کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
4692885 | 1636831 | 2012 | 9 صفحه PDF | دانلود رایگان |
![عکس صفحه اول مقاله: Three-dimensional geometry and fabric of shear deformation-bands in unconsolidated Pleistocene sediments Three-dimensional geometry and fabric of shear deformation-bands in unconsolidated Pleistocene sediments](/preview/png/4692885.png)
We present an outcrop-based study on the 3D geometry and fabric of shear deformation-bands that developed in Middle Pleistocene, unconsolidated, glaciolacustrine delta sands in northern Germany. With a three dimensional model of a 3.38 m³ outcrop we demonstrate deformation band geometries, analysis of band thickness and along-strike juxtaposition maps of beds against the deformation bands. The parallel thicknesses of the shear deformation-bands ranges from 0 to 8 cm, with a mean of 1.5 cm. Analysis of along-strike band displacement of intersecting shear deformation-bands proves the true displacement vector is close to dip-slip movement. The shear deformation-bands compensated a large lateral extension of ca. 10–20%. Though the deformation is unevenly distributed, this is a very high amount of deformation and this has wide implications when upscaled to the whole outcrop or locality. Grain size within the shear deformation-bands is identical to the grain-size distribution of the parent sediment. Conventional Fry analysis of grains in the shear deformation-bands shows strain ratios of 1.4. This, however, is an artifact of bulk grain-shape, since a normalized Fry plot shows strain close to unity. We observe a two-stage calcite overgrowth on the grains of the deformation band (radial sparite followed by micrite). We thus propose grain-boundary sliding (possibly aided by calcite-rich fluids) to be the dominant deformation mechanism. The deformation bands are very likely the product of young basement tectonics and may be related to movements in the crest of a salt anticline. In the study area, the observation of young basement tectonics is a novelty.
► Outcrop based 3D model of shear deformation-bands
► Restored cross-sections to quantify the amount of extension, compensated by the formation of deformation-band faults
► Strain analysis
► juxtaposition maps
Journal: Tectonophysics - Volumes 518–521, 20 January 2012, Pages 84–92