Possible origin of stromatactis-like cavities in Upper Jurassic sediments from the Wielkanoc quarry near Gołcza (Kraków-Czȩstochowa Upland, southern Poland)-experimental studies

Abstract

Isolated stromatactis-like cavities were found in a microbial-sponge buildup exposed in the Wielkanoc quarry (eastern part of the Kraków-Czȩstochowa Upland). The cavities are filled with several generations of carbonate cements and with internal sediments. The top surfaces of internal sediments are flat or wavy, whereas the roofs of cavities are arcuate. The origin of cavities from the Kraków-Czȩstochowa Upland is difficult to constrain. It seems that the stromatactis-like cavities from the Wielkanoc quarry resulted, at least partly, from remodeling of open spaces left after dissolution of corals in incompletely lithified sediment. Dissolution of corals disturbed the primary stress field within the carbonate buildup and generated the secondary stress characterized by the appearance of compressional forces in the walls of cavities and tensional forces in their roofs. Thus, the lack of support of sediments over roofs of cavities after dissolution of corals resulted in their instability and collapse triggered by vibrations caused by various factors. One of such triggers might have been the rejuvenation of the Kraków-Lubliniec Fault Zone in the Late Jurassic or the collapse of reticular framework within the buildup. The material falling down from the roofs was deposited at the bottoms of cavities as an internal sediment. Results of experimental studies demonstrate that the arcuate shapes of the roof surfaces of cavities are related to compressional stress in the walls and tensional stress in their roofs. © 2011 The Author(s).