Problem górnego turonu w kredzie dolnośląskiej

Abstract

THE PROBLEM OF THE UPPER TURONIAN IN THE LOWGR SILESIAN CRETACEOUS

Palaeontological investigations carried out along six sections of the Cretaceous of the Nysa trough made it possible to formulate the following conclusions. The Idzików marl may vertically be divided into two complexes of strata. The lower, complex is Upper Turonian (zone with Cardiaster planus). The higher complex to which the author limited the term "Idzików marl" is Lower Coniacian (zone with Inoceramus koeneni). The Idzików sandstone laid down on top of the Idzików marl, belongs to the Middle Coniacian (zone with Inoceramus involutus). In the author novel scheme; the Idzików marl comprises the rock. series of identical development of facies as well as the environment in which this series was formed. The Upper Turonian complex (thickness about 125 m.) consists alternately of layers of clayey-sandy marl and clayey marl; in the latter we observe, at times, beds of sandy limestone. The typically developed Idzików marl (of about 100 m. thickness) is deposited in distinct sedimentation cycles consisting of beds of sandstone clayey-sandy marl and clayey marl. At the termination of many of the cycles there developed fissures caused by loss of moisture (mudcraeks). At the bottom of the Idzików marl there occurs a horizon of 5-to, 10 m. thickness, built of clayey-siliceous marl. This latter marl is the facial correspondent of the so-called "zvonive opuki inoceramove" of the Bohemian Cretaceous. Along the base of this horizon there extends, in the Nysa. trough, the lower boundary of the Coniacian.·