Relation of intermittent occurrence of older debris flows to block uplift : Gozu debris flow

Debris flow deposits, that occurred during the Middle Pleistocene to the present, are widely distributed at the western foot of the Gozu Mountains. They are called the Gozu debris flow deposits. The stratigraphy and geohistorical development of debris flows have been outlined by TAKAHAMA and NOZAKI (1981). The Gozu debris flow deposits is divided into the following seven gravel beds in ascending order; GD I and GD II (the Middle Pleistocene), GD III, GD IV and GDV (the Upper Pleistocene) and GD VI and GD VII (the Holocene). The characteristics of the Gozu debris flow development is that the large-scale debris flows occurred intermittently during the Middle Pleistocene and the early Late Pleistocene times, with a long periods of “suspension”. Their deposits are GD I, GD II and GD III. During the “suspending periods”, these gravel beds were weathered intensely and their depositional surface were dissected. The Gozu Mountains made stepped block upheaval, with the maximum uplift amounting to around 1,000 meters since the Middle Pleistocene time up to the present (TAKAHAMA, 1984). The intense faulting and block uplift caused the strong erosive rejuvenation leadig to the intermittent occurrence of large-scale debris flows