Post-Variscan tectonic and landscape evolution of the Elbe Fault Zone and the Lusatian Block based on apatite fission-track data and geomorphologic constraints

Abstract

The Elbe Fault Zone is a continental scale NW striking structure that contains faults of different kinematics. Some faults were active at different times since at least the Variscan orogenesis in the Late Carboniferous. The Lusatian Fault (LF) was one of the major structures of the Elbe Fault Zone in the Late Cretaceous, when NW striking faults of Central Europe experienced basin inversion and thrusting during a short lived pulse of contraction. The LF displays a curved appearance on earth surface, what is not compatible with its activity at only one well defined event. Possibly, different faults where active along strike of the LF at different times.Apatite fission-track thermochronology can distinguish differential exhumation or burial of neighbouring fault blocks, if the vertical difference comprised at least 1–2 km. This study presents apatite fission-track data from the footwall and the hangingwall block of the LF and some other faults in its vicinity. Our new data show a clear difference between the hangingwall block of the LF (the Lusatian Block) with uniform 70–85 Ma apparent ages and relatively long track lengths and the footwall-block of the LF with 66–173 Ma apparent ages and shorter and more variable track lengths. For one section of the LF, we can show, that the Cretaceous fault is not visible geomorphologically, but was substituted by a neighbouring Cenozoic reverse fault with a distinct fault scarp. We used thermal history modelling to determine the timing and magnitude of exhumation and burial events from apparent apatite fission track ages and track length distributions. We infer, that the present morphological expression of the LF consist of smaller faults of different kinematics and age and present an evolution model for this section of the LF.This study establishes the existence of similar striking reverse faults in direct vicinity and partly intersecting each other in the Elbe Fault Zone. This observation emphasizes the significance of the Elbe Fault Zone as a continental scale zone of crustal weakness. It has not only been reactivated several times since the Variscan orogenesis, but represents a cluster of similar striking faults of different age and kinematics.