Geology

The T/WAB region has three types of geological units (quoted from USGS):

TKda: Denver and Arapahoe Fms (Phanerozoic | Mesozoic Cenozoic | Cretaceous Tertiary) -- Sandstone, mudstone, claystone, and conglomerate; Denver is characterized by andesitic materials
Qa : Modern alluvium (Phanerozoic | Cenozoic | Quaternary) -- Includes Piney Creek Alluvium and younger deposits
Qg : Gravels and alluviums (Phanerozoic | Cenozoic | Quaternary) -- Includes Broadway and Louviers Alluviums