New seismic stratigraphy and Late Tertiary history of the North Tanganyika Basin, East African Rift system, deduced from multichannel and high-resolution reflection seismic data and piston core evidence
New seismic stratigraphy and Late Tertiary history of the North Tanganyika Basin, East African Rift system, deduced from multichannel and high-resolution reflection seismic data and piston core evidence
复制标题
DOI：
10.1111/j.1365-2117.1996.tb00112.x
复制
发表时间：
1996-03-01
期刊：
影响因子：
3.2
通讯作者：
Klerkx, J
中科院分区：
文献类型：
--
作者：
Lezzar, KE;Tiercelin, JJ;Klerkx, J
本文介绍了在东非裂谷系坦噶尼喀湖北方进行高分辨率（火花）反射地震勘探的初步结果。我们结合这些结果与早期的多道反射地震和5-kHz回声测深调查的数据。三种互补的地震调查方法的结合使我们能够提出一个新的方案，晚中新世到最近的沉积演化的北坦噶尼喀盆地。地震层序和区域构造信息使我们能够推断每个地层层序末端的古地形。盆地历史包括六个阶段，解释为区域构造和/或气候变化的响应。利用反射地震-放射性碳方法（RSRM），估算出各相（层序界面以上）的起始年龄分别为：约7.4Ma，约1.1Ma，约393-363 ka，约295-262 ka，约193-169 ka，约40-35 ka。在过去五个阶段中，低于现今湖平面的相应低位湖高程估计分别为：类似于650-700 m、类似于350 m、类似于350 m、类似于250 m和类似于160 m。最后一个阶段从近似40-35 ka直到现在，可以细分为三个亚阶段，由两个低水位期隔开，其年代近似为23 ka和近似为18 ka。从晚中新世到中更新世，盆地内的大规模沉积模式主要受构造作用控制。相比之下，从中更新世到现在，沉积在坦噶尼喀湖似乎有显着的气候变化所建议的湖平面波动的重复模式。在此期间，盆地充填史的特点是三种类型的存款：“盆地填充”的积累，透镜状的“深湖扇”和“席状披覆”存款的复发协会。由于构造沉降下降条件下沉积物快速充填的结果，连续的低湖水位波动强度随时间而降低。因此，随着构造效应的减弱，气候信号在最近的沉积阶段更加明显。
We present here the initial results of a high-resolution (sparker) reflection seismic survey in Northern Lake Tanganyika, East African Rift system. We have combined these results with data from earlier multichannel reflection seismic and 5-kHz echosounding surveys. The combination of the three complementary seismic investigation methods has allowed us to propose a new scenario for the late Miocene to Recent sedimentary evolution of the North Tanganyika Basin. Seismic sequences and regional tectonic information permit us to deduce the palaeotopography at the end of each stratigraphic sequence. The basin history comprises six phases interpreted to be responses to variations in regional tectonism and/or climate. Using the reflection seismic-radiocarbon method (RSRM), the minimum ages for the start of each phase (above each sequence boundary) are estimated to be: similar to 7.4 Ma, similar to 1.1 Ma, similar to 393-363 ka, similar to 295-262 ka, similar to 193-169 ka, similar to 40-35 ka. Corresponding lowstand lake elevations below present lake level for the last five phases are estimated to have been: similar to 650-700 m, similar to 350 m, similar to 350 m, similar to 250 m and similar to 160 m, respectively. The latest phase from similar to 40-35 ka until the present can be subdivided into three subphases separated by two lowstand periods, dated at similar to 23 ka and similar to 18 ka. From the late Miocene until the mid Pleistocene, large-scale patterns of sedimentation within the basin were primarily controlled by tectonism. In contrast, from the mid Pleistocene to the present, sedimentation in Lake Tanganyika seems to have responded dramatically to climatic changes as suggested by repeated patterns of lake level fluctuations. During this period, the basin infill history is characterized by the recurrent association of three types of deposits: 'basin fill' accumulations; lens-shaped 'deep lacustrine fans'; and 'sheet drape' deposits. The successive low-lake-level fluctuations decreased in intensity with time as a consequence of rapid sedimentary filling under conditions of declining tectonic subsidence. The climate signal has thus been more pronounced in recent sedimentary phases as tectonic effects have waned.