Thickness variations across-levee and downchannel in acoustically defined depositional sequences from six submarine channel-levee systems show consistent and quantifiable patterns. The thickness of depositional sequences perpendicular to the channel trend, i.e. across the levee, decreases exponentially, as characterized by a spatial decay constant, k. Similarly, the thickness of sediment at the levee crest decreases exponentially down the upper reaches of submarine channels and can be characterized by a second spatial decay constant, k. The inverse of these decay constants has units of length and defines depositional length scales such that k )1 is a measure of levee width and k )1 is a measure of levee length. Quantification of levee architecture in this way allowed investigation of relationships between levee architecture and channel dimensions. It was found that these measures of levee e-folding width and levee e-folding length are directly related to channel width and relief. The dimensions of channels and levees are thus intimately related, thereby limiting the range of potential channel-levee morphologies, regardless of allocyclic forcing. A simple sediment budget model relates the product of the levee e-folding width and e-folding length to through-channel volume discharge. A classification system based on the quantitative downchannel behaviour of levee architecture allows identification of a Ômid-channelÕ reach, where sediment is passively transferred from the through-channel flow to the levees as an overspilling flow. Downstream from this reach, the channel gradually looses its control on guiding turbidity currents, and the resulting flow can be considered as an unconfined or spreading flow.

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Abstract. Piston cores from the continental margin off Nova Scotia show up to four discrete intervals of "brick-red sandy mud," which are up to 20 cm thick. The ages of these intervals are bracketed by several radiocarbon dates, and three fall in the range 12.5-14.1 ka (radiocarbon years with -0.4 kyr reservoir correction). The youngest dates from -10.4 ka, placing it within the Younger Dryas. The distribution of the beds and their petrographic character indicate a source in the Gulf of Saint Lawrence. The grain size of these beds suggests that they comprise a coarse component transported by ice rafting that diminishes distally and a free component that represents suspension fallout from a surface plume and resulting nepheloid layers. Graded brick-red beds in some cores were probably redeposited from turbidity currents. The lowermost bed on the Laurentian Fan and East Scotian Rise is immediately overlain by a carbonate-rich interval that can be identified all around the margin of the Grand Banks. This interval is correlated with detrital carbonate bed DC-1 in the Labrador Sea and Heinrich event H1 in the North Atlantic. The sequential occurrence of the two beds suggests that they may be a response to the same trigger, probably sea level rise, but that the Gulf of Saint Lawrence source was more easily destabilized.