Rock-magnetic properties confirm the eolian origin of Miocene sequences from the west of the Chinese Loess Plateau

Diagnostic rock-magnetic characteristics of Miocene sequences from the western part of the Chinese Loess Plateau are used to confirm the eolian nature of sections the origin of which has been a matter of recent dispute (Alonso-Zarza et al., 2009, 2010; Guo et al. 2010). The key magnetic properties include (i) detailed correlation of both the orbitally timed and supra-orbital variations in magnetic properties between widely separated sections, (ii) the bi-modal distribution of magnetic properties with respect to particle size, reflecting in situ neoformation alongside the deposition of detrital minerals derived from the source areas, (iii) the consistent presence, in the clay fractions, of fine ferrimagnetic grains close to the superparamagnetic/stable single domain transition, all within the size range characteristic of those formed by weathering and pedogenesis under at least partially aerobic conditions, and (iv) absence of evidence for lacustrine indicators such as bacterial magnetosome assemblages, sub-oxic diagenesis or greigite formation.