Deep-water changes: the near-synchronous disappearance of a group of benthic foraminifera from the Late Miocene Mediterranean
Deep-water changes: the near-synchronous disappearance of a group of benthic foraminifera from the Late Miocene Mediterranean
复制标题
DOI：
10.1016/s0031-0182(99)00065-6
复制
发表时间：
1999-09-01
影响因子：
3
通讯作者：
van der Zwaan, GJ
中科院分区：
文献类型：
--
作者：
Kouwenhoven, TJ;Seidenkrantz, MS;van der Zwaan, GJ
利用意大利北部蒙特德尔赌场剖面的海底有孔虫和地球化学数据，重建了晚中新世地中海盐度危机之前的事件序列。我们评估了影响大西洋-地中海连接的海平面变化和构造事件的影响。海底有孔虫组合的变化记录了深水环境的变化，这可以用地中海盆地的逐渐隔离来解释。氧、碳稳定同位素和氧化还原敏感元素的分析结果与底栖动物区系趋势一致。在7.16 Ma，盆地隔离的第一个重要步骤是一组通常在中下坡环境中发现的深水底栖物种几乎同时消失。与此同时，稳定的同位素和氧化还原敏感元素表明底水的降温和氧合作用减弱。在6.8 Ma以后，水团分层逐渐发展，可能伴随着底层水盐度的增加，所有指标都表明。该剖面中均质沉积物和腐泥质沉积物的旋回模式与天文参数有关，并允许与地理距离相当远的地中海剖面进行详细对比。我们将底栖有孔虫动物群与沉积在相似水深(约1000m)的Metochia剖面(希腊加夫多斯)的底栖有孔虫进行了比较，发现两个地点的底栖有孔虫表明了相似的、同步的古环境发展。所有的代理都表明，晚中新世地中海盐度危机的开始可以追溯到最早的梅西期。地中海盆地向蒸发岩圈闭的发展是与400基尔偏心率相关的气候效应叠加在大西洋-地中海连接处的门户动力学之间相互作用的结果。底栖有孔虫准确地记录了地中海盆地与世隔绝的步骤。(C)1999 Elsevier Science B.V.保留所有权利。
Benthic foraminiferal and geochemical data from the Monte del Casino section in northern Italy are employed to reconstruct the sequence of events preceding the Late Miocene Mediterranean salinity crisis. We evaluate the effects of eustatic sea-level changes and tectonic events, affecting the Atlantic-Mediterranean connections. Changing benthic foraminiferal assemblages record changes in the deep-water environment, that can be explained by progressive isolation of the Mediterranean basin. The results of the analyses of stable oxygen- and carbon isotopes and redox-sensitive elements are in line with the benthic faunal trends. At 7.16 Ma, a first major step in isolation of the basin is indicated by the nearly simultaneous disappearance of a group of deeper-water benthic species usually found in middle to lower slope environments. At the same time, stable isotopes and redox-sensitive elements indicate cooling and decreasing bottom water oxygenation. After 6.8 Ma gradual development of water-mass stratification, probably accompanied by increasing bottom-water salinity, is indicated by all proxies. The cyclic pattern of homogeneous and sapropelitic sediments in the section is related to astronomical parameters, and allows a detailed correlation with Mediterranean sections at considerable geographic distances. We compared the benthic foraminiferal faunas with those from the Metochia section (Gavdos, Greece), deposited at a similar water depth (similar to 1000 m), to find that the benthic foraminifera at both sites indicate a similar, synchronous paleoenvironmental development. All proxies indicate that the onset of the Late Miocene Mediterranean salinity crisis dates back to the earliest Messinian. The development of the Mediterranean basin toward an evaporite trap is a result of interactions between a 400-kyr eccentricity related climatic effect superimposed upon gateway dynamics at the Atlantic-Mediteranean connections. Benthic foraminifera accurately record the steps in increasing isolation of the Mediterranean basin. (C) 1999 Elsevier Science B.V. All rights reserved.