Abstract

Sandbox analogue modeling is a powerful tool to observe geometry of structural styles and to understand structure development resulting from deformation of sedimentary rock. This approach is very useful for evaluating deformation processes within sedimentary basin particularly in relation to hydrocarbon prospect. In this paper, we demonstrated the result of modeling structural development within the thrust-fold-belt, with special case study of the Cimanintin area, Sumedang, West Java. In general, the geology of this area from younger to older made of Cisaar Formation, Cinambo Formation, and Cantayan Formation. These formations have been strongly deformed forming series of thrust-fold system as a result of northward directed compressional mechanism. The exact orientation of major thrust-fold-belt is WNW-ESE trending suggesting NNE-SSW direction of shortening.

Sandbox modeling was conducted in laboratory after conducting detailed fieldwork. Therefore, the main purpose of this modeling is to replicate the natural structural styles and pattern of the convergent tectonics environment. The modeling setting was made of alternating layers of dry colored quartz sands which has internal angle of friction (F) 22°, with various grain sizes to represent the different sizes of the sedimentary units. This natural sand grain is suitable enough for simulating the brittle deformation in the upper crust. Sandbox modeling was conducted using a rectangular apparatus with dimension 50 × 40 × 20 cm, containing two glass-sided with moving wall powered by motor-drive and a fix wall located in front of the moving wall. To reflect the field condition, the sediment thickness and the area of interest were scaled to appropria te size.

The result of the modeling conclude that the development of the structural geometry are influenced by variables, such as the thickness of the sediment package, grain size, and the width of the area. In addition, sandbox analogue modeling shows excellent correlation with natural deformation in which they show good geometry similarity to the structure that developed in the thrust-fold-belt of Cimanintin area.