Sedimentation processes and new age constraints on rifting stages in Lake Baikal: results of deep-water drilling
Sedimentation processes and new age constraints on rifting stages in Lake Baikal: results of deep-water drilling
复制标题
贝加尔湖裂谷阶段的沉积过程和新时代限制：深水钻探结果
DOI：
10.1007/s005310000090
复制
发表时间：
2000
影响因子：
2.3
通讯作者：
A. Gvozdkov
中科院分区：
文献类型：
--
作者：
M. Kuzmin;E. Karabanov;A. Prokopenko;V. Gelety;V. Antipin;Douglas F. Williams;A. Gvozdkov
在本文中，我们首次尝试将BDP-93、BDP-96和BDP-97钻孔的岩性、成分和年龄测定的直接结果与这些剖面钻探区域的地质和地震数据相结合。BDP钻孔所代表的沉积环境明显不同，具有独特的岩性特征。深钻的结果提供了测试贝加尔湖裂谷动力学地质重建中使用的许多年龄模型的基本手段。在院士岭的BDP-96钻孔中，既没有发现从地震数据解释的全盆地不整合，也没有发现在地震地层复合体边界处从浅水相到深水相的解释变化。此外，岩性不支持拟议的重建强烈的湖平面波动和海侵在上新世在院士岭。院士岭深水半远洋沉积作用持续存在5 Ma。在地震剖面上，将新贝加尔亚期强烈裂谷阶段的开始和沉积过程中的相关剧烈变化解释为全盆地不整合面B10。不同的年龄估计，这个边界范围从上新世晚期（3.5马）上新世更新世的边界。如BDP-96钻孔所示，B10与从淤泥质软泥到致密粉质粘土的岩性变化有关，而不是与侵蚀接触有关。在BDP-96中，该界线的新年龄约为2.5Ma。这一新的年龄限制表明，北方贝加尔湖上部沉积地层（厚1.5-1.7 km）形成于过去2.5 Ma，平均沉积速率为60-70 cm/ka。Buguldeika的BDP-93钻孔表明，滨海山脉的隆起发生在1.07-1.31 Ma之前，这一日期超过了以前地质模型的年龄。
With this paper we present a first attempt to combine the direct results on lithology, composition and age dating in the boreholes BDP-93, BDP-96 and BDP-97 with geological and seismic data from the areas where those sections were drilled. The sedimentary environments represented by the BDP boreholes are markedly different and possess characteristic lithological features. The results of the deep drilling provide the essential means for testing numerous age models used in geological reconstructions of the Lake Baikal rifting dynamics. Neither the basin-wide unconformity interpreted from seismic data, nor the interpreted change from shallow-water to deep-water facies at the boundary of the seismic stratigraphic complexes were found in the BDP-96 boreholes on Academician Ridge. Also, lithology does not support the proposed reconstructions of intense lake level fluctuations and transgressions during the Pliocene at Academician Ridge. The continuous deep-water hemipelagic sedimentation at Academician Ridge has existed for the past 5 Ma. The beginning of an intense rifting phase of the Neobaikalian sub-stage and related drastic changes in sedimentation processes were interpreted on seismic sections as the basin-wide unconformity B10. Different age estimates for this boundary ranged from Late Pliocene (3.5 Ma) to Plio-Pleistocene boundary. As shown by BDP-96 borehole, B10 is associated with a lithological change from diatomaceous ooze to dense silty clay and not with an erosional contact. The new age for this boundary in BDP-96 is approximately 2.5 Ma. This new age constraint suggests that the upper sedimentary strata of Northern Baikal (1.5–1.7 km thick) have formed during the past 2.5 Ma with average sedimentation rates of 60–70 cm/ka. The BDP-93 boreholes at Buguldeika suggest that uplift in Primorsky Range took place prior to 1.07–1.31 Ma, a date which exceeds the age of previous geological models.