Stiffnites. Part I

Abstract

I identify the early phases of a particular kind of gravity-driven submarine sediment flow, that I have named immature stiffnite. The mature flow dynamics is originally presented in an accompanying report, referred to here as Pareschi [2011]. An immature stiffnite is constituted by a liquefied flowing mixture of muddy to sandy particles (sea floor ooze) in contact or in close proximity to each other, with inter-granular pores saturated in water. Sliding hard grains, including microshells, fragment during its motion. To infer the dynamics of an immature stiffnite, I consider deposits from the literature. In the literature, however, those deposits have not been well defined and they have often been confused with turbidites. Turbidites are water currents with suspended fine sediments that progressively settle-out down an incline. Stiffnites are triggered by events that create overpressure in intergrain pore water of the sea floor over wide areas. A peak of magnetic susceptibility can occur at the base of an immature stiffnite deposit.