Submarine slump masses and intraformational breccias at the type Devonian Devils Gate Limestone in central Nevada originated because of fluidization of selected layers in a partially lithified, turbidite-dominated sediment column. Fluidization and the development of shear planes that border the slumps resulted from increased microbially generated gas pressures in a sediment column sealed on top. In an incipient slump mass, thin ductile beds above and behind the slump nose were stretched and thinned between more fluid layers. In some cases, a sag may have formed in the surface sediments, but not necessarily an actual scarp. We suggest that the mechanism of mass movement described herein is a common diagenetic process in the carbonate-slope environment, particularly where sediments and organic decay products have been moved catastrophically from one environment to another.