Following the threads of channels—from river valleys to the sea floor

Ajay Limaye, Post-Doctoral Research Associate, St. Anthony Falls Laboratory, University of Minnesota

Channels are central actors in planetary evolution, shaping landscapes and the sedimentary record. Viewed from above, channels show varied patterns that are distinguished by the number of threads, or pathways, for fluid flow. River channels on Earth’s surface and channels on the seafloor, which convey sediment-laden density currents, show strikingly similar forms. Yet the strength of the analogy between the subaerial and submarine channels—including their formation conditions, morphology, and dynamics—is only partially understood. This uncertainty owes in part to the complex geometry of channels with multiple threads, which has inhibited systematic mapping. In this talk I will first present a new approach, based on reduced-complexity flow modeling, to capture the geometry of multithread channel networks. I will then apply this approach to compare and contrast multithread rivers and submarine channels formed in scaled laboratory experiments. The experiments indicate that compared to rivers formed under similar conditions, submarine channels are approximately twice as deep. The submarine channels also show significant decreases in channel depth and transitions to sheet flow downstream. Measurements of channel migration and aggradation rates suggest that beyond their superficial differences, single-thread and multi-thread channels yield fundamental differences in the architecture of marine sedimentary rocks.