Subsidence and Outbursts - Instantaneous Outbursts of Carbon Dioxide in Coal Mines in Lower Silesia, Germany (With Discussion)

Instantaneous outbursts of carbon dioxide in coal mines have occurred in Germany only in one part of the Waldenburg-Neurode mining district.' This mining region comprises the northeastern fold of the "Innersudetian" coal basin. The basin (Fig. 1) is in the form of a geologic trough approximately 60 km. (37 miles) long and 30 to 35 km. (19 to 22 miles) broad and is enclosed on three sides by ancient truncated mountain ranges—the Riesengebirge, the Bober-Katzbachgebirge and the Eulenge-birge. Only the southeastern part of the trough is not enclosed by mountains of older rock formation. The floor of the basin before the building up of the coal measures was formed on the western, northwestern and northeastern borders by the material from Archean rocks (gneiss and mica schists); in the northern part over this was deposited the Silurian formation. The carboniferous period is represented both by the Lower ("kulm") and Upper Carboniferous, with an unconformity between the stages; that is, the kulm was tilted up and partly eroded before the Upper Carboniferous was deposited. The kulm is a salt-water formation (with marine fauna) but Upper Carboniferous rocks are nonsaline water deposits, with fresh-water flora only. The Lower Silesian coal measures were thus formed in a lime basin fed by the running water coming down from the mountains. As already indicated, the bottom series of the Upper Carboniferous formation, termed "Waldenburg strata" were laid down unconformably on the Lower Carboniferous. Over the Waldenburg strata there are the "Weisstein strata," an intermediate barren stage without coal beds, 400 to 500 m. (1300 to 1600 ft.) thick. Another unconformity followed, which is overlain by the '(Saarbrucken" series, which contain the upper coal measures, and the ('Ottweil" strata. In the last named, it is only on the southwestern fold that beds of coal are developed.