∼4 Ma coarsening of sediments from Baikal, Chinese Loess Plateau and South China Sea and implications for the onset of NH glaciation
∼4 Ma coarsening of sediments from Baikal, Chinese Loess Plateau and South China Sea and implications for the onset of NH glaciation
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DOI：
10.1016/j.palaeo.2010.09.025
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发表时间：
2010-12-15
影响因子：
3
通讯作者：
Ma, Xiaolin
中科院分区：
文献类型：
--
作者：
Jiang, Hanchao;Mao, Xue;Ma, Xiaolin
沿着青藏高原东北缘发生了强烈的构造运动。在同一时期，全球气候从稳定时期转变为频繁和突变时期，这使得河流和冰川系统无法建立平衡状态。因此，很难将东亚3-4 Ma粗粒沉积物堆积直接归因于气候变化或构造活动。本研究将黄土高原晚新生代多代用指标记录与南海低纬粒度、海平面和底栖三角洲O-18记录以及贝加尔湖高纬粒度记录进行了比较。所有记录都表明，自近似4 Ma以来，该地区经历了稳定而持续的冷却，这与世界其他地区的冷却记录有很好的相关性。这与4.8 ~ 4.0 Ma期间中美洲航道（CAS）关闭引发大西洋纬向翻转环流加强导致北方半球（NH）变暖和南半球（SH）变冷的模拟结果在时间上相吻合。南半球的冷却将导致南极冰盖的显著发展，大约在4 Ma左右，将热带辐合带（ITCZ）推向北方。这与北半球变暖相叠加，给北半球中纬度地区带来了更多降水，导致4.2 Ma以来CLP西部四口子剖面粗颗粒沉积物增加。值得注意的是，在3.0-2.1 Ma期间，在寺口子断面没有粗颗粒沉积，而寺口子粒度记录反映的粗颗粒峰值自2.1 Ma以来逐渐减少，这可能是由于NH冰体积逐步增加，将ITCZ向南推。另一方面，南极冰盖的发展将导致全球变冷和物理风化的增强，引发沉积速率的增加以及从贝加尔湖到CLP到SCS的粒度的增加。因此，CAS在4.8- 4.0Ma期间的关闭及其对海洋热输送的影响可能是4 Ma以来全球变冷的主要强迫因子。4-3 Ma的持续稳定冷却可能对2.75Ma前北半球冰盖的形成有重要贡献。(C)2010 Elsevier B. V.保留所有权利。
Intense tectonic movement occurred along the northeastern margin of the Tibetan Plateau 3-4 Ma. During the same time period, global climate changed from a period of stability to a period of frequent and abrupt changes, which prevented fluvial and glacial systems from establishing a state of equilibrium. Thus, it is difficult to directly attribute the 3-4 Ma coarse-grained sediment accumulation in East Asia to climate change or tectonic activity. This study compares Late Cenozoic multi-proxy records from the Chinese Loess Plateau (CLP) to the low-latitude grain size, sea level and benthic delta O-18 records from the South China Sea (SCS) and the high latitude grain-size record from Lake Baikal. All records suggest a steady and persistent cooling since similar to 4 Ma, which correlates well with those cooling records from other regions around the world. This coincided in timing with the modeling results that the closure of the Central American Seaway (CAS) initiated strengthening of Atlantic meridional overturning circulation between 4.8 and 4.0 Ma which led to both warming of the Northern Hemisphere (NH) and cooling of the Southern Hemisphere (SH). Cooling of the SH would induce a marked development of the Antarctic ice sheets at similar to 4 Ma, pushing the Intertropical Convergence Zone (ITCZ) northward. This was superimposed on warming of the NH and brought more precipitation to the middle latitudes of the NH, resulting in increases in coarse-grained sediments in the Sikouzi section from the western CLP since 4.2 Ma. Notably, the absence of coarse-grained sedimentation in the Sikouzi section during 3.0-2.1 Ma and the gradual decrease in coarse-grained peaks since 2.1 Ma reflected by the Sikouzi grain-size record probably resulted from stepwise increase in the NH ice volume pushing the ITCZ southward. On the other hand, development of the Antarctic ice sheets would induce global cooling and enhancement of physical weathering, initiating increases in sedimentation rates as well as increases in grain size from Lake Baikal to the CLP to the SCS. Therefore the closure of the CAS during 4.8-4.0 Ma and its influence on ocean heat transport was possibly the major forcing factor for global cooling since 4 Ma. A persistent and steady cooling during 4-3 Ma probably made a significant contribution to the establishment of the NH ice sheets at 2.75 Ma ago. (C) 2010 Elsevier B.V. All rights reserved.