Dinant czy missisip - o problemach podziału karbonu

Stanisław Skompski



According to recommendation of the lUGS Subcommission on Carboniferous Stratigraphy, the Carboniferous system is divided into 2 subsystems: Lower (approximately Mississippian) and Upper (approximately Pennsylvanian). The lower boundaries of the both subsystems have been defined biostratigraphically and La Serre (Montagne Noire) section has been proposed as GSSP for DIC boundary. The latter (so called "mid-Carboniferous") boundary is intensively investigated by Working Group of SCS, which is now seeking a potential stratotype section. In spite of an advanced stage in codification of Lower Carboniferous division, doubts connected with biostratigraphical markers of discussed boundaries still exist. Generally, they concern ortho- and parastratigraphic range of different groups of fossils (see fig. 2, 3). In Poland DIC boundary sequences are usually characterized by stratigraphical gap or condensation. In Cracow area, near Krzeszowice, the limestone sequence in boundary interval seems to be continuous (according to the sedimentological observations), but extremely shallow facies make biostratigraphical solutions very difficult. The higher, mid-Carboniferous boundary, most precisely could be indicated in the section of the Lublin Carboniferous Basin. This boundary could be located between 2 biostratigraphical levels: Posidonia corrugate I and P. corrugata II, which are characterized by goniatites of E2 and H1 zones. Unfortunately both intervals are represented by shale sequences, and therefore the conodonts are unknown from these complexes. The use of Belgian and British new stages, proposed in the lUGS stratigraphica1 chart as universal Lower Carboniferous stages, seems to be limited only to the carbonate facies in shelf of Northatlantic-Fennosarmatian Continent.

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