Research paperModeling uncertainty in the three-dimensional structural deformation and stratigraphic evolution from outcrop data: Implications for submarine channel knickpoint recognition

- Quantifying impact of structural uncertainty on stratigraphic outcrop interpretation.
- Restoring structural deformation from channel geometry shows channel downcutting.
- Uncertainty analyses validates incision of youngest submarine channels into older ones.
- Submarine channel thalweg gradient (64-125  m/km) is consistent with an out-of-grade system.
- Steep segments (100-175 m/km) suggest the presence of tectonically-induced knickpoints.

Digital outcrop models help to constrain the interactions of stratigraphic and structural heterogeneity on ancient depositional systems. This study uses a stochastic approach that incorporates stratigraphic and structural modeling to interrogate the three-dimensional morphology of deep-water channel strata outcropping on Sierra del Toro in the Magallanes Basin of Chile. This approach considers the relative contributions, and associated uncertainty, of erosional downcutting versus post-depositional structural folding and small-offset faulting on the present-day configuration of the submarine channel complexes. Paleodepositional channel-belt gradients were modeled using a combination of three-dimensional visualization, stochastic surface modeling, palinspastic restoration, and decompaction modeling that are bound with errors constrained by stratigraphic and structural uncertainty. Modeling results indicate that at least 100 m of downcutting occurs over 6 km, and the resultant thalweg gradient of 64-125 m/km (decompacted) suggests that the Cerro Toro axial channel belt is an out-of-grade depositional system. Furthermore, the presence of steeper segments (100-175 m/km decompacted) suggests the preservation of one or more knickpoints that are similar in magnitude to tectonically-induced knickpoints on the modern seafloor. The interpreted knickpoints are correlated with a decreasing channel width-depth ratio and an increase of channel depth. These results indicate that stochastic surface modeling using digital outcrop models can constrain stratigraphic interpretations and post-depositional structural heterogeneity.