Anomalously steep submarine channel segments reveal varied styles of erosion

What is it about?

Knickpoints or knickzones in river channels are reaches that are anomalously steep. They can be formed by local movement on faults or folds, or arise from strata that are more resistant to erosion. In this article, multibeam sonar data from many different margins are compiled to look at the varied shapes of submarine channel knickpoints. In some slopes, such as in the Gulf of Alaska, some knickpoints lie up-slope ("up-stream") from where faults or folds are most likely to have initiated them. These knickpoints have therefore migrated, a feature of river knickpoints where bedrock erosion rate can be related to channel gradient. In the Barbados accretionary prism, in contrast, knickpoints appear as smooth versions of the surrounding seabed with much less evidence of migration. In these cases, erosion and deposition may be more related to bedload transport by turbidity currents passing down the channels, leaving the channel bed to follow a diffusive-type evolution, much as do some gravel- or sand-floored channels on alluvial fans on land.

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Photo by Cosmic Timetraveler on Unsplash

Photo by Cosmic Timetraveler on Unsplash

Why is it important?

There are much fewer data available to constrain erosion processes in submarine slope settings than for subaerial streams. However, the morphologic similarities suggest that the erosion process may not be so dissimilar, even if the dynamics of turbidity currents is complicated by gain or loss of sediment load, amongst other factors.