The redistribution of sediment by lacustrine processes operating in Green Lake, Teton County, Wyoming was studied in order to determine the factors which control sediment entrapment and to evaluate the effectiveness of entrapment as a control on downstream sediment mineralogy. Sediment patterns in the lake were identified by means of factor analysis of heavy minerals data. The results of these analyses show that detritus from sedimentary sources to the west is trapped in the lake, whereas sediment derived from Precambrian crystalline rocks to the east is carried through the lake and out the outlet. These relations are controlled by drainage slope and pattern, lake geometry and bathymetry, and source lithology. Because of selective sediment entrapment, it would not be possible to predict the source rock compositions in Green Lake Basin by examining the mineralogy of downstream sediments.