Germany During the Glacial Periods

2019 ◽  
pp. 259-282
Author(s):  
Martin Meschede ◽  
Laurence N. Warr
Keyword(s):  
Glacial Periods

scholarly journals Manganese co-limitation of phytoplankton growth and major nutrient drawdown in the Southern Ocean

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Thomas J. Browning ◽  
Eric P. Achterberg ◽  
Anja Engel ◽  
Edward Mawji
Keyword(s):  
Southern Ocean ◽  
Drake Passage ◽  
Phytoplankton Growth ◽  
South American ◽  
Cold Temperatures ◽  
Continental Shelves ◽  
Ocean Productivity ◽  
Major Nutrient ◽  
Essential Function ◽  
Glacial Periods

AbstractResidual macronutrients in the surface Southern Ocean result from restricted biological utilization, caused by low wintertime irradiance, cold temperatures, and insufficient micronutrients. Variability in utilization alters oceanic CO2 sequestration at glacial-interglacial timescales. The role for insufficient iron has been examined in detail, but manganese also has an essential function in photosynthesis and dissolved concentrations in the Southern Ocean can be strongly depleted. However, clear evidence for or against manganese limitation in this system is lacking. Here we present results from ten experiments distributed across Drake Passage. We found manganese (co-)limited phytoplankton growth and macronutrient consumption in central Drake Passage, whilst iron limitation was widespread nearer the South American and Antarctic continental shelves. Spatial patterns were reconciled with the different rates and timescales for removal of each element from seawater. Our results suggest an important role for manganese in modelling Southern Ocean productivity and understanding major nutrient drawdown in glacial periods.

Neoproterozoic sedimentary facies and glacial periods in the southwest of Tarim Block

2013 ◽  
Vol 56 (6) ◽  
pp. 901-912 ◽  
Author(s):  
QinLong Tong ◽  
Wei Wei ◽  
Bei Xu
Keyword(s):  
Sedimentary Facies ◽  
Tarim Block ◽  
Glacial Periods

Late Quaternary deep marine sediment records off southern Africa

2021 ◽  
Author(s):  
H.C. Cawthra ◽  
E.W. Bergh ◽  
E.A. Wiles ◽  
J.S. Compton
Keyword(s):  
Southern Africa ◽  
Late Quaternary ◽  
Strongly Correlated ◽  
Sea Level Fluctuations ◽  
Proxy Records ◽  
Terrestrial Environments ◽  
Bottom Waters ◽  
Resolution Mapping ◽  
And Shifts ◽  
Glacial Periods

Abstract High-resolution mapping, sampling and analysis of upper Quaternary southern African continental margin sediments recovered from beyond the Last Glacial Maximum shoreline (>130 m water depth) have expanded our understanding of how marine and terrestrial records are linked over glacial-interglacial climatic cycles. This paper synthesises data currently available from the deep seafloor around southern Africa and, specifically, core sites that demonstrate terrestrial sedimentological connectivity. Several proxies and case studies reveal the evolution of depositional systems, palaeoceanography and palaeoclimate over the last 191 kyr. Hydroacoustic mapping and investigations of submarine canyons have been carried out primarily on the eastern and southwestern margins, while palaeoceanographic productivity and microfossil assemblages have been applied most extensively on the western marine and southern Agulhas Bank. Studies on the western margin indicate that enhanced productivity, less oxygenated bottom waters and reduced marine faunal diversity in the transition to glacial periods, while glacial terminations are associated with reduced productivity and more oxygenated bottom waters. These changes, linked to palaeoceanography and late Quaternary sea-level fluctuations, influence the sedimentary record and sedimentation rates. On the eastern margin, sediment fluxes applied as proxies for rainfall offshore of the Great Kei, Umzimvubu, Limpopo and Zambezi rivers indicate that the southern African climate responds to changes in orbitally-modulated insolation and in particular, to the ~23 kyr precessional cycle, where the proxy records keep pace with this and then diverge at ~80 to 70 kyr. Since the penultimate glacial (Marine Isotope Stage/MIS 6), more humid conditions observed in southern Africa, as the Northern Hemisphere entered phases of rapid cooling, were potentially driven by a combination of warming in the Agulhas Current and shifts of the subtropical anticyclones. Broadly, the sedimentary records reviewed suggest fluctuations in climate and oceanographic circulation that are strongly correlated with the global benthic δ18O record, suggesting sensitivity to high-latitude forcing, and a strong influence of late Quaternary glacial-interglacial cycles despite these marine sites being far-removed from terrestrial environments.

Finnmark Platform Composite Tectono-Sedimentary Element, Barents Sea

2021 ◽  
pp. M57-2020-20
Author(s):  
E. Henriksen ◽  
D. Ktenas ◽  
J. K. Nielsen
Keyword(s):  
High Frequency ◽  
Oil And Gas ◽  
Barents Sea ◽  
Upper Jurassic ◽  
Source Rocks ◽  
Basement Rocks ◽  
Sea Bottom ◽  
Middle Carboniferous ◽  
Uralian Orogen ◽  
Glacial Periods

AbstractThe Finnmark Platform Composite Tectono-Sedimentary Element (CTSE), located in the southern Barents Sea, is a northward-dipping monoclinal structural unit. It covers most of the southern Norwegian Barents Sea where it borders the Norwegian Mainland. Except for the different age of basement, the CTSE extends eastwards into the Kola Monocline on the Russian part of the Barents Sea.The general water depth varies between 200-350 m, and the sea bottom is influenced by Plio-Pleistocene glaciations. A high frequency of scour marks and deposition of moraine materials exists on the platform areas. Successively older strata sub-crop below the Upper Regional Unconformity (URU, which was) formed by several glacial periods.Basement rocks of Neoproterozoic age are heavily affected by the Caledonian Orogeny, and previously by the Timanide tectonic compression in the easternmost part of the Finnmark Platform CTSE.Depth to crystalline basement varies considerably and is estimated to be from 4-5 to 10 km. Following the Caledonian orogenesis, the Finnmark Platform was affected by Lower to Middle Carboniferous rifting, sediment input from the Uralian Orogen in the east, the Upper Jurassic / Lower Cretaceous rift phase and the Late Plio-Pleistocene isostatic uplift.A total of 8 exploration wells drilled different targets on the platform. Two minor discoveries have been made proving presence of both oil and gas and potential sandstone reservoirs of good quality identified in the Visean, Induan, Anisian and Carnian intervals. In addition, thick sequences of Perm-Carboniferous carbonates and spiculitic chert are proven in the eastern Platform area. The deep reservoirs are believed to be charged from Paleozoic sources. A western extension of the Domanik source rocks well documented in the Timan-Pechora Basin may exist towards the eastern part of the Finnmark Platform. In the westernmost part, charge from juxtaposed down-faulted basins may be possible.

scholarly journals Patterns of millennial variability over the last 500 ka

2010 ◽  
Vol 6 (3) ◽  
pp. 295-303 ◽  
Author(s):  
M. Siddall ◽  
E. J. Rohling ◽  
T. Blunier ◽  
R. Spahni
Keyword(s):  
Atmospheric Circulation ◽  
North Atlantic ◽  
Glacial Cycles ◽  
The North ◽  
The North Atlantic ◽  
Paleoclimate Records ◽  
Temperature Proxy ◽  
Freshwater Release ◽  
Glacial Periods ◽  
Climate Events

Abstract. Millennial variability is a robust feature of many paleoclimate records, at least throughout the last several glacial cycles. Here we use the mean signal from Antarctic climate events 1 to 4 to probe the EPICA Dome C temperature proxy reconstruction through the last 500 ka for similar millennial-scale events. We find that clusters of millennial events occurred in a regular fashion over half of the time during this with a mean recurrence interval of 21 kyr. We find that there is no consistent link between ice-rafted debris deposition and millennial variability. Instead we speculate that changes in the zonality of atmospheric circulation over the North Atlantic form a viable alternative to freshwater release from icebergs as a trigger for millennial variability. We suggest that millennial changes in the zonality of atmospheric circulation over the North Atlantic are linked to precession via sea-ice feedbacks and that this relationship is modified by the presence of the large, Northern Hemisphere ice sheets during glacial periods.

Distortion of Mountain Strata, Isostasy, and Glacial Periods

Nature ◽  
1938 ◽  
Vol 141 (3577) ◽  
pp. 906-907
Author(s):  
JOSEPH LARMOR
Keyword(s):  
Glacial Periods

scholarly journals Klimazeugen des periglazialen Dauerfrostbodens in Mittel- und Westeuropa: Ein Beitrag zur Rekonstruktion des Klimas der Glaziale des quartären Eiszeitalters

1960 ◽  
Vol 11 (1) ◽  
pp. 121-141 ◽  
Author(s):  
Karlheinz Kaiser
Keyword(s):  
Western Europe ◽  
Younger Dryas ◽  
Climatic Conditions ◽  
Border Zone ◽  
Patterned Ground ◽  
A Value ◽  
Outer Appearance ◽  
Glacial Periods ◽  
Glacial Time ◽  
Temperature Depression

Abstract. Certain periglacial phenomena (ice-wedges, cryoturbations, patterned ground, pingos) are critically investigated with respect to their outer appearance as well as to the causes of their formation, but especially how far they might be used as indicators of an old permafrost. The results for Central and Western Europe have been mapped according to our actual status of knowledge. The attempts hitherto made to reconstruct the climate of the Quaternary glacial periods, have been thoroughly checked. A new calculation of the maximum diminution of Pleistocene temperature gives a value of 15—16° C (bottom temperature) in Central and Western Europe. For the Younger Dryas we still have to expect a temperature depression of 11—12° C. Both values have been found by comparing mean annual temperatures in the border-zone of permafrost at the high-glacial time and during the Younger Dryas with the actual temperatures. This is true on the premise that the active permafrost area can be limited by the — 2° C annual isotherme, both under actual as well as under glacial climatic conditions.

Cryptic diversity in the smooth snake (Coronella austriaca)

2019 ◽  
Vol 40 (2) ◽  
pp. 179-192 ◽  
Author(s):  
Daniel Jablonski ◽  
Zoltán T. Nagy ◽  
Aziz Avcı ◽  
Kurtuluş Olgun ◽  
Oleg V. Kukushkin ◽  
...  
Keyword(s):  
Genetic Structure ◽  
Dna Sequences ◽  
Integrative Approach ◽  
Biogeographic Pattern ◽  
Western Palearctic ◽  
The Rich ◽  
Morphological Variants ◽  
Glacial Periods ◽  
Coronella Austriaca ◽  
Evolutionary Lineages

Abstract The smooth snake, Coronella austriaca, is a common snake species widespread in the Western Palearctic region. It does not form conspicuous morphological variants and, although several evolutionary lineages have been distinguished based on the analyses of the mitochondrial DNA sequences, only two subspecies with very limited distribution have been traditionally recognized. Here we present an mtDNA phylogeography of the species using geographically extended sampling while incorporating biogeographically important areas that have not been analyzed before, such as Anatolia, Crimea, and Iran. We find that the smooth snake comprises 14 distinct phylogenetic clades with unclear mutual relationships, characterized by complex genetic structure and relatively deep divergences; some of them presumably of Miocene origin. In general, the biogeographic pattern is similar to other Western Palearctic reptiles and illustrates the importance of the main European peninsulas as well as the Anatolian mountains, Caucasus, and Alborz Mts. in Iran for the evolution of the present-day diversity. Considerable genetic structure present in the smooth snake populations within these large areas indicates the existence of several regional Plio-Pleistocene refugia that served as reservoirs for dispersal and population expansions after the glacial periods. The current taxonomy of C. austriaca does not reflect the rich genetic diversity, deep divergences, and overall evolutionary history revealed in our study and requires a thorough revision. This will only be possible with an even higher-resolution sampling and integrative approach, combining analyses of multiple genetic loci with morphology, and possibly other aspects of the smooth snake biology.

Global biosphere primary productivity over the last 800,000 years reconstructed from the triple-isotope composition of dioxygen trapped in polar ice cores

2021 ◽  
Author(s):  
Ji-Woong Yang ◽  
Amaëlle Landais ◽  
Margaux Brandon ◽  
Thomas Blunier ◽  
Frédéric Prié ◽  
...  
Keyword(s):  
Primary Productivity ◽  
Isotope Composition ◽  
Atmospheric Oxygen ◽  
Ice Cores ◽  
Oxygenic Photosynthesis ◽  
Time Interval ◽  
Polar Ice ◽  
Future Evolution ◽  
Glacial Stage ◽  
Glacial Periods

<p>The primary production, or oxygenic photosynthesis of the global biosphere, is one of the main source and sink of atmospheric oxygen (O<sub>2</sub>) and carbon dioxide (CO<sub>2</sub>), respectively. There has been a growing number of evidence that global gross primary productivity (GPP) varies in response to climate change. It is therefore important to understand the climate- and/or environment controls of the global biosphere primary productivity for better predicting the future evolution of biosphere carbon uptake. The triple-isotope composition of O<sub>2</sub> (Δ<sup>17</sup>O of O<sub>2</sub>) trapped in polar ice cores allows us to trace the past changes of global biosphere primary productivity as far back as 800,000 years before present (800 ka). Previously available Δ<sup>17</sup>O of O<sub>2</sub> records over the last ca. 450 ka show relatively low and high global biosphere productivity over the last five glacial and interglacial intervals respectively, with a unique pattern over Termination V (TV) - Marine Isotopic Stage (MIS) 11, as biosphere productivity at the end of TV is ~ 20 % higher than the four younger ones (Blunier et al., 2012; Brandon et al., 2020). However, questions remain on (1) whether the concomitant changes of global biosphere productivity and CO<sub>2</sub> were the pervasive feature of glacial periods over the last 800 ka, and (2) whether the global biosphere productivity during the “lukewarm” interglacials before the Mid-Brunhes Event (MBE) were lower than those after the MBE.<br>Here, we present an extended composite record of Δ<sup>17</sup>O of O<sub>2</sub> covering the last 800 ka, based on new Δ<sup>17</sup>O of O<sub>2</sub> results from the EPICA Dome C and reconstruct the evolution of global biosphere productivity over that time interval using the independent box models of Landais et al. (2007) and Blunier et al. (2012). We find that the glacial productivity minima occurred nearly synchronously with the glacial CO<sub>2</sub> minima at mid-glacial stage; interestingly millennia before the sea level reaches their minima. Following the mid-glacial minima, we also show slight productivity increases at the full-glacial stages, before deglacial productivity rises. Comparison of reconstructed interglacial productivity demonstrates a slightly higher productivity over the post-MBE (MISs 1, 5, 7, 9, and 11) than pre-MBE ones (MISs 13, 15, 17, and 19). However, the mean difference between post- and pre-MBE interglacials largely depends on the box model used for productivity reconstruction.</p>

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