as

Unconformably overlying the Mesozoic (?) acid intrusives is a
group of Mesozoic (?) andesitic flows and fragmental rocks.
Rhyolitic dykes and stocks were injected at a late stago in this
period of vulcanism, The Tertiary rocks in the areca are nearly
horizontal, amygdaloidal, and vosicular lava flows, Related to
these lava flows are andesitic and basaltic dykes. Several
isolated patches of conglomcrate unconformably overlic the
Tertiary lavas. Much of the arca has beon glaciated, resulting
in a mantle of glacial material in the lower parts, and a
rearrangement of the drainage.