Control by preexisting morphology on layer-bound faults in the southern Qiongdongnan Basin, NW South China Sea

IF 2.6 2区 地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY
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Abstract

The ideal development of layer-bound, polygonal faults occurs in an isotropic stress field. However, some populations of layer-bound faults appear to have originated as ‘polygonal’ faults, but display atypical plan-view fault geometries that suggest development under anisotropic stress conditions. High-resolution 2D/3D seismic data in the southern Qiongdongnan Basin displays three tiers of layer-bound faults with distinct strike variations and complex structural patterns that depart from the geometries of isotropic polygonal fault cells. The lower fault tier displays preferred orientations along E-W, NE-SW, NW-SE directions; the middle fault tier shows a primary E-W orientation and a secondary N-S trend; the shallow tier features strong N-S and E-W orientations. Fault patterns in map view include orthogonal, quasi-polygonal and circumferential geometries, among which the orthogonal pattern is dominant in the shallow fault tier. Several factors are inferred to cause these variable geometrical and structural patterns in layer-bound faults, they are: pre-existing tectonic faults, an uplifted region, local slopes, contourite depressions, and large contourite-related channels. The orthogonal fault patterns have longer E-W orientation parallel to the contourite channels and shorter N-S trends perpendicular to the thalwegs. The presence of submarine channels is suggested to locally deflect the stress orientation, which in turn impacts fault patterns.

南海西北部琼东南盆地南部的层状断层受原有形态的控制
在各向同性应力场中,层状多角形断层是理想的发育状态。然而,一些层状断层似乎起源于 "多边形 "断层,但却显示出非典型的平面断层几何形状,这表明断层是在各向异性应力条件下发育的。琼东南盆地的高分辨率二维/三维地震数据显示了三层断层,这些断层具有明显的走向变化和复杂的构造形态,与各向同性的多边形断层单元的几何形态不同。较低的断层层倾向于东-西、东北-西南、西北-东南方向;中间断层层主要倾向于东-西方向,次要倾向于北-南方向;较浅的断层层具有强烈的北-南和东-西方向。从地图上看,断层形态包括正交、准多角和环向几何形态,其中正交形态在浅层断层中占主导地位。据推断,造成层状断层的几何和结构形态多变的因素主要有:先前存在的构造断层、隆起区域、局部斜坡、等高线洼地以及与等高线有关的大型通道。正交断层的走向与等高线岩槽平行,呈较长的东西走向,而与等高线岩槽垂直的走向则呈较短的南北走向。海底通道的存在使应力方向发生局部偏转,进而影响断层形态。
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来源期刊
Journal of Structural Geology
Journal of Structural Geology 地学-地球科学综合
CiteScore
6.00
自引率
19.40%
发文量
192
审稿时长
15.7 weeks
期刊介绍: The Journal of Structural Geology publishes process-oriented investigations about structural geology using appropriate combinations of analog and digital field data, seismic reflection data, satellite-derived data, geometric analysis, kinematic analysis, laboratory experiments, computer visualizations, and analogue or numerical modelling on all scales. Contributions are encouraged to draw perspectives from rheology, rock mechanics, geophysics,metamorphism, sedimentology, petroleum geology, economic geology, geodynamics, planetary geology, tectonics and neotectonics to provide a more powerful understanding of deformation processes and systems. Given the visual nature of the discipline, supplementary materials that portray the data and analysis in 3-D or quasi 3-D manners, including the use of videos, and/or graphical abstracts can significantly strengthen the impact of contributions.
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