that for some taxa abies tsuga macrofossil occurrences were most frequent in regions of maximum tree abundance comparison of modern isopoll maps with the modern range and growing stock volume maps indicate that in contrast to the macrofossil data the pollen data provide poorer resolution of range limits for most taxa but better indications of abundance maxima and minima within the ranges

pollen response surface estimates of late quaternary changes in the moisture balance of the northeastern united states abstract quantitative estimates of late quaternary climate in the northeastern united states are reconstructed from fossil pollen data to evaluate changes in the regional moisture balance inferred from water level fluctuations we use environmental response surfaces to calibrate modern pollen data for 17 different taxa to an index of effective soil moisture and mean annual precipitation we apply these response surfaces to fossil pollen data from 60 sites in the region to reconstruct changes in soil moisture and mean annual precipitation at 3000 yr intervals from 12 000 yr b p to present the mapped reconstructions of soil moisture and mean annual precipitation illustrate how the regional moisture balance of the northeast may have changed over the last 12 000 yr in response to changing climate reconstructions of annual precipitation show a gradual increase from 30 below modern values at 12 000 yr b p to near modern values by 6000 yr b p and then remain relatively constant thereafter reconstructed changes in the index of effective soil moisture however show a pattern of near modern values at 12 000 6000 and 3000 yr b p with significantly lower values estimated for 9000 yr b p the time of maximum pine pollen abundances in the northeast this pattern of change is similar to the change in regional moisture balance inferred from stratigraphic records of water level fluctuations these results confirm previous interpretations based on records of water level fluctuations that conditions in the northeast were significantly drier during the early to middle holocene than at other times during the last 12 000 yr

paleoecology and high resolution paleohydrology of a kettle peatland in upper michigan we investigated the developmental and hydrological history of a sphagnum dominated kettle peatland in upper michigan using testate amoebae plant macrofossils and pollen our primary objective was to determine if the paleohydrological record of the peatland represents a record of past climate variability at subcentennial to millennial time scales to assess the role of millennial scale climate variability on peatland paleohydrology we compared the timing of peatland and upland vegetation changes to investigate the role of higher frequency climate variability on peatland paleohydrology we used testate amoebae to reconstruct a high resolution hydrologic history of the peatland for the past 5100 years and compared this record to other regional records of paleoclimate and vegetation comparisons revealed coherent patterns of hydrological vegetational and climatic changes suggesting that peatland paleohydrology responded to climate variability at millennial to sub centennial time scales although ombrotrophic peatlands have been the focus of most high resolution peatland paleoclimate research paleohydrological records from sphagnum dominated closed basin peatlands record high frequency and low magnitude climatic changes and thus represent a significant source of unexplored paleoclimate data

evidence of stream response to holocene climatic change in a small wisconsin watershed abstract during the holocene moderate climatic and vegetational changes triggered several episodes of adjustment in the brush creek fluvial system the alluvial chronology includes an episode of erosion at 7800 5700 yr b p corresponding to the mid holocene precipitation minimum and an episode of floodplain construction at 5700 5000 yr b p corresponding to a rapid increase in precipitation holocene climatic changes have influenced the sedimentology of the alluvial deposits and soil development on them fluvial adjustment is caused primarily by hydrologic and hydraulic changes related to climatic change but there is no simple model for fluvial response to climatic change the relationship between the direction of climatic change and the type of fluvial response is complex

polykinematic foreland basins initiated during orthogonal convergence and terminated by orogen oblique strike slip faulting an example from the northeastern variscan belt abstract an extensive early carboniferous foreland basin the moravosilesian culm basin mscb delineates the northeastern margin of the bohemian massif variscan orogenic belt the basin overlays a complex suture between the outer brunovistulia microplate forming a promontory previously accreted to laurussia and inner gondwana derived units that form the remainder of the bohemian massif our structural paleomagnetic and magnetic anisotropy data from the eastern portion of the mscb indicate that its depositional architecture internal fabric and deformation by folding and faulting record a major switch from orthogonal convergence to orogen oblique strike slip shearing first the brunovistulia microcontinent was subducted frontally towards w during 346 335 ma followed by a shift of the subduction vector towards ssw at around 335 330 ma from 330 ma onwards the underthrusting had ceased and the wnw ese dextral elbe shear zone related to the westward movement of gondwana with respect to laurussia controlled deformation of this region displacement of the northerly eastern sudetes block towards ese produced regional wnw ese pure shear shortening against the brunovistulia indentor and resulted in an overall doubly vergent structure of the mscb simultaneously the southerly moldanubian unit was translated towards wnw away from the brunovistulian microplate and likely contributed to an extensional regime related to orogenic collapse progressing outward from the internal domains of the bohemian massif on a larger scale we suggest that the mscb is an illustrative example of a polykinematic foreland basin where deposition syn to post sedimentary deformation and thus geodynamic processes changed significantly during basin evolution starting off with microplate impingement into a continental margin reentrant and terminated by strike slip shearing our data also do not support previous models for the tectonic development of the northeastern termination of the variscan belt which suggested either a large magnitude vertical axis oroclinal rotation of the foreland or its translation along an orogen perpendicular strike slip fault

holocene lake effect precipitation in northern michigan holocene sediments from nelson lake on michigan s eastern upper peninsula provide isotopic pollen and charcoal evidence for a two step sequence of changes in moisture source and increased lake effect precipitation during the late holocene between 8000 and 5300 cal yr b p a warm dry climate and zonal atmospheric circulation produced enriched stable oxygen and carbon isotopic values in combination with high percentages of pine pollen and sustained influx of charcoal particles after 5300 cal yr b p decreasing isotopic values in marl and increasing pollen percentages of mesic hardwoods and northern white cedar indicate increased meridional air flow and precipitation from cold winter storms generated in alberta canada after 3000 cal yr b p abrupt declines in values of 13c and 18o and increased pollen representation of hemlock american beech spruce and aquatic plants indicate paludification from increased lake effect snowfall the moisture was derived from the great lakes and transported by alberta cyclonic storms that were steered across lakes superior and michigan by a southward shift in the modal winter position of the polar jet stream

borehole variable head permeability tests in compacted clay liners and covers the performance of clayey liners and covers is assessed by several methods including borehole variable head permeability k tests different interpretations of the end of casing and lefranc tests

reconstruction of holocene lake level from diatoms chrysophytes and organic matter in a drainage lake from the experimental lakes area northwestern ontario canada abstract a paleolimnological study of lake level changes in lake 239 rawson lake a headwater lake in the experimental lakes area in northwestern ontario indicates large fluctuations have occurred over the holocene analyses are based on diatoms the proportion of chrysophyte scales to diatoms and organic matter content from near shore sediment cores quantitative estimates of lake level are based on a diatom inferred depth model that was developed from surficial sediments collected along several transects in lake 239 declines of 1 3 m occurred during the late holocene whereas declines of at least 8 m occurred during the more arid mid holocene these results provide the first substantive evidence of large declines in lake level in northwestern ontario during the mid holocene conditions during the mid holocene may provide a partial view of future conditions under increasing global temperatures

a groundwater model to explain past lake levels at parkers prairie minnesota usa the response of a lake level to a shift in climate depends on characteristics of surficial and groundwater hydrology that are unique to that lake determination of the past levels of several lakes rather than just one can help provide a more precise determination of past hydrology and climate for a given region the levels of several closed basin lakes in the parkers prairie sandplain in west central minnesota were lowest about 7 ka a steady state analytic element groundwater model was used to quantify the effect of changing regional groundwater recharge n on the altitude of the water table surrounding these lakes because overland flow on the sandplain is limited the surficial hydrology of the lakes can be simplified to the net quantity lake evaporation minus precipitation e p both n and e p were manipulated to force the model water table to coincide with the palaeolake levels model results indicate that lake levels at 7 ka can be explained primarily by reducing n to about 50 60 mm yr 1 40 5

holocene lake level rise in the upper peninsula of michigan usa as indicated by peatland growth we examined one sediment core from kerr lake and eight cores from the adjacent peatland in the sylvania wilderness area of the upper peninsula of michigan usa radiocarbon dating of the interface between peat and the underlying glacial till showed that the peatland grew by paludification of the surrounding uplands implying a rising water level in the lake pollen analysis of the cores showed that the peatland began expanding just before the arrival of tsuga in the surrounding forests the most rapid growth of the peatland occurred between 3900 and 3000 bp this is also the time when the forests were being transformed from dry pinus strobus dominated woodlands to moister tsuga and acer saccharum dominated northern hardwoods our results imply an increase in available moisture at the time of tsuga colonization

beds comprising debrite sandwiched within co genetic turbidite origin and widespread occurrence in distal depositional environments co genetic debrite turbidite beds occur in a variety of modern and ancient turbidite systems their basic character is distinctive an ungraded muddy sandstone interval is encased within mud poor graded sandstone siltstone and mudstone the muddy sandstone interval preserves evidence of en masse deposition and is thus termed a debrite the mud poor sandstone siltstone and mudstone show features indicating progressive layer by layer deposition and are thus called a turbidite palaeocurrent indicators ubiquitous stratigraphic association and the position of hemipelagic intervals demonstrate that debrite and enclosing turbidite originate in the same event detailed field observations are presented for co genetic debrite turbidite beds in three widespread sequences of variable age the miocene marnoso arenacea formation in the italian apennines the silurian aberystwyth grits in wales and quaternary deposits of the agadir basin offshore morocco deposition of these sequences occurred in similar unchannellized basin plain settings co genetic debrite turbidite beds were deposited from longitudinally segregated flow events comprising both debris flow and forerunning turbidity current it is most likely that the debris flow was generated by relatively shallow few tens of centimetres erosion of mud rich sea floor sediment changes in the settling behaviour of sand grains from a muddy fluid as flows decelerated may also have contributed to debrite deposition the association with distal settings results from the ubiquitous presence of muddy deposits in such locations which may be eroded and disaggregated to form a cohesive debris flow debrite intervals may be extensive 26 x 10 km in the marnoso arenacea formation and are not restricted to basin margins such long debris flow run out on low gradient sea floor 0 1 may simply be due to low yield strength 50 pa of the debris water mixture this study emphasizes that multiple flow types and transformations between flow types can occur within the distal parts of submarine flow events

response of unconfined turbidity current to normal fault topography turbidity currents descending the slopes of deep water extensional basins or passive continental margins commonly encounter normal fault escarpments but such large magnitude phenomena are hydraulically difficult to replicate at small scale in the laboratory this study uses advanced computational fluid dynamics numerical simulations to monitor the response of large natural scale unconfined turbidity currents 100 m thick and 2000 m wide at the inlet gate to normal fault topography with a maximum relief of nearly 300 m for comparative purposes the turbidity current is first released on a non faulted pristine slope of 1 5 simulation model 1 the expanding and waxing flow bypasses the slope without recognizable deposition within the vertical resolution limit of 2 m similar flow is then released towards the tip model 2 and towards the centre model 3 of a normal fault escarpment in both of these latter models the sand carried by flow tends to be entrapped in four distinct depozones an upslope near gate zone of flow abrupt expansion and self regulation a flow transverse zone at the fault footwall edge a flow transverse zone at the immediate hangingwall and a similar transverse zone near the crest of the hangingwall counter slope where some of the deposited sand also tends to be reshuffled to the previous zone by a secondary reverse underflow the near bottom reverse flow appears to be generated on a counter slope of 1 1 increased to 2 by deposition the kelvin helmholtz interface instability plays an important role by causing three dimensional fluctuations in the flow velocity magnitude and sediment concentration the thick deposits of large single surge flows may thus show hydraulic fluctuations resembling those widely ascribed to hyperpycnal flows the study indicates further that the turbiditic slope fans formed on such fault topographies are likely to be patchy and hence may differ considerably from the existing slope fan conceptual models when it comes to the spatial prediction of main sand depozones this article is protected by copyright all rights reserved

pollen studies at lake st croix a river lake on the minnesota wisconsin border usa lake st croix at the downstream end of the st croix river was formed when a natural dam was constructed across its mouth by the mississippi river which has aggraded its floodplain in holocene time since the termination of deep erosion by the glacial river warren the outlet for glacial lake agassiz until about 9500 bp pollen analysis and radiocarbon dating of a 19 m core from the uppermost basin of the lake shows a rapidly increasing rate of sedimentation and pollen influx since 3000 bp and especially since 1300 bp as the delta of the st croix river approached the coring site the pollen sequence closely resembles that for lily lake which is located on the moraine upland a few kilometres to the west its pollen assemblage differs from that for lake st croix more because of its upland location slightly to the west than to influx of river sediment in lake st croix

confidence intervals for age estimates and deposition times in late quaternary sediment sequences distribution sampling from sequences of radiocarbon ages is used to obtain confidence intervals for intermediate age estimates sediment deposition times and thence pollen deposition rates three

diatom indicators of peatland development at pogonia bog pond minnesota usa sediment cores were taken from the central pond and fringing mat of a sphagnum peatland located in the big woods vegetation type pollen analysis of the pond core spanning 12 000 cal bp to the pre

late carboniferous tectonic subsidence in south wales implications for variscan basin evolution and tectonic history in sw britain detailed stratigraphic data have been used to backstrip seven sections from the carboniferous south wales coal basin resulting tectonic subsidence curves for the interval 319 305 ma namurian westphalian d are convex up indicating increasing subsidence rate with time with rates between 130 and 250 m ma 1 suggesting a foreland basin setting forward modelling of subsidence due to flexural loading in front of a propagating orogenic wedge shows that an orogenic load migrating in a north northeasterly direction across sw england between 319 and 305 ma could have generated the backstripped subsidence patterns sensitivity tests show that while many of the forward model parameters are poorly constrained and the model results non unique backstripped subsidence patterns allow reasonable constraint on the different model cases so that model predictions can be treated as one possibility in a limited range the predicted load evolution is consistent with current knowledge of tectonic and stratigraphic features of sw england these results suggest that subsidence in other late carboniferous uk basins may also have been influenced by flexure due to a propagating orogenic load

sensitivity of late glacial and holocene climates to the combined effects of orbital parameter changes and lower boundary condition changes snapshot simulations with a general circulation model for 18 9 and 6 ka bp

response of bankfull flood magnitudes to holocene climate change uinta mountains northeastern utah long term variations in holocene fl ood magnitude were quantifi ed from the bankfull dimensions of abandoned channels preserved on flsurfaces in the northern uinta mountains of northeastern utah cross sectional areas of abandoned channels were reconstructed and relationships derived from the modern gage records were used to estimate bankfull discharges from bankfull cross section areas the results indicate systematic nonrandom variations of bankfull fl oods in the northern uinta mountains large fl oods as much as 10 15 greater than modern dominated from 8500 to 5000 calendar yr b p and again from 2800 to 1000 cal yr b p small fl oods as much as 15 20 less than modern characterize the periods from 5000 to 2800 cal yr b p and from 1000 cal yr b p to near present the middle and late holocene record of bankfull fl ood magnitude compares well with independent evidence for climatic variation in the area the early holocene record indicates that larger than modern bankfull fl oods coincide with warmer than modern mean annual temperature we hypothesize that an increased range of magnitude for seasonal solar radiation during the early holocene favored the accumulation and rapid melting of deep snowpacks in the high uinta mountains thus producing large fl oods despite warmer mean annual temperatures the episode of smaller than modern bankfull fl oods between 5000 and 2800 cal yr b p coincides with records of increased forest fi re frequency in the northern uintas larger than modern fl oods from 2800 to 1000 cal yr b p coincide with a local decrease in forest fi re frequency and evidence for minor local glacial readvances the decrease in fl magnitudes following 1000 cal yr b p corresponds to numerous local and regional records of warming during the medieval climatic anomaly

methods of interpretation of borehole falling head tests performed in compacted clay liners the interpretation of falling head tests in cased boreholes is discussed these tests are commonly used to measure hydraulic conductivity of compacted clay liners and are often part of the construction quality assurance program three methods of interpretation are reviewed with data sets collected from real tests two of these methods have been the subject of past research by other authors the hvorslev or time lag method and the velocity method after the limitations of these two approaches have been underlined a third method is proposed it uses a best linear unbiased estimator to fit the theoretical head difference function in a plot of falling water column elevation as a function of time z t method the hvorslev method is found unreliable and is not recommended the velocity method is theoretically sound but statistical uncertainty can become high when this method is used in testing materials with low hydraulic conductivity such as clay liners materials with low hydraulic conductivity tend to

multiple early holocene climate oscillations at silver lake new jersey and their possible linkage with outburst floods abstract episodic discharges from the laurentide ice sheet are considered to be one of the major causes of climate oscillations during the glacial to interglacial transition these outburst floods disrupted thermohaline circulation and might have caused cooling events in the north atlantic region and beyond including the younger dryas preboreal oscillation and 8 2 ka events however few terrestrial sedimentary records show regional climate changes directly linked to outburst floods during the early holocene here we present lithologic and isotopic data from silver lake in northern new jersey to document temperature and moisture changes during the early holocene and to discuss possible linkage with outburst flooding events the lithologic record shows multiple intervals with coupled decreases in carbonate and increases in organic matter during the early holocene suggesting lower lake levels and drier climate conditions simultaneous with these changes were decreases in carbonate 18 o values likely reflecting a decrease in air temperature during these dry periods the apparent correlation of these sedimentary events at silver lake with documented outburst floods from the melting ice sheet suggests a possible causal connection implying that the climate in the mid atlantic region was extremely sensitive to perturbations of ocean circulation