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

Lund 9526940本提案要求资金，以便从最近在北大西洋西部(北纬35°，西经72°)的深海沉积物布莱克/巴哈马外脊发现的一组28个活塞芯(平均长度为20米)中恢复氧同位素第5和第6阶段的重复、详细的PSV、漂移和古强度记录。所有取芯沉积物的年龄均小于20万年(18 O阶段6)，沉积速率至少为10 cm/Kyr；大多数在更新世的沉积速率大于20 cm/Kyr。以前对布莱克/巴哈马外脊沉积物的古地磁和沉积物磁学研究表明，这些岩心记录了古磁场长期变化(PSV)，不同岩心的PSV记录可以很容易地在它们之间进行对比。这项先前工作最重要的方面之一是首次完整地记录了拉尚之旅(42ka)。这种漂移记录独特的矢量和古强度模式及其与莫诺湖漂移(28ka)的自相似性表明，它们是由相同类型的核心发电机过程形成的。来自我们三个新岩心的初步古地磁数据清楚地表明，这些记录还包含另外两个漂移：首次从布莱克/巴哈马外脊(Smith and Foster，1969)沉积岩芯定义的布莱克事件(Blake Event)(约125ka)，以及Biwa I？远足(约170ka)。初步的古地磁数据表明，布莱克漂移在氧同位素阶段5的最早时段内看起来像是一个真正的反极性区间。另一方面，碧瓦I漂移看起来更像莫诺湖和拉尚漂移。这项拟议的研究将为建立PSV和远足之间关系的新模型提供关键的新信息，并将在古磁学界产生广泛影响。

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.