Reconstructing environmental signals across the Permian-Triassic boundary in the SE Germanic basin: Paleodrainage modelling and quantification of sediment flux

Abstract

Reconstructing sediment load in deep-time is one of the greatest challenges in the reconstruction of ancient sediment routing systems, particularly because solid statistical models are absent and paleo-climatic, paleo-tectonic, and sedimentary constraints are lacking. This study proposes a reliable workflow for the estimation of paleo-sediment fluxes (Qs) applying the BQART model to a case study from the SE Germanic Basin across the Middle Permian – Early Triassic interval. The input parameters of the simulations derive from: integrated plate modelling and structural kinematics; paleodrainage and paleogeographic reconstructions; global circulation models; and sandstone compositional signatures. We apply Monte Carlo simulation to overcome the input uncertainties for eight different scenarios obtained from the combination of two area estimates, two climate models, and two time resolutions. All the models are in general agreement and show changes in sediment flux (i) being steady or declining slightly through the Middle Permian, (ii) an increase of 31% at the beginning of the Late Permian (3.6–4.6 Mt yr−1), (iii) and a nearly 100% rise at the onset of the Early Triassic (7.4 Mt yr−1). The variation of sediment load across the PTB is coeval to the transition from meandering/sabkha to perennial braided depositional settings recorded from the well data of Obernsees-1 and Lindau-1; it results from both increased tectonism and seasonal precipitation. The Qs estimates agree with those of modern drainages under analogous environmental conditions, highlighting the reliability of the workflow included in this study for the quantification of sediment flux in deep time. Furthermore, the results of this study provide new insights on the highly debated evolution of the continental sequences across the PTB with strong implications for both past and future paleo-environmental reconstructions.