Badania geologiczne warstw nadredenowych niecki bytomskiej

Abstract

Geological research on the super-reden strata of the Bytom Synclinal The mine „Saturn“ is situated 2 km east of the town Siemianiowice (Laura-Hiitte) in the Polish Coal Basin. The author is interested in the study of the super-reden strata and after the inspektion of geological conditions in this mine, he chose for special research the Field VI, where the complex of strata studied is best uncovered by the mining. From the tectonical point of view, this part is situated on the southern wing of the Bytom Synclinal and is intersected by a series of fault: the first one in the direction WNW—ESE (hercinian folds) and the second in the direction nearly N-—S. The first series of tectonic disturbances throws off the northern part of the mine towards its southern part by nearly 100 m. By this last phenomenon we can explain the fact that on relatively small space and an angle of the dip of strata oscillating between 2—10°, we find quite a high complex — the strata „Milowickie“ (conf. Fig. 1 and 2—6). The following problems were studied by the author: 1) A comparison of geological profiles of Field VI, with the aid of personal surveying and the use of detailed plans of subterranean survey. 2) A collection of actual material illustrating the geological profiles and a lithological description of the individual layers. 3) A study of the material by petrographical analysis in order to illustrate mineralogical correlations in the series of the complex of layer under discussion. 4) A study of the yet unknown fauna in the strata under discussion and a definition of paleontological levels on the basis of the results of the faunistical analysis. 5) As far as possible a construction of hypothesis regarding the character of the sedimentation rhythm based on the results of petrographical analysis and an explanation of phenomena connected with it. According to these problems a microscopic study of thin sections was made, which allows one to state that the minerals composing the sandstones under discussion come from different rocks: the grains of quartz show under the microscope their structure, such as inclusions of minerals, liquid and gaz; ondulating disappearance of light; often separate grains are constructed of individuals optically oriented in different directions. We also find eonjointments of rare minerals, such as garnet, turmaline, zircon, rutil and apatite. We must note that among the many thin sections (60) an individual of feldspars has been discovered, which has been included with the albite. We also note the interesting facti that in the neighbourhood of recent individuals of orthoclase there are feldspars so completely transformed, that they have retained only the original outline of grains. One may suppose that these ndividuals, so strongly transformed chemically, belong to the type of plagioclases, on which the presence of acids created by the decomposition of organic substances, acted more powerfully, than on the individuals of the orthoclase type. Next, the following analyses have been performed: mechanical analysis (Fig. 7), slime analysis (separation of slime by water) (Fig. 8) and mineralogical analysis (Fig. 9—11). The results of these analysis permitted the construction of diagrams, which showin percentage of weight and circumference, the mineralogical correlations in the different strata of the complex of rocks under discussion. It appears that these relations depend on the relative distance from the layer of coal, and make it possible to differenciate three zones which correspond to three phases of sedimentation. I. Strata of sandstone: (No of specimens 8, 25, 73, 86) (Fig, 3, 5, 6) a) the assortment of grains is unsatisfactory, b) relatively a large quantity of agilens, c) the grains are for the most part angular, d) there is a large quantity of heavy minerals (0'5—10%) (except No. 73), e) amount of other components: Quartz — the quantity of which oscillates between 7 — 34% Feldspars — usually found between 1'5—2'5%, Muscovite — relatively more than biotite, Calcite — very small percentage or none at all, Chlorite — relatively a large quantity, Pirite — a large quantity depending on the degree of decomposition of the rock, Hydroxide of irons — group around half decomposed minerals. II. Strata of sandstone: (No of specimens 15, 17, 19,93) (Fig. 4) a) the assortment of grains is good (the grains have a diameter from max. 01 mm — 34, b) relatively a large quantity of agilens, c) grains with rounded edges are more frequently found, d) amount of heavy minerals is the largest, 053— 1 '4%, e) amount of other components: Quartz — the quantity oscillating between 15—23%, Feldspars — reach up to 8%, Muscovite — increases quantitatively upwards to 3%, Biotite — stays in equal relation to Chlorite, Calcite — increases quanitatively upwards 7--12%, (No. 93 excepted), Pyrite — quite a large amount up to 1%, Hydroxide of iron — relatively few. III. Strata of sandstone: (No of specimens 10, 12, 12a, 13, 14) (Fig. 4—5) a) the assortment of grain is very good (the strata contains 34—42% of grains which have a diameter of 0’2—01 mm), b) the quantity of agilens decreases considerably, c) the grains with rounded edges are predominant, d) the amount of heavy minerals is insignificant (0'05—0‘2%), e) amount of other components: Quartz — quantitatively oscillating between 20 — 30%, Feldspars — reach up to 14%, Muscovite — decreases upwards, the greatest amount found in No. 12, Biotite — its quantity stays on the average in a stable relation of 0'25— 1%, Chlorite — quantitatively decreases upwards, its largest amount in No. 12, Calcite — appears quantitatively little, Pyrite — its small quantity does not exceed 0'38%, Hydroxide of irons — appear very little. These zones with the different mineralogical correlations allow us to judge the conditions .of sedimentation, which underwent gradual changes, in connection with orogenic movements in the sphere of which lay the Polish Basin. The series of rocks under discussion, in the section of one rhythm of sedimentation (i. e. between two strata of coal) has to be divided into zones and into corresponding separate sedimentation phases. I-st Phase — erosion, absence of sediments, interruption in sedimentation. II-d Phase — abundant sedimentation, assortment of material according to diameter of grains is unsatisfactory. On account of strong but uneven currents heavy minerals become distributed irregularly, but comparatively abundantly in the rock. III-d Phase — even sedimentation, assortment of material acording to diameter of grains is good, as a result of stable and even currents of water. (Probably because the zone of influence of the transgression caught the better assorted material). The strata are poorly provided with heavy minerals. IV-th Phase — weakened transgression, the assortment of grains is good, the material is smaller, enrichment of strata in heavy minerals. V-th Phase — stagnation, a gradual diminution of the strength of the current, the sand — loam — materials gradually drop grains of quartz, and the heavy minerals; growing rich in organic materials: shale with coal inclusions, formation of coal strata and of shale with remains of carbonized plants. The author observed the phenomena caused by the action of the first two phases of sedimentation in the upper part of the coal strata „Ignacy“ (Fig. 15,16 and 17) and „Fanny“ (Fig. 18), where we see undeniable examples of transgression and erosion of the upper strata. The given curves (Fig. 12 and 13) show the percentage (Fig. t2) of clear sand material on one hand, and the percentage of garnet (Fig. 13) which constitutes about 95% of the amount of the heavy minerals in the individual parts of the profile of the 30 m thick complex of rocks under discussion. At a first glance we see that the relation between the percentage of sand material and the heavy minerals (garnet), is reverse in the different parts of the profile; with the exception of the strata of shale where the action of water had almost disappeared. A comparison of the results furnished by faunical analysis allows us to fix the paleontological levels. St. Czarnocki divides in his study the strata situated over the stratum „Reden“ into two parts. To the first part, which is the highest, I include the strata of the studied complex, and on the basis of the fauna heretofore unknown, which 1 have discovered and studied, I differentiate three palaeontologic levels (Fig. 1). I Horizon. Shale, 0 55 m. Anthracomya laevis, Anthracomya cf: minima and Spirorbis sp. together with many remains of Stigmaria, lies 3' 10 m under the layer „Nadmilowicki 1“. (Fig. 2 No. 36). II Horizon. Black slate 0'05 m, with the flora with the : Carbonicola aquilina, Anthracomya cf., Valenciensis, Anthracomya cf., laevis in the vaulting of the layer „Nadmilowicki 1“. (Fig. 2 No. 46 and 47). III Horizon. Light, slime — sand — limestone, 025 m, with Cypricardella annae 3‘60 m, under the layer „Nadmilowicki 11“. The flora of this stratum does not contain remains of leaves of continental plants and Stigmaria, but can be classified most accurately with chopped aquatic plants. I consider this to be a sea level (Fig. 2 No. 63). The enclosed scheme (Table 14), worked out by St. Czarnocki , has been supplemented by the author in the chapter „Paléontologie Levels“, according to the results of research to date. F. Rutkowski in his recently published study discusses the problem of the discordance between the synclinal, the anticlinal and the border groups, and draws the conclusion that actual material is lacking, which undoubtedly would prove those discordances. F. Rutkowski quotes authorities on the sea fauna of the anticlinal group strata, which in spite of the divergence of opinion between Michaelon one hand, and Roemer, Quitzow and Cossmann on the other, forces him to accept the opinion that there is no clean cut faunical boundary. From this he draws the conclusion about the tectonical discordance, and he adds that Goth an, in his study of Flora boundaries mentions that these phenomena are accompanied by a total change of the conditions of the sedimentation and changes in the pétrographie character of the rocks. Notwithstanding the strong florical differences, as the most probable result of a change in the paleogeographic conditions, one cannot agree to the opinion of Goth an concerning the change of the pétrographie character in the separate parts of the upper carbon in the Polish Basin. The results of pétrographie analysis of this study allow us to state the pétrographie similarities of rocks and the identity of minerals in the chief heavy minerals which compose the interlayer — strata of the parts of upper carbon: at any rate these differences are, till now, unperceivable. It is impossible to state a change of the sedimentation conditions. The appearance of conglomerates and of thick — grained sandstones lying immediately over the series of the layers „Reden“, cannot be considered as a discordance between those groups of carbon; we may consider it as the phenomenon of a certain rhythm of sedimentation, probably having a larger amplitude, because such interruptions in sedimentation on a smaller scale must have followed the formation of every layer of coal. The results of fauna analysis cannot give rise to a statement about the existence of an important palaeozoological difference in the sphere of upper carbon. Next to sweet water forms, such as Anthracomya and Carbonicola we find specimens of Spirorbis on the shell of Anthracomya laevis. Above the II horizon with the Carbonicola aquilina, at a distance of only a few meters, is situated the III horizon with the Cypricardella annae — a form known from the carbon limestone of England and the flora which most probably belongs to remains of aquatic plants. This conjointment points to the fact that we are dealing with a sea level. Reviewing the considerations based on actual geological material; on petrographic analysis, which shows the identity of the material composing the rocks under discussion, in connection with which the hypothesis about the phases of sedimentation — rhythm are right, — and on the fauna analysis which states the discovery of both sweet and salt water flora, in the synclinal group of upper carbon — the author draws the following conclusions: 1) There is no discordance between the individual parts of upper carbon in the Polish Basin. 2) The sedimentation was constant and its rhythms can be divided into phases. 3) The fauna discovered in the strata of the synclinal group, altough differing from the formation of the lower parts, shows nevertheless a mixed formation which is characteristic of the fauna of the paralical basins of Europe. 4) The transgression of the sea on the territory of the Polish Basin took place at the time of the formation of Upper carbon in its lower and middle period.