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    • Keywords


      Fold-and-thrust belts; sandbox experiments; basal friction; surface slope; surface erosion.

    • Abstract


      Sandbox experiments are used to study frontal thrust fault spacing, which is a function of physical properties within the thrust wedge. We consider three styles of thrust progression in mono-vergent wedges: Style I, II and III. In Style I, frontal thrusts progress forelandward, maintaining a constant spacing, whereas Style II and Style III progression show increasing and decreasing spacing, respectively. The three styles are shown as a function of the following factors: basal friction (𝜇b), initial surface slope (𝛼) and basal slopes (𝛽), and surface erosion. For high 𝜇b (∼0.46), thrust progression occurs in Style II when 𝛼 > 2° and 𝛽 > 0.5°, and in Style III when 𝛼 and 𝛽 are high (𝛼 < 2° and 𝛽 < 0.5°). Style II transforms to Style I when the wedge undergoes syn-thrusting surface erosion. In contrast, low-basal friction (𝜇b = 0.36) gives rise to either Style I or III, depending on the magnitudes of 𝛼 and 𝛽. Conditions with 𝛼 = 𝛽 = 0 developed Style I, whereas Style III in conditions with any non-zero values of 𝛼 and 𝛽. In this case, surface erosion caused the process of thrust progression unsteady, and prompted outof-sequence thrusting in the wedge. This study finally presents an analysis of the three styles, taking into account the following two parameters: (1) instantaneous increase of hinterland thickness (𝛥 H2/He) and (2) forelandward gradient of wedge thickness (𝛿 H/𝛿x). Experimental data suggest that thrust sequences develop in Style II for low 𝛿 H/𝛿x and large 𝛿 He/He values and, in Style III as either 𝛿 H/𝛿x increases or 𝛥 He/He drops.

    • Author Affiliations


      Puspendu Saha1 Santanu Bose1 Nibir Mandal2

      1. Experimental Tectonics Laboratory, Department of Geology, University of Calcutta, Kolkata 700 019, India.
      2. Department of Geological Sciences, Jadavpur University, Kolkata 700 032, India.
    • Dates

  • Journal of Earth System Science | News

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      Posted on July 25, 2019

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