Sédimentation sur la Ride de Terre-Neuve

1975 ◽  
Vol 12 (6) ◽  
pp. 1019-1035 ◽  
Author(s):  
L. Pastouret ◽  
G. A. Auffret ◽  
M. Hoffert ◽  
M. Melguen ◽  
H. D. Needham ◽  
...  
Keyword(s):  
Gulf Stream ◽  
Accumulation Rate ◽  
Late Quaternary ◽  
Stream Water ◽  
Sediment Accumulation ◽  
Distribution Patterns ◽  
Last Interglacial ◽  
The Holocene ◽  
The Core ◽  
The North

The stratification, in part more or less rhythmic, of a fifteen metre long core of predominantly hemi-pelagic sediment from the northern slope of the Southeast Newfoundland Ridge reflects changing distribution patterns of different water masses during the late Quaternary. In particular, the lithological and microfaunal characteristics of the sediments indicate that, in the area of the core, the cold Labrador Current from the north and the continental slope water have had a permanent influence on the sedimentation pattern, whereas the paths of the Gulf Stream water have shifted intermittently. The influence of the Gulf Stream is clearly identifiable during the Holocene and during the last interglacial (faunal zone X). Ice-rafted debris and relatively coarse turbidite-type beds are more prominent in sequences deposited under a glacial régime, notably in those that accumulated near the end of the late Pleistocene and the beginning of the Holocene. The upper limit of faunal zone X (Sangamon-Würm) is placed close to 1000 cm depth in the core on the basis of the disappearance at this level of Globorotalia tumida flexuosa (Koch). The resulting estimate of the subsequent mean sediment accumulation rate is of the order of 10 cm/1000 y.

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 Quaternary palaeoceanography and palaeogeography in northern Denmark: a review of results from the Skagen cores

1996 ◽  
Vol 43 ◽  
pp. 22-31
Author(s):  
Karen Luise Knudsen ◽  
Keld Conradsen ◽  
, Susanne Heier Nielsen ◽  
Marit-Solveig Seidenkrantz
Keyword(s):  
North Atlantic ◽  
Late Quaternary ◽  
Climatic Changes ◽  
Last Interglacial ◽  
North Atlantic Region ◽  
Atlantic Region ◽  
Radiocarbon Dates ◽  
Marine Deposits ◽  
The North ◽  
Late Weichselian

Palaeoenvironmental reconstructions from the Skagen record contribute to the understanding of Late Quatemary climatic changes and variations in the oceanographic circulation pattem in the entire North Atlantic region. The Skagen cores penetrated c. 192 m of Quatemary sediments comprising two marine Late Quaternary records: A 7 m marine unit (185.3-178.3 m) comprised the entire last interglacial, including its lower and upper transitions (Late Saalian-Eemian-Early Weichselian), while the upper 132 m of marine deposits covered the last about 15,000 years from the Late Weichselian through the Holocene, including the Pleistocene-Holocene transition. Results from the study of lithology, foraminifera, stable isotope measurements and radiocarbon dates are reviewed while emphasizing the most important contributions to the general understanding of the North Atlantic Quatemary history

scholarly journals Holocene hydrological changes in the Rhône River (NW Mediterranean) as recorded in the marine mud belt

2016 ◽  
Vol 12 (7) ◽  
pp. 1539-1553 ◽  
Author(s):  
Maria-Angela Bassetti ◽  
Serge Berné ◽  
Marie-Alexandrine Sicre ◽  
Bernard Dennielou ◽  
Yoann Alonso ◽  
...  
Keyword(s):  
North Atlantic ◽  
Accumulation Rate ◽  
Sediment Accumulation ◽  
Progressive Increase ◽  
Ice Age ◽  
Sediment Delivery ◽  
The North ◽  
Catchment Areas ◽  
The North Atlantic ◽  
The Impact

Abstract. Expanded marine Holocene archives are relatively scarce in the Mediterranean Sea because most of the sediments were trapped in catchment areas during this period. Mud belts are the most suitable targets to access expanded Holocene records. These sedimentary bodies represent excellent archives for the study of sea–land interactions and notably the impact of the hydrological activity on sediment accumulation. We retrieved a 7.2 m long sediment core from the Rhône mud belt in the Gulf of Lions in an area where the average accumulation rate is ca. 0.70 m 1000 yr−1. This core thus provides a continuous and high-resolution record of the last 10 ka cal BP. A multiproxy dataset (XRF core scan, 14C dates, grain size and organic-matter analysis) combined with seismic stratigraphic analysis was used to document decadal to centennial changes in the Rhône hydrological activity. Our results show that (1) the early Holocene was characterized by high sediment delivery likely indicative of local intense (but short-duration) rainfall events, (2) important sediment delivery around 7 ka cal BP presumably related to increased river flux, (3) a progressive increase in continental/marine input during the mid-Holocene despite increased distance from river outlets due to sea-level rise possibly related to higher atmospheric humidity caused by the southward migration of the storm tracks in the North Atlantic, (4) multidecadal to centennial humid events took place in the late Holocene. Some of these events correspond to the cold periods identified in the North Atlantic (Little Ice Age, LIA; Dark Ages Cold Period) and also coincide with time intervals of major floods in the northern Alps. Other humid events are also observed during relatively warm periods (Roman Humid Period and Medieval Climate Anomaly).

Holocene Coral Reef Terraces and Coseismic Uplift of Huon Peninsula, Papua New Guinea

1993 ◽  
Vol 40 (2) ◽  
pp. 177-188 ◽  
Author(s):  
Y. Ota ◽  
J. Chappell ◽  
R. Kelley ◽  
N. Yonekura ◽  
E. Matsumoto ◽  
...  
Keyword(s):  
Coral Reef ◽  
Papua New Guinea ◽  
Late Quaternary ◽  
Mass Movement ◽  
New Guinea ◽  
Last Interglacial ◽  
The Holocene ◽  
Fluvial Terraces ◽  
Uplift Rates ◽  
Recurrence Intervals

AbstractAs many as six levels of emerged Holocene coral terraces occur along 40 km of coastline on the Huon Peninsula, Papua New Guinea, recording uplift history since culmination of the postglacial transgression. The Holocene reef crest, ca. 6000 yr B.P., is tilted down to the northwest, parallel to the coast and concordant with the deformation of the last interglacial coral reef terrace, and descends from 23 to 12 m in the study area. The pattern and rate of deformation have been uniform in the late Quaternary because average uplift rates have remained the same since the last interglaciation. The Holocene terraces described here are erosional features with regressive encrusting corals, developed upon the Holocene transgressive reef. The multiple levels represent episodic, probably coseismic uplift, which has occurred repeatedly in the last ca. 6000 yr. Significant longshore variation in the age of the lowest terrace, from 1700 to 2500 yr B.P., suggests independent coseismic uplift on different sectors of the coast. This is supported by age-height relationships of the higher Holocene terraces. Nonlinear uplift during the Holocene, with recurrence intervals increasing toward the present, is clearly recorded by the regressive terraces in each subregion. Some of the Holocene regressive terraces grade laterally into fluvial terraces capped with debris-flow deposits, probably reflecting seismically triggered mass movement.

Late Quaternary environment of southern Windmill Islands, East Antarctica

2002 ◽  
Vol 14 (4) ◽  
pp. 385-394 ◽  
Author(s):  
HELEN KIRKUP ◽  
MARTIN MELLES ◽  
DAMIAN B. GORE
Keyword(s):  
Late Quaternary ◽  
Ice Core ◽  
Open Water ◽  
Climatic Conditions ◽  
East Antarctica ◽  
The Holocene ◽  
Last Glacial ◽  
The Core ◽  
Windmill Islands ◽  
The Last Glacial

Analyses on a sediment core collected from the Windmill Islands, East Antarctica are used to demonstrate that climatic conditions in this region prior to the Last Glacial Maximum were similar to those during the Holocene and that the area was overrun by ice at some stage between 26 kyr BP and the onset of biogenic sedimentation 11 kyr BP. The 10.9 m long core was taken from a marine inlet (epishelf lake) on Peterson Island and is predominantly a sapropel of Holocene age. Material in the lower part of the core includes a till layer lain down during the last glacial in the region and below this till is material which has been dated to 26 kyr BP. Geochemical analyses conducted on the core demonstrate similarities between the Holocene sequence and the preglacial material. The Holocene sequence shows enhanced biogenic production and periods of open water around 4 kyr BP, suggesting a climatic optimum around that time. A subsequent decline in conditions, probably a colder climate with greater extent of sea ice, is evident from 1 kyr BP to the present. The data support results from ice core studies on nearby Law Dome, which suggest there was a period of warming around 11.5 to 9 kyr BP, that recent summer temperatures are low relative to a few centuries ago, and that increasing winter temperatures are the main contributing factor to a recent overall warming in the region.

Formal Status and Vegetational Development of the Eemian Interglacial in Northwestern and Southern Europe

2002 ◽  
Vol 58 (1) ◽  
pp. 41-44 ◽  
Author(s):  
Charles Turner
Keyword(s):  
Western Europe ◽  
Southern Europe ◽  
Last Interglacial ◽  
The Holocene ◽  
The North ◽  
Vegetational Succession ◽  
The Alps ◽  
Formal Status ◽  
Eemian Interglacial

AbstractThe terms Eem and Eemian have been applied to lithostratigraphic, chronostratigraphic, and biostratigraphic aspects of the last interglacial in western Europe. Eemian vegetational successions show strong uniformity at sites from western France across the North European Plain to Poland, suggesting, by comparison with the Holocene, that major pollen zones are broadly synchronous. South of the Alps and Pyrenees, a different vegetational succession is observed with no evidence for a substage of post-temperate cooling.

The late Quaternary sedimentary record of Stave Lake, southwestern British Columbia

1992 ◽  
Vol 29 (9) ◽  
pp. 1997-2006 ◽  
Author(s):  
Robert Gilbert ◽  
Joseph R. Desloges
Keyword(s):  
Late Quaternary ◽  
Sediment Surface ◽  
Total Thickness ◽  
The South ◽  
Sedimentary Record ◽  
The Holocene ◽  
Acoustic Data ◽  
The North ◽  
Sediment Input ◽  
Fraser Valley

The postglacial sedimentary record of 59 km2 Stave Lake was investigated using 3.5 kHz subbottom profiles and cores from the sediment surface. The acoustic data show a thin cover of acoustically transparent sediment (unit 1) overlying bedrock or glacial sediment on the floor of the lake. Overlying acoustically stratified sediment is divided into unit 2, which thins from 28 m in the south of the lake to less than 12 m in the north, and unit 3, which thins from 20 m in the north to about 12 m in the south. Unit 1 is interpreted as resulting from deposition in a relatively quiet lacustrine or marine environment following retreat of Vashon glaciers about 13 ka ago. Unit 2 is ascribed to deposits of sediment in runoff to Stave Lake from the Sumas ice sheet in the Fraser Valley and connecting valleys to the Stave Basin. Following the retreat of the Sumas ice about 11 ka ago, deposition of unit 3 resulted almost entirely from sediment input from Stave River entering at the north end of the lake. Raising the lake in 1912 by damming for hydroelectric generation resulted in deposition of a thin but distinct marker horizon in the sediment, from which modern rates of accumulation averaging 3 mm/a are estimated. These are more than twice the average rates for the Holocene estimated from the total thickness of unit 3. The rates of sediment yield calculated from accumulation in Stave Lake are 4.5 × 105 kg∙km−2∙a−1 (modern) and less than 2 × 105 kg∙km−2∙a−1 (averaged over the Holocene).

scholarly journals Holocene hydrological changes of the Rhone River (NW Mediterranean) as recorded in the marine mud belt

2016 ◽  
Author(s):  
M. A. Bassetti ◽  
S. Berné ◽  
M. A. Sicre ◽  
B. Dennielou ◽  
Y. Alonso ◽  
...  
Keyword(s):  
North Atlantic ◽  
Accumulation Rate ◽  
Sediment Accumulation ◽  
Progressive Increase ◽  
Ice Age ◽  
Sediment Delivery ◽  
The North ◽  
Catchment Areas ◽  
The North Atlantic ◽  
The Impact

Abstract. Expanded marine Holocene archives are relatively scarce in the Mediterranean Sea because most of the sediments were trapped in catchment areas during this period. Mud belts are most suitable targets to access expanded Holocene records. These sedimentary bodies represent excellent archives for the study of sea-land interactions and notably the impact of the hydrological activity on sediment accumulation. We retrieved a 7.2 m-long sediment core from the Rhone mud belt in the Gulf of Lions in an area where the average accumulation rate is of ca. 0.70 m/1000 years. This core thus provides a continuous and high-resolution record of the last 10 ka cal BP. A multi-proxy dataset (XRF-core scan, 14C dates, grain size and organic matter analysis) combined with seismic stratigraphic analysis was used to document decadal to centennial changes of the Rhone hydrological activity. Our results show that 1) the Early Holocene was characterized by high sediment delivery likely indicative of local intense (but short duration) rainfall events , 2) important sediment delivery around 7 ka cal BP roughly presumably related to increased river flux, 3) a progressive increase of continental/marine input during the Mid-Holocene despite increased distance from river outlets due to sea-level rise possibly related to higher atmospheric humidity caused by the southward migration of the storm tracks in the North Atlantic, 4) multi-decadal to centennial humid events in the Late Holocene. Some of these events correspond to the cold periods identified in the North Atlantic (Little Ice Age, LIA; Dark Age) and also coincide with time intervals of major floods a in the Northern Alps. Other humid events are also observed during relatively warm periods (Roman Humid Period and Medieval Climate Anomaly).

scholarly journals Reconstruction of Atlantic Water variability during the Holocene in the western Barents Sea

2013 ◽  
Vol 9 (4) ◽  
pp. 4293-4322 ◽  
Author(s):  
D. E. Groot ◽  
S. Aagaard-Sørensen ◽  
K. Husum
Keyword(s):  
Barents Sea ◽  
Distribution Patterns ◽  
Atlantic Water ◽  
The Arctic ◽  
Arctic Water ◽  
The Holocene ◽  
Fine Grained ◽  
The Core ◽  
Continuous Presence ◽  
Local Shift

Abstract. The gravity core JM09-KA11-GC from 345 m water depth on the western Barents Sea margin was investigated for distribution patterns of benthic foraminifera, stable isotopes, and sedimentological parameters to reconstruct the flow of Atlantic Water during the Holocene. The core site is located below the Atlantic water masses flowing into the Arctic Ocean and close to the Arctic Front. The results show continuous presence of Atlantic Water at the margin throughout the Holocene. During the Early Holocene, (11 700–9400 cal yr BP), bottom water temperatures rose by 2.5 °C due to the increased influence of Atlantic Water, although sea-ice was still present at this time. The transition to the Mid Holocene is characterized by a local shift in current regime, resulting in a ceased supply of fine-grained material to the core location. Throughout the Mid Holocene the δ18O values indicate a slight cooling, thereby following changes in insolation. In the last 1500 yr, inflow of Atlantic Water increased but was interrupted by periods of increased influence of Arctic Water causing periodically colder and more unstable conditions.

scholarly journals Modern silicon dynamics of a small high-latitude subarctic lake

2021 ◽  
Vol 18 (7) ◽  
pp. 2325-2345
Author(s):  
Petra Zahajská ◽  
Carolina Olid ◽  
Johanna Stadmark ◽  
Sherilyn C. Fritz ◽  
Sophie Opfergelt ◽  
...  
Keyword(s):  
Lake Sediments ◽  
High Latitude ◽  
Accumulation Rate ◽  
Stream Water ◽  
Groundwater Discharge ◽  
Sediment Accumulation ◽  
Mass Balances ◽  
Stream Discharge ◽  
Low Mass ◽  
Subarctic Lake

Abstract. High biogenic silica (BSi) concentrations occur sporadically in lake sediments throughout the world; however, the processes leading to high BSi concentrations vary. We explored the factors responsible for the high BSi concentration in sediments of a small, high-latitude subarctic lake (Lake 850). The Si budget of this lake had not been fully characterized before to establish the drivers of BSi accumulation in this environment. To do this, we combined measurements of variations in stream discharge, dissolved silica (DSi) concentrations, and stable Si isotopes in both lake and stream water with measurements of BSi content in lake sediments. Water, radon, and Si mass balances revealed the importance of groundwater discharge as a main source of DSi to the lake, with groundwater-derived DSi inputs 3 times higher than those from ephemeral stream inlets. After including all external DSi sources (i.e., inlets and groundwater discharge) and estimating the total BSi accumulation in the sediment, we show that diatom production consumes up to 79 % of total DSi input. Additionally, low sediment accumulation rates were observed based on the dated gravity core. Our findings thus demonstrate that groundwater discharge and low mass accumulation rate can account for the high BSi accumulation during the last 150 cal yr BP. Globally, lakes have been estimated to retain one-fifth of the annual DSi terrestrial weathering flux that would otherwise be delivered to the ocean. Well-constrained lake mass balances, such as presented here, bring clarity to those estimates of the terrestrial Si cycle sinks.

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