A Test of Lead-210 Dating for the Measurement of Whole Lake Soft Sediment Accumulation

1983 ◽  
Vol 40 (4) ◽  
pp. 506-515 ◽  
Author(s):  
R. Douglas Evans ◽  
Frank H. Rigler
Keyword(s):  
Lake Sediment ◽  
Accumulation Rate ◽  
Sediment Accumulation ◽  
Soft Sediment ◽  
Lake Morphometry ◽  
Southern Ontario ◽  
Lake Bottom ◽  
Lead 210 ◽  
Shield Lakes ◽  
The Relationship

We have tested the hypothesis that variation in accumulation of soft sediments over a lake bottom is related to the lake morphometry, allowing an accurate measurement of whole lake sediment accumulation. In each of two Laurentian Shield lakes in southern Ontario, sediment accumulation was measured at ~20 locations. In both there was a statistically significant linear relationship between soft sediment accumulation and the water depth at the sample locations. The relationship explained 72 and 57% of sediment accumulation variation in Costello and Red Chalk lakes, respectively. Using these relationships, it was possible to calculate the whole lake sediment accumulation rate for each lake. The results indicate that, in general, there is a linear variation in sediment accumulation as a function of depth in small Shield lakes. This study points out the need for a closer examination of sediment movement and accumulation in the shallow regions of lakes.

Late Quaternary vegetation dynamics and hydroseral development in a Thuja occidentalis swamp in southern Ontario

1996 ◽  
Vol 33 (10) ◽  
pp. 1439-1456 ◽  
Author(s):  
M. Jane Bunting ◽  
Barry G. Warner ◽  
Ramon Aravena
Keyword(s):  
Vegetation Dynamics ◽  
Accumulation Rate ◽  
Late Quaternary ◽  
Sediment Accumulation ◽  
Open Water ◽  
Internal Factors ◽  
Southern Ontario ◽  
Thuja Occidentalis ◽  
Open Water Body ◽  
Water Community

Palaeoecological data from a small swamp in southern Ontario are used to reconstruct postglacial upland and wetland vegetation dynamics and assess the relative importance of autogenic and allogenic factors in wetland development. The inferred upland forest dynamics are comparable in timing and trend with lake records from the region. During the early Holocene, the shallow open water body became increasingly colonized by aquatic plants, until at around 8000 BP when the shallow open water community was replaced by a Larix swamp. At around 5600 BP, there was an apparent reversal in the wetland progression and Typha was locally dominant. There is a possible hiatus in the sedimentary record at around this time. Thereafter, a Thuj–Abies–Picea swamp community developed. The data suggest that internal factors and local events such as beaver activity could be equally or more important than regionally acting factors such as climatic change in controlling the hydroseral progression. The changing nature of the wetland community led to a 40-fold variation in sediment accumulation rate during the Holocene, emphasizing the importance of establishing a good chronology and using a multiple-core approach in such systems.

Pigment Preservation in Lake Sediments: A Comparison of Sedimentary Environments in Trout Lake, Wisconsin

1991 ◽  
Vol 48 (3) ◽  
pp. 472-486 ◽  
Author(s):  
James P. Hurley ◽  
David E. Armstrong
Keyword(s):  
Accumulation Rate ◽  
Sediment Cores ◽  
Sediment Accumulation ◽  
Sediment Surface ◽  
Water Interface ◽  
Sedimentary Pigments ◽  
Sedimentary Environments ◽  
Trout Lake ◽  
Secondary Carotenoids ◽  
Β Carotene

Fluxes and concentrations of a phorbins and major algal carotenoids were quantified in sediment trap material and sediment cores from two basins of Trout Lake, Wisconsin (TrDH and TrAB). The basins were chosen to contrast the influence of oxygen content at the sediment–water interface (TrDH, oxic and TrAB, reducing), sediment accumulation rate, and focusing. Pigment diagenesis occurred in both basins, but transformations and destruction were more extensive in TrDH. Although untransformed chlorophyll a was the major phorbin deposited at the sediment surface of both basins (51–64 mol%), pigment destruction, coupled with transition to pheophytin, accounted for substantial losses, especially in oxic TrDH sediments. Fucoxanthin, peridinin, and diadinoxanthin, despite representing > 70% of the deposited carotenoid flux, were substantially degraded or transformed in both basins. However, preservation was relatively high for secondary carotenoids, such as diatoxanthin and β-carotene, and for a major cryptomonad pigment, alloxanthin. Residual profiles in sediments show that pigment sedimentation from the epilimnion and accumulation in the permanent sediments are not directly related and that diagenesis must be considered in interpreting sedimentary pigments.

Crustacean zooplankton species richness: single- and multiple-year estimates

1998 ◽  
Vol 55 (7) ◽  
pp. 1573-1582 ◽  
Author(s):  
Shelley E Arnott ◽  
John J Magnuson ◽  
Norman D Yan
Keyword(s):  
Spatial Scales ◽  
Species Pool ◽  
Crustacean Zooplankton ◽  
Zooplankton Species ◽  
Asymptotic Approach ◽  
Sampling Programme ◽  
Temporal And Spatial ◽  
Shield Lakes ◽  
The Relationship ◽  
Temporal Extent

Richness estimates are dependent on the spatial and temporal extent of the sampling programme and the method used to predict richness. We assessed crustacean zooplankton richness in eight Canadian Shield lakes at different temporal and spatial scales using three methods of estimation: cumulative, asymptotic, and Chao's index. Percent species detected increased with the number of spatial, intraannual, or interannual samples taken. Single samples detected 50% of the annual species pool and 33% of the total estimated species pool. This suggests that previous estimates of zooplankton richness, based on single samples in individual lakes, are too low. Our richness estimates for individual lakes approach the total number of zooplankton found in some regions of Canada, suggesting that each lake has most taxa at some time, the majority being very rare. Single-year richness estimates provided poor predictions of multiple-year richness. The relationship between richness and environmental variables was dependent on the method of estimation and the number of samples used. We conclude that richness should be treated as an "index" rather than an absolute and sampling efforts should be standardized. We recommend an asymptotic approach to estimate zooplankton richness because the number of samples taken influenced it less.

scholarly journals SEAMUS (v1.0): a Δ<sup>14</sup>C-enabled, single-specimen sediment accumulation simulator

2019 ◽  
Author(s):  
Bryan C. Lougheed
Keyword(s):  
Sediment Core ◽  
Accumulation Rate ◽  
Sediment Accumulation ◽  
Species Abundance ◽  
Depth Interval ◽  
Single Specimen ◽  
14C Dating ◽  
Deep Sea Sediment ◽  
Wide Range ◽  
History Of

Abstract. The systematic bioturbation of single particles (such as foraminifera) within deep-sea sediment archives leads to the apparent smoothing of any temporal signal as record by the downcore, discrete-depth mean signal. This smoothing is the result of the systematic mixing of particles from a wide range of depositional ages into the same discrete depth interval. Previous sediment models that simulate bioturbation have specifically produced an output in the form of a downcore, discrete-depth mean signal. Palaeoceanographers analysing the distribution of single foraminifera specimens from sediment core intervals would be assisted by a model that specifically evaluates the effect of bioturbation upon single specimen populations. Taking advantage of recent increases in computer memory, the single-specimen SEdiment AccuMUlation Simulator (SEAMUS) was created in Matlab, whereby large arrays of single specimens are simulated. This simulation allows researchers to analyse the post-bioturbation age heterogeneity of single specimens contained within discrete-depth sediment core intervals, and how this heterogeneity is influenced by changes in sediment accumulation rate (SAR), bioturbation depth (BD) and species abundance. The simulation also assigns a realistic 14C activity to each specimen, by considering the dynamic Δ14C history of the Earth and temporal changes in reservoir age. This approach allows for the quantification of possible significant artefacts arising when 14C dating multi-specimen samples with heterogeneous 14C activity. Users may also assign additional desired carrier signals to specimens (e.g., stable isotopes, trace elements, temperature, etc.) and consider a second species with an independent abundance. Finally, the model can simulate a virtual palaeoceanographer by randomly picking whole specimens (whereby the user can set the percentage of older, broken specimens) of a prescribed sample size from discrete depths, after which virtual laboratory 14C dating and 14C calibration is carried out within the model.

scholarly journals High-resolution magnetostratigraphy of the upper Nacimiento Formation, San Juan Basin, New Mexico, USA: implications for basin evolution and mammalian turnover

2017 ◽  
Author(s):  
Caitlin Leslie ◽  
Daniel J. Peppe ◽  
Thomas E. Williamson ◽  
Dario Bilardello ◽  
Matthew Heizler ◽  
...  
Keyword(s):  
New Mexico ◽  
North America ◽  
Accumulation Rate ◽  
Global Climate ◽  
Sediment Accumulation ◽  
San Juan ◽  
Accumulation Rates ◽  
Fluvial System ◽  
San Juan Basin ◽  
Geomagnetic Polarity

Lower Paleocene deposits in the San Juan Basin document one of the best records of mammalian change and turnover following the Cretaceous-Paleogene extinctions and are the type section for the Puercan (Pu) and Torrejonian (To) North America Land Mammal age biozones (NALMA). One of the largest mammalian turnover events in the early Paleocene occurs between the Torrejonian 2 (To2) and Torrejonian 3 (To3) NALMA biozones. The Nacimiento Formation are the only deposits in North America where the To2-To3 mammalian turnover can be constrained, however the precise age and duration of the turnover is poorly understood due to the lack of a precise chronostratigraphic framework. We analyzed paleomagnetic samples, produced a 40Ar/39Ar detrital sanidine age, and developed a detailed lithostratigraphy for four sections of the upper Nacimiento Formation in the San Juan Basin, New Mexico (Kutz Canyon, Escavada Wash, Torreon West and East) to constrain the age and duration of the deposits and the To2-To3 turnover. The polarity stratigraphy for the four sections can be correlated to chrons C27r-C26r of the geomagnetic polarity time scale (GPTS). Using the local polarity stratigraphy for each section, we calculated a mean sediment accumulation rate and developed a precise age model, which allows us to determine the age of important late Torrejonian mammalian localities. Using the assigned ages, we estimate the To2-To3 turnover was relatively rapid and occurred over ~120 kyr (-60/+50 kyr) between 62.59 and 62.47 Ma. This rapid duration of the mammalian turnover suggests that it was driven by external forcing factors, such as environmental change driven by the progradation of the distributive fluvial system across the basin and/or changes in regional or global climate. Additionally, comparisons of the mean sediment accumulation rates between the sections that span from the basin margin to the basin center indicate that sediment accumulation rates equalized across the basin from the end of C27r through the start of C26r, suggesting an accommodation minima in the basin associated with the progradation of a distributive fluvial system into the basin. This accommodation minimum also likely led to the long hiatus of deposition between the Paleocene Nacimiento Formation and the overlying Eocene San Jose Formation.

Distribution of biogenic silica in the surficial sediments of Lake Michigan

1986 ◽  
Vol 23 (9) ◽  
pp. 1442-1449 ◽  
Author(s):  
Daniel J. Conley ◽  
Claire L. Schelske ◽  
Brian G. Dempsey ◽  
Charles D. Campbell ◽  
Teresa L. Newberry
Keyword(s):  
Spatial Distribution ◽  
Biogenic Silica ◽  
Lake Michigan ◽  
Sediment Accumulation ◽  
Sedimentation Rates ◽  
Surficial Sediments ◽  
Sediment Samples ◽  
High Productivity ◽  
Lake Bottom ◽  
High Concentrations

The spatial distribution of biogenic silica (BSi) in the surficial sediments of Lake Michigan is described from Shipek grab samples collected in 1975 and gravity cores obtained in 1983. Significantly smaller surficial BSi concentrations in the 1975 samples were attributed primarily to the inability of a Shipek grab to collect intact surficial sediment samples. Lower concentrations o.f BSi were found in nondepositional and transitional areas of sediment accumulation than in depositional basins. Therefore, BSi accumulation is restricted primarily to the 40% of the lake bottom where sediments are presently accumulating. High concentrations found in Green Bay surficial sediments are related to high productivity in the bay coupled with inputs of new silica from the Fox River. In the open lake, BSi concentrations of surficial sediments in depositional basins appeared to vary inversely with sedimentation rate in that lower BSi concentrations were found in areas with higher sedimentation rates.

scholarly journals 240+239Pu depositional signatures as a viable geochronological tool in the Amazon Basin

2017 ◽  
Vol 44 (1) ◽  
pp. 142-149 ◽  
Author(s):  
Luciana M Sanders ◽  
Kathryn H Taffs ◽  
Debra Stokes ◽  
Alex Enrich-Prast ◽  
Christian J Sanders
Keyword(s):  
Amazon Basin ◽  
Environmental Science ◽  
Sediment Cores ◽  
Sediment Accumulation ◽  
Recent Sediment ◽  
Floodplain Lake ◽  
Accumulation Rates ◽  
Amazon Floodplain ◽  
Dating Methods ◽  
Lead 210

AbstractAnthropogenic radionuclide signatures associated with nuclear testing are increasingly utilized in environmental science to explore recent sedimentation. In this study, we assess the suitability of Pu radioisotope analysis in floodplain lake environments in the Amazon Basin to form geochronologies during the 20thcentury. The240Pu +239Pu (240+239Pu) signatures in six sediment cores indicate sediment accumulation rates in the floodplain lakes of the major rivers; Amazon (2.3 mm year-1), Tapajos (10.2 and 2.4 mm year-1) and Madeira (3.4, 4.2 and 6.2 mm year-1). The results from this study show that240+239Pu fallout activities, and the well documented (240Pu/239Pu) atomic ratios of the above ground nuclear tests which began in the 1950’s, are sufficient and well preserved in Amazon floodplain lake sediments to infer chronologies. Lead-210 dating analyses in the same sediment cores produced comparable sediment accumulation rates at three of the six sites. The differences between dating methods may be attributed to the different time scale these dating methods represent and/or in the solubility between Pb and Pu along the sediment column. The geochronologies derived from the240+239Pu and210Pb dating methods outlined in this work are of interest to identify the effects of changing sediment accumulation rates during the previous century as a result of development, including deforestation, along the Amazon Basin which increased towards the middle of the 20thcentury. This study shows that Pu dating provides a viable alternative geochronology tool for recent sediment accumulation (previous ~60 years) along the Amazon Basin.

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