scholarly journals Dinocyst and acritarch biostratigraphy of the Late Pliocene to Early Pleistocene at Integrated Ocean Drilling Program Site U1307 in the Labrador Sea

2020 ◽  
Vol 39 (1) ◽  
pp. 41-60
Author(s):  
Aurélie Marcelle Renée Aubry ◽  
Stijn De Schepper ◽  
Anne de Vernal
Keyword(s):  
North Atlantic ◽  
Early Pleistocene ◽  
Labrador Sea ◽  
Ocean Drilling Program ◽  
Late Pliocene ◽  
Ocean Drilling ◽  
The North ◽  
Integrated Ocean Drilling Program ◽  
Basin Scale ◽  
The North Atlantic

Abstract. We have analyzed marine palynomorphs (mainly dinocysts and acritarchs) from the Integrated Ocean Drilling Program Site U1307 in the Labrador Sea in order to establish a detailed biostratigraphy for the Late Pliocene to Early Pleistocene. We have defined three magnetostratigraphically calibrated dinocyst and acritarch biozones in the Late Pliocene to Early Pleistocene. Zone LS1 is defined based on the highest occurrence of Barssidinium graminosum and covers the later Pliocene from 3.21 to 2.75 Ma. Zone LS2 is marked by the acme of Pyxidinopsis braboi which occurs between 2.75 and 2.57 Ma, thus encompassing the Plio–Pleistocene transition. Finally, zone LS3 extends from 2.57 to 2.23 Ma in the Early Pleistocene. The palynostratigraphic record of IODP Site U1307 is difficult to correlate to other North Atlantic and Nordic Seas sites mainly because of a different temporal resolution and a lack of well-defined biostratigraphic marker species at the basin scale. The low abundance, discontinuous occurrence and asynchronous events of warm-water Pliocene taxa such as Invertocysta lacrymosa, Impagidinium solidum, Ataxiodinium confusum, Melitasphaeridium choanophorum and Operculodinium? eirikianum suggest cooler conditions in the Labrador Sea than elsewhere in the North Atlantic, reflecting a strong regionalism. Nevertheless, as recorded at other locations in the North Atlantic, the disappearance of many dinocyst and acritarch taxa around 2.75 Ma at Site U1307 reflects a strong ecological response accompanying the intensification of the Northern Hemisphere glaciation.

scholarly journals Late Pliocene age control and composite depths at ODP Site 982, revisited

2011 ◽  
Vol 7 (3) ◽  
pp. 1631-1646
Author(s):  
N. Khélifi ◽  
M. Sarnthein ◽  
B. D. A. Naafs
Keyword(s):  
Northern Hemisphere ◽  
North Atlantic ◽  
Time Span ◽  
Ocean Drilling Program ◽  
Late Pliocene ◽  
Ocean Drilling ◽  
Proxy Records ◽  
The North ◽  
Sediment Records ◽  
The North Atlantic

Abstract. Ocean Drilling Program (ODP) Site 982 provided a key sediment section at Rockall Plateau for reconstructing northeast Atlantic paleoceanography and monitoring benthic δ18O stratigraphy over the Late Pliocene to Quaternary onset of major Northern Hemisphere Glaciation. A renewed hole-specific inspection of magnetostratigraphic events and the addition of epibenthic δ18O records for short Pliocene sections in holes 982A, B, and C, crossing core breaks in the δ18O record published for Hole 982B, now imply a major revision of composite core depths. After tuning to the orbitally tuned reference record LR04 the new composite δ18O record results in a hiatus, where the Kaena magnetic event might been lost, and in a significant age reduction for all proxy records by 130 to 20 ka over the time span 3.2–2.7 million yr ago (Ma). Our study demonstrates the significance of reliable composite-depth scales and δ18O stratigraphies in ODP sediment records for ocean-wide correlations in paleoceanography and makes Late Pliocene trends found at Site 982 much better comparable to those published from elsewhere in the North Atlantic.

scholarly journals Late Pliocene to early Pleistocene changes in the North Atlantic Current and suborbital-scale sea-surface temperature variability

2013 ◽  
Vol 28 (2) ◽  
pp. 274-282 ◽  
Author(s):  
Oliver Friedrich ◽  
Paul A. Wilson ◽  
Clara T. Bolton ◽  
Christopher J. Beer ◽  
Ralf Schiebel
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
North Atlantic ◽  
Sea Surface ◽  
Early Pleistocene ◽  
North Atlantic Current ◽  
Late Pliocene ◽  
The North ◽  
The North Atlantic ◽  
Atlantic Current

scholarly journals Cenozoic Biostratigraphy and Global Change

1991 ◽  
Vol 9 (2) ◽  
pp. 117-117
Author(s):  
Brian M. Funnell
Keyword(s):  
Global Change ◽  
North Atlantic ◽  
Ocean Drilling Program ◽  
East Anglia ◽  
Ongoing Research ◽  
Ocean Drilling ◽  
The North ◽  
History Of ◽  
The North Atlantic ◽  
The University

Abstract. INTRODUCTIONIn May 1989 a British Micropalaeontological Society Symposium Meeting was held at the University of East Anglia under the title “Cenozoic Biostratigraphy and Global Change”. Fourteen lectures were given on this theme, many of them originating from investigations of DSDP/IPOD and ODP (Ocean Drilling Program) samples. All addressed the potential of micropalaeontological observations for interpreting the history of global and regional oceanographic and climatic change. Many results of this type of investigation are currently appearing in science journals such as “Paleoceanography” and “Palaeogeography, Palaeoclimatology, Palaeoecology” as well as in the “Proceedings of the Ocean Drilling Program”. British micropalaeontologists are taking an active part in this research, but relatively few of the resultant papers have so far appeared in the Journal of Micropalaeontology.Many of the lectures given at the May 1989 Symposium represented work already recently published, or due to be subsequently published in the Proceedings of the Ocean Drilling Program. Four papers, representing ongoing research not then due to be published, have been brought together here as a small thematic set, illustrating a variety of approaches to “Cenozoic Biostratigraphy and Global Change”. They range across Ostracoda, Coccolithophorida, Planktonic and Benthic Foraminifera, through the entire Cenozoic, including the latest Quaternary, and they include results from both the North Atlantic and Pacific oceans.TITLES“Global Change and the Biostratigraphy of North Atlantic Cenozoic deep water Ostracoda” - Robin C. Whatley and Graham P. Coles.“Palaeoclimatic control of Upper Pliocene Discoaster assemblages in the North Atlantic” - Alex. Chepstow-Lusty, Jan Backman. . .

scholarly journals Technical note: Late Pliocene age control and composite depths at ODP Site 982, revisited

2012 ◽  
Vol 8 (1) ◽  
pp. 79-87 ◽  
Author(s):  
N. Khélifi ◽  
M. Sarnthein ◽  
B. D. A. Naafs
Keyword(s):  
North Atlantic ◽  
Technical Note ◽  
Time Span ◽  
Sea Surface ◽  
Ocean Drilling Program ◽  
Late Pliocene ◽  
Ocean Drilling ◽  
Proxy Records ◽  
The North ◽  
Sediment Records

Abstract. Ocean Drilling Program (ODP) Site 982 provided a key sediment section at Rockall Plateau for reconstructing northeast Atlantic paleoceanography and monitoring benthic δ18O stratigraphy over the late Pliocene to Quaternary onset of major Northern Hemisphere glaciation. A renewed hole-specific inspection of magnetostratigraphic reversals and the addition of epibenthic δ18O records for short Pliocene sections in holes 982A, B, and C, crossing core breaks in the δ18O record published for Hole 982B, now imply a major revision of composite core depths. After tuning to the orbitally tuned reference record LR04, the new composite δ18O record results in a hiatus, where the Kaena magnetic subchron might have been lost, and in a significant age reduction for all proxy records by 130 to 20 ky over the time span 3.2–2.7 million years ago (Ma). Our study demonstrates the general significance of reliable composite-depth scales and δ18O stratigraphies in ODP sediment records for generating ocean-wide correlations in paleoceanography. The new concept of age control makes the late Pliocene trends in SST (sea surface temperature) and atmospheric pCO2 at Site 982 more consistent with various paleoclimate trends published from elsewhere in the North Atlantic.

scholarly journals A revised and improved age model for the middle Miocene part of IODP Site U1318 (Porcupine Basin, offshore southwestern Ireland)

2017 ◽  
Vol 155 (5) ◽  
pp. 1105-1116
Author(s):  
WILLEMIJN QUAIJTAAL ◽  
STEVEN TESSEUR ◽  
TIMME H. DONDERS ◽  
PHILIPPE CLAEYS ◽  
STEPHEN LOUWYE
Keyword(s):  
North Atlantic ◽  
Middle Miocene ◽  
Ocean Drilling Program ◽  
Carbon And Oxygen Isotopes ◽  
Ocean Drilling ◽  
The North ◽  
Integrated Ocean Drilling Program ◽  
Isotope Record ◽  
Porcupine Basin ◽  
Age Model

AbstractIntegrated Ocean Drilling Program Leg 307 Site U1318 is one of the few relatively complete middle Miocene drillcores from the North Atlantic (Porcupine Basin, offshore southwestern Ireland). Using benthic foraminiferal stable carbon and oxygen isotopes, the existing age model for Site U1318 was improved. The stable isotope record displays globally recognized isotope events, used to revise the existing magnetostratigraphy-based age model. Two intervals contained misidentified magnetochrons which were corrected. The sampled interval now has a refined age of 12.75–16.60 Ma with a temporal resolution of c. 29 ka.

Late Quaternary palaeo-oceanography of the Denmark Strait overflow pathway, South-East Greenland margin

1998 ◽  
Vol 180 ◽  
pp. 163-167
Author(s):  
Antoon Kuijpers ◽  
Jørn Bo Jensen ◽  
Simon R . Troelstra ◽  
And shipboard scientific party of RV Professor Logachev and RV Dana
Keyword(s):  
North Atlantic ◽  
Deep Water ◽  
Deep Convection ◽  
Conveyor Belt ◽  
Water Masses ◽  
Labrador Sea ◽  
Greenland Sea ◽  
The North ◽  
Denmark Strait ◽  
The North Atlantic

Direct interaction between the atmosphere and the deep ocean basins takes place today only in the Southern Ocean near the Antarctic continent and in the northern extremity of the North Atlantic Ocean, notably in the Norwegian–Greenland Sea and Labrador Sea. Cooling and evaporation cause surface waters in the latter region to become dense and sink. At depth, further mixing occurs with Arctic water masses from adjacent polar shelves. Export of these water masses from the Norwegian–Greenland Sea (Norwegian Sea Overflow Water) to the North Atlantic basin occurs via two major gateways, the Denmark Strait system and the Faeroe– Shetland Channel and Faeroe Bank Channel system (e.g. Dickson et al. 1990; Fig.1). Deep convection in the Labrador Sea produces intermediate waters (Labrador Sea Water), which spreads across the North Atlantic. Deep waters thus formed in the North Atlantic (North Atlantic Deep Water) constitute an essential component of a global ‘conveyor’ belt extending from the North Atlantic via the Southern and Indian Oceans to the Pacific. Water masses return as a (warm) surface water flow. In the North Atlantic this is the Gulf Stream and the relatively warm and saline North Atlantic Current. Numerous palaeo-oceanographic studies have indicated that climatic changes in the North Atlantic region are closely related to changes in surface circulation and in the production of North Atlantic Deep Water. Abrupt shut-down of the ocean-overturning and subsequently of the conveyor belt is believed to represent a potential explanation for rapid climate deterioration at high latitudes, such as those that caused the Quaternary ice ages. Here it should be noted, that significant changes in deep convection in Greenland waters have also recently occurred. While in the Greenland Sea deep water formation over the last decade has drastically decreased, a strong increase of deep convection has simultaneously been observed in the Labrador Sea (Sy et al. 1997).

The Marine Environment

2017 ◽  
Author(s):  
N. Penny Holliday ◽  
Stephanie Henson
Keyword(s):  
Primary Production ◽  
North Atlantic ◽  
Physical Environment ◽  
Seasonal Cycle ◽  
Physical Processes ◽  
The North ◽  
Basin Scale ◽  
The North Atlantic ◽  
Physical Features ◽  
Growth Distribution

The growth, distribution, and variability of phytoplankton populations in the North Atlantic are primarily controlled by the physical environment. This chapter provides an overview of the regional circulation of the North Atlantic, and an introduction to the key physical features and processes that affect ecosystems, and especially plankton, via the availability of light and nutrients. There is a natural seasonal cycle in primary production driven by physical processes that determine the light and nutrient levels, but the pattern has strong regional variations. The variations are determined by persistent features on the basin scale (e.g. the main currents and mixed layer regimes of the subtropical and subpolar gyres), as well as transient mesoscale features such as eddies and meanders of fronts.

The Metasomatized Mantle beneath the North Atlantic Craton: Insights from Peridotite Xenoliths of the Chidliak Kimberlite Province (NE Canada)

2019 ◽  
Vol 60 (10) ◽  
pp. 1991-2024 ◽  
Author(s):  
M G Kopylova ◽  
E Tso ◽  
F Ma ◽  
J Liu ◽  
D G Pearson
Keyword(s):  
North Atlantic ◽  
Thermal State ◽  
Mineral Chemistry ◽  
Mantle Metasomatism ◽  
Labrador Sea ◽  
The North ◽  
Rock Types ◽  
History Of ◽  
The North Atlantic ◽  
North Atlantic Craton

Abstract We studied the petrography, mineralogy, thermobarometry and whole-rock chemistry of 120 peridotite and pyroxenite xenoliths collected from the 156–138 Ma Chidliak kimberlite province (Southern Baffin Island). Xenoliths from pipes CH-1, -6, -7 and -44 are divided into two garnet-bearing series, dunites–harzburgites–lherzolites and wehrlites–olivine pyroxenites. Both series show widely varying textures, from coarse to sheared, and textures of late formation of garnet and clinopyroxene. Some samples from the lherzolite series may contain spinel, whereas wehrlites may contain ilmenite. In CH-6, rare coarse samples of the lherzolite and wehrlite series were derived from P = 2·8 to 5·6 GPa, whereas predominant sheared and coarse samples of the lherzolite series coexist at P = 5·6–7·5 GPa. Kimberlites CH-1, -7, -44 sample mainly the deeper mantle, at P = 5·0–7·5 GPa, represented by coarse and sheared lherzolite and wehrlite series. The bulk of the pressure–temperature arrays defines a thermal state compatible with 35–39 mW m–2 surface heat flow, but a significant thermal disequilibrium was evident in the large isobaric thermal scatter, especially at depth, and in the low thermal gradients uncharacteristic of conduction. The whole-rock Si and Mg contents of the Chidliak xenoliths and their mineral chemistry reflect initial high levels of melt depletion typical of cratonic mantle and subsequent refertilization in Ca and Al. Unlike the more orthopyroxene-rich mantle of many other cratons, the Chidliak mantle is rich (∼83 vol%) in forsteritic olivine. We assign this to silicate–carbonate metasomatism, which triggered wehrlitization of the mantle. The Chidliak mantle resembles the Greenlandic part of the North Atlantic Craton, suggesting the former contiguous nature of their lithosphere before subsequent rifting into separate continental fragments. Another, more recent type of mantle metasomatism, which affected the Chidliak mantle, is characterized by elevated Ti in pyroxenes and garnet typical of all rock types from CH-1, -7 and -44. These metasomatic samples are largely absent from the CH-6 xenolith suite. The Ti imprint is most intense in xenoliths derived from depths equivalent to 5·5–6·5 GPa where it is associated with higher strain, the presence of sheared samples of the lherzolite series and higher temperatures varying isobarically by up to 200 °C. The horizontal scale of the thermal-metasomatic imprint is more ambiguous and could be as regional as tens of kilometers or as local as <1 km. The time-scale of this metasomatism relates to a conductive length-scale and could be as short as <1 Myr, shortly predating kimberlite formation. A complex protracted metasomatic history of the North Atlantic Craton reconstructed from Chidliak xenoliths matches emplacement patterns of deep CO2-rich and Ti-rich magmatism around the Labrador Sea prior to the craton rifting. The metasomatism may have played a pivotal role in thinning the North Atlantic Craton lithosphere adjacent to the Labrador Sea from ∼240 km in the Jurassic to ∼65 km in the Paleogene.

scholarly journals The recent AMOC variability in the Subpolar Gyre: results across the OVIDE section

2020 ◽  
Author(s):  
Pascale Lherminier ◽  
Herlé Mercier ◽  
Fiz F. Perez ◽  
Marcos Fontela
Keyword(s):  
North Atlantic ◽  
Lower Limb ◽  
Deep Convection ◽  
Labrador Sea ◽  
Subpolar Gyre ◽  
North Atlantic Current ◽  
The North ◽  
Subarctic Front ◽  
The North Atlantic ◽  
Atlantic Current

<p><span>According to the subpolar AMOC index built from ARGO and altimetry, the AMOC amplitude across the OVIDE section (from Greenland to Portugal) was similar to that of the mid-1990s between 2014 and 2017, i.e. 4-5 Sv above the level of the 2000s. It then returned to average values in 2018. The same index computed independently from the biennial summer cruises over 2002-2018 confirms this statement. Interestingly, despite the concomitant cold and fresh anomaly in the subpolar Atlantic, the heat flux across OVIDE remains correlated with the AMOC amplitude. This can be explained by the paths taken by the North Atlantic Current and the transport anomalies in the subarctic front. In 2014, the OVIDE section was complemented by a section from Greenland to Newfoundland (GA01), showing how the water of the lower limb of the AMOC was densified by deep convection in the Labrador Sea. The spatial patterns of volume, heat, salt and oxygen transport anomalies after 2014 will be discussed at the light of the 2000s average.</span></p>

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