The Potential of Marine Ferromanganese Nodules From Eastern Pacific as Recorders of Earth's Magnetic Field Changes During the Past 4.7 Myr: A Geochronological Study by Magnetic Scanning and Authigenic 10Be/9Be Dating
Abstrakt
The Clarion and Clipperton Fracture Zones in the Eastern Pacific are well known as a manganese nodule belt, which developed since the late Oligocene. The slow growth rate of these marine ferromanganese nodules implies that they have potentially recorded long-term environmental changes.
To produce environmental records from these nodules, their chronology needs to be established first. In order to achieve this objective, many dating methods have been applied; however, due to relatively low-resolution temporal constraint, high-resolution environmental signals recorded in marine ferromanganese nodules have not been well documented yet.
In this paper, we present a geochronological study based jointly on magnetic scanning and analyses of the authigenic beryllium isotopes (authigenic (10)Be/(9)Be) and the cobalt (Co) flux of a marine ferromanganese nodule. Results lead to the following observations: (1) The growth of the studied nodule resulted from a combination of hydrogenetic and diagenetic processes, and (2) a total of 24 magnetozones is recognized for the studied nodule.
Correlation to the geomagnetic polarity timescale suggests that chrons from C3n.2r to C1n were recorded in the nodule, implying that the growth of this nodule initiated ~4.70 Ma, which agrees well with the authigenic (10)Be/(9)Be and Co chronometers. Furthermore, a consistent pattern of broad paleomagnetic field variations was observed between the nodule's magnetic signal and the ocean-floor magnetic fields of the South Atlantic, confirming the validity of our growth model.
Overall, our study highlights the potential of marine ferromanganese nodules from the Eastern Pacific as recorders of changes in Earth's magnetic field.