Development of Cenozoic deep-sea benthic foraminiferal faunas in Antarctic waters
Development of Cenozoic deep-sea benthic foraminiferal faunas in Antarctic waters
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南极海域新生代深海底栖有孔虫动物群的发育
DOI：
10.1144/gsl.sp.1989.047.01.21
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发表时间：
1989
期刊：
影响因子：
--
通讯作者：
Ellen Thomas
中科院分区：
文献类型：
--
作者：
Ellen Thomas
南极洲Maud Rise大洋钻探计划689号（现今水深2080 m）和690号（现今水深2914 m）站位的上深海至下半深海底栖有孔虫记录了新生代期间南半球高纬度深水特征的变化。底栖有孔虫动物群显示只有轻微的差异，由于不同地点之间的水深的差异，和动物群组成的变化是同时代的。这些变化分别发生在古新世早/晚界线（± 61.6Ma）、古新世晚期（± 57.5Ma）、早始新世中期（± 55.0Ma）、中始新世中期（± 46.0Ma）、渐新世早期（± 36.5Ma）和中新世早期（± 14.5Ma）。古新世末的动物群变化是最重要的，也是世界公认的。在莫德高地，生物多样性下降了50%，许多常见物种在不到20000年的时间里灭绝。在始新世早期，多样性再次增加，并达到相同的价值观，在古新世的始新世中期。在始新世中期，多样性开始下降，并持续下降，直到中新世中期。中中新世开始至今，除晚中新世（±8.5- 7.5Ma）和第四纪部分地层外，生物硅质软泥堆积，钙质底栖有孔虫普遍缺失。海底有孔虫动物群组成在很大深度范围内（深海上部-深海下部）的变化可能表明海洋深层沃茨形成过程中的重大变化时期。最早的始新世动物群，生活在古新世末期的大灭绝之后，其特点是多样性低，小物种相对丰度高，可能向下迁移到深水沃茨。这些动物群，以及在较小程度上，那些在早中始新世，其特点是较高的相对丰度的双头和三系列的物种。相比之下，较老和较年轻的动物群有较高的相对丰度的螺旋物种。这表明，从古新世晚期到中始新世早期，莫德海隆底部沃茨的溶解氧含量很低，古新世末期底栖有孔虫的大灭绝可能是由于深层沃茨变暖导致溶解氧含量减少。变暖可能是由于板块构造活动导致的深层沃茨来源的变化。从始新世中期到中新世，物种多样性的总体下降可能反映了深层沃茨的持续冷却。因此，底栖有孔虫动物群表明，高纬度深海沃茨的新生代变化并不是从白垩纪环流逐渐发展到今天的深水形成模式：底栖动物群的变化是以不连续的步骤发生的。底栖动物的组成表明，深水最有可能在高纬度地区形成的马斯特里赫特-古新世早期，并从始新世中期到最近，在低纬度地区（温暖，咸的深水）在最新的古新世和始新世早期的深水形成的插曲。
Abstract Upper abyssal to lower bathyal benthic foraminifera from Ocean Drilling Program Sites 689 (present water depth 2080 m) and 690 (present water depth 2914m) on Maud Rise (Antarctica) recorded changes in deep-water characteristics at high southern latitudes during the Cenozoic. The benthic foraminiferal faunas show only minor differences as a result of the difference in water depths between the sites, and changes in faunal composition were coeval. These changes occurred at the early/late Paleocene boundary (±61.6 Ma), in the latest Paleocene (±57.5 Ma), in the middle early Eocene (±55.0 Ma), in the middle middle Eocene (±46.0 Ma), in the earliest Oligocene (±36.5 Ma) and in the early middle Miocene (±14.5 Ma). The faunal change at the end of the Paleocene was the most important and has been recognized world-wide. On Maud Rise, the diversity decreased by 50% and many common species became extinct over a period of less than 20 000 years. Diversity increased again during the early Eocene, and reached the same values as in the Paleocene by the middle Eocene. In the middle Eocene the diversity started to decrease, and continued to decrease until the middle Miocene. From the beginning of the middle Miocene until today biosiliceous oozes accumulated and calcareous benthic foraminifera were generally absent, with the exception of part of the late Miocene (±8.5–7.5 Ma) and the Quaternary. Changes in composition of the benthic foraminiferal faunas over a wide depth range (upper abyssal-lower bathyal) probably indicate periods of major changes in the formational processes of the deep waters in the oceans. The earliest Eocene faunas, living just after the major extinction at the end of the Paleocene, are characterized by low diversity and high relative abundance of small species that probably migrated downslope into the deep waters. These faunas, and to a lesser degree those in the early middle Eocene, are characterized by high relative abundance of biserial and triserial species. In contrast, older and younger faunas have high relative abundances of spiral species. This suggests that bottom waters on Maud Rise were poor in dissolved oxygen in the latest Paleocene through early middle Eocene, and that the major extinction of benthic foraminifera at the end of the Paleocene might have resulted from a decrease in availability of dissolved oxygen as a result of warming of the deep waters. Warming might have been caused by a change in sources of deep waters, possibly as a result of plate-tectonic activity. The overall decrease in diversity from middle Eocene through Miocene probably reflects continual cooling of the deep waters. Benthic foraminiferal faunas thus indicate that Cenozoic changes in the deep oceanic waters at high latitudes did not consist of gradual progression from Cretaceous circulation to the present-day patterns of formation of deep water: the benthic faunal changes occurred in discrete steps. Benthic faunal composition indicates that deep water most probably formed at high latitudes during the Maastrichtian—early Paleocene, and from the middle Eocene to Recent, with episodes of deep water formation at low latitudes (warm, salty deep water) during the latest Paleocene and early Eocene.