Amino acid epimerization implies rapid sedimentation rates in Arctic Ocean cores

Nature ◽  
1984 ◽  
Vol 310 (5980) ◽  
pp. 772-775 ◽  
Author(s):  
Hans Petter Sejrup ◽  
Gifford H. Miller ◽  
Julie Brigham-Grette ◽  
Reidar Løvlie ◽  
David Hopkins
Keyword(s):  
Amino Acid ◽  
Arctic Ocean ◽  
Sedimentation Rates

scholarly journals Revised Magnetostratigraphies Confirm Low Sedimentation Rates in Arctic Ocean Cores

1988 ◽  
Vol 29 (1) ◽  
pp. 43-53 ◽  
Author(s):  
William K. Witte ◽  
Dennis V. Kent
Keyword(s):  
Amino Acid ◽  
Arctic Ocean ◽  
High Coercivity ◽  
Sedimentation Rates ◽  
General Lack ◽  
The Core ◽  
Neogene Sediments

The general lack of an age-diagnostic biostratigraphy in the Neogene sediments of the abyssal Arctic Ocean has emphasized the importance of magnetostratigraphy in providing chronostratigraphic control in these sediments. Sedimentation rates interpreted from early magnetostratigraphic studies of cores taken from the T3 ice island in the western Mendeleev Plain were estimated to be on the order of 1 mm/103 yr; however, recent amino acid epimerization studies of a core from the same area have suggested sedimentation rates of almost 15 mm/103 yr. This controversy has led us to reexamine the paleomagnetism of several of these cores. Our alternating field demagnetization studies indicate that many of these cores have an intense, high coercivity overprint, acquired after the core was opened, that is adequately removed only after treatment at 20 to 70 mT. We have remeasured samples from two cores after demagnetizations up to 80 mT and can confirm the position of the Brunhes/Matuyama boundary originally identified in the cores. In addition, the Jaramillo and Olduvai subchrons are identified. Average sedimentation rates in these two cores are 2–3 mm/103 yr, similar to the original estimates based on reversal stratigraphy, as well as those determined from recent radiocarbon studies, but incompatible with the amino acid-based dates.

scholarly journals Arctic Ocean

Radiocarbon ◽  
1988 ◽  
Vol 30 (3) ◽  
pp. 277-277
Keyword(s):  
Arctic Ocean ◽  
Arctic Basin ◽  
The Arctic ◽  
Sedimentation Rates ◽  
University Of Wisconsin ◽  
The University

This study was undertaken in cooperation with David Clark of the University of Wisconsin in order to confirm the previous estimates of low sedimentation rates in the Arctic Basin (see Table 7).

Late Quaternary history of the Lake O'Hara region, British Columbia – an evaluation of sedimentation rates and bulk amino acid ratios in lacustrine records

1988 ◽  
Vol 25 (7) ◽  
pp. 1037-1048 ◽  
Author(s):  
Mel A. Reasoner ◽  
Nathaniel W. Rutter
Keyword(s):  
Amino Acid ◽  
Aspartic Acid ◽  
Sedimentation Rate ◽  
River Sediments ◽  
Sedimentation Rates ◽  
Rate Data ◽  
Radiocarbon Dates ◽  
Clastic Sediments ◽  
Lake Cores ◽  
Total Sedimentation

Lake O'Hara (subalpine) and Opabin Lake (alpine) are situated directly adjacent to a high section of the Continental Divide in the central Canadian Rocky Mountains. Core samples recovered from the lakes show a consistent stratigraphy comprising gyttja and underlying inorganic clastic sediments. The gyttja contains Bridge River (2350 years BP) and Mazama (6800 years BP) tephras and is separated from the lower clastic sediments by a sharp, conformable contact. Radiocarbon dates obtained from conifer needles, extracted from directly above the contact, indicate that deglaciation had proceeded upvalley from the O'Hara basin priorto ca. 10 100 years BP. Preliminary palaeobotanical and macrofossil data suggest that a Pinus–Abies forest with lesser Picea was established in the vicinity of Lake O'Hara by this time. Consequently, the minimum age of moraine systems situated downvalley from Lake O'Hara is Late Wisconsinan.Mean annual sedimentation rates were derived from sediment thickness data from 14 Lake O'Hara and 2 Opabin Lake cores. Averaged total sedimentation rate values from the Lake O'Hara cores are 0.13 mm/year (post-Bridge River), 0.13 mm/year (Mazama – Bridge River) and 0.05 mm/year (11 000 years BP – Mazama). Averaged total sedimentation rate values from the Opabin Lake cores are 0.19 mm/year (post-Bridge River), 0.07 mm/year (Mazama – Bridge River), and 0.06 mm/year (8530 years BP – Mazama). Higher total sedimentation rates in post-Bridge River sediments of Opabin Lake are presumably related to climatic conditions associated with more extensive upvalley ice during the last ca. 2300 years. Highly variable sedimentation rate data obtained from the Lake O'Hara cores suggest that the use of sedimentation rate data as a proxy record of upvalley glacial activity is inappropriate in the Lake O'Hara setting where inflowing glacial stream systems are interrupted by upvalley lake basins.Aspartic acid D/L ratios were derived from bulk gyttja samples of known age from seven Lake O'Hara and one Opabin Lake core. In all but two cases, aspartic acid D/L ratios increase consistently with respect to sediment age. The increasing downcore trends in the aspartic acid D/L ratios suggest the possibility of using amino acid data from bulk gyttja samples as a check for reworking in cases where chronostratigraphic markers are absent.

scholarly journals Abundance and Single-Cell Activity of Heterotrophic Bacterial Groups in the Western Arctic Ocean in Summer and Winter

2012 ◽  
Vol 78 (7) ◽  
pp. 2402-2409 ◽  
Author(s):  
Mrinalini P. Nikrad ◽  
M. T. Cottrell ◽  
D. L. Kirchman
Keyword(s):  
Amino Acid ◽  
Arctic Ocean ◽  
Heterotrophic Bacteria ◽  
Cell Activity ◽  
Organic Substrates ◽  
Content Type ◽  
Western Arctic Ocean ◽  
Western Arctic ◽  
Bacterial Groups

ABSTRACTEnvironmental conditions in the western Arctic Ocean range from constant light and nutrient depletion in summer to complete darkness and sea ice cover in winter. This seasonal environmental variation is likely to have an effect on the use of dissolved organic matter (DOM) by heterotrophic bacteria in surface water. However, this effect is not well studied and we know little about the activity of specific bacterial clades in the surface oceans. The use of DOM by three bacterial subgroups in both winter and summer was examined by microautoradiography combined with fluorescencein situhybridization. We found selective use of substrates by these groups, although the abundances of Ant4D3 (AntarcticGammaproteobacteria),Polaribacter(Bacteroidetes), and SAR11 (Alphaproteobacteria) were not different between summer and winter in the Beaufort and Chukchi Seas. The number of cells taking up glucose within all three bacterial groups decreased significantly from summer to winter, while the percentage of cells using leucine did not show a clear pattern between seasons. The uptake of the amino acid mix increased substantially from summer to winter by the Ant4D3 group, although such a large increase in uptake was not seen for the other two groups. Use of glucose by bacteria, but not use of leucine or the amino acid mix, related strongly to inorganic nutrients, chlorophylla, and other environmental factors. Our results suggest a switch in use of dissolved organic substrates from summer to winter and that the three phylogenetic subgroups examined fill different niches in DOM use in the two seasons.

scholarly journals Sedimentation rates in the Makarov Basin, central Arctic Ocean: A paleomagnetic and rock magnetic approach

2001 ◽  
Vol 16 (4) ◽  
pp. 368-389 ◽  
Author(s):  
Norbert R. Nowaczyk ◽  
Thomas W. Frederichs ◽  
Heidi Kassens ◽  
Nils Nørgaard-Pedersen ◽  
Robert F. Spielhagen ◽  
...  
Keyword(s):  
Arctic Ocean ◽  
Sedimentation Rates ◽  
Central Arctic Ocean ◽  
Makarov Basin

230Th-excess inventory and distribution in a southern Mendeleev Ridge core (Arctic Ocean): linkage with late Quaternary sedimentological and paleogeographical changes

2020 ◽  
Author(s):  
Tengfei Song ◽  
Claude Hillaire-Marcel ◽  
Yanguang Liu
Keyword(s):  
Grain Size ◽  
Sea Ice ◽  
Arctic Ocean ◽  
Late Quaternary ◽  
Critical Time ◽  
Clay Mineralogy ◽  
Sedimentation Rates ◽  
Central Arctic Ocean ◽  
Sea Levels ◽  
Ice Production

<p>In addition to <sup>14</sup>C-data, sedimentary excesses in <sup>230</sup>Th  (<sup>230</sup>Th<sub>xs</sub>) in central Arctic Ocean cored sequences yielded critical time constrains and sedimentation rates estimates, at least, at sites characterized by very low sedimentation rates (<< 1cm/ka). Closer to the Russian margin, where higher accumulation rates are recorded based on <sup>14</sup>C-ages, the setting of a reliable stratigraphy based on <sup>230</sup>Th<sub>xs</sub> reveals more challenging, as illustrated here, based on the analysis of  a gravity core raised from the southern Mendeleev Ridge (core ARC7-E25; -179.4°E, 79.0°N; 1200 m water depth; 320 cm long). Subsamples were collected at a 4 to 8 cm interval. Measurements included: AMS <sup>14</sup>C in foraminifera, grain size, bulk Xray mineralogy, clay mineralogy, geochemistry (C<sub>org</sub>, C<sub>inorg</sub>,<sup>13</sup>C<sub>org</sub>, <sup>238</sup>U, <sup>234</sup>U, <sup>230</sup>Th, <sup>226</sup>Ra, <sup>210</sup>Pb). Data indicate that some sediment were lost at core top. Nevertheless, <sup>14</sup>C and <sup>230</sup>Th<sub>xs  </sub>data allow estimating a mean sedimentation rate of about 6 to 7 mm/ka during the last two climatic cycles. A comparison of the <sup>230</sup>Th<sub>xs </sub>inventory and distribution pattern with those from other cores allows identifying important parameters involved in the cycling of the water column-produced <sup>230</sup>Th in this basin and its sporadic sedimentary accumulation, in particular linkages with sea-ice production over shelves, thus sea-levels, sea-ice rafting routes, grain-size and mineralogy, potential winnowing of fine fractions, role of brines and relative duration of intervals with reduced or nil sedimentation preceding <sup>230</sup>Th<sub>xs</sub>-accumulation intervals.</p>

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