ŚRODOWISKA SEDYMENTACJI ORDOWIKU GÓRNEGO W REGIONIE KIELECKIM GÓR ŚWIĘTOKRZYSKICH

Abstract

SEDIMENTARY ENVIRONMENTS OF THE UPPER ORDOVICIAN IN THE KIELCE REGION OF THE HOLY CROSS MTS.

Abstract. The spatial and temporal extent of the Upper Ordovician facies in the Kielce Region indicates regional tectonic controls on its distribution. The sedimentary basin was affected by differential subsidence rate, which probably originated from synsedimentary block faulting in the basement, that resulted in establishment of horst-like submarine palaeohigh with condensed carbonate deposition - grainstones, packstones to wackestons. During the Caradoc, the palaeohigh was bounded, to the south, by a deeper-water basin subjected to much stronger subsidence rate, where claystone facies were deposited. Periodically, the oxygen-deficient conditions occurred at the basin floor. From the latest Llanvirn to the early Late Caradoc the sedimentary and ecological conditions on the palaeohigh were affected by upwelling associated with the oceanic current that flowed south-eastwards along the northern margins of the Małopolska Block. The cessation of that oceanic current activity and then upwelling inflow was coeval with changes in palaeooceanographic circulation related to gradual closare of the western part of the Tornquist Sea during the latest Ordovician due to collision of the Avalonia with Baltica. The hydrodynamic conditions on the palaeohigh were dominated by interaction of storms and the oceanic palaeocurrent that together with slow carbonate production, resulted in low accumulation rate and subsequently in development of small starved seamount with a condensed carbonate sediment. During the end of the early Caradoc there was a rearrangement of the palaeohigh that resulted in establishment of a deeper water basin in the central part of the Kielce Region, with a continuous sedimentation in some places across the Silurian-Ordovician boundary. During the latest Caradoc and earliest Ashgill, the tectonic activity was intensified in the central part of the Kielce Region, resulting in uplifting of some parts of the basin floor, and subsequently a juxtaposition of the shallow and deep-water deposits in this area. The lithological expression of the Late Ashgill regression in the Kielce Region are clastic deposits (quartz wackes) accumulated by sandy debris flow derived from a fan delta.