ABSTRACT

The presence of submarine fans at the mouths of many submarine canyons suggests that a turbid current traveling down a submarine canyon disperses into a fan shaped flow as it leaves the mouth of the canyon and begins to move out over the basin floor. Thus, a fan shaped deposit results as the velocity of the flow wanes. The authors hypothesize that the grain fabric of the deposit will reflect the fan like flow pattern by having a preferred grain orientation that is also fan shaped.

It is further hypothesized that observed deviations between the trends of sole marks and the mean trend of elongate sand grains at the same place in the same bed, as reported by Spotts and Weser (1964), is due to a change in the flow path of the turbid current when it gradually decreases in velocity as it moves out across the fan. In such a case the sole marks are produced in the early phase of the flow whereas the grain alignment occurs in a later phase.

Submarine fans were experimentally produced by turbid current action in a small plexiglass tank. A fabric study of the fan deposit revealed that significant preferred sand grain orientation was produced by the depositing current. The orientation pattern within the fan is directed radially away from the mouth of the submarine canyon from which the current emerged. Attempts to study the initial flow direction of the turbid current (that part of the current which supposedly forms sole marks) were unsuccessful.