SEDIMENTARY PROCESSES PUBLISHEDGh. ROGOBETE, Adia GROZAV, R. BERTICI
Plate tectonics can explain the occurrence and formation of the entire catalogue of geological phenomena. There are intimate connections between air and water, and scientists tend to treat them as a single system. Earth’s geological history is a many – leaved volume, written by erosion, layer by sedimentary layer, in silt and sand on the ocean floor. Not all sands end up neatly stacked in wind – hewn dunes: up to a billion tons are blown into the atmosphere and scattered across the globe, every year, reaching Europe and of course Romania. Riding the trade winds, Saharan sand storms can cross the entire Atlantic, clouding the skies of Miami and even delivering mineral nutrients to the Amazon. In Romania, sand deposits are found on 400,000 ha, predominantly in Oltenia province (170,000 ha). On the west of Romania sands occur on 16,895 ha. But it is necessary to underline, that a great area with sand deposits are widely distributed under soil profiles. The research is based on some pedological studies effectuated in Romania, especially in the west part of the country by the authors of this article. When water or air flows over a bed of loose particles, the boundary shear stress tends to initiate particle movement. By fluid, sediment is transported in two distinct ways: in “suspension” (clay, silt, sand), and in “saltation” (sand particles). Wind blowing aer dry sand, initiates movement in much the same way as water. The result is that sands moved by air tend to be well sorted and also well rounded. In addiction, tectonic structures, like in Pannonian Sea, are often identical with syn-depositional structures. In the hilly zone, named Dealurile Lipovei, we present a soil profile – Luvosol stagnic (WRB – Stagnic Luvisols) bistratified, with A-El-Bt horizons, between 0 cm and 78 cm, and C horizon composed from sandy deposit with silt (23-24%) and clay (11%). The minerals which were found as new are epidote, zoisite, tourmaline and staurolite. They proceed from volcanic ash. The non-resistant minerals (biotite, hornblenda) changes with depth, whereas that of the quartz, feldspar and muscovite, remains nearly constant. The heavy resistant minerals present in the upper part of soil profile indicate stratification. In moderately weathered soils, the clay content and clay minerals are highest at the surface soil (0-60 cm) and disappeared in the sandy material (60-120 cm). There is a good correlation between the kind of clay minerals and the amount of rainfall or drainage conditions. Low rainfall and weak drainage, expandable minerals predominates(60-76%).
Erosional sedimentary, Depositional sedimentary, Aeolian processes, Alteration of minerals