Resolving Sedimentological Uncertainties Using Magnetostratigraphic Correlation: An Example from the Middle Jurassic of Burgundy, France

Abstract

ABSTRACT Magnetostratigraphic analysis was undertaken on a core 85 m long core from the shallow-water carbonate platform of Bathonian to late Callovian age in Burgundy, France, to establish high-resolution magnetic correlations in a succession devoid of good stratigraphic markers and with diachronous lithofacies. Magnetic extracts reveal that the magnetic minerals carrying the characteristic remanence are mainly detrital titanomagnetites and fine-grained biogenic magnetite of probable bacterial origin. Comparison of magnetic properties with lithologic data from wireline logs indicates that large grains are predominant in marly deposits whereas fine-grained minerals are common mainly in pure limestones. We have established a polarity sequence for the core that is independent of lithology and in ludes 17 polarity zones. With the help of faunal zonation based on brachiopods and ammonites, the polarity sequence was compared with the magnetostratigraphy established previously in four other sections from the same area. The magnetostratigraphic correlation corroborates that platform flooding occurred during the early Callovian, an age in agreement with biostratigraphic interpretation constraining the age of successive onlaps. A characteristic reverse polarity interval within the ammonite Calloviense subzone is present in all the cores, confirming the utility of magnetostratigraphy for stratigraphic correlation studies throughout the Paris Basin and Burgundy.