The geologic map of the Hog Cove Butte quadrangle depicts tilted lavas of the Miocene Columbia River Basalt Group and younger mixed volcanic flows and tuffs. These units trend to the north-northwest and dip to the west-southwest. Deposition of river sediments and sedimentary rocks of the lower to middle Miocene Payette Formation occurred contemporaneous with, and subsequent to regional volcanism. Following a break in time, the upper Miocene to Pliocene Idaho Group (Chalk Hills and Glenns Ferry formations) were deposited in a lake and fluvial environment (Lake Idaho). Most of the sediments are younger than the last of the volcanic flows. Dipping beds and repeated sections indicate that subsidence and fault activity continued through the Miocene and into the Pliocene. Folding of sedimentary strata is along axes that trend north to northwest and is likely of similar age. Subsidence, folding, and faulting provides a view of sandy deposits that to the west are buried and host petroleum deposits. An unsuccessful oil and gas well drilled in the quadrangle in 2010 provides a 3-D look at the subsurface geology.
Quaternary alluvial deposits include active stream deposits, terrace deposits along the larger streams, and highly dissected older alluvial fans and alluvium deposits. Landslide deposits are resulting from the failure of competent basalt over unconsolidated sediments, or the failure of loosely consolidated Glenns Ferry Formation near the contact with the underlying Chalk Hills Formation.
The map was funded by the USGS STATEMAP program and state appropriations.