Magnetostratigraphy of an early-middle Miocene loess-soil sequence in the western Loess Plateau of China

Stratigraphy and magnetic susceptibility of the Quaternary eolian deposits at different sites in China can be closely correlated, confirming their spatial coherence and temporal continuity. The extent to which these conclusions are true for the Miocene loess-soil sequences remains to be addressed. Here, a 231.9-m eolian section, QA-III, is geomagnetically dated, yielding an age span of 21.4 -11.4 Ma, with the portion older than 19.6 Ma being partially water-reworked. The magnetozones, litholigic structure and magnetic susceptibility of the sequence are highly correlative with the QA-I and QA-II sections, 30 km west of QA-III. These sequences demonstrate that the Miocene loess deposits are also spatially correlative in stratigraphy, present a near-continuous sequence of paleoenvironment changes, and that magnetic susceptibility is a useful tool for stratigraphic correlation. The basal age of QA-III confirms again the onset of Asian inland deserts and monsoon-dominate climates by the early Miocene.