Revision of the geological documentation in the Křtiny Valley adits, Moravian Karst

Abstract

Four adits excavated in the Křtiny Valley in the early fifties were documented and sampled especially from the viewpoint of structural geology and of genesis and origin of the sedimentary infi llings. The studied localities include limestones of the Macocha Formation (Givetian of the Býčí skála cycle), Devonian clastics and granitoids of the Brno Massif (Neoproterozoic). Relativelly monotonous fold structure of the limestones is disrupted by a thrust zone imbedding sandstone and granodiorite tectonic slices into the limestone sequence. NW–SE striking thrust zone bears N–S trending striae suggesting its strike-slip character. The shear sense was not yet determined. This thrust zone was rejuvenated and extremely altered during younger faulting, so nowadays it has a clayish appearance. Most of the psammites sampled in limestone cavitties display a typical „Ottnangian“ or „Cenomanian“ translucent heavy mineral assemblage (staurollite, kyanite, tourmaline, rutil) which proves redeposition (vertical transport) from Ottnangian and Cretaceous sands.Four adits excavated in the Křtiny Valley in the early fifties were documented and sampled especially from the viewpoint of structural geology and of genesis and origin of the sedimentary infi llings. The studied localities include limestones of the Macocha Formation (Givetian of the Býčí skála cycle), Devonian clastics and granitoids of the Brno Massif (Neoproterozoic). Relativelly monotonous fold structure of the limestones is disrupted by a thrust zone imbedding sandstone and granodiorite tectonic slices into the limestone sequence. NW–SE striking thrust zone bears N–S trending striae suggesting its strike-slip character. The shear sense was not yet determined. This thrust zone was rejuvenated and extremely altered during younger faulting, so nowadays it has a clayish appearance. Most of the psammites sampled in limestone cavitties display a typical „Ottnangian“ or „Cenomanian“ translucent heavy mineral assemblage (staurollite, kyanite, tourmaline, rutil) which proves redeposition (vertical transport) from Ottnangian and Cretaceous sands