Basal breccia and clastic dikes at Haycock Mountain, near the southern terminus of the Markagunt gravity slide, Utah

Basal breccia and clastic dikes at Haycock Mountain, near the southern terminus of the Markagunt gravity slide. 

The 23-Ma basal breccia is a poorly sorted mixture of rock and sediment that behaved as an overpressured fluid at the base of the slide, 

facilitating slide movement. Kinematic indicators on the planar basal slip surface demonstrate emplacement from the north. 

Tm(Ti) = cataclastically deformed 27-Ma Isom Formation; Tbh = 34-Ma Brian Head Formation