quaternary paleolake nutrient evolution and climatic change in the western qaidam basin deduced from phosphorus geochemistry record of deep drilling core sg 1 abstract phosphorus p provides an important biologically limiting nutrient in lake ecosystems and its concentrations furnish significant information on lake nutrient status climatic change and landscape development within a drainage area this study explores the potential of calcium bound p and iron bound p in calcareous lacustrine sediments to reveal variations of the paleolake nutrient status and its related climatic changes data come from the nearly 1000 m long core sg 1 from the western qaidam basin ne tibetan plateau which has been well dated by paleomagnetism to between 2 77 and 0 1 ma calcium bound p and iron bound p make up the two most frequent phases of inorganic phosphorus pools in the calcareous sediment this study compares the variations of calcium bound p and iron bound p with the independent proxy for biologic production proxy total organic carbon toc as well as a climatic proxy for lake level fluctuation from the borehole those results indicate that calcium bound p responds sensitively to paleolake nutrients and climatic changes while the iron bound p responds to more complex factors more specific to the content of iron oxides variations of the calcium bound p in the core sg 1 show a long term stepwise decrease with shifts at 2 5 ma 1 8 ma 1 2 ma and 0 6 ma indicating a long term stepwise decrease of the paleolake nutrient supply in the drainage this suggests that the ecologic systems experienced a long term deterioration and the climate in central asia became increasingly arid since after the late pliocene

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

a lacustrine sedimentary record of holocene periglacial activity from the uinta mountains utah u s a abstract a lake sediment core from the uinta mountains of northern utah was analyzed to constrain the timing of late holocene periglacial activity records of numerous physical properties were converted to time series spanning the past 5300 years using a depth age model based on four ams 14 c dates long term decreases in organic content and increases in bulk density attest to increasing inputs of clastic sediment abundance of mineral p signaling physical bedrock weathering reaches maximum values ca 2900 2150 and 1400 cal yr bp coincident with finer median grain size and a shift toward darker red sediment these peaks interpreted as signals of periglacial activity align with pulses of rock glacier activity in colorado determined from lichenometry the youngest peak coincides with lichenometric ages previously determined for periglacial deposits upstream from the lake a pulse of renewed periglacial activity ca 400 cal yr bp represents the little ice age the late 20th century witnessed extremely high values of organic matter and biogenic silica and unprecedented low values of c n reflecting greatly enhanced in lake productivity likely due to disturbance in the watershed

holocene environmental changes as recorded in the geochemistry of glacial lake sediments from retezat mountains south carpathians abstract sediment cores obtained from two deep 15 m glacial lakes were analyzed in context of terrestrial vegetation development and in lake processes from the retezat mountains southern carpathians romania only the holocene parts were chosen for study for testing what is the connection between geochemical changes and biotas around and in the lakes the lakes are situated at slightly different altitudes on the northern lake gales 1990 m a s l and southern slope lake bucura 2040 m a s l respectively changes in geochemical composition were relatively low amplitude during the studied period 10 300 1790 and 10 300 695 cal yr bp in both lakes but the applicability of enrichment factor ef for geochemical elements and diatom ecological traits guilds in paleoecological reconstruction were demonstrated in this paper the main changes have been observed at ca 10 670 9000 6500 and 3100 cal yr bp in geochemistry vegetation and siliceous algal assemblages catchment soil stabilization was apparent from 9000 cal yr bp onwards in lake and terrestrial productivity was the highest between 9000 and 6500 cal yr bp and human impact became the dominant driver in both terrestrial vegetation and sediment geochemical changes and in lake processes over the last 3400 years in both lakes the geochemical record displayed frequent erosional events within the holocene the strongest soil erosions clustered around 6500 7400 and 3200 900 cal yr bp

mid holocene glacier expansion between 7500 and 4000 cal yr bp in the british columbia coast mountains canada the mid holocene behaviour of five glaciers in the british columbia coast mountains was reconstructed from radiocarbon ages and stratigraphic analysis subfossil wood evidence at canoe fyles jaco

neoglaciation in the southern coast mountains of british columbia chronology prior to the late neoglacial maximum moraine stratigraphy and morphology radiocarbon dates from klinaklini franklin tiedemann gilbert and bridge glaciers and related information from elsewhere in the coast mountains are used to construct a chronology for glacier fluctuations the garibaldi phase of glacier expansion 6000 5000 14c years bp at the end of the early holocene xerothermic interval is indicated by overridden tree stumps the mid neoglacial tiedemann advance 3300 1900 14c years bp is represented by moraines till and meltwater sediments at three glaciers but only tiedemann glacier attained its greatest holocene extent at this time late neoglacial expansion commenced before 900 14c years bp and continued without notable interruption until glaciers achieved their maximum post pleistocene expansion during the eighteenth and nineteenth centuries evidence for the garibaldi and tiedemann events is scarce within the coast mountains because of the more extensive late neoglacial advance however correlative advances have been

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

episodes of low dissolved oxygen indicated by ostracodes and sediment geochemistry at crystal lake illinois usa low dissolved oxygen during the summer and early fall controls profundal continental ostracode distribution in crystal lake mchenry county illinois favoring cypria ophthalmica and physocypria globula at water depths from 6 to 13 m these species also thrived in the lake s profundal zone from 14 165 to 9600 calendar year before present cal yr b p during the late bolling allerod and younger dryas chronozones and early holocene characterized by sand cemented tubules large aquatic gastropod shells and littoral ostracode valves thin 1 6 cm tempestite deposits punctuate thicker deposits of organic gyttja from 16 080 to 11 900 cal yr b p the succeeding 2300 yr 11 900 9600 cal yr b p lack tempestites and reconstructed water depths were at their maximum deposition of marl under relatively well oxygenated conditions occurred during the remainder of the holocene until the arrival of europeans when the lake returned to a pattern of seasonally low dissolved oxygen such conditions are also indicated in the lake sediment by the speciation of phosphorus high concentrations of organic carbon and abundant iron and manganese occluded to mineral grains initial low dissolved oxygen was probably caused by the delivery of dissolved p and fe in shallow groundwater the chemistry of which was influenced by spodosol pedogenesis under a spruce forest the triggering may have been regionally warm and wet conditions associated with retreat of the lake michigan lobe south central laurentide ice sheet

western canadian glaciers advance in concert with climate change circa 4 2 ka 1 disparate climate proxies from the northern hemisphere record a climate event at 4 2 3 8 ka here we show that glaciers throughout the mountain ranges of western canada advanced at about this time this conclusion is based on 1 new and previously reported radiocarbon ages on in situ stumps logs branches and soils exposed by recent retreat in glacier forefields and 2 clastic rich sediment intervals in cores retrieved from four montane lakes these glacier and lacustrine data indicate a period of several decades to century length when climate conditions cool summers wet winters or both favoured glacier nourishment and advance across western canada

early holocene monsoonal fluctuations in the garhwal higher himalaya as inferred from multi proxy data from the malari paleolake abstract a 4 9 m thick lake sequence formed due to the landslide damming of a stream in the semiarid garhwal himalaya was studied to understand past monsoonal variations in the region the optically stimulated luminescence osl chronology indicates that the lake existed between 12 and 7 ka ago chronologically constrained trends of sand percent organic phosphorus op apatite inorganic phosphorus aip and parameters of environmental magnetism were measured in the paleolake profile measured proxies indicate that the indian summer monsoon ameliorated in the early holocene after 12 ka cooling and it appears that all the proxies from the lake have captured this globally recognized early holocene warming four phases of wet conditions intensified monsoon are recognized at 11 5 ka 11 10 5 ka 10 9 ka and 8 7 ka with maximum uncertainties of 1000 years the wet phases are characterized by high magnetic susceptibility increased op and reduced aip in an attempt to understand the primary forcing of the sharp fluctuations in monsoonal activity in the region we show that changes in magnetic susceptibility match variations of residual atmospheric 14c suggesting a role for solar variability as an explanation of climatic variability

surface rupture of the 1857 southern italian earthquake in october 1862 robert mallet published an extensive study of a large earthquake that occurred on 16 december 1857 150 km south east of naples this event is one of the most destructive ever recorded in italy although continental earthquakes of similar size are almost invariably associated with surface faulting mallet did not identify any surface rupture and subsequent workers have also failed to find surface traces using satellite images and aerial photographs as a guide we examined two prominent quaternary normal fault systems in the field flanking the val d agri and the val di diano both trend nw se and dip to the sw the distribution of damage suggests that one or both moved in 1857 on one fault segment in val d agri we found a 2 5 m high scarp whose youthfulness and height suggest it is due to the 1857 earthquake comparison of the observed slip with rates derived from geomorphic evidence suggests a recurrence time for 1857 type events of about 3000 years while the new data we provide are consistent with the event having a magnitude of ms 7 0 there are also grounds for supposing it might have been bigger

glacier change in western north america influences on hydrology geomorphic hazards and water quality the glaciers of western canada and the conterminous united states have dominantly retreated since the end of the little ice age lia in the nineteenth century although average rates of retreat varied from strong in the first half of the twentieth century with glaciers stabilizing or even advancing until 1980 and then resuming consistent recession this retreat has been accompanied by statistically detectable declines in late summer streamflow from glacier fed catchments over much of the study area although there is some geographical variation over recent decades glaciers in northwest bc and southwest yukon have lost mass dominantly by thinning with relatively low rates of terminal retreat and glacier fed streams in that region have experienced increasing flows in many valleys glacier retreat has produced geomorphic hazards including outburst floods from moraine dammed lakes mass failures from oversteepened valley walls and debris flows generated on moraines in addition to these hydrologic and geomorphic changes evidence is presented that glacier retreat will result in higher stream temperatures possibly transient increases in suspended sediment fluxes and concentrations and changes in water chemistry with climate projected to continue warming over the twenty first century current trends in hydrology geomorphology and water quality should continue with a range of implications for water resources availability and management and hydroecology particularly for cool and cold water species such as salmonids copyright 2008 john wiley sons ltd

early holocene thermal maximum in western north america new evidence from castle peak british columbia conifer logs and branches of early holocene age are common on the surface and in sediments above timberline at castle peak in the southeastern coast mountains of british columbia a study of this wood and associated peat and colluvium has shown that local timberline from 9 1 to 8 2 ka was at least 60 m and perhaps more than 130 m higher than today mean growing season temperature at castle peak during this period thus may have been 0 4 0 8 c warmer than at present this is consistent with theoretical considerations based on milankovitch forcing of climatic change and is supported by other paleoecological data from the southern canadian cordillera and adjacent northwestern united states a generally warm climate may have persisted until about 5 6 ka followed by late holocene cooling

holocene glacier fluctuations in the canadian cordillera alberta and british columbia abstract although the record of holocene glacier fluctuations in british columbia and alberta is still very fragmentary much recent progress has been made in their study dating of end moraines has been supplemented by studies of lateral moraine stratigraphy and dating of glacially overridden organic matter upstream of end moraines dates from sites close to contemporary glaciers indicate that ice had retreated to about its present limits before 10 ka bp prior to deposition of mazama tephra a minor pre hypsithermal readvance the crowfoot advance left deposits in the rockies and the interior of british columbia the earliest known neoglacial advances occurred 5 6 ka bp in the coast mountains and shortly after 4 ka bp in the rockies an advance culminating ca 4 3 ka bp has been reported from bugaboo glacier while evidence of another advance culminating in the period ca 2 5 1 8 ka bp the tiedemann advance is reported from more than one site following a recession the little ice age expansion the cavell advance began shortly after 900 bp this advance culminated in most cases in the 18th or 19th centuries the crowfoot tiedemann and little ice age advances were apparently of roughly the same magnitude the latter was most extensive in most cases but at several sites crowfoot moraines lie slightly farther downvalley than little ice age moraines during the present century ice fronts have generally retreated particularly rapidly in the period 1920 1950 a d although rates of retreat have decreased in the last three decades and some glaciers have readvanced slightly

palaeomagnetic dating of late holocene sediments in fennoscandia abstract palaeomagnetic secular variation curves that have been dated by varve analysis counting annual laminations are used to date four holocene lacustrine sediment sequences from central finland and northwest russia lat 62 66 n several fine scale geomagnetic declination and inclination fluctuations can be identified during the last 3200 yr which is the most accurately dated interval in the present data relative palaeomagnetic dating is a powerful dating tool for sediments of large and deep lakes in northern europe which are difficult to date using the 14 c method because of low organic content contamination by older carbon and or scarcity of terrestrial macrofossils suitable for ams 14 c dating the dating error during the last 3200yr is estimated to be less than 50 yr such accuracy is not readily attainable using other methods

sediment source and hydroclimatic inferences from glacial lake sediments the postglacial sedimentary record of lillooet lake british columbia lillooet river drains 3850 km2 of partly glacier covered terrain before entering lillooet lake in the southern coast mountains of british columbia the elongated lake covers an area of 21 km2 and forms a deep basin with water depths to 137 m acoustic profiling of the subbottom and sampling of the surface sediments reveals that total sediment thickness varies from 30 m in the north half of the lake near lillooet delta and then declines to less than 16 m in the south up valley ice retreat approximately 11 000 years bp resulted in conformable sediments in the main lake indicative of turbidity currents off lillooet delta which infilled and flattened the underlying surface a sill which separates the main and south basins prevents the down lake progression of turbidity currents resulting in conformable deposits indicative of rain out i e settling processes only a major acoustic reflector at about 6 9 m below the modern sediment surface is associated with a well dated volcanic eruption and sediment yield event in the upper basin at 2400 years bp modern glaciolacustrine deposition forms varves which accumulate at a rate of up to 28 mm year 1 in the north and decline to less than 0 9 mm year 1 in the south the occurrence of two sediment runoff regimes one average and the other extreme leads to distinct differences in varve sedimentology and varve thickness de coupling the two signals using sedimentary evidence alone cannot be done consistently so a sediment yield runoff relation for the lake r2 41 contains considerable noise an annual sediment accumulation chronology covering the last 125 years shows a much higher frequency of extreme runoff sediment yield events during the post 1940 interval this parallels a documented change in climate of the region after 1945 and suggests that a longer varve chronology would provide a good high resolution proxy record of hydroclimatic variations

xanes spectroscopy as a tool to trace phosphorus transformation during soil genesis and mountain ecosystem development from lake sediments the aim of this study is to investigate phosphorus p species modifications triggered by soil genesis and mountain ecosystem development after glacial retreat using a lake sediment archive lake anterne north french alps five lake sediment samples representative of different stages of soil and ecosystem development were selected for p speciation analyses furthermore a sequence of current soils from the catchment was analyzed to better constrain our interpretations of the lacustrine archive synchrotron techniques x ray fluorescence xrf mapping and p k edge x ray absorption near edge structure xanes spectroscopy were applied to lake sediments soils and standards mineral and organic to distinguish between different p species the results show that soil development during the first millennia of the holocene triggered increased p species diversity at the onset of the holocene p was present as apatite when rocks and leptosols dominated the catchment pedogenic processes then led to apatite dissolution and the formation of large amounts of p on metal clay organic complexes p geochemistry during the main step of soil genesis early leptosols dominated by apatite low weathered cambisols with p mainly adsorbed on iron oxides highly weathered podzols with large amounts of p on al fe clay organic complexes is thus clearly recorded in lake sediments p k edge xanes spectroscopy is particularly relevant as qualitative method to study p species in soils and lake sediments at high spatial resolution such resolution is needed to reveal the diversity of small p particles and like this better characterize the p cycle and improve our understanding of ecosystem evolution

deep structure of the southern apennines italy thin skinned or thick skinned 1 the deep structure of the southern apennines sa accretionary wedge is still debated since industrial seismic reflection and well data provide reliable constraints only to a depth of about 10 km as a consequence two directly linked questions regard 1 the shortening in the accretionary prism particularly within the buried apulian thrust units and 2 the degree of involvement of the lower plate basement i e the apulian crystalline basement to address these issues we have constructed a regional section along a recently released deep seismic reflection profile crop 04 which intersects the entire sa the resulting cross section adequately constrained to a depth of about 15 km has been framed in a geodynamic scenario characterized by the eastward roll back of the westward subducting apulo adriatic lithosphere on the basis of this section we speculate on the deep structure building both thin and thick skinned thrust models a cross check of these end members models against documented tectonic geophysical and geochemical features shows that the thin skinned model is generally more consistent with the available data the development of basement slices with thicknesses of tens of kilometers is unlikely while it remains possible that the apulian basement could have been involved with its upper few kilometers in the thin skinned model the total shortening of the allochthonous units i e apennine and apulian carbonate platforms and lagonegro basin is estimated to be greater than 280 300 km some 90 km of shortening can be attributed to the apulian thrust units

latest pleistocene and holocene glacier fluctuations in western canada we summarize evidence of the latest pleistocene and holocene glacier fluctuations in the canadian cordillera our review focuses primarily on studies completed after 1988 when the first comprehensive review of such evidence was published the cordilleran ice sheet reached its maximum extent about 16 ka and then rapidly decayed some lobes of the ice sheet valley glaciers and cirque glaciers advanced one or more times between 15 and 11 ka by 11 ka or soon thereafter glacier cover in the cordillera was no more extensive than at the end of the 20th century glaciers were least extensive between 11 and 7 ka a general expansion of glaciers began as early as 8 4 ka when glaciers overrode forests in the southern coast mountains it culminated with the climactic advances of the little ice age holocene glacier expansion was not continuous but rather was punctuated by advances and retreats on a variety of timescales radiocarbon ages of wood collected from glacier forefields reveal six major periods of glacier advance 8 59 8 18 7 36 6 45 4 40 3 97 3 54 2 77 1 71 1 30 ka and the past millennium tree ring and lichenometric dating shows that glaciers began their little ice age advances as early as the 11th century and reached their maximum holocene positions during the early 18th or mid 19th century our data confirm a previously suggested pattern of episodic but successively greater holocene glacier expansion from the early holocene to the climactic advances of the little ice age presumably driven by decreasing summer insolation throughout the holocene proxy climate records indicate that glaciers advanced during the little ice age in response to cold conditions that coincided with times of sunspot minima priority research required to further advance our understanding of late pleistocene and holocene glaciation in western canada includes constraining the age of late pleistocene moraines in northern british columbia and yukon territory expanding the use of cosmogenic surface exposure dating techniques using multi proxy paleoclimate approaches and directing more of the research effort to the northern canadian cordillera

holocene climate variability although the dramatic climate disruptions of the last glacial period have received considerable attention relatively little has been directed toward climate variability in the holocene 11 500 cal yr b p to the present examination of similar to50 globally distributed paleoclimate records reveals as many as six periods of significant rapid climate change during the time periods 9000 8000 6000 5000 4200 3800 3500 2500 1200 1000 and 600 150 cal yr b p most of the climate change events in these globally distributed records are characterized by polar cooling tropical aridity and major atmospheric circulation changes although in the most recent interval 600 150 cal yr b p polar cooling was accompanied by increased moisture in some parts of the tropics several intervals coincide with major disruptions of civilization illustrating the human significance of holocene climate variability c 2004 university of washington all rights reserved

effects of climate and landscape development on the terrestrial phosphorus cycle past variations in the terrestrial cycle of phosphorus p a biolimiting nutrient are poorly understood detailed geochemical analysis of p in lake sediment cores spanning the late pleistocene to the present from the western appalachian plateau the coast mountains of british columbia and the san bernardino mountains of southern california reveal large changes in terrestrial p cycling p is transformed from a mineralized form to more bioavailable forms with increased soil development and landscape stability in the catchments this process occurs relatively rapidly i e within 3 000 5 000 yr and can be reset quickly the degree of transformation depends on local climate and the starting point of the soil system the release of solid phase p from these landscapes follows modeled patterns of high rates during the initial stages of soil development and low rates upon soil and landscape stabilization changes in weathering style were confirmed for the southern california catchment by analysis of ge si ratios of lake diatoms which revealed substantially higher values during an interval of high p release and low values at present these records point to significant variability in the terrestrial p mass balance on glacial time scales a feature that needs to be incorporated into models of nutrient andmore carbon cycling in the past less

sequential extraction and analysis of phosphorus in marine sediments streamlining of the sedex procedure we streamlined the five step sedex sedimentary extraction procedure for characterizing sedimentary phosphorus to a four step procedure we combined extraction of adsorbed and oxide associated pools into a single step retaining steps for authigenic detrital and organic p in addition we used automated spectrophotometric flow injection analysis fia to determine p concentrations rather than traditional spectrophotometric techniques we decreased our total extraction and analytical time from 12 d for 24 replicate samples to 5 d without sacrificing our geo chemical objectives detection limits or analytical reproducibility

alpine lake sediment records of the impact of glaciation and climate change on the biogeochemical cycling of soil nutrients lake sediment cores from the coast mountains of british columbia were analyzed using chemical sequential extractions to partition the dominant geochemical fractions of phosphorus p the p fractions include mineral p the original source of bioavailable p occluded p bound to soil oxides and organic p remains of organic matter by comparing p fractions of soil and recent lake sediment samples these fractions are shown to be a valid proxy for landscape scale nutrient status changes in soil development for an alpine watershed lower joffre lake are inferred from the p fractions in the basin s outlet lake sediments glacially sourced mineral p dominates at the base of the core but several rapid shifts in p geochemistry are evident in the first 3000 yr of the record the latter indicates an interval of early and rapid soil nutrient maturation from 9600 to 8500 cal yr bp and a significant influx of slope derived material into lower joffre lake a substantial increase in mineral p occurs at ca 8200 cal yr bp consistent with the cold event in the vicinity of the north atlantic at that time the more recent record reveals a continual increase in the proportion of mineral p from glacial sources to the lake indicating a trend toward cooler conditions in the coast mountains

late quaternary activity of the scorciabuoi fault southern italy as inferred from morphotectonic investigations and numerical modeling 1 following a detailed morphotectonic analysis of the fluvial terraces of the sauro river basilicata southern italy the present research documents for the first time the late quaternary tectonic activity of the scorciabuoi fault and discusses its inferred seismogenic potential on the basis of both remote sensing techniques and detailed field investigations four fill terraces have been recognized and mapped along the sauro valley showing differential cumulative displacements across the fault these terraces are genetically correlated with four highstand sea level periods following stratigraphic and geological age constraints and on the basis of the correlation with a sequence of marine and fluvial terraces characterizing the lower agri valley the sauro terraces likely formed between 80 or 100 ka and present the inferred long term slip rate of the scorciabuoi fault ranges between 0 5 and 1 0 mm a numerical simulations based on a crustal elastic deformation model also contribute to separate and tentatively quantify the regional uplift rate 1 0 1 4 mm a and to improve the overall reconstruction of the late quaternary evolution of the area the synergic but distinct roles played by eustatism regional uplift and faulting are eventually appreciated

a lacustrine based neoglacial record for glacier national park montana usa abstract multi proxy study of sediment cores retrieved from lakes below modern glaciers supports the first detailed neoglacial chronology for glacier national park gnp montana analysis focused on sedimentary properties sensitive to the extent and activity of upstream glacier ice including water organic matter carbonate and biogenic silica content bulk density mass accumulation rate phosphorus fractionation magnetic susceptibility l a b color values and grain size distribution results indicate that alpine glaciers in gnp advanced and retreated numerous times during the holocene after the onset of neoglaciation ca 6500 bp the two oldest phases of glacier expansion were synchronous with the well documented garibaldi 5600 6900 bp and tiedemann peyto 1900 3700 bp phases in western canada younger phases correspond with the first millennium advance in western canada as well as glacier with advances in the sierra nevada the culminating little ice age lia advance was the most recent and extensive of a series of advance retreat cycles over the past millennium retreat from the lia maximum was the most dramatic episode of ice retreat in at least the last 1000 years

use of lacustrine sedimentary sequences as indicators of holocene glacial history banff national park alberta canada abstract bottom sediments from three lakes in the canadian rocky mountains were examined with the aim of evaluating the usefulness of downvalley sediment studies in reconstruction of holocene glacial histories analyses of organic carbon and carbonate contents of core sediments provide information on changing sedimentation rate and changing relative importance of glacial and non glacial sediment sources sedimentary histories of the three lakes are similar suggesting that they record regional glacial climatic forcing rather than localized events and thus that they may be useful in reconstructing holocene glacial history lacustrine sediments indicate a period of high sedimentation rates and relatively large glacial sediment contribution prior to 7500 7000 yr b p with much reduced rates and decreased glacial sediment contribution between about 6000 and 4000 yr b p possibly interrupted by a brief period of increased glacial sediment output shortly after 5000 yr b p sometime after 4000 yr b p sedimentation rates and glacial sediment output began to rise again reaching approximately present levels by 2750 2650 yr b p and have not since returned to low mid holocene levels in detail over the last 3000 yr there is some indication of a slight decrease in sedimentation rate for more than 1000 yr after about 2200 yr b p sedimentation rates and glacial sediment input into all three lakes rose between about 900 and 750 yr b p and have remained very high since if the lake sediments are interpreted as a proxy record of upvalley glacial activity they allow the development of a glacial chronology which is at once generally consistent with and more complete and easily datable than the surficial glacial record

the little ice age in the canadian rockies abstract this paper reviews the evidence and history of glacier fluctuations during the little ice age lia in the canadian rockies episodes of synchronous glacier advance occurred in the 12th 13th early 18th and throughout the 19th centuries regional ice cover was probably greatest in the mid 19th century although in places the early 18th century advance was more extensive glaciers have lost over 25 of their area in the 20th century selective preservation of the glacier record furnishes an incomplete chronology of events through the 14th 17th centuries in contrast varve sequences provide continuous annually resolved records of sediments for at least the last millennium in some highly glacierized catchments such records have been used to infer glacier fluctuations evaluation of recent proxy climate reconstructions derived from tree rings provides independent evidence of climate fluctuations over the last millennium most regional glacier advances follow periods of reduced summer temperatures reconstructed from tree rings particularly ca 1190 1250 1280 1340 1690s and the 1800s reconstructed periods of higher precipitation at banff alberta since 1500 are 1515 1550 1585 1610 1660 1680 and the 1880s glacier advances in the early 1700s the late 1800s and in places the 1950 1970s reflect both increased precipitation and reduced summer temperatures negative glacier mass balances from 1976 to 1995 were caused by decreased winter balances the glacier fluctuation record does not contain a simple climate signal it is a complex response to several interacting factors that operate at different timescales evaluation of climate proxies over the last millennium indicates continuous variability at several superimposed timescales dominated by decade century patterns only the 19th century shows a long interval of sustained cold summers this suggests that simplistic concepts of climate over this period should be abandoned and replaced with more realistic records based on continuous proxy data series the use of the term lia should be restricted to describing a period of extended glacier cover rather than being used to define a period with specific climate conditions

neoglacial glacier fluctuations in the canadian rockies abstract the little ice age was the most extensive neoglacial glacier advance in the canadian rockies evidence of earlier less extensive neoglacial glacier advances is based on wood recovered from several glacier forefields wood flushed out of athabasca glacier 7550 8230 yr b p three dates and dome glacier 6120 6380 yr b p two dates indicates that forests occurred upvalley of present glacier termini during the hypsithermal detrital logs from peyto 14 dates saskatchewan 3 dates robson 3 dates and yoho 1 date glaciers plus in situ slumps at peyto and robson glaciers have yielded 14 c dates between 2490 and 3300 yr b p 12 dates between 2800 and 2990 this wood is derived from sources at or upvalley from present glacier termini and represents forests overridden by glaciers between ca 3100 and 2500 yr b p treeline was higher than present immediately prior to this advance this advance which did not extend beyond the little ice age maximum position is designated the peyto advance and correlated with the tiedemann advance in western british columbia earliest little ice age advances at peyto and robson glaciers are dated ca 800 600 yr b p at positions ca 500 m upvalley from little ice age limits

early holocene glacier advance southern coast mountains british columbia canada abstract terrestrial and lake sediment records from several sites in the southern coast mountains british columbia provide evidence for an advance of alpine glaciers during the early holocene silty intervals within organic sediments recovered from two proglacial lakes are bracketed by ams 14 c dated terrestrial macrofossils and mazama tephra to 8780 6730 and 7940 6730 14 c yr bp 10 150 7510 and 8990 7510 cal yr bp radiocarbon ages ranging from 7720 to 7380 14 c yr bp 8630 8020 cal yr bp were obtained from detrital wood in recently deglaciated forefields of sphinx and sentinel glaciers these data together with previously published data from proglacial lakes in the canadian rockies imply that glaciers in western canada advanced during the early holocene the advance coincides with the well documented 8200 yr cold event identified in climate proxy data sets in the north atlantic region and elsewhere

optical dating studies of postglacial aeolian deposits from the south central interior of british columbia canada abstract tests of the validity of optical dating of the fine grained 4 11 m component of aeolian deposits from six sites in south central british columbia using 1 4 ev infrared excitation of potassium feldspars were made making use of known age tephra beds at one site on the western side of the fraser valley samples bracketing the mazama 7 5 7 6 ka cal yrs and bridge river tephras 2 3 ka cal yrs yielded optical ages in accordance with the known ages when a correction for thermal transfer was used the same method was applied to aeolian deposits on the fraser plateau known to have been deposited between 14 and 2 3 ka cal yrs the ages obtained from five samples from four separate exposures spanning 10 km varied from 30 to 94 ka clearly indicating that this sediment was not exposed to sufficient sunlight prior to burial as a result of a detailed investigation it is suggested that the reason is that some grains had been transported over short distances

holocene tree line and climate change on the queen charlotte islands canada palynological study of two subalpine ponds on the queen charlotte islands reveals changes in tree line and climate during the holocene the findings agree with previous reconstructions from nearby louise pond on the queen charlotte islands that suggest a warmer than present climate and higher than present tree lines in the early holocene ca 9600 660014c yr b p basal ages at sc1 pond and shangri la bog indicate that the basins did not hold permanent water before 720014c yr b p consistent with a warmer and drier early holocene previously inferred from louise pond pollen and plant macrofossils indicate the initial establishment of subalpine conditions by 6090 9014c yr b p similar to the 5790 13014c yr b p age for cooling inferred from louise pond conditions similar to present were established at sc1 pond by 3460 10014c yr b p confirming the previous estimate of 340014c yr b p at louise pond this 340014c yr b p vegetation shift on the queen charlotte islands corresponds with the beginning of the tiedemann glacial advance in the south coastal mountains of british columbia ca 330014c yr b p the peyto and robson glacial advances between 3300 and 280014c yr b p in the rocky mountains and climatic cooling inferred from palynological studies throughout southern british columbia northern washington and southeast alaska these findings confirm that changes in regional climate influenced changes in vegetation in coastal british columbia

improved age estimates for the white river and bridge river tephras western canada new 14c ages date the eruptions that produced the white river and bridge river tephras two important holocene marker beds in western canada the 14c ages were obtained on trees in growth position buried in coarse tephra and a pyroclastic flow near the source vents the mean calendric age of the white river eruption based on four 14c ages is 1147 cal years bp calibrated years approximately equivalent to calendric years or ad 803 the 2 age range obtained from the two most precise 14c ages is 1014 1256 cal years bp or ad 694 936 the mean age of the bridge river eruption determined both from i the single most precise outer ring 14c age and ii the weighted mean of six outer ring 14c ages is 2360 cal years bp or 411 bc 2 age range 2349 2704 cal years bp or 755 400 bc