Transgresja dolnego tortonu na południowych stokach Gór Swiętokrzyskich (strefa zatok i ich przedpola)

Abstract

Lower Tortonian transgression onto the southern slopes of the Holy Cross Mts.

The problems of the Lower Tortonian littoral structures in the western part of the southern slopes of the Holy Cross Mts. (Central Poland) are dealt with in the present paper. Various types of mechanical littoral structures, among them abrasion and accumulation forms, have been distinguished and organogenic littoral structures with borings of various lithophags (sponges, polychaetes, pelecypods, cirripeds and echinoids), playing the most important role, examined in detail. The palaeogeography of this region have been reconstructed on the basis of the distribution of littoral structures. The Lower Tortonian transgression arrived here in an area with a varied terrain relief, encroached on the depression of valleys and transformed them into bays. The course of valleys was subsequent in relation to the Laramian tectonic structures (folds) and, consequently, the shores of the transgressing sea became Dalmatian in character. A zone of rocky bays, consisting of four largers bays and a forebay zone, has been distinguished from a general palaeogeographical picture of the marine basin here formed. The sedimentation, developing in ,bays and which resulted in a gradual filling of them with different shallow-water, clastic or carbonate sediments, has been discussed. Furthermore, the entire Lower Tortonian sedimentary cycle, which in the region studied begins with transgressive structures and deposits and terminates on forebays with chemical deposits (gypsum) which characteristic of evaporation and a gradual vanishing of this basin, has been examined.