Low-field magnetic susceptibility (MS) is a powerful tool that can provide information critical to paleoenvironmental and palaeoclimatological reconstructions and for stratigraphic correlations in the Paleozoic and younger rocks, but this method has never been fully applied to Neoproterozoic sedimentary rocks. Low-field magnetic susceptibility is based on the continental influx of detrital minerals in marine sedimentary basins, which act as a proxy for changes both in climate and sea level driven by glaciations or tectonic events. During eustatic sea-level rise, detrital supply decreases, and average low-field magnetic susceptibility values are therefore low, with the opposite when the sea-level drops. Low-field magnetic susceptibility was performed on 1,002 non-deformed and non-altered fine-grained carbonate rocks with a Kappabridge MFK1A device at room temperature in a low AC magnetic field of 400 A/m at the Royal Belgian Institute of Natural Sciences (Belgium). The average magnetic susceptibility (MS) values over along a distal–proximal gradient of the Mbuji-Mayi carbonates show a transition between a ramp system with high to low MS values from the deepest to shallowest facies respectively, and a platform geometry with intermediate to high MS values from the deepest to shallowest facies respectively. The transition is also marked by important changes of facies and sea level. These data are compared to the facies succession of the Lukala Subgroup that shows typical average MS values of a ramp. The results show a relevant relationship between magnetic susceptibility, facies and sequence stratigraphy that infer an environmental influence. Carbonate production, water agitation and organic content and diagenetic overprinting influenced magnetic mineral concentrations.
|Title of host publication
|AGU Fall Meeting 2019, 9-13 December 2019, San Francisco, California
|Published - 2019