scholarly journals Clay mineralogy of the Upper Paleocene and Eocene clay sediments in Denmark

1987 ◽  
Vol 36 ◽  
pp. 249-258
Author(s):  
Zhang Deyu
Keyword(s):  
Clay Mineralogy ◽  
Climatic Conditions ◽  
The South ◽  
Material Source ◽  
Clear Trend ◽  
Volcanic Material ◽  
The North ◽  
Great Belt ◽  
Upper Paleocene ◽  
Distinct Increase

The clay mineralogy of the Upper Paleocene and Eocene "plastic clay" sediments has been investigated from a new borehole in the Great Belt of Denmark. Predominant smectite, with small amounts of illite, kaolinite and, in the Holmehus Fm., chlorite, have been identified in the Upper Paleocene sediments. Abundant smectite and increased amounts of kaolinite and illite, with little chlorite, are present in the Eocene sediments. The Tertiary section of the borehole has been divided into two zones; one dominated by smectite with trace amount of kaolinite, including the Upper Paleocene and the Rl-R3 Beds of R!llsnres Clay Fm.; another characterized by the distinct increase of kaolinite and the relative decrease of smectite, including the R4-R6 and the Ll-lA Beds of Eocene sediments. Regionally, smectite content decreases, while kaolinite and illite increase from the north to the south and southeast in the Eocene sediments. No clear trend has been recognized in the Upper Paleocene sediments. The effect of material source, palaeoclimate and depositional environment on clay mineral distribution is discussed. The high content of smectite is considered to be mainly attributed to the alteration and/or weathering of volcanic material, contributions of smectitic clay from carbonate terrains and far trans­ported suspended matter from north-northwest. The change in climatic conditions may also be of importance. The distinct increase in kaolinite content of the Eocene sediments is thought to be related to a elastic source to the south and southeast and to the warmer climatic conditions.

Mineralogical evidence for sediment derivation and ice movement within the Wash drainage basin, eastern England

Clay Minerals ◽  
1985 ◽  
Vol 20 (2) ◽  
pp. 209-220 ◽  
Author(s):  
R. D. Wilmot
Keyword(s):  
Recent Work ◽  
Drainage Basin ◽  
Clay Mineralogy ◽  
The South ◽  
River Systems ◽  
The North ◽  
Glacial Periods ◽  
Mineralogical Evidence

AbstractThe Wash drainage basin contains four principal river systems. Samples were collected from the freshwater and estuarine reaches of each of these, and silt- and clay-grade fractions were separated and examined by XRD. The clay mineralogy of each of the rivers is different; in the north the Witham sediments contain chlorite, the Welland and Nene samples contain vermiculite, with a higher proportion of kaolinite in the former, while in the south the Ouse sediments contain smectite. The clay fractions of the samples from the estuarine reaches all contain chlorite, confirming that non-fluvial sources must contribute to the sediments of the Wash. Comparison of this pattern of clay mineralogy with that for the underlying Jurassic and Cretaceous rocks shows that there was relatively little modification during the Pleistocene glacial periods. Such a pattern supports recent work which suggests that ice moved through the Wash gap and then fanned out from the Fenland area, rather than entering the region from the north.

scholarly journals Analysis and revision of the Miocene boreal faunae of bivalve mollusks of the South Sakhalin

2020 ◽  
Author(s):  
В.Д. ХУДИК ◽  
Ю.Д. ЗАХАРОВ
Keyword(s):  
Japan Sea ◽  
Climatic Conditions ◽  
Bivalve Mollusks ◽  
The South ◽  
The North ◽  
Initial Stage ◽  
The Japan Sea ◽  
South Sakhalin ◽  
Early Neogene ◽  
Climatic Cooling

Приведены результаты изучения остатков фаун двустворчатых моллюсков из миоценовых отложений Южного Сахалина. Их анализ позволил выделить три бореальных комплекса моллюсков: невельский, раннечеховский и курасийский, фиксирующие периоды похолодания климата в миоцене региона. Изучение неогеновых представителей родов Lucinoma и Mya позволило обозначить среди них ряд таксонов, имеющих стратиграфическое значение. Установленное присутствие тепловодных двустворок в фаунах позднечеховского времени Южного Сахалина, очевидно, отражает собой начальный этап тенденции нарастающего потепления климата в миоцене региона с климатическим оптимумом в верхнедуйско-сертунайское время. Высказывается следующее мнение: неустойчивые климатические условия в позднем палеогене – раннем неогене северной части Япономорского региона могли быть основной причиной возникновения здесь одного из мощных центров эволюции морских малакофаун бореальных районов северной Пацифики. The results on the studying of the faunae of bivalve mollusks remains from miocene deposits of the South Sakhalin are presented. The analysis of the last ones allowed distinguishing the following three boreal assemblages of mollusks: Nevelskiy, early Chekhovskiy and Kurasiiskiy, recording the period of climatic cooling in miocene of the region. Studying of Neogene representatives of Lucinoma and Mya generas allowed identifying some taxa among them which have stratigraphic significance. The detected presence of warm water bivalves in the faunae of the late Chekhovsky time of the South Sakhalin appears to reflect the initial stage of the tendency of the intensifying climate warming happened during miocene, with climatic optimum during the Verkhneduysky – Sertunaysky times. An opinion is expressed that the unstable climatic conditions in the northern part of the Japan Sea region during late Paleogene – early Neogene could have been the main reason for originating of one of the high-potential centers of evolution of the marine malacofaunae of boreal regions of the North Pacific.

scholarly journals Reanalysis of 47 Years of Climate in the French Alps (1958–2005): Climatology and Trends for Snow Cover

2009 ◽  
Vol 48 (12) ◽  
pp. 2487-2512 ◽  
Author(s):  
Yves Durand ◽  
Gérald Giraud ◽  
Martin Laternser ◽  
Pierre Etchevers ◽  
Laurent Mérindol ◽  
...  
Keyword(s):  
Snow Cover ◽  
Snow Depth ◽  
Numerical Models ◽  
High Elevation ◽  
Climatic Conditions ◽  
Spatial And Temporal Variability ◽  
The South ◽  
French Alps ◽  
Mountainous Regions ◽  
The North

Abstract Since the early 1990s, Météo-France has used an automatic system combining three numerical models to simulate meteorological parameters, snow cover stratigraphy, and avalanche risk at various altitudes, aspects, and slopes for a number of mountainous regions (massifs) in the French Alps and the Pyrenees. This Système d’Analyse Fournissant des Renseignements Atmosphériques à la Neige (SAFRAN)–Crocus–Modèle Expert de Prévision du Risque d’Avalanche (MEPRA) model chain (SCM), usually applied to operational daily avalanche forecasting, is here used for retrospective snow and climate analysis. For this study, the SCM chain used both meteorological observations and guess fields mainly issued from the newly reanalyzed atmospheric model 40-yr ECMWF Re-Analysis (ERA-40) data and ran on an hourly basis over a period starting in the winter of 1958/59 until recent past winters. Snow observations were finally used for validation, and the results presented here concern only the main climatic features of the alpine modeled snowfields at different spatial and temporal scales. The main results obtained confirm the very significant spatial and temporal variability of the modeled snowfields with regard to certain key parameters such as those describing ground coverage or snow depth. Snow patterns in the French Alps are characterized by a marked declining gradient from the northwestern foothills to the southeastern interior regions. This applies mainly to both depths and durations, which exhibit a maximal latitudinal variation at 1500 m of about 60 days, decreasing strongly with the altitude. Enhanced at low elevations, snow depth shows a mainly negative temporal variation over the study period, especially in the north and during late winters, while the south exhibits more smoothed features. The number of days with snow on the ground shows also a significant general signal of decrease at low and midelevation, but this signal is weaker in the south than in the north and less visible at high elevation. Even if a statistically significant test cannot be performed for all elevations and areas, the temporal decrease is present in all the studied quantities. Concerning snow duration, this general decrease can also be interpreted as a sharp variation of the mean values at the end of the 1980s, inducing a step effect in its time series rather than a constant negative temporal trend. The results have also been interpreted in terms of potential for a viable ski industry, especially in the southern areas, and for different changing climatic conditions. Presently, French downhill ski resorts are economically viable from a range of about 1200 m MSL in the northern foothills to 2000 m in the south, but future prospects are uncertain. In addition, no clear and direct relationship between the North Atlantic Oscillation (NAO) or the ENSO indexes and the studied snow parameters could be established in this study.

scholarly journals Determination of ecological conditions and geographical distribution of vegetation in the Goksu basin

2022 ◽  
pp. 51-61
Author(s):  
Fatih Karaosmanoglu
Keyword(s):  
Geographical Distribution ◽  
Plant Species ◽  
Geographical Area ◽  
Climatic Conditions ◽  
Physical Factors ◽  
Climate Data ◽  
The South ◽  
Climate Type ◽  
Ecological Conditions ◽  
The North

On the ecological conditions and distribution of vegetation in any geographical area; The mutual interaction of factors such as climate (temperature-precipitation), topography (altitude-mountain extent), soil plays an important role. In addition, these factors also determine the ecological and geographical distribution of vegetation at micro and macro levels. In this study, geographic information systems (GIS) are used as a method and here; Digital elevation model of the basin (30x30), multi-year climate data (precipitation, temperature), Erinc climate type results, soil distribution, stand distribution, plant profiles and field photographs are the materials used in the study. By processing these data, the type and distribution of vegetation in the Goksu basin were determined. According to these findings, physical factors such as altitude and the extent of the mountains have created significant differences in the precipitation and temperature distribution of the basin. This difference was clearly observed in the Erinc climate classification results, and the south of the basin presented humid and semihumid climate characteristics, and the north presented semi-arid climate characteristics. These climatic conditions also affected the soil formation and type,causing a wide distribution of non-calcareous brown soils and non-calcareous brown forest soils in the field. As a result of all these conditions, plant species showed different vertical and spatial distribution. In the part from the south of the basin to Saimbeyli, plant species such maquis, pinus brutia, pinus nigra, Cedrus libani, Abies, Juniperus are distributed, while in the north, oak species such as oak, Bromus torhentallus, Astragalus, Thymus have been distributed. Thus, factors such as climate, topography and soil played an important role in the spread of vegetation and species in the Goksu Basin.

Environments of the Russian Plain during the Middle Valdai Briansk Interstade (33,000–24,000 yr B.P.) Indicated by Fossil Mammals and Plants

2002 ◽  
Vol 57 (3) ◽  
pp. 391-400 ◽  
Author(s):  
Anastasia K. Markova ◽  
Alexandra N. Simakova ◽  
Andrei Yu Puzachenko ◽  
Lev M. Kitaev
Keyword(s):  
Climatic Conditions ◽  
Russian Plain ◽  
Joint Analysis ◽  
The South ◽  
Mathematical Methods ◽  
Mammal Species ◽  
Forest Zone ◽  
Steppe Species ◽  
Natural Zones ◽  
The North

AbstractAbundant mammal (45 localities) and plant (52 sections) fossil data collected from the Russian Plain deposits of the Middle Valdai Briansk Interstade indicate a period of noticeable warming. These materials were jointly analyzed. The data were organized in the database software PARADOX and then moved to the GIS program ARC/INFO. Mathematical methods as well as traditional research methods were used for the analysis. The reconstructed biogeographical provinces illustrate the specific environmental and climatic conditions of the Briansk Interstade. Analogues of modern natural zones did not exist at this time on the Russian Plain. The Briansk landscapes reflect the moderate-cool climate of this period, when the majority of northern subarctic plant and mammal species extended their ranges considerably to the south to the Central Russian Plain. At the same time, steppe species penetrated farther north and west. This combination shows that the continuous forest zone was destroyed during the Briansk Inter-stade. Five biogeographical provinces have been reconstructed from the north to the south for the Russian Plain during the Briansk warming on the basis of joint analysis of mammalian and botanical data.

The relations between the South African fauna and the terrestrial and limnic animal life of the southern cold temperate zone

1960 ◽  
Vol 152 (949) ◽  
pp. 568-571 ◽  
Keyword(s):  
South African ◽  
Climatic Conditions ◽  
Temperate Zone ◽  
General Distribution ◽  
Pleistocene Glaciations ◽  
The South ◽  
The North ◽  
Early Tertiary ◽  
Species Groups ◽  
The Rich

In principle, the fauna of the southern temperate zone should present a general distribution pattern similar to that of the northern temperate zone. The rich invertebrate material preserved in the early Tertiary Baltic amber indicates that, at that time, the similarity was much closer than it is today. But during the Tertiary the cooling climate, in the north, resulted in the recession and extinction of many of those organisms which were rigidly fixed to a certain combination of environmental factors. The Pleistocene glaciations very effectively put a stop to the existence of many such invertebrate species and species groups whose relatives are now regarded as typical relicts. There is no doubt that the influence of the ice ages was comparatively small in the southern temperate zone of the Old World compared to what happened in the north. As regards the African continent it has been supposed that the highest areas in southern Africa, the Maluti Range in eastern Basutoland, at that time were covered with ice. But it was not so. On visiting that area we found that it has been free from ice, and moreover, that it is inhabited by an interesting, largely endemic fauna. Likewise, there is nothing indicating that the South Atlantic islands, the Tristan group and Gough Island, were capped with ice or carried isolated glaciers during the Pleistocene glaciations. Comparatively unchanged climatic conditions made the survival of the preglacial fauna possible.

Electrophoretic study of enzymes from cereal aphid populations. V. Spatial and temporal genetic similarity of holocyclic populations of the bird-cherry oat aphid, Rhopalosiphum padi (L.) (Hemiptera: Aphididae), in Britain

1988 ◽  
Vol 78 (2) ◽  
pp. 241-249 ◽  
Author(s):  
H. D. Loxdale ◽  
C. P Brookes
Keyword(s):  
Allelic Variation ◽  
Rhopalosiphum Padi ◽  
Climatic Conditions ◽  
Population Bottlenecks ◽  
The South ◽  
Cereal Aphid ◽  
Electrophoretic Study ◽  
The North ◽  
Genotype Frequencies

AbstractLarge colonies of holocyclic Rhopalosiphum padi (L.) were sampled in May-June in 1985 and 1986 from the principal host, Prunus padus, in various parts of Britain, mainly in the south-east. They were tested electrophoretically using nine enzymes representing 14 putative genetic loci. Only two loci (14%) were polymorphic (GOT, glutamate-oxaloacetate transaminase, and SORDH, sorbitol dehydrogenase), the remainder being monomorphic. Allele and genotype frequencies at each locus were generally similar both spatially and temporally, and genotype frequencies were close to Hardy-Weinberg expectations. The low level of genetic variability may reflect population bottlenecks which have purged most of the variation and which have been imposed by the distribution of P. padus, especially in the south of Britain where the tree is generally scarce. In addition, it is probable that adverse climatic conditions directly affect winter survival of anholocyclic populations of the aphid and thus also reduce variability. In the long term, such bottlenecks would tend to preclude the maintenance of effectively neutral enzyme variants that arise within populations. The similarity of allele and genotype frequencies may reflect the highly migratory behaviour of R. padi. Thus, in southern Britain, where P. padus is generally much rarer in comparison with the north of the country, R. padi inter-population gene flow is still sufficient to alleviate the influences of genetic drift and possible directional selection on the allelic variation that remains.

scholarly journals The Aptian evaporites of the South Atlantic: a climatic paradox?

2012 ◽  
Vol 8 (3) ◽  
pp. 1047-1058 ◽  
Author(s):  
A.-C. Chaboureau ◽  
Y. Donnadieu ◽  
P. Sepulchre ◽  
C. Robin ◽  
F. Guillocheau ◽  
...  
Keyword(s):  
Coupled Model ◽  
Climatic Conditions ◽  
South Atlantic ◽  
Arid Climate ◽  
The South ◽  
Drainage Pattern ◽  
The North ◽  
Central Segment ◽  
Seawater Salinity ◽  
Catchment Areas

Abstract. For a long time, evaporitic sequences have been interpreted as indicative of an arid climate. Such systematic interpretations led to the suggestion that the Central segment of the South Atlantic (20–0°) was characterized by an arid climate during the upper Aptian. Indeed, synchronous to this period that corresponds to the rifting and to the opening of this part of the South Atlantic, a large evaporitic sequence spreads out from the equator to 20° S. Using the fully ocean atmosphere coupled model FOAM, we test the potential for the Aptian geography to produce an arid area over the Central segment. Sensitivity to the altitude of the rift shoulders separating the Africa and the South America cratons, to the water depth of the Central segment and to the drainage pattern have been performed. Using seawater salinity as a diagnostic, our simulations show that the southern part of the Central segment is characterized by very high salinity in the case of catchment areas draining the water out of the Central segment. Conversely, whatever the boundary conditions used, the northern part of the Central segment remains humid and salinities are very low. Hence, we conclude that the evaporites deposited in the southern part of the Central segment may have been controlled by the climate favouring aridity and high saline waters. In contrast, the evaporites of the northern part can hardly be reconciled with the climatic conditions occurring there and may be due to hydrothermal sources. Our interpretations are in agreement with the gradient found in the mineralogical compositions of the evaporites from the North to the South, i.e. the northern evaporites are at least 4 times more concentrated than the southern one.

scholarly journals Spatiotemporal Changes of Reference Evapotranspiration in Mongolia during 1980–2006

2016 ◽  
Vol 2016 ◽  
pp. 1-14 ◽  
Author(s):  
Wenjun Yu ◽  
Tonghua Wu ◽  
Weizhen Wang ◽  
Ren Li ◽  
Tianye Wang ◽  
...  
Keyword(s):  
Hydrological Cycle ◽  
Reference Evapotranspiration ◽  
Kendall Test ◽  
Climatic Conditions ◽  
Meteorological Variables ◽  
The South ◽  
Sparse Vegetation ◽  
The North ◽  
The Mean ◽  
Aridity Indices

Reference evapotranspiration (RET) plays an important role in the terrestrial hydrological cycle. Applying the Penman-Monteith method, the RET over Mongolia was estimated from 1980 to 2006. The changing trends and magnitude of RET were detected by the Mann-Kendall test and Theil-Sen’s slope methods. Meanwhile, aridity indices were estimated using two different indices. The impacts of meteorological variables on RET were assessed through sensitive analysis by comparing the resulting RETs from artificially disturbed meteorological variables. The results indicated that the RET for 16 stations in Mongolia showed an increasing trend, particularly in the center and south. The calculated RET was higher than precipitation, which means severe droughts in Mongolia. The spatial patterns of RET are significantly influenced by climatic conditions as well as characteristics of the underlying surface (e.g., elevation and vegetation). The mean annual RET decreased from the south to the north, owing to sparse vegetation in the south of Mongolia. The sensitivity analysis revealed that the changes of RET were strongly affected by air temperature and relative humidity.

scholarly journals Mapping the distribution of Anopheles funestus across Benin highlights a sharp contrast of susceptibility to insecticides and infection rate to Plasmodium between southern and northern populations

2017 ◽  
Vol 1 ◽  
pp. 28 ◽  
Author(s):  
Rousseau Djouaka ◽  
Romaric Akoton ◽  
Genevieve M. Tchigossou ◽  
Seun M. Atoyebi ◽  
Helen Irving ◽  
...  
Keyword(s):  
Infection Rate ◽  
Anopheles Funestus ◽  
Climatic Conditions ◽  
Taqman Assay ◽  
Public Health Issue ◽  
Ecological Zone ◽  
The South ◽  
The North ◽  
Selection Factors ◽  
Southern Benin

Background. Malaria remains an important public health issue in Benin, with Anopheles gambiae s.l. and Anopheles funestus s.s being the predominant vectors. This study was designed to generate information on An. funestus distribution, molecular speciation, Plasmodium infection rate and insecticide susceptibility status across Benin. Methods. Mosquito samples were collected from December 2014 to January 2016 in 46 localities in Benin. These samples were mapped and An. funestus collected were speciated to the molecular level. Plasmodium infection rate was determined using a Taqman assay and susceptibility to insecticides was assessed using the WHO guidelines. The genotyping of the L119F- Gste2 mutation was also carried out. Results. An. funestus was found in 8 out of the 46 localities surveyed with a high presence in Tanongou (wet Sudanese ecological zone), Kpome, Doukonta and Pahou (sub-equatorial ecological zone). Molecular identifications revealed that only An. funestus s.s was present in southern Benin, whereas in Tanongou (northern Benin) An. funestus s.s. and An. leesoni were found in sympatry at proportions of 77.7% and 22.3% respectively. Plasmodium infection rate of An. funestus was higher in southern Benin at a range of 13 to 18% compared to 5.6% recorded in Tanongou. High DDT (8±0.5%) and permethrin (11±0.5%) resistance were observed in Doukonta, Kpome and Pahou, contrasting with relatively low resistance profiles: mortality-DDT=90±3.18% and mortality-permethrin=100% in Tanongou. Genotyping analysis revealed  high frequency  of the resistant 119F allele in the South (Kpome and Doukonta) compared to the North (Tanongou). Discussion and Conclusion. The high presence of  An. funestus in the South compared to the North  could be due to favorable environmental and climatic conditions found in both regions. A significant Plasmodium infection rate was recorded across the country. A high resistance profile was recorded in the southern Benin; this raises the need for further investigations on resistance selection factors.

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