A Preliminary Experimental Study of Turbidite Fan Deposits: Discussion

Abstract

Parsons et al. (2002) have discussed an experimental study of turbidite fan deposits for understanding lobe switching. Because of perceived importance of turbidite lobes in hydrocarbon reservoirs (Shanmugam and Moiola 1991), this experimental study could be of value to oil industry. Also, experimental studies are primary means of unraveling complexities of process dynamics of turbidity currents and their deposits. This is because other two options, namely, (1) direct observations of turbidity currents in deep sea (e.g., Shepard et al. 1979) and (2) attempts to understand turbidity currents and their fan deposits on basis of outcrop study on land (e.g., Mutti and Ricci Lucchi 1972) have proven to be unsuccessful (e.g., Mutti 1992; Shanmugam 2002). Therefore, experimental study by Parsons et al. (2002) requires close scrutiny. I would like to debate following issues discussed in paper: (1) Reynolds number, (2) grain-size variation, (3) depositional bedforms, and (4) importance of mud. Proper scaling of experimental flows to natural turbidity currents is vital. According to Parsons et al. (2002, p. 626), Reynolds number of bottom-boundary layer in natural turbidity currents is ...often greater than 100..., whereas the Reynolds number of experimental turbidity currents. . .was always much less than unity... Parsons et al. (2002, p. 626) also acknowledged that particle Reynolds number in these experiments is not compatible with values of natural flows. The authors attributed these scaling difficulties to density of particles and viscosity of fluid used in their …