ECOS Guide to the Ecology of the Northern Rockies

                 
 

Mesozoic Era Exposures

(210-65 million years) Predominantly sedimentary deposits in the northeast section of the map, and igneous/metamorphic rocks in the southern section of the map.  The Idaho Batholith and the Boulder Batholith are Mesozoic igneous intrusions.  This is the age of dinosaurs.  Dinosaur fossils have been discovered in Montana at such locations as Egg Mountain near Choteau.  A meteorite impact occurred at 65 million years ago, causing a great mass extinction.

Idaho Batholith – Outcrops of 70-100 million year old igneous intrusion.  A large body of magma intruded into the crust during the formation of the northern Rockies, and is now exposed to the southwest of Missoula and in eastern Idaho. 

Boulder Batholith – Outcrops of ~75 million year old igneous intrusion.  A large body of magma intruded into the crust during the formation of the northern Rockies, and is now exposed between Butte and Helena.  The Boulder Batholith contributed to the rich mining resources in western MT.

 


 

The ECOS program is sponsored by the University of Montana's Division of Biological Sciences, and the College of Forestry and Conservation. Carol Brewer Program Director, Division of Biological Sciences. Paul Alaback Program Co-Director, College of Forestry and Conservation.
NSF LogoECOS is supported by the GK-12 Program of the National Science Foundation.
Any opinions, findings, and conclusions or recommendations expressed in this publication are those of the authors and do not necessarily reflect the views of the National Science Foundation.