Astronomical forcing of Carboniferous paralic sedimentary cycles in the Upper Silesian Basin, Czech Republic (Serpukhovian, latest Mississippian): New radiometric ages afford an astronomical age model for European biozonations and substages

Abstract

The similar to 3-km-thick Ostrava Formation in the foreland Upper Silesian Basin, which is located along the Czech Polish border, provides the thickest and most complete record of mixed shallow-marine to continental sediments of Serpukhovian (Carboniferous) age in the former equatorial Pangea. The coal-bearing strata of the formation show a prominent rhythmic architecture with similar to 200 faunal bands, of which approximately 80 contain marine fauna. Three new and three existing U-Pb zircon ages of intercalated volcanic tuffs measured using chemical abrasion isotope dilution thermal ionization mass spectrometry (CA-IDTIMS) allow for the calibration of rhythmic patterns of several orders. The genetic sequences show an average duration of 100 kyr, in line with orbital forcing by short eccentricity. This allows the astronomical tuning of these cycles in the Ostrava Formation to a time axis with a resolution of 100 kyr, providing temporal constraints on lithostratigraphic units, floral and ammonoid biozones, and West European substages. The Pendleian/Arnsbergian boundary defined at the base of the E2a ammonoid zone is now constrained to 325.9 Ma and the base of the Lyginopteris stangeri Zone at the base of the Ostrava Formation to similar to 329.2 Ma. The boundary of this zone with the subsequent L. larischii Zone corresponds to the base of the Jaklovec Member at similar to 325.8 Ma. The correlation of the major marine bands with equivalent bands in the Pennine Basin (England) and the Midland Valley of Scotland based on ammonoid faunas is suggested.