scholarly journals Evaluating the historical sedimentation patterns in two different Mediterranean deep environments (Sardinia and Sicily Channels)

2019 ◽  
Vol 20 (3) ◽  
pp. 542 ◽  
Author(s):  
NOUR EL HOUDA HASSEN ◽  
NAFAÂ REGUIGUI ◽  
MOHAMED AMINE HELALI ◽  
NEZHA MEJJAD ◽  
ABDELMOURHIT LAISSAOUI ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Water Depth ◽  
Accumulation Rate ◽  
Sediment Cores ◽  
Sediment Accumulation ◽  
Inverse Correlation ◽  
Accumulation Rates ◽  
Deep Sediment ◽  
210Pb And 137Cs ◽  
Excess 210Pb

The sediment accumulation rate in the Sardinia and Sicily channels in the central part of the Mediterranean Sea was studied by using short-lived radionuclides (210Pb and 137Cs) in two deep sediment cores. Different sedimentation regimes were identified indicating substantial differences in accumulation rates and historical patterns. The 210Pb-derived mean accumulation rate found in the Strait of Sardinia was 0.05 g.cm-2.y-1, lower than that in Sicily Channel (0.1 g.cm-2.y-1) suggesting an inverse correlation with water depth. Excess 210Pb inventories were 24 ± 1 and 6.0 ± 0.4 kBq.m-2, while the fluxes to the sediment were 745 ± 31 and 188 ± 11 Bq.m-2.y-1 in Sicily and Sardinia channels, respectively. 137Cs failed to use for the validation of the established chronologies, while its inventories found 450 Bq.m-2 and 355 Bq.m-2 in the Sicily and Sardinia channel, respectively.

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.

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.

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.

Global wind-induced change of deep-sea sediment budgets, new ocean production and CO 2 reservoirs ca . 3.3-2.35 Ma BP

1988 ◽  
Vol 318 (1191) ◽  
pp. 487-504 ◽  
Keyword(s):  
Large Scale ◽  
Accumulation Rate ◽  
Sediment Accumulation ◽  
Distribution Patterns ◽  
Trade Wind ◽  
Accumulation Rates ◽  
Deep Sea Sediment ◽  
Late Pliocene ◽  
High Productivity ◽  
Sediment Fraction

The late Pliocene phase of large-scale climatic deterioration about 3.2-2.4 Ma BP is well documented in a number of (benthic) δ 18 O records. To test the global implications of this event, we have mapped the distribution patterns of various sediment variables in the Pacific and Atlantic Oceans during two time slices, 3.4-3.18 and 2.43-2.33 Ma BP. The changes of bulk sedimentation and bulk sediment accumulation rates are largely explained by the variations of CaCO 3 -accumulation rates (and the accumulation rates of the complementary siliciclastic sediment fraction near continents in higher latitudes). During the late Pliocene, the CaCO 3 -accumulation rate increased along the equatorial Pacific and Atlantic and in the northeastern Atlantic, but decreased elsewhere. The accumulation rate of organic carbon (C org ) and net palaeoproductivity also increased below the high-productivity belts along the equator and the eastern continental margins. From these patterns we may conclude that (trade-) wind- induced upwelling zones and upwelling productivity were much enhanced during that time. This change led to an increased transfer of CO 2 from the surface ocean to the ocean deep water and to a reduction of evaporation, which resulted in an aridification of the Saharan desert belt as depicted in the dust sediments off northwest Africa.

scholarly journals Sediment geochronology and spatio-temporal and vertical distributions of radionuclides in the Upper Bonny Estuary (South Nigeria)

2014 ◽  
Vol 41 (4) ◽  
pp. 369-376 ◽  
Author(s):  
Omorotionmwan Omokheyeke ◽  
Francis Sikoki ◽  
Abdelmourhit Laissaoui ◽  
David Akpuluma ◽  
Peter Onyagbodor ◽  
...  
Keyword(s):  
Sediment Cores ◽  
Sediment Accumulation ◽  
Dry Weight ◽  
Radiometric Dating ◽  
Layer By Layer ◽  
Excess 210Pb ◽  
Radio Nuclide ◽  
Vertical Distributions ◽  
Southwest Nigeria ◽  
Spatio Temporal

Abstract Surface deposits and sediment cores were collected from the Upper Bonny Estuary, located in Southwest Nigeria, and analyzed to determine spatio-temporal and vertical distributions of radio-nuclide activities expressed in Bq·kg−1 dry weight. The results of activities of naturally occurring radionuclides of 226Ra (15 ± 2–34 ± 3 Bq·kg−1), 228Ra (32 ± 5–48 ± 6 Bq·kg−1), 40K (264 ± 29–462 ± 36 Bq·kg−1) were found to be all within the range of typical values reported for coastal regions. Ratios of 226Ra to 228Ra suggested accretion for all samples with low sediment accumulation registered during rainy months. In addition, vertical distributions at the three sampling sites were also studied with the initial aim of establishing chronologies from the decay of excess 210Pb. In two cores, excess 210Pb, estimated by subtracting 226Ra from total 210Pb on a layer-by-layer basis, exhibit relatively constant activity with discrete minima and maxima. Therefore, these cores were excluded from radiometric dating. Only the third core could be dated by the constant rate of supply model, and 137Cs was utilized to validate the 210Pb chronology.

Time averaging and stratigraphic unmixing: reconstructing ecological decline in molluscan production (Holocene, Brijuni, NE Adriatic)

2020 ◽  
Author(s):  
Adam Tomašových ◽  
Martin Zuschin ◽  
Ivo Gallmetzer ◽  
Alexandra Haselmair
Keyword(s):  
Accumulation Rate ◽  
Sediment Cores ◽  
Sediment Accumulation ◽  
Coralline Algae ◽  
Time Averaging ◽  
Sedimentation Rates ◽  
Amino Acid Racemization ◽  
Ecological History ◽  
Shell Bed ◽  
Warm Temperate

<p>The northeastern Adriatic seafloor is formed by warm-temperate bioclastic carbonates with coralline algae, bryozoans and mollusks. These sediments represent a mixture of past and present-day production owing to low sedimentation rates and bioturbation. Although low sedimentation rates do not allow resolution of ecological history at centennial or even millennial scales on the basis of raw stratigraphic data, age unmixing based on radiocarbon-calibrated amino acid racemization shows that one of the major molluscan sediment producers – the infaunal suspension-feeder Timoclea ovata  – markedly peaked in production ~5,000 years during the maximum flooding and earliest highstand phase and significantly diminished in abundance during the late highstand phase at Brijuni, with a large proportion of dead shells now present in surface sediments representing shells that are several centuries old. This species still occurs in living assemblages but our analyses indicate that its former production was by several orders of magnitude higher. In contrast, stratigraphic trends in absolute and proportional abundance of this species in ~1.5 m-thick sediment cores show a gradual or a very mild upcore decline, indicating that raw stratigraphic data do not efficiently detect millennial-scale ecological dynamic. The temporal decline in production of Timoclea ovata is associated with an increase in water depth and an increase in sediment-accumulation rate, and led to a transition from molluscan oyster-scallop shell bed to late highstand bryomol sediments.</p>

Sedimentological and limnological evolution of recreational lakes in a former asbestos mining region (Québec, Canada): insights from paleolimnology

2020 ◽  
Author(s):  
Reinhard Pienitz ◽  
Olivier Jacques
Keyword(s):  
Accumulation Rate ◽  
Sediment Cores ◽  
Sediment Accumulation ◽  
Ecological Condition ◽  
Nutrient Concentrations ◽  
Mineral Matter ◽  
Mining Activities ◽  
Fine Grained ◽  
Efficient Management ◽  
A Chain

<p>The Bécancour River basin in southern Québec (Canada) has been impacted by more than a hundred years of asbestos mining activities in the Thetford Mines region. Several recreational water bodies located downstream from the city are suffering from high sediment and contaminant loads and eutrophication. In order to prepare an efficient management of the fluvial lakes, we completed paleolimnological investigations to evaluate the extent of their deterioration and identify catchment disturbances that influenced their present-day condition. Here we present the results of a multi-proxy study of sediment cores collected from a chain of 5 lakes. The sedimentary records from these lakes indicate severe perturbations associated with the complete draining of Lac Noir, a former lake near Thetford Mines excavated and drained for mining purposes between 1955-1959. Radiometric <sup>210</sup>Pb dating revealed extreme increases in the sediment accumulation rate following this event. Analyses of loss-on-ignition, carbon (C) and nitrogen (N) isotopes, grain-size, and X-ray microfluorescence indicated that the post-1960 sediments were enriched in fine-grained mineral matter and had higher metal and nutrient concentrations as compared to older sediments at the bottom of the cores. Changes in the δ<sup>13</sup>C and C/N ratios and the predominance of diatom taxa (class Bacillariophyceae) typical of nutrient-rich waters (e.g., Cyclostephanos invisitatus, Cyclotella meneghiniana) also showed that the 1955-1959 event led to a rapid eutrophication of some lakes. Results from our study illustrate that the asbestos mining activities had dramatic impacts on lake biota and contaminant levels, and suggest that major restoration efforts will be needed to improve their ecological condition.</p>

Sign in / Sign up

Export Citation Format

Share Document