FEATURES OF NATURAL HYDRATION BY THE TYPES OF ARABLE LAND LOCATIONS OF THE SANAA BASIN

The aim of the study is to study the possibility of obtaining agricultural products from dry lands in arid climatic conditions of mountain areas, depending on natural moisture availability. The concept of types of arable land locations was introduced. The entire variety of locations of arable land in the Sanaa basin is divided into five types of locations depending on the location of a particular one or another form and relief element. The characteristics of the types of locations of the main wadi, intermountain basin, plain and other forms of relief of the Sanaa basin are given. The methodology for assessing the natural moisture availability of the types of locations of arable land of the main landforms was developed. Based on the materials of experimental field work on drain-forming sites and literary sources, the values of the runoff coefficients of the exits of indigenous rocks, loose eluvial, deluvial-proluvial and alluvial sediments of arable lands were determined and adopted for the calculation of natural moisture availability.

Shear-Type Mechanisms of Deformation Development in Structural Elements of a Deformation Relief

We studied basic structural elements of a deformation relief formed on lateral faces of nickel single crystals under compression. We correlated deformation heterogeneity with the type of structural elements of the relief. It was revealed that deformation heterogeneity did not depend on the type of a relief element or its scale. In addition, some studies were carried out to define ways of the deformation process in slip bands, mesa-and macrobands of deformation as well as in folds. It was found that a slip developed in separate slip bands resulted in their merging into micropackets with a slip occurring concurrently in several parallel planes. It led to the formation of a mesa-or macroscopic element of the deformation relief. We observed both intrusion and extrusion in the material in macrobands of [111]-single crystals as well as the formation of folding areas discussed.

Der Löß in Bulgarien

The loess in Bulgaria takes up an area of 9,800 km2 and is distributed exclusively in the section along the Danube. The loess forms a mantle over the pre-loessian relief surface forms — Pliocene denudation and sedimentation surfaces and Pleistocene river terraces. Loess formations overlie the Cretaceous, Tertiary and old Pleistocene deposits on the plateaux from which they are separated by a red-brown terra rossa-like clay weathering crust. On the terraces the loess overlies alluvial sediments of various ages, greater than its own age. The thickness of the loess formation depends on the distance from the Danube river and the age of the geomorphologic element which it overlies. On the plateaux in immediate proximity to the Danube river this thickness varies within the range of 50 and 60 m, loess walls reaching 102 m. The thickness drops to 25—30 m about 10 km south of the Danube, whereas in the southern peripheral parts it hardly reaches 4—5 m. The lithofacial composition of the loess formation changes with recedance from the Danube, the individual faciei differences being territorially manifested as narrow strips parallel to each other and to the Danube in the following order: loessial sand, sandy loess, typical loess, clayey loess and loessial clay. Loess stratigraphy is based on fossil soils, showing great stability with respect to number, type and territorial distribution. The number of loess horizons depends on the age of the relief element overlain by the loess complex and on the conditions favouring the preservation of the primary accumulation. The loess complex, overlying pre-Quaternary and Lower-Pleistocene forms of the relief, consists of 6 loess horizons, separated by 5 fossil soils; on the terrace of a relative height of 25—35 m (Riss/Würm I) it consists of three loess horizons, separated by two fossil soils and on the terrace of a relative height of 12—15 m (Wurm II) — by one loess horizon. On the basis of the available paleopedologic, paleontologic and pre-historic data and the principle of stratigraphic analogy we assume that the first loess horizon is deposited during Min-del I, the second-during Mindel II, the third-during Riss (I and II), the fourth-during Würm I, the fifth-during Würm II, the sixth-during Würm IIII, the second and third fossil soils being interglacial and the rest-interstadial. The studies conducted so far provide grounds to assume that the loess in Bulgaria is of eolian origin and terrigenous source — the overflooding of the Danube river.