A 150 kyr-long hydroclimate record from Southern California using Searles Lake sediments: initial findings

NASA Astrophysics Data System (ADS)

Stroup, J. S.; Olson, K. J.; McGee, D.; Lowenstein, T. K.; Smoot, J. P.; Janick, J. J.; Lund, S.; Peaple, M.; Chen, C. Y.; Feakins, S. J.; Litwin, R.

2017-12-01

Over decadal to millennial scales, the southwestern U.S has experienced large shifts in hydroclimate ranging from pluvial conditions to extreme droughts. Direct observations, modeling and proxy data suggest precipitation amount and distribution are controlled by multiple factors including the position of the Hadley Cell, strength of the Aleutian Low and North Pacific High, ENSO and the path of winter storm tracks. Sediment records from closed basin lakes provide a means for assessing how hydrologic conditions have responded to past climate changes; however, long (>50 ka) paleoclimate records from lakes are rare and high-resolution age models are challenging to obtain. Searles Lake, in southeastern California, contains a sedimentary record that spans from the Holocene to the Pliocene at high resolution. Previous drill core studies from the basin used stratigraphy and sediment mineralogy to interpret paleoenvironmental changes and have demonstrated that the lake's sediments are able to be precisely dated. These results provide a strong foundation for new high-resolution investigations of the lake sediments. In January 2017, our group collected a new 80 m-long core with the aim of reconstructing hydrologic changes over the last 150 ka at millennial or better resolution. The core was split at the National Lacustrine Core Facility (LacCore) in June. The core contains alternating evaporite layers and finely laminated muds which likely indicate times of dryer and wetter conditions. Despite the challenge of alternating lithologies, core recovery and quality are extremely high. Here, we will present our initial chronological and stratigraphic findings. The core record will be dated using a combination of U/Th, 14C and magnetostratigraphy. We will compare our initial stratigraphic description to the existing Searles Lake literature as well as other records from the region, such as data from Devils Hole. These results provide the framework upon which we will develop detailed

A new varved late Glacial and Holocene sediment record from Lake Jelonek (North Poland) - preliminary results

NASA Astrophysics Data System (ADS)

Kramkowski, Mateusz; Filbrandt-Czaja, Anna; Ott, Florian; Słowiński, Michał; Tjallingii, Rik; Błaszkiewicz, Mirosław; Brauer, Achim

2015-04-01

Anually laminated (varved) lake deposits are suitable natural archives for reconstructing past climatic and environmental changes at seasonal resolution. A major advantage of such records is that varve counting allows constructing robust and independent chronologies, a key challenge for paleoclimate research. Recently, a new annually laminated sediment record has been obtained from Lake Jelonek, located in the eastern part of the Pomeranian Lakeland in northern Poland (Tuchola Pinewoods). The lake is surrounded by forest and covers an area of 19,9 ha and has a maximum depth of 13,8 m. Three overlapping series of 14,3 m - long sediment records have been cored with an UWITEC 90 mm diameter piston corer from the deepest part of the lake. A continuous master composite profile has been established comprising the entire postglacial lacustrine sediment infill. Preliminary analyses including micro-facies analyses on thin sections from selected intervals as well as X-ray fluorescence element scanning (µ-XRF) reveal that the sediments are to a large part annually laminated. Here we present detailed varve models for different sediment intervals and discuss high-resolution geochemical variation in the entire sediment record. A preliminary age model based on radiocarbon dating and major biostratigraphical boundaries based on pollen data will be presented as well. These data will form the fundament for the planned multi-proxy study for detailed reconstructions of climatic and environmental variability during the late glacial and Holocene in the southern Baltic. This study is a contribution to the Virtual Institute ICLEA (Integrated Climate and Landscape Evolution Analysis) funded by the Helmholtz Association and National Science Centre Poland NCN 2011/01/B/ST10/07367.

Pre-aged plant waxes in tropical lake sediments and their influence on the chronology of molecular paleoclimate proxy records

NASA Astrophysics Data System (ADS)

Douglas, Peter M. J.; Pagani, Mark; Eglinton, Timothy I.; Brenner, Mark; Hodell, David A.; Curtis, Jason H.; Ma, Keith F.; Breckenridge, Andy

2014-09-01

Sedimentary records of plant-wax hydrogen (δDwax) and carbon (δ13Cwax) stable isotopes are increasingly applied to infer past climate change. Compound-specific radiocarbon analyses, however, indicate that long time lags can occur between the synthesis of plant waxes and their subsequent deposition in marginal marine sediments. The influence of these time lags on interpretations of plant-wax stable isotope records is presently unconstrained, and it is unclear whether such time lags also affect lacustrine sediments. We present compound-specific radiocarbon (14Cwax) data for n-alkanoic acid plant waxes (n-C26 to n-C32) from: (1) a sediment core from Lake Chichancanab, Yucatan Peninsula, Mexico, (2) soils in the Lake Chichancanab catchment, and (3) surface sediments from three other lakes in southeastern Mexico and northern Guatemala. 14Cwax ages in the surface sediments are consistently older than modern, and may be negatively correlated with mean annual precipitation and positively correlated with lake catchment area. 14Cwax ages in soils surrounding Lake Chichancanab increase with soil depth, consistent with deep, subsoil horizons being the primary source of lacustrine aged plant waxes, which are likely delivered to lake sediments through subsurface transport. Plant waxes in the Lake Chichancanab core are 350-1200 years older than corresponding ages of bulk sediment deposition, determined by 14C dates on terrestrial plant macrofossils in the core. A δDwax time series is in closer agreement with other regional proxy hydroclimate records when a plant-wax 14C age model is applied, as opposed to the macrofossil-based core chronology. Inverse modeling of plant-wax age distribution parameters suggests that plant waxes in the Lake Chichancanab sediment core derive predominantly from millennial-age soil carbon pools that exhibit relatively little age variance (<200 years). Our findings demonstrate that high-temporal-resolution climate records inferred from stable isotope

The preglacial sediment record of Lake Ladoga, Russia - first results from a seismic survey and sediment coring in 2013

NASA Astrophysics Data System (ADS)

Melles, Martin; Krastel, Sebastian; Fedorov, Grigory; Subetto, Dmitry A.; Savelieva, Larisa A.; Andreev, Andrej; Wagner, Bernd

2014-05-01

The new German-Russian project PLOT (Paleolimnological Transect) aims at investigating the Late Quaternary climatic and environmental history along a more than 6000 km long longitudinal transect crossing northern Eurasia. Special emphasis is put on the preglacial history. For this purpose shallow and deep seismic surveys shall be carried out on five lakes, which potentially host preglacial sediment records, followed by sediment coring based on the results of the seismic campaigns. The well-studied Lake El'gygytgyn represents the eastern-most location of the transect and acts as reference site. Within the scope of a pilot phase for the PLOT project, funded by the German Federal Ministry of Education and Research, we were able to investigate Lake Ladoga, which is located close to St. Petersburg at the western end of the transect. Lake Ladoga is the largest lake in Europe, covering an area of almost 18.000 km2. The modern sedimentation as well as the late glacial and Holocene history of the lake were already studied in detail over the past decades. The older, preglacial lake history, however, is only rudimentary known from a core transect drilled in the southern lake in the 1930th. The cores of up to about 60 m length were only briefly described and are not existing any more. The results from these cores, known from unpublished reports only, suggest the existence of marine sediments of presumably Eemian age, representing a time when Lake Lagoga was part of a precursor of the Baltic Sea, which had a connection via Ladoga and Onega Lakes to the White Sea and further to the Arctic Ocean. In late August/early September 2013 we carried out a seismic survey on Lake Ladoga using a Mini-GI-Gun and a 32-channel seismic streamer. In total, 1500 km of seismic profiles were measured, covering most parts of the lake. The seismic lines typically show acoustically well stratified Holocene muds overlaying rather transparent postglacial varves. These sediment successions can reach

Lake sediment records on climate change and human activities in the Xingyun Lake catchment, SW China.

PubMed

Zhang, Wenxiang; Ming, Qingzhong; Shi, Zhengtao; Chen, Guangjie; Niu, Jie; Lei, Guoliang; Chang, Fengqin; Zhang, Hucai

2014-01-01

Sediments from Xinyun Lake in central Yunnan, southwest China, provide a record of environmental history since the Holocene. With the application of multi-proxy indicators (total organic carbon (TOC), total nitrogen (TN), δ13C and δ15N isotopes, C/N ratio, grain size, magnetic susceptibility (MS) and CaCO3 content), as well as accelerator mass spectrometry (AMS) 14C datings, four major climatic stages during the Holocene have been identified in Xingyun's catchment. A marked increase in lacustrine palaeoproductivity occurred from 11.06 to 9.98 cal. ka BP, which likely resulted from an enhanced Asian southwest monsoon and warm-humid climate. Between 9.98 and 5.93 cal. ka BP, a gradually increased lake level might have reached the optimum water depth, causing a marked decline in coverage by aquatic plants and lake productivity of the lake. This was caused by strong Asian southwest monsoon, and coincided with the global Holocene Optimum. During the period of 5.60-1.35 cal. ka BP, it resulted in a warm and dry climate at this stage, which is comparable to the aridification of India during the mid- and late Holocene. The intensifying human activity and land-use in the lake catchment since the early Tang Dynasty (∼1.35 cal. ka BP) were associated with the ancient Dian culture within Xingyun's catchment. The extensive deforestation and development of agriculture in the lake catchment caused heavy soil loss. Our study clearly shows that long-term human activities and land-use change have strongly impacted the evolution of the lake environment and therefore modulated the sediment records of the regional climate in central Yunnan for more than one thousand years.

Initial Geochemistry Data of the Lake Ohrid (Macedonia, Albania) DEEP -Site Sediment Record: The ICDP Scopsco Drilling Project

NASA Astrophysics Data System (ADS)

Francke, A.; Wagner, B.; Sulpizio, R.; Zanchetta, G.; Leicher, N.; Gromig, R.; Krastel, S.; Lindhorst, K.; Wilke, T.

2014-12-01

Ancient lakes, with sediment records spanning >1 million years, are very rare. The UNESCO World Heritage site of Lake Ohrid on the Balkans is thought to be the oldest lake in Europe. With 212 endemic species described to date, it is also a hotspot of evolution. In order to unravel the geological and evolutionary history of the lake, an international group of scientists, conducted a deep drilling campaign in spring 2013 under the umbrella of the ICDP SCOPSCO project (Scientific Collaboration on Past Speciation Conditions in Lake Ohrid). Overall, about 2,100 m of sediments were recovered from four drill sites. At the main drill site (DEEP-site) in central parts of the lake where seismic data indicated a maximum sediment fill of ca. 700 m, a total of more than 1,500 m of sediments were recovered until a penetration depth of 569 m. Currently, core opening, core description, XRF and MSCL scanning, sub-sampling (16 cm resolution), and inorganic and organic geochemical as well as sedimentological analyses of the sediment cores from the DEEP site are in progress at the University of Cologne. Previous studies at Lake Ohrid have shown that interglacial periods are characterized by high TIC and TOC contents, likely associated with high contents of calcite and organic matter in the sediments. In contrast, during glacial periods negligible TIC and low TOC contents correspond to high K counts indicating enhanced supply of clastic material. Similar patterns can be observed in the biogeochemical analyses of the subsamples and in the XRF data of the DEEP site record. Following these variations on a glacial-interglacial time scale, TIC and TOC data obtained from the subsamples and from core catcher samples indicate that the DEEP site sequence provides a 1.2 million year old continuous record of environmental and climatological variability in the Balkan Region. The age control can be further improved by first findings of macroscopic tephra horizons. Peaks in K, Sr, Zr, and magnetic

Seasonal climate variability in historical and prehistorical times deduced from varved lake sediments: Calibration of records from Lakes Woseriner See and Tiefer See

NASA Astrophysics Data System (ADS)

Czymzik, Markus; Kienel, Ulrike; Dreibrodt, Stefan; Brauer, Achim

2013-04-01

Societies are susceptible to the effects of even short-term climate variations on water supply, health, and agricultural productivity. However, understanding of human-climate interactions is limited due to the lack of high-resolution climate records in space and time. Varved lake sediments provide long time-series of seasonal climate variability directly from populated areas that can be compared to historical and archeological records. Calibration against meteorological data enables process-based insights into sediment deposition within the lake that can be extrapolated into the past using transfer functions. Lakes Woseriner See (53°40'N/12°2'E; 37 m asl.) and Tiefer See (53°23'N/13°97'E, 65 m asl.) in northeastern Germany are located only 35 km apart. Situated within the former settlement areas, the lakes are well suited for studying climate influences on society related to the Neolithic Funnelbeaker culture or the Slavic colonization. Sub-recent annual laminations allow to establish climate proxy data-series at seasonal resolution that can be calibrated against the long meteorological record from the nearby City of Schwerin. Seasonal climate proxy data-series covering the last 90 years have been obtained from short sediment cores applying a combination of microfacies analyses, X-ray fluorescence scanning (µ-XRF), and varve counting. Main sediment microfacies in both lakes are endogenic calcite varves comprising calcite and organic layer couplets of varying thickness, diatom layers, and dispersed detrital grains. Calibration against meteorological data indicates that variations in sediment layer thickness and composition are not stationary through time but influenced by inter-annual variations in meteorological conditions.

Non-Linear Response to Holocene Insolation Forcing Recorded by High-Resolution Lake Sediment Records Across Iceland

NASA Astrophysics Data System (ADS)

Geirsdottir, A.; Miller, G. H.; Axford, Y.

2009-12-01

Many Icelandic lakes have sedimentation rates in excess of 1 m ka-1 throughout the Holocene. Such high rates offer the potential for decadally resolved (or better) records of environmental change at this sensitive North Atlantic site. Abundant well-defined tephra provide a secure geochronology. The fidelity of the common climate proxies biogenic silica (BSi) and total organic carbon (TOC), was tested by comparing these proxies in three lakes with very different catchment characteristics. Hestvatn (HST, 60 m deep) in southern Iceland receives overflow from a large river originating in the glaciated highlands of central Iceland, whereas the nearby lake Vestra Gislholtsvatn (VGHV, 15 m deep) has a small, low elevation catchment without glaciers. Haukadalsvatn (HAK, 42 m deep), in northwestern Iceland, has a large, high relief catchment. The BSi record from HAK has been shown to reflect April-May temperatures, with BSi highest when spring temperatures are at their maximum. The first- and second-order trends in BSi are similar in all three lakes for most of the Holocene. This supports the contention that BSi reflects primary productivity, and is less influenced by changes in sedimentation rate. In all three lakes, BSi reaches a maximum value shortly after 8 ka, and then declines gradually toward present, reflecting a relatively late Holocene thermal maximum, potentially due to the influence of meltwater from the lingering Laurentide Ice Sheet. A steady reduction in summer insolation determines this first-order trend towards lower BSi through the middle and late Holocene. Large, abrupt departures from the overall decrease in BSi characterize all three records after 8 ka. Following each rapid BSi decrease, BSi usually exhibits a step-function change, re-equilibrating at a lower BSi value. Some of the strongest departures (ca. 6 ka, 4 to 4.5 ka and ca. 3 ka) may be related to Icelandic volcanism, but the lack of a full recovery to pre-existing values after the eruptions

Lake Sediment Records as an Indicator of Holocene Fluctuations of Quelccaya Ice Cap, Peru and Regional Climate

NASA Astrophysics Data System (ADS)

Stroup, J. S.; Kelly, M. A.; Lowell, T. V.; Beal, S. A.; Smith, C. A.; Baranes, H. E.

2012-12-01

The past fluctuations of Quelccaya Ice Cap, (QIC; 13°S, 70°W, 5200 m asl) located in the southeastern Peruvian Andes, provide a record of tropical climate since the last glacial-interglacial transition. A detailed surficial geomorphic record of past glacial extents developed over the last several decades (e.g. Mercer and Palacios 1977; Buffen et al. 2009; Kelly et al. 2012 accepted) demonstrates that QIC is a dynamic glacial system. These records show that the ice cap was larger than present and retreating by ~11,500 yr BP, and smaller than present between ~7,000 and ~4,600 yr BP. The most recent advance occurred during the late Holocene (Little Ice Age;LIA), dated with 10Be surface exposure ages (510±90 yrs (n = 8)) (Stroup et al. in prep.). This overrode earlier deposits obscuring a complete Holocene record; we aim to address the gaps in glacial chronology using the sedimentary record archived in lakes. We retrieved two sets cores (8 and 5 m-long) from Laguna Challpacocha (13.91°S, 70.86°W, 5040 m asl), a lake that currently receives meltwater from QIC. Four radiocarbon ages from the cores suggest a continuous record dating to at least ~10,500 cal. yr BP. Variations in magnetic susceptibility, percent organic and inorganic carbon, bulk density, grayscale and X-ray fluorescence chemistry indicate changes in the amount of clastic sediment deposition. We interpret clastic sediments to have been deposited from ice cap meltwater, thus indicating more extensive ice. Clastic sediments compose the top of the core from 4 to 30 cm depth, below there is a sharp transition to organic sediments radiocarbon dated to (500±30 and 550±20 cal. yr BP). The radiocarbon ages are similar to the 10Be dated (LIA) glacial position. At least three other clastic units exist in the core; dating to ~2600-4300, ~4800-7300 and older then ~10,500 cal. yr BP based on a linear age model with four radiocarbon dates. We obtained two, ~4 m long, cores from Laguna Yanacocha (13.95°S,70.87�

A 2000-year palaeoflood record from northwest England from lake sediments

NASA Astrophysics Data System (ADS)

Schillereff, Daniel; Chiverrell, Richard; Macdonald, Neil; Hooke, Janet

2014-05-01

Greater insight into the relationship between climatic fluctuations and the frequency and magnitude of precipitation events over recent centuries is crucial in the context of future warming and projected intensification of hydrological extremes. However, the detection of trends in flood frequency and intensity is not a straightforward task as conventional flood series derived from instrumental sources rarely span sufficiently long timescales to capture the most extreme events. Usefully, the geomorphic effects of extreme hydrological events can be effectively recorded in upland lake basins as efficient sediment trapping preserves discharge-related proxy indicators (e.g., particle size). Provided distinct sedimentary signatures of historic floods are discernable and the sediment sequence can be well-constrained in time, these lacustrine archives offer a valuable data resource. We demonstrate that a series of sediment cores (3 - 5 m length) from Brotherswater, northwest England, contain numerous coarse-grained laminations, discerned by applying high-resolution (0.5 cm) laser granulometry, which are interpreted as reflecting a palaeoflood record extending to ~2000 yr BP. The presence of thick facies which exhibit inverse grading underlying normal grading, most likely reflecting the waxing and waning of flood-induced hyperpycnal flows, supports our palaeoflood interpretation. Data from an on-going sediment trapping protocol at Brotherswater that shows a relationship between river discharge (recorded via short-term lake level change representing flood events) and the calibre of particles captured in the traps lends further support to our interpretation. Well-constrained chronologies were constructed for the cores through integrating radionuclide (210Pb, 137Cs, 241Am, 14C) dating within a Bayesian age-depth modelling protocol. Geochemical markers of known-age that reflect phases of local point-source lead (Pb) mining were used to resolve time periods where radiocarbon

A late Holocene record of solar-forced atmospheric blocking variability over Northern Europe inferred from varved lake sediments of Lake Kuninkaisenlampi

NASA Astrophysics Data System (ADS)

Saarni, Saija; Muschitiello, Francesco; Weege, Stefanie; Brauer, Achim; Saarinen, Timo

2016-12-01

This study presents a new varved lake sediment sequence from Lake Kuninkaisenlampi, Eastern Finland. The record is constituted by alternations of clastic and biogenic laminae and provides a precise chronology extending back to 3607 ± 94 varve yrs. BP. The seasonality of the boreal climatic zone, with cold winters and mild summers, is reflected in the varve structure as a succession of three laminae from bottom to top, (i) a coarse to fine-grained detrital lamina marked by detrital catchment material transported by spring floods; (ii) a biogenic lamina with diatoms, plant and insect remnants reflecting biological productivity during the season of lake productivity; and (iii) a very fine amorphous organic lamina deposited during the winter stratification. The thickness of the detrital lamina in the lake reflects changes in the rate of spring snow melt in the catchment and is, therefore, considered a proxy for winter conditions. Hence, the record allows reconstructing local climate and environmental conditions on inter-annual to the multi-centennial timescales. We find that minerogenic accumulation reflected in the detrital lamina exhibits a high multi-decadal to centennial-scale spectral coherency with proxies for solar activity, such as Δ14C, and Total Solar Irradiance, suggesting a strong link between solar variability and sediment transport to the lake basin. Increased catchment erosion is observed during periods of low solar activity, which we ascribe to the development of more frequent atmospheric winter blocking circulation induced by solar-forced changes in the stratosphere. We suggest that soil frost in the catchment of Lake Kuninkaisenlampi related to more frequent winter blocking led to increased surface run-off and ultimately to increased catchment erosion during spring. We conclude that, during the past ca 3600 years, solar forcing may have modulated multi-decadal to centennial variations in sedimentation regimes in lakes from Eastern Finland and

Assessing the El Niño/Southern Oscillation proxy potential of the sediment record from Genovesa Crater Lake, Galápagos

NASA Astrophysics Data System (ADS)

Conroy, J.; Overpeck, J. T.; Cole, J. E.; Collins, A.; Bush, M. B.; Steinitz-Kannan, M.

2009-12-01

Paleoclimate records from the tropical Pacific Ocean suggest significant changes in sea surface temperature (SST) and El Niño/Southern Oscillation (ENSO) variability during the Holocene, but there are still many spatial and temporal gaps in our understanding of past tropical Pacific climate change. Many of the annually-resolved records of past ENSO variability are short, discontinuous, or from outside the tropical Pacific, whereas those records from the tropical Pacific often do not have the temporal resolution to accurately resolve the timing of individual El Niño events. Paleoclimate records from the Galápagos Islands are ideal for reconstructing past changes in tropical Pacific climate variability, since these islands are located in the heart of the ENSO phenomenon. Records from other lakes in the Galápagos have already suggested significant changes in ENSO frequency and the mean state of the eastern tropical Pacific throughout the Holocene. However, these lake sediment records have interannual temporal resolution at best, hampering our understanding of past ENSO dynamics. Here we present our initial findings from an additional Galápagos lake: Genovesa Crater Lake. The Genovesa sediment record is finely laminated and will likely provide a high-resolution paleoclimate record for this region of the tropical Pacific, as well as a means to test the hypotheses proposed by other ENSO reconstructions. Scanning μ-XRF time series of elemental abundances in the Genovesa sediment cores indicate that peaks in Ca abundance reflect the warm/wet season and El Niño events. We hypothesize that during warm/wet periods, a reduced sea bird population around the typically guanotropic Genovesa Crater Lake reduces the guano input into the lake, allowing layers of relatively clean carbonate to precipitate. During the cool season and La Niña events, guano input dilutes the precipitated carbonate. High-resolution pollen and diatom analyses will provide additional constraints on

Stable isotope record in annually laminated lake sediments from Lake Żabińskie (NE Poland) for the last millennium.

NASA Astrophysics Data System (ADS)

Gabryś, Alicja; Piotrowska, Natalia; Tylmann, Wojciech; Bonk, Alicja; Filipiak, Janusz; Wacnik, Agnieszka; Hernandez-Almeida, Ivan; Grosjean, Martin

2015-04-01

Stable isotope record of carbon (13C) and oxygen (18O) has been analysed from an annually laminated sediment from Lake Zabinskie (Mazurian Lakeland, NE Poland) with high resolution (1-3 yrs). The sediment layers which were formed in each year during the last millennium contain information about environmental changes in the past. The calcite layers are formed in lake sediment in warm months of the year, therefore the reconstruction of summer climate variables in the past is potentially possible. The investigation of correlation between isotope dataset and instrumental climate data for years 1897-2008 AD confirmed that theory. The record of temperature, precipitation and SPEI (Standardised Precipitation Evaporation Index) coefficient, which is a combination of both temperature and precipitation, was tested. The strongest linear correlations were found for most samples for June, July, August (JJA) months but in some cases the correlation coefficient was stronger when also May was taken into account. For the whole 120-yrs series the correlation between δ18O and average JJA temperature is 0.007, average JJA precipitation is 0.16 and average JJA SPEI is 0.20. Analyzing the results for 1897-2008 we can distinguish period 1960-2008 with relevantly stronger correlations: R(temperature) = 0.19, R(precipitation) = 0.20 and R(SPEI) = 0.45. This period is connected with cessation of human activity close to Lake Zabinskie. Reconstruction of climate variables for the last millennium was made using transfer function obtained for calibration period (1897-2008). Reconstructions showed that known climate extremes like Medieval Warm Period, Little Ice Age with Sporer (1420-1570), Maunder (1645-1715) and Dalton (1790-1820) Minimum was recorded in sediment from Lake Zabinskie. The presented study is a part of the project "Climate of northern Poland during the last 1000 years: Constraining the future with the past (CLIMPOL)", funded within Polish-Swiss Research Programme. http://www.climpol.ug.edu.pl

Earthquake Records of North Anatolian Fault from Sapanca Lake Sediments, NW Anatolia

NASA Astrophysics Data System (ADS)

Yalamaz, Burak; Cagatay, Namık; Acar, Dursun; Demirbag, Emin; Gungor, Emin; Gungor, Nurdan; Gulen, Levent

2014-05-01

We determined earthquake records in sediment cores of Sapanca Lake which is a pull-apart basin located along the North Anatolian Fault zone in NW Anatolia. The lake has a maximum depth of 55 m, and a surface area of 46.8 km2, measuring 16 km in E-W and 5 km in N-S directions. A systematic study of the sedimentological, physical and geochemical properties of three water-sediment interface cores, up to 75.7 cm long, located along depth transects ranging from 43 to 51.5 m water depths. The cores were analyzed using Geotek Multi Sensor Core Logger (MSCL) for physical properties, laser particle size analyzer for granulometry, TOC Analyzer for Total Organic Content (TOC) and Total Inorganic Carbon (TIC) analysis, Itrax-XRF Core Scanner for elemental analysis and digital X-RAY Radiography. The geochronology was determined using AMS radiocarbon and radionuclide methods. The Sapanca Lake earthquake records are characterized by mass flow units consisting of grey or dark grey coarse to fine sand and silty mud with sharp basal and transional upper boundaries. The units commonly show normal size grading with their basal parts showing high density, and high magnetic susceptibility and enrichment in one or more elements, such as Si, Ca, Tİ, K, Rb, Zr and Fe, indicative of coarse detrial input. Based on radionuclide and radiocarbon analyses the mass flow units are correlated with 1999 İzmit and Düzce earthquakes (Mw=7.4 and 7.2, respectively) , 1967 Mudurnu earthquake (Mw= 6,8), and 1957 Abant (Mw= 7.1) earthquake. Keywords: Sapanca Lake, North Anatolian Fault, Earthquake, Grain size, Itrax-XRF, MSCL

A 1200-Year Record of Rapid Climate Changes Across the Tropical Americas Identified from Lake Sediments (Invited)

NASA Astrophysics Data System (ADS)

Abbott, M.; Rodbell, D. T.; Stansell, N.; Bird, B. W.; Vuille, M.

2009-12-01

Well-dated, highly resolved lake sediment stratigraphies from similar catchments across the tropical Americas provide a means to investigate the timing, rate and direction of climate variability as well as providing a way to evaluate whether rapid changes occur synchronously in both hemispheres. This presentation focuses on the last 1500 years from three new high-resolution stable isotope records including Yuraicocha (12°32'S, 75°29'W), Pumacocha (10°41'S, 76° 3'36W), and Gancho (8°27'N, 80°51'W). These lakes are all sensitive to changes in P/E and the sediment records respond at subdecadal timescales. Additionally, the results from these sites are compared with lake level records from Titicaca (16°14'S, 68°37'W) and Blanca (8°19'N, 71°46'W) as well as other lake core and speleothem records from the region. The results show that in general conditions are dry across South America from ~800 AD until ~1300 AD with wetter conditions in Central America and the Caribbean. This pattern of dry conditions in tropical South America and wet conditions in the north reverses after ~1300 when conditions become wetter in South America, and drier in Central America and the Carrabin.

Hidden plastics of Lake Ontario, Canada and their potential preservation in the sediment record.

PubMed

Corcoran, Patricia L; Norris, Todd; Ceccanese, Trevor; Walzak, Mary Jane; Helm, Paul A; Marvin, Chris H

2015-09-01

Microplastics are a source of environmental pollution resulting from degradation of plastic products and spillage of resin pellets. We report the amounts of microplastics from various sites of Lake Ontario and evaluate their potential for preservation in the sediment record. A total of 4635 pellets were sampled from the Humber Bay shoreline on three sampling dates. Pellet colours were similar to those from the Humber River bank, suggesting that the river is a pathway for plastics transport into Lake Ontario. Once in the lake, high density microplastics, including mineral-polyethylene and mineral-polypropylene mixtures, sink to the bottom. The minerals may be fillers that were combined with plastics during production, or may have adsorbed to the surfaces of the polymers in the water column or on the lake bottom. Based on sediment depths and accumulation rates, microplastics have accumulated in the offshore region for less than 38 years. Their burial increases the chance of microplastics preservation. Shoreline pellets may not be preserved because they are mingled with organic debris that is reworked during storm events. Copyright © 2015 Elsevier Ltd. All rights reserved.

Modern processes of sediment formation in Lake Towuti, Indonesia, as derived from the composition of lake surface sediments

NASA Astrophysics Data System (ADS)

Hasberg, Ascelina; Melles, Martin; Morlock, Marina; Vogel, Hendrik; Russel, James M.; Bijaksana, Satria

2016-04-01

In summer 2015, a drilling operation funded by the International Continental Scientific Drilling Program (ICDP) was conducted at Lake Towuti (2.75°S, 121.5°E), the largest tectonically formed lake (surface area: 561 km²) of the Republic Indonesia. The Towuti Drilling Project (TDP) recovered more than 1000 meters of sediment core from three sites. At all three sites replicate cores down to 133, 154, and 174 m below lake floor have penetrated the entire lake sediment record, which is expected to comprise the past ca. 650.000 years continuously. Lake Towutís sediment record thus can provide unique information for instance concerning the climatic and environmental history in the Indo-Pacific-Warm-Pool (IPWP) and concerning the evolutionary biology in SE Asia. For a better understanding of the palaeoenvironmental proxies to be analyzed on the drill cores, the modern processes of sediment formation in the lake and in its catchment - under known environmental conditions - were investigated on a set of 84 lake sediment surface samples. Sampling was conducted by grab sampler (UWITEC Corp., Austria) in a grid of 1 to 4 km resolution that covers the entire lake. The samples were analyzed for inorganic geochemical composition (XRF powder scans and ICP-MS), magnetic susceptibility (Kappabridge), grain-size distribution (laser scanner), biogenic components (smear-slide analyses), biogenic silica contents (leaching), and carbonate, total organic carbon (TOC), nitrogen (TN), and sulfur (TS) concentrations (elemental analyzer). The sediments close to the lake shores and in front of the major river inlets are characterized by mean grain sizes coarser than average and high magnetic susceptibilities presented by high ratios of Cr, Ni, Co, and Zr. This reflects higher energies due to wave action and fluvial sediment supply, as well as the occurrence of magnetic minerals particularly in the sand and gravel fractions of the sediments. In regions of deeper waters and more distal to

Spatiotemporal climatic, hydrological, and environmental variations based on records of annually laminated lake sediments from northern Poland

NASA Astrophysics Data System (ADS)

Tylmann, W.; Blanke, L.; Kinder, M.; Loewe, T.; Mayr, C.; Ohlendorf, C.; Zolitschka, B.

2009-12-01

In northern Poland there is the unique opportunity to compare varved lake sediment records with distinct climatic trends along a 700 km long W-E transect. Annually laminated Holocene sediment sequences from Lake Lubinskie, Lake Suminko, Lake Lazduny, and Lake Szurpily were cored for high-resolution multiproxy climate and environmental reconstruction in the framework of the Polish-German project “Northern Polish Lake Research” (NORPOLAR). First results from a 139 cm long gravity core of Lake Lazduny (53°51.4’N, 21°57.3’E) document deposition of an organic (mean organic matter: 13.9%; mean biogenic opal: 9.8%) and highly carbonaceous gyttja (mean calcite content: 61.6%). The finely laminated sediment consists of biochemical varves. Pale spring/summer layers composed of autochthonous carbonates alternate with dark fall/winter layers made of organic and minerogenic detritus. The established chronology for the last 1500 calendar-years is based on thin section analysis supported by independent radiometric dating (C-14, Pb-210). Sedimentological, geochemical and stable isotope analyses were carried out with a decadal temporal resolution. Additionally, non-destructive and high-resolution XRF scanning data reveal a rhythmic variation in the Ca content that reflects seasonal calcite deposition. Redox-sensitive elements like Fe, Mn and S are interpreted to be the response to mean winter temperatures: colder winter temperatures → extended lake ice cover → intensification of meromixis → increased Fe/Mn ratio. In turn, these parameters can be linked to NAO (North Atlantic Oscillation) variability, because a negative NAO is related to colder and drier conditions in northeastern Europe. Climate variability is also mirrored by the δ13C record of the endogenic calcite fraction. In mid-latitude lakes calcite precipitation is dominated by productivity-controlled consumption of the dissolved inorganic carbon (DIC) pool. Thus the δ13C record potentially provides a

Isotopic chemical weathering behaviour of Pb derived from a high-Alpine Holocene lake-sediment record

NASA Astrophysics Data System (ADS)

Gutjahr, Marcus; Süfke, Finn; Gilli, Adrian; Anselmetti, Flavio; Glur, Lukas; Eisenhauer, Anton

2017-04-01

Several studies assessing the chemical weathering systematics of Pb isotopes provided evidence for the incongruent release of Pb from source rocks during early stages of chemical weathering, resulting in runoff compositions more radiogenic (higher) than the bulk source-rock composition [e.g. 1]. Deep NW Atlantic seawater Pb isotope records covering the last glacial-interglacial transition further support these findings. Clear excursions towards highly radiogenic Pb isotopic input in the deep NW Atlantic seen during the early Holocene, hence after the large-scale retreat of the Laurentide Ice Sheet in North America, are interpreted to be controlled by preferential release of radiogenic Pb from U- and Th-rich mineral phases during early stages of chemical weathering that are less resistant to chemical dissolution than other rock-forming mineral phases [2-4]. To date, however, no terrestrial Pb isotope record exists that could corroborate the evidence from deep marine sites for efficient late deglacial weathering and washout of radiogenic Pb. We present a high-resolution adsorbed Pb isotope record from a sediment core retrieved from Alpine Lake Grimsel (1908 m.a.s.l.) in Switzerland, consisting of 117 Pb compositions over the past 10 kyr. This high-Alpine study area is ideally located for incipient and prolonged chemical weathering studies. The method used to extract the adsorbed lake Pb isotope signal is identical to previous marine approaches targeting the authigenic Fe-Mn oxyhydroxides fraction within the lake sediments [5, 6]. The Pb isotope compositions are further accompanied by various elemental ratios derived from the same samples that equally trace climatic boundary conditions in the Grimsel Lake area. The Pb isotopic composition recorded in Lake Grimsel is remarkably constant throughout the majority of the Holocene until ˜2.5 ka BP, despite variable sediment composition and -age, and isotopically relatively close to the signature of the granitic source rock

Using lead isotopes and trace element records from two contrasting Lake Tanganyika sediment cores to assess watershed – Lake exchange

USGS Publications Warehouse

Odigie, Kingsley; Cohen, A.D.; Swarzenski, Peter W.; Flegal, R

2014-01-01

Lead isotopic and trace element records of two contrasting sediment cores were examined to reconstruct historic, industrial contaminant inputs to Lake Tanganyika, Africa. Observed fluxes of Co, Cu, Mn, Ni, Pb, and Zn in age-dated sediments collected from the lake varied both spatially and temporally over the past two to four centuries. The fluxes of trace elements were lower (up to 10-fold) at a mid-lake site (MC1) than at a nearshore site (LT-98-58), which is directly downstream from the Kahama and Nyasanga River watersheds and adjacent to the relatively pristine Gombe Stream National Park. Trace element fluxes at that nearshore site did not measurably change over the last two centuries (1815–1998), while the distal, mid-lake site exhibited substantial changes in the fluxes of trace elements – likely caused by changes in land use – over that period. For example, the flux of Pb increased by ∼300% from 1871 to 1991. That apparent accelerated weathering and detrital mobilization of lithogenic trace elements was further evidenced by (i) positive correlations (r = 0.77–0.99, p < 0.05) between the fluxes of Co, Cu, Mn, Ni, Pb, and Zn and those of iron (Fe) at both sites, (ii) positive correlations (r = 0.82–0.98, p < 0.01, n = 9) between the fluxes of elements (Al, Co, Cu, Fe, Mn, Ni, Pb, and Zn) and the mass accumulation rates at the offshore site, (iii) the low enrichment factors (EF < 5) of those trace elements, and (iv) the temporal consistencies of the isotopic composition of Pb in the sediment. These measurements indicate that accelerated weathering, rather than industrialization, accounts for most of the increases in trace element fluxes to Lake Tanganyika in spite of the development of mining and smelting operations within the lake’s watershed over the past century. The data also indicate that the mid-lake site is a much more sensitive and useful recorder of environmental changes than the nearshore site. Furthermore, the lead isotopic compositions

Climatic record of the Iberian peninsula from lake Moncortes' sediments

NASA Astrophysics Data System (ADS)

Cao, Min; Huguet, Carme; Rull, Valenti; Valero, Blas; Rosell-Mele, Antoni

2014-05-01

Climatic record of the Iberian peninsula from lake Moncortes' sediments Min Cao1, Carme Huguet1, Valenti Rull2, Blas L. Valero-Garces3, Antoni Rosell-Melé1,4 1Institut de Ciència i Tecnologia Ambientals (ICTA), Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Catalonia, Spain; 2Institut de Botanic de Barcelona (CSIC), Passeig del Migdia s/n, 08038, Barcelona, Spain, 3 Instituto Pirenaico de Ecologıa (CSIC), Avda. Montañana 1005, 50059 Zaragoza, Spain, 4Institució Catalana de Recerca i Estudis Avançats (ICREA), 08010 Barcelona, Catalonia, Spain. The continuing buildup of industrial greenhouse gases in the atmosphere and concomitant increase in global temperatures has made much of the world's society aware that decades to centuries of environmental change lie ahead, and that these will have profound economic, political and societal impacts. The Iberian Peninsula lies in the boundary between tropical and subtropical climates and seems to amplify the climatic signals form the northern hemisphere through both atmospheric and water circulation feedbacks, making it an ideal site to monitor Northern hemisphere climate changes. This extreme sensitivity to climatic changes also makes the Iberian Peninsula extremely vulnerable to future climate changes. This is why understanding sensitivity to climate change and the consequences it will have on both climate and the hydrological cycle is key to implement preventive measures. The aim of our study is to come up with a high resolution quantitative reconstruction of climate variability (temperature, production and precipitation) in the Iberian Peninsula from lake sediments. We also want to establish the relation between those changes and the ones observed in both ice cores from Greenland and paleotemperature records from marine sediments of the continental Iberian margin. For these reasons we sampled a core in Moncortes (42.3N, 0.99E), a lake of karstic origin with an average depth of 25m and an area of 0

A 300 year history of lead contamination in northern French Alps reconstructed from distant lake sediment records.

PubMed

Arnaud, F; Revel-Rolland, M; Bosch, D; Winiarski, T; Desmet, M; Tribovillard, N; Givelet, N

2004-05-01

Lead concentrations and isotopic ratios were measured along two well-dated sediment cores from two distant lakes: Anterne (2100 m a.s.l.) and Le Bourget (270 m a.s.l.), submitted to low and high direct human impact and covering the last 250 and 600 years, respectively. The measurement of lead in old sediment samples (>3000 BP) permits, in using mixing-models, the determination of lead concentration, flux and isotopic composition of purely anthropogenic origin. We thus show that since ca. 1800 AD the regional increase in lead contamination was mostly driven by coal consumption ((206)Pb/(207)Pb approximately 1.17-1.19; (206)Pb/(204)Pb approximately 18.3-18.6), which peaks around 1915 AD. The increasing usage of leaded gasoline, introduced in the 1920s, was recorded in both lakes by increasing Pb concentrations and decreasing Pb isotope ratios. A peak around 1970 ((206)Pb/(207)Pb approximately 1.13-1.16; (206)Pb/(204)Pb approximately 17.6-18.0) corresponds to the worldwide recorded leaded gasoline maximum of consumption. The 1973 oil crisis is characterised by a drastic drop of lead fluxes in both lakes (from approximately 35 to <20 mg cm(-2) yr(-1)). In the late 1980s, environmental policies made the Lake Anterne flux drop to pre-1900 values (<10 mg cm(-2) yr(-1)) while Lake Le Bourget is always submitted to an important flux (approximately 25 mg cm(-2) yr(-1)). The good match of our distant records, together and with a previously established series in an ice core from Mont Blanc, provides confidence in the use of sediments as archives of lead contamination. The integration of the Mont Blanc ice core results from Rosman et al. with our data highlights, from 1990 onward, a decoupling in lead sources between the high elevation sites (Lake Anterne and Mont Blanc ice core), submitted to a mixture of long-distance and regional contamination and the low elevation site (Lake Le Bourget), where regional contamination is predominant.

Catchment sediment flux: a lake sediment perspective on the onset of the Anthropocene?

NASA Astrophysics Data System (ADS)

Chiverrell, Richard

2014-05-01

Definitions of the Anthropocene are varied but from a geomorphological perspective broadly can be described as the interval of recent Earth history during which 'humans have had an 'overwhelming' effect on the Earth system' (Brown et al., 2013). Identifying the switch to a human-dominated geomorphic process regime is actually a challenging process, with in the 'Old World' ramping up of human populations and impacts on earth surface processes since the Neolithic/Mesolithic transition and the onset of agriculture. In the terrestrial realm lakes offer a unique window on changes in human forcing of earth surface processes from a sedimentary flux perspective, because unlike alluvial and hill-slope systems sedimentation is broadly continuous and uninterrupted. Dearing and Jones (2003) showed for a global dataset of lakes a 5-10 fold increase in sediment delivery comparing pre- and post-anthropogenic disturbance. Here sediment records from several lakes in lowland agricultural landscapes are presented to examine the changes in the flux and composition of materials delivered from their catchments. By definition the lakes record the switch to a human dominated system, but not necessary in accelerated sediment accumulation rates with changes in sediment composition equally important. Data from Crose, Hatch and Peckforton Meres, in lowland northwest England are interrogated producing quantitative land-cover reconstructions from pollen spectra calculated using the REVEALS model (Sugita, 2007), geochemical evidence for changes sediment provenance and flux, and 14C and stable Pb pollutant based chronological models detecting changes in sediment accumulation rate. The lake sediment geochemistry points to several phases of heightened human impact within these small agricultural catchments. Following small-in-scale forest cover reductions and limited impacts in terms of sediment flux during the Neolithic, the Bronze to Iron Age saw the first substantial reductions in forest cover

Possible Climatic Signal Recorded by Alkenone Distributions in Sediments from Freshwater and Saline Lakes on the Skarvsnes and Skallen Areas, Antarctica

NASA Astrophysics Data System (ADS)

Sawada, K.; Takeda, M.; Takano, Y.

2014-12-01

The distribution of long-chain (C37 - C39) alkenones in marine sediment has been well documented to record paleo-sea surface temperatures. The alkenones were also found in sediments of terrestrial saline lakes, and recently the calibrations of alkenone unsaturation indices - temperature have been established in continental areas. Furthermore, these biomarkers have been identified in lacustrine sediments on high-latitudinal terrestrial areas such as Greenland and Antarctica. In the present study, the alkenones were identified in the lacustrine sediment cores in freshwater (Lake Naga-ike) and saline lakes (Lake Suribati and Lake Funazoko) on the Skarvsnes, and a saline lake (Lake Skallen Oh-ike) on the Skallen, Antarctica. Here, we report that the alkenone distribution in the Antarctic lakes was examined as paleotemperature proxy. C37-C38 Tetra- and tri-unsaturated alkenones and C37 tetra- and tri-unsaturated alkenoates are identified in all sediment samples. The C37 di-unsaturated (C37:2) alkenones can be identified in sediments of surface layers (0-15 cm) of Lake Naga-ike and layers of 160-190 cm depth, in which age is ca. 3000 years BP by 14C dating, in Lake Skallen Ohike, and alkenone unsaturation index (UK37) is analyzed from these sediments. By using a calibration obtained from a culture strain Chrysotila lamellosa as reported by Nakamura et al. (2014), paleotemperatures are calculated to be 9.2-15ºC in surface sediments of Lake Naga-ike and 6.8-8.6ºC in Lake Skallen Oh-ike, respectively. The estimated temperatures are concordant with summer temperature of lake waters observed in Lake Naga-ike. Also, the highest concentrations of the alkenones and alkenoates are observed in deeper (older) sediment layers from Lake Naga-ikes, which has not been connected the ocean and intruded sea water. This implies that the alkenones are originated from indigenous biological organism(s) in Antarctic lake water. The class distributions (unsaturation ratios) of alkenones

Expanded spatial extent of the Medieval Climate Anomaly revealed in lake-sediment records across the boreal region in northwest Ontario.

PubMed

Laird, Kathleen R; Haig, Heather A; Ma, Susan; Kingsbury, Melanie V; Brown, Thomas A; Lewis, C F Michael; Oglesby, Robert J; Cumming, Brian F

2012-09-01

Multi-decadal to centennial-scale shifts in effective moisture over the past two millennia are inferred from sedimentary records from six lakes spanning a ~250 km region in northwest Ontario. This is the first regional application of a technique developed to reconstruct drought from drainage lakes (open lakes with surface outlets). This regional network of proxy drought records is based on individual within-lake calibration models developed using diatom assemblages collected from surface sediments across a water-depth gradient. Analysis of diatom assemblages from sediment cores collected close to the near-shore ecological boundary between benthic and planktonic diatom taxa indicated this boundary shifted over time in all lakes. These shifts are largely dependent on climate-driven influences, and can provide a sensitive record of past drought. Our lake-sediment records indicate two periods of synchronous signals, suggesting a common large-scale climate forcing. The first is a period of prolonged aridity during the Medieval Climate Anomaly (MCA, c. 900-1400 CE). Documentation of aridity across this region expands the known spatial extent of the MCA megadrought into a region that historically has not experienced extreme droughts such as those in central and western north America. The second synchronous period is the recent signal of the past ~100 years, which indicates a change to higher effective moisture that may be related to anthropogenic forcing on climate. This approach has the potential to fill regional gaps, where many previous paleo-lake depth methods (based on deeper centrally located cores) were relatively insensitive. By filling regional gaps, a better understanding of past spatial patterns in drought can be used to assess the sensitivity and realism of climate model projections of future climate change. This type of data is especially important for validating high spatial resolution, regional climate models. © 2012 Blackwell Publishing Ltd.

Historical Records of Mercury Stable Isotopes in Sediments of Tibetan Lakes

NASA Astrophysics Data System (ADS)

Yin, Runsheng; Feng, Xinbin; Hurley, James P.; Krabbenhoft, David P.; Lepak, Ryan F.; Kang, Shichang; Yang, Handong; Li, Xiangdong

2016-03-01

The Tibetan Plateau (TP), known as the “Third Pole”, is a critical zone for atmospheric mercury (Hg) deposition. Increasing anthropogenic activities in the globe leads to environmental changes, which may affect the loading, transport and deposition of Hg in the environment. However, the deposition history and geochemical cycling of Hg in the TP is still uncertain. Our records of Hg and Hg isotopes in sediment profiles of the two largest lakes in the TP, Lake Qinghai and Nam Co, show increased Hg influx since last century, with the maximum Hg influx enrichment ratios of 5.4 and 3.5 in Lake Qinghai and Nam Co, respectively. Shifts in negative δ 202Hg in Lake Qinghai (-4.55 to -3.15‰) and Nam Co (-5.04 to -2.16‰) indicate increased atmospheric Hg deposition through rainfall, vegetation and runoff of soils. Mass independent fractionation of both even-Hg (∆ 200Hg: +0.05 to +0.10‰) and odd-Hg (∆ 199Hg: +0.12 to +0.31‰) isotopes were observed. Positive Δ 200Hg suggest high proportion of precipitation-derived Hg in the TP, whereas the positive Δ 199Hg results from Hg(II) photo-reduction. Both lakes show increasing Δ 199Hg since the 1900 s, and we conclude that with the decrease of ice duration, Hg(II) photo-reduction may have been accelerated in these TP lakes.

Historical Records of Mercury Stable Isotopes in Sediments of Tibetan Lakes.

PubMed

Yin, Runsheng; Feng, Xinbin; Hurley, James P; Krabbenhoft, David P; Lepak, Ryan F; Kang, Shichang; Yang, Handong; Li, Xiangdong

2016-03-21

The Tibetan Plateau (TP), known as the "Third Pole", is a critical zone for atmospheric mercury (Hg) deposition. Increasing anthropogenic activities in the globe leads to environmental changes, which may affect the loading, transport and deposition of Hg in the environment. However, the deposition history and geochemical cycling of Hg in the TP is still uncertain. Our records of Hg and Hg isotopes in sediment profiles of the two largest lakes in the TP, Lake Qinghai and Nam Co, show increased Hg influx since last century, with the maximum Hg influx enrichment ratios of 5.4 and 3.5 in Lake Qinghai and Nam Co, respectively. Shifts in negative δ (202)Hg in Lake Qinghai (-4.55 to -3.15‰) and Nam Co (-5.04 to -2.16‰) indicate increased atmospheric Hg deposition through rainfall, vegetation and runoff of soils. Mass independent fractionation of both even-Hg (∆ (200)Hg: +0.05 to +0.10‰) and odd-Hg (∆ (199)Hg: +0.12 to +0.31‰) isotopes were observed. Positive Δ (200)Hg suggest high proportion of precipitation-derived Hg in the TP, whereas the positive Δ (199)Hg results from Hg(II) photo-reduction. Both lakes show increasing Δ (199)Hg since the 1900 s, and we conclude that with the decrease of ice duration, Hg(II) photo-reduction may have been accelerated in these TP lakes.

A Holocene Sediment Record of Phosphorus Accumulation in Shallow Lake Harris, Florida (USA) Offers New Perspectives on Recent Cultural Eutrophication

PubMed Central

Kenney, William F.; Brenner, Mark; Curtis, Jason H.; Arnold, T. Elliott; Schelske, Claire L.

2016-01-01

We studied a complete Holocene sediment record from shallow (zmax = 9.7 m) Lake Harris, Florida (USA) to infer the historical development of the lake and its current eutrophic status. We used 210Pb and 14C to date the 5.9-m sediment sequence (core LH-6-13) and determined accumulation rates for bulk sediment, organic matter, calcium carbonate, phosphorus fractions and biogenic silica fractions. The chronology of changes in sediment characteristics for LH-6-13 is consistent with the general paleoenvironmental framework established by core studies from other Florida lakes. Lake Harris began to fill with water in the early Holocene, ca. 10,680 cal a BP. A shift from carbonate-dominated to organic-rich sediments ca. 5,540 cal a BP corresponds to a transition to wetter climate in the middle Holocene. A rapid increase in diatom biogenic silica concentrations and accumulation rates ca. 2,600 cal a BP signals that the lake had deepened to its modern limnetic state. In LH-6-13, an up-core decrease in rates of accumulation for several sediment variables indicates time-course oligotrophication of the lake through the Holocene. In near-surface sediments, abrupt increases in the accumulation rates of these same variables indicate progressive cultural eutrophication after ca. AD 1900. Comparison of the modern state of Lake Harris to its condition 50–100 years ago provides a measure of the impact of recent cultural eutrophication. Because the pre-disturbance trajectory of this lake was one of oligotrophication, the true impact of cultural eutrophication is even greater than what is inferred from the changes over the past century. PMID:26789518

Coastal Lake Record of Holocene Paleo-Storms from Northwest Florida

NASA Astrophysics Data System (ADS)

Donoghue, J. F.; Coor, J. L.; Wang, Y.; Das, O.; Kish, S.; Elsner, J.; Hu, X. B.; Niedoroda, A. W.; Ye, M.

2009-12-01

The northwest Florida coast of the Gulf of Mexico has an unusually active storm history. Climate records for a study area in the mid-region of the Florida panhandle coast show that 29 hurricanes have made landfall within a 100-km radius during historic time. These events included 9 major storms (category 3 or higher). A longer-term geologic record of major storm impacts is essential for better understanding storm climatology and refining morphodynamic models. The Florida panhandle region contains a series of unique coastal lakes which are long-lived and whose bottom sediments hold a long-term record of coastal storm occurrence. The lakes are normally isolated from the open Gulf, protected behind a near-continuous dune barrier. Lake water is normally fresh to brackish. Lake bottom sediments consist of organic-rich muds. During major storms the dunes are breached and the lakes are temporarily open to marine water and the possibility of sandy overwash. Both a sedimentologic and geochemical signature is imparted to the lake sediments by storm events. Bottom sediment cores have been collected from the lakes. The cores have been subsampled and subjected to sedimentologic, stable isotopic and geochronologic analyses. The result is a sediment history of the lakes, and a record of storm occurrence during the past few millennia. The outcome is a better understanding of the long-term risk of major storms. The findings are being incorporated into a larger model designed to make reliable predictions of the effects of near-future climate change on natural coastal systems and on coastal infrastructure, and to enable cost-effective mitigation and adaptation strategies.

Stable carbon and oxygen isotope record of central Lake Erie sediments

USGS Publications Warehouse

Tevesz, M.J.S.; Spongberg, A.L.; Fuller, J.A.

1998-01-01

Stable carbon and oxygen isotope data from mollusc aragonite extracted from sediment cores provide new information on the origin and history of sedimentation in the southwestern area of the central basin of Lake Erie. Sediments infilling the Sandusky subbasin consist of three lithologic units overlying glacial deposits. The lowest of these is a soft gray mud overlain by a shell hash layer containing Sphaerium striatinum fragments. A fluid mud unit caps the shell hash layer and extends upwards to the sediment-water interface. New stable isotope data suggest that the soft gray mud unit is of postglacial, rather than proglacial, origin. These data also suggest that the shell hash layer was derived from erosional winnowing of the underlying soft gray mud layer. This winnowing event may have occurred as a result of the Nipissing flood. The Pelee-Lorain moraine, which forms the eastern boundary of the Sandusky subbasin, is an elevated area of till capped by a sand deposit that originated as a beach. The presence of both the shell hash layer and relict beach deposit strengthens the interpretation that the Nipissing flood was a critical event in the development of the southwestern area of the central basin of Lake Erie. This event, which returned drainage from the upper lakes to the Lake Erie basin, was a dominant influence on regional stratigraphy, bathymetry, and depositional setting.

Effect of recent climate change on Arctic Pb pollution: a comparative study of historical records in lake and peat sediments.

PubMed

Liu, Xiaodong; Jiang, Shan; Zhang, Pengfei; Xu, Liqiang

2012-01-01

Historical changes of anthropogenic Pb pollution were reconstructed based on Pb concentrations and isotope ratios in lake and peat sediment profiles from Ny-Ålesund of Arctic. The calculated excess Pb isotope ratios showed that Pb pollution largely came from west Europe and Russia. The peat profile clearly reflected the historical changes of atmospheric deposition of anthropogenic Pb into Ny-Ålesund, and the result showed that anthropogenic Pb peaked at 1960s-1970s, and thereafter a significant recovery was observed by a rapid increase of (206)Pb/(207)Pb ratios and a remarkable decrease in anthropogenic Pb contents. In contrast to the peat record, the longer lake record showed relatively high anthropogenic Pb contents and a persistent decrease of (206)Pb/(207)Pb ratios within the uppermost samples, suggesting that climate-sensitive processes such as catchment erosion and meltwater runoff might have influenced the recent change of Pb pollution record in the High Arctic lake sediments. Copyright © 2011 Elsevier Ltd. All rights reserved.

D/H Ratios From Sierra Nevada Varved Lake Sediments Record Decadal Hydroclimate Variability During The Medieval Period

NASA Astrophysics Data System (ADS)

Roach, L. D.; Cayan, D. R.; Sessions, A. L.; Charles, C. D.; Anderson, R. S.

2009-12-01

Assessment of the risks of persistent drought requires multiple realizations of decadal and centennial scale hydroclimate variability that extend beyond the relatively short period of instrumental record. Much remains to be learned about the so called “mega droughts” in the Sierra Nevada Mountains, where various lines of evidence point toward the occurrence of severe, decades-long droughts during Medieval times, approximately 900-1400 AD. Here we present a continuous, decadal scale record of hydroclimate variability in the Sierra Nevada Mountains that extends through the heart of the purported Medieval mega droughts. Previous work on the stable hydrogen isotope (D/H) ratios of refractory plant lipid compounds stored in lake sediments demonstrated that these compounds reflect the D/H values of lake water and/or shallow ground water--reservoirs both fed by local precipitation. Lake sediment D/H can therefore reflect the processes that determine D/H of precipitation, including temperature, humidity and moisture source. We have measured D/H of aquatic and terrestrial plant fatty acids extracted from a suite of sediment cores collected at Swamp Lake (elevation: 1554m), in Yosemite National Park, along the Sierra Nevada crest. Measurements with biennial resolution were made for two time periods: the 20th century and the 13th-15th centuries. D/H fluctuations in 20th century sediment contain relatively strong decadal structure. Comparison with instrumentally recorded climate variability reveals that lower D/H concentrations are associated with years of higher than normal annual precipitation, cooler than normal wintertime temperatures, and positive April 1 Snow Water Equivalent (SWE) anomalies throughout the Sierra Nevada, (and conversely for elevated D/H concentrations). The range of variability is approximately 50‰. These associations may be driven by the variable mass-balance impact of evaporation on the isotopic composition of lake water and shallow groundwater

The glacial/deglacial history of sedimentation in Bear Lake, Utah and Idaho

USGS Publications Warehouse

Rosenbaum, J.G.; Heil, C.W.

2009-01-01

Bear Lake, in northeastern Utah and southern Idaho, lies in a large valley formed by an active half-graben. Bear River, the largest river in the Great Basin, enters Bear Lake Valley ???15 km north of the lake. Two 4-m-long cores provide a lake sediment record extending back ???26 cal k.y. The penetrated section can be divided into a lower unit composed of quartz-rich clastic sediments and an upper unit composed largely of endogenic carbonate. Data from modern fluvial sediments provide the basis for interpreting changes in provenance of detrital material in the lake cores. Sediments from small streams draining elevated topography on the east and west sides of the lake are characterized by abundant dolomite, high magnetic susceptibility (MS) related to eolian magnetite, and low values of hard isothermal remanent magnetization (HIRM, indicative of hematite content). In contrast, sediments from the headwaters of the Bear River in the Uinta Mountains lack carbonate and have high HIRM and low MS. Sediments from lower reaches of the Bear River contain calcite but little dolomite and have low values of MS and HIRM. These contrasts in catchment properties allow interpretation of the following sequence from variations in properties of the lake sediment: (1) ca. 26 cal ka-onset of glaciation; (2) ca. 26-20 cal ka-quasicyclical, millennial-scale variations in the concentrations of hematite-rich glacial fl our derived from the Uinta Mountains, and dolomite- and magnetite-rich material derived from the local Bear Lake catchment (reflecting variations in glacial extent); (3) ca. 20-19 cal ka-maximum content of glacial fl our; (4) ca. 19-17 cal ka-constant content of Bear River sediment but declining content of glacial fl our from the Uinta Mountains; (5) ca. 17-15.5 cal ka-decline in Bear River sediment and increase in content of sediment from the local catchment; and (6) ca. 15.5-14.5 cal ka-increase in content of endogenic calcite at the expense of detrital material. The onset

The history of Cesium-137 liquid emissions by Mühleberg Nuclear Power Plant (Switzerland) is recorded in Lake Biel sediments

NASA Astrophysics Data System (ADS)

Girardclos, Stéphanie; Faessler, Jérôme; Loizeau, Jean-Luc; Zehringer, Markus

2014-05-01

Lake sediments record changes happening in their upstream river catchment and regional environment which includes traces of artificial radionuclides emissions deriving from human activities. 137Cs emissions started worldwide in the early 1950's and peaked in 1963-64 due to nuclear bomb tests in the high atmosphere. A second 137Cs activity peak, due to the 1986 Chernobyl catastrophe is recorded in sediment archives from central Europe. These two events (1963/64 and 1986) serve routinely as time markers for recent lake records. Nuclear Power Plants (NPPs) are often constructed along river course for cooling purposes. Since 1972, Mühleberg NPP (central Switzerland) lies 18 km upstream Lake Biel and releases radioactive liquid emissions into the Aare river which adds to the diffuse - above mentioned - radioactive pollution, as revealed by Albrecht et al. (1995; 1998) and recently confirmed by Thevenon et al. (2013) from Lake Biel sediments. The water of Lake Biel is used as drinking water for ca. 60'000 inhabitants and its outflowing water is further used by downstream cities lying on the Aare-Rhine course such as Basel (200'000 inhab.) In this study, the 137Cs activity curve of a 90-cm-long sediment core (BIE10-8), retrieved in April 2010 from the central Lake Biel basin at ca. 50 m depth, and measured by gamma ray spectrometry using high resolution germanium detectors, confirms previous work and reveals a new peak for the year 1998-2000, as observed by Thevenon et al. (2013). This peak is most certainly due to Mühleberg NPP as shown by the good correlation with declared 137Cs liquid emissions indicating a significant increase in 1998-99. Decay corrected activity data, converted into 137Cs fluxes, point to water pollution by Mühleberg NPP in 1975-1985 as being similar to those linked to the catastrophic events in 1963-64 and 1986 (about 75%). As former study showed that Lake Biel sediments scavenge only a portion of the total radionuclide in water, i.e. 30-55% for

Initial geochemistry data of the Lake Ohrid (Macedonia, Albania) "DEEP" site sediment record: The ICDP SCOPSCO drilling project

NASA Astrophysics Data System (ADS)

Francke, Alexander; Wagner, Bernd; Krastel, Sebastian; Lindhorst, Katja; Mantke, Nicole; Klinghardt, Dorothea

2014-05-01

Lake Ohrid, located at the border of Macedonia and Albania is about 30 km long, 15 km wide and up to 290 m deep. Formed within a tectonic graben, Lake Ohrid is considered to be the oldest lake in Europe. The ICDP SCOPSCO (Scientific Collaboration of Past Speciation Conditions in Lake Ohrid) deep drilling campaign at Lake Ohrid in spring 2013 aimed (a) to obtain more precise information about the age and origin of the lake, (b) to unravel the seismotectonic history of the lake area including effects of major earthquakes and associated mass wasting events, (c) to obtain a continuous record containing information on volcanic activities and climate changes in the central northern Mediterranean region, and (d) to better understand the impact of major geological/environmental events on general evolutionary patterns and shaping an extraordinary degree of endemic biodiversity as a matter of global significance. Drilling was carried out by DOSECC (Salt Lake City, USA) using the DLDS (Deep Lake Drilling System) with a hydraulic piston corer for surface sediments and rotation drilling for harder, deeper sediments. Overall, about 2,100 m of sediment were recovered from 4 drill sites. At the "DEEP" site in the center of the lake, seismic data indicated a maximum sediment fill of ca. 700 m, of which the uppermost 568 m sediment were recovered. Initial data from core catcher samples and on-site susceptibility measurements indicate that the sediment sequence covers more than 1.2 million years and provides a continuous archive of environmental and climatological variability in the area. Currently, core opening, core description, XRF and MSCL -scanning, core correlation, and sub-sampling of the sediment cores from the "DEEP" site is conducted at the University of Cologne. High-resolution geochemical data obtained from XRF-scanning imply that the sediments from the "DEEP" site are highly sensitive to climate and environmental variations in the Balkan area over the last few glacial

Expressions of climate perturbations in western Ugandan crater lake sediment records during the last 1000 years

NASA Astrophysics Data System (ADS)

Mills, K.; Ryves, D. B.; Anderson, N. J.; Bryant, C. L.; Tyler, J. J.

2014-08-01

Equatorial East Africa has a complex regional patchwork of climate regimes, sensitive to climate fluctuations over a variety of temporal and spatial scales during the late Holocene. Understanding how these changes are recorded in and interpreted from biological and geochemical proxies in lake sedimentary records remains a key challenge to answering fundamental questions regarding the nature, spatial extent and synchroneity of climatic changes seen in East African palaeo-records. Using a paired lake approach, where neighbouring lakes share the same geology, climate and landscape, it might be expected that the systems will respond similarly to external climate forcing. Sediment cores from two crater lakes in western Uganda spanning the last ~1000 years were examined to assess diatom community responses to late Holocene climate and environmental changes, and to test responses to multiple drivers using redundancy analysis (RDA). These archives provide annual to sub-decadal records of environmental change. Lakes Nyamogusingiri and Kyasanduka appear to operate as independent systems in their recording of a similar hydrological response signal via distinct diatom records. However, whilst their fossil diatom records demonstrate an individualistic, indirect response to external (e.g. climatic) drivers, the inferred lake levels show similar overall trends and reflect the broader patterns observed in Uganda and across East Africa. The lakes appear to be sensitive to large-scale climatic perturbations, with evidence of a dry Medieval Climate Anomaly (MCA; ca. AD 1000-1200). The diatom record from Lake Nyamogusingiri suggests a drying climate during the main phase of the Little Ice Age (LIA) (ca. AD 1600-1800), whereas the diatom response from the shallower Lake Kyasanduka is more complex (with groundwater likely playing a key role), and may be driven more by changes in silica and other nutrients, rather than by lake level. The sensitivity of these two Ugandan lakes to regional

Local to regional scale industrial heavy metal pollution recorded in sediments of large freshwater lakes in central Europe (lakes Geneva and Lucerne) over the last centuries.

PubMed

Thevenon, Florian; Graham, Neil D; Chiaradia, Massimo; Arpagaus, Philippe; Wildi, Walter; Poté, John

2011-12-15

This research first focuses on the spatial and temporal patterns of heavy metals from contrasting environments (highly polluted to deepwater sites) of Lake Geneva. The mercury (Hg) and lead (Pb) records from two deepwater sites show that the heavy metal variations before the industrial period are primarily linked to natural weathering input of trace elements. By opposition, the discharge of industrial treated wastewaters into Vidy Bay of Lake Geneva during the second part of the 20th century, involved the sedimentation of highly metal-contaminated sediments in the area surrounding the WWTP outlet pipe discharge. Eventually, a new Pb isotope record of sediments from Lake Lucerne identifies the long-term increasing anthropogenic lead pollution after ca. 1500, probably due to the development of metallurgical activities during the High Middle Ages. These data furthermore allows to compare the recent anthropogenic sources of water pollution from three of the largest freshwater lakes of Western Europe (lakes Geneva, Lucerne, and Constance). High increases in Pb and Hg highlight the regional impact of industrial pollution after ca. 1750-1850, and the decrease of metal pollution in the 1980s due to the effects of remediation strategies such as the implementation of wastewater treatment plants (WWTPs). However, at all the studied sites, the recent metal concentrations remain higher than pre-industrial levels. Moreover, the local scale pollution data reveal two highly contaminated sites (>100 μg Pb/g dry weight sediment) by industrial activities, during the late-19th and early-20th centuries (Lake Lucerne) and during the second part of the 20th century (Vidy Bay of Lake Geneva). Overall, the regional scale pollution history inferred from the three large and deep perialpine lakes points out at the pollution of water systems by heavy metals during the last two centuries due to the discharge of industrial effluents. Copyright © 2011 Elsevier B.V. All rights reserved.

Rock Magnetic Properties, Paleosecular Variation Record and Relative Paleointensity Stack between 11 and 21 14C kyr B.P. From Sediment Cores, Lake Moreno (Argentina)

NASA Astrophysics Data System (ADS)

Gogorza, C. S.; Irurzun, M. A.; Lirio, J. M.; Nunez, H.; Chaparro, M. A.; Sinito, A. M.

2008-05-01

We conducted a detailed study of natural remanence and rock magnetic properties on sediments cores from lake Moreno (South-Western Argentina). Based on these measurements, we constructed a paleosecular variation (PSV) record (Irurzun et al., 2008) and a relative paleointensity stack for the period 11-21 14C. The Declination and Inclination logs of the characteristic remanent magnetization for the cores as function of shortened depth are obtained. The data from all cores were combined to obtain a composite record using the Fisher method. Comparison between stacked inclination and declination records of lake Moreno and results obtained in previous works, lake Escondido (Gogorza et al., 1999; Gogorza et al., 2002) and lake El Trébol (Irurzun et al., 2008), shows good agreement. This agreement made possible to transform the stacked curves into time series that spans the interval 11 and 21 14C kyr B.P. Rock magnetic properties of the sediments cores showed uniform magnetic mineralogy and grain size, suggesting that they were suitable for relative paleointensity studies. The remanent magnetization at 20mT (NRM20mT) was normalized using the anhysteric remanent magnetization at 20mT (ARM20mT), the saturation of the isothermal remanent magnetization at 20mT (SIRM20mT) and the low field magnetic susceptibility {k}. Coherence analysis showed that the normalized records were not affected by local environmental conditions. The recorded pseudo-Thellier paleointensity was compared with records obtained from conventional normalizing methods. Comparing the paleointensity curves with others obtained previously in other lakes in the area has allowed us to reach reliable conclusions about centennial-scale features. References: Gogorza, C.S.G., Sinito, A.M., Di Tommaso, I., Vilas, J.F., Creer, K., Núnez, H. Holocene Geomagnetic Secular Variations Recorded by Sediments from Escondido lake (South Argentina). Earth, Planets and Space, V51(2), 93- 106. 1999. Gogorza, C.S.G., Sinito, A

Are lake sediments mere archives of degraded organic matter? - evidence of rapid biotic changes tracked in sediments of pre-alpine Lake Lunz, Austria

NASA Astrophysics Data System (ADS)

Hollaus, Lisa-Maria; Khan, Samiullah; Schelker, Jakob; Ejarque, Elisabet; Battin, Tom; Kainz, Martin

2016-04-01

Lake sediments are used as sentinels of changes in organic matter composition and dynamics within lakes and their catchments. In an effort to investigate how past and recent hydrological extreme events have affected organic matter composition in lake sediments, we investigated the biogeochemical composition of sediment cores and settling particles, using sediment traps in the pre-alpine, oligotrophic Lake Lunz, Austria. We assessed annual sedimentation rates using 137Cs and 210Pb, time integrated loads of settling particles, analyze stable carbon (δ13C) and nitrogen (δ15N) isotopes to track changes of carbon sources and trophic compositions, respectively, and use source-specific fatty acids as indicators of allochthonous, bacterial, and algal-derived organic matter. Preliminary results indicate that settling particles of Lake Lunz (33 m depth) contain high algae-derived organic matter, as assessed by long-chain polyunsaturated fatty acids (LC-PUFA), indicating low degradation of such labile organic matter within the water column of this lake. However, LC-PUFA decreased rapidly in sediment cores below the sediment-water interface. Concentrations of phosphorous remained stable throughout the sediment cores (40 cm), suggesting that past changes in climatic forcing did not alter the load of this limiting nutrient in lakes. Ongoing work reveals dramatic biotic changes within the top layers of the sediment cores as evidenced by high numbers of small-bodied cladocerans (e.g., Bosmina) and large-bodied zooplankton (e.g., Daphnia) are only detected at lower sediment layers. Current research on these lake sediments is aimed at investigating how organic matter sources changed during the past century as a result of recorded weather changes.

Holocene pollen and sediment record from the tangle lakes area, central Alaska

USGS Publications Warehouse

Ager, Thomas A.; Sims, John D.

1981-01-01

Pollen and sediments have been analyzed from a 5.5 meter‐length core of lacustrine sediments from Tangle Lakes, in the Gulkana Upland south of the Alaska Range (63 ° 01 ‘ 46”; N. latitude, 146° 03 ‘ 48 “ W. longitude). Radiocarbon ages indicate that the core spans the last 4700 years. The core sediments are sandy silt and silty clay; the core shows distinct rhythmic laminations in the lower 398 cm. The laminae appear to be normally graded; peat fibers and macerated plant debris are more abundant near the tops of the laminae. Six volcanic‐ash layers are present in the upper 110 cm of the core.Present‐day vegetation of the Tangle Lakes area is mesic shrub tundra and open spruce woodland, with scattered patches of shrub willow (Salix), balsam poplar (P. balsamifera), spruce (Picea), paper birch (Betula papyrifera), and alder (Alnus). Pollen analysis of 27 core samples suggests that this vegetation type has persisted throughout the past 4700 years, except for an apparently substantial increase in Picea beginning about 3500 years B.P. Percentages of Picea pollen are very low (generally 1–3 percent) in the lower 2 meters of core (ca. 4700 to 3500 years B.P.), but rise to 13–18 percent in the upper 3.4 meters (ca. 3500 years B.P. to present). Previously reported data from this area indicate that Picea trees initially arrived in the Tangle Lakes area about 9100 years B.P., at least 2.5 to 3 thousand years after deglaciation of the region. The present investigation suggests that Picea trees became locally scarce or died out sometime after about 9000 years B.P. but before 4700 years B.P., then reinvaded the area about 3500 years B.P. If this extrapolated age for the Picea reinvasion is accurate it suggests that local expansion of the Picea population coincides with the onset of a Neoglacial interval of cooler, moister climate. This is an unexpected result, because intervals of cooler climate generally coincide with lowering of the altitudinal limit of

Solar cycles and depositional processes in annual 10Be from two varved lake sediment records

NASA Astrophysics Data System (ADS)

Czymzik, Markus; Muscheler, Raimund; Brauer, Achim; Adolphi, Florian; Ott, Florian; Kienel, Ulrike; Dräger, Nadine; Słowiński, Michał; Aldahan, Ala; Possnert, Göran

2015-10-01

Beryllium 10 concentrations (10Becon) were measured at annual resolution from varved sediment cores of Lakes Tiefer See (TSK) and Czechowskie (JC) for the period 1983-2009 (∼solar cycles 22 and 23). Calibrating the 10Becon time-series against complementing proxy records from the same archive as well as local precipitation and neutron monitor data, reflecting solar forced changes in atmospheric radionuclide production, allowed (i) identifying the main depositional processes and (ii) evaluating the potential for solar activity reconstruction. 10Becon in TSK and JC sediments are significantly correlated to varying neutron monitor counts (TSK: r = 0.5, p = 0.05, n = 16; JC: r = 0.46, p = 0.03, n = 22). However, the further correlations with changes in organic carbon contents in TSK as well as varying organic carbon and detrital matter contents in JC point to catchment specific biases in the 10Becon time-series. In an attempt to correct for these biases multiple regression analysis was applied to extract an atmospheric 10Be production signal (10Beatmosphere). To increase the signal to noise ratio a 10Be composite record (10Becomposite) was calculated from the TSK and JC 10Beatmosphere time-series. 10Becomposite is significantly correlated to variations in the neutron monitor record (r = 0.49, p = 0.01, n = 25) and matches the expected amplitude changes in 10Be production between solar cycle minima and maxima. This calibration study on 10Be from two sites indicates the large potential but also, partly site-specific, limitations of 10Be in varved lake sediments for solar activity reconstruction.

A ~20,000 year history of glacial variability in the tropical Andes recorded in lake sediments from the Cordillera Blanca, Peru

NASA Astrophysics Data System (ADS)

Stansell, N.; Rodbell, D. T.; Moy, C. M.

2010-12-01

Pro-glacial lake sediments from the Cordillera Blanca, Peru contain continuous records of climate variability spanning the Last Glacial Maximum to present day. Here we present results from two alpine lake basins in the Queshgue Valley (9.8°S, 77.3°W) that contain high-resolution records of clastic sediment deposition for the last ~20,000 years. Radiocarbon-dated sediment cores were scanned at 0.5 to 1.0 cm resolution using a profiling x-ray fluorescence scanner for major and minor element distributions. In addition, we measured down-core variations in magnetic susceptibility, organic carbon, biogenic silica and calcium carbonate. Samples of bedrock and sediments from glacial moraines in the Queshgue watershed were analyzed using an ICP-MS in order to fingerprint and trace the source of glacial sediments deposited in the lakes. The bedrock is dominated by a combination of granodiorite with high Sr concentrations and meta-sedimentary rocks with high Zr values. Because the glacial sediments proximal to the modern glacier terminus are composed mostly of the granodiorite end-member, we interpret changes in Sr and clastic sediment concentrations in the lake sediment profiles as proxies for past glacial variability. Preliminary results indicate that glaciers retreated soon after ~14,500 cal yr BP and remained less extensive during the remaining late Glacial Stage and early Holocene. Gradually increasing clastic sediments through the middle and late Holocene indicate that glaciers became progressively larger, or more erosive towards present day. However, this overall Holocene trend of increasing glacier extent was interrupted by multiple periods of centennial- to millennial-scale ice margin retreat. For example, relative peaks in clastic sediments occurred from ~14,500 to 6000, 5600 to 5000, 4600 to 4200, 3600 to 3200, 2800 to 2700, 2400 to 2200, 1750 to 1550, 1100 to 900 cal yr BP, and during the Little Ice Age (~700 to 50 cal yr BP), while periods of low clastic

A millennium of metallurgy recorded by lake sediments from Morococha, Peruvian Andes.

PubMed

Cooke, Colin A; Abbott, Mark B; Wolfe, Alexander P; Kittleson, John L

2007-05-15

To date, information concerning pre-Colonial metallurgy in South America has largely been limited to the archaeological record of artifacts. Here, we reconstruct a millennium of smelting activity in the Peruvian Andes using the lake-sediment stratigraphy of atmospherically derived metals (Pb, Zn, Cu, Ag, Sb, Bi, and Ti) and lead isotopic ratios (206Pb/ 207Pb) associated with smelting from the Morococha mining region in the central Peruvian Andes. The earliest evidence for metallurgy occurs ca. 1000 A.D., coinciding with the fall of the Wari Empire and decentralization of local populations. Smelting during this interval appears to have been aimed at copper and copper alloys, because of large increases in Zn and Cu relative to Pb. A subsequent switch to silver metallurgy under Inca control (ca. 1450 to conquest, 1533 A.D.) is indicated by increases in Pb, Sb, and Bi, a conclusion supported by further increases of these metals during Colonial mining, which targeted silver extraction. Rapid development of the central Andes during the 20th century raised metal burdens by an order of magnitude above previous levels. Our results represent the first evidence for pre-Colonial smelting in the central Peruvian Andes, and corroborate the sensitivity of lake sediments to pre-Colonial metallurgical activity suggested by earlier findings from Bolivia.

Quantified sensitivity of lakes to record historic earthquakes: Implications for paleoseismology

NASA Astrophysics Data System (ADS)

Wilhelm, Bruno; Nomade, Jerome; Crouzet, Christian; Litty, Camille; Belle, Simon; Rolland, Yann; Revel, Marie; Courboulex, Françoise; Arnaud, Fabien; Anselmetti, Flavio S.

2015-04-01

Seismic hazard assessment is a challenging issue for modern societies. A key parameter to be estimated is the recurrence interval of damaging earthquakes. In moderately active seismo-tectonic regions, this requires the establishment of earthquake records long enough to be relevant, i.e. far longer than historical observations. Here we investigate how lake sediments can be used for this purpose and quantify the conditions that enable earthquake recording. For this purpose, (i) we studied nine lake-sediment sequences to reconstruct mass-movement chronicles in different settings of the French Alpine range and (ii) we compared the chronicles to the well-documented earthquake history over the last five centuries. The studied lakes are all small alpine-type lakes based directly on bedrock. All lake sequences have been studied following the same methodology; (i) a multi-core approach to well understand the sedimentary processes within the lake basins, (ii) a high-resolution lithological and grain-size characterization and (iii) a dating based on short-lived radionuclide measurements, lead contaminations and radiocarbon ages. We identified 40 deposits related to 26 mass-movement (MM) occurrences. 46% (12 on 26) of the MMs are synchronous in neighbouring lakes, supporting strongly an earthquake origin. In addition, the good agreement between MMs ages and historical earthquake dates suggests an earthquake trigger for 88% (23 on 26) of them. Related epicenters are always located at distances of less than 100 km from the lakes and their epicentral MSK intensity ranges between VII and IX. However, the number of earthquake-triggered MMs varies between lakes of a same region, suggesting a gradual sensitivity of the lake sequences towards earthquake shaking, i.e. distinct lake-sediment slope stabilities. The quantification of this earthquake sensitivity and the comparison to the lake system and sediment characteristics suggest that the primary factor explaining this variability is

Sedimentological and geochemical characteristic of varved lake sediment of the Lake Jelonek (North Poland)

NASA Astrophysics Data System (ADS)

Kramkowski, M. A.; Filbrandt-Czaja, A.; Ott, F.; Slowinski, M. M.; Tjallingii, R.; Błaszkiewicz, M.; Brauer, A.

2016-12-01

Lake Jelonek is located in Northern Poland. The lake covers an area of 19,9 ha and has a maximum depth of 13,8 m. Three overlapping series of 14,3 m - long sediment records have been cored with an UWITEC 90 mm diameter piston corer from the deepest part of the lake. The cores were split in half, lithologically described, photographed and correlated with each other by 28 marker layers to construct a composite profile covering 1426cm. Here we present detailed varve micro-facies for different sediment intervals and the preliminary chronology based on AMS 14C dating of 10 terrestrial macro remains samples and the Askja AD-1875 tephra. Here we present initial results from thin section analyses for two intervals. First (I) the uppermost 0-256 cm and second (II) the interval from 768-1296 cm. Intercalated between these two varved interval is a thick section (512 cm) of homogeneous organic-ditomaceous sediments. We present varve micro-facies data in combination with µ-XRF element scanning for comprehensive reconstruction of the sedimentation processes in Lake Jelonek. Varve counting reveals that the lower floating varve interval covers the time period from 1850 - 10500 cal a BP, while the uppermost 256 cm varved sediments comprise ca 925 years (2008-1083 AD). The main goal is to synchronize the sediment record from Lake Jelonek with European and Worldly records, to achieve a comprehensive knowledge of landscape forming processes and to distinguish between local, regional and global impacts during the past. This study is a contribution to the Virtual Institute of Integrated Climate and Landscape Evolution Analysis -ICLEA- of the Helmholtz Association; grant number VH-VI-415, National Science Centre, Poland grant 2015/19/N/ST10/02655 and from the Science and Research Funds for 2015-2016 allocated to a co-financed international project, CONTRACT No. 3500/ICLEA/15/2016/0.

A Latest Glacial and Holocene Record From Medicine Lake, Siskiyou County, California: Preliminary Diatom, Pollen, and Sediment Data

NASA Astrophysics Data System (ADS)

Starratt, S. W.; Barron, J. A.; Kneeshaw, T.; Phillips, L.; Lowenstern, J.; Wanket, J. A.

2002-12-01

Medicine Lake is a small (165 ha), relatively shallow (average 7.3 m), medium- altitude (2,036 m) lake located within the summit caldera of Medicine Lake volcano, a dormant Quaternary shield volcano located in the southern Cascade Range. During September 1999 and 2000, high-resolution bathymetry, seismic-reflection profiles, and sediment cores were collected from the lake. Twenty six samples from core B100NC-1 (water depth 12.6 m; length 226 cm) were analyzed for physical properties, sediment grain size, diatoms, pollen, and total organic carbon (TOC). Using both 14C (AMS) dating and tephrochronology, the sediments at the bottom of the core are estimated to be 11,000 cal yr B.P., thus yielding an estimated average sedimentation rate of about 21 cm/1,000 yr. The lowermost part of the core (226 cm - ~200 cm) records the transition from glacial to interglacial conditions. During the period from about 11,000-7,200 cal yr B.P., lake level fluctuated between deeper oligotrophic conditions with a diatom flora dominated by Cyclotella spp. and shallower intervals with a diverse benthic flora. The relative low abundance (10-15%) of Abies (fir) pollen and relative high abundance (30-40%) of Artemesia (sagebrush) pollen in this interval suggest drier than present-day conditions. The lowest part of this interval (226 cm - 210 cm) is almost devoid of Cyclotella and may represent an ice-covered lake in which only a small benthic flora could exist around the margins of the lake where light penetration was the greatest. The sediments in this interval are relatively low in TOC and are dominated by glacial flour. From about 7,200 cal yr B.P. to the present, conditions have fluctuated between higher lake levels (three intervals) that are dominated by Cyclotella with a reduced number and diversity of benthic taxa, and lower lake levels (two intervals) during which the abundances of Cyclotella decrease to less than 10%. Relative values of Abies and Pinus (pine) pollen are higher during

Protocol to Reconstruct Historical Contaminant Loading to Large Lakes: The Lake Michigan Sediment Record of Mercury

EPA Science Inventory

Samples of opportunity from Pb-210 dated sediment cores collected from Lake Michigan between 1994 and 1996 were analyzed for mercury. The storage of both anthropogenic and total (post-1850) mercury in the lake was calculated to be 186 and 228 metric tons, respectively. By setti...

A Tibetan lake sediment record of Holocene Indian summer monsoon variability

NASA Astrophysics Data System (ADS)

Bird, Broxton W.; Polisar, Pratigya J.; Lei, Yanbin; Thompson, Lonnie G.; Yao, Tandong; Finney, Bruce P.; Bain, Daniel J.; Pompeani, David P.; Steinman, Byron A.

2014-08-01

Sedimentological data and hydrogen isotopic measurements of leaf wax long-chain n-alkanes (δDwax) from an alpine lake sediment archive on the southeastern Tibetan Plateau (Paru Co) provide a Holocene perspective of Indian summer monsoon (ISM) activity. The sedimentological data reflect variations in lake level and erosion related to local ISM rainfall over the Paru Co catchment, whereas δDwax reflects integrated, synoptic-scale ISM dynamics. Our results indicate that maximum ISM rainfall occurred between 10.1 and ˜5.2 ka, during which time there were five century-scale high and low lake stands. After 5.2 ka, the ISM trended toward drier conditions to the present, with the exception of a pluvial event centered at 0.9 ka. The Paru Co results share similarities with paleoclimate records from across the Tibetan Plateau, suggesting millennial-scale ISM dynamics were expressed coherently. These millennial variations largely track gradual decreases in orbital insolation, the southward migration of the Intertropical Convergence Zone (ITCZ), decreasing zonal Pacific sea surface temperature (SST) gradients and cooling surface air temperatures on the Tibetan Plateau. Centennial ISM and lake-level variability at Paru Co closely track reconstructed surface air temperatures on the Tibetan Plateau, but may also reflect Indian Ocean Dipole events, particularly during the early Holocene when ENSO variability was attenuated. Variations in the latitude of the ITCZ during the early and late Holocene also appear to have exerted an influence on centennial ISM rainfall.

Evidence for Isostatic Emergence and Holocene Environmental Change Recorded in Chironomid Assemblages and Sediment Composition of Coastal Lake T1 in SW Greenland

NASA Astrophysics Data System (ADS)

Berman, K.; Axford, Y.; Lasher, G. E.

2017-12-01

Multi-proxy analysis of a coastal lake in southwest Greenland near Nuuk provides evidence for regional environmental changes, including the timing of isostatic rebound and the temperature history of the area. T1 (informal name) is a small lake 50 km south of Nuuk, at 17.5 m elevation and currently isolated from glacial meltwater drainage. The lake's sediment record begins approximately 9500 cal years BP, when the site was submerged beneath sea level due to glacial isostatic depression following the Last Glacial Maximum. The record captures the transition of the environment from a submerged, glacially-influenced marine site to a non-glacially fed (and initially meromictic) freshwater lake 8600 cal years BP. Magnetic susceptibility, a proxy for sediment minerogenic content, decreased rapidly from 9500 to 8600 years BP, before abruptly stabilizing and remaining relatively low and steady for the rest of the record. The transition to a lacustrine environment was characterized by a rapid and relatively simultaneous increase in primary productivity (inferred from biogenic silica concentrations) and shift towards terrestrial versus marine sources of organic matter (inferred from carbon:nitrogen ratios and nitrogen isotopes) between 8700 and 8400 years BP. Together, these proxies and the presence of marine shells below the transition provide robust evidence for the transition from a marine environment to a freshwater lake in response to regional postglacial isostatic rebound. Within the Holocene, measures of bulk sediment composition (e.g., biogenic silica, loss-on-ignition and magnetic susceptibility) are relatively stable. Chironomid (Insecta: Diptera: Chironomidae) assemblages, which in some environments are quantitative proxies for summer temperature changes, show species-level shifts within the Holocene that will be interpreted in this presentation alongside indicators of landscape change including carbon:nitrogen ratios, bulk sediment spectral reflectance and bulk

Quaternary magnetic excursions recorded in marine sediments.

NASA Astrophysics Data System (ADS)

Channell, J. E. T.

2017-12-01

This year is the golden (50th) anniversary of the first documentation of a magnetic excursion, the Laschamp excursion in volcanics from the Chaine des Puys (Bonhommet and Babkine, 1967). The first recording of an excursion in sediments was from the Blake Outer Ridge (Smith and Foster, 1969). Magnetic excursions are directional aberrations of the geomagnetic field apparently involving short-lived reversal of the main dipole field. They have durations of a few kyrs, and are therefore rarely recorded in sediments with mean sedimentation rates <10 cm/kyr. Certain Brunhes-aged excursions are now well documented having been recorded in both marine sediments and in lavas (Laschamp excursion, 41 ka). Other excursions have not been adequately recorded in lavas, but have been widely recorded in marine and lake sediments (Iceland Basin excursion, 190 ka). The recording of excursions is fortuitous both in lava sequences and in marine sediments due to their millennial/centennial-scale duration, however, the global recording of the Laschamp and Iceland Basin excursions imply that excursions involve the main dipole field, are recorded synchronously over the globe, and are therefore important in stratigraphic correlation. The marine sediment record includes magnetic excursions at 26 ka (Rockall), 32 ka (Mono Lake), 41 ka (Laschamp), 115 ka (Blake), 190 ka (Iceland Basin), 238 ka (Pringle Falls?), 286 ka (Portuguese Orphan), 495 ka (Bermuda), 540 ka (Big Lost), 590 ka (La Palma), and 670 ka (Osaka Bay), implying at least 11 excursions in the Brunhes Chron. For the Matuyama Chron, excursions have been recorded in marine sediments at 868 ka (Kamikatsura?), 932 ka (Santa Rosa), 1051 ka (Intra-Jaramillo), 1115 ka (Punaruu), 1255 ka (Bjorn), 1476 ka (Gardar), 1580 ka (Gilsa), and 2737 ka (Porcupine). Excursions coincide with minima in relative paleointensity (RPI) records. Ages are from correlation of excursion records to oxygen isotope records in the same cores, and ice

Lake-sediment evidence for the date of deglaciation of the Hidden Lake area, Kenai Peninsula, Alaska

NASA Astrophysics Data System (ADS)

Rymer, Michael J.; Sims, John D.

1982-06-01

An abrupt environmental change is reflected in a core from Hidden Lake, Alaska, by differences in sediment type, chlorite crystallinity, and content of organic carbon and water of the sediments. This abrupt change in the sedimentary record occurred about 14,500 14C yr ago and probably marks the time of recession of the glacier from the Hidden Lake drainage basin. Deglaciation of the area was then underway, and rock flour was being deposited in the lake. After recession of the glacier from the Hidden Lake drainage basin, rock flour was no longer introduced, and organic-matter content of the sediment increased. By the dating of these changes in sediment type, we show that retreat of glaciers in this area took place significantly earlier than previously estimated; this agrees with the timing of retreat of alpine glaciers elsewhere in western North America.

Search for continuous paleoclimatic record in Holocene lacustrine sediments from Lake District, Chile (40°S)

NASA Astrophysics Data System (ADS)

Bertrand, S.; Fagel, N.

2003-04-01

Our aim is to reconstruct a continuous Holocene climatic evolution related to ENSO variability in southern Chile. We focus on the sedimentary infilling of two glacial lakes from the Lake District Area (38-40°S). The preliminar sedimentological analysis must allow to define the key-site and the best palaeoclimatic proxies. This area, at the foothill of the Cordillera de Los Andes, has been affected by an intense Quaternary volcanic activity and by several historical earthquakes (e.g., Valdivia 1960). After preliminary seismic investigation, four cores were recovered in two lakes selected at the two ends of a N-S transect. (1) Icalma lake (12 km2, 38°S) is located in the Cordillera de Los Andes at an elevation of 1150m and results of the infilling of a glacial umbilic. The two 8m sediment cores consist of an alternation of laminated silts and volcanic layers. The sedimentary record is strongly disturbed by numerous seismic or volcanic events. The cumulated volcanogenic-derived material represents up to 50 % of the core length. In particular, the cores record at -4.50m a pumice layer widespread in the watershed and dated at 2900 yr BP. One core contains pluricentrimetric layers of wood accumulation. They could be due to earthquake impact on the vegetational cover in the watershed. An ubiquitous 6cm-thick slump described at -40 cm may be related with the 1960 Valdivia earthquake. (2) On Puyehue lake (164 km2, 40°S, elevation 185 m), two cores (7 and 11m) have been collected in both underflow and interflow sites. The interflow site (PUII) shows a very well laminated sediment, with only small disturbances due to volcanic and seismic activities. This core will be the key-site for the paleoclimatic study. The second core (PUI) is very rich in organic matter. The sediment is strongly destratified by numerous gas bubbles (methane). These characteristics are due to the dense vegetational cover in the watershed and to the core location near the delta of the main river. This

A model-based approach to wildland fire reconstruction using sediment charcoal records

USGS Publications Warehouse

Itter, Malcolm S.; Finley, Andrew O.; Hooten, Mevin B.; Higuera, Philip E.; Marlon, Jennifer R.; Kelly, Ryan; McLachlan, Jason S.

2017-01-01

Lake sediment charcoal records are used in paleoecological analyses to reconstruct fire history, including the identification of past wildland fires. One challenge of applying sediment charcoal records to infer fire history is the separation of charcoal associated with local fire occurrence and charcoal originating from regional fire activity. Despite a variety of methods to identify local fires from sediment charcoal records, an integrated statistical framework for fire reconstruction is lacking. We develop a Bayesian point process model to estimate the probability of fire associated with charcoal counts from individual-lake sediments and estimate mean fire return intervals. A multivariate extension of the model combines records from multiple lakes to reduce uncertainty in local fire identification and estimate a regional mean fire return interval. The univariate and multivariate models are applied to 13 lakes in the Yukon Flats region of Alaska. Both models resulted in similar mean fire return intervals (100–350 years) with reduced uncertainty under the multivariate model due to improved estimation of regional charcoal deposition. The point process model offers an integrated statistical framework for paleofire reconstruction and extends existing methods to infer regional fire history from multiple lake records with uncertainty following directly from posterior distributions.

Influence of geomorphic setting on sedimentation of two adjacent alpine lakes, Triglav Lakes Valley (Julian Alps, NW Slovenia)

NASA Astrophysics Data System (ADS)

Smuc, Andrej; Skabene, Dragomir; Muri, Gregor; Vreča, Polona; Jaćimović, Radojko; Čermelj, Branko; Turšič, Janja

2013-04-01

The Triglav Lakes Valley is elongated, 7km long depression, located high (at places over 2000 m.a.s.l.) in the central part of the Julian Alps (NW Slovenia). It hosts 6 small isolated lakes that formed due to the combination of Neogene tectonic and Pleistocene glaciation. The study is focused on the 5th and 6th Triglav Valley Lakes that characterize lower part of the valley. The lakes are located so close to each other that they are even connected in times of high water. Thus, they share the same bedrock geology, are subjected to the same climatic forcing and share similar vegetation communities. Despite their proximity, the lakes differ in their hydrologic and geomorphic setting. The lakes have no permanent surface tributaries; however 5th is fed periodically, at times of high water level, by the Močivec spring, while additional water flows from the swamp area near its northern shore. An underground spring on the eastern side of 5th represents the lake's only permanent freshwater inflow, while drainage takes place to the west via a small ponor. 6th has only one weak underground spring on the eastern side of the lake. Water levels may fluctuate between 2 and 3 m. Additionally, the lakes have different configuration of lakes shores; the northern shores of the 5th lake are low-angle soil and debris covered plateau, while southern shores of the 5th lake and shores of the 6th lake are represented by heavily karstified carbonate base rock and covered partly by trees. The detailed sedimentary analysis of the lakes record showed some similarities, but also some significant differences. Sediments of both lakes are represented by fine-grained turbidity current deposits that are transported from lake shores during snow melt or storms. The grain-size and sedimentary rates of the lakes are however markedly different. The 5th lake has coarser grained sediments, with mean ranging from 46 to 60 µm and records higher sedimentation rates of ~0,57 cm/year, compared to the 6th lake

The Record of Geomagnetic Excursions from a ~150 m Sediment Core: Clear Lake, Northern California

NASA Astrophysics Data System (ADS)

Levin, E.; Byrne, R.; Looy, C. V.; Wahl, D.; Noren, A. J.; Verosub, K. L.

2015-12-01

We are studying the paleomagnetic properties of a new ~150 meter drill core from Clear Lake, CA. Step-wise demagnetization of the natural remanent magnetism (NRM) yields stable directions after 20 mT, implying that the sediments are reliable recorders of geomagnetic field behavior. Several intervals of low relative paleointensity (RPI) from the core appear to be correlated with known geomagnetic excursions. At about 46 m depth, and ~33 ka according to an age model based on radiocarbon dates obtained from pollen and the Olema ash bed, a low RPI zone seems to agree with the age and duration of the Mono Lake Excursion, previously identified between 32 and 35 ka. Slightly lower in the core, at about 50 m depth and ~40 ka, noticeably low RPI values seem to be coeval with the Laschamp excursion, which has been dated at ~41 ka. A volcanic ash near the bottom of the core (141 mblf) is near the same depth as an ash identified in 1988 by Andrei Sarna-Wojcicki and others as the Loleta ash bed in a previous Clear Lake core. If the basal ash in the new core is indeed the, Loleta ash bed, then the core may date back to about 270-300 ka. Depending on the age of the lowest ash, a sequence of low RPI intervals could correlate with the Blake (120 ka), Iceland Basin (188 ka), Jamaica/Pringle Falls (211 ka), and CR0 (260 ka) excursions. Correlation of the low RPI intervals to these geomagnetic excursions will help in the development of a higher resolution chronostratigraphy for the core, resolve a long-standing controversy about a possible hiatus in the Clear Lake record, and provide information about climatically-driven changes in sedimentation.

Lumped parameter, isotopic model simulations of closed-basin lake response to drought in the Pacific Northwest and implications for lake sediment oxygen isotope records.

NASA Astrophysics Data System (ADS)

Steinman, B. A.; Rosenmeier, M.; Abbott, M.

2008-12-01

The economy of the Pacific Northwest relies heavily on water resources from the drought-prone Columbia River and its tributaries, as well as the many lakes and reservoirs of the region. Proper management of these water resources requires a thorough understanding of local drought histories that extends well beyond the instrumental record of the twentieth century, a time frame too short to capture the full range of drought variability in the Pacific Northwest. Here we present a lumped parameter, mass-balance model that provides insight into the influence of hydroclimatological changes on two small, closed-basin systems located in north- central Washington. Steady state model simulations of lake water oxygen isotope ratios using modern climate and catchment parameter datasets demonstrate a strong sensitivity to both the amount and timing of precipitation, and to changes in summertime relative humidity, particularly at annual and decadal time scales. Model tests also suggest that basin hypsography can have a significant impact on lake water oxygen isotope variations, largely through surface area to volume and consequent evaporative flux to volume ratio changes in response to drought and pluvial sequences. Additional simulations using input parameters derived from both on-site and National Climatic Data Center historical climate datasets accurately approximate three years of continuous lake observations (seasonal water sampling and continuous lake level monitoring) and twentieth century oxygen isotope ratios in sediment core authigenic carbonate recovered from the lakes. Results from these model simulations suggest that small, closed-basin lakes in north-central Washington are highly sensitive to changes in the drought-related climate variables, and that long (8000 year), high resolution records of quantitative changes in precipitation and evaporation are obtainable from sediment cores recovered from water bodies of the Pacific Northwest.

Lake-level history of Lake Michigan for the past 12,000 years: the record from deep lacustrine sediments

USGS Publications Warehouse

Colman, Steven M.; Forester, Richard M.; Reynolds, Richard L.; Sweetkind, Donald S.; King, John W.; Gangemi, Paul; Jones, Glenn A.; Keigwin, Loyd D.; Foster, David S.

1994-01-01

Collection and analysis of an extensive set of seismic-reflection profiles and cores from southern Lake Michigan have provided new data that document the history of the lake basin for the past 12,000 years. Analyses of the seismic data, together with radiocarbon dating, magnetic, sedimentologic, isotopic, and paleontologic studies of core samples, have allowed us to reconstruct lake-level changes during this recent part of the lake's history.The post-glacial history of lake-level changes in the Lake Michigan basin begins about 11.2 ka with the fall from the high Calumet level, caused by the retreat of the Two Rivers glacier, which had blocked the northern outlet of the lake. This lake-level fall was temporarily reversed by a major influx of water from glacial Lake Agassiz (about 10.6 ka), during which deposition of the distinctive gray Wilmette Bed of the Lake Michigan Formation interrupted deposition of red glaciolacustrine sediment. Lake level then continued to fall, culminating in the opening of the North Bay outlet at about 10.3 ka. During the resulting Chippewa low phase, lake level was about 80 m lower than it is today in the southern basin of Lake Michigan.The rise of the early Holocene lake level, controlled primarily by isostatic rebound of the North Bay outlet, resulted in a prominent, planar, transgressive unconformity that eroded most of the shoreline features below present lake level. Superimposed on this overall rise in lake level, a second influx of water from Lake Agassiz temporarily raised lake levels an unknown amount about 9.1 ka. At about 7 ka, lake level may have fallen below the level of the outlet because of sharply drier climate. Sometime between 6 and 5 ka, the character of the lake changed dramatically, probably due mostly to climatic causes, becoming highly undersaturated with respect to calcium carbonate and returning primary control of lake level to the isostatically rising North Bay outlet. Post-Nipissing (about 5 ka) lake level has

Lake-sediment record of PAH, mercury, and fly-ash particle deposition near coal-fired power plants in Central Alberta, Canada.

PubMed

Barst, Benjamin D; Ahad, Jason M E; Rose, Neil L; Jautzy, Josué J; Drevnick, Paul E; Gammon, Paul R; Sanei, Hamed; Savard, Martine M

2017-12-01

We report a historical record of atmospheric deposition in dated sediment cores from Hasse Lake, ideally located near both currently and previously operational coal-fired power plants in Central Alberta, Canada. Accumulation rates of spheroidal carbonaceous particles (SCPs), an unambiguous marker of high-temperature fossil-fuel combustion, in the early part of the sediment record (pre-1955) compared well with historical emissions from one of North America's earliest coal-fired power plants (Rossdale) located ∼43 km to the east in the city of Edmonton. Accumulation rates in the latter part of the record (post-1955) suggested inputs from the Wabamun region's plants situated ∼17-25 km to the west. Increasing accumulation rates of SCPs, polycyclic aromatic hydrocarbons (PAHs) and Hg coincided with the previously documented period of peak pollution in the Wabamun region during the late 1960s to early 1970s, although Hg deposition trends were also similar to those found in western North American lakes not directly affected by point sources. A noticeable reduction in contaminant inputs during the 1970s is attributed in part to technological improvements and stricter emission controls. The over one hundred-year historical record of coal-fired power plant emissions documented in Hasse Lake sediments has provided insight into the impact that both environmental regulations and changes in electricity output have had over time. This information is crucial to assessing the current and future role of coal in the world's energy supply. Crown Copyright © 2017. Published by Elsevier Ltd. All rights reserved.

Record of late Pleistocene glaciation and deglaciation in the southern Cascade Range. I. Petrological evidence from lacustrine sediment in Upper Klamath Lake, southern Oregon

USGS Publications Warehouse

Reynolds, R.L.; Rosenbaum, J.G.; Rapp, J.; Kerwin, M.W.; Bradbury, J.P.; Colman, S.; Adam, D.

2004-01-01

Petrological and textural properties of lacustrine sediments from Upper Klamath Lake, Oregon, reflect changing input volumes of glacial flour and thus reveal a detailed glacial history for the southern Cascade Range between about 37 and 15 ka. Magnetic properties vary as a result of mixing different amounts of the highly magnetic, glacially generated detritus with less magnetic, more weathered detritus derived from unglaciated parts of the large catchment. Evidence that the magnetic properties record glacial flour input is based mainly on the strong correlation between bulk sediment particle size and parameters that measure the magnetite content and magnetic mineral freshness. High magnetization corresponds to relatively fine particle size and lower magnetization to coarser particle size. This relation is not found in the Buck Lake core in a nearby, unglaciated catchment. Angular silt-sized volcanic rock fragments containing unaltered magnetite dominate the magnetic fraction in the late Pleistocene sediments but are absent in younger, low magnetization sediments. The finer grained, highly magnetic sediments contain high proportions of planktic diatoms indicative of cold, oligotrophic limnic conditions. Sediment with lower magnetite content contains populations of diatoms indicative of warmer, eutrophic limnic conditions. During the latter part of oxygen isotope stage 3 (about 37-25 ka), the magnetic properties record millennial-scale variations in glacial-flour content. The input of glacial flour was uniformly high during the Last Glacial Maximum, between about 21 and 16 ka. At about 16 ka, magnetite input, both absolute and relative to hematite, decreased abruptly, reflecting a rapid decline in glacially derived detritus. The decrease in magnetite transport into the lake preceded declines in pollen from both grass and sagebrush. A more gradual decrease in heavy mineral content over this interval records sediment starvation with the growth of marshes at the margins

Regional environmental change and human activity over the past hundred years recorded in the sedimentary record of Lake Qinghai, China.

PubMed

Sha, ZhanJiang; Wang, Qiugui; Wang, Jinlong; Du, Jinzhou; Hu, Jufang; Ma, Yujun; Kong, Fancui; Wang, Zhuan

2017-04-01

Environmental change and human activity can be recorded in sediment cores in aquatic systems such as lakes. Information from such records may be useful for environmental governance in the future. Six sediment cores were collected from Lake Qinghai, China and its sublakes during 2012 and 2013. Measurements of sediment grain-size fractions indicate that sedimentation in the north and southwest of Lake Qinghai is dominated by river input, whereas that in Lake Gahai and Lake Erhai is dominated by dunes. The sedimentation rates in Lake Qinghai were calculated to be 0.101-0.159 cm/y, similar to the rates in other lakes on the Qinghai-Tibetan Plateau. Using these data and sedimentation rates from the literature, we compiled the spatial distribution of sedimentation rates. Higher values were obtained in the three main areas of Lake Qinghai: two in river estuaries and one close to sand dunes. Lower values were measured in the center and south of the lake. Measurements of total organic carbon (TOC), total nitrogen (TN), phosphorus concentrations, and TOC/TN ratios in three cores (QH01, QH02, and Z04) revealed four horizons corresponding to times of increased human activity. These anthropogenic events were (1) the development of large areas of cropland in the Lake Qinghai watershed in 1960, (2) the beginning of nationwide fertilizer use and increases in cropland area in the lake watershed after 1970, (3) the implementation of the national program "Grain to Green," and (4) the rapid increase in the tourism industry from 2000. Profiles of Rb, Sr concentrations, the Rb/Sr ratio, and grain-size fraction in core Z04 indicate that the climate has become drier over the past 100 years. Therefore, we suggest that lake sediments such as those in Lake Qinghai are useful media for high-resolution studies of regional environmental change and human activity.

Inputting history of heavy metals into the inland lake recorded in sediment profiles: Poyang Lake in China.

PubMed

Yuan, Guo-Li; Liu, Chen; Chen, Long; Yang, Zhongfang

2011-01-15

The temporal and spatial distribution of heavy metals (Cd, Hg, Pb, As and Cr) in Poyang Lake, the largest freshwater lake (3050 km(2)) in China, were studied based on the sedimentary profiles. For this purpose, eight sedimentary cores were selected which located at lake area, outfall of lake and the main branch rivers, respectively. High-resolution profiles with interval 2 cm were used for analyzing the concentration of metals, and the ages of them were determined by (210)Pb and (137)Cs isotopic dating. While studying the change of metals concentration with the age in profile, it is found that the concentration of them in sediments was influenced not only by the sources in history but also by the sediment types. Based on this detailed work, the inventory and burden of heavy metals per decade were estimated in lake area during the past 50 years. Significantly, rivers-contribution ratio per decade was estimated to distinguish each river's contribution of heavy metals into lake while river-flux in history and metals concentration in profiles were considered as calculating factors. So, our research provides a proof to well understand the sedimentary history and the inputting history of heavy metals from main rivers into an inland lake. Copyright © 2010 Elsevier B.V. All rights reserved.

Sediment Transforms Lake Michigan

NASA Image and Video Library

2011-01-11

NASA image acquired December 17, 2010 In mid-December 2010, suspended sediments transformed the southern end of Lake Michigan. Ranging in color from brown to green, the sediment filled the surface waters along the southern coastline and formed a long, curving tendril extending toward the middle of the lake. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite captured these natural-color images on December 17, 2010 (top), and December 10, 2010 (bottom). Such sediment clouds are not uncommon in Lake Michigan, where winds influence lake circulation patterns. A scientificpaper published in 2007 described a model of the circulation, noting that while the suspended particles mostly arise from lake-bottom sediments along the western shoreline, they tend to accumulate on the eastern side. When northerly winds blow, two circulation gyres, rotating in opposite directions, transport sediment along the southern shoreline. As the northerly winds die down, the counterclockwise gyre predominates, and the smaller, clockwise gyre dissipates. Clear water—an apparent remnant of the small clockwise gyre—continues to interrupt the sediment plume. George Leshkevich, a researcher with the U.S. National Oceanic and Atmospheric Administration, explains that the wind-driven gyres erode lacustrine clay (very fine lakebed sediment) on the western shore before transporting it, along with re-suspended lake sediments, to the eastern shore. On the eastern side, the gyre encounters a shoreline bulge that pushes it toward the lake’s central southern basin, where it deposits the sediments. The sediment plume on December 17 followed a windy weather front in the region on December 16. NASA image courtesy MODIS Rapid Response Team at NASA GSFC. Caption by Michon Scott. Instrument: Aqua - MODIS NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard

δ18O and Carbonate Clumped Isotopes as Proxies of Lake Level Change: Mono Lake Modern Sediments Inform Pleistocene Interpretations

NASA Astrophysics Data System (ADS)

Westacott, S.; Ingalls, M.; Meixnerova, J.; Betts, M.; Lloyd, M. K.; Miller, L. G.; Sessions, A. L.; Trower, L.; Geobiology Course, A.

2017-12-01

In 1941 LA County began diverting water from the Mono Lake basin, causing lake level to fall dramatically until 1994 when diversion was substantially discontinued. High sedimentation rate (0.7 cm/yr) in combination with rapid, well-documented environmental change offers a unique opportunity to investigate the isotopic fingerprint of lake level change at a much finer scale than is typically accessible in the geologic record. δ18Ocarb can record lake level in a closed-basin system, but relies on knowing the relative contributions from carbonate precipitated from lake water and from authigenic carbonates, both of which are expected to exist in alkaline lake sediments. Here, we combine δ18Ocarb with clumped isotope thermometry (T(Δ47)) on a 70 cm sediment core to "unmix" the carbonate sources and reconstruct δ18Owater of Mono Lake over the past 116 years. Carbonate from the upper 10 cm of the sediment core yields a T(Δ47) of 26°C, reflecting surface water carbonate precipitation during late summer. Carbonates from sediment depths greater than 10cm yield a consistent T(Δ47) of 9.6°C, warmer than today's bottom waters, suggesting dissolution and reprecipitation of originally "warm" carbonate deposited from the water column alongside "cold" water of a different δ18Ow than Mono Lake surface water. A clumped isotope mixing model (Defliese & Lohmann, 2015) used to calculate the relative contributions of the two carbonate precipitates, corroborated by mirrored shifts in δ13Corg and δ13Ccarb down-core, suggests that about half of the carbonate found in the lower 60 cm of the sediment core is authigenic. As an example of how this strategy can be applied to older strata with looser constraints on primary composition, we also analysed the Pleistocene Wilson Creek Formation—lake sediments from Mono Lake's predecessor, Lake Russell. Although Pleistocene Lake Russell should have been cooler than modern Mono Lake, T(Δ47) values were similar to those of modern sediments

A conduit dilation model of methane venting from lake sediments

USGS Publications Warehouse

Scandella, B.P.; Varadharajan, C.; Hemond, Harold F.; Ruppel, C.; Juanes, R.

2011-01-01

Methane is a potent greenhouse gas, but its effects on Earth's climate remain poorly constrained, in part due to uncertainties in global methane fluxes to the atmosphere. An important source of atmospheric methane is the methane generated in organic-rich sediments underlying surface water bodies, including lakes, wetlands, and the ocean. The fraction of the methane that reaches the atmosphere depends critically on the mode and spatiotemporal characteristics of free-gas venting from the underlying sediments. Here we propose that methane transport in lake sediments is controlled by dynamic conduits, which dilate and release gas as the falling hydrostatic pressure reduces the effective stress below the tensile strength of the sediments. We test our model against a four-month record of hydrostatic load and methane flux in Upper Mystic Lake, Mass., USA, and show that it captures the complex episodicity of methane ebullition. Our quantitative conceptualization opens the door to integrated modeling of methane transport to constrain global methane release from lakes and other shallow-water, organic-rich sediment systems, and to assess its climate feedbacks.

Natural Environmental Hazards Reflected in High-Altitude Patagonian Lake Sediments (lake Caviahue, Argentina)

NASA Astrophysics Data System (ADS)

Müller, Anne; Scharf, Burkhard; von Tümpling, Wolf; Pirrung, Michael

2009-03-01

Two 6-m long sediment cores drilled in the two basins of Lake Caviahue give new evidence of the impact of natural hazards such as ash fallouts linked to nearby volcanic eruptions in the ecologically sensitive environment of the high-altitude region of the Argentinan Patagonian Andes. The two cores show distinct signals of changes in autochthonous productivity and terrigenous input into the lake from ash fallout as well as from river load and shore erosion. Multiproxy records of the sediments indicate whether these changes can be related to volcanic activity. High values of magnetic susceptibility in the cores reflect periods of basaltic ash fallouts during eruptions of the nearby Copahue Volcano. The southern basin is located in the prevalent direction of ash fallouts and has been affected by these volcanic inputs more intensely than the northern basin of the lake. In contrast, sedimentation and authochthonous productivity in the northern basin are strongly affected by fluvial inputs such as suspended river load and acidic stream waters.

Natural Environmental Hazards Reflected in High-Altitude Patagonian Lake Sediments (Lake Caviahue, Argentina)

NASA Astrophysics Data System (ADS)

Mueller, A.; Pirrung, M.; Scharf, B.; von Tuempling, W.

2007-05-01

Two 6-m long sediment cores drilled in the two basins of Lake Caviahue give new evidence of the impact of natural hazards such as ash fallouts linked to nearby volcanic eruptions in the ecologically sensitive environment of the high-altitude region of the Argentinan Patagonian Andes. The two cores show distinct signals of changes in autochthonous productivity and terrigenous input into the lake from ash fallout, river load and shore erosion. Multiproxy records of the sediments indicate whether these changes can be related to volcanic activity. High values of magnetic susceptibility in the cores reflect periods of basaltic ash fallouts during eruptions of the nearby Copahue volcano. The southern basin is located in the prevalent direction of ash fallouts and has been affected by these volcanic inputs more intensely than the northern basin of the lake. In contrast, sedimentation and authochthonous productivity in the northern basin are strongly affected by fluvial inputs such as suspended river load and acidic stream waters.

Bioturbation enhances the aerobic respiration of lake sediments in warming lakes.

PubMed

Baranov, Viktor; Lewandowski, Jörg; Krause, Stefan

2016-08-01

While lakes occupy less than 2% of the total surface of the Earth, they play a substantial role in global biogeochemical cycles. For instance, shallow lakes are important sites of carbon metabolism. Aerobic respiration is one of the important drivers of the carbon metabolism in lakes. In this context, bioturbation impacts of benthic animals (biological reworking of sediment matrix and ventilation of the sediment) on sediment aerobic respiration have previously been underestimated. Biological activity is likely to change over the course of a year due to seasonal changes of water temperatures. This study uses microcosm experiments to investigate how the impact of bioturbation (by Diptera, Chironomidae larvae) on lake sediment respiration changes when temperatures increase. While at 5°C, respiration in sediments with and without chironomids did not differ, at 30°C sediment respiration in microcosms with 2000 chironomids per m(2) was 4.9 times higher than in uninhabited sediments. Our results indicate that lake water temperature increases could significantly enhance lake sediment respiration, which allows us to better understand seasonal changes in lake respiration and carbon metabolism as well as the potential impacts of global warming. © 2016 The Authors.

Bioturbation enhances the aerobic respiration of lake sediments in warming lakes

PubMed Central

Krause, Stefan

2016-01-01

While lakes occupy less than 2% of the total surface of the Earth, they play a substantial role in global biogeochemical cycles. For instance, shallow lakes are important sites of carbon metabolism. Aerobic respiration is one of the important drivers of the carbon metabolism in lakes. In this context, bioturbation impacts of benthic animals (biological reworking of sediment matrix and ventilation of the sediment) on sediment aerobic respiration have previously been underestimated. Biological activity is likely to change over the course of a year due to seasonal changes of water temperatures. This study uses microcosm experiments to investigate how the impact of bioturbation (by Diptera, Chironomidae larvae) on lake sediment respiration changes when temperatures increase. While at 5°C, respiration in sediments with and without chironomids did not differ, at 30°C sediment respiration in microcosms with 2000 chironomids per m2 was 4.9 times higher than in uninhabited sediments. Our results indicate that lake water temperature increases could significantly enhance lake sediment respiration, which allows us to better understand seasonal changes in lake respiration and carbon metabolism as well as the potential impacts of global warming. PMID:27484649

A New Method for the Determination of Annual Sediment Fluxes from Varved Lake Sediments

NASA Astrophysics Data System (ADS)

Francus, P.; Massa, C.; Lapointe, F.

2013-12-01

located directly downstream of the Agassiz ice cap and contains laminated sediments whose accumulation is directly related to hydrological inputs generated by the melting of the ice cap. Over the last 65 years, annual sediment accumulation rates in Strathcona Lake documented an increase in high-energy hydrologic discharge events from 1990 to 2009. This timing is in agreement with evidence for an increase in the amount of melt on the adjacent Agassiz Ice Cap, as recorded in ice cores. A good correspondence was also found between annual mass accumulation rates and Eureka air temperature records, suggesting that temperature changes affected the extent of summer melting on the Agassiz Ice Cap, leading to high sediment yield to Strathcona Lake. Ojala, A.E.K., Francus, P., Zolitschka, B., Besonen, M. and Lamoureux, S.F. (2012) Characteristics of sedimentary varve chronologies - A review. Quaternary Science Reviews, 43, 45-60.

MANAGEMENT OF LAKES THROUGH SEDIMENT REMOVAL

EPA Science Inventory

When properly conducted, sediment removal is an effective lake management technique. This paper describes: (1) the purpose of sediment removal, (2) environmental concerns, (3) depth of sediment removal, (4) sediment removal techniques, (5) suitable lake conditions, (6) exemplary ...

Eruptive and environmental processes recorded by diatoms in volcanically-dispersed lake sediments from the Taupo Volcanic Zone, New Zealand

USGS Publications Warehouse

Harper, Margaret A.; Pledger, Shirley A.; Smith, Euan G. C.; Van Eaton, Alexa; Wilson, Colin J. N.

2015-01-01

Late Pleistocene diatomaceous sediment was widely dispersed along with volcanic ash (tephra) across and beyond New Zealand by the 25.4 ka Oruanui supereruption from Taupo volcano. We present a detailed analysis of the diatom populations in the Oruanui tephra and the newly discovered floras in two other eruptions from the same volcano: the 28.6 ka Okaia and 1.8 ka Taupo eruptions. For comparison, the diatoms were also examined in Late Pleistocene and Holocene lake sediments from the Taupo Volcanic Zone (TVZ). Our study demonstrates how these microfossils provide insights into the lake history of the TVZ since the Last Glacial Maximum. Morphometric analysis of Aulacoseira valve dimensions provides a useful quantitative tool to distinguish environmental and eruptive processes within and between individual tephras. The Oruanui and Okaia diatom species and valve dimensions are highly consistent with a shared volcanic source, paleolake and eruption style (involving large-scale magma-water interaction). They are distinct from lacustrine sediments sourced elsewhere in the TVZ. Correspondence analysis shows that small, intact samples of erupted lake sediment (i.e., lithic clasts in ignimbrite) contain heterogeneous diatom populations, reflecting local variability in species composition of the paleolake and its shallowly-buried sediments. Our analysis also shows a dramatic post-Oruanui supereruption decline in Cyclostephanos novaezelandiae, which likely reflects a combination of (1) reorganisation of the watershed in the aftermath of the eruption, and (2) overall climate warming following the Last Glacial Maximum. This decline is reflected in substantially lower proportions of C. novaezelandiae in the 1.8 ka Taupo eruption deposits, and even fewer in post-1.8 ka sediments from modern (Holocene) Lake Taupo. Our analysis highlights how the excellent preservation of siliceous microfossils in volcanic tephra may fingerprint the volcanic source region and retain a valuable record

Active hematite concretion formation in modern acid saline lake sediments, Lake Brown, Western Australia

NASA Astrophysics Data System (ADS)

Bowen, Brenda Beitler; Benison, K. C.; Oboh-Ikuenobe, F. E.; Story, S.; Mormile, M. R.

2008-04-01

Concretions can provide valuable records of diagenesis and fluid-sediment interactions, however, reconstruction of ancient concretion-forming conditions can be difficult. Observation of modern hematite concretion growth in a natural sedimentary setting provides a rare glimpse of conditions at the time of formation. Spheroidal hematite-cemented concretions are actively precipitating in shallow subsurface sediments at Lake Brown in Western Australia. Lake Brown is a hypersaline (total dissolved solids up to 23%) and acidic (pH ˜ 4) ephemeral lake. The concretion host sediments were deposited between ˜ 1 and 3 ka, based on dating of stratigraphically higher and lower beds. These age constraints indicate that the diagenetic concretions formed < 3 ka, and field observations suggest that some are currently forming. These modern concretions from Lake Brown provide an example of very early diagenetic formation in acid and saline conditions that may be analogous to past conditions on Mars. Previously, the hematite concretions in the Burns formation on Mars have been interpreted as late stage diagenetic products, requiring long geologic time scales and multiple fluid flow events to form. In contrast, the Lake Brown concretions support the possibility of similar syndepositional to very early diagenetic concretion precipitation on Mars.

Ecosystem responses during Late Glacial period recorded in the sediments of Lake Łukie (East Poland)

NASA Astrophysics Data System (ADS)

Zawiska, Izabela; Słowiński, Michał; Correa-Metrio, Alex; Obremska, Milena; Luoto, Tomi; Nevalainen, Liisa; Woszczyk, Michał; Milecka, Krystyna

2014-05-01

The main objectives of this study was to reconstruct climate impact on the functioning of Lake Łukie and its catchment (Łęczna Włodawa Lake District, East European Plain) during Late Glacial period. In order to reconstruct climatic fluctuations and corresponding ecosystem responses, we analysed lake sediments for pollen, subfossil Cladocera, plant macrofossils and chemical composition of the sediment. Of these, plant macrofossils and Cladocera were used to infer minimum and mean July temperatures and ordination analysis was used to examine biotic community shifts. Multiproxy analyses of late-glacial sediments of Lake Łukie clearly show that the main driver of aquatic and terrestrial ecosystems as well as geomorphological processes in the catchment was climate variation. The history of the lake initiated during the Older Dryas. In that period, Łęczna Włodawa Lake District was covered by open habitats dominated by grasses (Poaceae), humid sites were occupied by tundra plant communities with less clubmoss (Selaginella selaginoides), dry sites by dominated by steppe-like vegetation with light-demanding species such as Helianthemum, Artemisia, Chenopodiaceae, and juniper bushes (Juniperus). Cold climate limited the growth and development of organisms in the lake, Cladocera community species composition was poor, with only few species present there all the time. During this time period, permafrost was still present in the ground limiting infiltration of rainwater and causing high erosion in the catchment area. Surface runoff is confirmed by the presence of sclerotia of Cenococcum geophilum and high terrigenous silica content. The warming of the early Allerød caused a remarkable change in the natural environment of this area. This is in accordance with the temperature rise reconstructed with the use of plant macrofossils though the Cladocera reconstruction did not recorded the rise than. This temperature increase resulted in turnover of vegetation in the

Continuous lake-sediment records of glaciation in the Sierra Nevada between 52,600 and 12,500 14C yr B.P.

USGS Publications Warehouse

Benson, L.V.; May, Howard M.; Antweiler, Ronald C.; Brinton, T.I.; Kashgarian, Michaele; Smoot, J.P.; Lund, S.P.

1998-01-01

The chemistry of the carbonate-free clay-size fraction of Owens Lake sediments supports the use of total organic carbon and magnetic susceptibility as indicators of stadial-interstadial oscillations. Owens Lake records of total organic carbon, magnetic susceptibility, and chemical composition of the carbonate-free, clay-size fraction indicate that Tioga glaciation began ~24,500 and ended by ~13,600 14C yr B.P. Many of the components of glacial rock flour (e.g., TiO2, MnO, BaO) found in Owens Lake sediments achieved maximum values during the Tioga glaciation when valley glaciers reached their greatest extent. Total organic carbon and SiO2 (amorphous) concentrations reached minimum values during Tioga glaciation, resulting from decreases in productivity that accompanied the introduction of rock flour into the surface waters of Owens Lake. At least 20 stadial-interstadial oscillations occurred in the Sierra Nevada between 52,600 and 14,000 14C yr B.P. Total organic carbon data from a Pyramid Lake sediment core also indicate oscillations in glacier activity between >39,500 and ~13,600 14C yr B.P. Alpine glacier oscillations occurred on a frequency of ???1900 yr in both basins, suggesting that millennial-scale oscillations occurred in California and Nevada during most of the past 52,600 yr.

A full lipid biomarker based record from Lake Challa, Tanzania

NASA Astrophysics Data System (ADS)

Blaga, C. I.; de Leeuw, J. W.; Verschuren, D.; Sinninghe Damsté1, J. S.

2012-04-01

The climate of the regions surrounding the Indian Ocean - East Africa, Arabian and Indian peninsulas - is strongly dominated by the dynamics of the seasonal monsoon. To understand the long and short term driving forces behind the natural climatic variability in this region it is highly important to reconstruct climatic changes in the past and, thereby, predict future changes taking into account also anthropogenic activities. Most low latitude locations lack continuous, highly resolved continental records with good age control. From the few existing records acquired from tropical glacier ice, cave stalagmites and fossil diatoms a thorough understanding of the climatic variations reflected (rainfall and drought or temperature and its effect on precipitation) is scanty. Chemically stratified crater lakes accumulate high-quality climate-proxy records as shown in very recent studies done on the continuous and finely laminated sediment record of Lake Challa situated on the lower East slope of Mt. Kilimanjaro (Verschuren et al. 2009; Wolff et al. 2011). The unique location of this lake in equatorial East Africa implies that the climate variability is influenced by the Indian Ocean and not by the Atlantic due to the Congo Air Boundary (Thierney et al. 2011). The objective of this study is to fully explore the biomarker content of the Lake Challa sedimentary record already characterized by an excellent time resolution and chronology. Various normal chain lipids (n-alkanes, n-fatty acids, n-alcohols), sterols, long-chain diols, triterpenoids and glycolipids in sedimentary organic matter, were determined in their solvent-extractable (free) and saponification-released forms (bound). The changing composition of organic matter content from the investigated lake is used as a framework to trace palaeo-humidity, terrestrial input, algal input, temperature in sediment traps and underlying sediments of Lake Challa to further our palaeo-environmental knowledge based on GDGT's and

Lake Sediments show the Frequency of 21st Century Extreme Flooding in the UK is Unprecedented

NASA Astrophysics Data System (ADS)

Chiverrell, R. C.; Sear, D. A.; Warburton, J.; Macdonald, N.; Schillereff, D. N.; Dearing, J.; Croudace, I. W. C.

2016-12-01

Flooding in northwest England has been reconstructed from the coarse grained units preserved in lake sediment sequences at Bassenthwaite Lake, a record that includes the floods of December 2015 (Storm Desmond) and November 2009 and shows they were the most extreme in over 600 years. The inception and propagation of a lake sediment flood event horizon in the aftermath of the December 2015 storms in the UK has been explored as part of NERC Urgency Grant that focuses on Bassenthwaite Lake, Brotherswater, Buttermere and Ullswater. Our approach involves repeat coring of locations over 6-12 months, sediment trapping, and testing how this recent extreme event has settled into the sediment record. For Bassenthwaite Lake linking our new sediment palaeoflood series to river discharges, provides the first assessment of flood frequency and magnitude based on lake sediments for the UK. We show that recent devastating flooding in NW England in 2009 was the largest event in 415 years, had a recurrence interval far larger (1:9000 year) than conventional analysis based on short term records suggest (1:700 year), and occurred during a cluster of floods that is unprecedented in 600 years. Particle size characteristics of flood laminations, after correction for variations in the stability of catchment sediment sources, were correlated on a hydrodynamic basis with recorded river flows. The particle size flood record is underpinned by a robust chronology to CE 1420 derived from radionuclide (Pb210, Am241, and Cs137) dating and correlations to the rich history of metal (Pb, Zn, Ba and Cu) mining in the catchment accurately recorded in the sediment geochemistry. The sediment palaeoflood series reveals five flood rich periods (CE 1460-1500, 1580-1680, 1780-1820, 1850-1925, 1970-present), and these correspond with positive phases of reconstructed winter NAOI and other Atlantic circulation patterns. The hydro-climatology of the extreme events (top 1% of floods) in our series, show that 67

Reconstruction of the West Pacific ENSO precipitation anomaly using the compound-specific hydrogen isotopic record of marine lake sediments of Palau

NASA Astrophysics Data System (ADS)

Smittenberg, R. H.; Sachs, J. P.; Dawson, M. N.

2004-12-01

There is still much uncertainty whether the El Niño Southern Oscillation (ENSO) will become stronger or more frequent in a warming global climate. A principal reason for this uncertainty stems from a glaring lack of paleoclimate data in the equatorial Pacific, which hampers model validation. To partly resolve this data deficiency, sediments of three marine anoxic lakes were cored in Palau, an island group that lies in the heart of the West Pacific Warm Pool. The lakes contain seawater that seeps through fissures in the surrounding karst, and they are permanently stratified due to fresh water input provided by the year-round wet climate (map 1970-2000 = 3.7m). During ENSO events, however, the islands suffer from drought. The surface water hydrogen isotopic compositions in the lakes are sensitive to the relative proportions of D-depleted rainwater and D-enriched seawater, and are therefore sensitive to ENSO events. The lake surface water H/D values are recorded by algal and bacterial biomarkers that are preserved well in the highly organic and anoxic sediments, which accumulate relatively fast (mean 1 mm/yr). Ongoing down core measurement will eventually result in a precipitation proxy record of the islands. To obtain endmember D/H values, a comprehensive set of water samples from sea, lakes and rain water was obtained, as well as suspended particulate matter. Higher plant biomarker D/H values derived from the jungle vegetation surrounding the lakes may render supporting climatic proxy data, being influenced by evapotranspiration. Some lakes are inhabited by millions of jellyfish (Mastigias) that live in symbiosis with zooxanthellae. The jellyfish of one of the investigated lakes disappeared completely after the last large ENSO event in 1998 (returning in 2000-01), and a correlation is suggested. To reconstruct the history of jellyfish occurrence, jellyfish and sedimentary lipids were extracted and compared. In addition to a possible ENSO proxy record, this

Five thousand years of tropical lake sediment DNA records from Benin

NASA Astrophysics Data System (ADS)

Bremond, L.; Favier, C.; Ficetola, G. F.; Tossou, M. G.; Akouégninou, A.; Gielly, L.; Giguet-Covex, C.; Oslisly, R.; Salzmann, U.

2017-08-01

Until now, sedimentary DNA (sedDNA) studies have only focused on cold and temperate regions were DNA is relatively well preserved. Consequently, the tropics, where vegetation is hyperdiverse and natural archives are rare, have been neglected and deserve attention. In this study, we used next-generation sequencing to barcode sedDNA from Lake Sele, localized in the tropical lowlands of Benin (Africa), and compared the taxonomic diversity detected by DNA analyses with pollen assemblages. Plant sedDNA was successfully amplified from 33 of the 34 successfully extracted samples. In total, 43 taxa were identified along the 5000 years spanned by the sediment: 22 taxa were identified at the family level and 21 at the genus level. The plant diversity recovered through sedDNA from Lake Sele showed a specific local signal and limited overlapping with pollen. Introduced plants, grown and cultivated close to the water, such as sweet potato, were also well recorded by sedDNA. It appears, therefore, to be a promising approach to studying past diversity in tropical regions, and could help in tracking the introduction and history of agriculture. This is the first time this method has been used in the field of domestication and dissemination of several specific crops, and the results are very encouraging.

Lake and Bog Sediment Records of Holocene Climate and Glacier Variability in the Cordillera Vilcabamba of Southern Peru

NASA Astrophysics Data System (ADS)

Schweinsberg, A.; Licciardi, J. M.; Rodbell, D. T.; Stansell, N.

2013-12-01

Records of past fluctuations in climatically sensitive tropical glaciers are among the best indicators of regional paleoclimatic trends and forcings. However, continuous sediment records in this region remain limited, particularly during the Holocene. Here we present the first continuous records of glacier activity in the Cordillera Vilcabamba (13°20'S) of southern Peru from lake and bog sediment cores in stratigraphic contact with 10Be-dated moraines. Completed analyses include sediment lithostratigraphy, magnetic susceptibility, and biogenic silica, in conjunction with AMS radiocarbon dates on charcoal. Carbon measurements, bulk density, and bulk sedimentation rates are used to derive a record of clastic sediment flux that serves as a proxy indicator of former glacier activity. Visually distinct sedimentological variations, magnetic susceptibility peaks, and radiocarbon dates were correlated among adjacent cores to construct one composite record representative of each coring site. Three composite cores are presented: two from the Rio Blanco valley and one from the Yanama valley. Sediment records from these two glaciated valleys suggest a series of environmental changes during the last ~12,000 calendar years BP. Clastic sediment flux trends are broadly consistent with published evidence that the early to middle Holocene was relatively warm and arid in the southern Peruvian Andes. An episode of high clastic flux in the late Holocene may reflect enhanced glacial activity in response to the onset of cooler and wetter conditions. A prominent peak in magnetic susceptibility at 1660 cal yr BP is present in all composite cores and serves as a chronostratigraphic marker. In addition, our new basal radiocarbon ages place limits on the cosmogenic 10Be production rate in the high Andes, suggesting the cosmogenic 10Be production rate is considerably lower than previously published estimates.

Late Pleistocene and Holocene paleoclimate and alpine glacier fluctuations recorded by high-resolution grain-size data from an alpine lake sediment core, Wind River Range, Wyoming, USA

NASA Astrophysics Data System (ADS)

Thompson Davis, P.; Machalett, Björn; Gosse, John

2013-04-01

Varved lake sediments, which provide ideal high-resolution climate proxies, are not commonly available in many geographic areas over long time scales. This paper utilizes high-resolution grain-size analyses (n = 1040) from a 520-cm long sediment core from Lower Titcomb Lake (LTL), which lies just outside the type Titcomb Basin (TTB) moraines in the Wind River Range, Wyoming. The TTB moraines lie between Lower Titcomb Lake and Upper Titcomb Lake (UTL), about 3 km beyond, and 200 m lower than the modern glacier margin and Gannett Peak (Little Ice Age) moraines in the basin. Based on cosmogenic exposure dating, the TTB moraines are believed to be Younger Dryas (YD) age (Gosse et al., 1995) and lie in a geomorphic position similar to several other outer cirque moraines throughout the western American Cordillera. Until recently, many of these outer cirque moraines were believed to be Neoglacial age. The sediment core discussed here is one of five obtained from the two Titcomb Lakes, but is by the far the longest with the oldest sediment depositional record. Two AMS radiocarbon ages from the 445- and 455-cm core depths (about 2% loss on ignition, LOI) suggest that the lake basin may have been ice-free as early as 16.1 or even 16.8 cal 14C kyr, consistent with 10Be and 26Al exposure ages from boulders and bedrock surfaces outside the TTB moraines. The 257-cm depth in the core marks an abrupt transition from inorganic, sticky gray silt below (<1% LOI) to more organic, less sticky, light brown silt above (4-10% LOI). Eight AMS radiocarbon ages on bulk sediment and macrofossils date the transition to about 11.6 cal 14C kyr. Thus, sampling resolution above the transition is about 22.57 yr and below the transition is about 12.56 yr, consistent with a decreased sediment accumulation rate in LTL when Younger Dryas ice pulled back from the TTB moraines opening up UTL as a sediment depositional basin. The presented high-resolution grain size record reveals amplitudes and other

Summer temperatures inferred from varved lacustrine sediment at Iceberg Lake in southcentral Alaska

NASA Astrophysics Data System (ADS)

Diedrich, K.; Loso, M. G.

2010-12-01

Iceberg Lake, a glacier-dammed lake in southcentral Alaska, has been previously shown to record over 1,500 years of continuous laminated lacustrine sediment deposition. Because previous work was based on examination of subaerial outcrops exposed by stream incision in the bed of the jökulhlaup-drained lake, the length of the record was limited by the extent of the outcrops. In August of 2010, we returned to core the remote lake; our goal was recovery of the complete sedimentary record in the lake, extending perhaps back to the onset of late Holocene glaciation—around 3-5 ka in this region. We used a Vibarcorer system to recover sediment cores from two locations, one near the site of previous work and another at the distal end of the lake. The longest cores recovered were 5.2 meters and 6.2 meters at the proximal and distal sites, respectively. Based on the average lamination thickness established previously at the proximal site (4.7 mm), these cores should each represent over 1000 years of sediment accumulation, and likely much longer at the distal site, where laminations are expected to be thinner. Having established previously that the lake’s laminations are annual varves and that they are positively correlated with summer (melt-season) temperatures, our analysis is focused on documenting a long time-series of annual sediment accumulation and summer-layer particle size. Both measurements will be used to interpret the history of summer temperatures. The cores may also provide sedimentary evidence of the timing of advances/retreats of nearby glaciers, including the Tana Glacier and Bagley Icefield, helping to clarify the poorly-constrained timing of neoglaciation in Southern Alaska. The paleoclimate record produced at Iceberg Lake will be included in the Arctic System Science 8ka project

Sedimentation of Lake Taneycomo, Missouri, 1913-1987

USGS Publications Warehouse

Berkas, W.R.

1989-01-01

On the basis of the data from a sedimentation survey done by the U.S. Department of Agriculture, Soil Conservation Service, during 1935 and data collected by the U.S. Geological Survey during 1987, the volume of sediment accumulated in Lake Taneycomo from 1913 to 1935 and 1913 to 1987 was determined. Table Rock Dam, built directly upstream from Lake Taneycomo during 1958, eliminated about 92% of the 4,644-sq mi basin from contributing sediment directly to the lake. Cesium-137 isotope was used as a tracer in the sediment to determine the quantity of deposition in the lake after Table Rock Dam was completed. The relation between cross-sectional area and distance upstream from the dam (curve method) was used to determine the 1913 (original), the 1935, and the 1987 volumes of Lake Taneycomo. A total of 910,000,000 cu ft of sediment accumulated between 1913 and 1935, 42% of the original volume of the lake. A total of 1 ,066,000,000 cu ft of sediment accumulated between 1913 and 1987 , 49% of the original volume. Lake Taneycomo seems to be functioning as an alluvial river, responding to the new energy gradient established by the spillway at Ozark Beach Dam, and later to changes in the sediment load. The upper two-thirds of the lake seems to have been scoured after Table Rock Dam greatly decreased the sediment load to the lake. The cesium-137 analysis indicated that sediment is still accumulating in the lower reaches of the lake, with measured accumulation generally ranging from 0.2 to 2.6 ft. (USGS)

Fingerprinting of glacial silt in lake sediments yields continuous records of alpine glaciation (35-15 ka), western USA

NASA Astrophysics Data System (ADS)

Rosenbaum, Joseph G.; Reynolds, Richard L.; Colman, Steven M.

2012-09-01

Fingerprinting glacial silt in last glacial-age sediments from Upper Klamath Lake (UKL) and Bear Lake (BL) provides continuous radiocarbon-dated records of glaciation for the southeastern Cascade Range and northwestern Uinta Mountains, respectively. Comparing of these records to cosmogenic exposure ages from moraines suggests that variations in glacial flour largely reflect glacial extent. The two areas are at similar latitudes and yield similar records of glacial growth and recession, even though UKL lies less than 200 km from the ocean and BL is in the continental interior. As sea level began to fall prior to the global Last Glacial Maximum (LGM), existing glaciers in the UKL area expanded. Near the beginning of the global LGM (26.5 ka), the BL record indicates onset of glaciation and UKL-area glaciers underwent further expansion. Both records indicate that local glaciers reached their maximum extents near the end of the global LGM, remained near their maxima for ~ 1000 yr, and underwent two stages of retreat separated by a short period of expansion.

Sediment characteristics and sedimentation rates in Lake Michie, Durham County, North Carolina, 1990-92

USGS Publications Warehouse

Weaver, J.C.

1994-01-01

A reservoir sedimentation study was conducted at 508-acre Lake Michie, a municipal water-supply reservoir in northeastern Durham County, North Carolina, during 1990-92. The effects of sedimentation in Lake Michie were investigated, and current and historical rates of sedimentation were evaluated. Particle-size distributions of lake-bottom sediment indicate that, overall, Lake Michie is rich in silt and clay. Nearly all sand is deposited in the upstream region of the lake, and its percentage in the sediment decreases to less than 2 percent in the lower half of the lake. The average specific weight of lake-bottom sediment in Lake Michie is 73.6 pounds per cubic foot. The dry-weight percentage of total organic carbon in lake-bottom sediment ranges from 1.1 to 3.8 percent. Corresponding carbon-nitrogen ratios range form 8.6 to 17.6. Correlation of the total organic carbon percentages with carbon-nitrogen ratios indicates that plant and leaf debris are the primary sources of organic material in Lake Michie. Sedimentation rates were computed using comparisons of bathymetric volumes. Comparing the current and previous bathymetric volumes, the net amount of sediment deposited (trapped) in Lake Michie during 1926-92 is estimated to be about 2,541 acre-feet or slightly more than 20 percent of the original storage volume computed in 1935. Currently (1992), the average sedimentation rate is 38 acre-feet per year, down from 45.1 acre-feet per year in 1935. To confirm the evidence that sedimentation rates have decreased at Lake Michie since its construction in 1926, sediment accretion rates were computed using radionuclide profiles of lake-bottom sediment. Sediment accretion rates estimated from radiochemical analyses of Cesium-137 and lead-210 and radionuclides in the lake-bottom sediment indicate that rates were higher in the lake?s early years prior to 1962. Estimated suspended-sediment yields for inflow and outflow sites during 1983-91 indicate a suspended-sediment trap

Continuous Lake-Sediment Records of Glaciation in the Sierra Nevada between 52,600 and 12,500 14C yr B.P

NASA Astrophysics Data System (ADS)

Benson, Larry V.; May, Howard M.; Antweiler, Ronald C.; Brinton, Terry I.; Kashgarian, Michaele; Smoot, Joseph P.; Lund, Steve P.

1998-09-01

The chemistry of the carbonate-free clay-size fraction of Owens Lake sediments supports the use of total organic carbon and magnetic susceptibility as indicators of stadial-interstadial oscillations. Owens Lake records of total organic carbon, magnetic susceptibility, and chemical composition of the carbonate-free, clay-size fraction indicate that Tioga glaciation began ˜24,500 and ended by ˜13,600 14C yr B.P. Many of the components of glacial rock flour (e.g., TiO 2, MnO, BaO) found in Owens Lake sediments achieved maximum values during the Tioga glaciation when valley glaciers reached their greatest extent. Total organic carbon and SiO 2(amorphous) concentrations reached minimum values during Tioga glaciation, resulting from decreases in productivity that accompanied the introduction of rock flour into the surface waters of Owens Lake. At least 20 stadial-interstadial oscillations occurred in the Sierra Nevada between 52,600 and 14,000 14C yr B.P. Total organic carbon data from a Pyramid Lake sediment core also indicate oscillations in glacier activity between >39,500 and ˜13,600 14C yr B.P. Alpine glacier oscillations occurred on a frequency of ≤1900 yr in both basins, suggesting that millennial-scale oscillations occurred in California and Nevada during most of the past 52,600 yr.

Lead isotope ratios in six lake sediment cores from Japan Archipelago: Historical record of trans-boundary pollution sources.

PubMed

Hosono, Takahiro; Alvarez, Kelly; Kuwae, Michinobu

2016-07-15

Sediment cores from six lakes situated from north to south on the Japanese Archipelago were collected during 2009-2010 to investigate the hypothesis that deposition of lead (Pb) was coming from East Asia (including China, South Korea and eastern part of Russia). Accumulation rates and ages of the lake sediment were estimated by the (210)Pb constant rate of supply model and (137)Cs inputs to reconstruct the historical trends of Pb accumulation. Cores from four lakes located in the north and central Japan, showed clear evidence of Pb pollution with a change in the (206)Pb/(207)Pb and (208)Pb/(207)Pb ratios in the recent sediment as compared to the deeper sediment. Among the six studied lakes, significant inputs of anthropogenic lead emissions were observed at Lake Mikazuki (north Hokkaido in north Japan), Lake Chokai (north of Honshu), and Lake Mikuriga (central part of Honshu). Pb isotopic comparison of collected core sediment and previously reported data for wet precipitation and aerosols from different Asian regions indicate that, before 1900, Pb accumulated in these three lakes was not affected by trans-boundary sources. Lake Mikazuki started to receive Pb emissions from Russia in early 1900s, and during the last two decades, this lake has been affected by trans-boundary Pb pollution from northern China. Lake Chokai has received Pb pollutant from northern China since early 1900s until 2009, whereas for the Lake Mikuriga the major Pb contaminant was transported from southern China during the past 100years. The results of our study demonstrate that Japan Archipelago has received trans-boundary Pb emissions from different parts of East Asian region depending on location, and the major source region has changed historically. Copyright © 2016 Elsevier B.V. All rights reserved.

Environmental magnetic record and paleosecular variation data for the last 40 kyrs from the Lake Biwa sediments, Central Japan

NASA Astrophysics Data System (ADS)

Hayashida, Akira; Ali, Mohammed; Kuniko, Yoshiki; Kitagawa, Hiroyuki; Torii, Masayuki; Takemura, Keiji

2007-07-01

We have conducted paleomagnetic and environmental magnetic analysis of a sediment piston core recovered from Lake Biwa, central Japan. Tephrochronology and AMS radiocarbon dating showed that this core covers the time period since about 40 kyr BP. The variation of paleomagnetic direction shows a good agreement with the PSV record for the last 10 kyrs from the deeper water site (BIWA SV-3; Ali et al., 1999), although the amplitudes are subdued probably due to the relatively lower accumulation rate at the shallower site. Inclination lows of the pre-Holocene interval are correlated to PSV records reported from the marine sediments off Shikoku and in the Japan Sea. In addition, the variation of magnetic mineral concentration reflects environmental changes during the last glacial period. It is suggested that the flux of fine-grained magnetite, probably associated with greater precipitation, was increased during interstadial periods. The variation of anhysteretic remanent magnetization is likely correlated to the Dansgaard-Oeschger (D-O) cycles recorded in Greenland ice cores. An apparent swing of the PSV curve is recognized at about 27 ka, but evidence for the Mono Lake excursion at 32 ka around the D-O events 6 and 7 is unclear. Combination of the detailed paleomagnetic record and the sub-Milankovitch climate cycles thus provides better resolution for understanding geomagnetic secular variation and polarity excursions in space and time.

Post-depositional formation of vivianite-type minerals alters sediment phosphorus records

NASA Astrophysics Data System (ADS)

Dijkstra, Nikki; Hagens, Mathilde; Egger, Matthias; Slomp, Caroline P.

2018-02-01

Phosphorus (P) concentrations in sediments are frequently used to reconstruct past environmental conditions in freshwater and marine systems, with high values thought to be indicative of a high biological productivity. Recent studies suggest that the post-depositional formation of vivianite, an iron(II)-phosphate mineral, might significantly alter trends in P with sediment depth. To assess its importance, we investigate a sediment record from the Bornholm Basin that was retrieved during the Integrated Ocean Drilling Program (IODP) Baltic Sea Paleoenvironment Expedition 347 in 2013, consisting of lake sediments overlain by brackish-marine deposits. Combining bulk sediment geochemistry with microanalysis using scanning electron microscope energy dispersive spectroscopy (SEM-EDS) and synchrotron-based X-ray absorption spectroscopy (XAS), we demonstrate that vivianite-type minerals rich in manganese and magnesium are present in the lake deposits just below the transition to the brackish-marine sediments (at 11.5 to 12 m sediment depth). In this depth interval, phosphate that diffuses down from the organic-rich, brackish-marine sediments meets porewaters rich in dissolved iron in the lake sediments, resulting in the precipitation of iron(II) phosphate. Results from a reactive transport model suggest that the peak in iron(II) phosphate originally occurred at the lake-marine transition (9 to 10 m) and moved downwards due to changes in the depth of a sulfidization front. However, its current position relative to the lake-marine transition is stable as the vivianite-type minerals and active sulfidization fronts have been spatially separated over time. Experiments in which vivianite was subjected to sulfidic conditions demonstrate that incorporation of manganese or magnesium in vivianite does not affect its susceptibility to sulfide-induced dissolution. Our work highlights that post-depositional formation of iron(II) phosphates such as vivianite has the potential to strongly

Chemical fractionation of lake sediments to determine the effects of land-use change on nutrient loading

NASA Astrophysics Data System (ADS)

Heathwaite, A. L.

1994-07-01

Lake studies allow contemporary sediment and nutrient dynamics to be placed in a historical context in order that trends and rates of change in catchment inputs may be calculated. Here, a synthesis of the temporal information contained in catchment and lake sediment records is attempted. A chemical fractionation technique is used to isolate the different sediment sources contained in the lake core, and 210Pb dates provide an accurate record of changes in lake sediment sources over the past 100 years. The extent to which land-use records, collated from agricultural census returns, and process-based studies of sediment and nutrient export from different catchment land uses can be used to explain the trends observed in the lake sediments is examined. Sediment influx to the study lake has increased from less than 2 mm year -1 prior to the Second World War to over 10 mm year -1 at present. The source of the sediment is largely unaltered and unweathered allochthonous material eroded from the catchment. Land-use records suggest that the intensification of agriculture, characterized by a shift towards arable land immediately postwar, followed by an increase in the area of temporary grass in the 1960s, may be the cause of accelerated catchment erosion; both land-use changes would have increased the area of ploughed land in the catchment. An increase in the number of cattle and sheep in the catchment from around 2000 and 6000, respectively, in the 1940s, to a peak of nearly 7000 cattle and over 15 000 sheep in the 1980s, provides a further source of sediment and nutrients. Livestock are grazed on permanent grassland which is commonly located on steep hillslopes and in riparian zones where saturation-excess surface runoff may be an important hydrological pathway. Rainfall simulation experiments show that surface runoff from heavily grazed grassland has a high suspended sediment, ammonium-nitrogen and particulate phosphorus load. The combined effect of the long-term increase

Long-range transport of pollutants to the Falkland Islands and Antarctica: evidence from lake sediment fly ash particle records.

PubMed

Rose, Neil L; Jones, Vivienne J; Noon, Philippa E; Hodgson, Dominic A; Flower, Roger J; Appleby, Peter G

2012-09-18

(210)Pb-dated sediment cores taken from lakes on the Falkland Islands, the South Orkney Islands, and the Larsemann Hills in Antarctica were analyzed for fly ash particles to assess the temporal record of contamination from high temperature fossil-fuel combustion sources. Very low, but detectable, levels were observed in the Antarctic lakes. In the Falkland Island lakes, the record of fly ash extended back to the late-19th century and the scale of contamination was considerably higher. These data, in combination with meteorological, modeling, and fossil-fuel consumption data, indicate most likely sources are in South America, probably Chile and Brazil. Other southern hemisphere sources, notably from Australia, contribute to a background contamination and were more important historically. Comparing southern polar data with the equivalent from the northern hemisphere emphasizes the difference in contamination of the two circumpolar regions, with the Falkland Island sites only having a level of contamination similar to that of northern Svalbard.

Testing the potential of 10Be in varved sediments from two lakes for solar activity reconstruction

NASA Astrophysics Data System (ADS)

Czymzik, Markus; Muscheler, Raimund; Brauer, Achim; Adolphi, Florian; Ott, Florian; Kienel, Ulrike; Dräger, Nadine; Slowinski, Michal; Aldahan, Ala; Possnert, Göran

2015-04-01

The potential of 10Be in annually laminated (varved) lake sediments for solar activity reconstruction is, to date, largely unexplored. It is hypothesized that 10Be contents in sediments from well-chosen lakes reflect the solar induced atmospheric production signal. The varved nature of these archives provides the chance to establish solar activity time-series with very high temporal precision. However, so far solar activity reconstruction from 10Be in varved lake sediments is hampered due to a lack of detailed knowledge of the process chain from production in the atmosphere to deposition on the lake floor. Calibrating 10Be time-series from varved lake sediments against complementary proxy records from the same sediment archive as well as instrumental meteorological and solar activity data will allow a process-based understanding of 10Be deposition in these lakes and a quantitative evaluation of their potential for solar activity reconstruction. 10Be concentration and flux time-series at annual resolution were constructed for the period 1983 to 2007 (approx. solar cycles 22 and 23) conducting accelerator mass spectrometry and varve chronology on varved sediments of Lakes Tiefer See and Czechowski, located on an east-west transect at a distance of about 450 km in the lowlands of northern-central Europe. 10Be concentrations vary between 0.9 and 1.8*108atoms/g, with a mean of 1.3*108atoms/g in Lake Tiefer See and between 0.6 and 1.6*108atoms/g, with a mean of 1*108atoms/g in Lake Czechowski. Calculated mean 10Be flux is 2.3*108atoms/cm2/year for Lake Tiefer See and 0.7*108atoms/cm2/year for Lake Czechowski. Calibrating the 10Be time-series against corresponding geochemical μ-XRF profiles, varve thickness and total organic carbon records as well as precipitation data from the nearby stations Schwerin for Lake Tiefer See and Koscierzyna for Lake Czechowski and a neutron monitor record of solar activity suggests (1) a complex interaction of varying processes influencing

The Lake Towuti Drilling Project: A New, 1-Million Year Record of Indo-Pacific Hydroclimate

NASA Astrophysics Data System (ADS)

Russell, J. M.; Bijaksana, S.; Vogel, H.; Melles, M.; Crowe, S.; Fajar, S. J.; Hasberg, A. K.; Ivory, S.; Kallmeyer, J.; Kelly, C. S.; Kirana, K. H.; Morlock, M.; Tamuntuan, G. H.; Wicaksono, S. A.

2015-12-01

­The Indo-Pacific region plays an integral role in the Earth's climate system. Changes in local insolation, greenhouse gas concentrations, ice volume, and local sea level are each hypothesized to exert a dominant control on Indo-Pacific hydroclimate variations through the Pleistocene, yet existing records from the region are generally short and exhibit fundamental differences in orbital-scale patterns that limit our understanding of the regional climate responses to these global forcings. New paleoclimate records spanning multiple glacial-interglacial cycles are therefore required to document the region's hydroclimatic response to the full range of global climate boundary conditions observed during the late Quaternary. Lake Towuti is located in central Indonesia and is the only known terrestrial sedimentary archive in the region that spans multiple glacial-interglacial cycles. From May - July, 2015, the Towuti Drilling Project, consisting of nearly 40 scientists from eight countries, recovered over 1,000 meters of new sediment core from Lake Towuti. This includes cores though the entire sediment column to bedrock, which likely provide a >1-million-year records of regional hydroclimate. On-site borehole and sediment core logging data document major shifts in sediment composition, including transitions from lake clays to peats, calcareous sediments, and gravels. These data show excellent agreement with major lithological transitions recorded in seismic reflection data, and indicate large changes in lake levels and hydroclimate through the late Quaternary. Prior work on Lake Towuti indicated a dominant control by global ice volume on regional hydroclimate, a hypothesis we aim to test through the analysis of these new cores. This presentation will review existing records from the region and show the first long geochemical and sedimentological records from Lake Towuti to understand orbital-scale hydrologic change during the last ~1 million years.

Sedimentological, mineralogical, and geochemical results from surface sediments and the sediment record from Site 2 of the ICDP drilling project at Lake Towuti, Indonesia

NASA Astrophysics Data System (ADS)

Hasberg, A. K.; Melles, M.; Wennrich, V.; Vogel, H.; Just, J.; Russell, J. M.; Bijaksana, S.; Morlock, M.; Opitz, S.

2017-12-01

More than 1000 m of sediment core were recovered in spring 2015 from three different drill sites in tropical Lake Towuti (2.5°S, 121°E), Indonesia, during the Towuti Drilling Project (TDP) of the International Continental Scientific Drilling Program (ICDP). Furthermore, a set of 84 lake surface sediment samples, distributed over the entire lake, was collected in order to better understand modern sedimentary processes. The surface samples were investigated for physical, chemical, mineralogical, and biological properties at the University of Cologne (UoC), Germany. On the sediment cores macro- and microscopical lithological descriptions, line-scan imaging, logging of physical properties (MSCL), and subsampling was conducted at the National Lacustrine Core Facility of the University of Minnesota, USA, in November 2015 and January 2016. Afterwards, the archive core halves and 672 subsamples of TDP Site 2 were shipped to the UoC for X-Ray Fluorescence (XRF) scanning and sedimentological, geochemical, and mineralogical analyses, respectively, supplemented by visible to near-infrared spectroscopy (VNIR) at Brown University, USA. The data from the surface samples evidence that allochthonous sedimentation in Lake Towuti today is dominated by fluvial supply from five distinguishable source areas: (i) the Mahalona River to the north, which drains lakes Mahalona and Matano, (ii) inlets around the village of Timampu to the northwest, (iii) the Loeha River to the east, (iv) the Lengke River to the south, and (v) the Lemo-Lemo River to the northeast of Lake Towuti. Of these, source areas (ii) and (iii) as well as (iv) and (v) have similar geochemical compositions, respectively. In addition, the lake sedimentation is significantly influenced by gravitational sediment supply from steep slopes as well as lake-internal gravitational and density-driven processes. The uppermost 41 m of sediment core 2A consist of pelagic sediments (totaling 11 m) and event layers from mass movement

The extent and historical trend of metal pollution recorded in core sediments from the artificial Lake Shihwa, Korea.

PubMed

Ra, Kongtae; Bang, Jae-Hyun; Lee, Jung-Moo; Kim, Kyung-Tae; Kim, Eun-Soo

2011-08-01

The vertical distribution of trace metals in sediment cores was investigated to evaluate the extent and the historical record of metal pollution over 30 years in the artificial Lake Shihwa in Korea. A marked increase of trace metals after 1980 was observed due to the operation of two large industrial complexes and dike construction for a reclamation project. There was a decreasing trend of metal concentrations with the distance from the pollution source. The enrichment factor and pollution load index of the metals indicated that the metal pollution was mainly derived from Cu, Zn and Cd loads due to anthropogenic activities. The concentrations of Cr, Ni, Cu, Zn, As and Pb in the upper part of all core sediments exceeded the ERL criteria of NOAA. Our results indicate that inadequate planning and management of industrialization and a large reclamation project accomplished by dike construction have continued to strongly accelerate metal pollution in Lake Shihwa. Crown Copyright © 2011. Published by Elsevier Ltd. All rights reserved.

A Long Pleistocene Paleoclimate Record from Stoneman Lake, Arizona

NASA Astrophysics Data System (ADS)

Fawcett, P. J.; Anderson, R. S.; Brown, E. T.; Werne, J. P.; Jimenez-Moreno, G.; Toney, J. L.; Garcia, D.; Garrett, H. L.; Dunbar, N. W.

2015-12-01

Long continuous lake sediment cores provide enormous potential for interpreting climate change. In the American Southwest, long records are revolutionizing our understanding of megadroughts, which have occurred in the past and will most certainly occur in the future with rapidly changing climate. One site with the potential to study ancient megadroughts is Stoneman Lake, central Arizona, whose basin is a circular depression formed by a collapse in late Tertiary volcanics. The lake is spring fed, most recently alternating between a marsh and a lake, with water levels having fluctuated by > 3 meters over the last 25 years. Its small closed drainage basin (ca. 2.5 km2) with one small inflowing stream is key to the sensitivity of the record. Two parallel lacustrine sediment cores (70 m and 30 m deep) were recovered in October of 2014. Our preliminary chronology includes 8 AMS dates in the upper 7 m and two distinct tephras at 30.8 m depth and 36.3 m depth. Radiocarbon dates show a 2.7-m-thick Holocene section, and then a low Pleistocene SAR with an age of 11,000 cal yr B.P. at ~2.8 m to an age of 46,500 cal yr B.P. at 4.2 m depth. We estimate that the 70-m deep hole will provide a climate record back to ~1.3 million years ago. Of particular interest are the interglacials that serve as good analogs for future climate including MIS 11 and MIS 19. Initial core description includes MS, bulk density and high-resolution images. Holocene sediments are characterized by massive, dark organic rich silty clays with no distinct lamination. Sediments from the Last Glacial Maximum are well-laminated, light brown silty clays with few organics present. The distinctive laminations probably represent a very deep lake and therefore a wet cold climate, also verified by pollen data. There are several repeated intervals of laminated sediments deeper in the core that may represent older glacial maxima. Future work will include detailed pollen, plant macrofossil and charcoal analysis

Suspending sediment transport, sedimentation, and resuspension in Lake Houston, Texas: Implications for water quality

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matty, J.M.; Anderson, J.B.; Dunbar, R.B.

1987-01-01

Lake Houston is a man-made reservoir located northeast of Houston, Texas. The purpose of this investigation was to document suspended sediment transport, sedimentation, and resuspension in the lake with a view towards estimating the influence of sedimentation on water quality. Sediment traps were placed in strategic locations in the lake to collect suspended sediments. Samples were analyzed for bulk density, grain size, organic carbon, and a number of trace elements. These data were analyzed along with meteorological data to examine those factors which regulate suspended sediment input and dispersal, and the role of suspended sediments in controlling water quality withinmore » the lake. Sediment input to the lake depends primarily on the intensity of rainfall in the watershed. Sediment movement within the lake is strongly influenced by wave activity, which resuspends sediments from shallow areas, and by wind-driven circulation. The increased residence time of suspended sediments due to resuspension allows greater decomposition of organic matter and the release of several trace elements from sediments to the water column. Virtually all samples from sediment traps suspended between 1 and 5 m above the lake bottom contain medium to coarse silt, and even some very fine sand-sized material. This implies that circulation in Lake Houston is periodically intense enough to transport this size material in suspension. During winter, northerly winds with sustained velocities of greater than 5 m/sec provide the most suitable condition for rapid (< 1 d) transport of suspended sediment down the length of the lake. Fluctuations in current velocities and the subsequent suspension/deposition of particles may explain variations in the abundance of coliform bacteria in Lake Houston.« less

Holocene evolution of the River Nile drainage system as revealed from the Lake Dendi sediment record, central Ethiopian highlands

NASA Astrophysics Data System (ADS)

Wagner, B.; Viehberg, F. A.; Wennrich, V.; Junginger, A.; Kolvenbach, A.; Rethemeyer, J.; Schaebitz, F.; Schmiedl, G. H.

2015-12-01

A 12 m long sediment sequence from Dendi Crater lakes, located on the central Ethiopian Plateau, was analysed with sedimentological and geochemical methods to reconstruct the regional environmental history. Bulk organic carbon samples from 23 horizons throughout the sequence were used for AMS radiocarbon dating and indicate that the sediment sequence spans the last ca. 12 cal kyr BP. Microscope analyses and sedimentological data reveal three tephra layers, of which the most prominent layer with a thickness of ~2 m was deposited at 10.2 cal kyr BP and probably originates from an eruption of the Wenchi crater 12 km to the west of the Dendi lakes. Sedimentological data of the pelagic deposits indicate shifts in erosion and rainfall throughout the record. A decrease in Ca and Sr at 11.6 cal kyr BP is related to the shift of less humid condition during the Younger Dryas (YD) to the return to full humid conditions of the African Humid Period (AHP). Single thin horizons with high carbonate content or high Ti and K imply that short spells of dry conditions and significantly increased rainfall superimpose the generally more humid conditions during the AHP. The end of the AHP is gradual. Relatively stable and less humid conditions characterised the Dendi Crater lakes until around 3.9 cal kyr BP. A highly variable increase in clastic matter over the last 1500 years indicates higher erosion due to short-term variations in precipitation within the Dendi catchment. Overall, the sediment record suggests moderate change of precipitation during the Holocene, which is probably due to their exposed location in the Ethiopian highlands. The data from the Dendi Crater lakes show, in concert with other records from the Nile catchment and the Eastern Mediterranean Sea (EMS), that the Blue Nile provided the main freshwater source for maintaining EMS stratification and sapropel S1 formation between ca. 10.0 and 8.7 cal kyr BP. Subsequent aridification is recorded from equatorial East Africa

Paleosecular Type Curves for South America Based on Holocene-Pleistocene Lake Sediments Studies

NASA Astrophysics Data System (ADS)

Gogorza, C. S.

2007-05-01

Most of the high-resolution paleomagnetic secular variation (PSV) results were obtained from records on sediments from the Northern Hemisphere. Experimental results from South America are scarce. The first results were obtained by Creer et al. (1983) and have been continued since few years ago by the author and collaborators. This review deals with studies of PSV records from bottom sediments from three lakes: Escondido, Moreno and El Trébol (south-western Argentina, 41° S, 71° 30'W). Measurements of directions (declination D and inclination I) and intensity of natural remanent magnetization (NRM), magnetic susceptibility at low and high frequency (specific, X and volumetric, k), isothermal remanent magnetization (IRM), saturation isothermal remanent magnetization (SIRM), and back field were carried out. Stability of the NRM was investigated by alternating-field demagnetization. Rock magnetic studies suggest that the main carriers of magnetization are ferrimagnetic minerals, predominantly pseudo single domain magnetite. The correlation between cores was based on magnetic parameters as X and NRM. The tephra layers were identified from the lithologic profiles and also from the magnetic susceptibility logs. Due to their different chronological meaning and their rather bad behavior as magnetic recorder, these layers were removed from the sequence and the gaps that were produced along the profiles by the removal were closed, obtaining a "shortened depth". Radiocarbon age estimates from these cores and from earlier studies allow us to construct paleosecular variation records for the past 22,000 years. Inclination and declination curves (Gogorza et al., 2000a; Gogorza et al., 2002; Irurzun et al., 2006) show trends that are similar to a paleomagnetic secular variation curve for SW of Argentina (Gogorza et al., 2000b). References Creer, K.M., Tucholka, P. and Barton, C.E. 1983. Paleomagnetism of lake sediments, in Geomagnetism of Baked Clays and Recent Sediments, edited

Fingerprinting of glacial silt in lake sediments yields continuous records of alpine glaciation (35–15 ka), western USA

USGS Publications Warehouse

Rosenbaum, Joseph G.; Reynolds, Richard L.; Colman, Steven M.

2012-01-01

Fingerprinting glacial silt in last glacial-age sediments from Upper Klamath Lake (UKL) and Bear Lake (BL) provides continuous radiocarbon-dated records of glaciation for the southeastern Cascade Range and northwestern Uinta Mountains, respectively. Comparing of these records to cosmogenic exposure ages from moraines suggests that variations in glacial flour largely reflect glacial extent. The two areas are at similar latitudes and yield similar records of glacial growth and recession, even though UKL lies less than 200 km from the ocean and BL is in the continental interior. As sea level began to fall prior to the global Last Glacial Maximum (LGM), existing glaciers in the UKL area expanded. Near the beginning of the global LGM (26.5 ka), the BL record indicates onset of glaciation and UKL-area glaciers underwent further expansion. Both records indicate that local glaciers reached their maximum extents near the end of the global LGM, remained near their maxima for ~1000 yr, and underwent two stages of retreat separated by a short period of expansion.

Sedimentation in Lake Elgygytgyn, NE Russia, during the past 340.000 years

NASA Astrophysics Data System (ADS)

Juschus, O.; Melles, M.; Wennrich, V.; Nowaczyk, N.; Brigham-Grette, J.; Minyuk, P.

2009-12-01

In spring 2009, an ICDP drilling operation on Lake Elgygytgyn, located in a 3.6 Myr old meteorite impact crater in NE Siberia, penetrated 312 m of lake sediments above a suevite layer and brecciated bedrock. In the uppermost ca. 140 m, the lake sediments according to on-site core descriptions and susceptibility measurements are comparable to those occurring in up to 16.0 m long sediment cores from the central lake part, which were recovered and investigated within the site survey for the drilling project. Assuming comparable sedimentation rates, the upper 80 m of the sediment record may represent the depositional history during the past ca. 3.0 Myr. This poster summarizes the results thus far available from the upper 16 m, in order to illustrate the potential the drilled upper lake sediment record has for reconstructing the environmental and climatic history of the terrestrial Arctic during the Quaternary. Besides two volcanic ash layers and a number of fine-grained turbidites, by far most of the sediments in the central part of Lake Elgygytgyn originate from fluvial and eolian input, and from the biological production in the lake. These pelagic sediments can be distinguished into four depositional units of contrasting lithological and biogeochemical composition, reflecting past environmental conditions associated with relatively warm, peak warm, cold and dry, and cold but more moist climate modes. A relatively warm climate, resulting in complete summer melt of the lake ice cover and seasonal mixing of the water column, prevailed during the Holocene and Marine Isotope Stages (MIS) 3, 5.1 - 5.3, 6.1, 6.3, 6.5, 7.1 - 7.3, 7.5, 8.1, 8.3 and 9.1. MIS 5.5 (Eemian) and 9.5 were characterized by significantly enhanced aquatic primary production and organic matter supply from the catchment, indicating peak warm conditions. During MIS 2, 5.4, 6.2, 6.6, 8.2, 8.4, and 10 the climate was cold and dry, leading to perennial lake ice cover, little regional snowfall, and a

Isotope analyses of the lake sediments in the Plitvice Lakes, Croatia

NASA Astrophysics Data System (ADS)

Horvatinčić, Nada; Sironić, Andreja; Barešić, Jadranka; Bronić, Ines Krajcar; Nikolov, Jovana; Todorović, Nataša; Hansman, Jan; Krmar, Miodrag

2014-10-01

The analyses of radioactive isotopes 14C, 137Cs and 210Pb, and stable isotope 13C were performed in the sediment cores, top 40 cm, taken in 2011 from karst lakes Prošće and Kozjak in the Plitvice Lakes National Park, central Croatia. Frozen sediment cores were cut into 1 cm thick layers and dried. 14C activity in both carbonate and organic fractions was measured using accelerator mass spectrometry technique with graphite synthesis. 137Cs, 210Pb, 214Pb and 214Bi were measured by low level gamma spectrometry method on ORTECHPGe detector with the efficiency of 32%. Distribution of 14C activity from both lakes showed increase of the 14C activity in the top 10-12 cm in both carbonate and organic fractions as a response to thermonuclear bomb-produced 14C in the atmosphere in the sixties of the 20th century. Anthropogenically produced 137Cs was also observed in sediment profiles. Sedimentation rates for both lake sediments were estimated based on the unsupported 210Pb activity. Different 14C activity of the carbonate fraction (63-80 pMC, percent of modern carbon) and organic fraction (82-93 pMC) is the result of geochemical and biological processes of the sediment precipitation in the lake waters. This is also confirmed by the δ 13 C values of both fractions. Carbon isotope composition, a 14 C and δ 13 C, was compared with the lake sediments from the same lakes collected in 1989 and 2003.

Holocene record of glacier variability from lake sediments reveals tripartite climate history for Svalbard

NASA Astrophysics Data System (ADS)

van der Bilt, Willem; Bakke, Jostein; Vasskog, Kristian; D`Andrea, William; Bradley, Raymond; Olafsdottir, Sædis

2016-04-01

The Arctic is responding sensitively to ongoing global climate change, warming and moistening faster than any other region on the planet. Holocene proxy paleoclimate time series are increasingly used to put this amplified response in perspective by understanding Arctic climate processes beyond the instrumental period. Glaciers rapidly respond to climate shifts as demonstrated by their current demise around the world. This response has a composite climate signature, marked by shifts in hydroclimate (winter precipitation) as well as (summer) temperature. Attendant changes in glacier size are recorded by variations in glacigenic rock flour that may be deposited in downstream lakes. Here, we present a Holocene reconstruction of glacier activity, based on sediments from Hajeren, a glacier-fed lake on northwest Spitsbergen in the High Arctic Svalbard archipelago. Owing to undisturbed sediments and robust age control, we could resolve variability on a sub-centennial scale. To ensure the accurate detection of glacier activity, we applied a toolbox of physical, magnetic and geochemical proxies in conjunction with multivariate statistics. Our findings indicate a three-stage Holocene climate history for Svalbard, driving by melt water pulses, episodic Atlantic cooling and a decline in orbitally driven summer insolation. Correspondence between inferred advances, including a Holocene glacier maximum around 9.5 ka BP, suggests forcing by the melting LIS during the Early Holocene. Following a late Holocene Thermal Maximum around 7.4 ka BP, glaciers disappeared from the catchment. Glaciers reformed around 4.2 ka BP during the regional onset of the Neoglacial, supporting previous findings. This transition did, however, not mark the onset of persistent glacier activity in the catchment, but a series of centennial-scale cycles of growth and decay, including events around 3.3 and 1.1 ka BP. As orbitally driven insolation declined towards the present, the glaciation threshold

Spatiotemporal patterns of mercury accumulation in lake sediments of western North America

USGS Publications Warehouse

Drevnick, Paul; Cooke, Colin A.; Barraza, Daniella; Blais, Jules M.; Coale, Kenneth; Cumming, Brian F.; Curtis, Chris; Das, Biplob; Donahue, William F.; Eagles-Smith, Collin A.; Engstrom, Daniel R.; Fitzgerald, William F.; Furl, Chad V.; Gray, John R.; Hall, Roland I.; Jackson, Togwell A.; Laird, Kathleen R.; Lockhart, W. Lyle; Macdonald, Robie W.; Mast, M. Alisa; Mathieu, Callie; Muir, Derek C.G.; Outridge, Peter; Reinemann, Scott; Rothenberg, Sarah E.; Ruiz-Fernandex, Ana Carolina; St. Louis, V.L.; Sanders, Rhea; Sanei, Hamed; Skierszkan, Elliott; Van Metre, Peter C.; Veverica, Timothy; Wiklund, Johan A.; Wolfe, Brent B.

2016-01-01

For the Western North America Mercury Synthesis, we compiled mercury records from 165 dated sediment cores from 138 natural lakes across western North America. Lake sediments are accepted as faithful recorders of historical mercury accumulation rates, and regional and sub-regional temporal and spatial trends were analyzed with descriptive and inferential statistics. Mercury accumulation rates in sediments have increased, on average, four times (4×) from 1850 to 2000 and continue to increase by approximately 0.2 μg/m2 per year. Lakes with the greatest increases were influenced by the Flin Flon smelter, followed by lakes directly affected by mining and wastewater discharges. Of lakes not directly affected by point sources, there is a clear separation in mercury accumulation rates between lakes with no/little watershed development and lakes with extensive watershed development for agricultural and/or residential purposes. Lakes in the latter group exhibited a sharp increase in mercury accumulation rates with human settlement, stabilizing after 1950 at five times (5×) 1850 rates. Mercury accumulation rates in lakes with no/little watershed development were controlled primarily by relative watershed size prior to 1850, and since have exhibited modest increases (in absolute terms and compared to that described above) associated with (regional and global) industrialization. A sub-regional analysis highlighted that in the ecoregion Northwestern Forest Mountains, <1% of mercury deposited to watersheds is delivered to lakes. Research is warranted to understand whether mountainous watersheds act as permanent sinks for mercury or if export of “legacy” mercury (deposited in years past) will delay recovery when/if emissions reductions are achieved.

A diatom record of climate and hydrology for the past 200 KA from Owens Lake, California with comparison to other Breat Basin records

USGS Publications Warehouse

Bradbury, J.P.

1997-01-01

Diatoms from lake sediments beneath Owens Lake playa, Inyo County, California, document a nearly continuous paleolimnological record of climate and hydrologic change since the penultimate glacial-interglacial cycle based on a chronology established by radiocarbon, tephrochronology, and paleomagnetic control. Freshwater planktic diatoms (especially species of Stephanodiscus), plagioclase feldspar-rich sediments with high magnetic susceptibility, and Juniperus-type pollen characterized the penultimate glaciation at Owens Lake. Saline diatoms dominated in the following interglacial period, and there are several episodes during which freshwater planktic diatoms became abundant between 100 and 50 ka that may represent interstadial climatic conditions. Saline diatoms fell to low values after 50 ka, but warm-season Aulacoseira species indicate episodes of significant summer precipitation in the hydrologic balance of Owens Lake prior to the last glacial maximum. By 25 ka, glacial environments were again characterized by abundant Juniperus, plagioclase feldspar, and Stephanodiscus species. Generally and Holocene climates were recorded in Owens Lake by short-term fluctuations of saline and freshwater diatoms, desiccation, and oolitic sediments barren of diatoms. Comparison to paleoclimate records both north and south of Owens Lake suggest a southerly displacement of storm tracks originating from the Aleutian Low during glacial episodes.

Modeled tephra ages from lake sediments, base of Redoubt Volcano, Alaska

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schiff, C J; Kaufman, D S; Wallace, K L

2007-02-25

A 5.6-m-long lake sediment core from Bear Lake, Alaska, located 22 km southeast of Redoubt Volcano, contains 67 tephra layers deposited over the last 8750 cal yr, comprising 15% of the total thickness of recovered sediment. Using 12 AMS {sup 14}C ages, along with the {sup 137}Cs and {sup 210}Pb activities of recent sediment, we evaluated different models to determine the age-depth relation of sediment, and to determine the age of each tephra deposit. The age model is based on a cubic smooth spline function that was passed through the adjusted tephra-free depth of each dated layer. The estimated agemore » uncertainty of the 67 tephras averages {+-} 105 yr (1{sigma}). Tephra-fall frequency at Bear Lake was among the highest during the past 500 yr, with eight tephras deposited compared to an average of 3.7 per 500 yr over the last 8500 yr. Other periods of increased tephra fall occurred 2500-3500, 4500-5000, and 7000-7500 cal yr. Our record suggests that Bear Lake experienced extended periods (1000-2000 yr) of increased tephra fall separated by shorter periods (500-1000 yr) of apparent quiescence. The Bear Lake sediment core affords the most comprehensive tephrochronology from the base of the Redoubt Volcano to date, with an average tephra-fall frequency of once every 130 yr.« less

A synthesis of post-glacial diatom records from Lake Baikal

USGS Publications Warehouse

Bradbury, J. Platt; Bezrukova, E.; Chernyaeva, G.; Colman, S.M.; Khursevich, G.; King, J.W.; Likoshway, Ye. V.

1994-01-01

The biostratigraphy of fossil diatoms contributes important chronologic, paleolimnologic, and paleoclimatic information from Lake Baikal in southeastern Siberia. Diatoms are the dominant and best preserved microfossils in the sediments, and distinctive assemblages and species provide inter-core correlations throughout the basin at millennial to centennial scales, in both high and low sedimentation-rate environments. Distributions of unique species, once dated by radiocarbon, allow diatoms to be used as dating tools for the Holocene history of the lake.Diatom, pollen, and organic geochemical records from site 305, at the foot of the Selenga Delta, provide a history of paleolimnologic and paleoclimatic changes from the late glacial (15 ka) through the Holocene. Before 14 ka diatoms were very rare, probably because excessive turbidity from glacial meltwater entering the lake impeded productivity. Between 14 and 12 ka, lake productivity increased, perhaps as strong winds promoted deep mixing and nutrient regeneration. Pollen evidence suggests a cold shrub — steppe landscape dominated the central Baikal depression at this time. As summer insolation increased, conifers replaced steppe taxa, but diatom productivity declined between 11 and 9 ka perhaps as a result of increased summer turbidity resulting from violent storm runoff entering the lake via short, steep drainages. After 8 ka, drier, but more continental climates prevailed, and the modern diatom flora of Lake Baikal came to prominence.On Academician Ridge, a site of slow sedimentation rates, Holocene diatom assemblages at the top of 10-m cores reappear at deeper levels suggesting that such cores record at least two previous interglacial (or interstadial?) periods. Nevertheless, distinctive species that developed prior to the last glacial period indicate that the dynamics of nutrient cycling in Baikal and the responsible regional climatic environments were not entirely analogous to Holocene conditions. During

Anthropopression markers in lake bottom sediments

NASA Astrophysics Data System (ADS)

Nadolna, Anna; Nowicka, Barbara

2014-05-01

Lakes are vulnerable to various types of anthropogenic disturbances. Responses of lake ecosystems to environmental stressors are varied and depend not only on the type of a factor but also on the lake natural resistance to degradation. Within the EULAKES project an evaluation of anthropogenic stress extent in a flow-through, postglacial, ribbon lake (Lake Charzykowskie) was carried out. It was assumed, that this impact manifests unevenly, depending on a type and degree of the pressure on the shore zones, water quality of tributaries, lake basin shape and dynamics of a water movement. It was stated, that anthropogenic markers are substances accumulated in bottom sediments as a result of allochthonous substances inflow from the catchment and atmosphere. Along the selected transects 105 samples from the top layer of sediments (about 20 cm) was collected representing the contemporary accumulation (about 15 years). The content of selected chemical elements and compounds was examined, including nutrients (TN and TP), heavy metals (arsenic, cadmium, lead, chromium, nickel, copper, zinc, mercury, iron, and manganese) and pesticides (DDT, DDD, DDE, DMDT , γ-HCH). The research was conducted in the deepest points of each lake basin and along the research transects - while choosing the spots, the increased intensity of anthropogenic impact (ports, roads with heavy traffic, wastewater discharge zones, built-up areas) was taken into consideration. The river outlets to the lake, where there are ecotonal zones between limnic and fluvial environment, were also taken into account. Analysis of the markers distribution was carried out against the diversity of chemical characteristics of limnic sediments. Ribbon shape of the lake basin and the dominant wind direction provide an opportunity of easy water mixing to a considerable depth. Intensive waving processes cause removal of the matter from the littoral zone towards lake hollows (separated by the underwater tresholds), where the

Testing the apatite depletion hypothesis for early Holocene ecosystem acidification using the lake sediment record at Krâkenes, Norway.

NASA Astrophysics Data System (ADS)

Thrasher, I. M.; Boyle, J. F.; Chiverrell, R. C.; Plater, A. J.

2009-04-01

Lakes created by retreating ice at the end of the last glaciation underwent rapid acidification during the first few thousand years of their existence, a phenomenon that has been attributed in part to progressive leaching of soil bases since it was discovered more than 80 years ago. Though a role for leaching is still acknowledged, the most recent studies see this as subordinate to the effects of biological and climatic changes initiated by deglaciation, chiefly primary vegetation succession and species immigration. However, we propose a simpler alternative explanation, based on the geochemical modelling of runoff acidity. This shows that the extent and timing of early Holocene lake acidification in eight published palaeoecological records can be explained by leaching of the calcium phosphate mineral apatite from the granitic till soils of their catchments, at a rate controlled by simple dissolution kinetic factors. If confirmed, this hypothesis has important implications for our understanding of long-term lake ecosystem development. Not only does it mean that the mechanism is inherently irreversible, in contrast to the alternative ecological and climatic mechanisms which are not. Also, it reinforces the view that long-term ecosystem modelling cannot safely neglect nutrient limitation, as is currently the practice in widely used global dynamic vegetation models. Here we present a NERC-funded programme of research that uses the sediment mineral record of Kråkenes (western Norway), the best studied early Holocene lake sediment sequence in the world, to provide a simple, critical and unambiguous test of this hypothesis.

A Composite Depth Scale for Sediments from Crevice Lake, Montana

USGS Publications Warehouse

Rosenbaum, J.G.; Skipp, G.; Honke, J.; Chapman, C.

2010-01-01

As part of a study to derive records of past environmental change from lake sediments in the western United States, a set of cores was collected from Crevice Lake, Montana, in late February and early March 2001. Crevice Lake (latitude 45.000N, longitude 110.578W, elevation 1,713 meters) lies adjacent to the Yellowstone River at the north edge of Yellowstone National Park. The lake is more than 31 meters deep and has a surface area of 7.76 hectares. The combination of small surface area and significant depth promote anoxic bottom-water conditions that preserve annual laminations (varves) in the sediment. Three types of cores were collected through the ice. The uppermost sediments were obtained in freeze cores that preserved the sediment water interface. Two sites were cored with a 5-centimeter diameter corer. Five cores were taken with a 2-meter-long percussion piston corer. The percussion core uses a plastic core liner with an inside diameter of 9 centimeters. Coring was done at two sites. Because of the relatively large diameter of the percussion cores, samples from these cores were used for a variety of analyses including pollen, charcoal, diatoms, stable isotopes, organic and inorganic carbon, elemental analyses, and magnetic properties.

Interannual variation in seasonal diatom dynamics - what information is preserved in an annual sediment record?

NASA Astrophysics Data System (ADS)

Maier, D. B.; Bigler, C.; Diehl, S.

2017-12-01

Diatom sediment assemblages are among the most important proxies for past climate and ecological condition reconstruction in aquatic environments, but the role of seasonality in the formation of diatom records is poorly understood. In this study we combine the diatom record of a varved sediment with year-round physico-chemical water column monitoring and the corresponding sequential sediment trap diatom record to disentangle the process information contained in a diatom sediment signal. The comparison of three consecutive annual diatom records indicates that the entire annual diatom sediment signal can be driven by winter air temperature induced timing of ice and snow melt and persistent under-ice stratification promoting an early diatom bloom under ice before spring lake over-turn. By contrast, in a year of late ice thinning when the chlorophyll a maximum occurred after spring lake over-turn, a more annually integrated diatom sediment signal was built buy a continuous diatom flux. The contrasting diatom records produced during years of different winter conditions have important implications for diatom based paleoecological reconstructions. Decadal records of sediment trap samples as well as long-term varved sediment records provide further support for the role of late winter and early spring weather conditions in determining sediment diatom assemblages.

Lake sedimentary DNA accurately records 20th Century introductions of exotic conifers in Scotland.

PubMed

Sjögren, Per; Edwards, Mary E; Gielly, Ludovic; Langdon, Catherine T; Croudace, Ian W; Merkel, Marie Kristine Føreid; Fonville, Thierry; Alsos, Inger Greve

2017-01-01

Sedimentary DNA (sedDNA) has recently emerged as a new proxy for reconstructing past vegetation, but its taphonomy, source area and representation biases need better assessment. We investigated how sedDNA in recent sediments of two small Scottish lakes reflects a major vegetation change, using well-documented 20 th Century plantations of exotic conifers as an experimental system. We used next-generation sequencing to barcode sedDNA retrieved from subrecent lake sediments. For comparison, pollen was analysed from the same samples. The sedDNA record contains 73 taxa (mainly genus or species), all but one of which are present in the study area. Pollen and sedDNA shared 35% of taxa, which partly reflects a difference in source area. More aquatic taxa were recorded in sedDNA, whereas taxa assumed to be of regional rather than local origin were recorded only as pollen. The chronology of the sediments and planting records are well aligned, and sedDNA of exotic conifers appears in high quantities with the establishment of plantations around the lakes. SedDNA recorded other changes in local vegetation that accompanied afforestation. There were no signs of DNA leaching in the sediments or DNA originating from pollen. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

Magnetic Signature of Glacial Flour in Sediments From Bear Lake, Utah/Idaho

NASA Astrophysics Data System (ADS)

Rosenbaum, J. G.; Dean, W. E.; Colman, S. M.; Reynolds, R. L.

2002-12-01

Variations in magnetic properties within an interval of Bear Lake sediments correlative with oxygen isotope stage 2 (OIS 2) and OIS 3 provide a record of glacial flour production for the Uinta Mountains. Like sediments of the same age from Upper Klamath Lake (OR), these Bear Lake sediments have high magnetic susceptibilities (MS) relative to non-glacial-age sediments and contain well-defined millennial-scale variations in magnetic properties. In contrast to glacial flour derived from volcanic rocks surrounding Upper Klamath Lake, glacial flour derived from the Uinta Mountains and deposited in Bear Lake by the Bear River has low magnetite content but high hematite content. The relatively low MS values of younger and older non-glacial-age sediments are due entirely to dilution by non-magnetic endogenic carbonate and to the effects of sulfidic alteration of detrital Fe-oxides. Analysis of samples from streams entering Bear Lake and from along the course of the Bear River demonstrates that, in comparison to other areas of the catchment, sediment derived from the Uinta Mountains is rich in hematite (high HIRM) and aluminum, and poor in magnetite (low MS) and titanium. Within the glacial-age lake sediments, there are strong positive correlations among HIRM, Al/Ti, and fine sediment grain size. MS varies inversely with theses three variables. These relations indicate that the observed millennial-scale variations in magnetic and chemical properties arise from varying proportions of two detrital components: (1) very fine-grained glacial flour derived from Proterozoic metasedimentary rocks in the Uinta Mountains and characterized by high HIRM and low MS, and (2) somewhat coarser material, characterized by higher MS and lower HIRM, derived from widespread sedimentary rocks along the course of the Bear River and around Bear Lake. Measurement of glacial flour incorporated in lake sediments can provide a continuous history of alpine glaciation, because the rate of accumulation

Sediment deposition and selected water-quality characteristics in Cedar Lake and Lake Olathe, Northeast Kansas, 2000

USGS Publications Warehouse

Mau, D.P.

2002-01-01

The Lake Olathe watershed, located in northeast Kansas, was investigated using bathymetric survey data and reservoir bottom-sediment cores to determine sediment deposition, water-quality trends, and transport of nutrients (phosphorus and nitrogen species), selected trace elements, selected pesticides, and diatoms as indicators of eutrophic (organic-enriched and depleted oxygen supply) conditions. To determine sediment deposition and loads, bathymetric data from Cedar Lake and Lake Olathe, both located in the Lake Olathe watershed, were collected in 2000 and compared to historical topographic data collected when the lakes were built. Approximately 338 acre-feet of sediment deposition has occurred in Cedar Lake since dam closure in 1938, and 317 acre-feet has occurred at Lake Olathe since 1956. Mean annual sediment deposition was 5.45 acre-feet per year (0.89 acre-feet per year per square mile) for Cedar Lake and 7.0 acre-feet per year (0.42 acre-feet per year per square mile) for Lake Olathe. Mean annual sediment loads for the two reservoirs were 9.6 million pounds per year for Cedar Lake and 12.6 million pounds per year for Lake Olathe. Mean concentrations of total phosphorus in bottom-sediment samples from Cedar Lake ranged from 1,370 to 1,810 milligrams per kilogram, and concentrations in bottom-sediment samples from Lake Olathe ranged from 588 to 1,030 milligrams per kilogram. The implication of large total phosphorus concentrations in the bottom sediment of Cedar Lake is that inflow into Cedar Lake is rich in phosphorus and that adverse water-quality conditions could affect water quality in downstream Lake Olathe through discharge of water from Cedar Lake to Lake Olathe via Cedar Creek. Mean annual phosphorus loads transported from the Lake Olathe watershed were estimated to be 14,700 pounds per year for Cedar Lake and 9,720 pounds per year for Lake Olathe. The mean annual phosphorus yields were estimated to be 3.74 pounds per acre per year for Cedar Lake and 0

Phosphorus geochemistry of recent sediments in the South Basin of Lake Winnipeg

USGS Publications Warehouse

Mayer, T.; Simpson, S.L.; Thorleifson, L.H.; Lockhart, W.L.; Wilkinson, Philip M.

2006-01-01

Lake Winnipeg supports the largest commercial fishery on Canadian Prairies. It has been influenced by a variety of environmental forces and anthropogenic activities. To gain a better understanding of recent changes in nutrient status of the lake, it is important to reconstruct its previous history from sedimentary records. Lacustrine sediments are known to be an important sink of many dissolved and suspended substances, including phosphorus, hence, they provide a permanent historical record of changes occurring in the lake. These changes may be induced by natural factors or by anthropogenic activities in the watershed. Phosphorus profiles from dated sediment cores collected in 1999 and 1994 from the South Basin of Lake Winnipeg were investigated to determine phosphorus enrichment in recent sediments. To interpret the nutrient status and depositional conditions responsible for the trends in total phosphorus, three operationally defined forms of phosphorus (P) were determined: non-apatite inorganic P, apatite P, and organic P. Significant increases in sediment phosphorus concentrations were observed in the uppermost 20 cm of the cores and several anomalies were observed at depth. A doubling in total phosphorus relative to aluminum over the last fifty years is largely due to increases in the non-apatite inorganic fraction, suggesting that much of sedimentary phosphorus increase is attributable to changes in the nutrient status of the water column related to anthropogenic inputs. Organic phosphorus exhibits a subtle increase in the upper 20 cm of the gravity cores, likely due to increases in the primary productivity of the lake. Except for the slight increase in deeper sediments, apatite phosphorus, which is thought to be of detrital origin, remained fairly constant over the length of the cores. Anomalous spikes in phosphorus concentrations deeper in the cores, comprised mainly of the non-apatite inorganic phosphorus fraction, likely resulted from natural variation in

Interpreting the Holocene fluctuations of Quelccaya Ice Cap, Peru: using a combination of glacial and non-glacial lake records

NASA Astrophysics Data System (ADS)

Stroup, J. S.; Kelly, M. A.; Lowell, T. V.; Smith, C.; Beal, S. A., Jr.; Tapia, P. M.

2016-12-01

The past fluctuations of Quelccaya Ice Cap (QIC) are an indicator of tropical paleoclimate. At QIC, ice core and glacial geological records provide late Holocene climate constraints. However, early and middle Holocene QIC fluctuations are less well-known. To interpret past QIC fluctuations, we present Holocene-long lake sediment records from Challpacocha, a lake fed by QIC meltwater, and Yanacocha, a lake that has not received meltwater during the Holocene. To assess the clastic sediment delivered to Challpacocha by QIC meltwater, we compare visual stratigraphy, X-ray fluorescence chemistry, grainsize, loss on ignition and clastic flux records from both lakes (additional Yanacocha proxies are presented by Axford et al. (this meeting, abstract 157985)). We compare the meltwater derived clastic sediment record from Challpacocha with moraine and stratigraphic records of past ice extents during the late Holocene. This comparison indicates that clastic sediment flux in Challpacocha increased during QIC recession and decreased during QIC advance, or significantly reduced QIC extent. We then use the Challpacocha clastic sediment record to interpret early and middle Holocene QIC fluctuations. Based on the Challpacocha sediment record, combined with prior work, we suggest that from 11 to 6.5 ka QIC was similar to or smaller than its late Holocene extent. From 6.9 to 6.5 ka QIC may have been absent from the landscape. At 3-2.4 and 0.62-0.31 ka QIC experienced the most extensive Holocene fluctuations. We compare the clastic sediment fluxes from Challpacocha and Pacococha (a nearby lake fed by QIC; Rodbell et al., 2008) to infer QIC expansion between 6.5-5 ka. This is supported by 14C ages of in-situ subfossil plants which indicate ice advance at 6.3-4.7 ka (Thompson et al., 2006, 2013; Buffen et al., 2009). Our study highlights the value of using multiple datasets to improve lake sediment record interpretations.

Repeated sedimentation and exposure of glacial Lake Missoula sediments: A lake-level history at Garden Gulch, Montana, USA

NASA Astrophysics Data System (ADS)

Smith, Larry N.

2017-01-01

Glaciolacustrine sediments record lake transgression, regression, and subaerial modification of the silty lake-bottom of glacial Lake Missoula in the Clark Fork River valley. The sequence preserved at Garden Gulch, MT documents lake-level fluctuations at >65% of its full-pool volume. Twelve sedimentary cycles fine upwards from (1) very fine-grained sandy silt to (2) silt with climbing ripples to (3) rhythmically laminated silt and some clay. The cycles are fine-grained turbidites capped locally by thin layers of angular gravel derived from local bedrock outcrops. The gravels appear to be the toes of mass wasting lobes carried onto the exposed lakebed surface during repeated lake-level lowerings. Periglacial wedges, small rotational faults, involutions, and clastic dikes deform the tops of eleven cycles. The wedges are 10-30 cm wide, penetrate 30-70 cm deep, are spaced <1 m apart, and contain vertically oriented gravel and massive to laminated sediment. Wedges split and taper in plan view. A few thin silt-filled dikes, which branch and taper downwards from wedges, are interpreted as filled frost cracks. One 10-20 cm-wide sand-filled dike protrudes upward from a sand bed; it is interpreted as a liquefaction feature consistent with a filling and draining lake. The deformed cycle tops preserve evidence of periglacial cold, subaerial exposure, seasonal frost heave, and the incipient formation of sorted polygons. The lowest five cycles are thicker and display more periglacial modification at their tops than the upper seven cycles. The Garden Gulch section may represent as few as seven and as many as twelve substantial fillings and partial to complete drainings of glacial Lake Missoula.

Lake sediments record prehistoric lead pollution related to early copper production in North America.

PubMed

Pompeani, David P; Abbott, Mark B; Steinman, Byron A; Bain, Daniel J

2013-06-04

The mining and use of copper by prehistoric people on Michigan's Keweenaw Peninsula is one of the oldest examples of metalworking. We analyzed the concentration of lead, titanium, magnesium, iron, and organic matter in sediment cores recovered from three lakes located near mine pits to investigate the timing, location, and magnitude of ancient copper mining pollution. Lead concentrations were normalized to lithogenic metals and organic matter to account for processes that can influence natural (or background) lead delivery. Nearly simultaneous lead enrichments occurred at Lake Manganese and Copper Falls Lake ∼8000 and 7000 years before present (yr BP), indicating that copper extraction occurred concurrently in at least two locations on the peninsula. The poor temporal coherence among the lead enrichments from ∼6300 to 5000 yr BP at each lake suggests that the focus of copper mining and annealing shifted through time. In sediment younger than ∼5000 yr BP, lead concentrations remain at background levels at all three lakes, excluding historic lead increases starting ∼150 yr BP. Our work demonstrates that lead emissions associated with both the historic and Old Copper Complex tradition are detectable and can be used to determine the temporal and geographic pattern of metal pollution.

[Limnology of high mountain tropical lake, in Ecuador: characteristics of sediments and rate of sedimentation].

PubMed

Gunkel, Günter

2003-06-01

Equatorial high mountain lakes are a special type of lake occurring mainly in the South American Andes as well as in Central Africa and Asia. They occur at altitudes of a few thousand meters above sea level and are cold-water lakes (< 20 degrees C). Relatively little is known about them. A long-term limnological study was therefore undertaken at Lake San Pablo, Ecuador, to analyze the basic limnological processes of the lake, which has a tendency for eutrophication. Sediment quality of San Pablo Lake is given under consideration of horizontal and vertical distribution using sediment cores. Significance of sediments for eutrophication process of lakes is demonstrated using phosphorus concentration of sediments as well as the phosphorus retention capacity of the sediments by ratio Fe/P. Dating of the sediments is done using 137Cs and 210Pb, but the activity of 137Cs in the sediment was very low nearly at the detection level. Sedimentation rate is determined to be 3.5 mm/year and the sediment cores represent about 110 years. P concentration of the sediments is high (approximately 5 g/kg dry substance), and P retention capacity by Fe is insufficient (Fe/P = 4). The sediment quality did not change significantly during the past decades, and the trophic state of San Pablo Lake was already less or more eutrophic 110 years ago. The contamination of the lake sediments by heavy metals is insignificant.

A comparison of sedimentary DNA and pollen from lake sediments in recording vegetation composition at the Siberian treeline.

PubMed

Niemeyer, Bastian; Epp, Laura S; Stoof-Leichsenring, Kathleen R; Pestryakova, Luidmila A; Herzschuh, Ulrike

2017-11-01

Reliable information on past and present vegetation is important to project future changes, especially for rapidly transitioning areas such as the boreal treeline. To study past vegetation, pollen analysis is common, while current vegetation is usually assessed by field surveys. Application of detailed sedimentary DNA (sedDNA) records has the potential to enhance our understanding of vegetation changes, but studies systematically investigating the power of this proxy are rare to date. This study compares sedDNA metabarcoding and pollen records from surface sediments of 31 lakes along a north-south gradient of increasing forest cover in northern Siberia (Taymyr peninsula) with data from field surveys in the surroundings of the lakes. sedDNA metabarcoding recorded 114 plant taxa, about half of them to species level, while pollen analyses identified 43 taxa, both exceeding the 31 taxa found by vegetation field surveys. Increasing Larix percentages from north to south were consistently recorded by all three methods and principal component analyses based on percentage data of vegetation surveys and DNA sequences separated tundra from forested sites. Comparisons of the ordinations using procrustes and protest analyses show a significant fit among all compared pairs of records. Despite similarities of sedDNA and pollen records, certain idiosyncrasies, such as high percentages of Alnus and Betula in all pollen and high percentages of Salix in all sedDNA spectra, are observable. Our results from the tundra to single-tree tundra transition zone show that sedDNA analyses perform better than pollen in recording site-specific richness (i.e., presence/absence of taxa in the vicinity of the lake) and perform as well as pollen in tracing vegetation composition. © 2017 John Wiley & Sons Ltd.

Record of seismotectonic events in siliceous cyanobacterial sediments (Magadi cherts), Lake Magadi, Kenya

NASA Astrophysics Data System (ADS)

Behr, H.-J.; Röhricht, C.

The Quaternary sediments of Lake Magadi in the Kenya Rift include large volumes of chert. Before their lithification, these siliceous sediments underwent very strong deformation, as recorded by diapirism with pillow-chert mounds, extrusion along dykes and fault ramps, horizontal liquefaction slides with brecciation, slumping, as well as petee-, flow- and shear structures. Eugster (1969) considered these structures to have resulted from desiccation of Na-silicate precipitates (magadiite) that were deposited over wide areas and were several metres thick. Magadiite can remain soft over long periods; therefore, these ``Magadi-type cherts'' are called the type examples of inorganic cherts. However, field observations and microbiological studies of the cherts show that real inorganic cherts are rare at the type locality of Magadi-type cherts. Most of the cherts are older than the High Magadi Beds and developed from flat-topped calcareous bioherms of Pleurocapsa, Gloecocapsa, and other coccoid cyanobacteria, thinly bedded filamentous microbial mats, stromatolites, bacterial slimes, diatoms, Dascladiacea colonies and other organic matter. Silicification occurred from a silicasol via opal-A to opal-C with final recrystallisation to a chert of quartzine composition. The metabolic processes of cyanobacteria controlled the pH and influenced the dissolution-precipitation mechanism. Collapse, liquefaction and extrusion of the pre-lithified siliceous matrix was caused by seismotectonic rift activity, which activated fault scarplets and large-scale dyke systems. It led to liquefaction and other earthquake-induced structures along the fault ramps and on tilted blocks. Concentrated silicasols were generated by the interaction of alkaline waters with volcanic detritus, coupled with biochemical processes. After liquefaction and extrusion, the material solidified by spontaneous crystallisation in an environment that was characterised by highly variable pH and salinity. The Lake Magadi

Multi-Elements in Waters and Sediments of Shallow Lakes: Relationships with Water, Sediment, and Watershed Characteristics.

PubMed

Kissoon, La Toya T; Jacob, Donna L; Hanson, Mark A; Herwig, Brian R; Bowe, Shane E; Otte, Marinus L

2015-06-01

We measured concentrations of multiple elements, including rare earth elements, in waters and sediments of 38 shallow lakes of varying turbidity and macrophyte cover in the Prairie Parkland (PP) and Laurentian Mixed Forest (LMF) provinces of Minnesota. PP shallow lakes had higher element concentrations in waters and sediments compared to LMF sites. Redundancy analysis indicated that a combination of site- and watershed-scale features explained a large proportion of among-lake variability in element concentrations in lake water and sediments. Percent woodland cover in watersheds, turbidity, open water area, and macrophyte cover collectively explained 65.2 % of variation in element concentrations in lake waters. Sediment fraction smaller than 63 µm, percent woodland in watersheds, open water area, and sediment organic matter collectively explained 64.2 % of variation in element concentrations in lake sediments. In contrast to earlier work on shallow lakes, our results showed the extent to which multiple elements in shallow lake waters and sediments were influenced by a combination of variables including sediment characteristics, lake morphology, and percent land cover in watersheds. These results are informative because they help illustrate the extent of functional connectivity between shallow lakes and adjacent lands within these lake watersheds.

Multi-Elements in Waters and Sediments of Shallow Lakes: Relationships with Water, Sediment, and Watershed Characteristics

PubMed Central

Jacob, Donna L.; Hanson, Mark A.; Herwig, Brian R.; Bowe, Shane E.; Otte, Marinus L.

2015-01-01

We measured concentrations of multiple elements, including rare earth elements, in waters and sediments of 38 shallow lakes of varying turbidity and macrophyte cover in the Prairie Parkland (PP) and Laurentian Mixed Forest (LMF) provinces of Minnesota. PP shallow lakes had higher element concentrations in waters and sediments compared to LMF sites. Redundancy analysis indicated that a combination of site- and watershed-scale features explained a large proportion of among-lake variability in element concentrations in lake water and sediments. Percent woodland cover in watersheds, turbidity, open water area, and macrophyte cover collectively explained 65.2 % of variation in element concentrations in lake waters. Sediment fraction smaller than 63 µm, percent woodland in watersheds, open water area, and sediment organic matter collectively explained 64.2 % of variation in element concentrations in lake sediments. In contrast to earlier work on shallow lakes, our results showed the extent to which multiple elements in shallow lake waters and sediments were influenced by a combination of variables including sediment characteristics, lake morphology, and percent land cover in watersheds. These results are informative because they help illustrate the extent of functional connectivity between shallow lakes and adjacent lands within these lake watersheds. PMID:26074657

The nuclear bomb carbon curve recorded in tree-rings and lake sediments near Taal Volcano, Central Philippines

NASA Astrophysics Data System (ADS)

Liou, M. S.; Li, H. C.; Huang, S. K.; Guan, B. T.

2017-12-01

Dendrochronologies built from precisely dated annual rings have shown to record the regional bomb pulse and the C-14 concentration variations caused by local events. In this study, we collected teak trees Tectona grandis near the Lake Taal, Central Philippines in 2011 for dendrochronological analysis and radiocarbon dating. The tree-ring sample contains 90 rings dated from 1922 to 2011. Currently, 28 selected subsamples have been measured by AMS 14C on bulk carbon with a few samples on holocellulose. The 14C results of the samples indicate that: 1) the results of AMS 14C dating between holocellulose and whole wood from the same ring are similar, so we select whole wood for AMS 14C dating. 2) The nuclear bomb 14C pulse was clearly recorded in the Tectona grandis growth rings. The Δ14C values rose dramatically in 1960 and reached a maximum of 692‰ in 1966. The magnitude and the peak year of the bomb curve in the Tectona grandis tree-ring record are comparable to other published tree-ring records in the tropical regions. 3) The Δ14C values suddenly dropped in 1950, 1964 and 1968, probably affected by CO2 gas releasing due to the Taal volcanic activities. Further study on the tree-ring 14C dating will allow us to evaluate the bomb pulse trends more precisely, and the volcanic activities of Pinatubo and Taal Volcanoes. The tree-ring Δ14C record not only confirms existence of the bomb curve in Taal Lake area, but also allows us compare to the Δ14C record in the lake sediment for chronological construction. A 120-cm gravity core, TLS-2, collected from Lake Taal in 2008, shows the nuclear bomb carbon curve in the TOC of the core. However, the magnitude of the nuclear bomb 14C pulse in the TOC of TLS-2 is much lower than that in the tree-ring records, due to mixing effect of different organic carbon sources, smoothing effect of 14CO2 in multiple years plant growths, local old CO2 emission from volcanic activity, degassing from the lake bottom, and industrial and city

Identifying sediment discontinuities and solving dating puzzles using monitoring and palaeolimnological records

NASA Astrophysics Data System (ADS)

Dong, Xuhui; Sayer, Carl D.; Bennion, Helen; Maberly, Stephen C.; Yang, Handong; Battarbee, Richard W.

2016-12-01

Palaeolimnological studies should ideally be based upon continuous, undisturbed sediment sequences with reliable chronologies. However for some lake cores, these conditions are not met and palaeolimnologists are often faced with dating puzzles caused by sediment disturbances in the past. This study chooses Esthwaite Water from England to illustrate how to identify sedimentation discontinuities in lake cores and how chronologies can be established for imperfect cores by correlation of key sediment signatures in parallel core records and with long-term monitoring data (1945-2003). Replicated short cores (ESTH1, ESTH7, and ESTH8) were collected and subjected to loss-on-ignition, radiometric dating (210Pb, 137Cs, and 14C), particle size, trace metal, and fossil diatom analysis. Both a slumping and a hiatus event were detected in ESTH7 based on comparisons made between the cores and the long-term diatom data. Ordination analysis suggested that the slumped material in ESTH7 originated from sediment deposited around 1805-1880 AD. Further, it was inferred that the hiatus resulted in a loss of sediment deposited from 1870 to 1970 AD. Given the existence of three superior 14C dates in ESTH7, ESTH1 and ESTH7 were temporally correlated by multiple palaeolimnological proxies for age-depth model development. High variability in sedimentation rates was evident, but good agreement across the various palaeolimnological proxies indicated coherence in sediment processes within the coring area. Differences in sedimentation rates most likely resulted from the natural morphology of the lake basin. Our study suggests that caution is required in selecting suitable coring sites for palaeolimnological studies of small, relatively deep lakes and that proximity to steep slopes should be avoided wherever possible. Nevertheless, in some cases, comparisons between a range of contemporary and palaeolimnological records can be employed to diagnose sediment disturbances and establish a chronology.

Late Holocene Hydrologic Variability in the southeast Mojave Desert using sediments from Ford Lake, California

NASA Astrophysics Data System (ADS)

Leidelmeijer, J.; Kirby, M.; Anderson, W. T., Jr.; Mayer, S. A.; Palermo, J. A.; Stout, C.; Shellhorn, A.; Weisberg, G.; Rangel, H.; Hess, B.

2017-12-01

Most published lacustrine studies located in the Mojave Desert focus on lakes that receive the majority of their water from the Mojave River (e.g., Silver Lake, Cronese Lakes, Soda Lake, etc). Consequently, these Mojave River-fed lake sites record coastal hydroclimatic signals rather than a solely Mojave-only signal. The reason for this signal-disconnect is that the Mojave River is sourced in the San Bernardino Mountains, where annual precipitation is dictated by coastal hydroclimates. Therefore, much remains unknown about how the Mojave Desert changed during the Holocene at sub-millennial time scales. To address this problem and fill in an important geographical gap, we focus on Ford Lake in the southeastern Mojave Desert. Ford Lake is an internally drained, closed basin, and it is completely disconnected from the Mojave River. As a result, it represents one of the first lakes studied in the Mojave Desert with a climate signal that is 100% Mojave. Sediments from Ford Lake provide valuable context for understanding hydroclimatic variability exclusive to the Mojave Desert. To date, two hand-dug 1.5 m trenches (depocenter and littoral zone) and 3 overlapping sediments cores from the lake's depocenter have been sampled. The total core length is 3.55 m and bottomed in coarse alluvium, suggesting we captured the complete lacustrine sediment package. Initial results by Mayer (2016) focused on the most recent 1200 calendar years before present, or the upper 2.16 m. Mayer (2016) found evidence for increased run-off (wetter climate) during the Little Ice Age and reduced run-off (drier climate) during the Medieval Climatic Anomaly. Here, we complete the study, improving age control using sediment charcoal. Grain size, magnetic susceptibility, percent total organic matter, percent total carbonate content, C:N ratios and C and N isotopic analyses are (will be) measured at 1 cm contiguous intervals. The Ford Lake record has been (will be) compared to pre-existing regional

Unconsolidated sediments at the bottom of Lake Vostok from seismic data

USGS Publications Warehouse

Filina, I.; Lukin, V.; Masolov, V.; Blankenship, D.

2007-01-01

Seismic soundings of Lake Vostok have been performed by the Polar Marine Geological Research Expedition in collaboration with the Russian Antarctic Expedition since the early 1990s. The seismograms recorded show at least two relatively closely spaced reflections associated with the lake bottom. These were initially interpreted as boundaries of a layer of unconsolidated sediments at the bottom of the lake. A more recent interpretation suggests that the observed reflections are side echoes from the rough lake bottom, and that there are no unconsolidated sediments at the bottom of the lake. The major goal of this paper is to reveal the nature of those reflections by testing three hypotheses of their origin. The results show that some of the reflections, but not all of them, are consistent with the hypothesis of a non-flat lake bottom along the source-receiver line (2D case). The reflections were also evaluated as side echoes from an adjacent sloping interface, but these tests implied unreasonably steep slopes (at least 8 degrees) at the lake bottom. The hypothesis that is the most compatible with seismic data is the presence of a widespread layer of unconsolidated sediments at the bottom of Lake Vostok. The modeling suggests the presence of a two hundred meter thick sedimentary layer with a seismic velocity of 1700 -1900 m/sec in the southern and middle parts of the lake. The sedimentary layer thickens in the northern basin to ~350 m

Sediment oxygen profiles in a super-oxygenated antarctic lake

NASA Technical Reports Server (NTRS)

Wharton, R. A. Jr; Meyer, M. A.; McKay, C. P.; Mancinelli, R. L.; Simmons, G. M. Jr; Wharton RA, J. r. (Principal Investigator)

1994-01-01

Perennially ice-covered lakes are found in the McMurdo Dry Valleys of southern Victoria Land, Antarctica. In contrast to temperate lakes that have diurnal photic periods, antarctic (and arctic) lakes have a yearly photic period. An unusual feature of the antarctic lakes is the occurrence of O2 at supersaturated levels in certain portions of the water column. Here we report the first sediment O2 profiles obtained using a microelectrode from a perennially ice-covered antarctic lake. Sediment cores collected in January and October 1987 from Lake Hoare in Taylor Valley show oxygenation down to 15, and in some cases, 25 cm. The oxygenation of sediments several centimeters below the sediment-water interface is atypical for lake sediments and may be characteristic of perennially ice-covered lakes. There is a significant difference between the observed January and October sediment O2 profiles. Several explanations may account for the difference, including seasonality. A time-dependent model is presented which tests the feasibility of a seasonal cycle resulting from the long photoperiod and benthic primary production in sediments overlain by a highly oxygenated water column.

Modeled tephra ages from lake sediments, base of Redoubt Volcano, Alaska

USGS Publications Warehouse

Schiff, C.J.; Kaufman, D.S.; Wallace, K.L.; Werner, A.; Ku, T.-L.; Brown, T.A.

2008-01-01

A 5.6-m-long lake sediment core from Bear Lake, Alaska, located 22 km southeast of Redoubt Volcano, contains 67 tephra layers deposited over the last 8750 cal yr, comprising 15% of the total thickness of recovered sediment. Using 12 AMS 14C ages, along with the 137Cs and 210Pb activities of recent sediment, we evaluated different models to determine the age-depth relation of the core, and to determine the age of each tephra deposit. The selected age model is based on a mixed-effect regression that was passed through the adjusted tephra-free depth of each dated layer. The estimated age uncertainty of the 67 tephras averages ??105 yr (95% confidence intervals). Tephra-fall frequency at Bear Lake was among the highest during the past 500 yr, with eight tephras deposited compared to an average of 3.7/500 yr over the last 8500 yr. Other periods of increased tephra fall occurred 2500-3500, 4500-5000, and 7000-7500 cal yr. Our record suggests that Bear Lake experienced extended periods (1000-2000 yr) of increased tephra fall separated by shorter periods (500-1000 yr) of apparent quiescence. The Bear Lake sediment core affords the most comprehensive tephrochronology from the base of the Redoubt Volcano to date, with an average tephra-fall frequency of one every 130 yr. ?? 2007 Elsevier Ltd. All rights reserved.

A high-resolution, 60 kyr record of the relative geomagnetic field intensity from Lake Towuti, Indonesia

NASA Astrophysics Data System (ADS)

Kirana, Kartika Hajar; Bijaksana, Satria; King, John; Tamuntuan, Gerald Hendrik; Russell, James; Ngkoimani, La Ode; Dahrin, Darharta; Fajar, Silvia Jannatul

2018-02-01

Past changes in the Earth's magnetic field can be highlighted through reconstructions of magnetic paleointensity. Many magnetic field variation features are global, and can be used for the detailed correlation and dating of sedimentary records. On the other hand, sedimentary magnetic records also exhibit features on a regional, rather than a global scale. Therefore, the development of regional scale magnetic field reconstructions is necessary to optimize magnetic paleointensity dating. In this paper, a 60 thousand year (kyr) paleointensity record is presented, using the core TOW10-9B of Lake Towuti, located in the island of Sulawesi, Indonesia, as a part of the ongoing research towards understanding the Indonesian environmental history, and reconstructing a high-resolution regional magnetic record from dating the sediments. Located in the East Sulawesi Ophiolite Belt, the bedrock surrounding Lake Towuti consists of ultramafic rocks that render the lake sediments magnetically strong, creating challenges in the reconstruction of the paleointensity record. These sediment samples were subject to a series of magnetic measurements, followed by testing the obtained paleointensity records resulting from normalizing natural remanent magnetization (NRM) against different normalizing parameters. These paleointensity records were then compared to other regional, as well as global, records of magnetic paleointensity. The results show that for the magnetically strong Lake Towuti sediments, an anhysteretic remanent magnetization (ARM) is the best normalizer. A series of magnetic paleointensity excursions are observed during the last 60 kyr, including the Laschamp excursion at 40 kyr BP, that provide new information about the magnetic history and stratigraphy of the western tropical Pacific region. We conclude that the paleointensity record of Lake Towuti is reliable and in accordance with the high-quality regional and global trends.

Ephemerality of discrete methane vents in lake sediments

USGS Publications Warehouse

Scandella, Benjamin P.; Pillsbury, Liam; Weber, Thomas; Ruppel, Carolyn D.; Hemond, Harold F.; Juanes, Ruben

2016-01-01

Methane is a potent greenhouse gas whose emission from sediments in inland waters and shallow oceans may both contribute to global warming and be exacerbated by it. The fraction of methane emitted by sediments that bypasses dissolution in the water column and reaches the atmosphere as bubbles depends on the mode and spatiotemporal characteristics of venting from the sediments. Earlier studies have concluded that hot spots—persistent, high-flux vents—dominate the regional ebullitive flux from submerged sediments. Here the spatial structure, persistence, and variability in the intensity of methane venting are analyzed using a high-resolution multibeam sonar record acquired at the bottom of a lake during multiple deployments over a 9 month period. We confirm that ebullition is strongly episodic, with distinct regimes of high flux and low flux largely controlled by changes in hydrostatic pressure. Our analysis shows that the spatial pattern of ebullition becomes homogeneous at the sonar's resolution over time scales of hours (for high-flux periods) or days (for low-flux periods), demonstrating that vents are ephemeral rather than persistent, and suggesting that long-term, lake-wide ebullition dynamics may be modeled without resolving the fine-scale spatial structure of venting.

Lake sediment isotope records of hydroclimatic changes in the Pacific Northwest over the last two thousand years

NASA Astrophysics Data System (ADS)

Steinman, B. A.; Abbott, M.; Mann, M. E.; Ortiz, J. D.

2012-12-01

Recent drought conditions and greater water demand caused by population expansion are placing increasing stress on the ecosystems and economies of western North America. Variations in drought frequency and intensity in this region are primarily controlled by the El Niño Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO), which affect precipitation and temperature on interannual to centennial timescales. During the Little Ice Age (LIA) and Medieval Climate Anomaly (MCA) the tropical Pacific Ocean was likely characterized by shifts toward more El Niño and La Niña like mean state conditions, respectively, which produced changes in water availability that have no historic precedent. Here we report isotopic evidence (sediment δ18O records) from 9 lakes in the southern Yukon, central British Columbia, and the northwestern United States indicating that the LIA was a time of exceptional dryness in the Pacific Northwest and that the MCA was relatively wetter. We compare the lake sediment isotope data to synoptic ocean-atmosphere paleoproxy datasets as well as records of external forcing (i.e., solar and volcanic) that span the last 1-2 thousand years to ascertain the influence of climate system responses to external forcing on precipitation-evaporation balance in western North America. Modeling and proxy data comparisons have described links between the mean state of the tropical Pacific Ocean and radiative forcing on multi-decadal to centennial time scales during the middle and late Holocene. Analysis of proxy data including tree rings and speleothems have documented connections between inferred solar activity maxima, La Niña like conditions in the tropical Pacific and reduced water availability in the American southwest. Lake sediment δ18O data from the Pacific Northwest evince a pattern opposite that of the southwest in which periods of greater solar activity correspond with wetter hydroclimatic conditions, and vice versa, similar to the observed

Archaeal community changes in Lateglacial lake sediments: Evidence from ancient DNA

NASA Astrophysics Data System (ADS)

Ahmed, Engy; Parducci, Laura; Unneberg, Per; Ågren, Rasmus; Schenk, Frederik; Rattray, Jayne E.; Han, Lu; Muschitiello, Francesco; Pedersen, Mikkel W.; Smittenberg, Rienk H.; Yamoah, Kweku Afrifa; Slotte, Tanja; Wohlfarth, Barbara

2018-02-01

The Lateglacial/early Holocene sediments from the ancient lake at Hässeldala Port, southern Sweden provide an important archive for the environmental and climatic shifts at the end of the last ice age and the transition into the present Interglacial. The existing multi-proxy data set highlights the complex interplay of physical and ecological changes in response to climatic shifts and lake status changes. Yet, it remains unclear how microorganisms, such as Archaea, which do not leave microscopic features in the sedimentary record, were affected by these climatic shifts. Here we present the metagenomic data set of Hässeldala Port with a special focus on the abundance and biodiversity of Archaea. This allows reconstructing for the first time the temporal succession of major Archaea groups between 13.9 and 10.8 ka BP by using ancient environmental DNA metagenomics and fossil archaeal cell membrane lipids. We then evaluate to which extent these findings reflect physical changes of the lake system, due to changes in lake-water summer temperature and seasonal lake-ice cover. We show that variations in archaeal composition and diversity were related to a variety of factors (e.g., changes in lake water temperature, duration of lake ice cover, rapid sediment infilling), which influenced bottom water conditions and the sediment-water interface. Methanogenic Archaea dominated during the Allerød and Younger Dryas pollen zones, when the ancient lake was likely stratified and anoxic for large parts of the year. The increase in archaeal diversity at the Younger Dryas/Holocene transition is explained by sediment infilling and formation of a mire/peatbog.

Sedimentological characteristics of lake sediment of the Lake Jelonek (North Poland)

NASA Astrophysics Data System (ADS)

Kramkowski, Mateusz; Filbrandt-Czaja, Anna; Ott, Florian; Słowiński, Michał; Tjallingii, Rik; Błaszkiewicz, Mirosław; Brauer, Achim

2016-04-01

Lake Jelonek is located in Northern Poland (53°45'58N, 18°23'30E). The lake is surrounded by forest, covers an area of 19,9 ha and has a maximum depth of 13,8 m. In 2013 and 2014 three overlapping and parallel series of long sediment cores JEL14-A-(1445 cm), JEL14-B-(1430 cm), JEL14-C-(1435 cm) and seven short gravity cores JEL13 (K1-K7) have been recovered from the deepest part of the lake. A continuous composite profile JEL14 covering 1426 cm has been established by correlation based on 28 distinct macroscopic marker layers. The sediment sequence can be divided into 15 (I-XV) lithological units. These units comprise biochemical calcite varves, homogeneous calcite-rich gyttja, homogeneous organic-diatomaceous gyttja, and sandy layers. The chronology established so far is based on 14 AMS 14C dates from terrestrial plant remains and tephrochronology (Askja AD-1875) and covers the interval from the Younger Dryas to present times. Based on the chronology and sedimentological characteristics the composite profile has been correlated to a previous core from which a detailed pollen diagram had been established (Filbrandt-Czaja 2009). Here we present initial results from thin section analyses for two intervals from the new composite record JEL14, (I) the uppermost 0-256 cm and (II) the interval from 768-1296 cm. Intercalated between these two varved interval is a thick section (512 cm) of homogeneous organic-ditomaceous sediments. We present varve micro-facies data in combination with μ-XRF element scanning for comprehensive reconstruction of the sedimentation processes in Lake Jelonek. Preliminary varve counting reveals that the uppermost 256 cm varved sediments comprise ca 925 years (2008-1083 AD), while the lower floating varve interval covers the time period from 1850 - 10500 cal a BP. This study is a contribution to the Virtual Institute of Integrated Climate and Landscape Evolution Analysis -ICLEA- of the Helmholtz Association; grant number VH-VI-415. References

Fallout isotope chronology of the near-surface sediment record of Lake Bolătău.

PubMed

Bihari, Árpád; Karlik, Máté; Mîndrescu, Marcel; Szalai, Zoltán; Grădinaru, Ionela; Kern, Zoltán

2018-01-01

Fallout isotope ( 210 Pb ex, 137 Cs and 241 Am) based dating has been carried out on the near-surface sediment core collected from Lake Bolătău-Feredeu (Bukovina, Romania). The motivation was to improve the chronology of this recent section in connection with significant fluctuations observed in sediment accumulation rates, particle size distribution and primordial radioisotope (i.e. 40 K and 232 Th) composition. Previously only an extrapolation of a broad-range OxCal age-depth model, which was based on 8 AMS radiocarbon dates from the deeper part of a parallel sediment sequence and tentatively validated for the upper part using the double peaks of the 137 Cs activity concentration distribution, was available for the studied section (1-24 cm). Parallel to the previous 137 Cs measurement, 210 Pb and 226 Ra (for a more detailed, 210 Pb ex -based chronology), 241 Am (for an additional time-marker), as well as 40 K and 232 Th concentrations have also been determined by gamma-spectrometry. In case of the 210 Pb ex -based chronology, due to a large deviation from a pure exponential distribution, the Constant Flux (CF) model has been used for the calculation of sediment ages and accumulation rates. Although the broad-range OxCal and the CF model were broadly similar down to 22 cm, the 210 Pb ex -based ages are clearly superior in terms of uncertainty in the uppermost 12 cm, while the broad-range model has smaller uncertainty below 20 cm (>150 years). The CF model gave an average mass accumulation rate of (0.08 ± 0.03) g cm -2 yr -1 for sections 0-11 cm, and (0.03 ± 0.01) g cm -2 yr -1 for sections 12-22 cm, respectively. Significant changes have been observed in the depth distribution of both the particle size distribution and the elemental/isotopic composition of the sediment record, most likely related to the variation observable in the intensity and volume of precipitation in the catchment. The obtained high-resolution records of Lake Bolătău, including

Eutrophication History of Small Shallow Lakes in Estonia: Evidence from Multiproxy Analysis of Lake Sediments

NASA Astrophysics Data System (ADS)

Koff, T.; Marzecova, A.; Vandel, E.; Mikomägi, A.; Avi, E.

2015-12-01

Human activities have impacted aquatic systems through the release of contaminants and the regulation of surface and groundwater. Although environmental monitoring has been essential in detecting eutrophication, biodiversity loss or water quality deterioration, monitoring activities are limited in time and are thus not sufficient in their scope to identify causality and thresholds. Paleolimnological studies increasingly show that the response of lakes to climatic and human influences is complex, multidimensional, and often indirectly mediated through watershed processes. In this study we examine the history of eutrophication processes in small lakes in Estonia using the multi-proxy analysis of sediment. Study sites represent lakes with different anthropogenic stressors: urbanisation and recreational use, run-off from an oil shale mine, and fish-kills and liming measures. We have used diverse analytical methods, such as elemental analysis, stable isotopes, fossil pigments, diatoms and Cladocera remains. The information derived from sedimentary indicators broadly agrees with the historical evidence of eutrophication and pollution. Moreover, the sediment records are indispensable for identifying additional issues such as: 1) earlier onset of cultural eutrophication; 2) the significant impact of catchment erosion on the deterioration of lake quality, particularly cyanobacterial blooms; and 3) changes in sedimentation processes with significance for internal biogeochemical cycling of nutrients. Importantly, the integration of several methods has significantly improved interpretation of sedimentary data and elucidated the different strengths of various indicator types. The project findings prove to be highly relevant for both the prediction of the ecological responses of lakes to different anthropogenic impacts and the establishment of reasonable reference target conditions in restoration schemes, as well as for methodological improvements of the sediment analysis.

Incorporation of Fine-Grained Sediment Erodibility Measurements into Sediment Transport Modeling, Capitol Lake, Washington

USGS Publications Warehouse

Stevens, Andrew W.; Gelfenbaum, Guy; Elias, Edwin; Jones, Craig

2008-01-01

Capitol Lake was created in 1951 with the construction of a concrete dam and control gate that prevented salt-water intrusion into the newly formed lake and regulated flow of the Deschutes River into southern Puget Sound. Physical processes associated with the former tidally dominated estuary were altered, and the dam structure itself likely caused an increase in retention of sediment flowing into the lake from the Deschutes River. Several efforts to manage sediment accumulation in the lake, including dredging and the construction of sediment traps upriver, failed to stop the lake from filling with sediment. The Deschutes Estuary Feasibility Study (DEFS) was carried out to evaluate the possibility of removing the dam and restoring estuarine processes as an alternative ongoing lake management. An important component of DEFS was the creation of a hydrodynamic and sediment transport model of the restored Deschutes Estuary. Results from model simulations indicated that estuarine processes would be restored under each of four restoration alternatives, and that over time, the restored estuary would have morphological features similar to the predam estuary. The model also predicted that after dam-removal, a large portion of the sediment eroded from the lake bottom would be deposited near the Port of Olympia and a marina located in lower Budd Inlet seaward of the present dam. The volume of sediment transported downstream was a critical piece of information that managers needed to estimate the total cost of the proposed restoration project. However, the ability of the model to predict the magnitude of sediment transport in general and, in particular, the volume of sediment deposition in the port and marina was limited by a lack of information on the erodibility of fine-grained sediments in Capitol Lake. Cores at several sites throughout Capitol Lake were collected between October 31 and November 1, 2007. The erodibility of sediments in the cores was later determined in the

Synthetic Musk Fragrances in Lake Erie and Lake Ontario Sediment Cores

PubMed Central

Peck, Aaron M.; Linebaugh, Emily K.; Hornbuckle, Keri C.

2009-01-01

Two sediment cores collected from Lake Ontario and Lake Erie were sectioned, dated, and analyzed for five polycyclic musk fragrances and two nitro musk fragrances. The polycyclic musk fragrances were HHCB (Galaxolide), AHTN (Tonalide), ATII (Traseolide), ADBI (Celestolide), and AHMI (Phantolide). The nitro musk fragrances were musk ketone and musk xylene. Chemical analysis was performed by gas chromatography/mass spectrometry (GC/MS) and results from Lake Erie were confirmed using gas chromatography/triple-quadrupole mass spectrometry (GC/MS/MS). The chemical signals observed at the two sampling locations were different from each other due primarily to large differences in the sedimentation rates at the two sampling locations. HHCB was detected in the Lake Erie core while six compounds were detected in the Lake Ontario core. Using measured fragrance and 210Pb activity, the burden of synthetic musk fragrances estimated from these sediment cores is 1900 kg in Lake Erie and 18000 kg in Lake Ontario. The input of these compounds to the lakes is increasing. The HHCB accumulation rates in Lake Erie for 1979-2003 and 1990-2003 correspond to doubling times of 16 ± 4 yr and 8 ± 2 yr, respectively. The results reflect current U.S. production trends for the sum of all fragrance compounds. PMID:17007119

Do peatlands or lakes provide the most comprehensive distal tephra records?

NASA Astrophysics Data System (ADS)

Watson, E. J.; Swindles, G. T.; Lawson, I. T.; Savov, I. P.

2016-05-01

Despite the widespread application of tephra studies for dating and correlation of stratigraphic sequences ('tephrochronology'), questions remain over the reliability and replicability of tephra records from lake sediments and peats, particularly in sites >1000 km from source volcanoes. To address this, we examine the tephrostratigraphy of four pairs of lake and peatland sites in close proximity to one another (<10 km), and evaluate the extent to which the microscopic (crypto-) tephra records in lakes and peatlands differ. The peatlands typically record more cryptotephra layers than nearby lakes, but cryptotephra records from high-latitude peatlands can be incomplete, possibly due to tephra fallout onto snow and subsequent redistribution across the peatland surface by wind and during snowmelt. We find no evidence for chemical alteration of glass shards in peatland or lake environments over the time scale of this study (mid-to late- Holocene). Instead, the low number of basaltic cryptotephra layers identified in distal peatlands reflects the capture of only primary tephra-fall, whereas lakes concentrate tephra falling across their catchments which subsequently washes into the lake, adding to the primary tephra fallout received in the lake. A combination of records from both lakes and peatlands must be used to establish the most comprehensive and complete regional tephrostratigraphies. We also describe two previously unreported late Holocene cryptotephras and demonstrate, for the first time, that Holocene Icelandic ash clouds frequently reached Arctic Sweden.

Chemical and mineralogical proxies of erosion episodes in the dried lake sediments (Amik Lake, Southern Turkey): paleoenvironmental implications

NASA Astrophysics Data System (ADS)

El Ouahabi, Meriam; Hubert-Ferrari, Aurélia; Lebeau, Héléne; Fagel, Nathalie; Vander Auwera, Jacquelinec; Karabacak, Volkan; Schmidt, Sabine

2016-04-01

The Amik Basin in the Eastern Mediterranean region has been continuously occupied since 6000-7000 BC. The landscape has sustained with highly variable anthropic pressure culminating during the Late Roman Period when the Antioch city reached its golden age. The basin also sustained a high seismic activity (M≥7) as it is a releasing step-over along the Dead Sea Fault. The study focuses on the sedimentary record of the Amik Lake occupying the central part of the Basin. Our objective is to constrain major paleo-environmental changes in the area over the last 4000 years and to unravel possible human impacts on the sedimentation. A diverse array of complementary methods was applied on the 6 m long record. High resolution of mineralogical (XRD) and geochemical (XRF) analyses were performed. Quantitative mineralogical phases of sediments by the Rietveld method were computed using Topaz software. The age of the record is constrained combining radionuclide and radiocarbon dating, and checked using the correlation between the earthquake history and rapidly deposited layer identified. A high sedimentation rate of 0.12 cm/yr was inferred at the coring site. The 4000 years old record shows that significant fluctuations of the lake level and the riverine system inflow into the Amik Lake occurred. The Late Bronze lowstand leaded to punctual dryings of the lake at the end of the Bronze/Iron transition marked by the collapse of the Hittite Empire and during the Dark ages. At that time, the riverine was carrying a large terrigenous input linked to strong soil erosion related to deforestation, exploitation of mineral resources and the beginning of upland cultivation. During the Roman Period and in the later periods, upland soils were partly depleted and the riverine system completely transformed by channelization that leaded to a mashification of the Amik Basin. Chemical and mineralogical composition of sediments is quite diversified reflecting the significant geological variation

Plant DNA metabarcoding of lake sediments: How does it represent the contemporary vegetation

PubMed Central

Lammers, Youri; Yoccoz, Nigel Giles; Jørgensen, Tina; Sjögren, Per; Gielly, Ludovic; Edwards, Mary E.

2018-01-01

Metabarcoding of lake sediments have been shown to reveal current and past biodiversity, but little is known about the degree to which taxa growing in the vegetation are represented in environmental DNA (eDNA) records. We analysed composition of lake and catchment vegetation and vascular plant eDNA at 11 lakes in northern Norway. Out of 489 records of taxa growing within 2 m from the lake shore, 17–49% (mean 31%) of the identifiable taxa recorded were detected with eDNA. Of the 217 eDNA records of 47 plant taxa in the 11 lakes, 73% and 12% matched taxa recorded in vegetation surveys within 2 m and up to about 50 m away from the lakeshore, respectively, whereas 16% were not recorded in the vegetation surveys of the same lake. The latter include taxa likely overlooked in the vegetation surveys or growing outside the survey area. The percentages detected were 61, 47, 25, and 15 for dominant, common, scattered, and rare taxa, respectively. Similar numbers for aquatic plants were 88, 88, 33 and 62%, respectively. Detection rate and taxonomic resolution varied among plant families and functional groups with good detection of e.g. Ericaceae, Roseaceae, deciduous trees, ferns, club mosses and aquatics. The representation of terrestrial taxa in eDNA depends on both their distance from the sampling site and their abundance and is sufficient for recording vegetation types. For aquatic vegetation, eDNA may be comparable with, or even superior to, in-lake vegetation surveys and may therefore be used as an tool for biomonitoring. For reconstruction of terrestrial vegetation, technical improvements and more intensive sampling is needed to detect a higher proportion of rare taxa although DNA of some taxa may never reach the lake sediments due to taphonomical constrains. Nevertheless, eDNA performs similar to conventional methods of pollen and macrofossil analyses and may therefore be an important tool for reconstruction of past vegetation. PMID:29664954

Plant DNA metabarcoding of lake sediments: How does it represent the contemporary vegetation.

PubMed

Alsos, Inger Greve; Lammers, Youri; Yoccoz, Nigel Giles; Jørgensen, Tina; Sjögren, Per; Gielly, Ludovic; Edwards, Mary E

2018-01-01

Metabarcoding of lake sediments have been shown to reveal current and past biodiversity, but little is known about the degree to which taxa growing in the vegetation are represented in environmental DNA (eDNA) records. We analysed composition of lake and catchment vegetation and vascular plant eDNA at 11 lakes in northern Norway. Out of 489 records of taxa growing within 2 m from the lake shore, 17-49% (mean 31%) of the identifiable taxa recorded were detected with eDNA. Of the 217 eDNA records of 47 plant taxa in the 11 lakes, 73% and 12% matched taxa recorded in vegetation surveys within 2 m and up to about 50 m away from the lakeshore, respectively, whereas 16% were not recorded in the vegetation surveys of the same lake. The latter include taxa likely overlooked in the vegetation surveys or growing outside the survey area. The percentages detected were 61, 47, 25, and 15 for dominant, common, scattered, and rare taxa, respectively. Similar numbers for aquatic plants were 88, 88, 33 and 62%, respectively. Detection rate and taxonomic resolution varied among plant families and functional groups with good detection of e.g. Ericaceae, Roseaceae, deciduous trees, ferns, club mosses and aquatics. The representation of terrestrial taxa in eDNA depends on both their distance from the sampling site and their abundance and is sufficient for recording vegetation types. For aquatic vegetation, eDNA may be comparable with, or even superior to, in-lake vegetation surveys and may therefore be used as an tool for biomonitoring. For reconstruction of terrestrial vegetation, technical improvements and more intensive sampling is needed to detect a higher proportion of rare taxa although DNA of some taxa may never reach the lake sediments due to taphonomical constrains. Nevertheless, eDNA performs similar to conventional methods of pollen and macrofossil analyses and may therefore be an important tool for reconstruction of past vegetation.

Explosive eruption records from Eastern Africa: filling in the gaps with tephra records from stratified lake sequences

NASA Astrophysics Data System (ADS)

Lane, Christine; Asrat, Asfawossen; Cohen, Andy; Cullen, Victoria; Johnson, Thomas; Lamb, Henry; Martin-Jones, Catherine; Poppe, Sam; Schaebitz, Frank; Scholz, Christopher

2017-04-01

On-going research into the preservation of volcanic ash fall in stratified Holocene lake sediments in Eastern Africa reveals the level of incompleteness of our explosive eruption record. Only nine eruptions with VEI >4 are recorded in the LaMEVE database (Crosweller et al., 2012) and of the 188 Holocene eruptions listed for East African volcanoes in the Global Volcanism Programme database, only 24 are dated to > 2000 years ago (GVP, 2013). Tephrostratigraphic investigation of Holocene sediments from a number of lakes, including Lake Kivu (south of the Virunga volcanic field), Lake Victoria (west of the Kenyan Rift volcanism) and palaeolake Chew Bahir (southern Ethiopia), all reveal multiple tephra layers, which indicate vastly underestimated eruption histories. Whereas the tephra layers in Lake Kivu were all located macroscopically, no visible tephra layers were observed in the sediments from Lake Victoria and Chew Bahir. Instead, tephra are preserved as non-visible horizons (cryptotephra), revealed only after laboratory processing. These results indicate that even where we do have stratified visible tephra records, the number of past eruptions may still be a minimum. Cryptotephra studies therefore play a fundamental role in building comprehensive records of past volcanism. Challenges remain, in this understudied region, to identify the volcanic source of each of the tephra layers, which requires geochemical correlation to proximal volcanic deposits. Where correlations to source can be achieved, explosive eruption frequencies and recurrence rates may be assessed for individual volcanoes. Furthermore, if a tephra layer can be traced into multiple sedimentary sequences, the potential exists to evaluate eruption magnitude, providing a more useful criterion for risk assessment. Filling in the gaps in our understanding of East African Rift volcanism and the associated hazards is therefore critically dependent upon bringing together this important data from distal

A 400-ka tephrochronological framework for Central America from Lake Petén Itzá (Guatemala) sediments

NASA Astrophysics Data System (ADS)

Kutterolf, S.; Schindlbeck, J. C.; Anselmetti, F. S.; Ariztegui, D.; Brenner, M.; Curtis, J.; Schmid, D.; Hodell, D. A.; Mueller, A.; Pérez, L.; Pérez, W.; Schwalb, A.; Frische, M.; Wang, K.-L.

2016-10-01

Lake Petén Itzá, northern Guatemala, lies within a hydrologically closed basin in the south-central area of the Yucatán Peninsula, and was drilled under the auspices of the International Continental Scientific Drilling Program (ICDP) in 2006. At 16°55‧N latitude, the lake is ideally located for study of past climate and environmental conditions in the Neotropical lowlands. Because of its great depth (>160 m), Lake Petén Itzá has a record of continuous sediment accumulation that extends well into the late Pleistocene. A key obstacle to obtaining long climate records from the region is the difficulty of establishing a robust chronology beyond ∼40 ka, the limit of 14C dating. Tephra layers within the Lake Petén Itzá sediments, however, enable development of age/depth relations beyond 40 ka. Ash beds from large-magnitude, Pleistocene-to-Holocene silicic eruptions of caldera volcanoes along the Central American Volcanic Arc (CAVA) were found throughout drill cores collected from Lake Petén Itzá. These ash beds were used to establish a robust chronology extending back 400 ka. We used major- and trace-element glass composition to establish 12 well-constrained correlations between the lacustrine tephra layers in Lake Petén Itzá sediments and dated deposits at the CAVA source volcanoes, and with their marine equivalents in eastern Pacific Ocean sediments. The data also enabled revision of eight previous determinations of erupted volumes and masses, and initial estimates for another four eruptions, as well as the designation of source areas for 14 previously unknown eruptions. The new and revised sedimentation rates for the older sediment successions identify the interglacial of MIS5a between 84 and 72 ka, followed by a stadial between 72 and 59 ka that corresponds to MIS4. We modified the age models for the Lake Petén Itzá sediment sequences, extended the paleoclimate and paleoecological record for this Neotropical region to ∼400 ka, and determined the

A Model-Based Approach to Infer Shifts in Regional Fire Regimes Over Time Using Sediment Charcoal Records

NASA Astrophysics Data System (ADS)

Itter, M.; Finley, A. O.; Hooten, M.; Higuera, P. E.; Marlon, J. R.; McLachlan, J. S.; Kelly, R.

2016-12-01

Sediment charcoal records are used in paleoecological analyses to identify individual local fire events and to estimate fire frequency and regional biomass burned at centennial to millenial time scales. Methods to identify local fire events based on sediment charcoal records have been well developed over the past 30 years, however, an integrated statistical framework for fire identification is still lacking. We build upon existing paleoecological methods to develop a hierarchical Bayesian point process model for local fire identification and estimation of fire return intervals. The model is unique in that it combines sediment charcoal records from multiple lakes across a region in a spatially-explicit fashion leading to estimation of a joint, regional fire return interval in addition to lake-specific local fire frequencies. Further, the model estimates a joint regional charcoal deposition rate free from the effects of local fires that can be used as a measure of regional biomass burned over time. Finally, the hierarchical Bayesian approach allows for tractable error propagation such that estimates of fire return intervals reflect the full range of uncertainty in sediment charcoal records. Specific sources of uncertainty addressed include sediment age models, the separation of local versus regional charcoal sources, and generation of a composite charcoal record The model is applied to sediment charcoal records from a dense network of lakes in the Yukon Flats region of Alaska. The multivariate joint modeling approach results in improved estimates of regional charcoal deposition with reduced uncertainty in the identification of individual fire events and local fire return intervals compared to individual lake approaches. Modeled individual-lake fire return intervals range from 100 to 500 years with a regional interval of roughly 200 years. Regional charcoal deposition to the network of lakes is correlated up to 50 kilometers. Finally, the joint regional charcoal

Sediment deposition and sources into a Mississippi River floodplain lake; Catahoula Lake, Louisiana

USGS Publications Warehouse

Latuso, Karen D.; Keim, Richard F.; King, Sammy L.; Weindorf, David C.; DeLaune, Ronald D.

2017-01-01

Floodplain lakes are important wetlands on many lowland floodplains of the world but depressional floodplain lakes are rare in the Mississippi River Alluvial Valley. One of the largest is Catahoula Lake, which has existed with seasonally fluctuating water levels for several thousand years but is now in an increasingly hydrologically altered floodplain. Woody vegetation has been encroaching into the lake bed and the rate of this expansion has increased since major human hydrologic modifications, such as channelization, levee construction, and dredging for improvement of navigation, but it remains unknown what role those modifications may have played in altering lake sedimentation processes. Profiles of thirteen 137Cs sediment cores indicate sedimentation has been about 0.26 cm y− 1 over the past 60 years and has been near this rate since land use changes began about 200 years ago (210Pb, and 14C in Tedford, 2009). Carbon sequestration was low (10.4 g m− 2 y− 1), likely because annual drying promotes mineralization and export. Elemental composition (high Zr and Ti and low Ca and K) and low pH of recent (<~60 y) or surface sediments suggest Gulf Coastal Plain origin, but below the recent sediment deposits, 51% of sediment profiles showed influence of Mississippi River alluvium, rich in base cations such as K+, Ca2 +, and Mg2 +. The recent shift to dominance of Coastal Plain sediments on the lake-bed surface suggests hydrologic modification has disconnected the lake from sediment-bearing flows from the Mississippi River. Compared to its condition prior to hydrologic alterations that intensified in the 1930s, Catahoula Lake is about 15 cm shallower and surficial sediments are more acidic. Although these results are not sufficient to attribute ecological changes directly to sedimentological changes, it is likely the altered sedimentary and hydrologic environment is contributing to the increased dominance of woody vegetation.

Storm-induced redistribution of deepwater sediments in Lake Ontario

USGS Publications Warehouse

Halfman, J.D.; Dittman, D.E.; Owens, R.W.; Etherington, M.D.

2006-01-01

High-resolution seismic reflection profiles, side-scan sonar profiles, and surface sediment analyses for grain size (% sand, silt & clay), total organic carbon content, and carbonate content along shore-perpendicular transects offshore of Olcott and Rochester in Lake Ontario were utilized to investigate cm-thick sands or absence of deep-water postglacial sediments in water depths of 130 to 165 m. These deepwater sands were observed as each transect approached and occupied the "sills," identified by earlier researchers, between the three deepest basins of the lake. The results reveal thin (0 to 5-cm) postglacial sediments, lake floor lineations, and sand-rich, organic, and carbonate poor sediments at the deepwater sites (> 130 m) along both transects at depths significantly below wave base, epilimnetic currents, and internal wave activity. These sediments are anomalous compared to shallower sediments observed in this study and deeper sediments reported by earlier research, and are interpreted to indicate winnowing and resuspension of the postglacial muds. We hypothesize that the mid-lake confluence of the two-gyre surface current system set up by strong storm events extends down to the lake floor when the lake is isothermal, and resuspends and winnows lake floor sediment at these locations. Furthermore, we believe that sedimentation is more likely to be influenced by bottom currents at these at these sites than in the deeper basins because these sites are located on bathymetric highs between deeper depositional basins of the lake, and the bathymetric constriction may intensify any bottom current activity at these sites.

Monitoring climate signal transfer into the varved lake sediments of Lake Czechowskie, Poland

NASA Astrophysics Data System (ADS)

Groß-Schmölders, Miriam; Ott, Florian; Brykała, Dariusz; Gierszewski, Piotr; Kaszubski, Michał; Kienel, Ulrike; Brauer, Achim

2015-04-01

In 2012 we started a monitoring program at Lake Czechowskie, Poland, because the lake comprises a long Holocene time series of calcite varves until recent times. The aim of the program is to understand how environmental and climatic conditions influence the hydrological conditions and, ultimately, the sediment deposition processes of the lake. Lake Czechowskie is located in the north of Poland in the Pomeranian Lake District and is part of the national park Tuchola Forest. The landscape and the lake is formed by the glacier retreat after the last glaciation (Weichselian). Lake Czechowskie is a typical hardwater lake and has a length of 1.4 km, an average width of 600 m and a lake surface area of ca 4 km. The maximum depth of 32 m is reached in a rather small hollow in the eastern part of the lake. Two different types of sediment traps provide sediment samples with monthly resolution from different water depths (12m, 26m). In addition, hydrological data including water temperature in different depths, water inflow, throughflow and outflow and the depth of visibility are measured. These data allow to describe strength and duration of lake mixing in spring and autumn and its influence on sedimentation. The sediment samples were analyzed with respect to their dry weight (used to calculate mean daily sediment flux), their inorganic and organic carbon contents, the stable C- and O-isotopes of organic matter and calcite as well as N-isotopes of organic matter. For selected samples dominant diatom taxa are determined. Our first results demonstrate the strong influence of the long winter with ice cover until April in 2013 on the sedimentation. A rapid warming in only 9 days starting on April 9th from -0,3 C° to 15,2 C° resulted in fast ice break-up and a short but intensive lake mixing. In consequence of this short mixing period a strong algal bloom especially of Fragilaria and Crysophycea commenced in April and had its maximum in May. This bloom further induced biogenic

Trends in chemical concentration in sediment cores from three lakes in New Jersey and one lake on Long Island, New York

USGS Publications Warehouse

Long, Gary R.; Ayers, Mark A.; Callender, Edward; Van Metre, Peter C.

2003-01-01

Data from this study indicate that changes in population, land use, and chemical use in the urbanized watersheds over the period of sedimentary record have contributed to upward trends in concentrations of trace elements and hydrophobic organic compounds. Although downward trends were observed for some constituents in the years after their concentrations peaked, concentrations of most constituents in urban lake cores were higher in the most recently deposited sediments than at the base of each respective core and in the reference lake cores. Similar trends in concentrations of these constituents have been observed in sediment cores from other urban lakes across the United States.

Ground Penetrating Radar, Magnetic and Compositional Analysis of Sediment Cores and Surface Samples: The Relationships Between Lacustrine Sediments and Holocene Lake- Level and Climate Change at Deming Lake, Minnesota, USA

NASA Astrophysics Data System (ADS)

Murray, R.; Lascu, I.; Plank, C.

2007-12-01

Deming Lake is a small (<1 square km), deep (about 17m), meromictic kettle lake situated near the prairie- forest boundary, in Itasca State Park, MN. Because of the lake's location and morphology, the accumulated sediments comprise a high-resolution record of limnological and ecological changes in response to Holocene climate variations. We used a shore perpendicular transect of three cores (located in littoral, mid-slope, and profundal settings) and ground penetrating radar (GPR) profiles to investigate Holocene lake-level variability at Deming. Cores were sampled continuously at a 1-2 cm resolution and sediment composition (in terms of percent organic matter, carbonate material, and minerogenic residue) was determined via loss on ignition (LOI). Isothermal remanent magnetization (IRM) and anhysteretic remanent magnetization (ARM) were used as proxies of magnetic mineral concentration and grain size. Four lithostratigraphic units were identified and correlated between cores based on these analyses. Changes in GPR facies corroborate the correlation between the two shallow cores. In order to inform our interpretation of down-core variations in magnetic properties and LOI values in terms of variations in lake depth, a suite of over 70 modern sediment samples were collected from the basin and analyzed. LOI compositional variability across the basin was high, with no clear trends related to depth or distance from shore. A sharp decrease in minerogenic content was observed at depths consistent with a predicted wave-base of 0.5 m, but aside from this trend it appears the steep slopes of much of the basin promote gravity driven slumping and mixing of sediments at depth. In the profundal sediments IRM values are routinely 5% higher than in the slope and littoral environments, while ARM/IRM ratios indicate an increase in magnetic grain size with water depth. We infer that an increase in coarse organic material in the shallow-water cores of Deming records a period of aridity

Climate and lake-level history of the northern altiplano, Bolivia, as recorded in holocene sediments of the Rio Desaguadero

USGS Publications Warehouse

Baucom, P.C.; Rigsby, C.A.

1999-01-01

Strata exposed in terraces and modern cutbanks along the Rio Desaguadero contain a variety of lithofacies that were deposited in four distinct facie??s associations. These facie??s associations document a history of aggradation and downcutting that is linked to Holocene climate change on the Altiplano. Braided-stream, meandering-stream, deltaic and shoreline, and lacustrine sediments preserved in multi-level terraces in the northern Rio Desaguadero valley record two high-water intervals: one between 4500 and 3900 yr BP and another between 2000 and 2200 yr BP. These wet periods were interrupted by three periods of fluvial downcutting, centered at approximately 4000 yr BP, 3600 yr BP, and after 2000 yr BP. Braided-river sediments preserved in a single terrace level in the southern Rio Desaguadero valley record a history of nearly continuous fluvial sedimentation from at least 7000 yr BP until approximately 3200 yr BP that was followed by a single episode (post-3210 yr BP) of downcutting and lateral migration. The deposition and subsequent fluvial downcutting of the northern strata was controlled by changes in effective moisture that can be correlated to Holocene water-level fluctuations of Lake Titicaca. The deposition and dissection of braided-stream sediments to the south are more likely controlled by a combination of base-level change and sediment input from the Rio Mauri. Copyright ??1999, SEPM (Society for Sedimentar)- Geology).

Late quaternary sediments, minerals, and inferred geochemical history of Didwana Lake, Thar Desert, India

USGS Publications Warehouse

Wasson, R.J.; Smith, G.I.; Agrawal, D.P.

1984-01-01

Variations in clastic sediment texture, mineralogy of both evaporites formed at the surface and precipitates formed below the lake floor, and the relative chemical activities of the major dissolved components of the chemical precipitates, have allowed reconstruction of the history of salinity and water-level changes in Didwana Lake, Thar Desert, India. Hypersaline conditions prevailed at about the Last Glacial Maximum, with little evidence of clastic sediments entering the lake. Between ca. 13,000 and 6000 B.P. the lake level fluctuated widely, the lake alternately hypersaline and fresh, and clastic sediments were delivered to the lake at a low rate. Deep-water conditions occurred ca. 6000 B.P. and clastic influx increased abruptly. The water level dropped towards 4000 B.P. when the lake dried briefly. Since 4000 B.P. the lake has been ephemeral with a lowered rate of sedimentation and mildly saline conditions rather like those of today. This sequence of changes documented in the lake parallels changes in vegetation recorded in published pollen diagrams from both the Thar and the Arabian Sea. Correlation of the various lines of evidence suggests that the climate of the Last Glacial Maximum at Didwana was dry and windy with a weak monsson circulation. The monsson was re-established between ca. 13,000 and a little before 6000 B.P., and, when winter rainfall increased ca. 6000 B.P., the lake filled to its maximum depth. ?? 1984.

The Geochemical Record of Cultural Eutrophication and Remediation Efforts in Three Connecticut Lakes

NASA Astrophysics Data System (ADS)

Ku, T.; Bourne, H. L.; Tirtajana, S.; Nahar, M.; Kading, T.

2009-12-01

Cultural eutrophication is the process whereby human activity increases the amount of nutrients, primarily nitrogen and phosphorous, entering an aquatic ecosystem causing excessive biological growth. To reverse or decelerate cultural eutrophication, many regulatory agencies have implemented stringent laws intended to lower the flux of nutrients into impacted water bodies or have emplaced internal remediation systems designed to decrease primary productivity. To quantify the effects of cultural eutrophication and remediation efforts, we examined sedimentary histories of three eutrophic Connecticut lakes that record the transition from pre-anthropogenic conditions into eutrophication and through recent remediation. The three Connecticut lakes (Lake Waramaug, Beseck Lake, and Amos Lake) represent a range of remediation activities. Since 1983, Lake Waramaug has been the focus of significant remediation efforts including the installation of three hypolimnetic withdrawal / layer aeration systems, zoning regulations to limit runoff, and the stocking and seeding of fish and zooplankton. Beseck Lake has experienced episodic eutrophic conditions, in part due to failing septic systems, and in 2001, 433 residences were converted from septic systems to a city sewer system. Amos Lake serves as a cultural eutrophication end member as it has not has received any major remediation. Multiple freeze and gravity cores were collected from 2005-2008. Radiocarbon, Pb-210, Cs-137, Hg, and Pb measurements determined sediment ages. Organic C accumulation rates, C/N ratios, organic matter delta-15N, bulk sediment Fe and Al concentrations, and P speciation (labile, iron-bound, aluminum-bound, organic, and total) determined sediment and nutrient sources and accumulations. Dithionite-extractable iron, pyrite S, and pyrite delta-34S provided insight into changes in P-Fe-S cycling. The sediment cores represent the last few hundreds of years of lake history and, importantly, some Lake Waramaug

Generating quantitative palaeoflood data from homogeneous lake sediments: a case-study from Brotherswater, northwest England

NASA Astrophysics Data System (ADS)

Schillereff, Daniel; Chiverrell, Richard; Macdonald, Neil; Hooke, Janet

2016-04-01

The scarcity of long-term hydrological data is a barrier to reliably determining the likelihood of floods becoming more frequent and/or intense in a warmer world. Lakes and their sediments are increasingly being used to reconstruct long-term, highly-resolved datasets of past floods but the ultimate goal, generating quantitative palaeohydrological data to augment flood frequency analyses, is a persistent challenge. To this end, ascertaining the autogenic and allogenic processes influencing the character and preservation potential of palaeoflood laminations and determining the minimum discharge at which a sedimentary imprint will be deposited in a particular system are two key precursors. Some success has been achieved at lakes containing annually-laminated sequences or where event layers exhibit well-defined lithological contacts. Many non-alpine and non-polar lakes, especially those in temperate regions, are instead characterised by visually-homogeneous, organic-rich sediments from which discrete flood laminations are difficult to discriminate. Working at Brotherswater, a small upland lake in northwest England, we have successfully demonstrated an approach to obtain flood frequency and magnitude data from this type of lake system by integrating a 16 month sediment trap deployment (CE 2013-2014) with the recent (CE 1962 - 2014) depositional record. The geochemical composition and end-member modelling of the trap data shed light on the seasonal variation in background sedimentation dynamics, specifically enhanced sediment supply during winter, spring diatom blooms and heightened summer productivity, which alter the signature of coarse-grained deposition in response to higher flows. Having pinpointed the characteristic flood end-member, comparison of the short-core palaeoflood reconstruction to local river discharge data was able to reveal the hydrological thresholds of this system: flood magnitudes calculated to have a four year recurrence interval are preserved in

A High-Resolution Biogenic Silica Record From Lake Titicaca, Peru-Bolivia: South American Millennial-Scale Climate Variability From 18-60 Kya

NASA Astrophysics Data System (ADS)

Ekdahl, E. J.; Fritz, S. C.; Stevens, L. R.; Baker, P. A.; Seltzer, G. O.

2004-12-01

Sediments recovered from a deep basin in Lake Titicaca, Peru-Boliva, were analyzed for biogenic silica (BSi) content by extraction of freeze dried sediments in 1% sodium carbonate. Sediments were dated using an age model developed from multiple 14C dates on bulk sediments. The BSi record shows distinct fluctuations in concentration and accumulation rate from 18 to 60 kya. Multi-taper method spectral analysis reveals a significant millennial-scale component to these fluctuations centered at 1370 years. High BSi accumulation rates correlate with enhanced benthic diatom preservation, suggesting that the BSi record is related to variations in lake water level. Modern-day Lake Titicaca lake level and precipitation are strongly related to northern equatorial Atlantic sea surface temperatures, with cooler SSTs related to wetter conditions. Subsequently, the spectral behavior of the GRIP ice core δ 18O record was investigated in order to estimate coherency and linkages between North Atlantic and tropical South American climate. GRIP data exhibit a significant 1370-year spectral peak which comprises approximately 26% of the total variability in the record. Despite a high degree of coherency between millennial-scale periodicities in Lake Titicaca BSi and GRIP δ 18O records, the Lake Titicaca silica record does not show longer term cooling cycles characteristic of D-O cycles found in the GRIP record. Rather, the Lake Titicaca record is highly periodic and more similar in nature to several Antarctic climate proxy records. These results suggest that while South American tropical climate varies in phase with North Atlantic climate, additional forcing mechanisms are manifest in the region which may include tropical Pacific and Southern Ocean variability.

Sedimentology, tephrostratigraphy, and chronology of the DEEP site sediment record, Lake Ohrid (Albania, FYROM)

NASA Astrophysics Data System (ADS)

Leicher, Niklas; Wagner, Bernd; Francke, Alexander; Just, Janna; Zanchetta, Giovanni; Sulpizio, Roberto; Giaccio, Biagio; Nomade, Sebastien

2017-04-01

Lake Ohrid, located on the Balkan Peninsula, is one of the very few lakes in the world that provides a continuous and high-resolution record of environmental change of >1.3 Ma. The sedimentary archive was drilled in spring 2013 within the scope of the International Continental Scientific Drilling Program (ICDP) and the Scientific Collaboration on Past Speciation Conditions in Lake Ohrid (SCOPSCO) project in order to investigate local and regional geological and paleoclimatic processes, as well as triggers of evolutionary patterns and endemic biodiversity. The continuous composite profile (584 m) of the main drill site DEEP was logged (XRF, MSCL) and subsampled for biogeochemical (TIC, TOC, TN, TS) and sedimentological (grain size) analyses. The lithology of the DEEP site indicates that the history of Lake Ohrid can roughly be separated into two parts, with the older section between 584 and 450 m depth being characterised by a sedimentary facies indicating shallow water conditions, which is likely younger than ca. 1.9 Ma. In the lowermost few meters of the succession gravels and pebbles hampered a deeper drilling penetration and indicate that fluvial conditions existed during the onset of lake formation. Together with geotectonic, seismic, and biological information, the data imply that the Ohrid basin formed by transtension during the Miocene, opened during the Pliocene and Pleistocene, and that the lake established between 1.9 and 1.3 Ma ago. The sediments of the younger part (< 450 m sediment depth) indicate that deeper water conditions established in Lake Ohrid after 1.3 Ma ago. Since then, biogeochemical proxy data respond to global glacial/interglacial variability, with warm periods being characterized by high TIC and TOC concentrations and cold periods by negligible TIC and low TOC contents, respectively. To date, 56 tephra horizons have been identified in the upper 450 m of the DEEP site sequence and are subject of ongoing investigations aimed at identifying

Particle-associated contaminants in street dust, parking lot dust, soil, lake-bottom sediment, and suspended and streambed sediment, Lake Como and Fosdic Lake watersheds, Fort Worth, Texas, 2004

USGS Publications Warehouse

Wilson, Jennifer T.; Van Metre, Peter C.; Werth, Charles J.; Yang, Yanning

2006-01-01

A previous study by the U.S. Geological Survey of impaired water bodies in Fort Worth, Texas, reported elevated but variable concentrations of particle-associated contaminants (PACs) comprising chlorinated hydrocarbons, polycyclic aromatic hydrocarbons, and trace elements in suspended and bed sediment of lakes and streams affected by urban land use. The U.S. Geological Survey, in cooperation with the City of Fort Worth, collected additional samples during October 2004 to investigate sources of PACs in the watersheds of two impaired lakes: Lake Como and Fosdic Lake. Source materials and aquatic sediment were sampled and analyzed for PACs. Source materials sampled consisted of street dust and soil from areas with residential and commercial land use and parking lot dust from sealed and unsealed parking lots. Aquatic sediment sampled consisted of bottom-sediment cores from the two lakes and suspended and streambed sediment from the influent stream of each lake. Samples were analyzed for chlorinated hydrocarbons (organochlorine pesticides and polychlorinated biphenyls), polycyclic aromatic hydrocarbons, major and trace elements, organic carbon, grain size, and radionuclides.

Impact of methane flow through deformable lake sediments on atmospheric release

NASA Astrophysics Data System (ADS)

Scandella, B.; Juanes, R.

2010-12-01

Methane is a potent greenhouse gas that is generated geothermally and biologically in lake and ocean sediments. Free gas bubbles may escape oxidative traps and contribute more to the atmospheric source than dissolved methane, but the details of the methane release depend on the interactions between the multiple fluid phases and the deformable porous medium. We present a model and supporting laboratory experiments of methane release through “breathing” dynamic flow conduits that open in response to drops in the hydrostatic load on lake sediments, which has been validated against a high-resolution record of free gas flux and hydrostatic pressure in Upper Mystic Lake, MA. In contrast to previous linear elastic fracture mechanics analysis of gassy sediments, the evolution of gas transport in a deformable compliant sediment is presented within the framework of multiphase poroplasticity. Experiments address how strongly the mode and rate of gas flow, captured by our model, impacts the size of bubbles released into the water column. A bubble's size in turn determines how efficiently it transports methane to the atmosphere, and integrating this effect will be critical to improving estimates of the atmospheric methane source from lakes. Cross-sectional schematic of lake sediments showing two venting sites: one open at left and one closed at right. The vertical release of gas bubbles (red) at the open venting site creates a local pressure drop, which drives both bubble formation from the methane-rich pore water (higher concentrations shaded darker red) and lateral advection of dissolved methane (purple arrows). Even as bubbles in the open site escape, those at the closed site remain trapped.

Promise and Pitfalls of Using Grain Size Analysis to Identify Glacial Sediments in Alpine Lake Cores.

NASA Astrophysics Data System (ADS)

Clark, D. H.

2011-12-01

Lakes fed by glacier outwash should have a clastic particle-size record distinct from non-glacial lakes in the same area, but do they? The unique turquoise color of alpine glacial lakes reflects the flux of suspended clastic glacial rock flour to those lakes; conversely, lakes not fed by outwash are generally clear with sediments dominated by organics or slope-wash from nearby hillslopes. This contrast in sediment types and sources should produce a distinct and measureable different in grain sizes between the two settings. Results from a variety of lakes suggest the actual situation is often more subtle and complex. I compare grain size results to other proxies to assess the value of grain size analysis for paleoglacier studies. Over the past 10 years, my colleagues and I have collected and analyzed sediment cores from a wide variety of lakes below small alpine glaciers in an attempt to constrain the timing and magnitude of alpine glaciation in those basins. The basic concept is that these lakes act as continuous catchments for any rock flour produced upstream by glacier abrasion; as a glacier grows, the flux of rock flour to the lake will also increase. If the glacier disappears entirely, rock flour deposition will also cease in short order. We have focused our research in basins with simple sedimentologic settings: mostly small, high-altitude, stripped granitic or metamorphic cirques in which the cirque glaciers are the primary source of clastic sediments. In most cases, the lakes are fed by meltwater from a modern glacier, but were ice free during the earlier Holocene. In such cases, the lake cores should record formation of and changes in activity of the glacier upstream. We used a Malvern Mastersizer 2000 laser particle size analyzer for our grain size analyses, as well as recording magnetic susceptibility, color, and organics for the same cores. The results indicate that although lakes often experience increases in silt and clay-size (<0.63 mm) clastic

Comparison among the microbial communities in the lake, lake wetland, and estuary sediments of a plain river network.

PubMed

Huang, Wei; Chen, Xing; Wang, Kun; Chen, Junyi; Zheng, Binghui; Jiang, Xia

2018-06-10

Sediment microbial communities from plain river networks exert different effects on pollutant transformation and migration in lake basins. In this study, we examined millions of Illumina reads (16S rRNA gene amplicons) to compare lake, lake wetland, and estuary bacterial communities through a technically consistent approach. Results showed that bacterial communities in the sampled lake sediments had the highest alpha-diversity (Group B), than in sampled lake wetland sediments and estuary sediments. Proteobacteria was the most abundant (more than 30%) phyla in all the sediments. The lake sediments had more Nitrospirae (1.63%-11.75%) and Acidobacteria (3.46%-10.21%) than the lake wetland and estuary sediments, and estuary sediments had a greater abundance of the phylum Firmicutes (mean of 22.30%). Statistical analysis (LEfSe) revealed that lake wetland sediments contained greater abundances of the class Anaerolineaceae, orders Xanthomonadales, Pseudomonadales, and genera Flavobacterium, Acinetobacter. The lake sediments had a distinct community of diverse primary producers, such as phylum Acidobacteria, order Ignavibacteriales, and families Nitrospiraceae, Hydrogenophilaceae. Total phosphorus and organic matter were the main factors influencing the bacterial communities in sediments from several parts of the lake wetland and river estuary (p < .05). The novel insights into basin pollution control in plain river networks may be obtained from microbial distribution in sediments from different basin regions. © 2018 The Authors. MicrobiologyOpen published by John Wiley & Sons Ltd.

Sedimentary record of the 1872 earthquake and "Tsunami" at Owens Lake, southeast California

USGS Publications Warehouse

Smoot, J.P.; Litwin, R.J.; Bischoff, J.L.; Lund, S.J.

2000-01-01

In 1872, a magnitude 7.5-7.7 earthquake vertically offset the Owens Valley fault by more than a meter. An eyewitness reported a large wave on the surface of Owens Lake, presumably initiated by the earthquake. Physical evidence of this event is found in cores and trenches from Owens Lake, including soft-sediment deformation and fault offsets. A graded pebbly sand truncates these features, possibly over most of the lake floor, reflecting the "tsunami" wave. Confirmation of the timing of the event is provided by abnormally high lead concentrations in the sediment immediately above and below these proposed earthquake deposits derived from lead-smelting plants that operated near the eastern lake margin from 1869-1876. The bottom velocity in the deepest part of the lake needed to transport the coarsest grain sizes in the graded pebbly sand provides an estimate of the minimum initial 'tsunami' wave height at 37 cm. This is less than the wave height calculated from long-wave numerical models (about 55 cm) using average fault displacement during the earthquake. Two other graded sand deposits associated with soft-sediment deformation in the Owens Lake record are less than 3000 years old, and are interpreted as evidence of older earthquake and tsunami events. Offsets of the Owens Valley fault elsewhere in the valley indicate that at least two additional large earthquakes occurred during the Holocene, which is consistent with our observations in this lacustrine record.

A late quaternary record of eolian silt deposition in a maar lake, St. Michael Island, western Alaska

USGS Publications Warehouse

Muhs, D.R.; Ager, T.A.; Been, J.; Bradbury, J.P.; Dean, W.E.

2003-01-01

Recent stratigraphic studies in central Alaska have yielded the unexpected finding that there is little evidence for full-glacial (late Wisconsin) loess deposition. Because the loess record of western Alaska is poorly exposed and not well known, we analyzed a core from Zagoskin Lake, a maar lake on St. Michael Island, to determine if a full-glacial eolian record could be found in that region. Particle size and geochemical data indicate that the mineral fraction of the lake sediments is not derived from the local basalt and is probably eolian. Silt deposition took place from at least the latter part of the mid-Wisconsin interstadial period through the Holocene, based on radiocarbon dating. Based on the locations of likely loess sources, eolian silt in western Alaska was probably deflated by northeasterly winds from glaciofluvial sediments. If last-glacial winds that deposited loess were indeed from the northeast, this reconstruction is in conflict with a model-derived reconstruction of paleowinds in Alaska. Mass accumulation rates in Zagoskin Lake were higher during the Pleistocene than during the Holocene. In addition, more eolian sediment is recorded in the lake sediments than as loess on the adjacent landscape. The thinner loess record on land may be due to the sparse, herb tundra vegetation that dominated the landscape in full-glacial time. Herb tundra would have been an inefficient loess trap compared to forest or even shrub tundra due to its low roughness height. The lack of abundant, full-glacial, eolian silt deposition in the loess stratigraphic record of central Alaska may be due, therefore, to a mimimal ability of the landscape to trap loess, rather than a lack of available eolian sediment. ?? 2003 University of Washington. Published by Elsevier Inc. All rights reserved.

Historical sediment mercury deposition trends for South Dakota lakes

USGS Publications Warehouse

Squillace, Maria K.; Sieverding, Heidi L.; Betemariam, Hailemelekot H.; Urban, Noel R.; Penn, Michael R.; DeSutter, Thomas M.; Chipps, Steven R.; Stone, James J.

2018-01-01

PurposeSelect South Dakota, USA water bodies, including both natural lakes and man-made impoundments, were sampled and analyzed to assess mercury (Hg) dynamics and historical patterns of total Hg deposition.Materials and methodsSediment cores were collected from seven South Dakota lakes. Mercury concentrations and flux profiles were determined using lead (210Pb) dating and sedimentation rates.Results and discussionMost upper lake sediments contained variable heavy metal concentrations, but became more consistent with depth and age. Five of the seven lakes exhibited Hg accumulation fluxes that peaked between 1920 and 1960, while the remaining two lakes exhibited recent (1995–2009) Hg flux spikes. Historical sediment accumulation rates and Hg flux profiles demonstrate similar peak and stabilized values. Mercury in the sampled South Dakota lakes appears to emanate from watershed transport due to erosion from agricultural land use common to the Northern Great Plains.ConclusionsFor sampled South Dakota lakes, watershed inputs are more significant sources of Hg than atmospheric deposition.

Geochemical and Sedimentological Records of Late Quaternary Climate Change, Lake Tanganyika, Tropical East Africa

NASA Astrophysics Data System (ADS)

Felton, A. A.; Russell, J. M.; Cohen, A. S.; Baker, M. E.; McGlue, M. M.; Lezzar, K. E.

2005-12-01

We have analyzed piston core records from Lake Tanganyika (western Tanzania, East African Rift Valley) to investigate possible signals of tropical paleoclimate change during the Late Quaternary. Long paleoclimate records from East Africa are of importance for understanding climatic processes such as the role of solar variability in regulating tropical climates at Milankovitch time scales, and the relationship between abrupt climate changes, migration of Intertropical Convergence Zone, and regional climate variability (Nicholson, 2000). However, records of pre-Holocene climate variability from tropical African lakes (>25ka) are still quite rare. Long records from Lake Tanganyika are of particular interest given the lake's antiquity and its demonstrated potential for producing high resolution (frequently annually laminated) sedimentary records (Cohen et al., 1993). We analyzed physical properties, grain size, total organic carbon, major, minor and trace element variability, and biogenic silica data for a 7.75 m core from the Kalya slope and horst region of central Lake Tanganyika at 640m water depth. Nine 14C dates provide an age model for the core, which spans ~62 cal kyr. Elemental concentrations preserved in Lake Tanganyika sediments record variability in deposition and runoff into the lake basin. Under conditions of rapid erosion, exposure and rapid weathering of bedrock has been shown to generate high concentrations of original silicate minerals enriched in soluble cations such as sodium and potassium, elements that are also biologically conservative. Prior to 40ka cal yr. core sediments are characterized by high magnetic susceptibility, intermediate levels of organic carbon, low to intermediate levels of biogenic silica, and fine grain size, indicative of relatively high precipitation. There is a profound decrease in magnetic susceptibility, a decrease in organic carbon and an increase in grain size at 40ka cal yr, which persists until ~16ka cal yr. Seismic

Can ipids in lake sediments help to reconstruct changes in methane availability and methane fluxes in boreal and temperate lakes?

NASA Astrophysics Data System (ADS)

Stoetter, T.; van Hardenbroek, M.; Rinta, P.; Schilder, J.; Schubert, C. J.; Heiri, O.

2013-12-01

source, which would lead to increasing abundances of MOB produced FAs in the sediment. The presence or absence of oxygen above the sediments seems to have a strong effect on these relationships. In lakes with oxic bottom water, the abundance of depleted FAs shows a stronger rise with increasing CH4 concentrations than in lakes with anoxic bottom waters, suggesting that aerobic CH4 oxidizers are an important source of these depleted FAs. With increasing CH4 concentrations, for example just above the sediment, we find more depleted values in C16:1ω7 and C18:1ω7. This correlation is only strong if we exclude lakes with a strong terrestrial influence. Our preliminary analysis of FAs in surface sediment samples showed clear relations to CH4 parameters measured in the examined lake ecosystems suggesting that it may be possible to use FA analysis of lake sediment records as a proxy for CH4 availability in lakes. However, our results also show that oxygen conditions at the sediment-water interface and organic matter imported from the lake catchment can have a strong effect.

Holocene Record of Major and Trace Components in the Sediments of an Urban Impoundment on the Mississippi River: Lake Pepin, Minnesota and Wisconsin

USGS Publications Warehouse

Dean, Walter E.

2009-01-01

Lake Pepin is a natural impoundment formed by damming of the Mississippi River about 9,180 radiocarbon years ago (19,600 calendar years) by an alluvial fan deposited by the Chippewa River, a tributary of the Mississippi in Wisconsin. Unique among 26 Mississippi River impoundments, Lake Pepin has stratigraphically preserved Holocene materials, including pollutants, that have been transported down the Mississippi. This natural Holocene record can then be compared to changes that have occurred since European settlement (ca. AD 1830), and since enactment of clean air and water legislation. The most immediate response to settlement in the sediments of Lake Pepin was an increase in bulk-sediment accumulation rate. This was accompanied by gradual increases in concentrations of phosphorus (P), and organic carbon (OC), followed by dramatic increases in these elements beginning about 1940. The increase in P was far greater than any of the minor fluctuations in P that occurred throughout the Holocene, but the increase in OC was comparable to an increase in OC that occurred in the mid-Holocene. The concentrations of several metals (for example, cadmium [Cd], and lead [Pb]) also are elevated in recent sediments. Increased Cd concentrations lasted only about two decades during the industrial era between World War II and the enactment of clean water standards in the 1970s. Increased Pb emissions, on the other hand, occurred over more than 100 years, first from burning of coal and smelting of lead ores, and then, beginning in the 1930s, burning of leaded gasoline. Concentrations of Pb in the sediments of Lake Pepin decreased to about two times preindustrial levels within a decade of enactment of unleaded gasoline restrictions.

Lake deposits record evidence of large post-1505 AD earthquakes in western Nepal

NASA Astrophysics Data System (ADS)

Ghazoui, Z.; Bertrand, S.; Vanneste, K.; Yokoyama, Y.; Van Der Beek, P.; Nomade, J.; Gajurel, A.

2016-12-01

According to historical records, the last large earthquake that ruptured the Main Frontal Thrust (MFT) in western Nepal occurred in 1505 AD. Since then, no evidence of other large earthquakes has been found in historical records or geological archives. In view of the catastrophic consequences to millions of inhabitants of Nepal and northern India, intense efforts currently focus on improving our understanding of past earthquake activity and complement the historical data on Himalayan earthquakes. Here we report a new record, based on earthquake-triggered turbidites in lakes. We use lake sediment records from Lake Rara, western Nepal, to reconstruct the occurrence of seismic events. The sediment cores were studied using a multi-proxy approach combining radiocarbon and 210Pb chronologies, physical properties (X-ray computerized axial tomography scan, Geotek multi-sensor core logger), high-resolution grain size, inorganic geochemistry (major elements by ITRAX XRF core scanning) and bulk organic geochemistry (C, N concentrations and stable isotopes). We identified several sequences of dense and layered fine sand mainly composed of mica, which we interpret as earthquake-triggered turbidites. Our results suggest the presence of a synchronous event between the two lake sites correlated with the well-known 1505 AD earthquake. In addition, our sediment records reveal five earthquake-triggered turbidites younger than the 1505 AD event. By comparison with historical archives, we relate one of those to the 1833 AD MFT rupture. The others may reflect successive ruptures of the Western Nepal Fault System. Our study sheds light on events that have not been recorded in historical chronicles. Those five MMI>7 earthquakes permit addressing the problem of missing slip on the MFT in western Nepal and reevaluating the risk of a large earthquake affecting western Nepal and North India.

Holocene environmental and climatic change in the Northern Great Plains as recorded in the geochemistry of sediments in Pickerel Lake, South Dakota

USGS Publications Warehouse

Dean, W.E.; Schwalb, A.

2000-01-01

The sediments in Pickerel Lake, northeastern South Dakota, provide a continuous record of climatic and environmental change for the last 12000 yr. Sediments deposited between 12 and 6 ka (radiocarbon) show extreme variations in composition, oxygen and carbon isotopic composition of bulk carbonate, carbon isotopic composition of organic matter, and magnetic susceptibility. These variations reflect changes in sources of moisture, regional vegetation types, precipitation-evaporation balance, ground- and surface-water influx, water residence time, erosion, lake productivity, water level, and water temperature. The total carbonate content of late Pleistocene sediments steadily increased from <20% at the base of the core to as much as 80% in sediments deposited between 11 and 9 ka. By about 8 ka, the total carbonate content of the sediments had declined to about 40% where it remained with little variation for the past 8 kyr, suggesting relatively stable conditions. There are marked increases in values of ??13C and ??18O in bulk carbonate, and ??13C of organic matter, in sediments deposited between 10 and 6 ka as evaporation increased, and the vegetation in the watershed changed from forest to prairie. This shift toward more 18O-enriched carbonate may also reflect a change in source or seasonality of precipitation. During this early Holocene interval the organic carbon (OC) content of the sediments remained relatively low (2-3%), but then increased rapidly to 4.5% between 7 and 6 ka, reflecting the rapid transition to a prairie lake. The OC content fluctuates slightly between 4 and 6% in sediments deposited over the past 6 kyr. Like OC and total carbonate, most variables measured show little variation in the 13 m of sediment deposited over the past 6 kyr, particularly when compared with early Holocene variations. Although the magnetic susceptibility of this upper 13 m of sediment is generally low (<10 SI units), the upper six meters of the section is marked by striking 1

Isotopic fingerprints of anthropogenic molybdenum in lake sediments.

PubMed

Chappaz, Anthony; Lyons, Timothy W; Gordon, Gwyneth W; Anbar, Ariel D

2012-10-16

We measured the molybdenum isotope compositions (δ(98)Mo) of well-dated sediment cores from two lakes in eastern Canada in an effort to distinguish between natural and anthropogenic contributions to these freshwater aquatic systems. Previously, Chappaz et al. (1) ascribed pronounced 20th-century Mo concentration enrichments in these lakes to anthropogenic inputs. δ(98)Mo values in the deeper sediments (reflecting predominantly natural Mo sources) differ dramatically between the two lakes: -0.32 ± 0.17‰ for oxic Lake Tantare and +0.64 ± 0.09‰ for anoxic Lake Vose. Sediment layers previously identified as enriched in anthropogenic Mo, however, reveal significant δ(98)Mo shifts of ± 0.3‰, resulting in isotopically heavier values of +0.05 ± 0.18‰ in Lake Tantare and lighter values of +0.31 ± 0.03‰ in Lake Vose. We argue that anthropogenic Mo modifies the isotopic composition of the recent sediments, and we determine δ(98)Mo(anthropogenic) values of 0.1 ± 0.1‰ (Lake Vose) and 0.2 ± 0.2‰ (Lake Tantare). These calculated inputs are consistent with the δ(98)Mo of molybdenite (MoS(2)) likely delivered to the lakes via smelting of porphyry copper deposits (Lake Vose) or through combustion of coal and oil also containing Mo (Lake Tantare). Our results confirm the utility of Mo isotopes as a promising fingerprint of human impacts and perhaps the specific sources of contamination. Importantly, the magnitudes of the anthropogenic inputs are large enough, relative to the natural Mo cycles in each lake, to have an impact on the microbiological communities.

A rock-magnetic record from Lake Baikal, Siberia: Evidence for Late Quaternary climate change

USGS Publications Warehouse

Peck, J.A.; King, J.W.; Colman, Steven M.; Kravchinsky, V.A.

1994-01-01

Rock-magnetic measurements of sediment cores from the Academician Ridge region of Lake Baikal, Siberia show variations related to Late Quaternary climate change. Based upon the well-dated last glacial-interglacial transition, variations in magnetic concentration and mineralogy are related to glacial-interglacial cycles using a conceptual model. Interglacial intervals are characterized by low magnetic concentrations and a composition that is dominated by low coercivity minerals. Glacial intervals are characterized by high magnetic concentrations and increased amounts of high coercivity minerals. The variation in magnetic concentration is consistent with dilution by diatom opal during the more productive interglacial periods. We also infer an increased contribution of eolian sediment during the colder, windier, and more arid glacial conditions when extensive loess deposits were formed throughout Europe and Asia. Eolian transport is inferred to deliver increased amounts of high coercivity minerals as staining on eolian grains during the glacial intervals. Variations in magnetic concentration and mineralogy of Lake Baikal sediment correlate to the SPECMAP marine oxygen-isotope record. The high degree of correlation between Baikal magnetic concentration/mineralogy and the SPECMAP oxygen-isotope record indicates that Lake Baikal sediment preserves a history of climate change in central Asia for the last 250 ka. This correlation provides a method of estimating the age of sediment beyond the range of the radiocarbon method. Future work must include providing better age control and additional climate proxy data, thereby strengthening the correlation of continental and marine climate records. ?? 1994.

Diatoms in sediments of perennially ice-covered Lake Hoare, and implications for interpreting lake history in the McMurdo Dry Valleys of Antarctica

USGS Publications Warehouse

Spaulding, S.A.; McKnight, Diane M.; Stoermer, E.F.; Doran, P.T.

1997-01-01

Diatom assemblages in surficial sediments, sediment cores, sediment traps, and inflowing streams of perennially ice-covered Lake Hore, South Victorialand, Antarctica were examined to determine the distribution of diatom taxa, and to ascertain if diatom species composition has changed over time. Lake Hoare is a closed-basin lake with an area of 1.8 km2, maximum depth of 34 m, and mean depth of 14 m, although lake level has been rising at a rate of 0.09 m yr-1 in recent decades. The lake has an unusual regime of sediment deposition: coarse grained sediments accumulate on the ice surface and are deposited episodically on the lake bottom. Benthic microbial mats are covered in situ by the coarse episodic deposits, and the new surfaces are recolonized. Ice cover prevents wind-induced mixing, creating the unique depositional environment in which sediment cores record the history of a particular site, rather than a lake=wide integration. Shallow-water (<1 m) diatom assemblages (Stauroneis anceps, Navicula molesta, Diadesmis contenta var. parallela, Navicula peraustralis) were distinct from mid-depth (4-16 m) assemblages (Diadesmis contenta, Luticola muticopsis fo. reducta, Stauroneis anceps, Diadesmis contenta var. parallela, Luticola murrayi) and deep-water (2-31 m) assemblages (Luticola murrayi, Luticola muticopsis fo. reducta, Navicula molesta. Analysis of a sediment core (30 cm long, from 11 m water depth) from Lake Hoare revealed two abrupt changes in diatom assemblages. The upper section of the sediment core contained the greatest biomass of benthic microbial mat, as well as the greatest total abundance and diversity of diatoms. Relative abundances of diatoms in this section are similar to the surficial samples from mid-depths. An intermediate zone contained less organic material and lower densities of diatoms. The bottom section of core contained the least amount of microbial mat and organic material, and the lowest density of diatoms. The dominant process

A half-million-year record of paleoclimate from the Lake Manix Core, Mojave Desert, California

USGS Publications Warehouse

Reheis, Marith C.; Bright, Jordon; Lund, Steve P.; Miller, David M.; Skipp, Gary; Fleck, Robert J.

2012-01-01

Pluvial lakes in the southwestern U.S. responded sensitively to past climate through effects on rainfall, runoff, and evaporation. Although most studies agree that pluvial lakes in the southwestern U.S. reached their highest levels coeval with glacial stages, the specific timing of increased effective moisture and lake-level rise is debated, particularly for the southwesternmost lakes. We obtained a 45-m core of lacustrine sediment from Lake Manix, the former terminus of the Mojave River prior to about 25 ka, and supplemented data from the core with outcrop studies. These sediments provide a robust record of Mojave River discharge over the last half-million years. Lake Manix persisted from OIS 12 through early OIS 2, including during interstadial OIS 3 and interglacials OIS 5, 7, and 9. The ostracode faunal record displays a shift from an unexpectedly warm, summer-dominated lake hydrology during OIS 12 to predominantly colder, winter-dominated conditions afterwards. The ostracode-based stable isotope record displays a large degree of intra-sample variability and does not mimic other well-known isotopic records of climate change. Evaporation likely buffered the Manix δ18O record from most of the expected isotopic differences between interglacial and glacial-interval discharge. Isotopically depleted and stable lakes occurred only four to six times, most notably during OIS 7 and OIS 9. Internal drainage-basin changes also affected the isotopic record. Persistence of lakes in the Manix basin during interglacials requires atmospheric or oceanic circulation controls on the mean position of the Pacific storm track other than large ice sheets. We propose that the relative strength and sign of the Northern Annular Mode (NAM) and its influence on atmospheric river-derived precipitation is a potential explanation.

Dating of palaeomagnetic secular variation in Swedish varved lake sediments using radiocarbon wiggle-matching

NASA Astrophysics Data System (ADS)

Mellström, Anette; Nilsson, Andreas; Stanton, Tania; Muscheler, Raimund; Snowball, Ian

2013-04-01

Well-dated natural archives are crucial when investigating the timing between climate change and climate forcing. Annually laminated (varved) lake sediments, in particular, can provide valuable knowledge about past climatic and environmental conditions as the annual nature of the sediments enables the establishment of high-resolution archives. In addition, lake sediments can record variations in the Earth's magnetic field, which has the potential to be used as a dating validation technique if the palaeo-secular and -intensity curves are dated correctly. If individual and well-defined geomagnetic events can be dated accurately, they can then be used as isochrones, thereby allowing the synchronisation of different records. We therefore aim to date the "f" event, a late Holocene secular variation change, which is recorded in many sites in the northern hemisphere. Varved sites in Sweden have dated the "f" event to ~2700 cal. yrs BP. In order to constrain this date further, we have used the radiocarbon wiggle-matching method on a lake in central west Sweden, Kälksjön (Stanton et al., 2010), whose chronology has previously been validated using a number of complimentary dating methods. With the radiocarbon wiggle-matching technique, closely spaced samples are measured and matched to distinct wiggles in the radiocarbon calibration curve. The advantage of using varve-dated sediments is that it is possible to know the exact number of years between each sample, and therefore improve the initial age model. We compare the wiggle-match results of Kälksjön with results from a newly discovered varved lake sediment sequence in southern Sweden, Gyltigesjön. This comparison can provide information about magnetisation processes in sediments, such as the length of the palaeomagnetic lock-in delay. Stanton, T., Snowball, I., Zillén, L., Wastegård, S., 2010. Validating a Swedish varve chronology using radiocarbon, palaeomagnetic secular variation, lead pollution history and

Volcanic influence of Mt. Fuji on the watershed of Lake Motosu and its impact on the lacustrine sedimentary record

NASA Astrophysics Data System (ADS)

Lamair, Laura; Hubert-Ferrari, Aurélia; Yamamoto, Shinya; El Ouahabi, Meriam; Vander Auwera, Jacqueline; Obrochta, Stephen; Boes, Evelien; Nakamura, Atsunori; Fujiwara, Osamu; Shishikura, Masanobu; Schmidt, Sabine; Siani, Giuseppe; Miyairi, Yosuke; Yokoyama, Yusuke; De Batist, Marc; Heyvaert, Vanessa M. A.; QuakeRecNankai Team

2018-01-01

Lacustrine sediments are particularly sensitive to modifications within the lake catchment. In a volcanic area, sedimentation rates are directly affected by the history of the volcano and its eruptions. Here, we investigate the impact of Mt. Fuji Volcano (Japan) on Lake Motosu and its watershed. The lacustrine infill is studied by combining seismic reflection profiles and sediment cores. We show evidence of changes in sedimentation patterns during the depositional history of Lake Motosu. The frequency of large mass-transport deposits recorded within the lake decreases over the Holocene. Before 8000 cal yr BP, large sublacustrine landslides and turbidites were filling the lacustrine depression. After 8000 cal yr BP, only one large sublacustrine landslide was recorded. The change in sedimentation pattern coincides with a change in sediment accumulation rate. Over the last 8000 cal yr BP, the sediment accumulation rate was not sufficient enough to produce large sublacustrine slope failures. Consequently, the frequency of large mass-transport deposits decreased and only turbidites resulting from surficial slope reworking occurred. These constitute the main sedimentary infill of the deep basin. We link the change in sediment accumulation rate with (i) climate and vegetation changes; and (ii) the Mt. Fuji eruptions which affected the Lake Motosu watershed by reducing its size and strongly modified its topography. Moreover, this study highlights that the deposition of turbidites in the deep basin of Lake Motosu is mainly controlled by the paleobathymetry of the lakefloor. Two large mass-transport deposits, occurring around 8000 cal yr BP and 2000 cal yr BP respectively, modified the paleobathymetry of the lakefloor and therefore changed the turbidite depositional pattern of Lake Motosu.

Erosion under climate and human pressures: An alpine lake sediment perspective

NASA Astrophysics Data System (ADS)

Arnaud, Fabien; Poulenard, Jérôme; Giguet-Covex, Charline; Wilhelm, Bruno; Révillon, Sidonie; Jenny, Jean-Philippe; Revel, Marie; Enters, Dirk; Bajard, Manon; Fouinat, Laurent; Doyen, Elise; Simonneau, Anaëlle; Pignol, Cécile; Chapron, Emmanuel; Vannière, Boris; Sabatier, Pierre

2016-11-01

We review the scientific efforts over the last decades to reconstruct erosion from continuous alpine lake sediment records. We focused both on methodological issues, showing the growing importance of non-destructive high resolution approaches (XRF core-scanner) as well as progresses in the understanding of processes leading to the creation of an "erosion signal" in lakes. We distinguish "continuous records" from "event-records". Both provide complementary information but need to be studied with different approaches. Continuous regionally-relevant records proved to be particularly pertinent to document regional erosion patterns throughout the Holocene, in particular applying the source to sink approach. Event-based approaches demonstrated and took advantage of the strong non-linearity of sediment transport in high altitude catchment areas. This led to flood frequency and intensity reconstructions, highlighting the influence of climate change upon flood dynamics in the mountain. The combination of different record types, both in terms of location (high vs. low elevation), sedimentology (high vs. low terrigenous contribution) and significance (local vs. regional) is one of the main outputs of this paper. It allows the establishment of comprehensive histories of NW French Alps erosion, but also and consequently, soil dynamics and hydrological patterns throughout the Holocene. We also discuss the influence of glacier dynamics, one of the major agents of erosion in the Alps. A major feature is the growing human influence upon erosion at a local scale since at least the middle of the Bronze Age (3500 cal. BP). However and according to the regional record from Lake Bourget, only few periods of rising erosion at local scales generated a regional record that can be discriminated from wetter climatic periods. Among them, the period between 200 BCE and 400 AD appeared to be marked by a generalised rise in human-triggered erosion at local scales in the northern French Alps

Manganese and iron geochemistry in sediments underlying the redox-stratified Fayetteville Green Lake

NASA Astrophysics Data System (ADS)

Herndon, Elizabeth M.; Havig, Jeff R.; Singer, David M.; McCormick, Michael L.; Kump, Lee R.

2018-06-01

Manganese and iron are redox-sensitive elements that yield clues about biogeochemistry and redox conditions both in modern environments and in the geologic past. Here, we investigated Mn and Fe-bearing minerals preserved in basin sediments underlying Fayetteville Green Lake, a redox-stratified lake that serves as a geochemical analogue for Paleoproterozoic oceans. Synchrotron-source microprobe techniques (μXRF, μXANES, and μXRD) and bulk geochemical analyses were used to examine the microscale distribution and speciation of Mn, Fe, and S as a function of depth in the top 48 cm of anoxic lake sediments. Manganese was primarily associated with calcite grains as a manganese-rich carbonate that precipitated in the chemocline of the water column and settled through the euxinic basin to collect in lake sediments. Iron was preserved in framboidal iron sulfides that precipitated in euxinic bottom waters and underwent transformation to pyrite and marcasite in the sediments. Previous studies attribute the formation of manganese-rich carbonates to the diagenetic alteration of manganese oxides deposited in basins underlying oxygenated water. Our study challenges this paradigm by providing evidence that Mn-bearing carbonates form in the water column and accumulate in sediments below anoxic waters. Consequently, manganoan carbonates preserved in the rock record do not necessarily denote the presence of oxygenated bottom waters in ocean basins.

Contaminated Sediment in the Great Lakes

EPA Pesticide Factsheets

Contaminated sediments are a significant problem in the Great Lakes basin. Persistent high concentrations of contaminants in the bottom sediments of rivers and harbors pose risks to aquatic organisms, wildlife, and humans.

Varves in lake sediments - a review

NASA Astrophysics Data System (ADS)

Zolitschka, Bernd; Francus, Pierre; Ojala, Antti E. K.; Schimmelmann, Arndt

2015-06-01

Downcore counting of laminations in varved sediments offers a direct and incremental dating technique for high-resolution climatic and environmental archives with at least annual and sometimes even seasonal resolution. The pioneering definition of varves by De Geer (1912) had been restricted to rhythmically deposited proglacial clays. One century later the meaning of 'varve' has been expanded to include all annually deposited laminae in terrestrial and marine settings. Under favourable basin configurations and environmental conditions, limnic varves are formed due to seasonality of depositional processes from the lake's water column and/or transport from the catchment area. Subsequent to deposition of topmost laminae, the physical preservation of the accumulating varved sequence requires the sustained absence of sediment mixing, for example via wave action or macrobenthic bioturbation. Individual (sub)laminae in varved lake sediments typically express contrasting colours, always differ in terms of their organic, chemical and/or mineralogical compositions, and often also differ with regard to grain-size. Various predominating climatic and depositional conditions may result in clastic, biogenic or endogenic (incl. evaporitic) varved sediments and their mixtures. To reliably establish a varve chronology, the annual character of laminations needs to be determined and verified in a multidisciplinary fashion. Sources and influences of possible errors in varve chronologies are best determined and constrained by repeated varve counts, and by including radioisotopes and correlation with historically documented events. A well-established varve chronology greatly enhances the scientific value of laminated limnic archives by securely anchoring the wealth of multi-proxy palaeoenvironmental information in the form of time-series for multidisciplinary investigations. Applications of varved records are discussed with special reference to advances since the 1980s. These span fields

Early- to Mid-Holocene hydroclimate shifts in tropical East Africa: the multi-proxy sediment record from Lake Rutundu, Kenya

NASA Astrophysics Data System (ADS)

De Cort, Gijs; Creutz, Mike; Barao, Lucia; Conley, Daniel; Haug, Gerald; Bodé, Samuel; Blaauw, Maarten; Engstrom, Dan; Verschuren, Dirk

2015-04-01

Following the generally arid conditions of the Last Glacial Maximum (LGM), a large part of the African continent experienced the Early to Mid-Holocene as a much more humid period than today. This so-called African Humid Period (AHP) coincided with high summertime insolation over the Northern Hemisphere subtropics, causing invigorated monsoons to create moist conditions over the northern parts of the continent. Similarly, equatorial and even low-latitude southeastern Africa experienced a wetter climate due to the post-glacial increase in atmospheric greenhouse gasses ultimately leading to altered Atlantic and Indian Ocean monsoon dynamics. The timing and abruptness of the onset and ending of the AHP in the different regions of the continent have been the subject of major discussion. On the other hand, shorter-lived climate fluctuations within the AHP have received much less attention, due to a scarcity of well-dated, high-resolution African paleoclimate records spanning the entire Holocene. In this study we used the sediment record of Lake Rutundu, a high-altitude crater lake on Mount Kenya, to document multidecadal to millennial-scale hydroclimate variability on the East African equator from the LGM to the present. A multiproxy approach combining core-surface scanning techniques (magnetic susceptibility, X-ray fluorescence) and close-interval bulk-sediment analyses (organic matter and biogenic Si content, grain size, organic δ15N and δ13C) resulted in a high-resolution record firmly anchored in time by an age model based on 210Pb dating and sixteen calibrated radiocarbon ages. This new Lake Rutundu hydroclimate record confirms that moister conditions following the LGM returned to East Africa ca.16 kyr BP, and it contains a perfectly timed Younger Dryas episode (12.8-11.5 kyr BP) of intermittent drought. We find that the Early- to Mid-Holocene period, which in African records is often described as uniformly wet, was in fact punctuated by three distinct, century

High Resolution Environmental Magnetic Study of a Holocene Sedimentary Record from Zaca Lake, Ca

NASA Astrophysics Data System (ADS)

Platzman, E. S.; Lund, S.; Kirby, M. E.; Feakins, S. J.

2012-12-01

Magnetic studies of Holocene lake sediments recovered from Zaca lake have yielded a 3000-year high resolution record of environmental variability and paleolimnology. Zaca lake is a small oligomictic lake ~12m deep situated 730 m above sea level in the steep canyons of the San Rafael mountains, NW of Santa Barbara. Throughout much of the year Zaca lake is anaerobic below 7m. Hydrogen sulfide, fed into the lake via runoff and local sulphur springs, is present throughout the hypolimnion with concentrations sometime exceeding 30 mg/ l. During the summer months when the lake is stratified, light colored carbonate rich microlaminae are formed; and often during the winter months when the lake overturns, killing the anaerobic bacteria, black microlamina rich in iron sulfide are deposited on the lake floor, creating a stratigraphy reflecting patterns of environmental variability on annual to millennial scales. Samples for magnetic analysis were obtained from 8.5 m of core recovered from the central region of Zaca lake. Ages, constrained using radiocarbon chronostratigraphy, yielded sedimentation rates of 2-10 mm/yr with an average rate of 3 mm per yr over the 3000 yr interval. Parameters reflecting decadal scale variability in magnetic concentration (susceptibility, ARM, SIRM) and grainsize (ARM/Chi) were measured every 2 cm. Additional rock magnetic tests, including thermal demagnetization of three component IRM, were applied at selected intervals to constrain the magnetic mineralogy. These data were combined with analyses of clastic grain size, % calcium carbonate and % organics to create a multiproxy record of environmental variability. Results show that Zaca lake has had a complex depositional history. Anthropogenic effects associated with European colonization are present in the upper meters. Most notable, however, is a dramatic shift in the magnetic parameters and mineralogy between the upper and lower half of the core (circa 1300 ybp) indicating a shift in regime

Constraining Resurgence through Lake Sediment Paleomagnetism on Resurgent Dome Samosir Island in Toba Caldera, Sumatra, Indonesia

NASA Astrophysics Data System (ADS)

Solada, K.; de Silva, S. L.; Stoner, J. S.; Mucek, A. E.; Reilly, B. T.; Hatfield, R. G.; Pratomo, I.; Bowers, J.; Jamil, R.; Setianto, B.

2017-12-01

Around 74 ka, a supervolcano, Toba Caldera in Sumatra, Indonesia erupted, producing the Youngest Toba Tuff and its associated caldera. After this catastrophic eruption, a lake filled the caldera, sedimentation within the lake occurred, and the process known as resurgence began. Today, the resurgent dome, Samosir Island, is uplifted 700 m above the lake with the upper 100 m composed of these post eruption lake sediments. These sediments and their ages offer insight to the resurgent uplift history. To constrain sediment chronology, we collected discrete paleomagnetic 8 cm3 cubes and 43 radiocarbon samples from 10 sites around the island. Bulk organic carbon 14C ages provide an initial chronostratigraphic framework, which is improved by correlating paleomagnetic signals between site sections. Additionally, nearby marine sediment paleomagnetic records show large amplitude changes in inclination over the past 74 ka, providing a good template to compare the sediment chronology. 27 radiocarbon samples have already been dated, with the oldest dating at 38 ka. However, our radiocarbon and paleomagnetic correlation suggest that this record extends even older. Natural and laboratory magnetizations on discrete samples were studied using alternating field (AF) demagnetization at the Oregon State University P-Mag Lab. Although there is variability in magnetic susceptibility between study sites and natural remanant magnetization intensities are often relatively low ( 10-4 (A/m)), AF demagnetization behavior suggests a primary magnetization is recorded. Characteristic remanent magnetizations are reasonably well-defined using a principal component analysis with maximum angular deviation values < 15°, though stronger samples typically have better resolved magnetizations. Data from 4 sites with 14C ages ranging from 23 ka to 38 ka, show low inclination values, averaging around -5° compared with geocentric axial dipole prediction for the site location of approximately 4°. This is

Microplastic pollution in Vembanad Lake, Kerala, India: The first report of microplastics in lake and estuarine sediments in India.

PubMed

Sruthy, S; Ramasamy, E V

2017-03-01

We present the first study of microplastics in the sediments of Vembanad Lake, a Ramsar site in India. Microplastics are emerging pollutants of increasing environmental concern with a particle size of <5 mm, which originate from successive degradation of larger plastic debris or are manufactured as small granules and used in many applications. The impact of microplastics pollution on the environment and biota is not well known. Vast data exist in the literature on marine microplastics while reports on freshwater ecosystems are scarce. In this context, to examine the occurrence of microplastic particles (MPs) in the Vembanad Lake, samples were collected from ten sites and processed for microplastic extraction through density separation. Identification of the polymer components of MPs was done using micro Raman spectroscopy. MPs were recovered from all sediment samples, indicating their extensive distribution in the lake. The abundance of MPs recorded from the sediment samples is in the range of 96-496 particles m -2 with a mean abundance of 252.80 ± 25.76 particles m -2 . Low density polyethylene has been identified as the dominant type of polymer component of the MPs. As clams and fishes are the major source of protein to the local population, the presence of MPs in the lake becomes critically important, posing a severe threat of contaminating the food web of this lake. This study, being the first report from India on MPs in lake sediments, provide impetus for further research on the distribution and impact of this emerging pollutant on the biota of many aquatic systems spread across India. Copyright © 2016 Elsevier Ltd. All rights reserved.

Suspended-sediment budget, flow distribution, and lake circulation for the Fox Chain of Lakes in Lake and McHenry Counties, Illinois, 1997-99

USGS Publications Warehouse

Schrader, David L.; Holmes, Robert R.

2000-01-01

The Fox Chain of Lakes is a glacial lake system in McHenry and Lake Counties in northern Illinois and southern Wisconsin. Sedimentation and nutrient overloading have occurred in the lake system since the first dam was built (1907) in McHenry to raise water levels in the lake system. Using data collected from December 1, 1997, to June 1, 1999, suspended-sediment budgets were constructed for the most upstream lake in the system, Grass Lake, and for the lakes downstream from Grass Lake. A total of 64,900 tons of suspended sediment entered Grass Lake during the study, whereas a total of 70,600 tons of suspended sediment exited the lake, indicating a net scour of 5,700 tons of sediment. A total of 44,100 tons of suspended sediment was measured exiting the Fox Chain of Lakes at Johnsburg, whereas 85,600 tons entered the system downstream from Grass Lake. These suspended-sediment loads indicate a net deposition of 41,500 tons downstream from Grass Lake, which represents a trapping efficiency of 48.5 percent. A large amount of recreational boating takes place on the Fox Chain of Lakes during summer months, and suspended-sediment load was observed to rise from 110 tons per day to 339 tons per day during the 1999 Memorial Day weekend (May 26 ?31, 1999). Presumably, this rise was the result of the boating traffic because no other hydrologic event is known to have occurred that might have caused the rise. This study covers a relatively short period and may not represent the long-term processes of the Fox Chain of Lakes system, although the sediment transport was probably higher than an average year. The bed sediments found on the bottom of the lakes are composed of mainly fine particles in the silt-clay range. The Grass Lake sediments were characterized as black peat with an organic content of between 9 and 18 percent, and the median particle size ranged from 0.000811 to 0.0013976 inches. Other bed material samples were collected at streamflow-gaging stations on the

Mineralogic Causes of Variations in Magnetic Susceptibility of Late Pleistocene and Holocene Sediment from Great Salt Lake, Utah

USGS Publications Warehouse

Reynolds, Richard L.; Rosenbaum, Joseph G.; Thompson, Robert S.

2008-01-01

We describe here results of magnetic susceptibility (MS) measurements and magnetic mineralogy of sediments sampled in three cores from the south basin of Great Salt Lake. The cores were obtained in 1996 with a Kullenburg-type piston corer at sites in close proximity: core 96-4 at 41 deg 01.00' N, 112 deg 28.00' W and cores 96-5 and 96-6 at 41 deg 00.09' N, 112 deg 23.05' W. Cores 96-5 (2.16 m long) and -6 combine to make a composite 11.31-m sediment record. Sediments in core 96-4 (5.54 m long) correspond to the approximate depth interval of 3.9-9.6 m in the composite core of 96-5 and -6 based on similarities in the MS records as described below. The central goal of the research was to provide a sediment record of paleoenvironmental change in the northeastern Basin and Range Province over the past 40,000 years. Specific targets included a sedimentologic record of lake-level change combined with a pollen record of climatic change.

Greigite (Fe3S4) as an indicator of drought - The 1912-1994 sediment magnetic record from White Rock Lake, Dallas, Texas, USA

USGS Publications Warehouse

Reynolds, R.L.; Rosenbaum, J.G.; Van Metre, P.; Tuttle, M.; Callender, E.; Goldin, A.

1999-01-01

Combined magnetic and geochemical studies were conducted on sediments from White Rock Lake, a reservoir in suburban Dallas (USA), to investigate how land use has affected sediment and water quality since the reservoir was filled in 1912. The chronology of a 167-cm-long core is constrained by the recognition of the pre-reservoir surface and by 137Cs results. In the reservoir sediments, magnetic susceptibility (MS) and isothermal remanent magnetization (IRM) are largely carried by detrital titanomagnetite that originally formed in igneous rocks. Titanomagnetite and associated hematite are the dominant iron oxides in a sample from the surficial deposit in the watershed but are absent in the underlying Austin Chalk. Therefore, these minerals were transported by wind into the watershed. After about 1960, systematic decreases in Ti, Fe, and Al suggest diminished input of detrital Fe-Ti oxides from the surficial deposits. MS and IRM remain constant over this interval, however, implying compensation by an increase in strongly magnetic material derived from human activity. Anthropogenic magnetite in rust and ferrite spherules (from fly ash?) are more common in sediment deposited after about 1970 than before and may account for the constant magnetization despite the implied decrease in detrital Fe-Ti oxides. An unexpected finding is the presence of authigenic greigite (Fe3S4), the abundance of which is at least partly controlled by climate. Greigite is common in sediments that predate about 1975, with zones of concentration indicated by relatively high IRM/MS. High greigite contents in sediment deposited during the early to mid-1950s and during the mid-1930s correspond to several-year periods of below-average precipitation and drought from historical records. Relatively long water-residence times in the reservoir during these periods may have led to elevated levels of sulfate available for bacterial sulfate reduction. The sulfate was probably derived via the oxidation of

Late Pleistocene paleoclimatic history documented by an oxygen isotope record from carbonate sediments in Qarhan Salt Lake, NE Qinghai-Tibetan Plateau

NASA Astrophysics Data System (ADS)

Fan, QiShun; Ma, HaiZhou; Wei, HaiCheng; Shan, FaShou; An, FuYuan; Xu, LiMing; Madsen, David B.

2014-05-01

Late Pleistocene paleoclimatic variability on the northeastern Qinghai-Tibetan Plateau (NE QTP) was reconstructed using a chronology based on AMS 14C and 230Th dating results and a stable oxygen isotopic record. These are derived from lake carbonates in a 102-m-long Qarhan sediment core (ISL1A) collected from the eastern Qaidam Basin. Previous research indicates that the δ18O values of lacustrine carbonates are mainly controlled by the isotopic composition of lake water, which in turn is a function of regional P/E balance and the proportion of precipitation that is monsoon-derived on the NE QTP. Modern isotopic observations indicate that the δ18O values of lake carbonates in hyper-arid Qaidam Basin are more positive during the warm and wet period. Due to strong evaporation and continental effect in this basin, the positive δ18O values in the arid region indicate drier climatic conditions. Based on this interpretation and the δ18O record of fine-grained lake carbonates and dating results in ISL1A, the results imply that drier climatic conditions in the Qarhan region occurred in three intervals, around 90-80 ka, 52-38 ka and 10-9 ka, which could correspond to late MIS 5, middle MIS 3 and early Holocene, respectively. These three phases were almost coincided with low lake level periods of Gahai, Toson and Qinghai Lakes (to the east of Qarhan Lake) influenced by ASM on the orbital timescales. Meanwhile, there was an episode of relatively high δ18O value during late MIS 3, suggesting that relatively dry climatic condition in this period, rather than “a uniform Qarhan mega-paleolake” spanning the ˜44 to 22 ka period. These results insight into the understanding of “the Greatest Lake Period” on the QTP.

Phosphate mineral formation in Lake Baikal sediments and implications for paleoclimate

NASA Astrophysics Data System (ADS)

Fagel, N.; Alleman, L. Y.; André, L.; Cloots, R.; Hatert, F.; Juvigné, E.; Renson, V.

2003-04-01

The more than 20 million years old Lake Baikal sedimentary record provides a good climate archive. While most paleoclimate reconstructions are mainly based on biotic proxies, we tested in this study other minerogenic tracers. In particular, it was suggested that the formation of authigenic and/or diagenetic phosphate minerals in Baïkal sediments underlines transitions from glacial to interglacial periods (Deike et al., 1997). The phosphate mineral formation previously evidenced (Müller et al., 2002) may be sensitive to suspended sediment concentrations: glacial periods are characterised by high detrital discharge, interglacial intervals are marked by low detrital supply but high biogenic sedimentation. Phosphate minerals were observed in Baïkal sediments from recent to 65 kyr BP. Their abundance was related to the sedimentation rate, the phosphate enrichment layers being particularly common on low sedimentation site, i.e., the Academician Ridge. Major and trace elements have been analysed by ICP-AES and ICP-MS on four cores drilled on topographic hills, in the southern basin (Posolsky bank, CON01-604), in the central part (Academician Ridge, VER98-1-3 and VER98-1-14) and in the northern basin (Continent Ridge, CON01-603). The geochemical signature is consistent with the occurrence of Mn-Fe-phosphate minerals. For instance P2O5 reaches up to 3% wt. relative to a mean value of 0.3 in the background sediment, MnO2 presents an enrichment factor up to 6. There is no associated enrichment in any of the trace elements measured at the same levels. In the sediments, those P-Mn-Fe rich levels are related either to sparse millimetric dark concretions or to a layer (or a group of layers) defined by an alignment of numerous concretions but there is no so-called crusts. The concretions, isolated by >63 mm sieving, present a lamellar morphology. They are identified as Fe-phosphate phases with a variable proportion of Mn. The powder diffraction diagram is consistent with

Polycyclic aromatic hydrocarbons (PAHs) in surface sediments of two lakes of the Dongting Lake district in Hunan, China

NASA Astrophysics Data System (ADS)

He, Jiang; Yang, Yajing; Zhang, Lugang; Luo, Yushuang; Liu, Fei; Yang, Pinhong

2018-04-01

In this paper, 18 and 12 surface sediment samples were collected from Datong Lake and Shanpo Lake, respectively, and the 16 USEPA priority Polycyclic aromatic hydrocarbons (PAHs) in these samples were detected. The result indicated that the Σ16PAHs ranged from 206.56 to 1058.98 ng.g-1 with an average concentration of 667.22 ng.g-1 in sediments from Datong Lake, whereas it ranged from 90.62 to 900.70 ng.g-1 with an average concentration of 364.97 ng.g-1 in sediments from Shanpo Lake. The concentrations of individual PAHs in sediments ranged from 5.50 to 85.23 and from 4.39 to 52.74 ng.g-1 in Datong Lake and Shanpo Lake, respectively. According to the indexes such as HMW/LMW, Ant/(Ant+Phe), Flua/(Flua+Pyr), IcdP/(IcdP+BghiP), and BaA/(BaA+Chr), the PAHs in sediments from both lakes are mainly of pyrogenic origin. The total BaP equivalent in the surface sediment samples from Datong Lake and Shanpo Lake is 42.77 and 33.35 ng.g-1, respectively.

Modeling of sediment transport in a saltwater lake with supplemental sandy freshwater.

PubMed

Liang, Li; Deng, Yun; Li, Ran; Li, Jia

2018-06-22

Considering the highly complex flow structure of saltwater lakes during freshwater supplementation, a three-dimensional numerical model was developed to simulate suspended sediment transport in saltwater lakes. The model was validated using measurements of the salinity and sediment concentration during a pumping test at Yamdrok Lake. The simulation results were in quantitative agreement with the measured data. The observed and simulated results also indicated that the wind stress and vertical salinity gradient have a significant influence on salinity and sediment transport in a saltwater lake. The validated model was then used to predict and analyze the contributions of wind, the supplement flow rate and salinity stratification to the sediment transport process in Yamdrok Lake during continuous river water supplementation. The simulation results showed that after the sandy river water was continuously discharged into the saltwater lake, the lateral diffusion trends of the sediment exhibited three stages: linear growth in the inflow direction, logarithmic growth in the wind direction, and stabilization. Furthermore, wind was the dominant factor in driving the lake flow pattern and sediment transport. Specifically, wind can effectively reduce the area of the sediment diffusion zone by increasing the lateral sediment carrying and dilution capacities. The effect of inflow on the lake current is negligible, but the extent of the sediment turbidity zone mainly depends on the inflow. Reducing the inflow discharge can decrease the area of the sediment turbidity zone to proportions that far exceed the proportions of inflow discharge reductions. In addition, the high-salinity lake water can support the supplemented freshwater via buoyancy forces, which weaken vertical mixing and sediment settlement and increase lake currents and sediment diffusion near the surface.

Sediment delivery and lake dynamics in a Mediterranean mountain watershed: Human-climate interactions during the last millennium (El Tobar Lake record, Iberian Range, Spain).

PubMed

Barreiro-Lostres, Fernando; Brown, Erik; Moreno, Ana; Morellón, Mario; Abbott, Mark; Hillman, Aubrey; Giralt, Santiago; Valero-Garcés, Blas

2015-11-15

Land degradation and soil erosion are key environmental problems in Mediterranean mountains characterized by a long history of human occupation and a strong variability of hydrological regimes. To assess recent trends and evaluate climatic and anthropogenic impacts in these highly human modified watersheds we apply an historical approach combining lake sediment core multi-proxy analyses and reconstructions of past land uses to El Tobar Lake watershed, located in the Iberian Range (Central Spain). Four main periods of increased sediment delivery have been identified in the 8m long sediment sequence by their depositional and geochemical signatures. They took place around 16th, late 18th, mid 19th and early 20th centuries as a result of large land uses changes such as forest clearing, farming and grazing during periods of increasing population. In this highly human-modified watershed, positive synergies between human impact and humid periods led to increased sediment delivery periods. During the last millennium, the lake depositional and geochemical cycles recovered quickly after each sediment delivery event, showing strong resilience of the lacustrine system to watershed disturbance. Recent changes are characterized by large hydrological affections since 1967 with the construction of a canal from a nearby reservoir and a decreased in anthropic pressure in the watershed as rural areas were abandoned. The increased fresh water influx to the lake has caused large biological changes, leading to stronger meromictic conditions and higher organic matter accumulation while terrigenous inputs have decreased. Degradation processes in Iberian Range watersheds are strongly controlled by anthropic activities (land use changes, soil erosion) but modulated by climate-related hydrological changes (water availability, flood and runoff frequency). Copyright © 2015 Elsevier B.V. All rights reserved.

Site-dependent proxy response to climate change during the last 140 years observed in varved lake sediments in Northern Poland

NASA Astrophysics Data System (ADS)

Ott, Florian; Kramkowski, Mateusz; Wulf, Sabine; Plessen, Birgit; Serb, Johanna; Tjallingii, Rik; Schwab, Markus; Słowiński, Michał; Brykała, Dariusz; Tyszkowski, Sebastian; Putyrskaya, Victoria; Appelt, Oona; Błaszkiewicz, Mirosław; Brauer, Achim

2017-04-01

This accurate dating and chronological correlation using crypto-tephras provide a powerful way to compare the varved sediment records of the lakes Głęboczek (JG), Czechowskie (JC) and Jelonek (JEL) (north-central Poland). For the last 140 years, high-resolution varve micro-facies analyses (seasonal layer composition and thickness) and µ-XRF element scanning as well as bulk geochemical analyses (TOC, CaCO3) at sub-decadal to decadal resolution were conducted for all three records. Varve chronologies have been independently established by means of annual layer counting. 137Cs activity concentration measurements confirmed the varve chronology from JC. The Askja AD1875 tephra has been used to synchronize the records. A comparison of sediment data with monthly temperature data from Koszalin since 1870 and daily temperature data from Chojnice since 1951 revealed different responses of lake deposition to recent temperature change. Varves are well-preserved over the entire 140 years only in the sediments of JG, while in the JC record two faintly varved intervals are intercalated and in JEL two non-varved intervals occur at the base and top of the profile. These differences likely are due to variations in lake characteristics. Climate changes at the demise of the Little Ice Age and the recent warming since the 1980s are expressed in varve micro-facies, CaCO3 and TOC contents in the three lakes with different response times and amplitudes. This allows us to discuss the role of local parameters like lake size, bathymetry and water depth in transferring climate change signals into lake sediment records. This study is a contribution to the Virtual Institute of Integrated Climate and Landscape Evolution Analyses - ICLEA - of the Helmholtz Association, grant number VH-VI-415.

Linking hydro-climate to the sediment archive: a combined monitoring and calibration study from a varved lake in central Turkey

NASA Astrophysics Data System (ADS)

Roberts, C. Neil; Dean, Jonathan R.; Eastwood, Warren J.; Jones, Matthew D.; Allcock, Samantha L.; Leng, Melanie J.; Metcalfe, Sarah E.; Woodbridge, Jessie; Yiǧitbaşıoǧlu, Hakan

2016-04-01

Hydro-climatic reconstructions from lake sediment proxies require an understanding of modern formation processes and calibration over multiple years. Here we use Nar Gölü, a non-outlet, monomictic maar lake in central Turkey, as a field site for such a natural experiment. Fieldwork since 1997 has included observations and measurements of lake water and sediment trap samples, and automated data logging (Jones et al., 2005; Woodbridge and Roberts, 2010; Dean et al., 2015). We compare these data to isotopic, chemical and biotic proxies preserved in the lake's annually-varved sediments. Nar Gölü underwent a 3 m lake-level fall between 2000 and 2010, and δ18O in both water and carbonates is correlated with this lake-level fall, responding to the change in water balance. Over the same period, sedimentary diatom assemblages responded via changes in habitat availability and mixing regime, while conductivity inferred from diatoms showed a rise in inferred salinity, although with a non-linear response to hydro-climatic forcing. There were also non-linear shifts in carbonate mineralogy and elemental chemistry. Building on the relationship between lake water balance and the sediment isotope record, we calibrated sedimentary δ18O against local meteorological records to derive a P/E drought index for central Anatolia. Application to of this to the longer sediment core isotope record from Nar Gölü (Jones et al. 2006) highlights major drought events over the last 600 years (Yiǧitbaşıoǧlu et al., 2015). Although this lacustrine record offers an archive of annually-dated, decadally-averaged hydro-climatic change, there were also times of non-linear lake response to climate. Robust reconstruction therefore requires understanding of physical processes as well as application of statistical correlations. Dean, J.R., Eastwood, W.J., Roberts, N., Jones, M.D., Yiǧitbaşıoǧlu, H., Allcock, S.L., Woodbridge, J., Metcalfe, S.E. and Leng, M.J. (2015) Tracking the hydro

Non-Destructive High-Resolution Organic Matter Record on Lake Sediment using Steady-State Solid Phase Fluorescence: Organic Matter Quality and Quantity Assessment.

NASA Astrophysics Data System (ADS)

Quiers, M.; Perrette, Y.; Etienne, D.; Develle, A. L.; Jacq, K.

2017-12-01

The use of organic proxies increases in paleoenvironmental reconstructions from natural archives. Major advances have been achieved by the development of new highly informative molecular proxies usually linked to specific compounds. While studies focused on targeted compounds, offering a high information degree, advances on bulk organic matter are limited. However, this bulk is the main contributor to carbon cycle and has been shown to be a driver of many mineral or organic compounds transfer and record. Development of target proxies need complementary information on bulk organic matter to understand biases link to controlling factors or analytical methods, and provide a robust interpretation. Fluorescence methods have often been employed to characterize and quantify organic matter. However, these technics are mainly developed for liquid samples, inducing material and resolution loss when working on natural archives (either stalagmite or sediments). High-resolution solid phase fluorescence (SPF) was developed on speleothems. This method allows now to analyse organic matter quality and quantity if procedure to constrain the optical density are adopted. In fact, a calibration method using liquid phase fluorescence (LPF) was developed for speleothem, allowing to quantify organic carbon at high-resolution. We report here an application of such a procedure SPF/LPF measurements on lake sediments. In order to avoid sediment matrix effects on the fluorescence signal, a calibration using LPF measurements was realised. First results using this method provided organic matter quality record of different organic matter compounds (humic-like, protein-like and chlorophylle-like compounds) at high resolution for the sediment core. High resolution organic matter fluxes are obtained in a second time, applying pragmatic chemometrics model (non linear models, partial least square models) on high resolution fluorescence data. SPF method can be considered as a promising tool for high

Geochemical and Geophysical Analysis of Holocene-aged Sediments from Southeastern Tulare Lake, CA

NASA Astrophysics Data System (ADS)

Prosser, L.; Jackson, B.; Roza, J.

2015-12-01

Tulare Lake is located in the San Joaquin Valley of California west of the Sierra Nevada mountains (Preston, 1981). The Poso Canal trench locality is located in the southeastern portion of Tulare Lake in the Ton Tachi lake plane south of the Atwell Island sand spit. This area was chosen because these sediments lie beneath a road bed that predates agricultural tilling, preserving late-Holocene lake sediments. Sediments from trench TL13-7C were sampled for geophysical and geochemical analyses in order to create a higher resolution lake-level history during the late-Holocene than had been possible using only lithologic descriptions. The new record is comprised of grain size, clay percentage, carbon/nitrogen (C/N) ratios, total inorganic carbon (TIC), total organic carbon (TOC), and nitrogen (N) analyses taken at 2-cm intervals over 181-cm of section comprising four lithologic units. From oldest to youngest, Unit 1A consists of relatively equal and steady percentages of clay, silt, and sand, and relatively low C/N ratios, TIC, TOC, and N, suggesting an unproductive lake and relatively deep lake levels at this high elevation site. Fluctuating C/N ratios, a steady decrease in clay percentage, and a steady increase in sand percentage in Unit 1B suggests periods of flooding and fluctuating lake levels and eventually shallow evaporative lake conditions, as evidenced by a considerable and sudden increase in TIC (to 4.51%) in Unit 2. In addition to the drastic change in TIC, Unit 2 shows evidence of a large influx of terrestrial organic matter perhaps transported by floods by an increase in sand percentage and two pronounced spikes in C/N ratios to 38 and 65 (Meyers and Lallier-Verges, 1999). Unit 3 shows low but steady levels of clay and sand percentages, and higher but steady levels of silt. Levels of TIC, TOC, C/N, and N are all steady, with relatively higher levels of TOC and N, which are indicators of high lake level and productivity (Cohen, 2003). Unit 4 is very similar

Investigation of sedimentation rates and sediment dynamics in Danube Delta lake system (Romania) by 210Pb dating method.

PubMed

Begy, R-Cs; Simon, H; Kelemen, Sz; Preoteasa, L

2018-06-14

Being a dynamic environment associated with complex costal, fluvial and marine processes, only a few studies regarding the evolution of the Danube Delta and the human impacts on its ecosystem have been carried out. Being a sensible to all processes occurring in its catchment area, information is stored in the deposited sediments, which can be used as tracers for natural and anthropogenic processes. The aim of this study is to determine a detailed reconstruction of the sedimentation rates in the last century by applying the 210 Pb dating method validated by 137 Cs profiles. Additionally, the impacts of the construction of river-regulating structures (mainly the Iron Gates Hydro-Energetic Power Plants) are investigated, along with the assessment of natural phenomena (floods, storms etc.). To achieve this, 26 sediment cores from seven lakes were collected. 210 Pb sup and 137 Cs were determined using gamma spectrometry, while 210 Pb tot was measured via alpha spectrometry ( 210 Po), using the CRS model for age determination. From the assessed lakes, the most affected was the Matița Lake with a maximum sedimentation rate of 10.93 g cm -2 yr -1 and the least affected was the Isac Lake. Average sedimentation rates are: 0.95 g cm -2 yr -1 for Cruhlig Lake, 0.70 g cm -2 yr -1 for Uzlina Lake, 0.44 g cm -2 yr -1 for Isac Lake, 0.47 g cm -2 yr -1 for Cuibida Lake, 0.51 g cm -2 yr -1 for Iacob Lake, 1.00 g cm -2 yr -1 for Matița Lake and 0.76 g cm -2 yr -1 for Merhei Lake. Physical parameters (water content, porosity and bulk density) and LOI (organic matter and inorganic carbon content) were determined for each core to differentiate organic and non-organic sedimentation. Beside the natural influences, it is difficult to track the effects of the Iron Gates and not all analysed lakes were suitable for this task. The 1940-1970 period and the following ten years were compared in means of sedimentation: a decrease in sedimentation can be observed

The origin and distribution of subbottom sediments in southern Lake Champlain.

USGS Publications Warehouse

Freeman-Lynde, R. P.; Hutchinson, D.R.; Folger, D.W.; Wiley, B.H.; Hewett, M.J.

1980-01-01

3 units, correlatable with recent Lake Champlain, late-glacial marine Champlain Sea, and proglacial Lake Vermont sediments, have been identified from seismic reflection profiles and 8 piston cores. Lake Vermont deposits are nonfossiliferous and range from thin to absent nearshore and on bedrock highs to more than 126 m thick near Split Rock Point. Champlain Sea sediments contain marine foraminifers and ostracodes and are fairly uniform in thickness (20-30 m). Recent Lake Champlain sediments range in thickness from 0 to 25 m. Average sedimentation rates for Lake Vermont are considerably higher (4-8 cm/yr) than those for the Champlain Sea (0.8-1.2 cm/yr) and Lake Champlain (0.14-0.15 cm/yr). Bedrock, till, and deltaic and alluvial deposits were also identified.- from Authors

Lake Sediment Particle Size Analysis for Holocene Paleoenvironmental Study of Steens Mountain, Eastern Oregon

NASA Astrophysics Data System (ADS)

Morris, J.; Stoner, J. S.; Reilly, B. T.; Hatfield, R. G.; Konyndyk, D.; Abbott, M. B.; Finkenbinder, M. S.; Hillman, A. L.

2016-12-01

In order to better understand climate trends in the late Pleistocene and Holocene in southeast Oregon, we present a sedimentological analysis of Fish Lake, Harney County, Oregon. Fish Lake (42° 44' 15" N, 118° 38' 57" W, 2,246.7 m) sits on the west slope of Steens Mountain, a fault-block mountain of Miocene basalt, adjacent to a glacial moraine. The present environment is high desert with sub alpine steppe vegetation, receiving approximately 12" of precipitation annually. The lake was cored in August 2013 with a series of overlapping drives, correlated by six distinct tephra and magnetic susceptibility. The composite section provides a 7.5 m continuous record of at least the last 13 ka, constrained by an age model built with 13 terrestrial macrofossil 14C dates. The recovered sediments, consisting of fine terrigenous and biogenous material in varying proportions, were analyzed with computed tomography (CT) scans, x-ray fluorescence (XRF) scans, magnetic measurements, loss on ignition (LOI), and sediment grain-size. CT and LOI data reveal a low density, high organic interval in the early Holocene ( 8.5-11 ka) with relatively coarse and well-sorted grain-size, suggesting an extended period of low lake level and low precipitation. Sediment grain-sizes are variable through the middle and late Holocene with high amplitude longer period features from 3 ka to the present. We investigate these grain-size fluctuations in the context of regional Holocene records.

Holocene evolution of the Tonle Sap Lake: valley network infill and rates of sedimentation in Cambodia's Great Lake

NASA Astrophysics Data System (ADS)

Best, J.; Darby, S. E.; Langdon, P. G.; Hackney, C. R.; Leyland, J.; Parsons, D. R.; Aalto, R. E.; Marti, M.

2017-12-01

Tonle Sap Lake, the largest freshwater lake in SE Asia (c. 120km long and 35 km wide), is a vital ecosystem that provides 40-60% of the protein for the population of Cambodia. The lake is fed by flow from the Mekong River that causes the lake rise in level by c. 8m during monsoonal and cyclone-related floods, with drainage of the lake following the monsoon. Hydropower dam construction on the Mekong River has raised concerns as to the fragility of the Tonle Sap habitat due to any changing water levels and sedimentation rates within the lake. This paper details results of sub-bottom profiling surveys of Tonle Sap Lake in October 2014 that detailed the stratigraphy of the lake and assessed rates of infill. An Innomar Parametric Echo Sounder (PES) was used to obtain c. 250 km of sub-bottom profiles, with penetration up to 15m below the lake bed at a vertical resolution of c. 0.20m. These PES profiles were linked to cores from the north of the lake and previous literature. The PES profiles reveal a network of valleys, likely LGM, with relief up to c. 15-20m, that have been infilled by a suite of Holocene sediments. The valley surface is picked out as a strong reflector throughout the lake, and displays a series of valleys that are up to c. 15m deep and commonly 50-200m wide, although some of the largest valleys are 1.2km in width. Modelling of channel network incision during LGM conditions generates landscapes consistent with our field observations. The Tonle Sap valley network is infilled by sediments that show firstly fluvial and/or subaerial slope sedimentation, and then by extensive, parallel-bedded, lacustrine sedimentation. Lastly, the top c. 1m of sedimentation is marked by a distinct basal erosional surface that can be traced over much of the Tonle Sap Lake, and that is overlain by a series of parallel PES reflections. This upper sediment layer is interpreted to represent sedimentation in the Tonle Sap lake due to sediment suspension settling but after a period

Conditions affecting the release of phosphorus from surface lake sediments.

PubMed

Christophoridis, Christophoros; Fytianos, Konstantinos

2006-01-01

Laboratory studies were conducted to determine the effect of pH and redox conditions, as well as the effect of Fe, Mn, Ca, Al, and organic matter, on the release of ortho-phosphates in lake sediments taken from Lakes Koronia and Volvi (Northern Greece). Results were evaluated in combination with experiments to determine P fractionation in the sediment. The study revealed the major effect of redox potential and pH on the release of P from lake sediments. Both lakes showed increased release rates under reductive conditions and high pH values. The fractionation experiments revealed increased mobility of the reductive P fraction as well as of the NaOH-P fraction, indicating participation of both fractions in the overall release of sediment-bound P, depending on the prevailing environmental conditions. The results were assessed in combination with the release patterns of Fe, Mn, Ca, Al, and organic matter, enabling the identification of more specific processes of P release for each lake. The basic release patterns included the redox induced reductive dissolution of P-bearing metal oxides and the competitive exchange of phosphate anions with OH- at high pH values. The formation of an oxidized surface microlayer under oxic conditions acted as a protective film, preventing further P release from the sediments of Lake Volvi, while sediments from Lake Koronia exhibited a continuous and increased tendency to release P under various physicochemical conditions, acting as a constant source of internal P loading.

Processes of seasonal layer formation in varved Lake Czechowskie (N Poland): Linking monitoring and sediment core data

NASA Astrophysics Data System (ADS)

Ott, Florian; Brykała, Dariusz; Gierszewski, Piotr; Schwab, Markus; Brademann, Brian; Dräger, Nadine; Kienel, Ulrike; Pinkerneil, Sylvia; Plessen, Birgit; Słowiński, Michał; Błaszkiewicz, Mirosław; Brauer, Achim

2017-04-01

The interpretation of environmental and climate records, such as lake sediments, rely on the profound understanding of the proxy sensitivity towards past changes. Monitoring of lake sedimentation, limnological, hydrological and climate parameters are natural experiments combining measurements and observations. In this study, we present monitoring data from Lake Czechowskie (N Poland) for the period 2013-2016. Lake Czechowskie has a surface area of 73 ha and a maximum water depth of 32 m. Sediment has been trapped in a 4-cylinder and an automatic sequential trap installed at 12 and 30 m water depths close to the deepest part of the lake, respectively. Sampling intervals range from 15 (sequential) to 30 days (4 cylinder) days. The sediment has been analyzed for total sediment flux, calcium carbonate and organic matter contents. Continuous water temperature measurements (30 min. intervals) are based on 17 data loggers covering the entire water column (1 m steps from 0-12 m; 5 m steps from 12-32 m). Limnological measurements (e.g. electrical conductivity, dissolved oxygen and pH) have been carried out manually on a monthly routine. Air temperature, precipitation, wind speed and direction are available for the same period from a meteorological station installed at the shore of Lake Czechowskie. Our dataset exhibit seasonal deposition starting with diatom blooms and calcite precipitation in spring after lake stratification. A second deposition peak occurs at the onset of lake mixing in late autumn and winter. This is caused by an initial deposition of planktonic diatoms (mainly Fragilaria spp.) indicating lake productivity, followed by an increase in larger calcite patches (>30 µm) and periphyitic diatoms (mainly Navicula spp.) representing resuspension of littoral sediments. We paired sediment trap data with micro-facies analyses from a sediment core obtained in autumn 2016 covering the same time interval. This study is a contribution to the Virtual Institute of

Estimation of Sediment Sources Using Selected Chemical Tracers in the Perry Lake and Lake Wabaunsee Basins, Northeast Kansas

USGS Publications Warehouse

Juracek, Kyle E.; Ziegler, Andrew C.

2007-01-01

In Kansas and nationally, stream and lake sediment is a primary concern as related to several important issues including water quality and reservoir water-storage capacity. The ability to achieve meaningful decreases in sediment loads to reservoirs requires a determination of the relative importance of sediment sources within the contributing basins. To investigate sources of sediment within the Perry Lake and Lake Wabaunsee Basins of northeast Kansas, representative samples of channel-bank sources, surface-soil sources (cropland and grassland), and reservoir bottom sediment were collected, analyzed, and compared. Subbasins sampled within the Perry Lake Basin included Atchison County Lake, Banner Creek Reservoir, Gregg Creek, Mission Lake, and Walnut Creek. The samples were sieved to isolate the less than 63-micron fraction (that is, the silt and clay) and analyzed for selected nutrients (total nitrogen and total phosphorus), organic and total carbon, 25 trace elements, and the radionuclide cesium-137 (137Cs). To determine which of the 30 constituents provided the best ability to discriminate between channel-bank and surface-soil sources in the two basins, four selection criteria were used. To be selected, it was required that the candidate constituent (1) was detectable, (2) had concentrations or activities that varied substantially and consistently between the sources, (3) had concentration or activity ranges that did not overlap between the sources, and (4) had concentration or activity differences between the sources that were statistically significant. On the basis of the four selection criteria, total nitrogen (TN), total phosphorus (TP), total organic carbon (TOC), and 137Cs were selected. Of the four selected constituents, 137Cs likely is the most reliable indicator of sediment source because it is known to be conservative in the environment. Trace elements were not selected because concentrations in the channel-bank and surface-soil sources generally were

Chemical data for bottom sediment, lake water, bottom-sediment pore water, and fish in Mountain Creek Lake, Dallas, Texas, 1994-96

USGS Publications Warehouse

Jones, S.A.; Van Metre, P.C.; Moring, J.B.; Braun, C.L.; Wilson, J.T.; Mahler, B.J.

1997-01-01

Mountain Creek Lake is a reservoir adjacent to two U.S. Department of the Navy facilities, the Naval Weapons Industrial Reserve Plant and the Naval Air Station in Dallas, Texas. A Resource Conservation and Recovery Act Facility Investigation found ground-water plumes containing chlorinated solvents on both facilities. These findings led to a U.S. Geological Survey study of Mountain Creek Lake adjacent to both facilities between June 1994 and August 1996. Bottom sediments, lake water, bottom-sediment pore water, and fish were collected for chemical analysis.

Color reflectance spectroscopy of profundal lake sediments: a novel moisture-balance proxy for tropical East Africa

NASA Astrophysics Data System (ADS)

Meyer, Inka; Van Daele, Maarten; Fiers, Geraldine; Verleyen, Eli; De Batist, Marc; Verschuren, Dirk

2016-04-01

Investigations of the continuous sediment record from Lake Challa, a deep freshwater crater lake on the eastern slope of Mt. Kilimanjaro, are expanding our knowledge about past climate and environmental changes in equatorial East Africa. During a field campaign in 2005 a 20.65-m long composite sediment sequence was retrieved from the center of the lake, covering the past 25,000 years. Unlike many other East African lakes, Lake Challa never dried out during this period and therefore provides one of the few continuous and high-resolution regional climate-proxy records since before the LGM. Continuously taken digital line-scan images (GeoTek MSCL core logger) revealed systematic colour variation from greenish to yellow-brownish sediments throughout the core sequence. To characterize the origin of these colour variations, high-resolution colour reflectance spectrometry was carried out. The relative absorption band depth (RABD) at different wavelengths was calculated to distinguish between sediment components with distinct absorption/ reflection characteristics. RABD660/670 can be used as a proxy for chlorophyll and its derivates, and RABD610 as a proxy for carotenoids and their derivates. Comparison of RABD660/670 with independent reconstructions of rainfall (the Branched and Isoprenoid Tetraether (BIT) index of bacterial lipids) and seismic lake level reconstructions showed a positive correlation between these proxies. During times of wetter climate and higher lake level, e.g. the early Holocene, the RABD660/670 value is higher than during times of inferred dry conditions and low lake level, e.g. the early late-Glacial period (during which no chlorophyll or its derivates were detected). We attribute this positive correlation to reduced preservation of chlorophyll contained in the settling remains of dead phytoplankton during lowstands, when bottom waters may have been better oxygenated. This data is supported by the variation in fossil pigment concentration and

Sedimentation rates in the marshes of Sand Lake National Wildlife Refuge

USGS Publications Warehouse

Gleason, R.A.; Euliss, N.H.; Holmes, C.W.

2003-01-01

Impoundments located within river systems in the Northern Great Plains are vulnerable to sediment inputs because intensive agriculture in watersheds has increased soil erosion and sediments in rivers. At the request of the U.S. Fish and Wildlife Service (FWS), we evaluated the vertical accretion of sediment in the Mud Lake impoundment of Sand Lake National Wildlife Refuge (NWR), Brown County, South Dakota. The Mud Lake impoundment was created in 1936 by constructing a low-head dam across the James River. We collected sediment cores from the Mud Lake impoundment during August 2000 for determination of vertical accretion rates. Accretion rates were estimated using cesium-13 7 and lead-210 isotopic dating techniques to estimate sediment accretion over the past 100 years. Accretion rates were greatest near the dam (1.3 cm yr-1) with less accretion (0.2 cm yr-1) occurring in the upper reaches of Mud Lake. As expected, accretion was highest near the dam where water velocities and greater water depth facilitates sediment deposition. Higher rates of sedimentation (accretion> 2.0 cm year-1) occurred during the 1990s when river flows were especially high. Since 1959, sediment accretion has reduced maximum pool depth of Mud Lake near the dam by 55 cm. Assuming that sediment accretion rates remain the same in the future, we project Mud Lake will have a maximum pool depth of 77 and 51 cm by 2020 and 2040, respectively. Over this same time frame, water depths in the upper reaches of Mud Lake would be reduced to< 2 cm. Projected future loss of water depth will severely limit the ability of managers to manipulate pool levels in Mud Lake to cycle vegetation and create interspersion of cover and water to meet current wildlife habitat management objectives. As predicted for major dams constructed on rivers throughout the world, Mud Lake will have a finite life span. Our data suggests that the functional life span of Mud Lake since construction will be < 100 years. We anticipate that

MERCURY IN SEDIMENT AND FISH FROM NORTH MISSISSIPPI LAKES.

EPA Science Inventory

Sediments and/or fish were collected from Sardis, Enid and Grenada Lakes, which are located in three different watersheds in North Mississippi, in order to assess mercury contamination. The mean total mercury concentration in sediments from Enid Lake in 1997 was 0.154 mg Hg/kg, w...

Mid-Late Holocene Asian monsoon variations recorded in the Lake Rara sediment, western Nepal

NASA Astrophysics Data System (ADS)

Nakamura, A.; Yokoyama, Y.; Maemoku, H.; Yagi, H.; Okamura, M.; Matsuoka, H.; Miyake, N.; Adhikari, D.; Dangol, V.; Miyairi, Y.; Obrochta, S.; Matsuzaki, H.; Ikehara, M.

2011-12-01

The Asian monsoon is an important component of the Earth's climate system to understand regional and global climate dynamics. While geological reconstructions indicate that the Asian summer monsoon intensity gradually decreased through the Holocene, a clear and coherent picture of millennial and centennial scale variability has yet to emerge (e.g., Overpeck and Cole, 2007). The Himalayas are a key location for understanding centennial to millennial scale variations in the Asian monsoon, yet few studies of the Holocene have been conducted in this sensitive area. Direct evidence for shifts in monsoonal wind strength is often limited to marine proxy records, while terrestrial reconstructions (e.g., lake levels and spleothems) focus on precipitation. Here, we present the first evidence of terrestrial summer monsoon wind strength changes from Lake Rara, western Nepal. The lake is located at 3,000m above sea level and has a maximum water depth of 168m. Lake Rara Mn/Ti data, a proxy for lake stratification, provide the first direct comparison of the Indian summer monsoon wind intensity between the terrestrial Himalayan region and the marine Arabian sea region (Gupta et al., 2003) during mid-late Holocene. Centennial to millennial scale variability found in those records are synchronous, with the weak wind intervals corresponding to drier periods of East Asian. Strong similarities between the Lake Rara monsoon record and the Dongge cave speleothems precipitation record (Wang et al., 2005) suggest that the influence of Indian summer monsoon penetrates into southeastern China, which should be taken into account when interpreting paleomonsoon reconstructions. Overpeck JT, Cole JE. 2007. Climate change - Lessons from a distant monsoon. Nature 445: 270-271. Gupta AK, Anderson DM, Overpeck JT. 2003. Abrupt changes in the Asian southwest monsoon during the Holocene and their links to the North Atlantic Ocean. Nature 421: 354-357. Wang YJ, Cheng H, Edwards RL, He YQ, Kong XG, An

Late Quaternary lake-level changes constrained by radiocarbon and stable isotope studies on sediment cores from Lake Titicaca, South America

NASA Astrophysics Data System (ADS)

Rowe, Harold D.; Guilderson, Thomas P.; Dunbar, Robert B.; Southon, John R.; Seltzer, Geoffrey O.; Mucciarone, David A.; Fritz, Sherilyn C.; Baker, Paul A.

2003-09-01

developed for the Lake Titicaca sequence using different organic fractions, mobile organic sub-fractions and fractions containing mobile sub-fractions should generally be avoided in geochronology studies. Consequently, we believe humin and/or bulk decalcified ages provide the most consistent chronologies for the post-13,500 yr BP interval, and humin ages provide the most representative ages for sedimentation prior to 13,500 yr BP interval. Using the age model derived from the deep water core site and a previously published isotope-based lake-level reconstruction, we present a qualitative record of lake level in the context of several ice-core records from the western hemisphere. We find the latest Pleistocene lake-level response to changing insolation began during or just prior to the Bølling/Allerød period. Using the isotope-based lake-level reconstruction, we also find the 85-m drop in lake level that occurred during the mid-Holocene was synchronous with an increase in the variability of ice-core δ18O from a nearby icecap, but was not reflected in any of the polar ice-core records recovered from the interior of Antarctica and Greenland.

Lake Qinghai sediment geochemistry linked to hydroclimate variability since the last glacial

NASA Astrophysics Data System (ADS)

Jin, Zhangdong; An, Zhisheng; Yu, Jimin; Li, Fuchun; Zhang, Fei

2015-08-01

Geochemistry of basin sediments from semi-arid regions is valuable to understand past hydroclimatic changes. Here, we investigate the links of sedimentary geochemistry (Rb, Sr, Ca/Zr, TOC, and %CaCO3), carbonate mineralogy and ostracod shell δ18O of Lake Qinghai, a basin proximal to major dust production centers at mid-latitudes of the Northern Hemisphere, to changes in depositional conditions and hydroclimate during the past 32 ka. Surface lacustrine sediments are characterized by low-Rb, high-Sr, low-Rb/Sr, high-%CaCO3 and high-Ca/Zr values, in contrast to the chemical compositions of eolian loess (high-Rb, low-Sr, high-Rb/Sr, low-%CaCO3, and low-Ca/Zr). A direct comparison of soluble Ca and Sr in two short cores with instrumental water discharge data suggests that lacustrine precipitates in Lake Qinghai are dominated by authigenic aragonite formed under Ca2+-limited water conditions, and that the accumulation rate of aragonite dominantly depends on solute fluxes into the lake during the rainy seasons (late May to September). Our high-resolution down-core records show that sediments during the last glacial (∼32-19.8 ka) had high-Rb, low-Sr, low-%CaCO3, and low-Ca/Zr, indicating eolian dust (loess) accumulation in a desiccated basin under dry glacial conditions, further supported by grain size and pollen results. This type of sedimentation was maintained during the last deglacial (∼19.8-11.5 ka), but interrupted by episodic lacustrine precipitates with high-Sr, high-%CaCO3, high-Ca/Zr, and low-Rb. At ∼11.5 ka, sedimentary Rb/Sr, Ca/Zr, %CaCO3 and TOC show dramatic and permanent changes, implying an abrupt shift in the atmospheric circulation at the onset of the Holocene in the Lake Qinghai region. Lacustrine precipitates have persisted throughout the Holocene with a maximum during the early to mid-Holocene (∼10.5-8.0 ka). Since ∼8.0 ka, the gradual and significant decreases in aragonite and Sr accumulations in tandem with increasing dust deposit and

The carbon cycle and biogeochemical dynamics in lake sediments

USGS Publications Warehouse

Dean, W.E.

1999-01-01

The concentrations of organic carbon (OC) and CaCO3 in lake sediments are often inversely related. This relation occurs in surface sediments from different locations in the same lake, surface sediments from different lakes, and with depth in Holocene sediments. Where data on accumulation rates are available, the relation holds for organic carbon and CaCO3 accumulation rates as well. An increase of several percent OC is accompanied by a decrease of several tens of percent CaCO3 indicating that the inverse relation is not due to simple dilution of one component by another. It appears from core data that once the OC concentration in the sediments becomes greater than about 12%, the CO2 produced by decomposition of that OC and production of organic acids lowers the pH of anoxic pore waters enough to dissolve any CaCO3 that reaches the sediment-water interface. In a lake with a seasonally anoxic hypolimnion, processes in the water column also can produce an inverse relation between OC and CaCO3 over time. If productivity of the lake increases, the rain rate of OC from the epilimnion increases. Biogenic removal of CO2 and accompanying increase in pH also may increase the production of CaCO3. However, the decomposition of organic matter in the hypolimnion will decrease the pH of the hypolimnion causing greater dissolution of CaCO3 and therefore a decrease in the rain rate of CaCO3 to the sediment-water interface.

German-Russian project PLOT: new postglacial-glacial-preglacial pollen records from the Lakes Ladoga and Bol'shoe Shuch'e

NASA Astrophysics Data System (ADS)

Andreev, A.; Savelieva, L.; Shumilovskikh, L.; Gromig, R.; Wennrich, V.; Fedorov, G.; Wagner, B.; Melles, M.

2017-12-01

The German-Russian project PLOT (PaleolimnoLOgical Transect) investigates the Late Quaternary environmental history along the Northern Eurasia transect. Within the scope of a pilot phase of the project we have investigated Lake Ladoga, the largest lake in Europe. Although the postglacial history of the lake was studied over the last decades, the preglacial history remained unknown. It is assumed that during the Last Interglacial Lake Ladoga was part of a precursor of the Baltic Sea, which had a connection via Ladoga and Onega Lakes to the White Sea. Sediment coring at two sites in western Ladoga Lake in September 2013 has revealed sediment succession subdivided into 5 main lithological units. The sediments studied in a 22.7 m lake core were also palynologically investigated. Pollen assemblages indicate that the lowermost sediments with pollen of Betula, Alnus, Pinus, Carpinus, Quercus, Corylus, Ulmus, Tilia, remains of fresh-water Pediastrum and Botryococcus colonies as well as cysts of marine dinoflagellates and brackish water acritarchs) were accumulated during an interglacial with climate more favorable than in the Holocene. The OSL-dated samples show the late Eemian and post Eemian ages. Lake Bol'shoe Shuch'e (Polar Urals) was cored in April 2016. The thickness of the lacustrine sediments was 54 m. According to the previous studies, most of the study area has remained ice-free over the last 50-60 ka. However, the configuration and timing of the preceding glaciations has remained unclear, because of lack continuous, long-term paleoenvironmental records in the area. Preliminary studies show that the uppermost 9 m of the sediments were accumulated during the Holocene, between 11 and 9 m - in Younger Dryas, between 11 and 9 m - in Allerod, between 11 and 25 m - in MIS 2, between 25 and 54 m - in the MIS 3. We expect that the core will provide the most continuous sediment records from the whole region which can be used to reconstruct the environmental changes.

Mountain Lake, Presidio National Park, San Francisco: Paleoenvironment, heavy metal contamination, sedimentary record rescue, remediation, and public outreach

NASA Astrophysics Data System (ADS)

Myrbo, A.; Rodysill, J. R.; Jones, K.; Reidy, L. M.

2014-12-01

Sediment cores from Mountain Lake, a small natural lake in Presidio National Park, San Francisco, CA, provide a record of Bay Area environmental change spanning the past 2000 years, and of unusually high heavy metal contamination in the last century (Reidy 2001). In 2013, partial dredging of the lake removed the upper two meters of lake sediment as part of a remediation effort. Prior to dredging, long and short cores spatially covering the lake and representing deep and shallow environments were recovered from the lake to preserve the paleoenvironmental record of one of the only natural lakes on the San Francisco Peninsula. The cores are curated at LacCore and are available for research by the scientific community. Mountain Lake formed in an interdunal depression and was shallow and fluctuating in its first few hundred years. Lake level rise and inundation of a larger area was followed by lowstands under drier conditions around 550-700 and 1300 CE. Nonnative taxa and cultivars appeared at the time of Spanish settlement in the late 18th century, and the lake underwent eutrophication due to livestock pasturing. U.S. Army landscaping introduced trees to the watershed in the late 19th century. The upper ~1m of sediments document unusually high heavy metal contamination, especially for lead and zinc, caused by the construction and heavy use of Highway 1 on the lake shore. Lead levels peak in 1975 and decline towards the surface, reflecting the history of leaded gasoline use in California. Zinc is derived mainly from automobile tires, and follows a pattern similar to that of lead, but continues to increase towards the surface. Ongoing research includes additional radiocarbon dating and detailed lithological analysis to form the basis of lake-level reconstruction and archeological investigations. Because the Presidio archaeological record does not record human habitation in the area until approximately 1300 years before present, the core analysis also has the potential to

Human land uses enhance sediment denitrification and N2O production in Yangtze lakes primarily by influencing lake water quality

NASA Astrophysics Data System (ADS)

Liu, W.; Yao, L.; Wang, Z.; Xiong, Z.; Liu, G.

2015-10-01

Sediment denitrification in lakes alleviates the effects of eutrophication through the removal of nitrogen to the atmosphere as N2O and N2. However, N2O contributes notably to the greenhouse effect and global warming. Human land uses (e.g. agricultural and urban areas) strongly affect lake water quality and sediment characteristics, which, in turn, may regulate lake sediment denitrification and N2O production. In this study, we investigated sediment denitrification and N2O production and their relationships to within-lake variables and watershed land uses in 20 lakes from the Yangtze River basin in China. The results indicated that both lake water quality and sediment characteristics were significantly influenced by watershed land uses. N2O production rates increased with increasing background denitrification rates. Background denitrification and N2O production rates were positively related to water nitrogen concentrations but were not significantly correlated with sediment characteristics and plant community structure. A significant positive relationship was observed between background denitrification rate and percentage of human-dominated land uses (HDL) in watersheds. Structural equation modelling revealed that the indirect effects of HDL on sediment denitrification and N2O production in Yangtze lakes were mediated primarily through lake water quality. Our findings also suggest that although sediments in Yangtze lakes can remove large quantities of nitrogen through denitrification, they may also be an important source of N2O, especially in lakes with high nitrogen content.

The Long Pleistocene Paleoclimate Record from Stoneman Lake, Arizona: an Update

NASA Astrophysics Data System (ADS)

Werne, J. P.; Anderson, R. S.; Fawcett, P. J.; Brown, E. T.; Jimenez-Moreno, G.; Toney, J. L.; Dunbar, N. W.; Stockhecke, M.; Garrett, H.; Garcia, D.

2016-12-01

Long continuous lake sediment core records of Pleistocene paleoenvironmental and paleoclimatic change are rare in the American Southwest. Such records have the potential to provide long-term perspective on, for instance, the occurrence and duration of past megadroughts, vegetation change during glacial-interglacial transitions, and changes in precipitation sources, among many other aspects of environmental change. One site with the potential to study ancient megadroughts and long-term environmental change is Stoneman Lake, central Arizona, whose basin is a circular depression formed by a collapse in late Tertiary volcanics. The lake is presently spring fed, and has alternated between a marsh and a lake over the last 25 years, fluctuating by > 3 meters. This sensitivity is due to its small closed drainage basin (ca. 2.5 km2) with one small intermittant inflowing stream. We have been analyzing two parallel lacustrine sediment cores (70 m and 30 m deep), which were recovered in October of 2014. Our preliminary chronology is based on 8 AMS dates in the upper 7 m and two distinct tephras at 30.8 m and 36.3 m depth. The Holocene-Pleistocene boundary occurs at 2.8 m ( 11,000 cal yr B.P.) while the lowest finite AMS age at 4.2 m is 45,500 cal yr B.P. The most likely source of the tephra at 30.8 m is from Sugarloaf, San Francisco Volcanic Field, having a preliminary age of 700k. Based on this age, we estimate that the 70-m deep hole will provide a climate record back to 1.3 million years ago. Of particular interest are the interglacials that serve as good analogs for future climate including MIS 11 and MIS 19. In addition to our Geo-Tek analyses (MS, bulk density and high-resolution images) pollen data outlines glacial-interglacial changes since the mid-Pleistocene. Carbon isotopes from glacial-age sediments are more negative, suggesting a dominance of C3 plants, while less negative values during interglacials suggest a greater C4 component. ITRAX Scanning XRF and

The recent climatic change of subarctic zone recorded in lake sediments in Hokkaido, Japan

NASA Astrophysics Data System (ADS)

Seto, K.; Takata, H.; Saito, M.; Katsuki, K.; Sonoda, T.; Kawajiri, T.; Watanabe, T.

2010-12-01

In the coastal area of the Sea of Okhotsk in the east part of Hokkaido located to for subarctic zone, many brackish-water lakes are distributed. Especially, the Okhotsk brackish-water lake group around Abashiri City is constituted by major lake in Japan such as Lake Abashiri, Lake Mokoto, Lake Tofutsu, and Lake Notoro. The each lake shows a different present environment and history. Therefore, the change that is common in those lakes seems to be the change concerning the climate. In this study, recent environment change in Abashiri region (after the Little Ice Age) is discussed by sedimentologic and geochemical high-resolution analysis of the cores collected from the Okhotsk brackish-water lake group. The cores collected from four lake shows the length of 1 to 3m. In Lake Mokoto, there was the Ta-a tephra (AD 1739) at the 350cm depth. The Ta-a tephra are found at the horizon of 250 cm in Lake Abashiri, of 78 cm in Lake Notoro, and of 44 cm in Lake Tofutsu. The differences of the sedimentation rate of that lake are caused by the size of lake and catchment area. In Lake Mokoto, the catchment area is most large, and the size of lake is smallest among the four lake of Abashiri City. The cores collected from Lake Abashiri and Lake Mokoto consist of organic mud with the lamination in all cores. The core top 56 cm shows the black (N1.5/0, L value: < 5), and it seems to indicate the euxinic environment as present. The organic mud of 56-77cm-depth show black (2.5GY2/1, L values = ca 20), and it is considered that it shows the freshwater environment. In history of Lake Abashiri, the lake water changes to brackish-water from freshwater in 1930’s. It is considered that the change of the lightness in 56 cm depth is correspondent to this timing. In the observation by the soft X-ray photograph, the pattern of the lamination of Lake Abashiri is similar to the Lake Mokoto. The cyclic lamination set is observed in the core from Lake Mokoto. It is considered that this cyclic

Using Inclination and Declination Data from South African Lake Sediment Records to Evaluate Radiocarbon-based Chronologies of the Past Millennium

NASA Astrophysics Data System (ADS)

Haberzettl, T.; Wündsch, M.; Kasper, T.; Meadows, M. E.; Stoner, J. S.; Su, Y.; Mäusbacher, R.

2016-12-01

Paleomagnetic data obtained from sedimentary archives are extremely scarce in South Africa. Attempts to extract such data from marine sediment cores on the South African shelf failed. This was very likely due to the high carbonate content in these sediments resulting in very low NRMs and hence a bad preservation of the directional data. Although NRMs are still very low it was possible to extract directional data from lacustrine sediments of coastal lakes on the Western Cape. Unfortunately, the radiocarbon-based chronologies for the sediments from these systems suffer from variable reservoir effects over time. In order to assess the quality of the established age-depth relations we compared inclination and declination data covering the past millennium from the two neighbouring lakes Eilandvlei and Swartvlei (Garden Route National Park, Wilderness Coastal Section) to predictions of the gufm1 magnetic field model derived from historical records (Jackson et al., 2000), the CALS3k.4 model (Korte and Constable, 2011) as well as archaeomagnetic data from the Limpopo region (Neukirch et al., 2012; Tarduno et al., 2015). Despite the large distance between the compared records (up to 1500 km) a very good agreement of the Eilandvlei data with the compared data was observed, which confirms the radiocarbon-based chronology from this site. However, a distinct underestimation of the reservoir effect at Swartvlei revealed by the paleomagnetic data lead to a re-evaluation of the chronology resulting in a temporal coverage of this record of only 400 years. Data from Eilandvlei show that inclination values vary around the ones expected, based on a geocentric axial dipole model (GAD) for the site latitude for the time interval 1000-400 cal BP. A distinct shift to steeper inclinations can be observed thereafter. This might reflect that the impact of the South Atlantic Anomaly at this location became more pronounced after 400 cal BP. Reference: Jackson, A. et al. 2000. Philosophical

Rates, timing, and cyclicity of Holocene eolian activity in north-central United States: Evidence from varved lake sediments

USGS Publications Warehouse

Dean, W.E.

1997-01-01

Most of the sediment components that accumulated in Elk Lake, northwestern Minnesota, during the Holocene are autochthonous or biogenic, delivered to the sediment-water interface on a seasonal schedule, preserved in distinct annual laminae (varves). The main allochthonous component is detrital clastic material, as measured by bulk-sediment concentrations of aluminum, sodium, potassium, titanium, and quartz, that enters the lake mostly as eolian dust. The eolian clastic influx to Elk Lake was considerably greater during the mid-Holocene (8-4 ka) than it has been for the past 4000 yr, when periods of increased eolian activity correspond to the time of the Little Ice Age and the dust bowl. Geochemical records of eolian activity exhibit distinct cyclicities with dominant periodicities of 400 and 84 yr.

Role of storms and forest practices in sedimentation of an Oregon Coast Range lake

NASA Astrophysics Data System (ADS)

Richardson, K.; Hatten, J. A.; Wheatcroft, R. A.; Guerrero, F. J.

2014-12-01

The design of better management practices in forested watersheds to face climate change and the associated increase in the frequency of extreme events requires a better understanding of watershed responses to extreme events in the past and also under management regimes. One of the most sensitive watershed processes affected is sediment yield. Lake sediments record events which occur in a watershed and provide an opportunity to examine the interaction of storms and forest management practices in the layers of the stratigraphy. We hypothesize that timber harvesting and road building since the 1900s has resulted in increases in sedimentation; however, the passage of the Oregon Forest Practices Act (OFPA) in 1972 has led to a decrease in sedimentation. Sediment cores were taken at Loon Lake in the Oregon Coast Range. The 32-m deep lake captures sediment from a catchment highly impacted by recent land use and episodic Pacific storms. We can use sedimentological tools to measure changes in sediment production as motivated by extreme floods before settlement, during a major timber harvesting period, and after installation of forestry Best Management Practices. Quantification of changes in particle size and elemental composition (C, N, C/N) throughout the cores can elucidate changes in watershed response to extreme events, as can changes in layer thickness. Age control in the cores is being established by Cesium-137 and radiocarbon dating. Given the instrumental meteorological data and decadal climate reconstructions, we will disentangle climate driven signals from changes in land use practices. The sediment shows distinct laminations and varying thickness of layers throughout the cores. Background deposition is composed of thin layers (<0.5 cm) of fine silts and clays, punctuated by thicker layers (3-25 cm) every 10 to 75 cm. These thick layers consist of distinctly textured units, generally fining upward. We interpret the thick layers in Loon Lake to be deposited by

Environmental legacy of copper metallurgy and Mongol silver smelting recorded in Yunnan Lake sediments.

PubMed

Hillman, Aubrey L; Abbott, Mark B; Yu, JunQing; Bain, Daniel J; Chiou-Peng, TzeHuey

2015-03-17

Geochemical measurements on well-dated sediment cores from Lake Er (Erhai) are used to determine the timing of changes in metal concentrations over 4500 years in Yunnan, a borderland region in southwestern China noted for rich mineral deposits but with inadequately documented metallurgical history. Our findings add new insight into the impacts and environmental legacy of human exploitation of metal resources in Yunnan history. We observe an increase in copper at 1500 BC resulting from atmospheric emissions associated with metallurgy. These data clarify the chronological issues related to links between the onset of Yunnan metallurgy and the advent of bronze technology in adjacent Southeast Asia, subjects that have been debated for nearly half a century. We also observe an increase from 1100 to 1300 AD in a number of heavy metals including lead, silver, zinc, and cadmium from atmospheric emissions associated with silver smelting. Culminating during the rule of the Mongols, known as the Yuan Dynasty (1271-1368 AD), these metal concentrations approach levels three to four times higher than those from industrialized mining activity occurring within the catchment today. Notably, the concentrations of lead approach levels at which harmful effects may be observed in aquatic organisms. The persistence of this lead pollution over time created an environmental legacy that likely contributes to known issues in modern day sediment quality. We demonstrate that historic metallurgical production in Yunnan can cause substantial impacts on the sediment quality of lake systems, similar to other paleolimnological findings around the globe.

Variation laws and release characteristics of phosphorus on surface sediment of Dongting Lake.

PubMed

Zhu, Guangrui; Yang, Ying

2018-05-01

The variation trend and growth rate of P were analyzed by the concentration of the phosphorus fraction on surface sediment of Dongting Lake from 2012 to 2016, to reveal the cumulative effect of P in the actual environment. Meanwhile, the adsorption kinetics and adsorption isotherm were employed to examine the P-release possibility of sediment, which predicts the yearly released sediment phosphorus in Dongting Lake. The actual growth rate of TP (Total Phosphorus) is 53 mg·(kg·year) -1 in East Dongting Lake, 39 mg·(kg·year) -1 in South Dongting Lake, and 29 mg·(kg·year) -1 in West Dongting Lake, while the sum of the phosphorus fraction growth rates has little difference from the rate of TP in sediments of the three areas of Dongting Lake. Furthermore, the Elovich model and the Langmuir crossover-type equations are established to present the adsorption characteristic of sediment in Dongting Lake; the result shows that the sediments play a source role for phosphorus in East and South Dongting Lake from zero equilibrium phosphorus concentration (EPC 0 ) in the present situation, but an adsorption effect on TP is shown in West Dongting Lake. When the conditions of environment change are ignored, the maximum P-sorption level in sediments of East Dongting Lake will reach in 2040 according to the actual growth rate of sediments, while that in West Dongting Lake and South Dongting Lake will be in 2046 and 2061, respectively.

Hyper-spectral imaging: A promising tool for quantitative pigment analysis of varved lake sediments

NASA Astrophysics Data System (ADS)

Butz, Christoph; Grosjean, Martin; Tylmann, Wojciech

2015-04-01

Varved lake sediments are good archives for past environmental and climate conditions from annual to multi-millennial scales. Among other proxies, concentrations of sedimentary photopigments have been used for temperature reconstructions. However, obtaining well calibrated annually resolved records from sediments still remains challenging. Most laboratory methods used to analyse lake sediments require physical subsampling and are destructive in the process. Hence, temporal resolution and number of data are limited by the amount of material available in the core. Furthermore, for very low sediment accumulation rates annual subsampling is often very difficult or even impossible. To address these problems we explore hyper-spectral imaging as a non-destructive method to analyse lake sediments based on their reflectance spectra in the visible and near infrared spectrum. In contrast to other scanning methods like X-ray fluorescence, VIS/NIR reflectance spectrometry distinguishes between biogeochemical substances rather than single elements. Among others Rein (2003) has shown that VIS-RS can be used to detect relative concentrations of sedimentary photopigments (e.g. chlorins, carotenoids) and clay minerals. In this study hyper-spectral imaging is used to infer ecological proxy data from reflectance spectra of varved lake sediments. Hyper-spectral imaging permits the measurement of an entire sediment core in a single run at high spatial (30x30µm/pixel) and spectral resolutions (~2.8nm) within the visual to near infrared spectrum (400-1000nm). This allows the analysis of data time series and spatial mapping of sedimentary substances (e.g. chlorophylls/bacterio-chlorophylls and diagenetic products) at sub-varve scales. The method is demonstrated on two varved lake sediments from northern Poland showing the distributions of relative concentrations of two types of sedimentary pigments (Chlorophyll-a + derivatives and Bacterio-pheophytin-a) within individual varve years. The

Investigating molecular changes in organic matter composition in two Holocene lake-sediment records from central Sweden using pyrolysis-GC/MS

NASA Astrophysics Data System (ADS)

Ninnes, Sofia; Tolu, Julie; Meyer-Jacob, Carsten; Mighall, Tim M.; Bindler, Richard

2017-06-01

Organic matter (OM) is a key component of lake sediments, affecting carbon, nutrient, and trace metal cycling at local and global scales. Yet little is known about long-term (millennial) changes in OM composition due to the inherent chemical complexity arising from multiple OM sources and from secondary transformations. In this study we explore how the molecular composition of OM changes throughout the Holocene in two adjacent boreal lakes in central Sweden and compare molecular-level information with conventional OM variables, including total carbon, total nitrogen, C:N ratios, δ13C, and δ15N. To characterize the molecular OM composition, we employed a new method based on pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), which yields semiquantitative data on >100 organic compounds of different origin and degradation status. We identify large changes in OM composition after deglaciation (circa 8500 ± 500 B.C.), associated with early landscape development, and during the most recent 40-50 years, driven by degradation processes. With molecular-level information we can also distinguish between natural landscape development and human catchment disturbance during the last 1700 years. Our study demonstrates that characterization of the molecular OM composition by the high-throughput Py-GC/MS method is an efficient complement to conventional OM variables for identification and understanding of past OM dynamics in lake-sediment records. Holocene changes observed for pyrolytic compounds and compound classes known for having different reactivity indicate the need for further paleo-reconstruction of the molecular OM composition to better understand both past and future OM dynamics and associated environmental changes.

An 8,000 year oxygen isotope record of hydroclimatic change from Paradise Lake, central British Columbia

NASA Astrophysics Data System (ADS)

Hillman, A. L.; Abbott, M. B.; Steinman, B. A.; Pompeani, D. P.; Cwiklik, J. P.

2013-12-01

Climate in the Pacific Northwest over the Holocene has primarily been controlled by the position of the Aleutian Low (AL), which is interconnected to the Pacific Decadal Oscillation (PDO) and the El Nino Southern Oscillation (ENSO). Stable isotopes of authigenic calcite precipitated from lake water and archived as lake sediment can be used to reconstruct changes in precipitation/evaporation (P/E) balance over timescales ranging from individual years to millennia. Several records of this type from southern British Columbia and northern Washington (e.g., Castor and Cleland Lakes), as well as from the southern Yukon Territory (e.g., Marcella and Rantin Lakes) have been produced, but few records from between these two regions exist. Here, we present a record of δ18O and δ13C measurements of authigenic calcite from Paradise Lake, British Columbia (54.68259°N, 122.61154°W), a surficially closed basin, groundwater throughflow lake located in the central interior of British Columbia. A total of 14 AMS radiocarbon dates were used to provide age control for the Paradise Lake record. In sediment from 8,000-4,500 years BP, oxygen isotope values vary around a mean value of -18.0‰. From 4,500-2,000 years BP, a general trend towards more positive oxygen isotope values occurs, with increased variability in both δ18O and δ13C. A gradual shift of ~2‰ in δ18O measurements (to a mean value of -16.0‰) occurs over the last 2,000 years of the record, likely due to lower lake levels. The large magnitude mean state shifts in oxygen isotopes over the last 8,000 years are similar to that observed in the Marcella Lake record (Anderson et al., 2007), although they are of a smaller magnitude. We hypothesize that significant groundwater throughflow at Paradise Lake likely causes a muted hydrologic and isotopic response to climate forcing relative to Marcella Lake, which has more isotopically enriched water and loses a greater proportion of water via evaporation. The Paradise lake �

Parametrization of environment by geochemistry of the varved clastic and bio- chemogenic lake sediments

NASA Astrophysics Data System (ADS)

Kalugin, Ivan; Darin, Andrey; Babich, Valery; Markovich, Tatiana; Meydan, Feray

2017-04-01

As it well known, recent quantitative estimations of high-resolution environmental variability are based on geochemical records in lake sediments. Naturally, annually laminated sediments (varves) are the best objects for paleoclimatic study, because they allow to investigate seasonal variability for understanding long-term environmental pattern. Also, varved sediments seem to be applied as the model for identification of element-indicators for non-laminated sediments. The XRF scanner on Synchrotron Radiation provides big geochemical dataset for next mathematic treatment, including time series construction. XRF scanning realizes rapid and non-destructive determinations more than 30 trace elements in a range of concentration from 1 up to 10000 ppm in annual layers. That makes sedimentary cores comparable with tree-rings. Geochemical and physicochemical investigation of lake sediments provides basic information to identify geochemical signals with paleoclimate. In general, sediment consists of mineral component, organics and carbonates. The proportions between these components are affected by environmental parameters, because measured element content or their combinations show correlation with meteodata on instrumental time interval. That allows applying geochemical variability to reconstruct the environmental parameters in the form of time series. The proportions between main components are controlled by temperature, atmospheric precipitation, water salinity and other external forcings. So, layered structure of lake bottom sediments and detectable elements content variability both represent a continuous record of environmental history. Element composition and it's climatic response. Bottom sediments represent conditions of physical weathering, temperate bioproductivity and aridity, which concern to mountain lakes within extra tropical zone. The numerical values of the parameters can be computed by software of physical-chemical modeling for gas+water+rock multisystems

Optimal control of suspended sediment distribution model of Talaga lake

NASA Astrophysics Data System (ADS)

Ratianingsih, R.; Resnawati, Azim, Mardlijah, Widodo, B.

2017-08-01

Talaga Lake is one of several lakes in Central Sulawesi that potentially to be managed in multi purposes scheme because of its characteristic. The scheme is addressed not only due to the lake maintenance because of its sediment but also due to the Algae farming for its biodiesel fuel. This paper governs a suspended sediment distribution model of Talaga lake. The model is derived from the two dimensional hydrodynamic shallow water equations of the mass and momentum conservation law of sediment transport. An order reduction of the model gives six equations of hyperbolic systems of the depth, two dimension directional velocities and sediment concentration while the bed elevation as the second order of turbulent diffusion and dispersion are neglected. The system is discreted and linearized such that could be solved numerically by box-Keller method for some initial and boundary condition. The solutions shows that the downstream velocity is play a role in transversal direction of stream function flow. The downstream accumulated sediment indicate that the suspended sediment and its changing should be controlled by optimizing the downstream velocity and transversal suspended sediment changing due to the ideal algae growth need.

Jellyfish Lake, Palau: early diagenesis of organic matter in sediments of an anoxic marine lake

USGS Publications Warehouse

Orem, W.H.; Burnett, W.C.; Landing, W.M.; Lyons, W.B.; Showers, W.

1991-01-01

The major postdepositional change in the sedimentary organic matter is carbohydrate biodegradation. Lignin and aliphatic substances are preserved in the sediments. Dissolved organic matter in pore waters is primarily composed of carbohydrates, reflecting the degradation of sedimentary carbohydrates. Rate constants for organic carbon degradation and sulfate reduction in sediments of the lake are about 10?? lower than in other anoxic sediments. This may reflect the vascular plant source and partly degraded nature of the organic matter reaching the sediments of the lake. -from Authors

Holocene glacier fluctuations inferred from lacustrine sediment, Emerald Lake, Kenai Peninsula, Alaska

NASA Astrophysics Data System (ADS)

LaBrecque, Taylor S.; Kaufman, Darrell S.

2016-01-01

Physical and biological characteristics of lacustrine sediment from Emerald Lake were used to reconstruct the Holocene glacier history of Grewingk Glacier, southern Alaska. Emerald Lake is an ice-marginal threshold lake, receiving glaciofluvial sediment when Grewingk Glacier overtops the topographic divide that separates it from the lake. Sub-bottom acoustical profiles were used to locate core sites to maximize both the length and resolution of the sedimentary sequence recovered in the 4-m-long cores. The age model for the composite sequence is based on 13 14C ages and a 210Pb profile. A sharp transition from the basal inorganic mud to organic-rich mud at 11.4 ± 0.2 ka marks the initial retreat of Grewingk Glacier below the divide of Emerald Lake. The overlaying organic-rich mud is interrupted by stony mud that records a re-advance between 10.7 ± 0.2 and 9.8 ± 0.2 ka. The glacier did not spill meltwater into the lake again until the Little Ice Age, consistent with previously documented Little Ice Ages advances on the Kenai Peninsula. The retreat of Grewingk Glacier at 11.4 ka took place as temperature increased following the Younger Dryas, and the subsequent re-advance corresponds with a climate reversal beginning around 11 ka across southern Alaska.

Pleistocene lake outburst floods and fan formation along the eastern Sierra Nevada, California: implications for the interpretation of intermontane lacustrine records

NASA Astrophysics Data System (ADS)

Benn, Douglas I.; Owen, Lewis A.; Finkel, Robert C.; Clemmens, Samuel

2006-11-01

Variations in the rock flour fraction in intermontane lacustrine sediments have the potential to provide more complete records of glacier fluctuations than moraine sequences, which are subject to erosional censoring. Construction of glacial chronologies from such records relies on the assumption that rock flour concentration is a simple function of glacier extent. However, other factors may influence the delivery of glacigenic sediments to intermontane lakes, including paraglacial adjustment of slope and fluvial systems to deglaciation, variations in precipitation and snowmelt, and lake outburst floods. We have investigated the processes and chronology of sediment transport on the Tuttle and Lone Pine alluvial fans in the eastern Sierra Nevada, California, USA, to elucidate the links between former glacier systems located upstream and the long sedimentary record from Owens Lake located downstream. Aggradation of both fans reflects sedimentation by three contrasting process regimes: (1) high magnitude, catastrophic floods, (2) fluvial or glacifluvial river systems, and (3) debris flows and other slope processes. Flood deposits are represented by multiple boulder beds exposed in section, and extensive networks of large palaeochannels and boulder deposits on both fan surfaces. Palaeohydrological analysis implies peak discharges in the order of 10 3-10 4 m 3 s -1, most probably as the result of catastrophic drainage of ice-, moraine-, and landslide-dammed lakes. Cosmogenic radionuclide surface exposure dating shows that at least three flood events are represented on each fan, at 9-13, 16-18 and 32-44 ka (Tuttle Fan); and at ˜23-32, ˜80-86 ka, and a poorly constrained older event (Lone Pine Fan). Gravels and sands exposed in both fans represent fluvial and/or glacifluvial sediment transport from the Sierra Nevada into Owens Valley, and show that river systems incised and reworked older sediment stored in the fans. We argue that millennial-scale peaks in rock flour

Phosphorus in sediment in the Kent Park Lake watershed, Johnson County, Iowa, 2014–15

USGS Publications Warehouse

Kalkhoff, Stephen J.

2016-07-12

Phosphorus data were collected from the Kent Park Lake watershed in Johnson County, Iowa, in 2014 and 2015 to obtain information to assist in the management of the water quality in the lake. Phosphorus concentrations were measured for sediment from several ponds in the watershed and sediment deposited in the lake. The first set of samples was collected in 2014 to understand phosphorus in several potential sources to the lake and the spatial variability in lake sediments. Phosphorus concentrations ranged from 68 to 380 milligrams per kilogram in lake sediment and from 57 to 220 milligrams per kilogram in sedimentation and dredge spoil ponds. Additional samples were collected in 2015 to determine how phosphorus concentrations vary with depth in the lake sediment. Phosphorus concentrations generally decreased with increasing depth within the lake sediment. In 2015, total phosphorus concentrations in lake sediment ranged from 50 to 340 milligrams per kilogram.

Acoustic stratigraphy of Bear Lake, Utah-Idaho: late Quaternary sedimentation patterns in a simple half-graben

USGS Publications Warehouse

Colman, Steven M.

2006-01-01

A 277-km network of high-resolution seismic-reflection profiles, supplemented with a sidescan-sonar mosaic of the lake floor, was collected in Bear Lake, Utah–Idaho, in order to explore the sedimentary framework of the lake's paleoclimate record. The acoustic stratigraphy is tied to a 120 m deep, continuously cored drill hole in the lake. Based on the age model for the drill core, the oldest continuously mapped acoustic reflector in the data set has an age of about 100 ka, although older sediments were locally imaged. The acoustic stratigraphy of the sediments below the lake indicates that the basin developed primarily as a simple half-graben, with a steep normal-fault margin on the east and a flexural margin on the west. As expected for a basin controlled by a listric master fault, seismic reflections steepen and diverge toward the fault, bounding eastward-thickening sediment wedges. Secondary normal faults west of the master fault were imaged beneath the lake and many of these faults show progressively increasing offset with depth and age. Several faults cut the youngest sediments in the lake as well as the modern lake floor. The relative simplicity of the sedimentary sequence is interrupted in the northwestern part of the basin by a unit that is interpreted as a large (4 × 10 km) paleodelta of the Bear River. The delta overlies a horizon with an age of about 97 ka, outcrops at the lake floor and is onlapped by much of the uppermost sequence of lake sediments. A feature interpreted as a wave-cut bench occurs in many places on the western side of the lake. The base of this bench occurs at a depth (22–24 m) similar to that (20–25 m) of the distal surface of the paleodelta. Pinch-outs of sedimentary units are common in relatively shallow water on the gentle western margin of the basin and little Holocene sediment has accumulated in water depths of less than 30 m. On the steep eastern margin of the basin, sediments commonly onlap the hanging wall of the East

Analysis of elements in lake sediment samples by PIXE spectrometry

NASA Astrophysics Data System (ADS)

Chelarescu, E. D.; Radulescu, C.; Stihi, C.; Bretcan, P.; Tanislav, D.; Dulama, I. D.; Stirbescu, R. M.; Teodorescu, S.; Bucurica, I. A.; Andrei, R.; Morarescu, C.

2017-09-01

This work aims to determine the concentrations of several elements (e.g. Pb, Ni, Zn, Mn, Cr, and Fe) from lake sediments, in order to characterize their origin and evolution. Particle Induced X-ray Emission (PIXE) technique using the 3 MV Tandetron™ particle accelerator from National Institute for R&D in Physics and Nuclear Engineering "Horia Hulubei" (IFIN-HH), Magurele-Bucharest, Romania, was applied. Sediment cores from different salt lakes from Romania (i.e. Amara Lake, Caineni Lake, and Movila Miresii Lake) were collected, in August 2015. The content of Pb, Cr, Mn, Fe, and Ni from sediment samples show similarities with other data presented in literature and international regulation. The Zn was the only element with a higher content in all samples (e.g. maximum 401.7-517.3 mg/kg d.w.).

Geochemistry and Mineralogy of Western Australian Salt Lake Sediments: Implications for Meridiani Planum on Mars.

PubMed

Ruecker, A; Schröder, C; Byrne, J; Weigold, P; Behrens, S; Kappler, A

2016-07-01

Hypersaline lakes are characteristic for Western Australia and display a rare combination of geochemical and mineralogical properties that make these lakes potential analogues for past conditions on Mars. In our study, we focused on the geochemistry and mineralogy of Lake Orr and Lake Whurr. While both lakes are poor in organic carbon (<1%), the sediments' pH values differ and range from 3.8 to 4.8 in Lake Orr and from 5.4 to 6.3 in Lake Whurr sediments. Lake Whurr sediments were dominated by orange and red sediment zones in which the main Fe minerals were identified as hematite, goethite, and tentatively jarosite and pyrite. Lake Orr was dominated by brownish and blackish sediments where the main Fe minerals were goethite and another paramagnetic Fe(III)-phase that could not be identified. Furthermore, a likely secondary Fe(II)-phase was observed in Lake Orr sediments. The mineralogy of these two salt lakes in the sampling area is strongly influenced by events such as flooding, evaporation, and desiccation, processes that explain at least to some extent the observed differences between Lake Orr and Lake Whurr. The iron mineralogy of Lake Whurr sediments and the high salinity make this lake a suitable analogue for Meridiani Planum on Mars, and in particular the tentative identification of pyrite in Lake Whurr sediments has implications for the interpretation of the Fe mineralogy of Meridiani Planum sediments. Western Australia-Salt lakes-Jarosite-Hematite-Pyrite-Mars analogue. Astrobiology 16, 525-538.

Seasonal Variations in Water Chemistry and Sediment Composition in Three Minnesota Lakes

NASA Astrophysics Data System (ADS)

Lascu, I.; Ito, E.; Banerjee, S.

2006-12-01

Variations in water chemistry, isotopic composition of dissolved inorganic carbon, sediment geochemistry and mineral magnetism were monitored for several months in three Minnesota lakes. Lake McCarrons, Deming Lake and Steel Lake are all small (<1 km2), deep (>16 m), stratified lakes that contain varved sediments for some time intervals or throughout. Deming Lake and Steel Lake are situated in north-central Minnesota, about 40 km apart, while Lake McCarrons is located in the heart of the Twin Cities and is heavily used for recreational purposes. The lakes have different mixing regimes (Steel is dimictic, Deming is meromictic and McCarrons is oligomictic) but all have well defined epilimnia and hypolimnia during the ice-free season. Water samples were collected bi-weekly from the epilimnia, upper and lower hypolimnia, while sediments were collected monthly from sediment traps placed in shallow and deep parts of the lakes. All lakes are moderately alkaline (80-280 ppm HCO3-) carbonate-producing systems, although calcite is being dissolved in the slightly acidic hypolimnetic waters of Deming Lake. The magnetic parameters reveal different distributions of the magnetic components in the three lakes, but all exhibit a general increase in the concentration of bacterial magnetosomes towards the end of summer. Differences in elemental concentrations, cation and anion profiles, and chemical behavior as the season progressed are also obvious among the three lakes. For the two lakes situated in the same climatic regime, this implies additional controls (besides climate) on water and sediment composition, such as local hydrology, substrate composition and biogeochemical in-lake processes.

Temperature Dependence of Apparent Respiratory Quotients and Oxygen Penetration Depth in Contrasting Lake Sediments

NASA Astrophysics Data System (ADS)

Sobek, Sebastian; Gudasz, Cristian; Koehler, Birgit; Tranvik, Lars J.; Bastviken, David; Morales-Pineda, María.

2017-11-01

Lake sediments constitute an important compartment in the carbon cycle of lakes, by burying carbon over geological timescales and by production and emission of greenhouse gases. The degradation of organic carbon (OC) in lake sediments is linked to both temperature and oxygen (O2), but the interactive nature of this regulation has not been studied in lake sediments in a quantitative way. We present the first systematic investigation of the effects of temperature on the apparent respiratory quotient (RQ, i.e., the molar ratio between carbon dioxide (CO2) production and O2 consumption) in two contrasting lake sediments. Laboratory incubations of sediment cores of a humic lake and an eutrophic lake across a 1-21°C temperature gradient over 157 days revealed that both CO2 production and O2 consumption were positively, exponentially, and similarly dependent on temperature. The apparent RQ differed significantly between the lake sediments (0.63 ± 0.26 and 0.99 ± 0.28 in the humic and the eutrophic lake, respectively; mean ± SD) and was significantly and positively related to temperature. The O2 penetration depth into the sediment varied by a factor of 2 over the 1-21°C temperature range and was significantly, negatively, and similarly related to temperature in both lake sediments. Accordingly, increasing temperature may influence the overall extent of OC degradation in lake sediments by limiting O2 supply to aerobic microbial respiration to the topmost sediment layer, resulting in a concomitant shift to less effective anaerobic degradation pathways. This suggests that temperature may represent a key controlling factor of the OC burial efficiency in lake sediments.

The Geologic History of Lake of the Woods, Minnesota, Reconstructed Using Seismic-Reflection Imaging and Sediment Core Analysis

NASA Astrophysics Data System (ADS)

Hougardy, Devin D.

only near the margins of the basin, suggesting that water occupied much of the middle of the southern basin after lake level drawdown. The reflection character and configuration of SU-C and SU-D are genetically different indicating that the depositional environment had changed following the formation of UNCF-2. Piston-type sediment cores collected from the southern basin of LOTW at depths that correspond to the middle of SU-D contain high amounts of organic material and charcoal fragments and sediment that are probably not related to Lake Agassiz. Instead, they were likely deposited during a transitional phase between when Lake Agassiz left the LOTW basin (UNCF-2) and inundation of LOTW from the northern basin due to differential isostatic rebound (UNCF-3). All sediment cores collected from the southern basin of LOTW record the uppermost unconformity, analogous in depth to UNCF-3 in the seismic images, which separates modern sediments from mid to late-Holocene sediments. The lithology of sediments below this unconformity varies across the basin from gray clay to laminated silt and clay. Radiocarbon ages from two peat layers immediately below the unconformity indicate that subaerial conditions had existed prior to the formation of UNCF-1, at about 7.75 ka cal BP. The timing correlates well with other lakes in the upper Midwest that record a prolonged dry climate during the mid-Holocene. UNCF-3 is planar and erosional across the entire survey area but erosion is greatest in the northern part of the basin as the result of a southward transgressing wave base driven by differential isostatic rebound. Deposition in the southern basin probably resumed around 3.3 ka cal BP, though no radiocarbon dates were collected directly above UNCF-3. The lithology of sediment above UNCF-3 is highly uniform across the basin and represents modern sedimentation. Late-Holocene sedimentation rates were calculated at about 0.9 mm year-1 and are roughly double the sedimentation rates in the NW

Hydrologic and Suspended-Sediment Data for Reelfoot Lake, Obion and Lake Counties, Northwestern Tennessee, May 1985-September 1986

DTIC Science & Technology

1986-01-01

DATE 1986 2. REPORT TYPE N/A 3. DATES COVERED - 4. TITLE AND SUBTITLE Hydrologic and Suspended-Sediment Data for Reelfoot Lake , Obion and...ANSI Std Z39-18 Ii-nmRO IiO~IC l!!Jm srLISPENDED- SEDIMENT DATA FOR REELFOOT LAKE , OBION AND LAKE COIJNTHES, IWXUWWESTERN TENNESSEE, IMAY...references 4 Hydrologic data 5 1. !Uap showing location of project area, Reelfoot Lake , streamflow monitoring stations. lake -stage monitoring

Lake level and climate records of the last 90 ka from the Northern Basin of Lake Van, eastern Turkey

NASA Astrophysics Data System (ADS)

Çağatay, M. N.; Öğretmen, N.; Damcı, E.; Stockhecke, M.; Sancar, Ü.; Eriş, K. K.; Özeren, S.

2014-11-01

Sedimentary, geochemical and mineralogical analyses of the ICDP cores recovered from the Northern Basin (NB) of Lake Van provide evidence of lake level and climatic changes related to orbital and North Atlantic climate system over the last 90 ka. High lake levels are generally observed during the interglacial and interstadial periods, which are marked by deposition of varved sediments with high total organic carbon (TOC), total inorganic carbon (TIC), low detrital influx (high Ca/F) and high δ18O and δ13C values of authigenic carbonate. During the glacial and stadial periods of 71-58 ka BP (Marine Isotope Stage 4, MIS4) and end of last glaciation-deglaciation (30-14.5 ka BP; MIS3) relatively low lake levels prevailed, and grey homogeneous to faintly laminated clayey silts were deposited at high sedimentation and low organic productivity rates. Millennial-scale variability of the proxies during 60-30 ka BP (MIS3 is correlated with the Dansgaard-Oeschger (D-O)) and Holocene abrupt climate events in the Atlantic. These events are characterized by laminated sediments, with high TOC, TIC, Ca/Fe, δ18O and δ13C values. The Lake Van NB records correlate well in the region with the climate records from the lakes Zeribar and Urmia in Iran and the Sofular Cave in NW Anatolia, but are in general in anti-phase to those from the Dead Sea Basin (Lake Lisan) in the Levant. The relatively higher δ18O values (0 to -0.4‰) for the interglacial and interstadial periods in the Lake Van NB section are due to the higher temperature and seasonality of precipitation and higher evaporation, whereas the lower values (-0.8 to -2‰) during the glacial and stadial periods are caused mainly by relative decrease in both temperature and seasonality of precipitation. The high δ18O values (up to 4.2‰) during the Younger Dryas, together with the presence of dolomite and low TOC contents, supports evaporative conditions and low lake level. A gradual decrease in the δ18O values from an

Human Impact on Biogeochemical Cycles and Deposition Dynamics in Karstic Lakes: El Tobar Lake Record (Central Iberian Range, Spain)

NASA Astrophysics Data System (ADS)

Barreiro-Lostres, F.; Moreno-Caballud, A.; Giralt, S.; Hillman, A. L.; Brown, E. T.; Abbott, M. B.; Valero-Garces, B. L.

2014-12-01

Karstic lakes in the Iberian Range (Central Spain) provide a unique opportunity to test the human impact in the watersheds and the aquatic environments during historical times. We reconstruct the depositional evolution and the changes in biogeochemical cycles of El Tobar karstic lake, evaluating the response and the resilience of this Mediterranean ecosystem to both anthropogenic impacts and climate forcing during the last 1000 years. Lake El Tobar (40°32'N, 3°56'W; 1200 m a.s.l.; see Figure), 16 ha surface area, 20 m max. depth and permanent meromictic conditions, has a relatively large watershed (1080 ha). Five 8 m long sediment cores and short gravity cores where recovered, imaged, logged with a Geotek, described and sampled for geochemical analyses (elemental TOC, TIC, TN, TS), XRF scanner and ICP-MS, and dated (137Cs and 10 14C assays). The record is a combination of: i) laminated dark silts with terrestrial remains and diatoms and ii) massive to banded light silts (mm to cm -thick layers) interpreted as flood deposits. Sediments, TOC, and Br/Ti and Sr/Ca ratios identify four periods of increased sediment delivery occurred about 1500, 1800, 1850 and 1900 AD, coinciding with large land uses changes of regional relevance such as land clearing and increased population. Two main hydrological changes are clearly recorded in El Tobar sequence. The first one, marked by a sharp decrease in Mg, Ca and Si concentrations, took place about 1200 AD, and during a period of increasing lake level, which shifted from shallower to deeper facies and from carbonatic to clastic and organic-rich deposition. This change was likely related to increased water availability synchronous to the transition from the Medieval Climate Anomaly to the Little Ice Age. The second one was a canal construction in 1967 AD when a nearby reservoir provided fresh water influx to the lake, and resulted in stronger meromictic conditions in the system after canal construction, which is marked by lower

Holocene Record Of The Cuitzeo Lake, Michoacan, Central Mexico

NASA Astrophysics Data System (ADS)

Israde-Alcantar, I.; Bischoff, J.; Cram, S.; Ruiz-Fernandez, C.; Barron, J.; Lozano-Garcia, S.; Ortega-Guerrero, B.; Garduño-Monroy, V. H.

2007-05-01

A 205 cm-long core spanning the last ca.10,000 years was taken in the western basin of Lake Cuitzeo, located in the tectonic depressions of central Mexico. Age control for the core is provided by four AMS dates on organic sediment. The uppermost 30 cm of the core appears to be highly bioturbated according to Pb210 chronologies. A time plot of mass-accumulation rates of sediment (g/cm2/kyr) shows high rates from 10,000 to 6000 yrs BP, strikingly reduced mid-Holocene rates, and increasing rates post 1000 yrs (which could be due to introduction of European ranching and agriculture). Organic and inorganic carbon (TOC. TIC), diatoms, iron and titanium concentrations were analyzed and used to infer variations in the hydrological cycle and climatic conditions. The lower part of the core (ca.8000 C14 yr B.P.) is characterized by high percents of CaCO3 (more than 35 percent) which rapidly declines to values less than 20 percent after ca. 6000 C14 yr B.P., likely reflecting reduced summer precipitation due to decline summer insolation. Coincident with this decline in percents CaCO3 there is a decline greater that two-fold sediment accumulation rates and an increase in percents TOC. Two peaks TOC are recorded at 909 and 6744 C14 yr B.P. suggesting increased precipitation. The TOC peak at 909 C14 yr B.P. may be associated with increased precipitation during the Medieval Warm Period. The middle Holocene TOC peak at 6744 C14 yr B.P. coincides with a period of increased precipitation in the Cariaco Basin of Venezuela. These changes in precipitation are similar to those recorded in lake records from Guatemala and the marine record of the Cariaco Basin and can be explained by shifts in the mean latitude of the Atlantic Intertropical Convergence Zone (ITCZ). The upper 100 cm of the core was studied at 1 cm intervals for metals (Al, Fe, Ti, Pb, etc.) using ICPMS geochemistry. These metals show strong cycles throughout the studied interval which may reflect wet-dry cycles. A two fold

Sediment transport and deposition in Lakes Marion and Moultrie, South Carolina, 1942-85

USGS Publications Warehouse

Patterson, G.G.; Cooney, T.W.; Harvey, R.M.

1996-01-01

Lakes Marion and Moultrie, two large reservoirs in the South Carolina Coastal Plain, receive large inflows of sediment from the Santee River. The average rate of sediment deposition for both lakes during the period 1942-85 was about 0.06 inch per year, or about 800 acre-feet per year. The rate during 1983-85 was about 0.037 inch per year, or about 490 acre-feet per year, reflecting the decreasing trend in sediment inflow. This is a reversal of a trend toward increasing suspended- sediment concentrations in streams that were caused by farming practices in the southern Piedmont from about 1800 to about 1920. Only a small part of the eroded sediment has been carried out of the Piedmont, but the remaining sediment is becoming less available for transport. Sediment deposition is concentrated in several areas of upper Lake Marion where the velocity of the incoming water decreases significantly. Beds of aquatic macrophytes appear to encourage deposition which, in turn, creates favorable habitat for the plants. The rate of sediment accumulation in Lakes Marion and Moultrie averaged 650,000 tons per year during 1983-85, reflecting a trap efficiency of 79 percent of the total sediment inflow of 825,000 tons per year. Thickness of post-impoundment sediment varies from about 11 feet near the mouth of the Santee River in Lake Marion to 0 feet in Lake Moultrie near Bonneau. Sediments in Lake Marion tend to have finer texture and higher contents of organic matter, nutrients, and trace metals than those in Lake Moultrie.

A 27 ka paleoenvironmental lake sediment record from Taro Co, central Tibetan Plateau: implications for the interplay between monsoon and the Westerlies

NASA Astrophysics Data System (ADS)

Wang, J.; Ma, Q.; Huang, L.; Ju, J.; Guo, Y.; Lin, X.; Li, Y.; Zhu, L.

2017-12-01

The climate of Tibetan Plateau (TP) is mainly influenced by the Indian Ocean Summer Monsoon (IOSM) and the Westerlies. The interaction of these two air masses is therefore a crucial scientific issue to understand how they impact the climate in this area, especially in the geological times. However, constrained by the available archives, researches on this topic are still very few in the hinterland of the TP, especially covering the Last Glacial Maximum (LGM) period. Here we present a new lake sediment record retrieved from Taro Co covering the last 27 ka to elucidate how the IOSM and the Westerlies interact and the possible mechanisms. Taro Co (486 km2, Dmax: 132m, 4565 m a.s.l., currently closed), located on the central TP, is a fresh lake with the major supply from glaciers. Two parallel piston cores as well as several gravity cores were retrieved from the deepest parts. These cores were correlated based on high resolution XRF scanning and a continuous 1069 cm-long core was finally integrated. Chronology was determined by 210Pb, 137Cs and AMS 14C measurements. Multidiscipline analyses including grain size, total organic carbon (TOC), total nitrogen, diatom, ostracod, pollen and n-alkanes were accomplished to reconstruct paleoenvironmental changes. The lake level of Taro Co was low since 27 cal ka BP indicated by very coarse materials and diatom assemblages with gradually increased temperature and salinity (TOC and carbonate getting higher). The terrestrial water input decreased continuously reflected by such elements as Si, Ti, Fe, K. It is likely that there was a sedimentation gap between 961-954cm, corresponding to 23.4 to 18.6 cal ka BP probably demonstrated Taro Co was very shallow at that period. The first prominent abrupt change of most proxies was observed at 14.7 cal ka BP showing a great lake deepening which likely indicated an enhancement of IOSM. There were several spells with abrupt changes of cold/warm stages before the Holocene and the Younger Dryas

Identifying water-quality trends in the Trinity River, Texas, USA, 1969-1992, using sediment cores from Lake Livingston

USGS Publications Warehouse

Van Metre, P.C.; Callender, E.

1996-01-01

Chemical analyses were done on cores of bottom sediment from three locations in Lake Livingston, a reservoir on the Trinity River in east Texas to identify trends in water quality in the Trinity River using the chemical record preserved in bottom sediments trapped by the reservoir. Sediment cores spanned the period from 1969, when the reservoir was impounded, to 1992, when the cores were collected. Chemical concentrations in reservoir sediment samples were compared to concentrations for 14 streambed sediment samples from the Trinity River Basin and to reported concentrations for soils in the eastern United States and shale. These comparisons indicate that sediments deposited in Lake Livingston are representative of the environmental setting of Lake Livingston within the Trinity River Basin. Vertical changes in concentrations within sediment cores indicate temporal trends of decreasing concentrations of lead, sodium, barium, and total DDT (DDT plus its metabolites DDD and DDE) in the Trinity River. Possible increasing temporal trends are indicated for chlordane and dieldrin. Each sediment-derived trend is related to trends in water quality in the Trinity River or known changes in environmental factors in its drainage basin or both.

Microplastic pollution in lakes and lake shoreline sediments - A case study on Lake Bolsena and Lake Chiusi (central Italy).

PubMed

Fischer, Elke Kerstin; Paglialonga, Lisa; Czech, Elisa; Tamminga, Matthias

2016-06-01

Rivers and effluents have been identified as major pathways for microplastics of terrestrial sources. Moreover, lakes of different dimensions and even in remote locations contain microplastics in striking abundances. This study investigates concentrations of microplastic particles at two lakes in central Italy (Lake Bolsena, Lake Chiusi). A total number of six Manta Trawls have been carried out, two of them one day after heavy winds occurred on Lake Bolsena showing effects on particle distribution of fragments and fibers of varying size categories. Additionally, 36 sediment samples from lakeshores were analyzed for microplastic content. In the surface waters 2.68 to 3.36 particles/m(3) (Lake Chiusi) and 0.82 to 4.42 particles/m(3) (Lake Bolsena) were detected, respectively. Main differences between the lakes are attributed to lake characteristics such as surface and catchment area, depth and the presence of local wind patterns and tide range at Lake Bolsena. An event of heavy winds and moderate rainfall prior to one sampling led to an increase of concentrations at Lake Bolsena which is most probable related to lateral land-based and sewage effluent inputs. The abundances of microplastic particles in sediments vary from mean values of 112 (Lake Bolsena) to 234 particles/kg dry weight (Lake Chiusi). Lake Chiusi results reveal elevated fiber concentrations compared to those of Lake Bolsena what might be a result of higher organic content and a shift in grain size distribution towards the silt and clay fraction at the shallow and highly eutrophic Lake Chiusi. The distribution of particles along different beach levels revealed no significant differences. Copyright © 2016 Elsevier Ltd. All rights reserved.

Spatial and Temporal Variability of Dust Deposition in the San Juan Mountains, CO: A Network of Late Holocene Lake Sediment Records

NASA Astrophysics Data System (ADS)

Arcusa, S.; Routson, C.; McKay, N.

2017-12-01

Millions of stakeholders living in the arid southwestern US rely on snowmelt from the San Juan Mountains of Colorado. However, dust deposition on snow accelerates snowmelt, challenging water management. Dustiness in the southwestern US is primarily mediated by drought, which is projected to increase in frequency and severity. Over the past several millennia, multidecadal-length megadroughts are hypothesized to have enhanced regional dustiness. These past megadroughts were more frequent during the Roman (ca. 1-400 CE) and Medieval (ca. 800-1300 CE) time periods and were similar in duration and severity to those projected for the future. Developing an understanding of the temporal and spatial patterns of past dust deposition in the San Juan Mountains will help inform adaptation strategies for future droughts. A network of short sediment cores from six alpine lakes in the San Juan Mountains were collected in 2016 and 2017 to investigate the spatial patterns of dust deposition. The range in lake basin characteristics in the network, such as catchment size, helps to constrain the influence of secondary dust deposition. Grain size analysis and X-ray Fluorescence were combined with radiocarbon dating to trace the temporal patterns in dust flux over the Late Holocene (the last 2000 years). The End-member Modelling Algorithm (EMMA) was used to estimate the dust proportion in the lake sediment, distinguishing from locally derived catchment material. Comparisons to modern dust-on-snow samples were made to identify the dust size distribution. The results show that deposition trends were not uniform between the south-eastern and north-western San Juans, with increasing trends towards the present in the former, possibly reflecting a shift in dust sources associated with changes in wind speed and direction. Dust levels greater than long term averages were recorded during the Medieval and Roman periods. The network also showed the influence of lake basin parameters, such as the

Subarctic Lake Sediment Microbial Community Contributions to Methane Emission Patterns

NASA Astrophysics Data System (ADS)

Emerson, J. B.; Varner, R. K.; Parks, D.; Wik, M.; Neumann, R.; Johnson, J. E.; Singleton, C. M.; Woodcroft, B. J.; Tollerson, R., II; Owusu-Dommey, A.; Binder, M.; Freitas, N. L.; Crill, P. M.; Saleska, S. R.; Tyson, G. W.; Rich, V. I.

2017-12-01

Northern post-glacial lakes have recently been identified as a significant and increasing source of carbon to the atmosphere, largely through ebullition (bubbling) of microbially produced methane from the sediments. Ebullitive methane flux has been shown to correlate significantly with sediment surface temperatures, suggesting that solar radiation is the primary driver of methane emissions from these lakes. However, the slope of this relationship (i.e., the extent to which increasing temperature increases ebullitive methane emissions) differs spatially, both within and among lakes. As microbes are responsible for both methane generation and removal in lakes, we hypothesized that microbial communities—previously uncharacterized in post-glacial lake sediments—could be contributing to spatiotemporal differences in methane emission responses to temperature. We compared methane emission data with sediment microbial (metagenomic and amplicon), isotopic, and geochemical characterizations across two post-glacial lakes in Northern Sweden. With increasing temperatures, the increase in methane emissions was greater in lake middles (deeper water) than lake edges (shallower water), consistent with higher abundances of methanogens in sediments from lake middles than edges, along with significant differences in microbial community composition between these regions. Using sparse partial least squares statistical modeling, microbial abundances (including the abundances of methane-cycling microorganisms and of reconstructed population genomes, e.g., from Planctomycetes, Thermoplasmatales, and Candidate Phylum Aminicenantes) were better predictors of porewater methane concentrations than abiotic variables. These results suggest that, although temperature controls methane emissions, microbial community composition and function may drive the rate and magnitude of this temperature response in subarctic post-glacial lakes.

Heavy Metal Enrichment in laminated lake sediments from N-Germany and N-Poland: Geochemical background, enrichment history and land surface changes

NASA Astrophysics Data System (ADS)

Hoelzmann, Philipp; Brauer, Achim; Dräger, Nadine; Kienel, Ulrike; Obremska, Milena; Ott, Florian; Słowinski, Michał

2017-04-01

For three lake sediment records, situated in rural environments in NE-Germany (Lake Tiefer See) and N-Poland (Lake Czechowskie, Lake Głęboczek), we present a detailed heavy metal enrichment history with sub-decadal resolution for the last 200 years. We determine the local and specific geogenic background values on the base of heavy-metal analysis of pre-industrial sediments and different sediment types (e.g. calcareous gyttja, organic gyttja etc.). These results provide means to calculate and quantify anthropogenic heavy metal accumulations and enrichment factors as well as to define regional measures for a state of reference, reflecting natural conditions without human impact. All three lakes show a similar pattern of relatively low heavy metal concentrations and only Pb, Zn and Cd show a clear parallel pattern of enrichment starting around 1850. This heavy metal enrichment mainly results from atmospheric input due to increasing industrialization within the framework of the Industrial Revolution. Highest concentrations of Cd, Zn, and Pb occur around 1960 to 1980 and thereafter a clear pattern of declining anthropogenic input is registered. This data is supplemented by calculations of mass accumulation rates to determine heavy metal input to the lakes for the past 200 years. For Lake Czechowskie the heavy metal input to the lake is compared to an on average five year resolved pollen record that reflects changes in land use and vegetation.

Forest fire and climate change in western North America: insights from sediment charcoal records.

Treesearch

Daniel G Gavin; Douglas J Hallett; Feng Sheng Hu; Kenneth P Lertzman; Susan J Prichard; Kendrick J Brown; Jason A Lynch; Patrick Bartlein; David L. Peterson

2007-01-01

Millennial-scale records of forest fire provide important baseline information for ecosystem management, especially in regions with too few recent fires to describe the historical range of variability. Charcoal records from lake sediments and soil profiles are well suited for reconstructing the incidence of past fire and its relationship to changing climate and...

Characterizing the Fate and Mobility of Phosphorus in Utah Lake Sediments

NASA Astrophysics Data System (ADS)

Carling, G. T.; Randall, M.; Nelson, S.; Rey, K.; Hansen, N.; Bickmore, B.; Miller, T.

2017-12-01

An increasing number of lakes worldwide are impacted by eutrophication and harmful algal blooms due to anthropogenic nutrient inputs. Utah Lake is a unique eutrophic freshwater lake that is naturally shallow, turbid, and alkaline with high dissolved oxygen levels that has experienced severe algal blooms in recent years. Recently, the Utah Division of Water Quality has proposed a new limitation of phosphorus (P) loading to Utah Lake from wastewater treatment plants in an effort to mitigate eutrophication. However, reducing external P loads may not lead to immediate improvements in water quality due to the legacy pool of nutrients in lake sediments. The purpose of this study was to characterize the fate and mobility of P in Utah Lake sediments to better understand P cycling in this unique system. We analyzed P speciation, mineralogy, and binding capacity in lake sediment samples collected from 15 locations across Utah Lake. P concentrations in sediment ranged from 615 to 1894 ppm, with highest concentrations in Provo Bay near the major metropolitan area. Sequential leach tests indicate that 25-50% of P is associated with Ca (CaCO₃/ Ca10(PO4)6(OH,F,Cl)2 ≈ P) and 40-60% is associated with Fe (Fe(OOH) ≈ P). Ca-associated P was confirmed by SEM images, which showed the highest P concentrations correlating with Ca (carbonate minerals/apatite). The Ca-associated P fraction is likely immobile, but the Fe-bound P is potentially bioavailable under changing redox conditions. Batch sorption results indicate that lake sediments have a high capacity to absorb and remove P from the water column, with an average uptake of 70-96% removal over the range of 1-10 mg/L P. Mineral precipitation and sorption to bottom sediments is an efficient removal mechanism of P in Utah Lake, but a significant portion of P may be temporarily available for resuspension and cycling in surface waters. Mitigating lake eutrophication is a complex problem that goes beyond decreasing external nutrient

Modeling Hydrodynamics, Water Temperature, and Suspended Sediment in Detroit Lake, Oregon

USGS Publications Warehouse

Sullivan, Annett B.; Rounds, Stewart A.; Sobieszczyk, Steven; Bragg, Heather M.

2007-01-01

Detroit Lake is a large reservoir on the North Santiam River in west-central Oregon. Water temperature and suspended sediment are issues of concern in the river downstream of the reservoir. A CE-QUAL-W2 model was constructed to simulate hydrodynamics, water temperature, total dissolved solids, and suspended sediment in Detroit Lake. The model was calibrated for calendar years 2002 and 2003, and for a period of storm runoff from December 1, 2005, to February 1, 2006. Input data included lake bathymetry, meteorology, reservoir outflows, and tributary inflows, water temperatures, total dissolved solids, and suspended sediment concentrations. Two suspended sediment size groups were modeled: one for suspended sand and silt with particle diameters larger than 2 micrometers, and another for suspended clay with particle diameters less than or equal to 2 micrometers. The model was calibrated using lake stage data, lake profile data, and data from a continuous water-quality monitor on the North Santiam River near Niagara, about 6 kilometers downstream of Detroit Dam. The calibrated model was used to estimate sediment deposition in the reservoir, examine the sources of suspended sediment exiting the reservoir, and examine the effect of the reservoir on downstream water temperatures.

AMS radiocarbon analyses from Lake Baikal, Siberia: Challenges of dating sediments from a large, oligotrophic lake

USGS Publications Warehouse

Colman, Steven M.; Jones, Glenn A.; Rubin, M.; King, J.W.; Peck, J.A.; Orem, W.H.

1996-01-01

A suite of 146 new accelerator-mass spectrometer (AMS) radiocarbon ages provides the first reliable chronology for late Quaternary sediments in Lake Baikal. In this large, highly oligotrophic lake, biogenic and authigenic carbonate are absent, and plant macrofossils are extremely rare. Total organic carbon is therefore the primary material available for dating. Several problems are associated with the TOC ages. One is the mixture of carbon sources in TOC, not all of which are syndepositional in age. This problem manifests itself in apparent ages for the sediment surface that are greater than zero. However, because most of the organic carbon in Lake Baikal sediments is algal (autochthonous) in origin, this effect is limited to about 1000+500 years, which can be corrected, at least for young deposits. The other major problem with dating Lake Baikal sediments is the very low carbon contents of glacial-age deposits, which makes them extremely susceptible to contamination with modern carbon. This problem can be minimized by careful sampling and handling procedures. The ages show almost an order of magnitude difference in sediment-accumulation rates among different sedimentary environments in Lake Baikal, from about 0.04 mm/year on isolated banks such as Academician Ridge, to nearly 0.3 mm/year in the turbidite depositional areas beneath the deep basin floors, such as the Central Basin. The new AMS ages clearly indicate that the dramatic increase in diatom productivity in the lake, as evidenced by increases in biogenic silica and organic carbon, began about 13 ka, in contrast to previous estimates of 7 ka for the age of this transition. Holocene net sedimentation rates may be less than, equal to, or greater than those in the late Pleistocene, depending on the site. This variability reflects the balance between variable terrigenous sedimentation and increased biogenic sedimentation during interglaciations. The ages reported here, and the temporal and spatial variation in

The seismic stratigraphy of Okanagan Lake, British Columbia; a record of rapid deglaciation in a deep 'fiord-lake' basin

NASA Astrophysics Data System (ADS)

Eyles, Nicholas; Mullins, Henry T.; Hine, Albert C.

1991-09-01

This paper presents the first detailed data regarding the newly discovered deep infill of Okanagan Lake. Okanagan Lake (50°00'N, 119°30'W) is 120 km long, ˜ 3-5 km wide and occupies a glacially overdeepened bedrock basin in the southern interior of British Columbia. This basin, and other elongate lakes of the region (e.g. Shuswap, Kootenay, Kalamalka, Canim and Mahood lakes), mark the site of westward flowing ice streams within successive Cordilleran ice sheets. An air gun seismic survey of Okanagan Lake shows that the bedrock floor is nearly 650 m below sea-level, more than 2000 m below the rim of the surrounding plateau. The maximum thickness of Pleistocene sediment in Okanagan Lake basin approaches 800 m. Forty-six seismic reflection traverses and an axial profile show a relatively simple stratigraphy composed of three seismic sequences argued to be no older than the last glacial cycle (< 30 ka). A discontinuous basal unit (sequence I) characterized by large-scale diffractions, and up to 460 m thick, infills the narrow, V-shaped bedrock floor of the basin and is interpreted as a boulder gravel deposited by subglacial meltwaters. Overlying seismic sequence II is composed of two sub-sequences. Sub-sequence IIa is a chaotic to massive facies up to 736 m thick. Lakeshore exposures close to where this unit reaches lake level show deformed and chaotically-bedded glaciolacustrine silts containing gravel lens and large ice-rafted boulders. The surface topography of this sub-sequence is irregular and in general mimics the form of the underlying bedrock as a result of compaction. This sequence passes laterally into stratified facies (sub-sequence IIb) at the northern end of the basin. Seismic sequence II appears to record rapid ice-proximal dumping of glaciolacustrine silt as the Okanagan glacier backwasted upvalley in a deep lake. A thin (60 m max.) laminated seismic sequence (III) drapes the hummocky surface of sequence II and represents postglacial sedimentation

Reconstruction of Holocene Climate Variability within the Central Mediterranean Using Lake Sediments from the Akrotiri Peninsula, Crete

NASA Astrophysics Data System (ADS)

Magill, C. R.; Rosenmeier, M. F.; Cavallari, B. J.; Curtis, J. H.; Weiss, H.

2005-12-01

Middle and late Holocene geochemical records from the Limnes depression, a small sinkhole located within the Akrotiri Peninsula, Crete, document centennial and millennial-scale climate variability within the central Mediterranean region. The oldest sediments of the basin consist largely of fibrous plant macrofossils and organic matter and likely indicate lake filling and expansion of wetland vegetation beginning ~5700 radiocarbon years before present (14C-yrs B.P.) (4550 B.C.). The basal peat layers grade into predominantly open water and less shallow lacustrine deposits by 4500 14C-yrs B.P (3200 B.C.). Continuous open water sedimentation within the Limnes core is interrupted by a number of distinct lag deposits and peaty deposits centered at 3700, 1600, and 350 14C-yrs B.P (2100 B.C., 500 A.D., and 1500 A.D.) indicating periods of significantly lowered lake level or perhaps lake desiccation. These ages coincide roughly with oxygen isotope (δ18O) minima measured in biogenic carbonates (ostracod shells) and support the inference for low lake stage. Trace element (Ca, Mg, and Sr) concentrations in ostracod shells from the Limnes core parallel the oxygen isotope record, suggesting that the data reflect basin hydrology rather than changes in the isotopic composition of rainfall. Furthermore, covariance in both δ18O and Mg concentrations eliminate temperature as a control on the oxygen isotope record. Sediments from the basin also contain aragonite remains of the green alga Chara and isotope analysis of the calcite may record additional paleoenvironmental information. The paleoclimate history inferred from the Limnes record correlates temporally (albeit tenuously) to previous paleoenvironmental data that document abrupt onset of arid conditions in the eastern Mediterranean and western Asia ca. 2200 B.C. Moreover, stratigraphic and geochemical evidence of low lake level (drying) within the Limnes basin at 2100 B.C. may correspond to the termination of the Early Minoan

Geomicrobiological Features of Ferruginous Sediments from Lake Towuti, Indonesia

PubMed Central

Vuillemin, Aurèle; Friese, André; Alawi, Mashal; Henny, Cynthia; Nomosatryo, Sulung; Wagner, Dirk; Crowe, Sean A.; Kallmeyer, Jens

2016-01-01

Lake Towuti is a tectonic basin, surrounded by ultramafic rocks. Lateritic soils form through weathering and deliver abundant iron (oxy)hydroxides but very little sulfate to the lake and its sediment. To characterize the sediment biogeochemistry, we collected cores at three sites with increasing water depth and decreasing bottom water oxygen concentrations. Microbial cell densities were highest at the shallow site—a feature we attribute to the availability of labile organic matter (OM) and the higher abundance of electron acceptors due to oxic bottom water conditions. At the two other sites, OM degradation and reduction processes below the oxycline led to partial electron acceptor depletion. Genetic information preserved in the sediment as extracellular DNA (eDNA) provided information on aerobic and anaerobic heterotrophs related to Nitrospirae, Chloroflexi, and Thermoplasmatales. These taxa apparently played a significant role in the degradation of sinking OM. However, eDNA concentrations rapidly decreased with core depth. Despite very low sulfate concentrations, sulfate-reducing bacteria were present and viable in sediments at all three sites, as confirmed by measurement of potential sulfate reduction rates. Microbial community fingerprinting supported the presence of taxa related to Deltaproteobacteria and Firmicutes with demonstrated capacity for iron and sulfate reduction. Concomitantly, sequences of Ruminococcaceae, Clostridiales, and Methanomicrobiales indicated potential for fermentative hydrogen and methane production. Such first insights into ferruginous sediments showed that microbial populations perform successive metabolisms related to sulfur, iron, and methane. In theory, iron reduction could reoxidize reduced sulfur compounds and desorb OM from iron minerals to allow remineralization to methane. Overall, we found that biogeochemical processes in the sediments can be linked to redox differences in the bottom waters of the three sites, like oxidant

Deposition, Alteration, and Resuspension of Colorado River Delta Sediments, Lake Powell, Utah

NASA Astrophysics Data System (ADS)

Kramer, N. M.; Parnell, R.

2002-12-01

Current drought conditions in the southwest United States have resulted in lowering water levels in Lake Powell, Utah. Delta sediments forming at the Colorado River inflow for the past 39 years are becoming exposed and reworked as lake levels continue to fall to over 22 meters below full pool level. Fine sediments act as a sink for pollutants by adsorbing contaminants to their surfaces. Reworking these sediments may pose a risk to water quality in the lake. We examine whether burial and time have sufficiently altered fine sediments in the delta and affected materials adsorbed on their surfaces. Fifteen lake cores and six sediment traps were collected from the sediment delta forming at the Colorado River inflow in Lake Powell. This research characterizes fine sediment mineralogy, the composition of exchangeable materials, and organic matter content within delta sediments to determine the type and amount of alteration of these sediments with cycles of burial and resuspension. We hypothesize that as sediments are reworked, organic carbon is degraded and organic nitrogen is released forming ammonium in these reducing conditions. Sediment trap samples will be used to test this hypothesis. Trap samples will be compared to subsamples from sediment cores to determine the amount of alteration of fine sediments. All samples are analyzed for organic carbon, organic nitrogen, ammonium, cation exchange capacity, exchangeable cation composition, and clay mineralogy. Organic carbon and nitrogen are analyzed using a Leco CN analyzer. Ammonium is analyzed using a Lachet ion chromatograph. Clay mineralogy is characterized using a Siemens D500 powder X-ray diffractometer. Cation exchange capacity and exchangeable cations are measured using standard soil chemical techniques. Clay mineral analyses indicate significant spatial and temporal differences in fine sediment entering the Lake Powell delta which complicates the use of a simple deposition/alteration/resuspension model using a

An 80-year record of sediment quality in the lower Mississippi River

USGS Publications Warehouse

Van Metre, Peter C.; Horowitz, Arthur J.

2013-01-01

In 1937, the US Army Corps of Engineers cut through the "neck" of a large meander on the lower Mississippi River (below the confluence with the Ohio River) forming the Caulk Neck cutoff and creating Lake Whittington, a 26-km long oxbow lake, in northern Mississippi. Since 1938, seasonal flooding and a boat channel connecting the lake with the Mississippi River have led to sediment accumulation in the lake, resulting in an 80-year record of sediment quality in the river. On the basis of an age-dated sediment core from the lake, trends in trace metals and hydrophobic organic compounds (except polycyclic aromatic hydrocarbons) follow well-known patterns with upward trends from the 1930s to the ca 1970s, followed by downward trends to the present. Two factors contribute to these patterns: reservoir construction and changes in emissions. The construction of seven large reservoirs on the Missouri River, in particular the closure of the Fort Randall (1953) and Gavins Point (1955) Dams, greatly reduced the load of relatively clean sediment to the Mississippi River, likely contributing to downstream increases in contaminant concentrations in the Mississippi River. Increasing anthropogenic emissions also contributed to upward trends until ca 1970 when major environmental policy actions began resulting in broad decreases in emissions and downward trends in the concentrations of most of the contaminants monitored. Polycyclic aromatic hydrocarbons and phosphorus are partial exceptions to this pattern, with increases to the 1960s and variable concentrations showing no clear trend since. Published 2012. This article is a U.S. Government work and is in the public domain in the USA.

Distribution of atrazine and its phytoremediation by submerged macrophytes in lake sediments.

PubMed

Qu, Mengjie; Li, Huidong; Li, Na; Liu, Guanglong; Zhao, Jianwei; Hua, Yumei; Zhu, Duanwei

2017-02-01

We investigated sediments with high atrazine accumulation capability from 6 eutrophic lakes in Hubei Province of central China. Almost all lakes have atrazine in their sediments because of human activities. Honghu Lake and Liangzihu Lake were found to have higher levels of atrazine in sediment: 0.171 and 0.114 mg kg -1 , respectively. The results showed that lake sediments could adsorb atrazine six times faster than soils. The equilibrium partition coefficient of atrazine desorption (K Pd ) is much larger than the adsorption equilibrium partition coefficient (K Pa ) of atrazine, indicating that the residue of atrazine in water is easily immobilized by the sediments. Meanwhile, the incubation experiment showed that the removal rateof atrazine in Potamogeton crispus-planted and Myriophyllum spicatum-planted sediments reached >90%, while the rate in unplanted sediments was 77.2 ± 2.12% over 45 d. In unplanted sediment, the half-life of atrazine dissipation was 14.30 d, which was strongly enhanced by P. crispus and M. spicatum, greatly reducing the half-life to 8.60 and 9.72 d, respectively. These two submerged macrophytes are considered to be potential tools in the remediation of atrazine-contaminated sediments. Copyright © 2016 Elsevier Ltd. All rights reserved.

Sediment records of Yellow River channel migration and Holocene environmental evolution of the Hetao Plain, northern China

NASA Astrophysics Data System (ADS)

Wang, Jingzhong; Wu, Jinglu; Pan, Baotian; Jia, Hongjuan; Li, Xiao; Wei, Hao

2018-05-01

The origin and evolution of lakes in the Hetao Plain, northern China, were influenced by climate variation, channel migration, and human activity. We analyzed a suite of sediment cores from the region to investigate Yellow River channel migration and environmental change in this region over the Holocene. Short sediment cores show that environmental indicators changed markedly around CE 1850, a time that corresponds to flood events, when large amounts of river water accumulated in the western part of the Hetao Plain, giving rise to abundant small lakes. Multiple sediment variables (environmental proxies) from two long cores collected in the Tushenze Paleolake area show that sediments deposited between 12.0 and 9.0 cal ka BP were yellow clay, indicative of fluvial deposition and channel migration. From 9.0 to 7.5 cal ka BP, sand was deposited, reflecting a desert environment. From 7.5 to 2.2 cal ka BP, however, the sediments were blue-gray clay that represents lacustrine facies of Lake Tushenze, which owes its origin to an increase in strength of the East Asian monsoon. At about 2.2 cal ka BP, the north branch of the Yellow River was flooded, and the Tushenze Paleolake developed further. Around 2.0 cal ka BP, the paleolake shrank and eolian sedimentation was recorded. The analyzed sediment records are consistent with the written history from the region, which documents channel migration and environmental changes in the Hetao Plain over the Holocene.

A continuous 250,000 yr record of oxygen and carbon isotopes in ostracode and bulk-sediment carbonate from Bear Lake, Utah-Idaho

USGS Publications Warehouse

Bright, Jordon; Kaufman, D.S.; Forester, R.M.; Dean, W.E.

2006-01-01

Oxygen and carbon isotopes from a continuous, 120-m-long, carbonate-rich core from Bear Lake, Utah-Idaho, document dramatic fluctuations in the hydrologic budget of the lake over the last 250,000 yr. Isotopic analyses of bulk sediment samples capture millennial-scale variability. Ostracode calcite was analyzed from 78 levels, mainly from the upper half of the core where valves are better preserved, to compare the isotopic value of purely endogenic carbonate with the bulk sediment, which comprises both endogenic and detrital components. The long core exhibits three relatively brief intervals with abundant endogenic aragonite (50??10%) and enriched ??18O and ??13C. These intervals are interpreted as warm/dry periods when the lake retracted into a topographically closed basin. We correlate these intervals with the interglacial periods of marine oxygen-isotope stages 1, 5e, and 7a, consistent with the presently available geochronological control. During most of the time represented by the core, the lake was fresher than the modern lake, as evidenced by depleted ??18O and ??13C in bulk-sediment carbonate. ?? 2006 Elsevier Ltd. All rights reserved.

MODELLING SEDIMENT TRANSPORT FOR THE LAKE MICHIGAN MASS BALANCE PROJECT

EPA Science Inventory

A sediment transport model is one component of the overall ensemble of models being developed for the Lake Michigan Mass Balance. The SEDZL model is being applied to simulate the fine-grained sediment transport in Lake Michigan for the 1982-1983 and 1994-1995 periods. Model perf...

Holocene paleoclimatic evidence and sedimentation rates from a core in southwestern Lake Michigan

USGS Publications Warehouse

Colman, Steven M.; Jones, Glenn A.; Forester, R.M.; Foster, D.S.

1990-01-01

Preliminary results of a multidisciplinary study of cores in southwestern Lake Michigan suggest that the materials in these cores can be interpreted in terms of both isostatically and climatically induced changes in lake level. Ostracodes and mollusks are well preserved in the Holocene sediments, and they provide paleolimnologic and paleoclimatic data, as well as biogenic carbonate for stable-isotope studies and radiocarbon dating. Pollen and diatom preservation in the cores is poor, which prevents comparison with regional vegetation records. New accelerator-mass spectrometer 14C ages, from both carbon and carbonate fractions, provide basin-wide correlations and appear to resolve the longstanding problem of anomalously old ages that result from detrital organic matter in Great Lakes sediments. Several cores contain a distinct unconformity associated with the abrupt fall in lake level that occurred about 10.3 ka when the isostatically depressed North Bay outlet was uncovered by the retreating Laurentide Ice Sheet. Below the unconformity, ostracode assemblages imply deep, cold water with very low total dissolved solids (TDS), and bivalves have ?? 18O (PDB) values as light as - 10 per mil. Samples from just above the unconformity contain littoral to sublittoral ostracode species that imply warmer, higher-TDS (though still dilute) water than that inferred below the unconformity. Above this zone, another interval with ?? 18O values more negative than - 10 occurs. The isotopic data suggest that two influxes of cold, isotopically light meltwater from Laurentide ice entered the lake, one shortly before 10.3 ka and the other about 9 ka. These influxes were separated by a period during which the lake was warmer, shallower, but still very low in dissolved solids. One or both of the meltwater influxes may be related to discharge from Lake Agassiz into the Great Lakes. Sedimentation rates appear to have been constant from about 10 ka to 5 ka. Bivalve shells formed between about

Sediment radioisotope dating across a stratigraphic discontinuity in a mining-impacted lake.

PubMed

McDonald, C P; Urban, N R

2007-01-01

Application of radioisotope sediment dating models to lakes subjected to large anthropogenic sediment inputs can be problematic. As a result of copper mining activities, Torch Lake received large volumes of sediment, the characteristics of which were dramatically different from those of the native sediment. Commonly used dating models (CIC-CSR, CRS) were applied to Torch Lake, but assumptions of these methods are violated, rendering sediment geochronologies inaccurate. A modification was made to the CRS model, utilizing a distinct horizon separating mining from post-mining sediment to differentiate between two focusing regimes. (210)Pb inventories in post-mining sediment were adjusted to correspond to those in mining-era sediment, and a sediment geochronology was established and verified using independent markers in (137)Cs accumulation profiles and core X-rays.

Wind influence on the course of sedimentation processes of the laminated lacustrine sediments of Lake Czechowskie

NASA Astrophysics Data System (ADS)

Wiśniewska, Daria; Kramkowski, Mateusz; Tyszkowski, Sebastian

2016-04-01

The studies of the laminated lacustrine sediments play a very important role in the analysis of climate change. They provide valuable information related to the response of the ecosystem to changes in the environment. The condition for the development of the annual lamination is calm sedimentation, which can be compromised by the movement of water caused by waving. The depth to which this movement affects depends on the shape of the lake basin as well as the velocity and direction of the wind. During the study of sedimentary processes of laminated deposits in Lake Czechowskie (Tuchola Forest, North Poland, 53°52'N, 18°14' E, 108 m asl), the following question arose: How strong was the influence of the wind on the processes of lacustrine sedimentation? The key in getting the answers was the use of GIS techniques. Lake Czechowskie has an area of 76.6 hectares; it has two deeps separated by a threshold: a deeper one of 33 m (maximum depth of the basin) in the central-eastern part, and a shallower of 13 m in the western part. The speed of movement of water that is able to move sediment from the bottom of the lake, called the orbital wave velocity, is the basis for the designation of areas where re-suspension takes place. To calculate the wave parameters, the process of mixing, as well as the designation of re-suspension zones, the tool-script Wave Model (Rohweder et al. 2008) in the program ArsGIS 10.1 was used. The input data were wind direction and velocity from the meteorological station of Wirty about 15 km away, bathymetric data from acoustic profiling, and the Maximum Orbital Wave Velocity. The elements taken into account include maximum wind velocity of the multi-year 1996-2013, with particular emphasis on hurricanes Ksawery (December 2013) and Yoda (November 2011), during which wind velocity exceeded 120 km/h. In addition, maximum wind velocity ever recorded in the Polish Lowlands was considered. On the basis of the modelling, the authors delimited the areas

Electricity generation by anaerobic bacteria and anoxic sediments from hypersaline soda lakes

USGS Publications Warehouse

Miller, L.G.; Oremland, R.S.

2008-01-01

Anaerobic bacteria and anoxic sediments from soda lakes produced electricity in microbial fuel cells (MFCs). No electricity was generated in the absence of bacterial metabolism. Arsenate respiring bacteria isolated from moderately hypersaline Mono Lake (Bacillus selenitireducens), and salt-saturated Searles Lake, CA (strain SLAS-1) oxidized lactate using arsenate as the electron acceptor. However, these cultures grew equally well without added arsenate using the MFC anode as their electron acceptor, and in the process oxidized lactate more efficiently. The decrease in electricity generation by consumption of added alternative electron acceptors (i.e. arsenate) which competed with the anode for available electrons proved to be a useful indicator of microbial activity and hence life in the fuel cells. Shaken sediment slurries from these two lakes also generated electricity, with or without added lactate. Hydrogen added to sediment slurries was consumed but did not stimulate electricity production. Finally, electricity was generated in statically incubated "intact" sediment cores from these lakes. More power was produced in sediment from Mono Lake than from Searles Lake, however microbial fuel cells could detect low levels of metabolism operating under moderate and extreme conditions of salt stress. ?? 2008 US Government.

Preliminary Results of a Modern Watershed Study from Lake Junín, Peru: Biomarker Assemblages in Terrestrial and Aquatic Plants and Surface Sediments

NASA Astrophysics Data System (ADS)

Woods, A.; Werne, J. P.; Rodbell, D. T.; Abbott, M. B.

2016-12-01

Lake Junín is a large, evaporatively-enriched lake in the central Peruvian Andes that is ideally situated to record variability in the South American Summer Monsoon, and sediment cores recovered by the Lake Junín Deep Drilling Project in 2015 span several glacial/interglacial cycles. Compound-specific stable hydrogen isotopes from leaf waxes offer the potential to reconstruct changes in monsoon strength and evapotranspiration for the entire sediment record, and can be compared with the carbonate-derived oxygen isotope record that is preserved only during interglacials. To characterize the modern proxy system, leaf samples were collected from terrestrial and aquatic species that are representative of the vegetation in the watershed. The compound distributions, concentrations, and D/H ratios of n-alkanes and n-alkanoic acids from plants and surface sediments were analyzed to develop site-specific calibrations of both terrestrial and aquatic isotopic signals, for application to downcore biomarker analyses.

Detection gas presence in lakes bottom sediments based on seismic investigations.

NASA Astrophysics Data System (ADS)

Krylov, Pavel; Nurgaliev, Danis; Yasonov, Pavel

2017-04-01

Seismic investigations are used for various tasks, such as the study of the bottom sediments properties, finding sunken objects, reconstruction the reservoir history, etc. Detailed seismic investigation has been carried out in the southern part of Lake Bol'shoe Yarovoe (Altai Krai), Lake Sunukul (Chelyabinsk region), Lake Kisegach to map the bottom sediments and features associated with the presence of gas. The obtained results demonstrate that various types of gas can be recognized in lakes sediments, such as pockmarks, acoustic turbidity, gas flares, seeps. These features, on the one hand, prevent the reconstruction of sequence stratigraphic patterns and, on the other hand, contribute to understanding of the processes of gas formation and migration in the sediments, possible impacts of these processes on the formation of sediments enriched in the organic matter. Also, it helps to recognize these processes in the ancient sediments. The paper points out the importance of studying the formation of methane in lake sediments, because it plays an important role in the climate change. The work was carried out according to the Russia Government's Program of Competitive Growth of Kazan Federal University, supported by the grant provided to the Kazan State University for performing the state program in the field of scientific research, and partially supported by the Russian Foundation for Basic research (grant nos. 16-35-00452).

A Multiproxy Approach to Unraveling Climate and Human Demography in the Peruvian Altiplano from a 5000 year Lake Sediment Core

NASA Astrophysics Data System (ADS)

Vaught-Mijares, R. M.; Hillman, A. L.; Abbott, M. B.; Werne, J. P.; Arkush, E.

2017-12-01

Drought and flood events are thought to have shaped the ways in which Andean societies have adapted to life in the Titicaca Basin region, particularly with regard to land use practices and settlement patterns. This study examines a small lake in the region, Laguna Orurillo. Water isotopes suggest that the lake primarily loses water through evaporation, making it hydrologically sensitive. In 2015, a 3.4 m overlapping sediment record was collected and inspected for evidence of shallow water facies and erosional unconformities to reconstruct paleohydrology. Sediment core chronology was established using 7 AMS radiocarbon dates and 210Pb dating and indicates that the core spans 5000 years. Additional sediment core measurements include magnetic susceptibility, bulk density, organic/carbonate content, and XRD. Results show a pronounced change in sediment composition from brittle, angular salt deposits to massive calcareous silt and clay around 5000 years BP. Multiple transitions from clay to sand show potential lake level depressions at 1540, 2090, and 2230, yr BP that are supported by a drastic increase in carbonate composition from 2760-1600 yr BP. Additional shallow-water periods may be reflected in the presence of rip-up clasts from 4000 to 3000 yr BP. These early interpretations align well with existing hydrologic records from Lake Titicaca. In order to develop a more detailed climate and land use record, isotope analyses of authigenic carbonate minerals using δ13C and δ18O and leaf waxes using δD are being developed. Ultimately, this record will be linked with records from nearby Lagunas Arapa and Umayo. Additional proxies for human population such as fecal 5β-stanols and proximal anthropologic surveys will be synthesized to contribute to a regional understanding of Holocene climate variability and human demography in the Peruvian Altiplano.

Small ecosystem engineers as important regulators of lake's sediment respiration.

NASA Astrophysics Data System (ADS)

Baranov, Victor; Lewandowski, Joerg; Krause, Stefan; Romeijn, Paul

2016-04-01

Although shallow lakes are covering only about 1.5% of the land surface of the Earth, they are responsible for sequestration of carbon amounts similar or even larger than those sequestered in all marine sediments. One of the most important drivers of the carbon sequestration in lakes is sediment respiration. Especially in shallow lakes, bioturbation, i.e. the biogenic reworking of the sediment matrix and the transport of fluids within the sediment, severely impacts on sediment respiration. Widespread freshwater bioturbators such as chironomid larvae (Diptera, Chironomidae) are building tubes in the sediment and actively pump water through their burrows (ventilation). In the present work we study how different organism densities and temperatures (5-30°C) impact on respiration rates. In a microcosm experiment the bioreactive resazurin/resorufin smart tracer system was applied for quantifying the impacts of different densities of Chironomidae (Diptera) larvae (0, 1000, 2000 larvae/m2) on sediment respiration. Tracer transformation rates (and sediment respiration) were correlated with larval densities with highest transformation rates occurring in microcosms with highest larval densities. Respiration differences between defaunated sediment and sediment with 1000 and 2000 larvae per m2 was insignificant at 5 °C, and was progressively increasing with rising temperatures. At 30 °C respiration rates of sediment with 2000 larvae per m2 was 4.8 times higher than those of defaunated sediment. We interpret this as an effect of temperature on larval metabolic and locomotory activity. Furthermore, bacterial communities are benefiting from the combination of the high water temperatures and bioirrigation as bacterial community are able to maintain high metabolic rates due to oxygen supplied by bioirrigation. In the context of global climate change that means that chironomid ecosystem engineering activity will have a profound and increasing impact on lake sediment respiration

Combining XAS speciation and Zn isotopes to track past eutrophication in lake sediments : The example of Baldeggersee (Switzerland)

NASA Astrophysics Data System (ADS)

Noël, V. S.; Voegelin, A.; Jouvin, D.; Louvat, P.; gelabert, A.; Mueller, B.; Benedetti, M. F.; Juillot, F.

2011-12-01

Among transition elements, Zn has attracted a great deal of interest because it is an essential nutrient at low concentrations, but it can also be toxic when present at high concentrations in ecosystems (Morel et al., 2003). In the present study, the isotopic signature and crystal-chemical of Zn were followed along a sediment core from a prealpine lake that experienced a marked eutrophication in order to explore the potential of this approach at tracking past environmental conditions of continental lake-catchment systems. Lake Baldeggersee (Luzern, Switzerland) is located at an elevation of 900 m in the Swiss Prealps. It experienced a period of strong eutrophication due to intensive farming in its catchment (Lotter et al., 1997). These led to the formation of varved sediments over one century prior to artificial lake aeration (Wehrli et al., 1997). This enabled us to correlate Zn speciation and isotopic signatures to the history of the water column. Results indicate that both Zn speciation and isotopes are distinct between sediments deposited during mesotrophic and eutrophic conditions in the water column: During the mesotrophic period, sedimentation was mainly detrital and Zn is mainly found associated with clay minerals in the sediments. During the eutrophic period, sedimentation was dominated by biological activity in the lake and Zn mainly occurs as ZnS in the sediments. Zn isotopes recorded these changes in the sedimentation regime, with δ66ZnJMC values around +0.2 % for the sediments of the mesotrophic period and δ66ZnJMC values around 0 % for the sediments of the eutrophic period. Comparison with the results from a study on the seasonal variation of the isotope signature of Zn in settling sediment of another prealpine lake (Peel et al., 2010) suggests that the enrichment in light Zn isotopes in the eutrophic sediments is in line with predominant Zn input with settling biomass (algae). Since lake eutrophication is mainly related to hydrological conditions

Environmental changes and the Migration Period in northern Germany as reflected in the sediments of Lake Dudinghausen

NASA Astrophysics Data System (ADS)

Dreßler, Mirko; Selig, Uwe; Dörfler, Walter; Adler, Sven; Schubert, Hendrik; Hübener, Thomas

2006-07-01

Paleolimnological techniques were used to identify environmental changes in and around Lake Dudinghausen (northern Germany) over the past 4800 yr. Diatom-inferred total phosphorus (DI-TP) changes identify four phases of high nutrient levels (2600-2200 BC, 1050-700 BC, 500 BC-AD 100 and AD 1850-1970). During these high DI-TP phases, fossil pollen, sediment geochemistry and archaeological records indicate human activities in the lake catchment. Although the same paleo-indicators suggest increased human settlement and agriculture activity during the late Slavonic Age, the Medieval Time and the Modern Time (AD 1000-1850), DI-TP levels were low during this period. In the sediments, iron and total phosphorus were high from ˜AD 100 to 1850, likely due to increased inflow of iron-rich groundwater into the lake. Increased iron input would have lead to a simultaneous binding and precipitation of phosphate in the upper sediment and overlying water column. As a result, anthropogenic impact on Lake Dudinghausen was masked by these phosphorus-controlling processes from AD 1000 to 1850 and was not evident by means of DI-TP. In accordance with fossil pollen, sediment geochemistry and limited archaeological records, DI-TP levels were low from AD 100-1000. Groundwater levels likely rose during this period as the climate gradually changed toward colder and/or moister conditions. Such climate change likely led to reduced settlement activities and forest regeneration in the catchment area. Our results are concordant with similar studies from central Europe which indicate rapid decreasing settlement activities from AD 100 to 1000.

Methane Bubbles Transport Particles From Contaminated Sediment to a Lake Surface

NASA Astrophysics Data System (ADS)

Delwiche, K.; Hemond, H.

2017-12-01

Methane bubbling from aquatic sediments has long been known to transport carbon to the atmosphere, but new evidence presented here suggests that methane bubbles also transport particulate matter to a lake surface. This transport pathway is of particular importance in lakes with contaminated sediments, as bubble transport could increase human exposure to toxic metals. The Upper Mystic Lake in Arlington, MA has a documented history of methane bubbling and sediment contamination by arsenic and other heavy metals, and we have conducted laboratory and field studies demonstrating that methane bubbles are capable of transporting sediment particles over depths as great as 15 m in Upper Mystic Lake. Methane bubble traps were used in-situ to capture particles adhered to bubble interfaces, and to relate particle mass transport to bubble flux. Laboratory studies were conducted in a custom-made 15 m tall water column to quantify the relationship between water column height and the mass of particulate transport. We then couple this particle transport data with historical estimates of ebullition from Upper Mystic Lake to quantify the significance of bubble-mediated particle transport to heavy metal cycling within the lake. Results suggest that methane bubbles can represent a significant pathway for contaminated sediment to reach surface waters even in relatively deep water bodies. Given the frequent co-occurrence of contaminated sediments and high bubble flux rates, and the potential for human exposure to heavy metals, it will be critical to study the significance of this transport pathway for a range of sediment and contaminant types.

Town Lake bottom sediments : a chronicle of water quality changes in Austin, Texas, 1960-98

USGS Publications Warehouse

Van Metre, Peter C.; Mahler, B.J.

1999-01-01

Town Lake, the last in the chain of Highland Lakes on the Colorado River, runs through the center of Austin, Texas. On any given day, grebes and coots dot the water, rowers skim alongside, and the sparkle of the sun on the water can be admired from the adjacent hike and bike path and from the windows of nearby office buildings. During the summer months, crowds gather along the shores of Town Lake to watch as many as 1 million Mexican Free-Tail bats emerge from under the Congress Avenue bridge. But below the lazily moving azure water lies a bed of sediment about 1 meter (m) thick?sediment that has been deposited gradually since the reservoir was formed in 1959 and that has been recording changes in water quality since that time. What can this sediment tell us about the history of water quality in the Colorado River? And what does it say about the effects of the rapid urbanization of Austin and the future health of our environment?

Lake sediments provide the first eruptive history for Corbetti, a high-risk Main Ethiopian Rift volcano

NASA Astrophysics Data System (ADS)

Martin-Jones, Catherine M.; Lane, Christine S.; Pearce, Nicholas J. G.; Smith, Victoria C.; Lamb, Henry F.; Schaebitz, Frank; Viehberg, Finn; Brown, Maxwell C.; Frank, Ute; Asrat, Asfawossen

2017-04-01

A recent World Bank report found that 49 of Ethiopia's 65 known Holocene volcanoes pose a high-risk to the surrounding population. One of these volcanoes, Corbetti, located in the densely populated Main Ethiopian Rift (MER), has only one documented Holocene eruption. Any risk assessment for Corbetti is therefore highly uncertain. Reliable hazard forecasting is dependent on the completeness of volcanic records. In the case of Ethiopian Rift volcanoes complete records are hindered by frequently poorly exposed, buried and inaccessible proximal outcrops. Lake sediments can yield comprehensive, stratigraphically-resolved dossiers of past volcanism. Here we use volcanic ash (tephra) layers preserved in sediments from three MER lakes to provide the first record of Holocene volcanism for Corbetti. It shows that Corbetti has erupted explosively throughout the Holocene at an average return period of 800 years. Based on the thickness and dispersal of the tephras, at least six eruptions were of a large magnitude, and there were four eruptions in the past 2000 years. Future explosive eruptions are likely and these could have significant societal impacts, they could blanket nearby Awassa and Shashamene, home to 260,000 people, with pumice deposits. Our data indicate that the threat posed by Corbetti has been significantly underestimated. These data can be used to refine regional volcano monitoring and develop evacuation plans. This lake sediment-tephrostratigraphic approach shows significant potential for application throughout the East African Rift system, and is essential to understanding volcanic hazards in this rapidly developing region.

Environmental magnetic methods for detecting and mapping contaminated sediments in lakes

NASA Astrophysics Data System (ADS)

Boyce, J. I.

2009-05-01

The remediation of contaminated sediments is an urgent environmental priority in the Great Lakes and requires detailed mapping of impacted sediment layer thickness, areal distribution and pollutant levels. Magnetic property measurements of sediment cores from two heavily polluted basins in Lake Ontario (Hamilton Harbour, Frenchman's Bay) show that concentrations of hydrocarbons (PAH) and a number of heavy metals (Pb, As, Ni, Cu, Cr, Zn, Cd, Fe) are strongly correlated with magnetic susceptibility. The magnetic susceptibility contrast between the contaminated sediment and underlying 'pre-colonial' sediments is sufficient to generate a total field anomaly (ca. 2-20 nT) that can be measured with a magnetometer towed above the lake bed. Systematic magnetic surveying (550 line km) of Hamilton Harbour using a towed marine magnetometer clearly identifies a number of well-defined magnetic anomalies that coincide with known accumulations of contaminated lake sediment. When calibrated against in-situ magnetic property measurements, the modeled apparent susceptibility from magnetic survey results can be used to classify the relative contaminant impact levels. The results demonstrate the potential of magnetic property measurements for rapid reconnaissance mapping of large areas of bottom contamination prior to detailed coring and sediment remediation.

Organic sedimentation in modern lacustrine systems: A case study from Lake Malawi, East Africa

USGS Publications Warehouse

Ellis, Geoffrey S.; Barry J. Katz,; Christopher A. Scholz,; Peter K. Swart,

2015-01-01

This study examines the relationship between depositional environment and sedimentary organic geochemistry in Lake Malawi, East Africa, and evaluates the relative significance of the various processes that control sedimentary organic matter (OM) in lacustrine systems. Total organic carbon (TOC) concentrations in recent sediments from Lake Malawi range from 0.01 to 8.80 wt% and average 2.83 wt% for surface sediments and 2.35 wt% for shallow core sediments. Hydrogen index (HI) values as determined by Rock-Eval pyrolysis range from 0 to 756 mg HC g−1 TOC and average 205 mg HC g−1 TOC for surface sediments and 228 mg HC g−1 TOC for shallow core samples. On average, variations in primary productivity throughout the lake may account for ~33% of the TOC content in Lake Malawi sediments (as much as 1 wt% TOC), and have little or no impact on sedimentary HI values. Similarly, ~33% to 66% of the variation in TOC content in Lake Malawi sediments appears to be controlled by anoxic preservation of OM (~1–2 wt% TOC), although some component of the water depth–TOC relationship may be due to physical sediment transport processes. Furthermore, anoxic preservation has a minimal effect on HI values in Lake Malawi sediments. Dilution of OM by inorganic sediment may account for ~16% of variability in TOC content in Lake Malawi sediments (~0.5 wt% TOC). The effect of inputs of terrestrial sediment on the organic character of surface sediments in these lakes is highly variable, and appears to be more closely related to the local depositional environment than the regional flux of terrestrial OM. Total nitrogen and TOC content in surface sediments collected throughout the lake are found to be highly correlated (r2 = 0.95), indicating a well-homogenized source of OM to the lake bottom. The recurring suspension and deposition of terrestrial sediment may account for significant amounts of OM deposited in offshore regions of the lake. This process effectively separates denser

Holocene rainfall runoff in the central Ethiopian highlands and evolution of the River Nile drainage system as revealed from a sediment record from Lake Dendi

NASA Astrophysics Data System (ADS)

Wagner, Bernd; Wennrich, Volker; Viehberg, Finn; Junginger, Annett; Kolvenbach, Anne; Rethemeyer, Janet; Schaebitz, Frank; Schmiedl, Gerhard

2018-04-01

A 12 m long sediment sequence was recovered from the eastern Dendi Crater lake, located on the central Ethiopian Plateau and in the region of the Blue Nile headwaters. 24 AMS radiocarbon dates from bulk organic carbon samples indicate that the sediment sequence spans the last ca. 12 cal kyr BP. Sedimentological and geochemical data from the sediment sequence that were combined with initial diatom information show only moderate change in precipitation and catchment runoff during that period, probably due to the elevated location of the study region in the Ethiopian highlands. Less humid conditions prevailed during the Younger Dryas (YD). After the return to full humid conditions of the African Humid Period (AHP), a 2 m thick tephra layer, probably originating from an eruption of the Wenchi crater 12 km to the west of the lake, was deposited at 10.2 cal kyr BP. Subsequently, single thin horizons of high clastic matter imply that short spells of dry conditions and significantly increased rainfall, respectively, superimpose the generally humid conditions. The end of the AHP is rather gradual and precedes relatively stable and less humid conditions around 3.9 cal kyr BP. Subsequently, slightly increasing catchment runoff led to sediment redeposition, increasing nutrient supply, and highest trophic states in the lake until 1.5 cal kyr BP. A highly variable increase in clastic matter indicates fluctuating and increasing catchment runoff over the last 1500 years. The data from Lake Dendi show, in concert with other records from the Nile catchment and the Eastern Mediterranean Sea (EMS), that the Blue Nile discharge was relatively high between ca. 10.0 and 8.7 cal kyr BP. Subsequent aridification peaked with some regional differences between ca. 4.0 and 2.6 cal kyr BP. Higher discharge in the Blue Nile hydraulic regime after 2.6 cal kyr BP is probably triggered by more local increase in rainfall, which is tentatively caused by a change in the influence of the Indian Ocean

Reliance on (210)Pb chronology can compromise the inference of preindustrial Hg flux to lake sediments.

PubMed

Cooke, Colin A; Hobbs, William O; Michelutti, Neal; Wolfe, Alexander P

2010-03-15

Lake sediments are frequently used to reconstruct the rate and magnitude of human impacts on the biogeochemical cycle of mercury (Hg). The vast majority of these studies rely on excess (210)Pb inventories in short cores to temporally constrain recent trends in Hg deposition, revealing an approximately 3-fold increase in Hg deposition since preindustrial times. However, the exhaustion of unsupported (210)Pb and the onset of widespread global Hg pollution converge temporally in the late 19th century, raising the possibility that preindustrial Hg fluxes are poorly constrained. Here, we combine (210)Pb and accelerator mass spectrometry (AMS) (14)C dated lake sediment records from arctic and Andean lakes to assess the reliability of (210)Pb-derived chronologies in the estimation of preindustrial Hg fluxes. For all four studied lakes, relying on (210)Pb chronologies results in an overestimate of preindustrial Hg fluxes, because extrapolated basal (210)Pb sedimentation rates are systematically overestimated in comparison to accumulation models that include (14)C dates. In the Andes, the use of (14)C dates is critical toward assessing the full history of Hg pollution, which extends beyond the industrial era. In the Arctic, (14)C dating suggests that Hg deposition may have increased >10-fold since the Industrial Revolution, rather than the commonly quoted 3-fold increase. The incorporation of (14)C dates may therefore be necessary if accurate Hg flux histories are sought from oligotrophic lake sediments.

Temperature dependency of long-chain alkenone distributions in recent to fossil limnic sediments and in lake waters 1

NASA Astrophysics Data System (ADS)

Zink, Klaus-G.; Leythaeuser, Detlev; Melkonian, Michael; Schwark, Lorenz

2001-01-01

Distribution patterns of C 37 and C 38 polyunsaturated long-chain alkenones (LCAs) serve as proxies for the determination of paleotemperatures for marine surface waters. We studied Recent/Subrecent and Late Glacial/Holocene sediments from Germany, Austria, Russia, and the U.S. to test for a correspondence between LCA distribution and surface water temperature in limnic systems. Previously, reports of LCA occurrence were restricted to sediments of 6 wide distributed freshwater and alkaline lakes. In this study 13 of 27 investigated lakes contained LCAs in surface sediments with concentrations varying between 12 to 205 μg/g TOC. Late Glacial to Holocene sediment sequences from Lake Steisslingen and Lake Wummsee, (Germany), Lake Pichozero (Russia), and Brush Lake (U.S.A.) contained abundant LCAs with averaged concentrations of 33 to 7536 μg/g TOC. For the first time we observed the occurrence of LCAs within in the water column of oligotrophic Lake Stechlin (NE-Germany). Alkenones were restricted to the zone of maximum chlorophyll concentration within the water column indicating that LCAs have a biosynthetic origin and can be attributed to phototrophic (micro)algae. Attempts to identify the producing organism, however, were not successful. Culture experiments allow various phytoplankton to be excluded as producers. Alkenone-producing algae are evidently of small size, hindering microscopical identification. LCAs commonly occur in high concentrations in Late Glacial sediments, mainly during the cold period of the Younger Dryas, whereas the Holocene usually is devoid of polyunsaturated alkenones. The episodic occurrence of LCAs restricts their utility as proxies for continuous geological records. Furthermore, lack of microscopical verification and the episodic distribution allow for different producers of unsaturated alkenones in Recent and Late Glacial sediments. An empirical relationship between LCA distribution and temperature was observed. In fossil sediments from

Historical atmospheric pollution trends in Southeast Asia inferred from lake sediment records.

PubMed

Engels, S; Fong, L S R Z; Chen, Q; Leng, M J; McGowan, S; Idris, M; Rose, N L; Ruslan, M S; Taylor, D; Yang, H

2018-04-01

Fossil fuel combustion leads to increased levels of air pollution, which negatively affects human health as well as the environment. Documented data for Southeast Asia (SEA) show a strong increase in fossil fuel consumption since 1980, but information on coal and oil combustion before 1980 is not widely available. Spheroidal carbonaceous particles (SCPs) and heavy metals, such as mercury (Hg), are emitted as by-products of fossil fuel combustion and may accumulate in sediments following atmospheric fallout. Here we use sediment SCP and Hg records from several freshwater lentic ecosystems in SEA (Malaysia, Philippines, Singapore) to reconstruct long-term, region-wide variations in levels of these two key atmospheric pollution indicators. The age-depth models of Philippine sediment cores do not reach back far enough to date first SCP presence, but single SCP occurrences are first observed between 1925 and 1950 for a Malaysian site. Increasing SCP flux is observed at our sites from 1960 onward, although individual sites show minor differences in trends. SCP fluxes show a general decline after 2000 at each of our study sites. While the records show broadly similar temporal trends across SEA, absolute SCP fluxes differ between sites, with a record from Malaysia showing SCP fluxes that are two orders of magnitude lower than records from the Philippines. Similar trends in records from China and Japan represent the emergence of atmospheric pollution as a broadly-based inter-region environmental problem during the 20th century. Hg fluxes were relatively stable from the second half of the 20th century onward. As catchment soils are also contaminated with atmospheric Hg, future soil erosion can be expected to lead to enhanced Hg flux into surface waters. Copyright © 2018 Elsevier Ltd. All rights reserved.