Temporal variation in counterclockwise vertical-axis block rotations across a rift overlap zone, southwestern Ethiopia, East Africa

IF 2.7 3区 地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS
A. Erbello , G. Dupont-Nivet , T. Kidane , N. Nowaczyk , M. Sudo , D. Melnick , B. Bookhagen , S. Brune , G. Corti , G. Gecho , M.R. Strecker
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引用次数: 0

Abstract

The southward propagation of the southern Main Ethiopian Rift (sMER) and the northward propagation of the Kenya Rift have generated the Broadly Rifted Zone (BRZ), a ∼ 40-km-wide region of extensional overlap between the Chew Bahir Basin-Gofa Province and the sMER. However, the tectonic interaction between these propagating rifts is not well-understood. We present new paleomagnetic and geochronologic data from Eo–Oligocene (45–35 Ma) and Miocene (18–11 Ma) volcanic and sedimentary rocks from the BRZ. Rock magnetic, alternating field and thermal demagnetization experiments indicate simple titanomagnetite mineralogies carrying a characteristic remanent magnetization from which straightforward magnetization directions were obtained. Site-mean paleomagnetic directions obtained from the analyzed samples reflect stable normal and reversed polarity directions. A comparison of the mean directions obtained for the Eo–Oligocene and Miocene rocks relative to the pole for stable South Africa at the corresponding ages reveals a significant counterclockwise (CCW) rotation of ∼11.1° ± 6.4° and insignificant CCW rotation of ∼3.2° ± 11.5°, respectively, reflecting a decrease in the extent of block rotations through time. Our results are consistent with the regional migration patterns of deformation during rifting. In the context of the regional tectonic evolution toward a narrow zone of extension, much of the deformation associated with block rotations probably occurred prior to the final stages of the emplacement of the Miocene volcanic flows. In light of the structural fabrics in the basement rocks exposed in the sMER, the observed CCW block rotations were likely accompanied and aided by the reactivation of NW-SE-striking basement heterogeneities, supporting the notion that inherited crustal-scale structures play a significant role during rifting across the BRZ.
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来源期刊
Tectonophysics
Tectonophysics 地学-地球化学与地球物理
CiteScore
4.90
自引率
6.90%
发文量
300
审稿时长
6 months
期刊介绍: The prime focus of Tectonophysics will be high-impact original research and reviews in the fields of kinematics, structure, composition, and dynamics of the solid arth at all scales. Tectonophysics particularly encourages submission of papers based on the integration of a multitude of geophysical, geological, geochemical, geodynamic, and geotectonic methods
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