松江市島根町須々海海岸の中新統牛切層に見られる重力流堆積物(予報)

その他

Two types of gravity flow deposits were identified in outcrops of the Miocene Ushikiri Formation（middle to lower slope deposit）exposed along the Susumi coast, Matsue, Shimane Prefecture. The first type of sandstones contain turbidite, debrite and, in some cases, slumped deposit. The second type of beds display Bouma Ta-b character and were deposited from turbidity currents. Thin debrites are also seen in the top of some beds.
The debrite covering turbidite sandstone may have deposited from debris flow developed through the propagation of turbidity flow by supplying sediment to the flow via injection of liquefied substrata, or by simultaneous slumping. The absence of the debrite in the upper part can be explained by the scale of the flows being insufficient to cause liquifaction of substrata , slumping or erosion of substrata , and flattening of the topography due to sediment aggradation that suppresses gravitational effect such as slumps. Further detailed tracing of the individual sandstone beds in this formation may yield clues for the detailed evolutionary processes of gravity flows in the slope environment.