Post-Marquette discharge from Glacial Lake Agassiz into the Superior basin

Glacial Lake Agassiz, the largest of the North American glacial lakes, discharged through several different outlets during its history, although the timing and location of discharge remain controversial. However, one discharge event is well established based on extensive onshore observations: drainage through the Nipigon Lake area into the Superior basin about 10,700 years ago, following retreat of ice of the Marquette advance from the basin. High-resolution, single-channel seismic-reflection data collected with a small airgun were acquired to test the hypothesis that the Post-Marquette drainage event left diagnostic stratigraphic and geomorphic signatures beneath Lake Superior. The unique bathymetry of northwestern Lake Superior, where water depth plunges off Nipigon and Black Bays, makes this location ideal for the characterization of the post-Marquette depositional and erosional features. According to our hypothesis, the initial, sudden discharge of high-velocity water would have eroded channels through the bays. The steep and sudden drop-off into the Superior basin would have caused the flow to slow and drop much of the sediment it was carrying. Our results confirm the existence of both erosional features and depositional sediment packages related to Lake Agassiz discharge at this time. The erosional features include deeply incised bedrock channels in the bays. The depositional features comprise subaqueous fans that are thickest in the deep water areas adjacent to the outlets and thin lakeward and laterally away from the channels. The seismic character of the basal units of the fans, proximal to the channels, is chaotic and only very weakly stratified, suggesting that these deposits represent coarse sediment laid down during the initial, high-energy stages of the flood. These sediments are overlain by a stratified package which is interpreted as the fine grained sediment associated with the later, low-energy stages of the flood. The combination of channels and subaqueous fans is inferred to be diagnostic of high-energy Lake Agassiz discharge into the Superior basin, and they serve as analogs for hypothesized discharge at other times.     

Geological and geophysical evidence for pre-Nipissing (>5,000 years BP) transgression infilled valleys in the Lake Huron basin,Ontario

Lake Algonquin, the largest glacial lake of the Great Lakes area, ended prior to 10,000 years BP by drainage to the Ottawa Valley as the North Bay outlet was deglaciated. At that time, the outlet area was isostatically downwarped more than 100 m; resulting low water, river-linked lakes Chippewa, Stanley, and Hough, lowstands in the basins of lakes Michigan, Huron, and Georgian Bay respectively, were much below present lake level. While water levels were low, about half of the present lake area was dry land. The land above the lowstands was dissected by streams and became forested. Uplift of the North Bay outlet between 10,000 and 5,000 years BP raised lake level to above the present (the Nipissing transgression), submerging the forest and valley system. Submerged stumps from those forests have often been encountered on the present lake floor; some stumps have been dated. Four sites in Ontario (Parkhill, Owen Sound, St. Joseph Island, Meaford) provide on-land evidence of pre-Nipissing drainage and valley formation. Radiocarbon ages of valley fill organic materials range from 7,310 to 5,410 years BP. At three sites, present drainage is known to be displaced from the pre-Nipissing drainage. Geophysical methods (EM, GPR, resistivity) have been used to refine valley location and morphology at Parkhill and Meaford. There is the potential of tracing the valleys down slope to the low-water shorelines with shipboard geophysics, with implications for archaeology, hydrology and hydrogeology, paleogeography, and Great Lakes history. This is the eighth in a series of ten papers published in this special issue of Journal of Paleolimnology. These papers were presented at the 47th Annual Meeting of the International Association for Great Lakes Research (2004), held at the University of Waterloo, Waterloo, Ontario, Canada. P.F. Karrow and C.F.M. Lewis were guest editors of this special issue.     

Environmental changes documented by sedimentation of Lake Yiema in arid China since the late Glaciation

In this study, a 6 m long core (16,000 BP) at the center of the dry Lake Yiema, a closed lake of Shiyang River drainage in Minqin Basin of the arid northwestern China, was retrieved to recover the history of climate changes and lake evolution in the area. Five radiocarbon dates on organic matter were obtained. A chronological sequence is established based on these five dates and other dates from nearby sites. Magnetic susceptibility, particle size and chemical composition were analysized for climate proxies. The proxies indicate that a drier climate prevailed in the Shiyang River drainage during the last glacial. Lake Yiema was dry and eolian sand covered most part of the lake basin. During the early and middle Holocene, a moister climate prevailed in the drainage. Climate became dry stepwise with an abrupt transition from one stage to another during the entire Holocene and became driest since about 4,200 BP. Maximum dry climate spells occurred at about 12,000-10,000 BP and after about 4,200 BP. A dry climate event also existed at about 7,600 BP. Periodical sand storms with about 400-yr cycle happened during the middle Holocene. Desiccation processes of the lake started at 4,200 BP, and were accelerated since the last 2,500 yrs by the inflow water diversion for agriculture irrigation. During the past 2,500 yrs, the lake size has been closed associated with the human population, implying that the human impact has been accelerating the lake desiccation superimposed on the natural climate deterioration.     

A preliminary investigation of siliceous microfossil succession in late Quaternary sediments from Lake Baikal, Siberia

Siliceous microfossil assemblage succession was analyzed in a 100 m sediment core from Lake Baikal, Siberia. The core was recovered from the lake's central basin at a water depth of 365 m. Microfossil abundance varied greatly within the intervals sampled, ranging from samples devoid of siliceous microfossils to samples with up to 3.49 × 10¹¹ microfossils g^-1 sediment. Fluctuations in abundance appear to reflect trends in the marine ¹⁸O record, with peak microfossil levels generally representing climate optima. Microfossil taxa present in sampled intervals changed considerably with core depth. Within each sample a small number of endemic diatom species dominated the assemblage. Changes in dominant endemic taxa between sampled intervals ranged from extirpation of some taxa, to shifts in quantitative abundance. Differences in microfossil composition and the association of variations in abundance with climate fluctuations suggest rapid speciation in response to major climatic excursions.     

A late Pleistocene and Holocene mineral magnetic record from sediments of Lake Aibi,Dzungarian Basin,NW China

We studied mineral magnetic properties of a 6-m-long, late Pleistocene through Holocene sediment sequence from Lake Aibi in Dzungaria (Zunggary, Junggar), northern Xinjiang, China. Results were used to infer environmental changes and are compared with previously studied cores from Lake Manas. Both water bodies occupy the deepest parts of the Dzungarian Basin and are remnants of large Holocene lakes. During the Late Pleistocene, the magnetic mineralogy in both lakes was dominated by detrital, iron oxide minerals. Oxic conditions, which dominated during sedimentation and early diagenesis, persisted over the Pleistocene–Holocene transition. Later, during the middle Holocene, lake bottom conditions enabled authigenic formation of iron sulphide minerals such as pyrite (FeS₂) in Lake Aibi, and pyrite and greigite (Fe₃S₄) in Lake Manas. This iron sulphide mineralogy suggests increased biological activity in stagnant, anoxic bottom waters. Anoxic bottom conditions started about 9.8 cal kyr BP in Lake Manas and at about 7.2 cal kyr BP in Lake Aibi. A short dry event recorded in Lake Manas between 6.8 and 5.2 cal kyr BP is not clearly observed in Lake Aibi. In the late Holocene, i.e. the last 2.8 cal kyr, sediments of both lakes are again characterised by iron oxides, suggesting well-mixed, shallow water bodies. For this recent period, it seems that the detrital material in the two lakes had a common origin. Magnetic properties of sediments in Lakes Aibi and Manas show broadly similar environmental evolution during the late Pleistocene and Holocene. Nevertheless, despite the close proximity of the two lakes (~200 km) in the same basin, they display some different magnetic properties and record environmental changes at different times.     

Holocene millennial-scale climate variations documented by multiple lake-level proxies in sediment cores from Hurleg Lake,Northwest China

Millennial-scale climate variability has not been well documented in arid northwest China due to the scarcity of high-resolution, well-dated paleoclimate records. Here we present multi-proxy records from sediment cores taken in freshwater Hurleg Lake on the northeastern Tibetan Plateau, which reveal millennial-scale lake-level and climate variations over the past 8,000 years. This high-elevation region is very sensitive to large-scale climate change, thus allowing us to better understand Holocene climate variations in East Asia. The lake-level record, derived from lithology, magnetic mineralogy, carbonate isotopes, ostracode shell isotopes and trace elements, X-ray fluorescence (XRF), and gray scale data, indicates a highly variable and generally dry climate from 7.8 to 1 ka (1 ka = 1,000 cal year BP), and a relatively stable and wet climate after 1 ka. Superimposed on this general trend, six dry intervals at 7.6–7.2 ka, 6.2–5.9 ka, 5.3–4.9 ka, 4.4–3.8 ka, 2.7–2.4 ka, and 1.7–1.1 ka were detected from the high-resolution carbonate content and XRF data. The generally dry climate between 7.8 and 1 ka was almost synchronous with the decrease of East Asian and Indian monsoon intensities shortly after 8 ka. The six dry intervals can be correlated with weak monsoon events recorded in the East Asia and Indian monsoon regions, as well as the North Atlantic cold events. Our data suggest that millennial-scale monsoon variations could cause highly variable climate conditions in arid northwest China during the Holocene. These millennial-scale climate variations may reflect changes in solar variation and/or changes in oceanic and atmospheric circulation.     

Mineral magnetic and physical properties of surficial sediments and onshore samples from the southern basin of Lake Baikal, Siberia

Results of lithostratigraphic and mineral magnetic analysis of two surficial sediment cores (21 cm and 45 cm in length) collected from the Southern basin of Lake Baikal at a water depth of 1390 m, are presented. The sediments have been measured for a wide range of mineral magnetic parameters in order to assess their value in the identification of turbidite layers. Particle size and geochemical data are also presented and these explain some of the down core variations in magnetic mineralogy. It is suggested that changes in the particle size frequency distributions down core may be related to fossil diatom shells. One of the cores has been dated using ²¹⁰Pb. The sediment cores were cross-correlated using low frequency magnetic susceptibility (f) and these cores can also be correlated with a nearby core collected earlier in 1992. Changes in the magnetic parameters of lf, IRMs and HIRM₂₁₀ suggest that there are significant changes in the concentration of ferrimagnetic minerals in the sediment cores, indicating changing sediment sources and/or increasing concentrations of spheroidal carbonaceous particles and the dissolution of minerals through reduction below the oxidised layer within the sediment core.     

A model for the demise of large, glacial Lake Ojibway, Ontario and Quebec

Large glacial lakes modulated the return of meltwater to the ocean during deglaciation, and their drainage may have initiated global climate change. Yet few records of their drainage come from observations within their basins. Sediment cores from nine lakes along a 240-km transect from northwestern Quebec to northeastern Ontario cover a portion of former Lake Ojibway and provide a stratigraphy of the terminal phase of this large glacial lake. Magnetic susceptibility, density, grain size, X-ray fluorescence chemistry and X-ray diffraction data were used to characterize stratigraphic changes within the basin. The basal sequence consists of till and rhythmites, with ice-proximal debris flows overlain by varves. The varves thin up-section and become unrecognizable, which indicates decreased deposition rates. This fine-grained sediment forms the matrix of a clay-pebble conglomerate. The clay-pebbles are ice-rafted debris (IRD). The IRD flux was probably constant, whereas the sedimentation rate of the finer-grained matrix decreased. The end of IRD marks the cessation of icebergs in the lake and is the best indication for drainage of the glacial lake. The conglomerate is capped by laminated to massive gray silt deposited after lake drainage and marks the transition to organic-rich, post-glacial lakes. Such sequences place drainage into the broader context of deglaciation.     

Anthropogenic impacts recorded in recent sediments from Otisco Lake,New York,USA

Geochemical analysis of ²¹⁰Pb-dated sediment cores from Otisco Lake (New York) combined with analysis of recent land cover change in the watershed revealed the history of land use change, lake management, and industrial pollution since European settlement in the northeastern US. Clearance of forestland for agriculture characterized the early settlement era that was marked in the Otisco Lake sediments by a decline in organic carbon (OC) and OC:N ratios, which indicate a change in the sources of organic matter to the lake. Agricultural land use reached its greatest areal extent in the Otisco watershed around 1900, followed by field abandonment and reforestation over the last century. In the 1920s sediment accumulation rates began to increase coincident with residential development along the lake shore. Nitrogen and organic carbon, which are transported from the watershed, show increased fluxes to the lake in response to this change. Deposition of inorganic carbon increased markedly over a short period from the 1940s to the 1980s, which is consistent with enhanced mobilization of watershed calcium by increased acidic deposition, followed by alkalinization of the lake waters and calcite precipitation. An increase in copper content in the sediments reflects application, since 1942, of the algicide copper sulfate to the lake waters to control algal blooms. This CuSO₄ marker confirmed the accuracy of the ²¹⁰Pb chronology. Atmospheric mercury (Hg) fluxes to the lake were affected by increased sediment transport from the watershed. The maximum Hg peak in the sediment record, however, was dated to the early 1970s and coincides with maximum Hg emissions to the atmosphere in the Great Lakes region.     

Potential salinity limitations on nitrogen fixation in sediments from Mono Lake, California

Mono Lake is a hypersaline alkaline lake in the high altitude Great Basin desert of eastern California. Algal productivity of the lake is nitrogen-limited, and a contributing source is derived from benthic nitrogen fixation. Lake level and salinity have fluctuated with natural climatic variations but have also been affected by the diversion of tributary streams. This research examines the influence of varied salinity and lake level on the potential for benthic nitrogen fixation in Mono Lake. A sediment-surface microbial mat community was exposed directly, and in acclimated cultures, to a range of Mono Lake salinities under anaerobic incubations and the activity of nitrogenase assayed by acetylene reduction. Activity was stimulated in light, but also occurred in darkness. Over an experimental salinity range from 50 to 150 g L⁻¹ TDS, nitrogenase activity was reduced by 90 per cent, with the activity persisting at the highest salinity being attributable to dark fixation alone. Between a salinity of 50 g L⁻¹, occurring in Mono Lake over 50 years ago, and 100 g L⁻¹, nitrogenase activity was reduced by nearly half. Changes in the area of the littoral zone at varied lake levels also affect the total amount of potential benthic nitrogen fixation in the lake. An accounting of yearly inputs of nitrogen to Mono Lake suggests N₂-fixation could contribute as much as 76–81 percent of the total. Inhibition of nitrogen fixation rates by increased salinity could limit the long-term nutrient supply and benthic primary productivity of this ecosystem.     

近现代高邮湖沉积记录的环境变化

1 Introduction Gaoyou Lake is the third largest lake in Jiangsu Province. It lies in central Jiangsu Province, lower reaches of the Huaihe River, and west of the Jing–Hang (Beijing–Hangzhou) Grand Canal. Previous research on environmental changes of the…     

Environmental changes during modern period from the record of Gaoyou Lake sediments,Jiangsu

Based on analysis of parameters of cores taken from Gaoyou Lake, including magnetic susceptibility, grain-size characteristics and sedimentary rate, environmental changes during the modern period were examined with the assistance of historical records and Gaoyou Lake water level materials. It is concluded that during the modern period a higher value of magnetic susceptibility and a lower sediment grain size coincided with a wet climate, while a lower value of magnetic susceptibility and a higher grain size were related with a dry climate. The results indicate that the climate in the 123 years period from 1880 to 2003AD can be divided into four stages： two low water level stages （1880-1915AD, 1948-1981AD） and two high water level stages （1915-1948AD, 1981-2003AD）. It appears that the regional climate generally underwent a dry-wet-dry-wet pattern in 30-year cycles. At present, it is at the end of a wet period, so the regional climate is expected to become dry in the near future. This conclusion corresponds with the climate records in the historical literature of the Gaoyou area, and it also matches with the climatic changes in North Jiangsu area.     

Environmental changes during modern period from the record of Gaoyou Lake sediments, Jiangsu

Based on analysis of parameters of cores taken from Gaoyou Lake, including magnetic susceptibility, grain-size characteristics and sedimentary rate, environmental changes during the modern period were examined with the assistance of historical records and Gaoyou Lake water level materials. It is concluded that during the modern period a higher value of magnetic susceptibility and a lower sediment grain size coincided with a wet climate, while a lower value of magnetic susceptibility and a higher grain size were related with a dry climate. The results indicate that the climate in the 123 years period from 1880 to 2003AD can be divided into four stages: two low water level stages (1880–1915AD, 1948–1981AD) and two high water level stages (1915–1948AD, 1981–2003AD). It appears that the regional cli-mate generally underwent a dry–wet–dry–wet pattern in 30-year cycles. At present, it is at the end of a wet period, so the regional climate is expected to become dry in the near future. This conclusion corresponds with the climate records in the historical literature of the Gaoyou area, and it also matches with the climatic changes in North Jiangsu area.     

A late Cenozoic Earth's crust and climate dynamics record from Lake Baikal

The sedimentary record from Lake Baikal (Siberia, Russia) has been an important source of information about paleoclimatic variability in the northern hemisphere and dynamics of continental rift development. A lack of reliable chronology has, however, been a major obstacle to fully utilizing the Baikal archive for time scales beyond about 4-5 Myr. In this paper we use the distribution of ¹⁰Be to establish a new chronology for the longest core drilled in Lake Baikal so far. The ¹⁰Be-based chronology spans the last 8 Myr and provides better constraints on sedimentation rates and consequently on an east-west tectonic extension in the lake, which has been apparently coeval with other rifts in Asia that are related to the Tibetan plateau uplift. Our data also show higher ¹⁰Be flux in the sediment section older then 5 Myr compared with the younger period. This can be explained partly by warm and humid climatic conditions of the Miocene and partly by a high cosmic ray flux to the Earth resulting from possible low geomagnetic field intensity during that time.     

Post-Chippewa oxygen isotope record from Cowles Bog, southern Lake Michigan basin

Previous studies of sediments and molluscs recovered from vibracores at Cowles Bog, a fen located in the Indiana Dunes National Lakeshore, along the south shore of Lake Michigan, reveal long and short term water level fluctuations during the last 6000 years. Low water events are indicated by zones of organic detritus, in which occasionally, iron oxide and calcium carbonate nodules, as well as selenite crystals have been precipitated. Oxygen isotope data from aragonitic shells of the gastropod Amnicola limosa (Say) collected from a sediment core provide a record of Middle to Late Holocene environmental changes for the fen. These data are in good agreement with previous interpretations of water level fluctuations based on changes in lithology and molluscan faunal abundance and composition. Below 366 cm the molluscan record is either absent or represented by shell fragments. The condition of shells in this interval suggests that the molluscs may have been exposed to subaerial weathering and reworking of older Holocene lake sediments, possibly during the low water Chippewa phase in the Lake Michigan basin (10000 YBP to 6000 YBP). Above 366 cm the core is characterized by a well preserved molluscan fauna. Relatively light isotopic values for the interval between 366 cm to 300 cm correlate with the transition from non-fossiliferous sands, peat and diamict to silty marl and calcareous sand, with a molluscan fauna dominated by taxa associated with permanent water bodies. The event producing these alterations, the Nipissing Transgression, marks a change from subaerial to permanent lacustrine conditions that were not characterized by high net evaporation. Evidence for another series of environmental changes occurs between 284 cm and 198 cm. This evidence includes the: (1) appearance of aquatic molluscs at 280 cm that are associated with water bodies subject to significant seasonal water level changes; (2) intermittent accumulations of iron oxide nodules, calcium carbonate nodules, and organic layers interbedded with crudely horizontal layers of fine, calcareous, sand, suggesting periodic water level oscillations; (3) onset of major excursions in the oxygen isotopic values between 260 cm to 198 cm. Relatively high ¹⁸O (PDB) values, possibly indicating evaporative enrichment of the water, correlate with a prominent shell debris layer at a depth of about 235 cm. Taken together, this evidence suggests that the core site was in the process of becoming isolated from Lake Michigan. This isolation occurred during a series of low water events during the later part of the Nipissing Transgression.     

A late Holocene pollen record of deforestation and environmental change from the Lake Tauanui catchment, Northland, New Zealand

Late Holocene pollen and sediment records from the Lake Tauanui catchment, northern New Zealand, indicate that the lake formed about 5500 years ago following a series of volcanic events in the Tauanui Volcanic Centre. These volcanic events initiated a volcanosere resulting in a mixed conifer-hardwood forest. Dacrydium cupressinum was the dominant tree. Agathis australis was always present. Changes similar to those registered in other Northland pollen diagrams are apparent. At ca 4000 yr B.P., when the climate became cooler and drier than before, a fire occurred in the catchment area causing erosion of the surrounding slopes and some destruction of forest. Fluctuations in abundance of many forest species, including Ascarina lucida, A. australis and D. cupressinum, from ca 3500 yr B.P. indicate repeated disturbance, increasingly so after 1600 yr B.P. Summer droughts and increased frequency of cyclonic winds are suggested as the cause. Major anthropogenic deforestation events defined by palynology occurred across many parts of the New Zealand landscape at ca 700 yr B.P. At Lake Tauanui anthropogenic forest disturbance, radiocarbon dated to ca 1000 yr B.P., is indicated by significant decline in all tree and shrub elements with concomitant increase in pteridophytes, especially Pteridium esculentum. Charcoal concentration increases steadily from the onset of disturbance, and in the final phase after the arrival of Europeans, major clearance of vegetation is indicated. Herbs increase markedly in this period, in diversity and abundance.     

Bryozoan statoblasts in the recent sediments of Douglas Lake, Michigan

Statoblast valves produced by the freshwater bryozoan Plumatella nitens were recovered in three sediment cores from Douglas Lake, Michigan. Douglas Lake is a multi-depression lake of glacial origin. The region was heavily logged from 1880 to 1920. Sediment cores were taken from three of the seven depressions, and dated using 210Pb isotopes and pollen. Sedimentation rates were very low in the Grapevine Point core as compared to the other two cores. Concentrations of statoblasts ranged from three to 140 ml-1 of wet sediment. Profiles of statoblast concentrations and accumulation rates indicate a sharp decline in Plumatella populations corresponding to the time the Douglas Lake watershed was being clear-cut. It appears that logging and the resulting increase in erosion had adverse effects on bryozoan populations, and possibly on the entire littoral zone of the lake. High sediment loads to the lake could have caused mortality in Plumatella by interfering with the feeding of these animals, or by decreasing numbers of macrophytes which are frequently used as substrate. Populations of Plumatella have not recovered to pre-disturbance levels.     

青藏高原腹地湖泊沉积对第四纪晚期古季风变化的响应

通过对青藏高原腹地的综合科学考察和对中心钻孔岩芯剖面的最新研究,用层序地层学与年代地层学和气候地层学相结合的方法,分辨出可可西里地区湖泊沉积记录(孔深7.25 m)的第四纪晚期距今3万余年以来的古气候变化,沉积物磁化率等因子综合表征的高原古季风变化是波动发展的,发生在仙女木期地质环境事件中的季风活动具有强烈暴发的特点,是高原季风发展中的突变事件,而且地表热点效应对其起到了激发作用。综合分析的研究成果表明,它的变化频谱与激变因子及其运行机制是伴随着青藏高原地质效应的演变而发展的,为研究第四纪冰消期以来的气候变化提供了新的信息。     

Multiple ecological and hydrological changes recorded in varved sediments from Sanagak Lake,Nunavut, Canada

A combination of biotic, sedimentary and biogeochemical proxies was used to investigate the timing and causes of post-18th century changes in the stratigraphic record of a large, deep lake on the Boothia Peninsula, Nunavut, Canada (70°15′ N, 94°30′ W). A varve chronology verified with radioisotopic dating (²¹⁰Pb and ¹³⁷Cs) revealed a complex pattern of environmental dynamics since c. AD 1830. An increase in the diatoms Asterionella formosa, Stephanodiscus minutulus and Cyclotella atomus and a decrease in Aulacoseira taxa in the uppermost centimetre of sediment suggested that environmental conditions have favoured the growth of smaller and/or lighter planktonic species since the 1980s. Longer term changes in some benthic species, the chrysophyte cysts to diatom valve ratio, %C, and C/N ratios suggest declined river inflow and a relative reduction in allochthonous inputs during the last century. Higher than average δ¹⁵N values in the late 19th to early 20th centuries coincide with changes in bulk carbon and nitrogen profiles, and below average values since approximately 1950 may be associated with increased atmospheric N loading or reduced productivity. Biogenic silica and organic carbon accumulation in the sediments suggest a possible decline in lake production during the 20th century that may be associated with changes in the river discharge regime. The short and long-term ecological and biogeochemical trends were also reflected in the sedimentary structure through declining varve thickness for the duration of the record and an abrupt change in sedimentology in the uppermost 1 cm, coinciding with deposition since ca. AD 1987. Together, these biological and physical changes suggest changes in hydroclimatic conditions in the 20th century, and an increase in planktonic diatom taxa since the 1980s that coincides with a distinct period of climate warming.     

The climatic signal in varved sediments from Lake C2, northern Ellesmere Island, Canada

Annually-laminated clastic sediments preserve a high resolution proxy record of paleoclimate, provided that allochthonous sedimentation represents a response to meteorological forcing of watershed sediment transfer. Here, we demonstrate this linkage, and illustrate a calibration process using the most recent 40 years of a varve record from Lake C2 (82°50 N; 78°00 W), three years of field measurements, and meteorological data for 1951–92 from nearby AES weather station Alert. Field measurements were used to correlate proxies of the energy available for snowmelt (e.g. air temperature) and daily suspended sediment discharge (SSQ). Our calibration was extended through use of weather data from Alert. Both mean daily air temperature at Echo, and daily SSQ, were well correlated with air temperature at 600 m above Alert, as obtained from the 1200 Z (0800 LST) rawinsonde sounding. Accordingly, we used pooled 1990 and 1992 Alert 600 m data to predict the lagged daily sediment discharge into Lake C2 (adj. r ²=0.43). Daily values were summed each year in order to produce an annual series of predicted sediment transfer to the lake. The original varve chronology was based on eight sediment cores recovered from the deep basin of the lake (>80 m). Although low-frequency fluctuations of the varve and predicted SSQ series agree, slight tuning of the varve record optimizes the correlation between them. Adjustments were based on examination of weather data for specific years, reexamination of sediment core thin sections, and by aligning fluctuations in the two series which closely matched. Although the original chronology is reasonably well correlated with 600 m temperatures at Alert (for JJA mean, r=0.41, significant at 0.01), the adjusted chronology is both better correlated and contains a more precise climate signal (r=0.54 for July mean, significant at 0.01). This is the first calibrated varve record produced from Arctic lake sediments, and demonstrates that varves from Lake C2 contain a paleoclimatic record. We believe the post-facto manipulations required to produce the adjusted varve chronology are reasonable given the uncertainties inherent in varve counting, and the lack of any independent corroborating chronostratigraphic markers.This is the ninth in a series of papers published in this issue on the Taconite Inlet Lakes Project. These papers were collected by Dr R. S. Bradley.