O rzekomej wkładce tufitowej z wiercenia Żebrak pod Siedlcami

Abstract

THE ALLEGED TUFFITE FROM BORE-HOLE ŻEBRAK NEAR SIEDLCEFrom the bore-hole Żebrak near Siedlce (Eastern Poland), W. Pożaryski and K. Lendzion (1960) have described as an tuffite layer a 50 cm. intercalation belonging to the Lower Maestrichtian.The petrographical and chemical investigation of this rock disclosed it to be a marly Cretaceous rock impregnated with a cement mortar, introduced into the bore-hole under pressure while pushing·down the tubing. In the rock sample the analysis in revealed components of Portland cement, thus an isotropis vitreous sub-stance in several kinds of structure (Figs. 3 and 4), identified by X-ray examination (Plate 2).The presence of this substance caused a misleading macroscopic resemblance of the rock, impregnated by cement, to tuffite. In the rock fissures, portlandite has crystallized in flat hexagonal plates of 0.20 to 0.06 mm. diameter (Fig. 1), determined on the basis of an X-ray picture (Fig. 2).After dissolving the whole rock sample in hydrochloric acid, the author identified in the sediment the following detritic minerals: quartz, pyrite, magnetite, tourmaline, and zircon.