Bi-modal deformation styles in confined mass-transport deposits: examples from a salt minibasin in SE Brazil

D Gamboa, TM Alves - Marine Geology, 2016 - Elsevier
Marine Geology, 2016Elsevier
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 …
Abstract
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.
Elsevier
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