Provenance analysis of continental redbeds across the Permian to Triassic transition in SW Germany and NE France

In the southwestern, proximal Central European Basin system continental redbed deposition prevailed throughout Late Permian to Early Triassic time. The study aims at unravelling sediment provenance and drainage evolution based on heavy mineral (HM) data from 97 samples from the Black Forest, Palatinate Forest and the Vosges, covering ~10−12 Myrs from Zechstein to Upper Bundsandstein strata (Wuchiapingian to early Anisian). Further data include U-Pb ages and grain-size measurements of ~3000 zircons from 40 selected samples.

The HM spectra are rather uniform, dominated by the stable phases zircon, tourmaline and rutile (along with other TiO₂-phases) and complemented by variable apatite content as well as minor monazite. Zircon U-Pb ages range from ~0.25 to 3.5 Ga, showing prominent Variscan (30%), Caledonian (23%), Cadomian (28%) age components, and also older ages (19%). Grain-size data indicate overall decrease of zircon size with increasing zircon U-Pb age. The zircon age distributions suggest an increase of Cadomian and older ages at the expense of Variscan ages with decreasing stratigraphic age of the samples. This observation is independent of zircon grain size. It is interpreted to reflect a change from more local sources in Late Permian time to a significantly enlarged catchment area including tapping new sources. This comes along with a homogenization of sediment composition across the entire drainage and deposition area in the late Olenekian to early Anisian. The study serves as an example of HM-based fingerprints for regional-scale drainage basin widening due to relief planation in the aftermath of major orogenic phases.