Inconsistent palaeomagnetic recording of the Blake event in Chinese loess related to sedimentary environment

Three loess sequences located east of the Liupan mountain region, China, were studied to obtain records of the Blake polarity event. Palaeomagnetic records from the appropriate stratigraphic interval of these three sequences, however, record the Blake event poorly in one case and not at all in the other two cases. It is important to understand why these loess sequences miss the Blake event, whereas others record it quite well. We conclude that regional variations in the sedimentary environment over the Chinese loess plateau are responsible for the inconsistent recording of the Blake event. The palaeomagnetic records suggest a threefold subdivision of the Chinese loess plateau into (1) the central and southern portions of the part of the plateau that lies east of the Liupan Mountains, where the primary record of the Blake event has been severely smoothed or wiped out by pedogenic processes during palaeosol (S1) formation; (2) the northern margin of the loess plateau to the east of the Liupan Mountains, where frequent, severe dust storms have resulted in discontinuous records with a high probability of missing the Blake event; and (3) the region west of the Liupan Mountains, where loess sequences are deposited rapidly and nearly continuously with only minor pedogenesis, and are thus capable of recording short events like the Blake.