Petrophysical record of the Late Silurian shallow-water carbonate facies across the Lau Event (Prague Synform, Czech Republic) and dynamic time warping alignment of the magnetic susceptibility logs

Abstract

Abstract High-resolution petrophysical logging magnetic susceptibility measurements (MS) and gamma-ray spectrometry (GRS), supplemented by rock magnetic measurements (anhysteretic and isothermal remanent magnetizations (ARM/IRM), frequency-dependent MS (FDMS)) and MS logs alignment using the dynamic time warping (DTW) algorithm, were constrained by upgraded conodont biozonation across the Lau Event interval (LEI). Two sections (Pozary and Muslovka) representing shallow-water facies in the Prague Synform were studied. Conodont data and DTW alignment show that Muslovka represents a less complete succession when compared to the Pozary. DTW alignment of the MS logs shows perfect match of the logs and detected six prominent and several minor gaps. MS logs show elevated values and triple peaks at both sections across the LEI which start in the uppermost part of the siluricus Biozone. Magnetite was identified as the main carrier of the MS signal at both sections using ARM and IRM. FDMS revealed occurrence of superparamagnetic (SP) particles at both sections in all selected samples. Furthermore, a higher contribution of SP particles to the MS signal is recorded below the Lau Event interval in the Pozary section. GRS logs show depletion in U concentrations across the LEI at both sections.