白令海(IODP Ex. 323)深海沉积物在 MIS 8-10 期间的古地磁场变异性和修订的年代地层学

IF 2.3 3区 地球科学 Q2 OCEANOGRAPHY
Steve Lund , Makoto Okada
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引用次数: 0

摘要

本文从白令海的 IODP Ex. 323 1343、1344 和 1345 号站点提取了 MIS 8-10 年(243-375 ka)的三条古地磁时变(PSV)综合记录(方向和相对古强度)。这些记录中有 79 个倾角特征和 74 个偏角特征可以相互关联。氧同位素记录以及白令海古强度记录与氧同位素年代全球 PISO-1500 古强度记录的相关性,为我们这三个地点提供了详细的年代地层,其不确定性为±2000 年。在我们的 PSV 记录中,有两个偏移记录是可重复的,即葡萄牙孤岛偏移(286 ± 2 ka)和卡拉布里亚海脊偏移(326 ± 2 ka)。这两次偏移的方向间隔都很短(少于 500 年)。两个游程的方向都是简单的开放式循环。葡萄牙孤岛偏移具有逆时针(CC)循环,而卡拉布里亚海脊偏移具有顺时针(C)循环。在剔除所有偏移方向后,对 PSV 进行了 3 天和 9 天重叠区间的统计研究。我们发现了长期世俗变化的两个显著特点。首先,"正常 "的PSV具有连贯的长期变化性,它的几个连续的9-ky倾角或偏角平均值与总体平均值不同。这些持续的104ky变化表明了区域动力活动模式的长期记忆。这种记忆与地球磁场千年尺度的持续漂移不一致。其次,在MIS 8-10年的75%的时间间隔内,PSV的角度离散度(衡量方向变化的指标)相当低(∼15°)。但在 265-272 ka、283-295 ka 和 307-325 ka 附近的三个短时间间隔内,角度离散度增加了一倍多(∼35°)。这三个高角色散区间的开始和结束时间都很快(∼103 年)。在北大西洋,这三个高角散区间也几乎同步出现(Lund,2022 年)。这些高角散区间也是两个区域都出现偏移的区间,并且与相对较低的古强度相关。我们认为,这构成了布鲁内斯纪年全球世时变化总体模式的一个独特的双峰模式。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Paleomagnetic field variability and revised chronostratigraphy of bering sea (IODP ex. 323) deep-sea sediments during MIS 8-10

This paper develops three composite paleomagnetic secular variation (PSV) records (directions and relative paleointensity) for MIS 8–10 (243–375 ka) from IODP Ex. 323 Sites 1343, 1344, and 1345 in the Bering Sea. There are 79 inclination features and 74 declination features in each of these records that can be correlated among them. Oxygen isotope records and correlation of our Bering Sea paleointensity records to the oxygen-isotope dated global PISO-1500 paleointensity record provide a detailed chronostratigraphy for our three sites with an uncertainty of ∼±2000 years. There are two excursions recorded reproducibly in our PSV records, the Portuguese Orphan Excursion (286 ± 2 ka) and the Calabrian Ridge Excursion (326 ± 2 ka). Both of these excursions have only short intervals (less than 500 years) of excursional directions. Both excursions have simple open looping of the directions. The Portuguese Orphan excursion has counter-clockwise (CC) looping, while the Calabrian Ridge Excursion has clockwise (C) looping. Statistical study of the PSV after removal of all excursional directions has been carried in overlapping 3-ky and 9-ky intervals. We have identified two distinctive features of the long-term secular variation. First, the ‘normal’ PSV has coherent long-term variability noted by several successive 9-ky inclination or declination averages distinct from overall averages. These persistent >104 ky variations indicate long-term memory in the regional pattern of dynamo activity. Such memory is not consistent with persistent millennial-scale drift of the Earth's magnetic field. Second, PSV angular dispersion (a measure of directional variability) is quite low (∼15°) for ∼75% of the MIS 8–10 time interval. But angular dispersion more than doubles (∼35°) in three short intervals around 265–272 ka, 283–295 ka, and 307–325 ka. The onset and termination of these three high-angular-dispersion intervals occurs fast (∼103 yrs). These same three high-angular-dispersion intervals also occur almost synchronously in the North Atlantic Ocean (Lund, 2022). These high-angular-dispersion intervals are also intervals in which excursions occur in both regions and are associated with relatively low paleointensity. We think this constitutes a distinctive bimodal pattern to overall pattern to Global secular variation in the Brunhes Chron.

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来源期刊
CiteScore
4.60
自引率
4.20%
发文量
144
审稿时长
18.3 weeks
期刊介绍: Deep-Sea Research Part I: Oceanographic Research Papers is devoted to the publication of the results of original scientific research, including theoretical work of evident oceanographic applicability; and the solution of instrumental or methodological problems with evidence of successful use. The journal is distinguished by its interdisciplinary nature and its breadth, covering the geological, physical, chemical and biological aspects of the ocean and its boundaries with the sea floor and the atmosphere. In addition to regular "Research Papers" and "Instruments and Methods" papers, briefer communications may be published as "Notes". Supplemental matter, such as extensive data tables or graphs and multimedia content, may be published as electronic appendices.
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