Using Landscape Evolution Modeling to Evaluate Potential for Buried Mega-Landslide Reservoir Units Within the Basin and Range, Western U.S.A.

Abstract

Mega-landslides reside on the surface and in the subsurface throughout the Basin and Range province of the western USA. Buried mega-landslide blocks locally are excellent hydrocarbon reservoirs, accounting for approximately half of the produced hydrocarbons in Nevada. These basins are bounded on one or both sides by Miocene to recent normal and/or strike-slip faults. Basins within the province are filled with several km of poorly consolidated and unconsolidated clastic material shed from the ranges, lacustrine sediments, and volcanic ash and flows, making seismic imaging in this region very difficult and expensive. Therefore, the purpose of this study is to use clues in rangefront morphology to help identify mega-landslides in the subsurface.

We used the LandLab software to develop numerical landscape models of a developing horst range affected by mega-landslides. LandLab is a Python-based open source landscape evolution modeling software that is designed to quantify surface processes and evolution of landscapes through time. Idealized modeling exercises were run to evaluate the scope of potential rangefront morphologies resulting from mega-landslide processes. The baseline modeling exercise used a deep-seated dip-slope landslide process to simulate the evolution of a range during regional extension. From these baseline results, landslides were imposed according to a size-frequency distribution and conditioned for the range of local lithologies and structures within the Basin and Range. Model stratigraphy was tracked to evaluate how different distributions of landslide sizes impact the alluvial architecture with a range of fault slip rates and climatic parameters.

This idealized landscape modeling has provided information on (i) the general evolution of rangefront stratigraphy as it relates to landsliding and landslide deposits; (ii) estimating the time scale for relaxation of landslide source areas following an event, and what lingering impacts on the fluvial network may remain to be extracted from the topography; and (iii) disruptions to the pattern of alluviation on the fans and other basin fill by emplacement of a mega-landslide. These results will be compared to exposed mega-landslides throughout the province. Key geomorphic features from these models will be used to guide analysis of rangefronts for potential buried mega-landslide reservoirs in the Basin and Range.

AAPG Datapages/Search and Discovery Article #90350 © 2019 AAPG Annual Convention and Exhibition, San Antonio, Texas, May 19-22, 2019