Bi-modal deformation styles in confined mass-transport deposits: examples from a salt minibasin in SE Brazil
Bi-modal deformation styles in confined mass-transport deposits: examples from a salt minibasin in SE Brazil
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DOI：
10.1016/j.margeo.2016.06.003
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发表时间：
2016-09
期刊：
影响因子：
2.9
通讯作者：
D. Gamboa;T. Alves
中科院分区：
文献类型：
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作者：
D. Gamboa;T. Alves
高质量的三维地震数据揭示了巴西东南部（圣埃斯皮里图盆地）的一个盐小型盆地中填充的大量搬运沉积物的双峰变形样式。我们分析了在同一中新世地层间隔内的三个大规模运输沉积物，以及全新世地层中的四个沉积物。我们的解释表明，变形的质量传输存款有关的长轴方向。结果，它们被分为两种类型：a）类型1具有平行于移动方向的长轴，并且显示出显著的内部变形; B）类型2具有垂直于移动方向的长轴，是高度不均匀的，并且包括大的未变形板。第二类物质搬运型矿床的长轴与边界断层和盐构造的走向平行。大多数的质量传输存款显示强烈的变形在其端壁，和相对较短的再动员距离推断为类型1和2。在研究区，块状迁移沉积物的侵位时间受相邻盐脊的生长控制。在第二阶段，小盆地的北方轴向地区的早期盐运动向南转移。全新世物质搬运沉积表明东部和西部盐脊交替生长。我们的研究结果表明，详细的地震地层分析是了解盐小型盆地中物质运输沉积变形的时间和幅度的关键。建议的分类方法可适用于大陆边缘和湖泊环境中的MTD。
High-quality 3D seismic data reveal bi-modal deformation styles in mass-transport deposits filling a salt minibasin in SE Brazil (Espírito Santo Basin). We analyse three mass-transport deposits within the same Miocene stratigraphic interval, and four others in Holocene strata. Our interpretation reveals that deformation in the mass-transport deposits relates to their long-axis orientation. As a result, they are divided into two types: a) Type 1 have long axes parallel to the direction of movement and show significant internal deformation; b) Type 2 have long axes perpendicular to the direction of movement, are highly heterogeneous and include large undeformed slabs. The long axes of Type 2 mass-transport deposits are parallel to the strike of bounding faults and salt structures. The majority of mass-transport deposits show intense deformation at their headwalls, and relative short remobilisation distances are inferred for both Types 1 and 2. In the study area, the timing of emplacement of mass-transport deposits was controlled by the growth of adjacent salt ridges. Earlier halokinesis in the northern axial areas of the minibasin shifted southwards in a second stage. Holocene mass-transport deposits suggest alternating growth of the eastern and western salt ridges. Our results show that detailed seismic-stratigraphic analyses are a key to understanding the timings and magnitude of deformation of mass-transport deposits in salt minibasins. The classification proposed can be applied to MTDs on continental margins and in lacustrine settings.