Székessy V. szerk.: A Magyar Természettudományi Múzeum évkönyve 41. (Budapest 1948)
Szurovy, G.: Geological structure of the Southern part of the Great Hungarian Plain
rally be made out. In their course disturbances caused by faults could very rarely be observed. The seismic measurements have shown that the subsoil of the basin lies at a considerable depth: 8,200—11,500 ft, and that the gravity structures mean an elevation as high as 3,281-—4,921 ft, below the surface. As an exception may be considered the structure of Madaras—Tompa, where the gravity diagram of the subsoil has been considerably influenced by the thick layers of miocene sediments. IV. The latest deep well drillings. On the structures determined by geophysical measurements 16 wells have been drilled. Their geological results are summed up in table II. On the structure of Biliarnagybajom 16 wells have been brought down by the counter flush method. The Trauzl equipment used here only allows drilling to a depth of 656 ft, which is not sufficient considering the lack of a marked key horizon. Therefore, the drilling of shallow wells has not been continued. From a geological point of view the drillings have very well confirmed the seismic measurements. They have shown that the smaller and larger basins forming the Great Plain are filed with very uniform sediments of considerable thickness. Coloured clay, marly clay and shaley marl beds alternate with thinner and thicker beds of fine sand, course sand and sandstone. In general we can state that the Pleistocene and Levantiian beds are characterised by the coloured clay, the upper Pannonian by tlie light gray and very sandy shaley marl, the lower Pannonian by the dark gray compact marly clay. The colour of the coloured clay varies from blue to bluish gray, greenish gray, greenish yellow, yellowish green, brownish green, brown and dark brown. It is unstratified, though, and contains rather thick lignite beds. The contents of calcium carbonate lias been frequently secreted and formed limy-marl concretions. The marl nodules can reach a considerable size; they are harder than their surroundings, and their colour is a light yellowish green or grenish gi-ay. The clays of the upper Pannonian are characterised by a predominantly gray colour and a more conspicious stratification. The contents of calcium carbonate increases a little, the rocks are full of