scholarly journals Magnetic susceptibility variations in Upper Pleistocene deep-sea sediments of the NE Atlantic: Implications for ice rafting and paleocirculation at the Last Glacial Maximum

1995 ◽  
Vol 10 (2) ◽  
pp. 221-250 ◽  
Author(s):  
Simon G. Robinson ◽  
Mark A. Maslin ◽  
I. Nicholas McCave
1998 ◽  
Vol 13 (3) ◽  
pp. 298-310 ◽  
Author(s):  
Nina R. Catubig ◽  
D. E. Archer ◽  
Roger Francois ◽  
Peter deMenocal ◽  
Will Howard ◽  
...  

2020 ◽  
Author(s):  
Andrei Briceag ◽  
Gabriel Ion ◽  
Mihaela Melinte-Dobrinescu ◽  
Dan Vasiliu ◽  
Naliana Lupascu

<p>The Danube Deep-Sea Fan, situated in NW Black Sea, is one of the most developed deep-sea sedimentary structures in Europe (Panin & Jipa, 2002). In 2018, in the framework of the uBiogas Project (24PCCDI/2018), several cores were acquired from the aforementioned area. In this study, high resolution microfaunal analyses coupled with sedimentological and geochemical ones, were performed on two gravity cores that revealed changes since the Last Glacial Maximum. The cores have been collected from two secondary canyons, situated in the E of the Danube Canyon, at 655,7 m (MN183_3_GC_1) and 1315 m water depths (MN183_8_GC_1). In both cores, three stratigraphic units as described by Ross & Degens (1974) were identified (oldest first): Unit 3 (Lacustrine lutite), Unit 2 (Sapropel Mud) and Unit 1 (Coccolith Mud).</p><p>The sediments of Unit 3 correspond to the Last Glacial Maximum and are marked by the presence of the cold-water ostracod species. The cores contain a reddish-brown clay and silty interval belonging to the post-glacial melt-water pulse of the Heinrich Event 1. In these deposits the ostracod assemblages display a high diversity and abundance. The CaCO<sub>3</sub> amount is very low, i.e. below 15%, except for the upper part where it reaches more than 50%. The samples of Unit 3 contain nannofossil assemblages that are entirely composed of reworked species from Cretaceous, Paleogene, Early and Middle Miocene intervals.</p><p>In Unit 2 (the sapropel), very few specimens of ostracods were identified, towards the top. During this depositional interval CaCO<sub>3 </sub>values are dropping again below 15%. The high abundance of the calcareous nannoplankton species Braarudosphaera bigelowii in the upper part of Unit 2 suggests the first strong influx of marine waters into the Black Sea basin.</p><p>In the youngest Unit 1, a brackish-marine ostracod assemblage, with low diversity and abundance was identified. This interval is characterized by the presence of polyhaline ostracods with Mediterranean origin. The ostracods from this assemblage tolerate salinities comprised between 17-21 ‰ and characterize a sub-littoral environment. The CaCO<sub>3</sub> values are increasing to more than 50%. During the depositional interval of Unit 1 the environmental was definitely a marine one, probably with a constant salinity of surface waters over 17 ppm, allowing the calcareous nannoplankton species Emiliania huxleyi and Braarudosphaera bigelowii to proliferate. The great abundance of the two taxa and especially of Emiliania huxleyi indicates the existence in the basin of a high nutrient input.</p><p>The financial support for this paper was provided by the Romanian Ministry of Research and Innovation, through the Programme 1 – Development of the National System of Research – Institutional Performance, Project of Excellence in Research-Innovation, Contract No. 8PFE/2018 and by the Project uBiogas, contract no. 24PCCDI/ 2018.</p><p> </p><p>Panin, N., Jipa, D., 2002. Danube river sediment input and its interaction with the northwestern Black Sea. Estuarine Coastline Shelf Science 54: 551–562.</p><p>Ross, D.A., Degens, E.T., 1974. Recent sediments of the Black Sea. In: Degens E.T. and Ross D.A. (Eds.), The Black Sea: Geology, Chemistry, and Biology. American Association of Petroleum Geologists, Tulsa, USA: 183–199.</p>


Bothalia ◽  
1983 ◽  
Vol 14 (3/4) ◽  
pp. 391-394 ◽  
Author(s):  
J. C. Vogel

The stable isotopes of hydrogen, oxygen and carbon can potentially provide evidence of past climates. The most detailed information has been obtained from variations in the oxygen-18 content of foraminifera from ocean floor cores, the analysis of which has produced a record of ocean temperature changes through the Quaternary and beyond. The use of isotope analysis of continental materials to reveal climatic change is more limited, but some advances have been made in recent years. One approach has been to utilize the variations in the isotopic composition of precipitation as recorded in ancient groundwater. Thus groundwater samples from a confined aquifer on the southern Cape coast show a marked rise in temperature since the Last Glacial maximum. The temperature changes during the Upper Pleistocene and Holocene are also reflected in the oxygen-18 content of stalagmites from the Cango caves in the same region. The widespread occurrence of C4 grasses in the warmer summer rainfall areas of southern Africa provides a novel possibility of observing temporal shifts of climatic boundaries. The distinctly high carbon-13 content of C4 plants is clearly reflected in the skeletons of grazers so that faunal material from suitably situated archaeological sites can be used to observe changes in the composition of the local grass-cover. The evidence thus far accumulated suggests only minor changes since the Upper Pleistocene. The combined evidence to date indicates that temperatures and also precipitation in southern Africa have changed since the Last Glacial maximum, about 18 000 years ago, but that shifts in the boundaries of the various veld-types were probably not very extensive.


Science ◽  
2010 ◽  
Vol 330 (6007) ◽  
pp. 1084-1087 ◽  
Author(s):  
J. Yu ◽  
W. S. Broecker ◽  
H. Elderfield ◽  
Z. Jin ◽  
J. McManus ◽  
...  

Author(s):  
L. Bezusko ◽  
S. Mosyakin ◽  
A. Bezusko

The article summarizes the results of quantitative paleoclimatic reconstructions conducted using different methods based on the palinological records of the Upper Pleistocene deposits of the plain part of Ukraine. Quantitative climatic characteristics for the Riss-Wurm interglacial period, Dubno interstadial and the Last Glacial Maximum are provided. It is concluded that primary refugia of thermophilic and hydrophilic trees on the plain areas did not exist during the Last Glacial Maximum. Key words: paleoclimatic reconstructions, Late Pleistocene, Riss-Wurm interglacial period, Dubno interstadial.


2021 ◽  
pp. 10-17
Author(s):  
Oguz Turkozan

A cycle of glacial and interglacial periods in the Quaternary caused species’ ranges to expand and contract in response to climatic and environmental changes. During interglacial periods, many species expanded their distribution ranges from refugia into higher elevations and latitudes. In the present work, we projected the responses of the five lineages of Testudo graeca in the Middle East and Transcaucasia as the climate shifted from the Last Glacial Maximum (LGM, Mid – Holocene), to the present. Under the past LGM and Mid-Holocene bioclimatic conditions, models predicted relatively more suitable habitats for some of the lineages. The most significant bioclimatic variables in predicting the present and past potential distribution of clades are the precipitation of the warmest quarter for T. g. armeniaca (95.8 %), precipitation seasonality for T. g. buxtoni (85.0 %), minimum temperature of the coldest month for T. g. ibera (75.4 %), precipitation of the coldest quarter for T. g. terrestris (34.1 %), and the mean temperature of the driest quarter for T. g. zarudyni (88.8 %). Since the LGM, we hypothesise that the ranges of lineages have either expanded (T. g. ibera), contracted (T. g. zarudnyi) or remained stable (T. g. terrestris), and for other two taxa (T. g. armeniaca and T. g. buxtoni) the pattern remains unclear. Our analysis predicts multiple refugia for Testudo during the LGM and supports previous hypotheses about high lineage richness in Anatolia resulting from secondary contact.


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