The Holocene environmental changes in southern Indonesia reconstructed from highland caldera lake sediment in Bali Island
The Holocene environmental changes in southern Indonesia reconstructed from highland caldera lake sediment in Bali Island
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DOI：
10.1016/j.quaint.2015.03.020
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发表时间：
2015-07
影响因子：
2.2
通讯作者：
Y. Fukumoto;Xun Li;Y. Yasuda;M. Okamura;Kazuyoshi Yamada;K. Kashima
中科院分区：
文献类型：
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作者：
Y. Fukumoto;Xun Li;Y. Yasuda;M. Okamura;Kazuyoshi Yamada;K. Kashima
硅藻，花粉，地磁和地球化学分析进行了一个3.6米长的沉积物芯取自Buyan湖，高原火山口湖在巴厘岛中部，重建全新世气候变化赤道南印度尼西亚。岩芯代表了距今1.8万年的有机-无机湖泥沉积。以底栖硅藻化石为主要成分的不断包裹体表明沿岸的物质的悬浮和流入是主要的沉积过程。岩芯在6.5-5.0和3.6-3.1 cal ky BP两个不同的时间段内含有层状沉积物，多个代用指标记录显示，这些部分的气候普遍较干燥，特别是在3.6-3.1 cal ky BP。湖底沃茨在这些叠层时期更可能是由于增加湖泊生产力延长旱季和风混合减少条件。纹层结构由底栖硅藻和无定形有机物组成的层和仅由浮游硅藻化石组成的层组成，每一层都可能代表雨季和旱季沉积物。虽然印尼南部目前显示出明确的澳大利亚季风降雨季节性，计数层数显示出年际周期的纹层形成。长时间的旱季可能会掩盖这些时期的降雨季节性，但精确的沉积模式是难以捉摸的。未分层的部分显示均匀的沉积物混合物的底栖，浮游硅藻和更多的体积的陆源物质表明潮湿的气候和季节性类似于现在的时间。这是支持的沼泽环境花粉的更高的份额，反映了更稳定的湖泊水平的趋势。6.5 cal ky BP以来的干燥气候与全新世中期以来较强的ENSO动力学的普遍看法一致，这是由于较弱的北方夏季日照，但干燥期的零星出现意味着区域气候强迫的影响，如热带辐合带（ITCZ）的时间迁移。然而，赤道太平洋和印度洋可能发生大气候模态的时间转换。最潮湿的气候推断从3.1 cal ky BP到现在，这可能反映了南半球大气对流的重要性增加，随后在南方夏季ITCZ的位置偏南。
Diatom, pollen, geomagnetic and geochemical analyses were carried out on a 3.6 m long sediment core taken from Lake Buyan, a highland caldera lake in central Bali Island, to reconstruct the Holocene climate changes in equatorial southern Indonesia. The core represents ∼8 thousand years sedimentation of organic-diatomaceous lake mud. Constant inclusion of benthic diatom fossils as main components indicated that suspension and inflow of littoral materials were the main sedimentary process. The core contained laminated sediments in two distinct intervals at 6.5–5.0 and 3.6–3.1 cal ky BP, and multi-proxy records showed generally drier climate in these sections especially at 3.6–3.1 cal ky BP. Lake bottom waters were more reducing condition in these laminated periods probably due to increased lake productivity by prolonged dry season and wind mixing. Laminae structures were made up of a layer composed of benthic diatoms and amorphous organic materials, and a layer made by only planktonic diatom fossils, each of which may represent rainy and dry period deposits. Although southern Indonesia shows clear Australian monsoon rainfall seasonality at present, counting of layer numbers showed interannual cycles of laminae formation. Prolonged dry seasons could obscured the rainfall seasonality in these periods, but precise depositional patterns were elusive. Unlaminated sections showed homogeneous sediment mixture of benthic, planktonic diatoms and more volume of terrigenous materials indicating wetter climate and seasonality similar to the present time. This was supported by the higher share of marsh environment pollens reflecting more stable lake level trends. The dry climate from 6.5 cal ky BP was in line with the general perception of stronger ENSO dynamics from the mid Holocene due to weaker than before boreal summer insolation, but the sporadic appearances of dry periods imply the influence of regional climate forcings such as temporal migrations of inter tropical convergence zone (ITCZ). It was, however, possible that temporal shifts of large climate mode occurred in equatorial Pacific and Indian Oceans. Wettest climate was inferred from 3.1 cal ky BP to the present and this might reflect increased importance of Austral hemisphere atmospheric convection and subsequent southerly position of ITCZ in Austral summer time.