A paleomagnetic component for a proxy of water stratification and anoxia in the sedimentary archives of oceans and epicontinental seas

Abstract

This project will apply magnetic methods on key sections representative for anoxic environments in marine, hypersaline, brackish and lacustrine settings aiming to establish if there is a relationship between the presence of specific magnetic minerals and marine connectivity in general, anoxia in particular. The envisaged aim is to improve the understanding of the specific magnetic mineral's zonation as an expression of marine connectivity and productivity. The research will be focused on sedimentary successions of various ages and from various environments in which stratification and anoxia has occurred: South Atlantic anoxic pre-evaporites, form north of the Rio Grande Rise; black shales and menilites from the brackish Tethys Region - Black Sea; that will be compared with lacustrine oil shales from the Taubate basin - Brazil; sapropelic levels from in the Indian Ocean - Maldives; anoxic events levels in sediments from the Equatorial Atlantic - Demerara Rise and anoxic sediments linked with the PETM from Arctic - Svalbard islands. Those extreme conditions will be also compared with samples from other events and locations where the carbon cycle was much different from today (MMCO, MECO, EOT, OAES). We will aim to provide geochemical clarifications on the behavior of Fe3+, Fe2+ ions fixation, diagenesis and alteration in these sediments with focus on the magnetic minerals.During the project we will employ high-resolution magnetostratigraphic methods, rock-magnetism, environmental magnetism and spectroscopy (HRTEM, XANES, EDS) on continuous sedimentary successions that record anoxic episodes. The target sections have well-documented biostratigraphic, geochemical, isotopic and sedimentological information that may allow us to identify particular correlations between the anoxia (onset, progressions and shutdown) and the magnetic signatures (markers). Through this approach we aim to: 1.establish how the magnetic signature of the sediments can be linked with anoxia and can be used as marker for the rise or fall of anoxia by linking the presence of certain magnetic carriers with episodes of increase/decrease in anoxia, previously documented by biostratigraphic and geochemical studies in the same sediments;2.a better understanding how the sills, such as the Rio Grande Rise, are controlling the marine connectivity and implicitly the formation of evaporites and anoxia but also mineralization such as Manganese crusts by focusing on stratigraphic successions where changes in ocean connectivity are well documented and trying to find magnetic markers of the chemical changes induced by variations of marine connectivity;3.contribute to the understanding of the preservation/oxidation processes occurring in the anoxic sediments by performing high-resolution microscopy and spectroscopy measurements. 4.attempt to establish magnetic carriers' fingerprints for different types of anoxia. Intellectual Merit: Luigi Jovane has several years of experience working on the main cores and stratigraphic sections of the middle Eocene-Oligocene of the Neo-Tethys Realm, Indian Ocean, and Antarctica. His works represent high-impact and highly cited papers for paleomagnetism and its implications for chronostratigraphy, cyclostratigraphy and paleoclimatology for this period. Dan V. Palcu is an early career scientist with excellent background and important publications in paleomagnetism with implications in the understanding of marine connectivity and anoxia. The candidates are proposing to explore a novel approach on describing anoxia by attempting to identify zones/intervals characterized by specific magnetic carriers and correlate them with connectivity changes (and the rise/fall of anoxia).