Early Paleogene variations in the calcite compensation depth: new constraints using old borehole sediments from across Ninetyeast Ridge, central Indian Ocean
Early Paleogene variations in the calcite compensation depth: new constraints using old borehole sediments from across Ninetyeast Ridge, central Indian Ocean
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DOI：
10.5194/cp-11-473-2015
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发表时间：
2015-03
影响因子：
4.3
通讯作者：
B. S. Slotnick;V. Lauretano;J. Backman;G. Dickens;A. Sluijs;L. Lourens
中科院分区：
文献类型：
--
作者：
B. S. Slotnick;V. Lauretano;J. Backman;G. Dickens;A. Sluijs;L. Lourens
抽象。全球碳循环的重大变化发生在62 Ma至48 Ma之间，这些变化很可能与海洋-大气系统总碳储量的变化有关。根据碳循环理论，海洋碳质量的变化应反映在同期全球海洋碳酸盐在海底的积累，从而反映在方解石补偿深度（CCD）的深度。为了更好地限制这些变化的原因和幅度，该社区需要从广泛分离的深海沉积物部分，特别是包括印度洋的早第三纪碳同位素和碳酸盐积累记录。这一时间间隔的几个CCD重建已经产生了使用科学钻探网站在大西洋和太平洋，但是，相应的信息，从印度洋一直非常有限。为了评估CCD的深度和印度洋古近纪层序重新科学钻探的潜力，我们研究了横跨Ninetyeast Ridge的三个地点的古新世晚期-始新世早期沉积物的岩性、超微化石、碳同位素和碳酸盐含量记录：深海钻探项目（DSDP）站点213（深，东），214（浅，中央）和215（深，西）。扰动的、不连续的沉积物剖面并不理想，因为它们是使用旋转取心方法在单孔中采集的，但仍然是印度洋中部最好的古近纪沉积物。213和215站点的δ 13 C记录与大西洋和太平洋几个地点的记录相似，包括215站点古新世碳同位素最大值（皮姆）期间δ 13 C的显著高值，以及213和215站点始新世早期气候最佳值（EECO）期间δ 13 C的显著低值。古新世-始新世热极大期（PETM）和K/X事件在213号站点发现，但在215号站点没有发现，可能是因为取芯间隙。213号和215号站点的碳酸盐含量下降到
Abstract. Major variations in global carbon cycling occurred between 62 and 48 Ma, and these very likely related to changes in the total carbon inventory of the ocean-atmosphere system. Based on carbon cycle theory, variations in the mass of the ocean carbon should be reflected in contemporaneous global ocean carbonate accumulation on the seafloor and, thereby, the depth of the calcite compensation depth (CCD). To better constrain the cause and magnitude of these changes, the community needs early Paleogene carbon isotope and carbonate accumulation records from widely separated deep-sea sediment sections, especially including the Indian Ocean. Several CCD reconstructions for this time interval have been generated using scientific drill sites in the Atlantic and Pacific oceans; however, corresponding information from the Indian Ocean has been extremely limited. To assess the depth of the CCD and the potential for renewed scientific drilling of Paleogene sequences in the Indian Ocean, we examine lithologic, nannofossil, carbon isotope, and carbonate content records for late Paleocene – early Eocene sediments recovered at three sites spanning Ninetyeast Ridge: Deep Sea Drilling Project (DSDP) Sites 213 (deep, east), 214 (shallow, central), and 215 (deep, west). The disturbed, discontinuous sediment sections are not ideal, because they were recovered in single holes using rotary coring methods, but remain the best Paleogene sediments available from the central Indian Ocean. The δ13C records at Sites 213 and 215 are similar to those generated at several locations in the Atlantic and Pacific, including the prominent high in δ13C across the Paleocene carbon isotope maximum (PCIM) at Site 215, and the prominent low in δ13C across the early Eocene Climatic Optimum (EECO) at both Site 213 and Site 215. The Paleocene-Eocene thermal maximum (PETM) and the K/X event are found at Site 213 but not at Site 215, presumably because of coring gaps. Carbonate content at both Sites 213 and 215 drops to