The thesis area consists of 42 square miles located
in Madison and Gallatin counties, Montana, in the southern
part of the Madison Range. The strata exposed in the
area range in age from Precambrian to Quaternary and have
an aggregate thickness of more than 7,600 feet.
The Paleozoic rocks, about 3,900 feet thick, are
mainly carbonates but include sandstones, shales, and
cherts of marine origin. Ordovician and Silurian formations
The Mesozoic rocks consist mainly of sandstones,
shales, calcareous claystones, and argillaceous limestones
of marine and continental origin. All Mesozoic periods
are represented in this 3700 foot thick sequence of
The Cenozoic rocks and sediments include welded tuff,
glacial deposits, and alluvium. Quaternary landslides
cover about one-quarter of the thesis area.
The structures are Late Cretaceous to Early Tertiary
(Laramide) and Late Cenozoic in age. The Laramide structures
are northwest- trending, asymmetrical (steeper to
the northeast) folds and high angle reverse faults. The
Late Cenozoic structures are normal faults that displace
Upper Cretaceous strata.