Experiment on Turbidity Currents and Their Deposits in a Model 3D Subsiding Minibasin

Abstract

Abstract Minibasins on the continental slope are formed by the movement of salt or mud layers in the subsurface. The north slope of the Gulf of Mexico (GOM), for example, is riddled with salt-withdrawal minibasins ranging in scale from a few kilometers to tens of kilometers. These minibasins are often connected to each other by channels, which have been carved through the compensational ridges between basins by turbidity currents. The same turbidity currents tend to fill the minibasins with their deposits (turbidites). The process of deposition in a minibasin is not directly observable in the field. It can, however, be modeled at laboratory scale. This paper reports on the results of the first laboratory experiment on deposition from turbidity currents in a 3D minibasin undergoing subsidence. The basement of the experimental basin underwent bowl-like subsidence for the first half of the experiment: subsidence was turned off for the second half. Thirty-two individual turbidity-current events were introduced into the basin, including pulse-like and continuous flows. The first continuous flow created a short leveed channel in the proximal part of the basin; the channel was obliterated by subsequent flows. Dip and strike views of the deposit bear remarkable resemblances to corresponding views from a high-resolution seismic survey of a GOM minibasin (Basin 4, Brazos Trinity Intra-Slope System, GOM continental slope). Scaleup of the flows and geometry to field scale using the principles of Froude similarity suggest that the experiment provides a reasonable representation of the processes that could be expected in nature. The experimental turbidity currents appear, however, to have been more strongly depositional in the proximal region than deposits found in the field.