Evidence of climatic warming in the southern Urals region derived from borehole temperatures and meteorological data

Thirty borehole temperature–depth profiles in the central and southern Urals, Russia were scrutinized for evidence of ground surface temperature histories. We explored two inversion schemes: a simple ramp inversion in which solutions are parameterized in terms of an onset time and magnitude of change and a more sophisticated functional space inverse algorithm in which the functional form of the solution is left unspecified. To enhance and potentially identify latitudinal differences in the ground surface temperature signal, we subdivided the data into three groups based on geographic proximity and simultaneously inverted the borehole temperature–depth logs. The simultaneous inversions highlighted 13 temperature–depth logs that could not both fit a common ground surface temperature history and a priori models within reasonable bounds. Our results confirm that this is an effective way to reduce site-specific noise from an ensemble of boreholes. Each inversion scheme gives comparable results indicating locally variable warming on the order of 1°C starting between 1800 and 1900 AD. Similarly surface air temperature records from 12 nearby meteorological stations exhibit locally variable warming also on the order of 1°C of warming during the 20th century. To explore the degree to which borehole temperatures and surface air temperature (SAT) time series are responding to the same signal, we average the SAT data into the same three groups and used these averages as a forcing function at the Earth's surface to generate synthetic transient temperature profiles. Root mean square (RMS) misfits between these synthetic temperature profiles and averaged temperature–depth profiles are low, suggesting that first-order curvature in borehole temperatures and variations in SAT records are correlated.     

Paleomagnetic studies of Paleolithic site deposits in the Matzuka Cave (Northern Caucasus)

As a result of detailed paleomagnetic and magnetic studies of Paleolithic site deposits in the Matuzka Cave, a record of the Matuzka geomagnetic excursion in lithologic layer 7 has been discovered and studied. Such characteristic features as the geomagnetic field direction, position of the virtual geomagnetic pole, geomagnetic field intensity (roughly estimated) after and during the excursion, and climatic conditions coeval with its existence make the Matuzka excursion similar to the ～130-ka Blake excursion. This dates at ～130 ka the formation of layer 7 with ancient archaeological findings.     

Variolitic lavas in the axial rift of the Mid-Atlantic Ridge and their origin (Sierra Leone area, 6°18′N)

Altered variolites described for the first time in the axial zone of the Mid-Atlantic Ridge are represented by rounded globules of andesite (icelandite) composition with light trachyandesite rim embedded in a picrobasaltic matrix. The globules were transferred with picrobasaltic melt and then floated to the surface of lava flow, while formation of leucocratic rims was presumably related to thermodiffusion (Soret effect) in a cooling heterogeneous melt. This heterogeneous melt was formed by penetration of ascending column of picrobasaltic magma in already existing small intracructsal magmatic chamber filled with residual icelanditetype andesite melt and involvement of the latter into a general upward movement. The rapid ascent of the melts in the oceanic spreading zones by means of turbulent flowing caused dispersion of the extragenous melt into small drops in a jet of picrobasaltic magma, without their interaction. Variolites were formed during cooling of such heterogeneous lava flow. No signs of liquid immiscibility were found in the studied variolites.     

Climate Change in the Urals,Russia, Inferred from Borehole Temperature Data

Borehole temperatures in the central and south Urals were analysed for the past ground surface temperature (GST) signal. 31 highquality temperature logs were selected for this purpose and inverted with algorithms based on the generalised least squares theory. The signal to noise ratio was improved by averaging the results of individual borehole inversions. No distinct regional trends were found in the studied region except for some indications of more pronounced warming in the south. The mean GST history (GSTH) was characterised by cooling down to –0.6 °C in the 18th century and subsequent warming to 0.5 °C above the longterm mean at the beginning of this century, and to 1 – 1.5 °C by 1980. The stability of the mean GSTH was tested in dependence on the number of holes used for the averaging. It showed that any subset of 15 holes yielded a GSTH similar to that obtained from the whole set. A surface air temperature (SAT) time series comprising the period 1832 – 1989 was combined from 17 meteorological records. Its least squares warming rate of 1.1 °C per 100 years is somewhat higher than that of the GST (0.7 – 0.8°C/100 years) in the same period.     

Geochemistry of granitic migmatites in the northeastern and southwestern Belomorian belt: An example of Karelia

Comparative petrological and geochemical characteristics are presented for the rocks from two areas in northern Karelia in the northeastern and southwestern parts of the Belomorian Mobile Belt. Both of the areas were determined to consist of plagioclase and plagioclase-microcline migmatites, plagiogranites, and granites, but the northeastern part is volumetrically dominated by plagioclase migmatites and plagiogranites corresponding to tonalites and trondhjemites in composition. The rocks of the southwestern part of the belt are rich in plagioclase and microcline. Based on the geological relations between the rocks and their petrography and geochemistry, it is demonstrated that the plagioclase migmatites of tonalite and trondhjemite composition were produced by the migmatization of amphibolites and differ from intrusive tonalites and trondhjemites. The rocks examined in both parts of the belt reveal a similar petrochemical and geochemical evolution with similar behaviors of major and some trace elements (except Ba and Sr), which were controlled by migmatization processes. Compared with the rocks of the northeastern part of the belt, those in its southwestern portion are enriched in Ba and Sr, with the differences in the behavior of these elements possibly controlled by variations in the depths at which the rocks were formed in different geodynamic environments.     

Magnetic and mineralogical characteristics of rocks at the Mezmaiskaya cave Paleolithic site (Northern Caucasus)

The results of magnetic and microprobe studies of the rock sequences in the Mezmaiskaya cave at the unique multilayer Paleolithic site are discussed. The magnetic properties of rocks are analyzed for 17 layers (upwards from layer 4 to layer 1\1) dated from over 73 ka ago to recent times. The rocks of layer 1C (Early Upper Paleolithic, ∼38 ka) are found to have the highest magnetic susceptibility (K) (up to 2500 × 10⁻⁶ SI), which is related to the intensive activity of [Homo sapiens]. The minimum K corresponds to the rocks of layer 2, which is overlain by layer 1D. The sizes of magnetic grains vary throughout the rock section. The largest grains are found in the middle part of the section in the Middle Paleolithic layers 2B3, 2B2, 2B1, 2A, and 2. The superparamagnetic fraction is identified in all layers. This fact supports the view that the cave was open as early as the formation of layer 4. According to the thermomagnetic data on the saturation magnetization and the temperature curves of magnetic susceptibility, magnetite is the main carrier of the rock magnetization; some samples contain iron hydroxides. Samples with iron sulfides (pyrite) are abundant. The study of the hysteresis parameters of rocks showed that the question on whether sulfide-bearing rocks are suitable for reliable paleomagnetic determinations requires further laboratory research into the origin of magnetite in the rocks. The chemical composition of rocks composing layer 2B3 and layers 1D (∼39 ka) and 2B1 (∼45 ka), in which the presence of volcanic ash has been previously established according to the presence of volcanic glass, was determined by detailed microprobe analysis. A wide variety of chemical elements (up to 18 items) was recognized in layers 1D and 2B1. The iron, titan, chrome, manganese content, and concentrations of other components vary from grain to grain. The microprobe analysis of samples from layers 1D and 2B1 revealed a set of magnetic particles with compositions characteristic of volcanic rocks, which supports the ash origin of these layers. Layer 2B3 is established not to be volcanic ash. The results on the volcanic glass in the rocks of layers 1D and 2B1 were published by Golovanova and her colleagues in Current Anthropology in October 2010 [Golovanova et al., 2010].     

Lithological and Geochemical Characteristics of the Paleocene/Eocene Sediments corresponding to the PETM Biospheric Event in the Eastern Crimea (Nasypnoe Section)

The paper reports lithological and geochemical data on the stratigraphic interval corresponding to the Paleocene/Eocene Thermal Maximum (PETM) event in the Paleogene section of Eastern Crimea (Nasypnoe section). The section is located on the western continuation of the sublatitudinal profile consisting of 15 PETM sections spanning the area from Crimea to Tajikistan (over 2500 km). It is shown that PETM sediments have the negative δ¹³C and δ¹⁸O isotope excursions and are enriched in kaolinite, which is typical of most sections of this interval around the world. At the same time, the extremely low content of organic matter (OM) in sediments of the Nasypnoe section makes them sharply different from the highly carbonaceous rocks of the PETM interval in Central and Eastern Caucasus, and Central Asian regions. This is correlated with the low contents of many chemical elements in the studied rocks, and their extremely high contents in the highly carbonaceous rocks of the easterly sections. Thus, Eastern Crimea in the end of the Paleocene?beginning of the Eocene was occupied by the low-bioproductive marine paleobasin, whereas the coeval paleobasin in Central Asia was characterized by extremely high bioproductivity owing to the presence of significant amount of phosphorus.     

Sedimentary environments and geochemistry of Upper Eocene and Lower Oligocene rocks in the northeastern Caucasus

Upper Eocene and Lower Oligocene rocks in the northeastern Caucasus were examined in the most representative Chirkei section (Sulak River basin). Sharp lithogeochemical distinctions between them were revealed. The results of the study of nannoplankton demonstrated that the Eocene/Oligocene interface occurs slightly below the boundary between the Belaya Glina and Khadum formations. The studied section revealed a series of nannoplankton bioevents facilitating its stratigraphic subdivision. It has been established that organic matter (OM) in rocks of the Khadum Formation is characterized by a relatively high degree of maturity. Probably, the material of mainly marine genesis contains a terrigenous OM admixture. Positive oxygen isotope anomaly in the upper part of the Belaya Glina Formation reflects global climate changes (cooling) near the Eocene/Oligocene interface. Limitation of the anomaly by the upper boundary of the Belaya Glina Formation is likely related to changes in water salinity variations in the Early Oligocene basin and intense early diagenetic processes in rocks therein. Lithological, geochemical, and paleoecological data suggest that the Khadum paleobasin was depleted in oxygen. Such environment was unstable with periodic intensification or attenuation. Paleoecology in the Belaya Glina basin was typical of normally aerated basins.     

Impact of Climatic Stresses and Volcanism on the Tendencies of the Cultural Process in the North Caucasus during the Late Pleistocene

Izvestiya, Atmospheric and Oceanic Physics - Multidisciplinary investigations into Paleolithic sites make it possible to identify all the main stadials in the Late Pleistocene history of the North...