Depositional evolution of confined turbidite basins

Confined turbidite basins are a common feature of many structurally complex continental slopes, but their depositional history has never been characterized using outcrop data. A synthesis of outcrop data from Tertiary Alpine basins with subsurface data from the Gulf of Mexico indicates that the progressive infill of confined turbidite basins can be characterized by four phases: (1) Flow ponding, where incoming flows are totally trapped, depositing thick, sheet-like sand-mud couplets. (2) Flow stripping, where the finer, more dilute portion of the flow is able to escape over the confining topography to be deposited elsewhere, causing increased sand/mud ratio within the basin. (3) Flow bypass, either by flows traversing over the filled basin or by switching of feeder channels away from the basin; the former resulting in incision, the latter in abandonment. (4) Blanketing, of the basin and surrounding topography due to base-level rise; this usually takes the form of meandering channel-levee complexes with low sand/mud ratios. Confined basin sequences may be stacked during the episodic growth of the confining topography to a basin, and may appear similar to sea-level-induced depositional sequences.