Settling Fluxes and Sediment Accumulation Rates by the Combined Use of Sediment Traps and Sediment Cores in Tema Harbour (Ghana)

Abstract. Due to the lack of bioturbation, the varve-laminated muds from the oxygen minimum zone (OMZ) off Pakistan provide a unique opportunity to precisely determine the vertical and lateral sediment fluxes in the nearshore part of the northeastern Arabian Sea. West of Karachi (Hab area), the results of two sediment trap stations (EPT and WPT) were correlated with 16 short sediment cores on a depth transect crossing the OMZ. The top of a distinct, either reddish- or light-gray silt layer, 210Pb-dated as AD 1905 ± 10, was used as an isochronous stratigraphic marker bed to calculate sediment accumulation rates. In one core, the red and gray layer were separated by a few (5–10) thin laminae. According to our varve model, this contributes < 10 years to the dating uncertainty, assuming that the different layers are almost synchronous. We directly compared the accumulation rates with the flux rates from the sediment traps that collected the settling material within the water column above. All traps on the steep Makran continental slope show exceptionally high, pulsed winter fluxes of up to 5000 mg m−2 d−1. Based on core results, the flux at the seafloor amounts to 4000 mg m−2 d−1 and agrees remarkably well with the bulk winter flux of material, as well as with the flux of the individual bulk components of organic carbon, calcium carbonate and opal. However, due to the extreme mass of remobilized matter, the high winter flux events exceeded the capacity of the shallow traps. Based on our comparisons, we argue that high-flux events must occur regularly during winter within the upper OMZ off Pakistan to explain the high accumulations rates. These show distribution patterns that are a negative function of water depth and distance from the shelf. Some of the sediment fractions show marked shifts in accumulation rates near the lower boundary of the OMZ. For instance, the flux of benthic foraminifera is lowered but stable below ~1200–1300 m. However, flux and sedimentation in the upper eastern Makran area are dominated by the large amount of laterally advected fine-grained material and by the pulsed nature of the resuspension events at the upper margin during winter.

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

Geochronometria ◽

10.1515/geochr-2015-0068 ◽

2017 ◽

Vol 44 (1) ◽

pp. 142-149 ◽

Cited By ~ 1

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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Chemical composition of short sediment cores from Thermaikos Gulf (Eastern Mediterranean): Sediment accumulation rates, trawling and winnowing effects

Continental Shelf Research ◽

10.1016/j.csr.2005.08.006 ◽

2005 ◽

Vol 25 (19-20) ◽

pp. 2456-2475 ◽

Cited By ~ 25

Author(s):

A.P. Karageorgis ◽

H. Kaberi ◽

N.B. Price ◽

G.K.P. Muir ◽

J.M. Pates ◽

...

Keyword(s):

Chemical Composition ◽

Eastern Mediterranean ◽

Sediment Cores ◽

Sediment Accumulation ◽

Accumulation Rates

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Reconstructing the Rate of Accumulation of Lake Sediment: The Effect of Sediment Focusing

Quaternary Research ◽

10.1016/0033-5894(75)90015-0 ◽

1975 ◽

Vol 5 (4) ◽

pp. 541-550 ◽

Cited By ~ 146

Author(s):

John T. Lehman

Keyword(s):

Temporal Variation ◽

Lake Sediment ◽

Sediment Cores ◽

Sediment Accumulation ◽

Maximum Depth ◽

Accumulation Rates ◽

Sediment Focusing ◽

Regional History ◽

Rate Of Accumulation

Use of accumulation rates of pollen or minerals to infer regional history is complicated by nonuniform deposition of lake sediment. Sediment focusing, direction of sediment to the deepest part of a basin, can introduce a discrepancy between changes in accumulation rates measured directly from sediment cores and actual changes in influx of sediment or pollen to a lake. This difference depends on values and temporal variation of the ratio of mean depth to maximum depth in a basin as it fills. Several models of sediment accumulation show how measurements from a single core can be transformed to yield basinwide influx rates, and how the distortion due to sediment focusing can be assessed. Basins shaped like hyperboloids or frustums may introduce much greater distortions than basins conforming to ellipsoid or sinusoid shapes.

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

Mediterranean Marine Science ◽

10.12681/mms.19558 ◽

2019 ◽

Vol 20 (3) ◽

pp. 542 ◽

Cited By ~ 3

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.

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Radiocarbon Dating, Chronologic Framework, and Changes in Accumulation Rates of Holocene Estuarine Sediments from Chesapeake Bay

Quaternary Research ◽

10.1006/qres.2001.2285 ◽

2002 ◽

Vol 57 (1) ◽

pp. 58-70 ◽

Cited By ~ 67

Author(s):

Steven M. Colman ◽

Pattie C. Baucom ◽

John F. Bratton ◽

Thomas M. Cronin ◽

John P. McGeehin ◽

...

Keyword(s):

Chesapeake Bay ◽

Deep Water ◽

Sediment Cores ◽

Sediment Accumulation ◽

Complex Mixture ◽

Estuarine Sediments ◽

Accumulation Rates ◽

Pollen Stratigraphy ◽

Mass Accumulation Rates ◽

Mass Accumulation

AbstractRapidly accumulating Holocene sediments in estuaries commonly are difficult to sample and date. In Chesapeake Bay, we obtained sediment cores as much as 20 m in length and used numerous radiocarbon ages measured by accelerator mass spectrometry methods to provide the first detailed chronologies of Holocene sediment accumulation in the bay. Carbon in these sediments is a complex mixture of materials from a variety of sources. Analyses of different components of the sediments show that total organic carbon ages are largely unreliable, because much of the carbon (including coal) has been transported to the bay from upstream sources and is older than sediments in which it was deposited. Mollusk shells (clams, oysters) and foraminifera appear to give reliable results, although reworking and burrowing are potential problems. Analyses of museum specimens collected alive before atmospheric nuclear testing suggest that the standard reservoir correction for marine samples is appropriate for middle to lower Chesapeake Bay. The biogenic carbonate radiocarbon ages are compatible with 210Pb and 137Cs data and pollen stratigraphy from the same sites.Post-settlement changes in sediment transport and accumulation is an important environmental issue in many estuaries, including the Chesapeake. Our data show that large variations in sediment mass accumulation rates occur among sites. At shallow water sites, local factors seem to control changes in accumulation rates with time. Our two relatively deep-water sites in the axial channel of the bay have different long-term average accumulation rates, but the history of sediment accumulation at these sites appears to reflect overall conditions in the bay. Mass accumulation rates at the two deep-water sites rapidly increased by about fourfold coincident with widespread land clearance for agriculture in the Chesapeake watershed.

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Comparative 210Pb, 137Cs, and Pollen Geochronologies of Sediments from Lakes Ontario and Erie

Quaternary Research ◽

10.1016/0033-5894(78)90105-9 ◽

1978 ◽

Vol 10 (2) ◽

pp. 256-278 ◽

Cited By ~ 124

Author(s):

J.A. Robbins ◽

D.N. Edgington ◽

A.L.W. Kemp

Keyword(s):

Lake Erie ◽

Sediment Cores ◽

Sediment Accumulation ◽

Radioactive Decay ◽

Storm Surges ◽

Accumulation Rates ◽

Near Surface ◽

Western Lake ◽

Physical Mixing ◽

Regional Forest

The distribution of 210Pb, 137Cs, and Ambrosia (ragweed) pollen in two sediment cores from Lake Ontario and in three cores from Lake Erie provides independent estimates of sediment accumulation rates. Geochronology with 210Pb is based on radioactive decay of the isotope following burial in sediments. The method can reveal with precision changes in sedimentation occurring over the past 100 yr or so. Geochronologies with 137Cs and Ambrosia are based on the occurrence of a horizon corresponding, respectively, to the onset of nuclear testing 25 yr ago and to regional forest clearance in the middle 1800s. These methods provide estimates of long-term average sediment accumulation rates. In all but one core, the distributions of 137Cs and 210Pb indicate no physical mixing of near-surface sediments. In two cores, including one from central Lake Erie collected by diver, all three estimates of sedimentation rates are in excellent agreement. In two other cores, rates based on 210Pb are significantly higher than those inferred from Ambrosia pollen profiles. Lower average rates appear to result from occasional massive losses of sediments. Such events, apparent in the distribution of 210Pb but not in pollen records, correlate with the occurrence of major storm surges on the lakes during this century. In one core from western Lake Erie, exponential distributions of both 210Pb and Ambrosia appear to be artifacts which may result from extensive biological or physical reworking of sediments in shallow water (11 m). Previous indications of increased sedimentation in Lake Erie since about 1935 based on Castanea (chestnut) pollen data are not substantiated.

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Patterns and mechanisms of fluvial sediment flux and accumulation in two subarctic fjords: Nachvak and Saglek Fjords, Nunatsiavut, Canada

Canadian Journal of Earth Sciences ◽

10.1139/e2012-052 ◽

2012 ◽

Vol 49 (10) ◽

pp. 1200-1215 ◽

Cited By ~ 8

Author(s):

Samuel J. Bentley ◽

Elisabeth Kahlmeyer

Keyword(s):

Sediment Accumulation ◽

Suspended Sediments ◽

Sediment Traps ◽

Extensive Study ◽

Sediment Flux ◽

Small Rivers ◽

Recent Sediment ◽

Accumulation Rates ◽

Natural Sediment ◽

Fluvial Sediment

Recent marine sedimentary deposits and river discharge in two subarctic fjords in Nunatsiavut (Northern Labrador, Canada) have been studied to elucidate patterns and mechanisms of fluvial sediment transfer and accumulation in the fjords, to further our understanding of the longer-term sedimentary record. Multibeam and sub-bottom acoustic data and sediment cores were collected in Nachvak and Saglek fjords, within Canada’s Torngat Mountains National Park, as part of the most extensive study of the park’s marine resources to date. Cores were subsampled for X-radiography, grain size, and 210Pb/137Cs geochronology. Muddy basin sediments within each fjord are bioturbated, indicating circulation of oxygenated bottom water. Depositional fluxes and inventories of 210Pb indicate efficient marine scavenging of 210Pb by fine suspended sediments. In Nachvak Fjord, with small rivers and steep, presently glaciated catchments, postglacial and recent sediment accumulation rates are similar, implying relatively constant sedimentation over time. In Saglek Fjord, fed by larger rivers with more extensive catchments that lack glaciers, recent sediment accumulation is more rapid than that averaged over postglacial time. Present mass accumulation rates for the Nachvak Fjord basin are on average 39 000 t·year–1 for the entire basin, and for Saglek 43 000 t·year–1 for the entire basin, with sediment-gravity flows being one likely mechanism for sediment delivery to deep basins. Results collectively suggest that both marine basins are excellent natural sediment traps. Comparison of accumulation rates from 137Cs and 210Pb suggest that sediment fluxes to Nachvak Fjord may have decreased slightly over the past ∼130 years.

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Recent trends in sediment and nutrient accumulation rates in coastal, freshwater Lake Sibaya, South Africa

Marine and Freshwater Research ◽

10.1071/mf12313 ◽

2013 ◽

Vol 64 (11) ◽

pp. 1087 ◽

Cited By ~ 3

Author(s):

Marc S. Humphries ◽

Claudia R. Benitez-Nelson

Keyword(s):

South Africa ◽

Sediment Cores ◽

Sediment Accumulation ◽

Freshwater Lake ◽

Total Carbon ◽

Nutrient Concentrations ◽

Bulk Sediment ◽

Accumulation Rates ◽

Nitrogen And Phosphorus ◽

Recent Trends

Eutrophication of aquatic systems has emerged as one of the most pressing issues confronted by scientists and environmental managers. In this study, we used two sediment cores from Lake Sibaya, a coastal freshwater lake in South Africa, to infer historical variations in bulk sediment accumulation and nutrient (C, N and P) biogeochemistry. Cores were dated using 210Pb, 137Cs and 14C, and dates were used to calculate bulk sediment accumulation rates and nutrient concentrations over the last 250 years. In the western section of the lake, stratigraphic variations in total carbon, nitrogen and phosphorus increased abruptly to near-constant levels around the beginning of the 20th century, a trend that appears to be consistent with the onset of human settlement and land clearance in the catchment. In contrast, sedimentation rates have remained relatively constant over this period, despite recent land use change in the catchment. Results of this study suggest that recent increases in development pressure have yet to further influence sedimentation in Lake Sibaya, thus providing values against which future monitoring efforts can be compared. This study represents the first report on recent trends in sedimentation and nutrient biogeochemistry in Lake Sibaya. The results have broad implications for other ecologically sensitive areas within the Maputaland ecoregion of coastal southern Africa.

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