Structural and volcanic evolution of the Gregory Rift Valley
Structural and volcanic evolution of the Gregory Rift Valley
复制标题
格雷戈里裂谷的结构和火山演化
DOI：
10.1144/gsl.sp.1978.006.01.05
复制
发表时间：
1978
期刊：
影响因子：
--
通讯作者：
B. C. King
中科院分区：
文献类型：
--
作者：
B. C. King
东非裂谷系从红海向南延伸约3000公里。在东非，它以西部裂谷和东部裂谷为代表，其中格雷戈里裂谷是肯尼亚和坦桑尼亚北方的一部分。格里高利裂谷形成于中新世早期，是大陆分水岭上的一个向下弯曲地带，沿着大陆分水岭，地表起伏较大（高达2000米）。随后的断层作用产生了一个宽约80公里、长约450公里的地堑，在地堑的北部和南部，断层向外张开，覆盖了更广阔的区域。火山活动并不局限于裂谷，而是在中新世向西发展，在上新世-更新世至近代向东发展。在裂谷内部，火山活动从北部开始，并在上新世向南延伸，而构造和火山活动后来都倾向于限制在一个中心地带，从汉宁顿湖向北形成一个狭窄的轴向槽。火山活动和沉积作用的爆发，大部分或全部填满了下陷的海槽，但只是在更新世，通过肩部的隆起和底部的下沉，才形成了现在的裂谷形态。次火山表面沿裂谷肩部的平均海拔高度约为沿着1500米;其最大深度可能是从巴林戈湖附近向南，相当于绝对位移约4公里。在约80公里的裂谷宽度上可能发生了约8公里的地壳伸展，但没有地壳分离的证据。
The East African Rift System extends southwards from the Red Sea for a distance of about 3000 km. Within East Africa it is represented by the Western Rift and the Eastern Rift, of which the Gregory Rift Valley is that part lying within Kenya and northern Tanzania. The Gregory Rift Valley was initiated in early Miocene times as a downwarp along the continental watershed on a land surface having considerable relief (up to 2000 m). Subsequent faulting produced a graben about 80 km wide and some 450 km in length, to the north and south of which the faults splay outwards over much broader zones. Volcanic activity was not confined to the Rift, but developed both to the west in the Miocene and to the east from Plio-Pleistocene to Recent times. Within the Rift itself volcanism commenced in the north and extended to the south in the Pliocene, while both tectonic and volcanic activity tended later to restriction within a central zone, which from Lake Hannington northwards formed a narrow axial trough. Episodes of volcanism and sedimentation largely or wholly infilled the downwarping trough, but only in the Pleistocene, by uplift of the shoulders and downfaulting of the floor, was the morphology of the present Rift Valley achieved. The altitude of the sub-volcanic surface averages about 1500 m along the shoulders of the Rift; its greatest depth below the floor may be southwards from near Lake Baringo, corresponding to an absolute displacement of some 4 km. About 8 km of crustal extension over about 8o km of rift width may have occurred, but there is no evidence for crustal separation.