Steady rifting in northern Kenya inferred from deformed Holocene lake shorelines of the Suguta and Turkana basins
Steady rifting in northern Kenya inferred from deformed Holocene lake shorelines of the Suguta and Turkana basins
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从苏古塔和图尔卡纳盆地变形的全新世湖岸线推断肯尼亚北部的稳定裂谷
DOI：
10.1016/j.epsl.2012.03.007
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发表时间：
2012
影响因子：
5.3
通讯作者：
Tiercelin JJ
中科院分区：
文献类型：
--
作者：
Melnick D;Garcin Y;Quinteros J;Strecker MR;Olago D;Tiercelin JJ
不同时间尺度上活动裂谷变形速率的比较，可能有助于破译其结构演化，控制机制，沉积环境随时间的演变变化。在这里，我们使用变形的湖泊岸线在肯尼亚北方的苏加塔和图尔卡纳盆地的应变标志，估计在103- 104年的时间尺度的变形率，并将它们与跨越101- 107年的速率。这两个盆地今天都是内部排水的，但直到7至5 kyr湖泊水位分别高出300和100米，通过连接它们与尼罗河排水系统的溢流槛的高度来维持。常年高水位的湖泊形成了最高水位的海岸线--一种独特的地貌特征，几乎连续数十公里。我们在裂谷沿着100 km以上的45个地点测量了这个地貌标志的高程，并使用溢流槛作为垂直基准。薄壳弹性和热力学模型预测，该地区的快速均衡反弹与湖平面福尔斯下降，直到2kyr前持续到10米。沿四条裂谷正剖面的全新世累积落差速率为沿着6.8-8.5mm/yr，若考虑均衡回弹，则为7.5-9.6mm/yr。假设断层倾角为55-65°，从地震反射剖面推断，我们得到的伸展速率为3.2- 6 mm/年（包括现场测量、断层倾角和年龄的不确定性），或考虑回弹的3.5-6.7mm/年。我们的估计是一致的，在不确定性，4- 5.1毫米/年的现代板块运动学模型和板块重建预测自320万年以来的扩展速率。全新世的应变速率为10− 15 s − 1，与106年尺度的估计值相似，但比107年尺度的估计值高出一个数量级。这与板块边界的持续局部化和变窄是一致的，这意味着限制肯尼亚裂谷的岩石圈块体相对刚性。在稳定的伸展速率下增加的应变速率表明，随着伸展和地壳减薄幅度的增加，区域过程的作用，如火山作用的削弱，成为主导的远场板块构造控制的解体过程和从大陆裂谷向海洋扩张的过渡。
A comparison of deformation rates in active rifts over different temporal scales may help to decipher variations in their structural evolution, controlling mechanisms, and evolution of sedimentary environments through time. Here we use deformed lake shorelines in the Suguta and Turkana basins in northern Kenya as strain markers to estimate deformation rates at the 103–104yr time scale and compare them with rates spanning 101–107yr. Both basins are internally drained today, but until 7 to 5kyr lake levels were 300 and 100m higher, respectively, maintained by the elevation of overflow sills connecting them with the Nile drainage. Protracted high lake levels resulted in formation of a maximum highstand shoreline — a distinct geomorphic feature virtually continuous for several tens of kilometers. We surveyed the elevation of this geomorphic marker at 45 sites along >100km of the rift, and use the overflow sills as vertical datum. Thin-shell elastic and thermomechanical models for this region predict up to ~10m of rapid isostatic rebound associated with lake-level falls lasting until ~2kyr ago. Holocene cumulative throw rates along four rift-normal profiles are 6.8–8.5mm/yr, or 7.5–9.6mm/yr if isostatic rebound is considered. Assuming fault dips of 55–65°, inferred from seismic reflection profiles, we obtained extension rates of 3.2–6mm/yr (including uncertainties in field measurements, fault dips, and ages), or 3.5–6.7mm/yr considering rebound. Our estimates are consistent, within uncertainties, with extension rates of 4–5.1mm/yr predicted by a modern plate-kinematic model and plate reconstructions since 3.2Myr. The Holocene strain rate of 10−15s−1is similar to estimates on the ~106yr scale, but over an order of magnitude higher than on the ~107yr scale. This is coherent with continuous localization and narrowing of the plate boundary, implying that the lithospheric blocks limiting the Kenya Rift are relatively rigid. Increasing strain rate under steady extension rate suggests that, as the magnitude of extension and crustal thinning increases, the role of regional processes such as weakening by volcanism becomes dominant over far-field plate tectonics controlling the breakup process and the transition from continental rifting to oceanic spreading.
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影响因子：
2.9
作者：
D. Hendrie;N. Kusznir;C. Morley;C. Ebinger
通讯作者：
D. Hendrie;N. Kusznir;C. Morley;C. Ebinger
影响因子：
5.3
作者：
Garcin, Yannick;Melnick, Daniel;Tiercelin, Jean-Jacques
通讯作者：
Tiercelin, Jean-Jacques
肯尼亚图尔卡纳裂谷的结构风格
DOI：
--
发表时间：
1988
期刊：
影响因子：
--
作者：
Thomas J. Dunkelman;J. Karson;B. Rosendahl
通讯作者：
B. Rosendahl
吉布提阿萨尔裂谷的当代、全新世和第四纪变形：对缓慢扩张的山脊力学的影响
影响因子：
--
作者：
R. Stein;P. Briole;J. Ruegg;P. Tapponnier;F. Gasse
通讯作者：
F. Gasse
肯尼亚北部裂谷地壳结构的综合地球物理研究：对梅嫩盖地区地热能勘探的启示
影响因子：
64.8
作者：
N. Mariita
通讯作者：
N. Mariita