THE CORRELATION POTENTIAL OF MAGNETIC SUSCEPTIBILITY AND OUTCROP GAMMA-RAY LOGS AT TOURNAISIAN-VISÉAN BOUNDARY SECTIONS IN WESTERN EUROPE

Investor logo

Warning

This publication doesn't include Faculty of Economics and Administration. It includes Faculty of Science. Official publication website can be found on muni.cz.
Authors

BÁBEK Ondřej KALVODA Jiří ARETZ Maecus COSSEY Patrick DEVUYST Francois-Xavier HERBIG Hans-Georg SEVASTOPULO George

Year of publication 2010
Type Article in Periodical
Magazine / Source Geologica Belgica
MU Faculty or unit

Faculty of Science

Citation
Field Geology and mineralogy
Keywords Outcrop logging techniques; foraminifer biostratigraphy; Carboniferous; deep-marine sediments; sealevel
Description We have measured five deep-water carbonate and carbonate-siliciclastic sections at the Tournaisian-Viséan (Tn/V) boundary in western Europe, using petrophysical outcrop logging techniques (gamma-ray spectrometry /GRS/ and magnetic susceptibility /MS/). The aim was to trace correlatable log patterns across the flanks of the London-Brabant Massif from eastern Ireland to western Germany. Both GRS and MS logging proved useful for long-distance (up to ~1000 km) correlation. The log patterns can be interpreted in terms of sea-level fluctuations. A late Tournaisian regression, a sequence boundary at the Tn/V boundary, early Viséan lowstand systems tract and an overlying transgressive to regressive succession can be identified from the GRS and MS logs. The Tn/V sequence boundary can be correlated with exposure features and karstic surfaces in the up-dip shallow-water settings at the boundary between sequence 4 and 5 of Hance et al. (2001, 2002). This indicates that sea-level fluctuations around the Tn/V boundary were synchronous and traceable on the flanks of the London-Brabant Massif. The GRS-based logging has a greater correlation potential than MS as it can be applied in a broad spectrum of facies and depositional settings. In certain sections, the MS signal shows an increasing trend during transgression and a decreasing during regression, which is opposite to the MS paradigm from shallow-water carbonate platform settings. These trends are assumed to result from landward/basinward facies shifts of a low-productivity carbonate ramp system. Lowstand shedding of carbonate tempestites and turbidites results in low MS values while during sea-level rise the ramp systems backstep, developing a retrograding facies succession in its distal parts, which is associated with upward-increasing MS values.
Related projects:

You are running an old browser version. We recommend updating your browser to its latest version.