Paleomagnetic Field Variability 100-200,000 YBP: A Test of the Relationship Between Excursions and Secular Variation

点击翻译按钮获取中文摘要

Lund 9526940 This proposal requests funds to recover replicate, detailed PSV, excursion, and paleointensity records within oxygen isotope stages 5 and 6 from a group of 28 piston cores (20 m average length) that has recently been recovered from the Blake/Bahama Outer Ridge, a deep-sea sediment drift deposit in the Western North Atlantic Ocean (35o N, 72o W). All of the cored sediments are less than 200,000 years old ( 18 O Stage 6) and have sedimentation rates of at least 10 cm/kyr; most have rates greater than 20 cm/kyr during the Pleistocene. The PIs previous paleomagnetic and sediment magnetic studies of sediments from the Blake/Bahama Outer Ridge clearly show that paleomagnetic field secular variation (PSV) is recorded in these cores, and that the PSV records from the different cores can be easily correlated among them. One of the most significant aspects of this previous work is the first complete record of the Laschamp excursion (42 ka). The distinctive vector and paleointensity pattern of this excursion record and its self-similarity to the Mono Lake excursion (28ka) argue that they were formed by the same style of core dynamo process. Preliminary paleomagnetic data from three of our new cores clearly indicate that these records also contain two more excursions: 'Blake event' (ca. 125 ka), first defined from sediment cores of the Blake/Bahama Outer Ridge (Smith and Foster, 1969), and the Biwa I? excursion (ca. 170 ka). Preliminary paleomagnetic data indicate that the Blake excursion looks like a true reversed polarity interval within the earliest interval of oxygen isotope stage 5. On the other hand, the Biwa I excursion looks much more like the Mono Lake and Laschamp excursions. The proposed research will provide critical new information for developing a new model of the relationship between PSV and excursions and will have a broad impact in the paleo-magnetics community.