Publications

Oblique convergent deformation has notoriously generated areas with structural complex geometry and patterns resulting from the role of various local parameters that control stress distributions. Therefore, a special technique is needed for understanding and solving such a problem, in particular to relate fault geometry and its evolution. The main purpose of this paper is to present results of integrated techniques using a balancing crosssection with analogue sandbox modeling (ASM) in conducting 3D structural analysis in the Seram Fold-Thrust-Belt (FTB). ASM is one of the types of analogue modeling in geological sciences in which the main purpose is simulating a deformation style and structural evolution of the sedimentary basin. ASM is one of the effective ways in conducting physical modelling, and evaluates complex reformation of sedimentary rocks. In the ITB sandbox-modeling laboratory, the experiment is conducted using several standard, custom-built, sandbox apparatus. The apparatus used in this experiment is an opentopped glass box with fixed external walls and one or two moveable internal walls, pushed by screw jacks driven at a constant velocity by a stepper motor. The dimensions of the box are sufficiently large to ensure that a large part of the model escapes boundary effects. The sand pack is made of thin alternating colored layers, which allow the identification of faults and folds on cross-sections as well as a map view. In this study, we used natural dry quartz sand with a Navier-Coulomb rheology and angle of internal friction of about 300, similar to many sedimentary rocks combined with gypsum for representing limestone layers. The * Institute of Technology Bandung ** NIKO Energy Indonesia quartz sand is part of the Ngrayong Formation, collected from natural outcrop in East Java. The Seram FTB is characterized as a broard deformation zone distributed in a NW-SE trend, more than 400 km long and ~100 km wide. Our recent work indicates that the fault pattern changes along strike from west to east, accompanied by a change in the dip of the faults from NE to SW. Coss-section balancing shows that this belt experienced large amounts of shortening, which in some locations reached 50%. The results of integrated study indicated that deformation in the Seram FTB, including the Seram trough, is best explained using an oblique convergent system. Two of the modelling variables clearly affected the ASM results, these are stratigraphic variation and preexisting basement fault geometry. Lithologic variation was the main influence on the frequency of faulting developments, and pre-existing basement fault geometry was the primary influence on modelling results. Keywords: sandbox modelling, balanced crosssection, Seram Fold-Thrust Belt, oblique convergent