2006 Volume 112 Issue 5 Pages 331-348
The Samondake Unit in the Neo-Izumi area, central Japan, represents a sandstone-dominant accretionary complex of the Mino Terrane. It is divided into two fault-bounded subunits, the Kuzawadani Subunit on the northeast and the Kouchidani Subunit on the southwest. Although these subunits show different features in deformation grade and lithologic assemblages, they consist largely of contemporaneous deep-marine siliciclastic succession assigned to middle Jurassic. Owing to the penetrative shears oblique to bedding plane at low-angle and lack of available key beds, it was difficult to reconstruct the original lithostratigraphy accurately. The facies study having been carried out on well-exposed and less-sheared sections discriminated seventeen facies and five facies associations (Fa.A-E). Among them, the facies associations A and B are comparable to the channel-fills and lobe-like deposits, respectively. The facies associations C is defined as a marginal facies of deep-marine fan, and includes interlobe and lobe fringe deposits accompanied with sheeted sandstones and mud drapes. The facies associations D and E are assigned to hemipelagic and pelagic sediments on the basin-plain and ocean-floor, respectively. Among them, the facies association B is the most dominant one in the Samondake Unit. This suggests the trench fan as a depositional system of the Samondake Unit.
