Erosion at inception of deep-sea channels

Abstract

We present a general model for channel inception and evolution in the deep sea by integrating observations from two complementary datasets: (1) high-resolution multibeam bathymetry and chirp sub-bottom profiles of the Lucia Chica channel system on the seafloor offshore central California, and (2) the well-exposed channelized strata of the Tres Pasos Formation in southern Chile. The Lucia Chica channel system shows laterally offset, sub-parallel channels that evolved across a similar gradient, but display different architecture, reflecting the influence of channel maturity and intrinsic cyclicity of channel formation. The stratigraphically oldest channel is narrower with well-developed levees while the younger channelized features are broader and bounded by low-relief levees or no levees at all.The high-resolution Lucia Chica dataset is integrated with detailed field observations of channel axis-to-margin sedimentary facies relationships and the stratigraphic context afforded from depositional-dip continuity in outcrops of the Tres Pasos Formation. Numerous channels from the outcrop belt are characterized by initial erosional stages.By combining these two datasets with numerical analysis, experimental work, and previous interpretations of additional outcropping strata and seafloor examples, we hypothesize that an initial erosional template extending into a basin is a pre-requisite for creation of channels in deep-sea environments.