The Magnetostratigraphy Susceptibility for Lowermost Lower Devonian to Uppermost Middle Devonian Marine Rocks: Eastern Anti Atlas, Morocco Ahmed El Hassani Resident Member, Hassan II Academy of Sciences and Technology, Morocco Brooks B. Ellwood Department of Geology and Geophysics, Louisiana State University, Baton Rouge, Louisiana 70803, USA ABSTRACT Magnetic susceptibility (MS) data from marine rocks are being used for global correlation, because these data are a proxy for time synchronous variations in global erosion cycles, driven by eustacy and climate change. The MS reflects the detrital flux into the marine environment resulting from these erosional pulses. We present here the MS signature from three stratigraphic intervals that are biostratigraphically well studied, from the lowermost Lower Devonian (Lochkovian Stage) through the uppermost Middle Devonian through most of the Givetian Stage, a data base including ~3,300 samples, and ~30 million years of the Devonian. Fluctuating detrital input, due to eustatic-based erosion, is associated with the bioevents observed in our data sets. These bioevents include the well-known Chotec and Kačák Intervals at the Emsian/Eifelian and Eifelian/Givetian boundaries, respectively, as well as the two "Terebratula" pumilio events in the Upper Givetian. All these bioevents are associated with pronounced sea-level high stands. In the Lower Emsian there are two anomalous, large-amplitude transgression-regression (T/R) cycles that demonstrate significant changes in detrital content into the marine system. We see two possible explanations for these pulses. One, these pulses result from either major plate boundary changes and large-scale eustatic fluctuations due to the collision of Laurentia with elements of Gondwana at that time, or two, are due to the development of complex plant structures and root systems as plants covered continents for the first time, resulting in enhanced chemical weathering producing anomalous detrital sediment pulses into the marine environment that ended with soil stabilization at the end of the Lower Emsian. RESUME Les données de la susceptibilité magnétique (MS) à partir de roches marines sont actuellement utilisées pour établir des corrélations globales, parce que ces données sont dues à des variations temporelles synchrones de l'érosion à l’échelle mondiale, à cause de l'eustatisme et des changements climatiques. MS reflète le flux détritique dans le milieu marin résultant de ces impulsions d'érosion. Nous présentons ici l’empreinte MS à partir de trois intervalles stratigraphiques qui sont biostratigraphiquement bien étudiés, et couvrant l’espace entre la partie basale du Dévonien inférieur (étage Lochkovien) et le Dévonien terminal, incluant la plupart de 1