A Paleomagnetic Study of the Blake Event in Chinese Loess-Paleosol Sequences

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9903074 Van der VooThe Blake Event is a short-duration reversed interval in the Brunhes Chron. It is thought to have occurred about 125,000 years B.P, although its age is poorly constrained. It possibly included multiple reversals (up to three reversed intervals have been reported). The PI intends to obtain up to seven parallel records from Chinese loesses and paleosols near Lanzhou, where the Blake Event has previously been observed in a few places. The goals are (1) to constrain the beginning and end dates of the Event, (2) to verify whether the Event consists of multiple reversals or not, and (3) to determine whether some of the loess-paleosol sequences acquired their remanent magnetizations with a significant delay. This delay time, in turn, is critical to correct inferred ages for older reversal boundaries in the loess, such as the Matuyama-Brunhes boundary. A mismatch exists in the literature between the paleoclimatic stage in which this reversal is recorded in the Chinese loess (a cold interval) and that recorded in deep-marine sequences (a warm interval). Once delay times (if any) have been quantified, the PI will attempt to correlate these factors with environmental parameters, such as precipitation, sedimentation rates, or degree of pedogenesis, as revealed through rock magnetic studies of the magnetic minerals. This correlation is important to assess the use of magnetic parameters as paleoclimatic proxies, particularly for the evolution of Asian and Indian monsoonal patterns.