Rock magnetic properties and relative paleointensity stack for the last 300 ka based on a stratigraphic network from the subtropical and subantarctic South Atlantic

Abstract: We present a detailed study of natural remanence and rock magnetic properties of eight sediment cores from a South–North profile across the subtropical front (STF) in the South Atlantic, which previously have been combined into a stratigraphic network. Based on these measurements, we construct a first relative paleointensity (RPI) stack for the central South-Atlantic (SAS-300) covering the last 300 ka. The degree of down-core homogeneity of magnetic mineral concentration as well as magnetic mineral content and grain sizes vary between all cores and are quantified by high-resolution rock magnetic measurements. In the cores north of and close to the STF, the magnetic remanence is mainly carried by magnetite. The cores in the south also contain a high coercive mineral fraction. Based on a linear model of the sediment matrix, we propose to apply principal component analysis (PCA) of natural remanent magnetization (NRM), anhysteretic, and isothermal remanent magnetization (ARM and IRM) to determine a homogeneity interval, where remanences are only affected by a single environmental signal. This reduces lithologic and climatic influence upon the relative paleointensity record. For our data set PCA indicates that all remanences in the 30 mT to 80 mT demagnetization interval are dominated by a single environmental influence. Single core RPI estimates are then obtained by normalizing the NRM fraction in this homogeneity interval with respect to either IRM, ARM in the same interval, or by κ. By direct averaging, we obtain the stack SAS-300, which is compared to other paleointensity series such as Sint-800, or the RPI records from ODP Sites 1089 (Subantarctic South Atlantic) and 983 (Gardar Drift). The detailed documentation of environmental influences combined with the presentation of seven different recordings of the same geomagnetic signal allows to connect southern and northern hemisphere RPI data, also with respect to possible common environmental distortions. [Copyright &y& Elsevier]