Long-term variations in the flux of cosmogenic isotope 10Be over the last 10000 years: Variations in the geomagnetic field and climate

A spectral analysis of data on the flux of cosmogenic ¹⁰Be in ice core samples from the Central Greenland (project GRIP) over the last 10 thousand years have been carried out. It has been shown that the ¹⁰Be flux varies cyclically; the most significant cycle is of about 2300 years. Variations in the position of the virtual geomagnetic pole over 8000 years have been analyzed. Significant components, pointing to the cyclic variation in the position of the geomagnetic pole with a period of about 2300 years, have been revealed in a periodogram of the virtual geomagnetic pole longitude. In addition to the nearly 2300-year-long cycle, some lines are observable in the ¹⁰Be flux periodogram, which can be considered as a manifestation of the 1000-year-long cycle of the ¹⁰Be deposition rate on the ice surface. The relationship between the cyclicity of the geomagnetic pole position and the ¹⁰Be flux is discussed.     

Groundwater quality and rural drinking-water supplies in the Republic of Moldova

 This paper describes the results of a groundwater quality assessment conducted in two pilot areas, Balatina and Carpineni, in the Republic of Moldova. Shallow groundwater is the main source of drinking water in rural areas, but reliable data on its quality are currently insufficient for developing rural water-supply systems with standard designs. The main components of the study included a field sampling program (including pesticides), an evaluation of the reliability of existing drinking-water data, an analysis of land use and groundwater-pollution risks using GIS, and the formulation of recommendations to reduce risks for public health. Microbiological, nitrate, and selenium contamination are most serious in the villages. These contaminants should be given priority in addressing drinking-water aspects for rural water-supply development in the two pilot areas. Pollution occurs mainly due to poor sanitary conditions. In a few shallow wells, traces of selected pesticides were observed, but the effect of these levels of pesticides on public health is still unclear. Limited resources of shallow groundwater of good quality occur outside the villages. Additional pilot studies should be implemented to prove the technical and institutional feasibility of developing and protecting these resources. Received, September 1997 Revised, September 1998 Accepted, March 1999     

On M-Theory

This contribution gives a personal view on recent attempts to find a unified framework for non-perturbative string theories, with special emphasis on the hidden symmetries of supergravity and their possible role in this endeavor. A reformulation ofd = 11 supergravity with enlarged tangent space symmetry SO(1, 2) × SO(16) is discussed from this perspective, as well as an ansatz to construct yet further versions with SO(1, 1) × SO(16)^∞ and possibly even SO(1, 1)₊ × ISO(16)^∞ tangent space symmetry. It is suggested that upon “third quantization”, dimensionally reduced maximal supergravity may have an equally important role to play in this unification as the dimensionally reduced maximally supersymmetricSU(∞) Yang Mills theory.     

Ionospheric Disturbances due to the Influence of Localized Thermospheric Sources

Geomagnetism and Aeronomy - The paper presents the results of numerical modeling of the ionospheric disturbances from spatially localized, midlatitude, thermospheric sources that simulate the...     

The end of the Great Khersonian Drying of Eurasia: Magnetostratigraphic dating of the Maeotian transgression in the Eastern Paratethys

Central Eurasia underwent significant palaeoclimatic and palaeogeographic transformations during the middle to late Miocene. The open marine ecosystems of the Langhian and Serravallian seas progressively collapsed and were replaced in the Tortonian by large endorheic lakes. These lakes experienced major fluctuations in water level, directly reflecting the palaeoclimatic conditions of the region. An extreme lowstand of the Eastern Paratethys lake (?300 m) during the regional Khersonian stage reveals a period of intensely dry conditions in Central Eurasia causing a fragmentation of the Paratethys region. This period of “Great Drying” ended by a climate change towards more humid conditions at the base of the Maeotian stage, resulting in a large transgressive event that reconnected most of the Paratethyan basins. The absence of a robust time frame for the Khersonian–Maeotian interval hampers a direct correlation with the global records and complicates a thorough understanding of the underlying mechanisms. Here we present a new chronostratigraphic framework for the Khersonian and Maeotian deposits of the Dacian Basin of Romania, based on integrated magneto‐biostratigraphic studies on long and continuous sedimentary successions. We show the dry climate conditions in the Khersonian start at 8.6–8.4 Ma. The Khersonian/Maeotian transition is dated at 7.65–7.5 Ma, several million years younger than previous estimates. The Maeotian transgression occurs later (7.5–7.4 Ma) in more marginal and shallower basins, in agreement with the time transgressive character of the flooding. In addition, we date a sudden water level drop of the Eastern Paratethys lake, the Intra‐Maeotian Event (IME), at 6.9 Ma, and hypothesize that this corresponds to a reconnection phase with the Aegean basin of the Mediterranean. Finally, we discuss the potential mechanisms explaining the particularities of the Maeotian transgression and conclude that the low salinity and the seemingly “marine influxes” most likely correspond to episodes of intrabasinal mixing in a gradual and pulsating transgressive setting.     

Evaluation of deep crustal earthquakes in northern Germany – Possible tectonic causes

We present new evidence for seven deep crustal, intraplate earthquakes in northern Germany, a region regarded as an area of low seismicity. From 2000 to 2018, seven earthquakes with magnitudes of M_L 1.3–3.1, were detected at depths of 17.0–31.4 km. By placing the earthquake hypocentres in a geological three‐dimensional model, we can correlate two of the earthquakes with the Thor Suture, a major fault zone in this area. Five of the earthquakes group in the lower crust near the Moho, which implies that parts of the lower crust and the crust/mantle boundary in northern Germany act as a structural discontinuity on which deformation localizes. Numerical simulation implies that stress changes due to glacial isostatic adjustment most likely triggered these deep crustal earthquakes.