Litostratygrafia dewońskiej serii stromatoporoidowo-koralowcowej w Górach Świętokrzyskich

Abstract

Ustanowiono formalną jednostkę litostratygraficzną, formację dolomitów i wapieni stromatoporoidowo-koralowcowych z Kowali, która obejmuje większość utworów organogenicznych zaliczanych do Żywetu i niższego franu w regionie kieleckim i w zachodniej części regionu łysogórskiego. W obrębie formacji z Kowali wydzielono 2 ogniwa: wapienia mikrytowego z Jaźwicy i wapienia masywnego z Kadzielni. Ponadto opisano 4 podrzędne jednostki nieformalne: warstwy stringocefalowe, chęcińskie oraz sitkówczańskie dolne i górne. Przedyskutowano wzajemne relacje i aspekty chronostratygraficzne opisanych wydzieleń oraz ich ewentualne rozprzestrzenienie poza regionem Świętokrzyskim. LITHO~TIGRAPHYOFTHEDEVO-STROMATOPOROID-CORAL CARBONATE SEQUENCE IN THE HOLY CROSS MOUNTAINSThe stromatoporoid-coral series forms an important member within the epicontinental Devonian sequence in the Holy Cross Mts (southern Poland); it is ascribed to the Givetian and lower Frasnian in the southern and western part of the area (Fig. 1). Most of the series is here included into the formal lithostratigraphic unit defined as the Kowala Formation built of coral-stromatoporoid dolostones and limestones, with total thickness ranging from 330 to 800 m. The formation consists mainly of skeletal in situ accumulations together with accompanying inorganic deposits, but excluding organodetrital limestones developed as fore-reef and reef-cap facies (Fig. 2). The lowest part of the formation is ascribed to the informal unit I (M. Narkiewicz, in press) some 80 m thick, and representing a sebkha sequence with a small proportion of biostromal deposits. Higher up, the informal Stringocephalus Beds are described, with thickness up to 230 m, containing several characteristic horizons of gray, almost unfossiliferous calcilutites with thicknesses exceeding 30 m. The Stringocephalus Beds are overlain by the Jaźwica Member built of micritic limestone. It is an important key horizon, from 2.2 to 13.1 m thick, developed as thin-bedded marly mudstones to packs tones bearing an exceptionally diverse faunal assemblage (cf. AG-level of G. Racki, 1986b). In the upper part of the Kowala Formation we define the Sitkówka Beds, the lower portion of which represents a top of the biostromal platform, while the upper one (Fig. 4) embraces areally restricted occurrences of the Frasnian reef-limestones (cf. M. Narkiewicz, 1988). In turn, the Kadzielnia Member, built of a massive limestone, represents Frasnian bioherms of variable size, occurring in the uppermost part of the Kowala Formation. In the southern part of the investigated area we define the Chęciny Beds with a considerable proportion of platy and nodular-like limestones, lacking any larger skeletal accumulations. Lower part of the Kowala Formation underwent dolomizatition which encompassed succesively higher lithostratigraphic units, from south to north: unit I, Stringocephalus Beds (central part of the investigated area), up to the Sitkówka Beds and the Kadzielnia Member (M. Narkiewicz, in press).