scholarly journals Late Miocene-Early Pliocene Planktonic Foraminifera and Palaeoceanography of the North Atlantic

1991 ◽  
Vol 9 (2) ◽  
pp. 145-151 ◽  
Author(s):  
Peter W. P. Hooper ◽  
Brian M. Funnell ◽  
Philip P. E. Weaver
Keyword(s):  
North Atlantic ◽  
Late Miocene ◽  
Planktonic Foraminifera ◽  
Time Interval ◽  
Messinian Salinity Crisis ◽  
Dominant Form ◽  
Early Pliocene ◽  
North East ◽  
The North ◽  
The North Atlantic

Abstract. Relative abundance variations of planktonic Foraminifera have been studied for the Late Miocene to Early Pliocene time interval of 7.0 to 3.5 Ma from three sites in the North East Atlantic; DSDP607 (41°N), DSDP609 (50°N) and DSDP611 (53°N), Particular attention has been given to the percentage of benthic Foraminifera of total (benthic + planktonic) Foraminifera as an index of dissolution by aggressive bottom waters, and to the percentage of dextral Neogloboquadrina pachyderma of total (dextral + sinistral) N. pachyderma as an index of “Sub-Polar” or warmer waters.Strong dissolution, probably associated with the northward penetration of aggressive Antarctic Bottom Water, is observed at two of the sites up to and during the initiation of the Messinian “Salinity Crisis” in the adjoining Mediterranean Sea at about 5.8 Ma. All three sites exhibit strong cyclic fluctuations of the percentage of dextral N. pachyderma during the Messinian “Salinity Crisis” interval, from approximately 5.8 Ma to 4.8 Ma. These are interpreted as indicating wide-ranging oscillations of a water mass boundary, analogous to the present-day Polar Front, in the North Atlantic during the “Salinity Crisis”. Following the re-filling of the Mediterranean with normal marine waters at about 4.8 Ma, the dextral form of N. pachyderma, which is more characteristic of warmer waters than the sinistral form, becomes the dominant form and shows less quantitative variation at all three sites throughout the Early Pliocene.

scholarly journals Insights into the Cenozoic geology of North Beirut (harbour area): biostratigraphy, sedimentology and structural history

2020 ◽  
Vol 2 (1) ◽  
Author(s):  
Germaine Noujaim Clark ◽  
Marcelle Boudagher-Fadel
Keyword(s):  
Planktonic Foraminifera ◽  
Foraminiferal Assemblage ◽  
Early Pliocene ◽  
North East ◽  
The North ◽  
Rock Structure ◽  
Structural History ◽  
Orbulina Universa ◽  
Geological Complexity ◽  
Harbour Area

The biostratigraphy and sedimentology of the outcrops and bedrock recently exposed in archaeological excavations around the harbour area of Beirut (~5 km²) unlock the geological and structural history of that area, which in turn are key to understanding the hydrocarbon and hydrogeological potential of the region. A key location (Site 2) of a studied outcrop section and newly uncovered bedrock is on the northern foothill cliff of East Beirut (Achrafieh). The outcrop section of carbonates is of Eocene beds overlain by conformable Miocene beds. The excavation of the slope bordering the outcrop uncovered a bedrock section of an early Pliocene shoreline of carbonate/siliciclastic sands at its base and topped by a beach-rock structure. The early Pliocene age of the shoreline section is dated by an assemblage of planktonic foraminifera that includes Sphaeroidinellopsis subdehiscens , Sphaeroidinella dehiscens and Orbulina universa . The Eocene carbonates of Site 2 extend the coverage of the previously reported Eocene outcrops in the harbour area. They form a parasequence of thin-bedded, chalky white limestones that includes the youngest fossil fish deposits in Lebanon ( Bregmaceros filamentosus ). The deposits are dated as early Priabonian by their association with the planktonic foraminiferal assemblage of Porticulasphaera tropicalis , Globigerinatheka barri , Dentoglobigerina venezuelana , Globigerina praebulloides , Turborotalia centralis and Borelis sp. The Middle Miocene carbonates that conformably overlie the early Priabonian, parasequence include a planktonic foraminiferal assemblage of Globigerinoides trilobus , Orbulina universa and Borelis melo . Elsewhere, in the harbour area, the preserved Eocene limestones are also overlain by conformable Miocene carbonate parasequences of Langhian–Serravallian age. Younger argillaceous limestone beds of the Mio/Pliocene age occur in the eastern central part of the harbour area and enclose an assemblage of Truncorotalia crassaformis , Globorotalia inflata and Orbulina universa . The three markers of old and recently raised structural blocks in the harbour area are a Lutetian/Bartonian marine terrace in the south west corner, a lower Pliocene shoreline carbonate section in the north east side and a Holocene raised beach of marine conglomerates in the north east corner of the area. The locations of these paleo-shorelines, less than 2 km apart, indicate a progressive platform narrowing of North Beirut since the Paleogene. This study underpins the geological complexity of the region and contributes to understanding the underlying geology, which will be needed for future regional archaeological, hydrocarbon and hydrogeological exploration.

A new species of amphipod, Megamphopus katagani sp. nov. (Crustacea: Peracarida: Photidae) from the Sea of Marmara (Turkey), with a key to the species of Megamphopus in the North Atlantic, Mediterranean and associated Seas

Zootaxa ◽  
2011 ◽  
Vol 2791 (1) ◽  
pp. 63 ◽  
Author(s):  
KEREM BAKIR ◽  
MURAT SEZGIN ◽  
ALAN A. MYERS
Keyword(s):  
New Species ◽  
North Atlantic ◽  
Sea Of Marmara ◽  
East Atlantic ◽  
North East ◽  
The North ◽  
The North Atlantic ◽  
A New Species

A new species of amphipod, Megamphopus katagani sp. nov., is described from the sea of Marmara (Turkey). A key to the species of Megamphopus known from the North-East Atlantic, Mediterranean and associated seas is provided.

scholarly journals Water mass distributions and transports for the 2014 GEOVIDE cruise in the North Atlantic

2018 ◽  
Vol 15 (7) ◽  
pp. 2075-2090 ◽  
Author(s):  
Maribel I. García-Ibáñez ◽  
Fiz F. Pérez ◽  
Pascale Lherminier ◽  
Patricia Zunino ◽  
Herlé Mercier ◽  
...  
Keyword(s):  
North Atlantic ◽  
Water Mass ◽  
Water Levels ◽  
Water Masses ◽  
Meridional Overturning Circulation ◽  
Labrador Sea ◽  
Intermediate Water ◽  
North East ◽  
The North ◽  
The North Atlantic

Abstract. We present the distribution of water masses along the GEOTRACES-GA01 section during the GEOVIDE cruise, which crossed the subpolar North Atlantic Ocean and the Labrador Sea in the summer of 2014. The water mass structure resulting from an extended optimum multiparameter (eOMP) analysis provides the framework for interpreting the observed distributions of trace elements and their isotopes. Central Waters and Subpolar Mode Waters (SPMW) dominated the upper part of the GEOTRACES-GA01 section. At intermediate depths, the dominant water mass was Labrador Sea Water, while the deep parts of the section were filled by Iceland–Scotland Overflow Water (ISOW) and North-East Atlantic Deep Water. We also evaluate the water mass volume transports across the 2014 OVIDE line (Portugal to Greenland section) by combining the water mass fractions resulting from the eOMP analysis with the absolute geostrophic velocity field estimated through a box inverse model. This allowed us to assess the relative contribution of each water mass to the transport across the section. Finally, we discuss the changes in the distribution and transport of water masses between the 2014 OVIDE line and the 2002–2010 mean state. At the upper and intermediate water levels, colder end-members of the water masses replaced the warmer ones in 2014 with respect to 2002–2010, in agreement with the long-term cooling of the North Atlantic Subpolar Gyre that started in the mid-2000s. Below 2000 dbar, ISOW increased its contribution in 2014 with respect to 2002–2010, with the increase being consistent with other estimates of ISOW transports along 58–59° N. We also observed an increase in SPMW in the East Greenland Irminger Current in 2014 with respect to 2002–2010, which supports the recent deep convection events in the Irminger Sea. From the assessment of the relative water mass contribution to the Atlantic Meridional Overturning Circulation (AMOC) across the OVIDE line, we conclude that the larger AMOC intensity in 2014 compared to the 2002–2010 mean was related to both the increase in the northward transport of Central Waters in the AMOC upper limb and to the increase in the southward flow of Irminger Basin SPMW and ISOW in the AMOC lower limb.

scholarly journals Mismatch between the depth habitat of planktonic foraminifera and the calibration depth of SST transfer functions may bias reconstructions

2013 ◽  
Vol 9 (2) ◽  
pp. 859-870 ◽  
Author(s):  
R. J. Telford ◽  
C. Li ◽  
M. Kucera
Keyword(s):  
Climate Sensitivity ◽  
North Atlantic ◽  
Transfer Functions ◽  
Thermal Structure ◽  
Planktonic Foraminifera ◽  
Near Surface ◽  
The North ◽  
Temperature Reconstructions ◽  
The North Atlantic ◽  
The Last Glacial

Abstract. We demonstrate that the temperature signal in the planktonic foraminifera assemblage data from the North Atlantic typically does not originate from near-surface waters and argue that this has the potential to bias sea surface temperature reconstructions using transfer functions calibrated against near-surface temperatures if the thermal structure of the upper few hundred metres of ocean changes over time. CMIP5 climate models indicate that ocean thermal structure in the North Atlantic changed between the Last Glacial Maximum (LGM) and the pre-industrial (PI), with some regions, mainly in the tropics, of the LGM ocean lacking good thermal analogues in the PI. Transfer functions calibrated against different depths reconstruct a marked subsurface cooling in parts of the tropical North Atlantic during the last glacial, in contrast to previous studies that reconstruct only a modest cooling. These possible biases in temperature reconstructions may affect estimates of climate sensitivity based on the difference between LGM and pre-industrial climate. Quantifying these biases has the potential to alter our understanding of LGM climate and improve estimates of climate sensitivity.

Ophlitaspongia and Ophlitaspongia papilla reinstated, and a new species of Ophlitaspongia described (Porifera: Demospongiae: Microcionidae)

1999 ◽  
Vol 79 (4) ◽  
pp. 609-620 ◽  
Author(s):  
C.M. Howson ◽  
S.J. Chambers
Keyword(s):  
New Species ◽  
North Atlantic ◽  
Deep Water ◽  
The Other ◽  
East Atlantic ◽  
Halichondria Panicea ◽  
North East ◽  
The North ◽  
The North Atlantic ◽  
A New Species

A new species of Ophlitaspongia (Porifera: Microcionidae) from wave-exposed sublittoral rock in the north-east Atlantic is described and compared to the two other species recorded from the genus in the north-east Atlantic. The species known as Ophlitaspongia seriata is considered to be a junior synonym of Halichondria panicea. Consequently, the name O. papilla has been reinstated. The other recorded species O. basifixa, is from deep water. Ophlitaspongia basifixa has characters which differentiate it from Ophlitaspongia sp. nov. The genus Ophlitaspongia has been separated from related genera and reinstated for species in the North Atlantic.

Climatic Record of the Past 130,000 Years in North Atlantic Deep-Sea Core V23-82: Correlation with the Terrestrial Record

1973 ◽  
Vol 3 (1) ◽  
pp. 110-116 ◽  
Author(s):  
Constance Sancetta ◽  
John Imbrie ◽  
N.G. Kipp
Keyword(s):  
North Atlantic ◽  
Deep Sea ◽  
Planktonic Foraminifera ◽  
Linear Interpolation ◽  
Stratigraphic Correlation ◽  
Last Glacial ◽  
The Past ◽  
The North ◽  
The North Atlantic ◽  
The Last Glacial

AbstractQuantitative paleo-environmental analyses of planktonic foraminifera in 182 samples covering the past 130,000 years in North Atlantic deep-sea core V23-82 yield time series interpreted in terms of changing surface-water conditions. An absolute chronology is estimated by linear interpolation between levels dated by 14C or by stratigraphic correlation with other radiometrically dated climatic records. Significant events include: (1) rapid warming at 127,000 YBP, marking the start of the penultimate North Atlantic and European interglacial; (2) 124,000 YBP temperature maximum (Eemian); (3) 109,000 YBP cooling, correlated with the beginning of the last European glaciation (Würm), and representing a temporary cooling of the North Atlantic; (4) severe cooling 73,000 YBP, marking the start of the last full glacial regime in the North Atlantic; (5) short warm intervals within the last glacial regime dated at 59,000 YBP, 48,000 YBP, and 31,000 YBP; (6) rapid termination of the last glacial interval at 11,000 YBP; (7) a 6000 YBP hypsi-saline, followed by lowering salinity values presumably associated with decreasing flux of Gulf Stream waters over the core site.

scholarly journals Modelling global-scale climate impacts of the late Miocene Messinian Salinity Crisis

2013 ◽  
Vol 9 (4) ◽  
pp. 4807-4853 ◽  
Author(s):  
R. F. Ivanovic ◽  
P. J. Valdes ◽  
R. Flecker ◽  
M. Gutjahr
Keyword(s):  
Atlantic Ocean ◽  
North Atlantic ◽  
Late Miocene ◽  
General Circulation ◽  
North Atlantic Ocean ◽  
Global Scale ◽  
Climate Impacts ◽  
Meridional Overturning Circulation ◽  
Messinian Salinity Crisis ◽  
The North

Abstract. Late Miocene tectonic changes in Mediterranean–Atlantic connectivity and climatic changes caused Mediterranean salinity to fluctuate dramatically, including a ten-fold increase and near-freshening. Recent proxy- and model-based evidence suggests that at times during this Messinian Salinity Crisis (MSC, 5.96–5.33 Ma), highly-saline and highly-fresh Mediterranean water flowed into the North Atlantic Ocean, whilst at others, no Mediterranean Outflow Water (MOW) reached the Atlantic. By running extreme, sensitivity-type experiments with a fully-coupled ocean–atmosphere general circulation model, we investigate the potential of these various MSC MOW scenarios to impact global-scale climate. The simulations suggest that MOW had a greater influence on North Atlantic Ocean circulation and climate than it does today. We also find that depending on the presence, strength and salinity of MOW, the MSC could have been capable of cooling mid-high northern latitudes by more than 1.2 °C, with the greatest cooling taking place in the Labrador, Greenland–Iceland–Norwegian and Barents Seas. With hypersaline-MOW, a component of North Atlantic Deep Water formation shifts to the Mediterranean, strengthening the Atlantic Meridional Overturning Circulation (AMOC) south of 35° N by 3–7 Sv. With hyposaline-MOW, AMOC completely shuts down, inducing a bipolar climate anomaly with strong cooling in the North (up to −10.5 °C) and weaker warming in the South (up to +2.5 °C). These simulations identify key target regions and climate variables for future proxy-reconstructions to provide the best and most robust test cases for (a) assessing Messinian model performance, (b) evaluating Mediterranean–Atlantic connectivity during the MSC and (c) establishing whether or not the MSC could ever have affected global-scale climate.

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