The concept of tectonic provenance: Case study of the gigantic Markagunt gravity slide basal layer

Formation and evolution of the basal layer in large landslides has important implications for processes that reduce frictional resistance to sliding. In this report, we show that zircon geochronology and tectonic provenance can be used to investigate the basal layer of the gigantic-scale Markagunt gravity slide of Utah, USA. Basal layer and clastic injectite samples have unique tectonic chronofacies that identify the rock units that were broken down during emplacement. Our results show that basal material from sites on the former land surface is statistically indistinguishable and formed primarily by the breakdown of upper plate lithologies during sliding. Decapitated injectites have a different tectonic chronofacies than the local basal layer, with more abundant lower plate-derived zircons. This suggests clastic dikes formed earlier in the translation history from a structurally deeper portion of the slide surface and a compositionally different basal layer before being translated to their current position.

Automated summary

The formation and evolution of the basal layer in large landslides has important implications for reducing frictional resistance to sliding. This study investigates the basal layer of the Markagunt gravity slide in Utah, USA, using zircon geochronology and tectonic provenance. The results show that the basal material primarily comes from the breakdown of upper plate lithologies during sliding, and decapitated injectites have a different composition and come from a structurally deeper portion of the slide surface.