Gunchu Formation : An Indicator of Active Tectonics on an Oblique Convergent Margin

Mechanisms of sedimentary basin formation on active plate margins show enormous diversity reflecting complex tectonic processes. Clastic layers within a basin are an excellent recorder of long-term environmental changes and the mass balance on arc-trench systems. This book is aiming to elucidate the intriguing tectonics of an active margin based on authentic field geology. Recent quantum leaps in geophysical technique have provided us with three-dimensional views of the deep interior of sedimentary basins. To comprehensively understand the geodynamics, however, describing surface processes by means of stratigraphy, sedimentology and structural geology has equal significance because such geologic approaches suggest the time sequence of tectonic events. A case study is presented for an event sedimentary unit filling an asymmetric basin on a large transcurrent active fault bisecting the southwestern Japan arc. The analysis should be thought-provoking for corporate experts, university staffs, graduate and undergraduate students engaged in geologic survey, and should be especially useful to professionals in the field of active tectonics.