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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Biological control of paleomagnetic remanence acquisition in carbonate framework rocks of the Tahiti coral reef
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Biological control of paleomagnetic remanence acquisition in carbonate framework rocks of the Tahiti coral reef

机译：塔希提岛珊瑚礁碳酸盐骨架岩石中古磁性残留物的生物控制

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摘要

Integrated Ocean Drilling Program (IODP) Expedition #310 recovered 632meters of Post Last-Glacial-Max (Post-LGM) and late Pleistocene coral reef framework rocks (37 holes at 22 sites) from the current fore-reef slopes surrounding the island of Tahiti. The cores were collected primarily to constrain the timing and amplitude of rising sea levels associated with the end of the last global glaciation (10-18,000 YBP), to identify the climatic and environmental changes during that period, and to evaluate the reef response to those combined changes. The cores, which were collected in three regions (Faaa, Tiarei, and Maraa), are remarkable in that more than 60% of the total core volume is associated with microbialites rather than macroscopic coral or coralline algae assemblages. We present here paleomagnetic data from 316 oriented paleomagnetic samples collected from the Post-LGM framework rocks of the Maraa region (12 holes at 6 sites). 96% of our samples were recovered from microbialites that have filled the primary cavities of the coral/coralgal framework. All samples appear to accurately record geomagnetic field variability at Tahiti (average inclination=-30.6°, alpha_(95)~2.9°, site axial dipole inclination=-32.6°) and yet the samples are composed of ~99% precipitated calcium carbonate. Our rock magnetic data indicate that the NRM resides almost entirely in detrital titanomagnetite grains derived from the Tahiti volcanic edifice. We present magnetic and microscopic evidence that the natural remanent magnetization in the carbonate rocks was locked in through mediation of organic biofilms (mostly bacterial) that held the grains in place until they were trapped by carbonate precipitation.
机译：综合大洋钻探计划（IODP）第310号远征队从塔希提岛周围目前的前礁斜坡上回收了632米的上冰川后（LGM）和更新世晚期的珊瑚礁构架岩石（22个位置的37个孔） 。收集岩心主要是为了限制与上一次全球冰川期结束（10-18,000 YBP）相关的海平面上升的时间和幅度，以识别该时期的气候和环境变化，并评估珊瑚礁对那些变化的反应。综合变化。在三个地区（Faaa，Tiarei和Maraa）收集的岩心很显着，因为超过60％的岩心总体积与微辉石而不是宏观的珊瑚或珊瑚藻类组合有关。我们在这里展示了从Maraa地区（6个位置的12个孔）的LGM后骨架岩石中收集的316个定向古磁样本的古磁数据。我们的样本中有96％是从填满珊瑚/珊瑚骨架主要腔的微辉石中回收的。所有样品似乎都能准确记录大溪地的地磁场变化（平均倾角= -30.6°，α_（95）〜2.9°，局部轴向偶极倾角= -32.6°），但样品由约99％的沉淀碳酸钙组成。我们的岩石磁数据表明，NRM几乎完全存在于来自大溪地火山大厦的碎屑钛磁铁矿晶粒中。我们提供的磁性和微观证据表明，碳酸盐岩石中的自然剩余磁化强度通过有机生物膜（主要是细菌）的介导作用而被锁定，该生物生物膜将谷物保持在原位，直到被碳酸盐沉淀捕获为止。

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