The onset, development, and break-down of stratification in an environment of highly variable turbulence is described. Observations in Spencer Gulf, South Australia, indicate that anomalous tidal characteristics cause the shutdown of a major component of turbulence at fortnightly intervals. This encourages the formation of stratification by horizontal advection of density. From time series observations at a single point in the gulf, the development of stratification is correlated with periods of substantially reduced rates of stirring, from wind and tidal stresses, and a threshold value of the combined rate of energy input required to maintain mixed conditions is derived. The formation of stratification relaxes viscous constraints, and a buoyancy/inertia circulation rapidly develops, with associated velocities of ~0.2 m s-1. After an inertial period, geostrophic adjustment turns the circulation into a large-scale horizontal cyclonic gyre which has important implications for dispersion within the gulf and for the exchange of properties between gulf and shelf. Boundary friction effects on the advancing gravity currents are also clearly evident. ¿American Geophysical Union 1987