Paleomagnetic Constraints on Sedimentation Rates in the Eastern Arctic Ocean

1996 ◽  
Vol 46 (1) ◽  
pp. 62-71 ◽  
Author(s):  
David A. Schneider ◽  
Jan Backman ◽  
William B. Curry ◽  
Göran Possnert
Keyword(s):  
Arctic Ocean ◽  
Sediment Cores ◽  
Sediment Accumulation ◽  
Ocean Basin ◽  
Canada Basin ◽  
Sedimentation Rates ◽  
Carbonate Concentration ◽  
Order Of Magnitude ◽  
Diverse Data

Deep-sea sediments recovered from six sites visited during the International Arctic Ocean Expedition of 1991 were examined to determine sedimentation rates in the eastern Arctic Ocean basin. The dearth of age-diagnostic biogenic material in these sediments precludes the application of biostratigraphic methods, but ages can be deduced using paleomagnetism, in conjunction with measurements of radiocarbon and carbonate concentration. Although no one of these techniques gives an unambiguous determination of age, the interpretation most consistent with these diverse data implies that sedimentation rates in the eastern Arctic are, in general, a few centimeters per thousand years. Such estimates of sedimentation rate are an order of magnitude greater than those previously determined from many sediment cores taken from the Canada Basin. However, one site examined on the Morris Jesup Rise shows a relatively low rate of sediment accumulation (less than 0.6 cm/103 yr) suggesting that, although higher than in the Canada Basin, sedimentation rates in the eastern Arctic can be highly variable.

Testing the synchronicity of Pleistocene biostratigraphic events in the central Arctic – Do we have a consistent biostratigraphic framework?  

2021 ◽  
Author(s):  
Flor Vermassen ◽  
Helen K. Coxall ◽  
Gabriel West ◽  
Matt O'Regan
Keyword(s):  
Arctic Ocean ◽  
Sediment Cores ◽  
Age Determination ◽  
The Arctic ◽  
Calcareous Nannofossils ◽  
Central Arctic Ocean ◽  
Eurasian Basin ◽  
Future Work ◽  
Amerasian Basin

<p>Harsh environmental and taphonomic conditions in the central Arctic Ocean make age-modelling for Quaternary palaeoclimate reconstructions challenging. Pleistocene age models in the Arctic have relied heavily on cyclostratigraphy using lithologic variability tied to relatively poorly calibrated foraminifera biostratigraphic events. Recently, the identification of <em>Pseudoemiliania lacunosa</em> in a sediment core from the Lomonosov Ridge, a coccolithophore that went extinct during marine isotope stage (MIS) 12 (478-424 ka), has been used to delineate glacial-interglacial units back to MIS 14 (~500 ka BP). Here we present a comparative study on how this nannofossil biostratigraphy fits with existing foraminifer biohorizons that are recognised in central Arctic Ocean sediments. A new core from the Alpha Ridge is presented, together with its lithologic variability and down-core compositional changes in planktonic and benthic foraminifera. The core exhibits an interval dominated by <em>Turborotalita egelida</em>, a planktonic foraminifer that is increasingly being adopted as a marker for MIS11 in sediment cores from the Amerasian Basin of the Arctic Ocean. We show that the new age-constraints provided by calcareous nannofossils are difficult to reconcile with the proposed MIS 11 age for the <em>T. egelida</em> horizon. Instead, the emerging litho- and coccolith biostratigraphy implies that Amerasian Basin sediments predating MIS5 are older than the egelida-based age models suggest, i.e. that the <em>T. egelida</em> Zone is older than MIS11. These results expose uncertainties regarding the age determination of glacial-interglacial cycles in the Amerasian basin and point out that future work is required to reconcile the micro- and nannofossil biostratigraphy of the Amerasian and Eurasian basin.</p>

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>

Determination of particulate organic carbon sources to the surface mixed layer of the Canada Basin, Arctic Ocean

2014 ◽  
Vol 119 (2) ◽  
pp. 1084-1102 ◽  
Author(s):  
Kristina A. Brown ◽  
Fiona McLaughlin ◽  
Philippe D. Tortell ◽  
Diana E. Varela ◽  
Michiyo Yamamoto-Kawai ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Arctic Ocean ◽  
Particulate Organic Carbon ◽  
Mixed Layer ◽  
Carbon Sources ◽  
Canada Basin ◽  
Surface Mixed Layer ◽  
Organic Carbon Sources

Holocene sedimentation in glacial Tasikutaaq Lake, Baffin Island

1988 ◽  
Vol 25 (6) ◽  
pp. 810-823 ◽  
Author(s):  
Donald S. Lemmen ◽  
Robert Gilbert ◽  
John P. Smol ◽  
Roland I. Hall
Keyword(s):  
Drainage Basin ◽  
Sediment Cores ◽  
Sediment Accumulation ◽  
Late Glacial ◽  
Sediment Concentration ◽  
Diatom Assemblage ◽  
Laminated Sediments ◽  
Sedimentation Rates ◽  
Baffin Island ◽  
Sediment Input

Tasikutaaq Lake, on Cumberland Peninsula, Baffin Island, receives inflow and fine sediment from a 448 km2 drainage basin, 21% of which is glacier covered. During the summer of 1983 the lake remained essentially isothermal between about 4 and 6 °C. The suspended sediment concentration of inflow never exceeded 100 mg L−1 with overflow and homopycnal flow dominant.Surface sediments are clearly laminated, although varves are not apparent. The sediments are very fine, with less than 3% sand in all but the most proximal sites. Average sedimentation rates between 1976 and 1983 ranged from about 4 mm a−1 to 0.25 mm a−1 down lake from the point of inflow. The absence of varves is a function of the low rates of sediment accumulation and the long residence time of the fine sediments in the water column.Three sediment cores up to 135 cm in length reveal marked changes in sediment characteristics and diatom assemblages through the Holocene. During the late Foxe Glaciation it is likely that glacier ice contacted the lake, with retreat upvalley recorded by thinly varved (?) silts. By 7580 ± 140 BP ice had retreated to near its present margins. The earliest diatom assemblage in the cores is dominated by small Fragilaria spp., typical of late glacial, pioneering environments. Sedimentation rates during much of the Hypsithermal were about five times less than at present, with the resulting massive sediments having "nonglacial" characteristics despite the presence of glacial ice in the drainage basin. A planktonic diatom flora suggests that summer lake ice cover was minimal at this time. A climatic deterioration at about 4500 BP marks the onset of the Neoglacial, recorded by a shift in the diatom assemblage to species characteristic of more shallow water environments. Retreat from Neoglacial moraines is recorded by clearly laminated sediments and increasing accumulation rates. In general, laminated sediments relate to periods of high sediment input associated with glacial retreat, whereas massive sediments relate to low sediment input in association with glacial stabilization or advance.

scholarly journals Atomic Absorption Spectrometric Determination of Chromium, Copper, Lead, Mercury, and Zinc in Sediments Collected in Bayou d'Inde, Southwestern Louisiana

2002 ◽  
Vol 85 (1) ◽  
pp. 225-232 ◽  
Author(s):  
Carey Hardaway ◽  
Kermit Gauthreaux ◽  
Joseph Sneddon ◽  
James N Beck
Keyword(s):  
Trace Metals ◽  
Atomic Absorption ◽  
Sediment Cores ◽  
Sedimentation Rates ◽  
Low Concentrations ◽  
High Concentrations ◽  
Atomic Absorption Spectrometric ◽  
Copper Lead

Abstract The concentrations of the metals chromium (Cr), copper (Cu), lead (Pb), mercury (Hg), and zinc (Zn) were determined in sediment cores taken from Bayou d'Inde in southwestern Louisiana. Previous studies had reported elevated concentrations of these trace metals in sediments along this waterway. The current study, conducted more than a decade later, was designed to determine if these metals had migrated from the areas of highest concentrations. Concentrations as high as 400 mg/kg for Cr, 1100 mg/kg for Cu, 10 mg/kg for Hg, and 600 mg/kg for Pb and Zn were found. Areas of high concentrations of metals were isolated within a distance of about 1 km from the most highly contaminated areas in the bayou. Low concentrations of metals were found at the mouth of the bayou. Estimated sedimentation rates of 0.67–1.2 cm/yr were based on the burial of the sediments originally studied. The concentrations of the metals studied remained high and were also highly localized, both spatially and temporally.

scholarly journals Eddies in the Canada Basin, Arctic Ocean, Observed from Ice-Tethered Profilers

2008 ◽  
Vol 38 (1) ◽  
pp. 133-145 ◽  
Author(s):  
M-L. Timmermans ◽  
J. Toole ◽  
A. Proshutinsky ◽  
R. Krishfield ◽  
A. Plueddemann
Keyword(s):  
Arctic Ocean ◽  
Baroclinic Instability ◽  
Potential Temperature ◽  
Canada Basin ◽  
The Arctic ◽  
Central Basin ◽  
Ambient Flow ◽  
Central Canada ◽  
Flow Speeds ◽  
Order Of Magnitude

Abstract Five ice-tethered profilers (ITPs), deployed between 2004 and 2006, have provided detailed potential temperature θ and salinity S profiles from 21 anticyclonic eddy encounters in the central Canada Basin of the Arctic Ocean. The 12–35-m-thick eddies have center depths between 42 and 69 m in the Arctic halocline, and are shallower and less dense than the majority of eddies observed previously in the central Canada Basin. They are characterized by anomalously cold θ and low stratification, and have horizontal scales on the order of, or less than, the Rossby radius of deformation (about 10 km). Maximum azimuthal speeds estimated from dynamic heights (assuming cyclogeostrophic balance) are between 9 and 26 cm s−1, an order of magnitude larger than typical ambient flow speeds in the central basin. Eddy θ–S and potential vorticity properties, as well as horizontal and vertical scales, are consistent with their formation by instability of a surface front at about 80°N that appears in historical CTD and expendable CTD (XCTD) measurements. This would suggest eddy lifetimes longer than 6 months. While the baroclinic instability of boundary currents cannot be ruled out as a generation mechanism, it is less likely since deeper eddies that would originate from the deeper-reaching boundary flows are not observed in the survey region.

scholarly journals Diversity and Distribution of Marine Microbial Eukaryotes in the Arctic Ocean and Adjacent Seas

2006 ◽  
Vol 72 (5) ◽  
pp. 3085-3095 ◽  
Author(s):  
C. Lovejoy ◽  
R. Massana ◽  
C. Pedr�s-Ali�
Keyword(s):  
Arctic Ocean ◽  
18S Rrna Gene ◽  
Ocean Basin ◽  
Significant Loss ◽  
Canada Basin ◽  
The Arctic ◽  
Rrna Gene ◽  
The North ◽  
The Arctic Ocean ◽  
Upper Mixed Layer

ABSTRACT We analyzed microbial eukaryote diversity in perennially cold arctic marine waters by using 18S rRNA gene clone libraries. Samples were collected during concurrent oceanographic missions to opposite sides of the Arctic Ocean Basin and encompassed five distinct water masses. Two deep water Arctic Ocean sites and the convergence of the Greenland, Norwegian, and Barents Seas were sampled from 28 August to 2 September 2002. An additional sample was obtained from the Beaufort Sea (Canada) in early October 2002. The ribotypes were diverse, with different communities among sites and between the upper mixed layer and just below the halocline. Eukaryotes from the remote Canada Basin contained new phylotypes belonging to the radiolarian orders Acantharea, Polycystinea, and Taxopodida. A novel group within the photosynthetic stramenopiles was also identified. One sample closest to the interior of the Canada Basin yielded only four major taxa, and all but two of the sequences recovered belonged to the polar diatom Fragilariopsis and a radiolarian. Overall, 42% of the sequences were <98% similar to any sequences in GenBank. Moreover, 15% of these were <95% similar to previously recovered sequences, which is indicative of endemic or undersampled taxa in the North Polar environment. The cold, stable Arctic Ocean is a threatened environment, and climate change could result in significant loss of global microbial biodiversity.

scholarly journals Fluxes of As, Cu, Hg, Pb in lake sediments in the Coppermine River basin, Canada

2007 ◽  
Vol 38 (2) ◽  
pp. 177-185 ◽  
Author(s):  
Liisa Peramaki ◽  
Michael Stone
Keyword(s):  
Trace Metals ◽  
River Basin ◽  
Anthropogenic Activities ◽  
Sediment Cores ◽  
Sediment Accumulation ◽  
Temporal Distribution ◽  
Atmospheric Pollutants ◽  
Sedimentation Rates ◽  
Gravity Corer ◽  
Coppermine River

Many watersheds in northern Canada are experiencing increasing pressures from resource extraction, development and the long-range transport of atmospheric pollutants. This study examines sediment accumulation and the spatial and temporal distribution of trace metals in bottom sediment of down gradient lakes in the headwaters of the Coppermine River basin, Canada. Sediment cores were collected from Lac de Gras, Desteffany Lake, Point Lake and Daring Lake using a plastic lined K–B single-gravity corer. Each core was dated using 210Pb and concentrations of trace metals (As, Cu, Hg, Pb) were determined in core sections. Sedimentation rates ranged from 101 g m−2 yr−1 at Desteffany Lake to 156 g m−2 yr−1 at Daring Lake and are comparable to other northern lakes. Concentrations of As and Cu were significantly higher at Lac de Gras. Metal loading data and enrichment ratios show that concentrations of Pb and Hg are elevated compared to historic background levels. Metal enrichment is from anthropogenic activities and atmospheric inputs. Lake sediment represents a good indicator of state for the Coppermine basin and documents historic trends of metal deposition. However, the indicator has low sensitivity to change and coarse temporal resolution due to low sedimentation rates in northern environments.

Central Arctic Ocean Response to Pleistocene Earth-Orbital Variations

1984 ◽  
Vol 22 (1) ◽  
pp. 121-128 ◽  
Author(s):  
Robin F. Boyd ◽  
David L. Clark ◽  
Glenn Jones ◽  
W.F. Ruddiman ◽  
A. McIntyre ◽  
...  
Keyword(s):  
Arctic Ocean ◽  
Sediment Cores ◽  
The Arctic ◽  
Lower Latitude ◽  
Sedimentation Rates ◽  
Orbital Forcing ◽  
Central Arctic Ocean ◽  
The Third ◽  
Ocean Response ◽  
Ocean Sediment

Three central Arctic Ocean sediment cores were sampled for percentage carbonate, number of foraminifera, and texture. These three parameters were used in spectral analyses to test the idea that the ice-covered Arctic Ocean may respond to orbital forcing in a different manner than has been indicated for lower latitude ice-free oceans. The record for two of the cores represents approximately 1 my, and the record for the third, approximately 400,000 yr. The 100,000-yr frequency is well represented in all of the cores. A 40,000-yr frequency may be present, as well. An unexpected 70,000-yr frequency occurs in most of the spectra and may reflect nonlinear sedimentation rates or the combined effect of obliquity and eccentricity. The strong 100,000-yr signal confirms that, in spite of ice feedback, the Arctic Ocean has responded to orbital forcing in much the same manner as have ice-free oceans.

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