Climatic Phases Research Articles

Valanginian cold/warm climatic oscillation and synsedimentary tectonic interaction for drowning the carbonate platform of Southern Tethys (Sicily)

Valanginian is a deeply investigated time interval due to the climatic, environmental and oceanographic changes that characterised it, globally recorded in sedimentary successions.During the Valanginian, an oscillation between warm and cold climatic phases is generally accepted as causing change in sedimentation, especially along the carbonate platform successions. In this context the so-called “Weissert event” occurred.The analysed stratigraphic interval consists of a Valanginian–Hauterivian package of two black metallic crusts (hardgrounds) and condensed pelagites, interbedded in the Lower Cretaceous carbonate shallow-water succession outcropping in the Palermo Mountains (NW Sicily). Integrating facies, structural, mineralogical and geochemical analysis, including analysis of δ13C and δ18O isotope records, the interaction between synsedimentary tectonics and climatic changes, as causing palaeoenvironmental and palaeoceanographic changes in the Lower Cretaceous Panormide carbonate platform, has been envisaged.A regional extensional tectonic event in the Southern Tethyan margin was detected at the Berriasian/Valanginian boundary, as responsible for the tectonic fragmentation of the Mesozoic Panormide carbonate platform in various fault-blocks. Locally, tectonic subsidence caused drowning of some of the fault-blocks. Before the recovery of the benthic carbonate factory in the Barremian, condensed pelagites and mineralised (Fe–Mn) crusts developed during the alternation of warm and cold climatic pulses.The positive–negative excursions of the Valanginian–Hauterivian δ13C pattern of the Colombrina section provide solid evidence for the chronostratigraphic assignment of the study interval to the drowning of many carbonate platforms that preludes the onset of the “Weissert event”. In detail, the drastic negative shift of δ13C in the late early Valanginian mineralised crust reveals massive release of isotopically light carbon to the atmosphere/hydrosphere reservoirs from a possible excess of volcanogenic CO2 or methane release from clathrate dissociation. Combining sedimentological data with the increase of the δ18O isotope records, two cold climate pulses are envisaged. The first one is assigned to the Berriasian/Valanginian boundary and led to the formation of the lower mineralised crust. The second and more evident positive shift of δ18O is assigned to the earliest late Valanginian, during the sedimentation of the laminated pelagites deposited immediately after the upper mineralisation event. These cold events that are comparable with the coeval cooling pulses recorded at a global scale highlight icehouse interludes during the Lower Cretaceous greenhouse mode.

Neanderthal palaeoecology in the late Middle Palaeolithic of western Iberia: a stable isotope analysis of ungulate teeth from Lapa do Picareiro (Portugal)

ABSTRACTAdaptation to Late Pleistocene climate change is an oft‐cited potential contributor to Neanderthal disappearance in Eurasia. Accordingly, research on Neanderthal behaviour – including subsistence strategies, mobility, lithic technology, raw material procurement and demography – often focuses on linking changes observable in the archaeological record to specific phases of climate and environmental change. However, these correspondences are often tenuous because palaeoclimatic and archaeological records are rarely available on the same scale. In Iberia, a critical location for understanding the demise of Neanderthals, some research indicates that Neanderthal populations were unable to recover from environmental degradations known as Heinrich Events, while other studies suggest that enclaves of Neanderthal populations survived for several millennia longer in refugial zones. Here, we present a palaeoenvironmental reconstruction study using analysis of δ13C and δ18O of herbivore tooth enamel recovered from two Mousterian deposits at Lapa do Picareiro, a site located in Portuguese Estremadura. We then use these data, combined with other site‐based palaeoenvironmental indicators, to assess whether central Portugal acted as a refugium during periods of unfavourable climate, and to test whether Neanderthals in Portuguese Estremadura reorganised their mobility strategies after severe climate episodes.

Evolution of the Semideciduous-Riparian Forest (ecotone Cerrado-Atlantic Forest) during the late Holocene, Southeast of Brazil

The floodplains of meandering rivers in southeastern Brazil represent places where the sedimentary record associated with the history of transition/ecotone areas and exchange of biomes accumulates, such as the Cerrado (Cerradão Forest) and Atlantic Forest (Semideciduous-Riparian Forest). The present study aims to use palynological, isotopic (δ13C, δ15N and 14C), and anthracological indicators in cores taken from three abandoned meander bends to make inferences about environmental evolution, vegetation reconstruction, and climatic inferences. The study area is located in the Mogi Guaçu River Basin, in the countryside of São Paulo State. The studies show that ~2,730 BP (stage I), the area underwent through a more humid climatic phase compared to the current one, which allowed the expansion of the Riparian Semideciduous Forest. After that date, in stage II (1,800 to 510 BP), the percentage of the Cerrado (Cerradão Forest) increased, due to a drier period. From 510 BP to the present day (stage III), humidity has taken place with a new expansion of the Riparian Semideciduous Forest, although elements of Cerrado are present. Microscopic charcoal fragments were found in all stages and may infer the incidence of paleo-wildfires during the Late Holocene. The results indicate that both phytophysiognomies remained for the studied period, varying their expansion depending on the humidity present in each stage. Although lakes formed by abandoned meanders are not areas with the best palynological record, they are frequent environments in the interior of the continents. If properly interpreted, they may provide relevant information to vegetation and climatic changes for the areas. Keywords: paleoenvironmental studies, Holocene, river dynamics, pollen grains, isotopic analysis, charcoal fragments.

The late Quaternary stratigraphy of coastal dunes and associated deposits in southern Africa

Abstract Coastal sand dune sediments with associated intraformational aeolianite, palaeosols and beachrock are found throughout much of the southern African coast, and have important roles as both Quaternary environmental archives and in recording the interplay of sediment supply, coastal processes and sea-level change. This paper examines the stratigraphy and palaeoenvironmental significance of coastal sand dunes and associated sediments, using examples mainly from South Africa but also with reference to the sandy coasts of Namibia and southern Mozambique. Based on morphological, sedimentary and dating evidence reported in the diverse literature, the stratigraphic relationship of coastal sand dune sediments to Marine Isotope Stages (MIS) is summarized, and a chronostratigraphic diagram for the period MIS 6 to 1 along the South African coast is used to identify spatially coherent sedimentary units that correspond to different regional climatic and sea-level phases. This framework provides a stratigraphic context to better examine the relationship between coastal sand dunes and external forcing during the late Quaternary in southern Africa, and to guide future field studies.

A proposed chronostratigraphic framework for the late Quaternary of southern Africa

AbstractThe principles of chronostratigraphy can inform the process of correlation between different palaeoclimate records, enabling the coherence of spatial and temporal patterns of past climates and environments to be identified based on the physical, chemical, biological and isotopic properties of individual depositional units. This study presents a chronostratigraphic framework for the late Quaternary of southern Africa, based on the integration of palaeoclimatic and palaeoenvironmental proxy data from key records across the country from the start of Marine Isotope Stage 6 (~191 ka BP) to present. The methodology adopted in this study involves, first, wiggle-matching between sufficiently long and continuous records from different regions across southern Africa, informed by radiometric age controls from individual records. Based on interpretive limitations of these records, we then integrate different geomorphic and archaeological data types in proposing successive chronostratigraphic time periods that collectively extend through the late Quaternary of southern Africa. These time periods correspond to phases in which, within them, a certain set of (relative) stable climates or environments existed in different regions of southern Africa, as recorded in different ways in different proxy records. The boundaries between successive time periods are identified where there is evidence for a significant change in the workings of the climate or environmental system as reflected in the preserved proxy record found in a certain locality. These chronostratigraphic units are interpreted as reflecting the impacts of external forcing that is of regional extent, synchronous, and are not merely an outcome of local environmental variability. These chronostratigraphic phases identified for the late Quaternary period also correspond to distinctive technological and cultural phases in the southern African archaeological record, demonstrating links between coeval climate and environmental change and phases of human evolutionary development. This chronostratigraphic approach provides both a correlative framework for understanding the varied late Quaternary records of southern Africa, and a testable hypothesis for considering the synchroneity or otherwise of different records and thus their associated forcing factors.

Paleoclimate and paleoenvironment reconstruction of paleosols spanning the Lower to Upper Cretaceous from the Rukwa Rift Basin, Tanzania

The Cretaceous Period is considered the archetypical greenhouse interval, yet there is mounting evidence for intermittent cooler climatic phases throughout this geologic span. Few continental climate histories exist for the Cretaceous south of the paleoequator, and fewer still for Africa during this time. The Cretaceous Galula Formation is one of the few exposed fossiliferous continental sedimentary successions from what is now subequatorial Africa that also contains paleosols and spans both the Early and Late Cretaceous series. Bulk sediment and pedogenic carbonate nodules were sampled from paleosols located throughout ~500 m of the Galula Formation stratotype section, including four from the lower Mtuka Member (Aptian-Cenomanian) and four from the upper Namba Member (Cenomanian-Campanian), to reconstruct the paleoclimate and paleoenvironment of the Rukwa Rift Basin. The Mtuka paleosols developed on channel fill deposits in a semi-arid climate amidst well-defined wet and dry seasons that predominantly generated vertic Calcisols. Geochemical and morphological climofunctions determined that mean annual precipitation (MAP) increased up-section from 454 to 860 mm/yr, whereas the δ18O values of pedogenic carbonates and Bt horizon major-element paleothermometry estimated mean annual temperature (MAT) remained relatively steady, ranging between 12.9 and 13.9 °C throughout the Mtuka Member. The paleosols of the overlying Namba Member formed on channel fill and overbank deposits proximal to the main channels, in a semi-arid to sub-humid climate with little seasonality, forming mostly calcic Argillisols. The Namba paleosols formed under slightly wetter and cooler conditions, recording MAP values between 602 and 987 mm/yr, and MAT estimates between 10.3 and 12.5 °C. These data are consistent with the Mtuka paleosols corresponding to the cool greenhouse period that spanned the Aptian-Albian, with the Namba paleosols corresponding to Late Cretaceous cooling following the Cretaceous Thermal Maximum. This work demonstrates that temperate conditions prevailed in the Rukwa Rift Basin during the mid-Late Cretaceous.

2400 years of climate and human-induced environmental change recorded in sediments of Lake Młynek in northern Poland

Abstract. In the densely forested Warmia and Masuria region (northern Poland) there are many small endorheic lakes characterized by their low sedimentation rate, which makes them excellent archives of Holocene environmental and palaeoclimatic change. Lake Młynek, located near the village of Janiki Wielkie, was selected for multi-faceted palaeoenvironmental research supported with radiocarbon dates. Sediments from this lake also contain unique information about human impact on the environment, because a stronghold has been operating on its northern shore since the early Iron Age to the early Medieval period, giving the opportunity to correlate palaeoenvironmental data with the phases of human activity over the last 2400 years. During the second and third centuries BCE the lake was surrounded by a dense deciduous forest. From the first century BCE to second century CE the forest around the lake was much reduced, which can be associated with the first pre-Roman (La Tène) and Roman occupation phase evidenced by the construction of the stronghold located close to the lake. From the second up to ninth century CE gradual restoration of the forest and a decline in human activity took place, along with lake deepening and the onset of a colder and humid climatic phase which corresponded to the global cooling episode known as the Bond 1 event (1.5 ka BP). The next intensive phase of forest clearing around the lake occurred between the 9th–13th century CE as result of human activity (Middle Age settlement phase of the stronghold). Whilst this period is marked by a warming, the human impact which has transformed the landscape likely overprints any signals of climate-driven environmental changes.

Temperature Gradients Across the Pacific Ocean During the Middle Miocene

AbstractSea surface temperatures (SSTs) of the tropical Pacific Ocean exert powerful controls on regional and global climates. Previous studies have suggested that during warm climate phases, the east‐west temperature gradient collapsed. To date, there has been no high‐resolution reconstruction of sea surface conditions in both the east and west Pacific Ocean during the Miocene Climate Optimum (MCO) and across the middle Miocene climate transition (MMCT); therefore, our understanding of the mean oceanographic state during this major global climatic shift is limited. Here, we present new SST reconstructions for the eastern Pacific Ocean (15.5–13.3 Ma) which show a clear east‐west temperature gradient of ∼4°C during the warmest interval of the Neogene, implying that the oceanographic processes that produce the modern gradient were present and active. There is no shift in the east‐west gradient across the MMCT indicating that the gradient was not impacted by global cooling and ice growth. We find a 2°C sea surface cooling in the eastern equatorial Pacific, that lags the benthic foraminiferal δ18O positive shift by 150 kyr, indicating that tropical temperature did not decrease synchronously with the expansion of the Antarctic ice sheet. Reconstructed variations in the δ18O composition of seawater, determined by combining our Mg/Ca and δ18O records, reveal a freshening in the eastern Pacific Ocean after 13.8 Ma, suggesting changes in the hydrological cycle and in tropical fronts in response to the new icehouse regime.

Mid-Holocene Palaeoenvironment, Plant Resources and Human Interaction in Northeast Iberia: An Archaeobotanical Approach

The role of the adoption of farming economies in the transformation of mid-Holocene landscapes in Northeast Iberia is under discussion given that the Neolithization coincides with the cold climatic phase dated ca. 7500–7000 cal BP. The main aim of this paper is to assess whether human activities or climate were the main driver of vegetation changes during the Middle Holocene through the study of the archaeobotanical data from three case studies: Cova del Sardo, La Draga, and Coves del Fem. The application of diverse archaeobotanical techniques to the different plant remains provides a complete picture of the vegetation composition and plant uses. During the early Neolithic, settlement surroundings were intensively exploited for firewood, wood raw material, timber, and plant fibers. The resources were obtained mainly from deciduous and pine forests, depending on the site localization, but also from riparian zones. The diversity of plants exploited was high, not only trees but shrubs and herbs. Evidence of deforestation has been identified in the settlement surroundings in La Draga and Cova del Sardo. The combination of plant exploitation with other agropastoral activities favored the expansion of colonizing species and enhanced biodiversity at a local scale.

A small neighborhood well-organized: seasonal and daily activity patterns of the community of large and mid-sized mammals around waterholes in the Gobi Desert, Mongolia

BackgroundAnimal communities have complex patterns of ecological segregation at different levels according to food resources, habitats, behavior, and activity patterns. Understanding these patterns among the community is essential for the conservation of the whole ecosystem. However, these networks are difficult to study nowadays, due to anthropic disturbances and local extinctions, making it difficult to conclude if segregation patterns are natural or human-induced. We studied ecological segregation in a community of large and mid-sized mammals in the Great Gobi Desert, a remote arid area free from recent extinctions and human disturbances. Activity patterns of 10 sympatric mammal species were monitored around 6 waterholes through camera-trapping over a two-year period, and analyzed them primarily through circular statistics.ResultsComplex patterns of spatial, seasonal, and daily segregation were found. Overlap in seasonal activity was detected in only 3 of the 45 possible pairs of species. Four species used the waterholes all-year-round, while others peaked their activity during different periods. The Bactrian camel showed continuous daily activity, the grey wolf had bimodal activity, and the argali and Siberian ibex were diurnal, while the others had nocturnal peaks during different hours. Daily and spatial overlap were both detected in only 6 of the 45 pairs. Only one species pair (snow leopard and Eurasian lynx) showed an overlap at two levels: seasonal and daily. Climate and moon phase significantly affected the activity of certain species.ConclusionsAltogether, the results showed complex patterns of ecological segregation at different levels in the use of the key resource in arid environments: waterholes. These results are important for understanding the biology of these species under natural conditions, as well as potential changes in altered ecosystems, and may help to design conservation strategies.

Out of the extratropics: the evolution of the latitudinal diversity gradient of Cenozoic marine plankton.

Many ecological and evolutionary hypotheses have been proposed to explain the latitudinal diversity gradient, i.e. the increase in species richness from the poles to the tropics. Among the evolutionary hypotheses, the 'out of the tropics' (OTT) hypothesis has received considerable attention. The OTT posits that the tropics are both a cradle and source of biodiversity for extratropical regions. To test the generality of the OTT hypothesis, we explored the spatial biodiversity dynamics of unicellular marine plankton over the Cenozoic era (the last 66 Myr). We find large-scale climatic changes during the Cenozoic shaped the diversification and dispersal of marine plankton. Origination was generally more likely in the extratropics and net dispersal was towards the tropics rather than in the opposite direction, especially during the warmer climates of the early Cenozoic. Although migration proportions varied among major plankton groups and climate phases, we provide evidence that the extratropics were a source of tropical microplankton biodiversity over the last 66 Myr.

Sedimentary Ancient DNA From the Subarctic North Pacific: How Sea Ice, Salinity, and Insolation Dynamics Have Shaped Diatom Composition and Richness Over the Past 20,000 Years

AbstractWe traced diatom composition and diversity through time using diatom‐derived sedimentary ancient DNA (sedaDNA) from eastern continental slope sediments off Kamchatka (North Pacific) by applying a short, diatom‐specific marker on 63 samples in a DNA metabarcoding approach. The sequences were assigned to diatoms that are common in the area and characteristic of cold water. SedaDNA allowed us to observe shifts of potential lineages from species of the genus Chaetoceros that can be related to different climatic phases, suggesting that pre‐adapted ecotypes might have played a role in the long‐term success of species in areas of changing environmental conditions. These sedaDNA results complement our understanding of the long‐term history of diatom assemblages and their general relationship to environmental conditions of the past. Sea‐ice diatoms (Pauliella taeniata [Grunow] Round & Basson, Attheya septentrionalis [Østrup] R. M. Crawford and Nitzschia frigida [Grunow]) detected during the late glacial and Younger Dryas are in agreement with previous sea‐ice reconstructions. A positive correlation between pennate diatom richness and the sea‐ice proxy IP25 suggests that sea ice fosters pennate diatom richness, whereas a negative correlation with June insolation and temperature points to unfavorable conditions during the Holocene. A sharp increase in proportions of freshwater diatoms at ∼11.1 cal kyr BP implies the influence of terrestrial runoff and coincides with the loss of 42% of diatom sequence variants. We assume that reduced salinity at this time stabilized vertical stratification which limited the replenishment of nutrients in the euphotic zone.

A spatiotemporal gradient in the anthropization of Pyrenean landscapes. Preliminary report

A preliminary analysis of the timing of landscape anthropization in the southern-central Pyrenees shows the occurrence of an elevational gradient from the Bronze Age (basal belts) to the Middle Ages (alpine belts). This relationship is statistically significant and suggests an average anthropization rate of 40 m in elevation per century. The elevational gradient is most clear between the Bronze Age and the Roman occupation, suggesting a progressive upward anthropization trend from the south with the likely involvement of Iberian cultures. During the Middle Ages, a massive anthropization pattern of subalpine/alpine areas is observed; this pattern is chronologically consistent with the incursion of northern cultures crossing the Pyrenees and the development of extensive high-mountain pastoralism and horizontal transhumance. In general, the progression of upward anthropization has occurred during warm climatic phases. Further work is needed to confirm these observations, especially in areas with few available paleoecological studies, notably the basal and montane belts. It could be interesting to develop similar studies of other Pyrenean regions and other mountain ranges.

An uncertainty-focused database approach to extract spatiotemporal trends from qualitative and discontinuous lake-status histories

Changes in lake status are often interpreted as palaeoclimate indicators due to their dependence on precipitation and evaporation. The Global Lake Status Database (GLSDB) has since long provided a standardised synopsis of qualitative lake status over the last 30,000 14C years. Potential sources of uncertainty however are not recorded in the GLSDB. Here we present an updated and improved relational-database framework that incorporates uncertainty in both chronology and the interpretation of palaeoenvironmental data. The database uses peer-reviewed palaeolimnological studies to produce a consensus on qualitative lake-status histories, whose chronologies are revised and standardized through the recalibration of radiocarbon dates and the application of Bayesian age-depth modelling for stratigraphic archives. Quantitative information on absolute water-level elevation is preserved if available from geomorphological sources. We also propose a new probabilistic analytical framework that accounts for these uncertainties to reconstruct synoptic, integrated environmental signals. The process is based on a Monte Carlo algorithm that iteratively samples individual lake-status histories within the limits of their uncertainties to produce many possible scenarios. We then use Recursively-Subtracted Empirical Orthogonal Function analysis to extract dominant patterns of lake-status variability from these scenarios.As a proof of concept, we apply this framework to 67 sites in eastern and southern Africa whose lake-status histories cover part of the late Pleistocene and/or Holocene. We show that, despite the sometimes large temporal and interpretation uncertainties, and the inclusion of highly discontinuous lake-status time series, identifying the major known millennial-scale climatic phases during the last 20,000 years is possible. Our framework was also able to identify an antiphased response between the lake basins in eastern and interior southern Africa to these changes. We propose that our new database and methodology framework serves as a template for efficient lake-status data synthesis, encourages the incorporation of lake-status data in palaeoclimate syntheses, and expands the possibilities for the use of such data in the evaluation of climate models.

Holocene paleoenvironmental changes in the marginal marine basin of Great Rann of Kachchh, western India: Insights from sedimentological and mineral magnetic studies on a ∼60 m long core

We carried out sedimentological and mineral magnetic studies on a ∼60 m long core recovered from the central part of the Great Rann of Kachchh (GRK), a marginal marine basin, located on the western continental margin of India to understand the Holocene paleoenvironmental changes. We critically analysed the sedimentation pattern, sediment characteristics along with paleoclimatic signatures of global and regional relevance. In GRK basin, the sedimentation started in early Holocene (∼10.6–9.3 kyr BP) under rapidly rising post glacial sea level with very high sedimentation rate (8.71 cm/yr to 2.37 cm/yr) which is also seen in several marginal marine basins across the globe. The abundant laminations, coarse grained sediment flux and environmental magnetic parameters (χlf, S-ratio) suggests that the sedimentation occurred in developing monsoonal conditions under wetter yet fluctuating climate during this period. After ∼9 kyr BP, the environmental magnetic proxies show transition toward relatively wetter condition with peak at ∼6.5 kyr BP. This wetter climatic phase on the other hand corroborates with reduction of sedimentation rate to 0.46 cm/yr. This reduction in sedimentation rate under strengthening monsoonal conditions probably occurred due to rapid filling up of the basin on account of earlier high sedimentation in the basin. The sedimentation rate is reduced significantly after the onset of aridity at ∼4 kyr BP except a minor wet spell recorded during ∼1.5 to 1 kyr BP before drying of the GRK basin.

Деформационные тектонические волны как возможный триггерный механизм активизации эмиссии метана в Арктике

The authors consider a model of tectonic waves in the lithosphere, caused by the strongest earthquakes in the Aleutian subduction zone and propagating from it into the Arctic shelf and adjacent land areas. They demonstrate that changes in thermodynamic conditions at the boundary between the rigid lithosphere and viscous asthenosphere can generate traveling wave disturbances. The mechanism of this phenomenon is associated with the fact that the rate of movement of the base of the lithosphere, which is the solidus line, does not coincide with the rate of movement of its surface, and the viscous reaction of the asthenosphere becomes a function of the kinetics of the melting process. The emerging traveling tectonic wave generates a decrease in normal stresses in the near-surface layer of the earth’s crust, which, according to the L. I. Lobkovsky hypothesis, leads to the activation of methane emission from the accumulation zones of metastable relict gas hydrates and the onset of sharp warming phases of the actual climate in the Arctic.

The ecohydrological impact of water resource developments through inundation regime analysis of a large semi-arid floodplain

The ephemeral inundation of floodplains in semi-arid and arid zone climates is an essential driver of biological productivity. Natural biota depend on floodplain inundation to support critical reproductive life phases. In historical times, grazing industries have developed taking advantage of phases of high productivity associated with the overbank flow. However, the modelling of inundation in lowland floodplains is challenged by the complexity of topographic and hydrodynamic constraints. Here we apply a spatially explicit fine-scale inundation model to compare floodplain inundation regimes associated with current hydrological development on the Darling River floodplain, Australia, and pre-development, conceptualised as the removal of hydrological control structures. Our results suggest that hydrological developments in the Darling River catchment have substantially increased inter-flood period, an effect particularly pronounced during dry climatic phases. The result explains the decline in waterbird utilisation in this section of the Darling River, the low resilience of outer floodplain vegetation to the recent drought, and the reduction in grazing capacity. Water resource development had less impact on large inundation events.

Torn between Cultures: Reading Shashi Tharoor’s Riot

Shashi Tharoor is a distinctivevoice in the Postcolonial Indian literature in English with his remarkable contribution of more than 16 works of fiction and non-fiction. Postcolonialism refers to a set of theoretical concepts, approaches and interventions which deals with the diverse effects of the interaction between the colonizer and the colonized. History, politics and culture have always been a dominant preoccupation of the Indian English novelists. The compulsive obsession was perhaps inevitable since the genre originated and developed concurrently with the climatic phase of colonial rule. As a diplomat and writer, Shashi Tharoor has explored the diversity of culture in his native country. He has made his point in many of his interviews that the novel is full of collisions of various sorts- personal, political, cultural, emotional and violent. Riot is a novel about the ownership of history, about love, hate, cultural collision, religious fanaticism and the impossibility of knowing the truth. The novel chronicles the mystery of an American 24-year old lady, Priscilla Hart. The intention of this paper is to explore the cultural conflict between the East and the West and an attempt is made to examine Shashi Tharoor’s Riot as a conveyor of the various distinguishable features to the divergent cultures. The characters of Riot are facing problems and striving to achieve their identities as Indians and as individuals in Indian society. Lakshman, though an educated Indian, cannot share his intellectual ideas with any fellow Indians, but feels quite comfortable with Priscilla, an American lady. Yet, he cannot completely forego his Indian identity and is aware of their irreconcilable gap between their culture, values and outlook towards life.

Paleoenvironment and source-rock potential of the Cenomanian-Turonian Eagle Ford Formation in the Sabinas basin, northeast Mexico

The Cenomanian-Turonian Eagle Ford Formation is a widespread organic-rich mudrock in Texas and northern Mexico. The economic significance of this unit for oil and gas production in USA has led to numerous investigations documenting its lithological and geochemical variability. Comparatively little is known about facies distribution and source rock potential of this unit in Mexico. Here, we studied a section of the Eagle Ford Formation in the central part of the Sabinas basin. In order to evaluate the lateral continuity of the Eagle Ford Formation, and more specifically to gain understanding of the paleoenvironmental drivers of organic matter deposition and the hydrocarbon source source rock potential of this unit, we combined lithological, gamma-ray spectrometric, petrographic and organic geochemical data.Vertical distribution of main lithologic units and gamma-ray signal of the Eagle Ford Formation of the studied section match those documented in several sites from Texas, with the shale-dominated, bentonite-rich succession of the lower Eagle Ford showing the higher gamma-ray values, and the limestone-dominated succession of the upper Eagle Ford exhibiting moderate-high gamma ray values. Th/K and U/Th ratios suggest that the organic-rich lower Eagle Ford was deposited mainly during a warmer and more humid period, probably related to a sub-humid regional climate phase during the Cenomanian-Turonian global warming event, and under anoxic/dysoxic marine environments. Furthermore, a higher abundance of radiolarians indicates its deposition under nutrient-rich surface water conditions induced by upwelling currents. In contrast, these ratios support a less humid climate and oxic/dysoxic conditions during the accumulation of the upper Eagle Ford. Nevertheless, fluctuations of bottom water oxygen are evidenced by the occurrence of high TOC contents and bioturbated levels. Although TOC values throughout the Eagle Ford Formation point to a poor to very good source rock potential, both equivalent vitrinite reflectance (%VReq) and Tmax values indicate that the organic matter is overmature and has an exhausted hydrocarbon generation capability.

Late Quaternary vegetation and climate of SE Europe–NW Asia according to pollen records in three offshore cores from the Black and Marmara seas

High-resolution pollen analyses were performed on two cores from the western Black Sea and one core from the Marmara Sea, covering the Late Glacial-Holocene transition using 14C chronology. Particular effort was invested in the botanical identification of pollen grains thereby significantly improving our knowledge of regional flora. When interpreted with respect to modern vegetation, pollen records revealed all the major changes caused by climatic fluctuations over the last 20,000 years. The results of this study provide evidence for the occurrence of relict thermophilous-hygrophilous trees (papillate Cupressaceae, Carya, Liquidambar, Zelkova) in certain refugia up to the Holocene. Vegetation dynamics is specified for some taxa (e.g. Cupressus–Juniperus, Fagus, Cedrus) and some ecosystems (e.g. mesophilous forests, Mediterranean sclerophyllous populations, steppes). Pollen data enabled palaeoclimatic reconstructions which were compared with available estimates in the region. The use of a powerful pollen ratio between ‘thermophilous and steppe taxa’ led to fruitful climatostratigraphic relationships with the oxygen isotope curve from the NGRIP core. The Younger Dryas and cooling at 8.2 ka are among the most obvious climatic phases identified in the three cores studied here.