How to deal with missing overburden - Investigating exhumation of the fragment of the Mid-Polish Anticlinorium by a multi-proxy approach

Tectonic inversion and erosion conceal basin geological history. As simple stratigraphic reconstructions can be inaccurate, thermal modelling techniques are often applied. In this paper, we show the advantages of a multi-proxy approach for exhumation studies, which explores full range of all possible solutions. The part of the Mesozoic Central European Basin that was inverted into the Mid-Polish Anticlinorium in the Late Cretaceous is chosen as a case study. The analysis consists of three steps: First, a wide range of possible geological scenarios is constructed, accounting for two alternatives of the overburden sequence, southern and northern, that result from the impact of the Holy Cross Fault on Mesozoic deposition. The second stage comprises apatite fission track and vitrinite reflectance analyses carried out on a similar to 1500 m long vertical profile, inverse modelling of these data to obtain thermal histories, and 1D thermal modelling of burial-erosion using the PetroMod software. In the third step, results of modelling exercises are combined with probabilities of the overburden variants to define an ensemble of the most likely geological scenarios. By applying this workflow we conclude that exhumation of the Mid-Polish Anticlinorium began in the latest Turonian-early Campanian and that similar to 1.7-2.3 km of uppermost Triassic Cretaceous rocks were removed. The heat flow was similar or slightly higher than the present-day value and during the Jurassic the study area was located on the northern side of the Holy Cross Fault, where deposition was faster. We also investigate the impact of elevated Late Palaeozoic heat flow on our samples and find that it was overprinted by high Late Cretaceous temperatures. All this is achieved by presenting the results as an ensemble of the most likely solutions within the wide modelling space.