Showing papers by "Augusto Mangini published in 1989"
TL;DR: In this paper, high-resolution 10Be dating was applied to 16 manganese nodules and crusts from different localities in the world oceans to determine time markers at about 3 Ma, 6.5 Ma, and 14 Ma.
Abstract: Time markers at about 3 Ma., 6.5 Ma., and 14 Ma. are common to 16 manganese nodules and crusts from different localities in the world oceans. These time markers correspond to variations in the growth rates, in the inner structure, and in the chemistry of the samples. The observed time markers could be related to (1) changes of the bottom water velocity and (2) variations in the manganese and iron contents in the deep ocean. The time markers were determined by high-resolution 10Be dating, applying the accelerator mass spectrometry facility at the Eidgenossische Technische Hochschule Zurich.
42 citations
TL;DR: In this paper, the Kane gap was investigated and the structure of the nodule was compared with the stratigraphy of the related sediments, and the following conclusions were drawn concerning the sedimentation processes during the last 4 to 6×106 years: the growth of the nuggets started about 4 to 4.5 Ma before present during or near to the end of a period of erosion on a fossil-free, probably Miocene sediment.
Abstract: Manganese nodules from the Kane Gap (a deep sea channel connecting the Sierra Leone and Gambia Basins off West Africa) were investigated chemically and dated by10Be along cross-sections. Comparing the nodule structure with the stratigraphy of the related sediments, the following conclusions are drawn concerning the sedimentation processes during the last 4 to 6×106 years: The growth of the nodules started about 4 to 4.5 Ma before present during or near to the end of a period of erosion on a fossil-free, probably Miocene sediment. During the first phase of only a few hundred thousandyears, the nodules grew very quickly (7 to >18 mm/Ma). Fe-rich hydrogenetic material formed the internal sections of the nodules during this time. Slowing down of the bottom currents, resulting in deposition of thin sediment covers for short intervals, caused the character of the nodules to change to a more diagenetic composition. The growth rates were reduced to about 1 to 2 mm/Ma. The time of slowing is roughly 3 to 4 Ma BP.
6 citations