Sea-Floor Sunday #50: Saline density flow channel network

This week’s Sea-Floor Sunday is an image from a recent paper from Flood et al. about channel networks on the floor of the Black Sea (you can see the entire paper here).

What I find interesting about this system is that it forms from saline density flows that come from the Bosphorus (the strait that separates the Black Sea from the Sea of Marmara and the rest of the Aegean Sea in the Mediterranean region):

This channel network accommodates the saline density current formed by the Mediterranean inflow. The density contrast between the density underflow and the ambient water mass is … similar to the density contrast ascribed to low-concentration turbidity currents in the deep sea.

This density current is dense because the bottom waters are saltier — so when flows come through the strait into the Black Sea, they flow across the shelf into deeper water. The development of a network of channels and associated landforms are the result.

The bathymetric map below (about 15 km across) nicely images the main channel near the bottom of the image bifurcating towards the north (towards the top of the image).

Channel network, southwestern Black Sea - image ~15 km across (credit: Flood et al. paper in journal Sedimentology; © 2009 International Association of Sedimentologists)

Turbidity currents are also density currents but get the excess density necessary to create an underflow from sediment. Experimentalists often use salt to create density underflows in the lab. This system is essentially a full-scale laboratory for studying the processes and landforms related to channelization of density flows. Although one big difference is that the saline density flows are eroding and redistributing sediment but not delivering additional sediment to the system.

If you are interested in river or deltaic channel patterns you might find this paper interesting.

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FLOOD, R., HISCOTT, R., & AKSU, A. (2009). Morphology and evolution of an anastomosed channel network where saline underflow enters the Black Sea Sedimentology, 56 (3), 807-839 DOI: 10.1111/j.1365-3091.2008.00998.x