The Moravian-Silesian region comprises the Upper Silesian black coal basin. The work to be reported deals with the study of palaeomagnetism of sedimentary rocks of the Upper Visean, Namurian A, and with the explanation of the origin of the so-called variegated layers with the use of petromagnetic and palaeomagnetic methods. It is above all roof slate, where the carrier of palaeomagnetization is finely dispersed pyrrhotite, which proved to be extraordinarily suitable for palaeomagnetic studies. The pole positions inferred on Carboniferous rocks in the Moravian-Silesian region fall into the pole positions so far inferred on Carboniferous rocks of the Bohemian Massif. It suggests the interpretation that the wider area of the Upper Silesian basin on the Moravian side was not much afflicted by palaeotectonic deformations although it is situated in the vicinity of the lithospheric boundary separating the North European Platform from the collision zone of the Alpine-Carpathian tectonic system. With the use of modified Thellier's method it was proved that the so-called variegated layers that form a large body in the area of the Orlov tectonic structure in the Upper Silesian basin correspond to typical erdbrands. These rocks came into existence in the post-Triassic period due to caustic alteration of Carboniferous sedimentary rocks, undoubtedly as a result of the self-combustion of coal seams in air conditions created by the existence of the Orlov tectonic structure.