Komplementarne strefy kataklazy w piaskowcach synklinorium północnosudeckiego
Abstract
CONJUGATE CATACLASTIC ZONES IN THE SANDSTONES OF THE NORTH-SUDETIC SYNCLINORIUM
Summary
Unusual conjugate cataclastic zones in the Buntsandstein and Coniacian sandstones of the North-Sudetic Synclinorium were described. Origin of these structures was interpreted as the result of the stress field connected with the Laramian folding of the area.
Two directions (NW-SE and WNW-ESE) of folds, joints and cataclastic zones were described. The possibility of the Reches's (10) model application for the explanation of this bimodality was suggested.
Various morphologic types of conjugate cataclastic zones were distinguished. The proposed classification is based on differentiated development of the shearing process.
Although shear zones with strong cataclasis can be as thick as 15 cm, no visible displacement was found (see Fig. on the cover). This fact can be explained by the stress hardening (sensu Aydin - 1) of the shear zone in porous sandstone. During repeating cyclic compression the „hard" cataclastic zones and the “weak” sandstone behave in different manner resulting in oscillative movements at the interface hard/weak rock. In this way the lateral growth of the shear. zones is performed.
No differences were found between the orientations of the cataclastic zones in the Buntsandstein and Coniacian sandstones. Occurrence of the conjugate cataclastic zones only in these two horizons can be explained by the position of the neutral plane in the folded sequence.
Summary
Unusual conjugate cataclastic zones in the Buntsandstein and Coniacian sandstones of the North-Sudetic Synclinorium were described. Origin of these structures was interpreted as the result of the stress field connected with the Laramian folding of the area.
Two directions (NW-SE and WNW-ESE) of folds, joints and cataclastic zones were described. The possibility of the Reches's (10) model application for the explanation of this bimodality was suggested.
Various morphologic types of conjugate cataclastic zones were distinguished. The proposed classification is based on differentiated development of the shearing process.
Although shear zones with strong cataclasis can be as thick as 15 cm, no visible displacement was found (see Fig. on the cover). This fact can be explained by the stress hardening (sensu Aydin - 1) of the shear zone in porous sandstone. During repeating cyclic compression the „hard" cataclastic zones and the “weak” sandstone behave in different manner resulting in oscillative movements at the interface hard/weak rock. In this way the lateral growth of the shear. zones is performed.
No differences were found between the orientations of the cataclastic zones in the Buntsandstein and Coniacian sandstones. Occurrence of the conjugate cataclastic zones only in these two horizons can be explained by the position of the neutral plane in the folded sequence.