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首页> 外文期刊>Geosphere >Polyphase kinematic history of transpression along the Mecca Hills segment of the San Andreas fault, southern California
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Polyphase kinematic history of transpression along the Mecca Hills segment of the San Andreas fault, southern California

机译：南加州圣安德烈亚斯断层山丘山区多相运动历史，南加州

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Miocene–Pliocene sedimentary rocks in the Mecca Hills, southern California, were uplifted and deformed by transpression along a restraining bend in the San Andreas fault trace between the Orocopia and San Bernardino Mountains in Pleistocene time. This paper presents field evidence for three stages of structural evolution of a complex, asymmetric wedge-like flower structure, expressed as: (1) subhorizontal en échelon folds and faults oblique to the San Andreas fau (2) steeply plunging folds subparallel to the San Andreas fau and (3) folds and thrust faults fully parallel to the San Andreas fault. We argue that the resulting flower-structure deformation formed successively from early distributed transpression through full (?) strain partitioning, rather than from active, synchronous, strike-slip–forming movements, as expected. The model is supported by crosscut relations of major folds and faults and strain estimates from minor conjugate shear fracture sets. The polyphase evolution initiated on a steep right-lateral strand of the San Andreas fault, producing thick fault gouge. Then, the adjacent Neogene strata were folded en échelon outward in a uniformly distributed simple shear strain field. The subsidiary Skeleton Canyon fault formed along a restraining bend that localized right-lateral shearing along this fault, and reshaped the en échelon folds into steeply plunging folds almost parallel to the San Andreas fault in a nascent partly partitioned strain field. The final kinematic stage generated SW-verging folds and thrust faults trending parallel to the San Andreas fault and decapitated the en échelon folds and faults. The switch from early, distributed strike-slip to late-stage regional slip-partitioned shortening (fold-thrust) deformation may have been locally induced by the bending geometry of the fault. The polyphase structures were active in successive order to balance the driving forces in one or more critical-angled transpressional and fold-and-thrust uplift wedges. Fault-related shortening, uplift, and erosion are still controlled in the Mecca Hills by combining and adjusting the wedges with low convergence angle, transpression, and lateral crustal motion in a San Andreas fault plate scenario. Our model, therefore, addresses a more nuanced view of a polyphase flower-structure system and highlights the need to more carefully sort out spatially and temporally different kinematic data as a basis for analog and numerical modeling of transpressional uplift areas.
机译：麦加山脉，南加州麦加山沉积岩沉积岩被沿着Orocopia和San Bernardino山脉在更新世时期的San Andreas故障轨迹中升压和变形。本文介绍了三个阶段的结构演变的特点证据，表示为：（1）Subohorizo​​NealENÉchelon折叠和故障倾斜于圣安德烈亚斯故障; （2）陡峭的褶皱以San Andreas Fault分开; （3）与San Andreas故障完全平行的折叠和推力故障。我们认为，通过完全（α）应变分配，而不是从最早的分布式经变压缩，而不是从主动，同步，击球形成运动，而不是主动，同步，撞击成型运动所形成的花结构变形。来自次缀合形剪切骨折组的主要折叠和故障和菌株估计的横切关系支持该模型。在San Andreas故障的陡峭右侧链中发起的多相进化，产生厚的故障凿孔。然后，在均匀分布的简单剪切应变场向外折叠相邻的Neogene Strata。沿着抑制弯曲形成的子公司骨架峡谷故障，沿着该故障局部右侧剪切，并将Zhéchelon折叠成陡峭的褶皱，几乎平行于初始分隔的应变场中的SAN Candreas故障。最终的运动阶段产生了与San Andreas故障平行的SW-Verging折叠和推力故障，并斩首Zhelon折叠和故障。从早期的弯曲几何形状局部地诱导了从早期，分布式击球滑动到后期区域滑动分区缩短（折叠式推力）变形。多相结构的连续顺序是有效的，以平衡一个或多个临界变压和折叠和推动隆起楔形的驱动力。通过组合和调节San Andreas故障板场景中的低收敛角，变形和横向地壳运动，仍然在Mecca Hills中控制了与错误缩短，隆起和侵蚀仍然控制。因此，我们的模型解决了多相花卉结构系统的更细注的视图，并且突出了更仔细地将空间和时间不同运动数据进行了更仔细地对跨压隆起区域的模拟和数值建模的基础。

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