Chalk Bluffs

Location:   Weld County
Size:   640 acres
Designated:   September 2001
Landowner: State Land Board

This natural area is a small portion of an extensive area in northern Colorado where the barren outcrops of the Ogallala, Fox Hills and Arikaree Formations known as the Chalk Bluffs dominate the landscape.  The western site is on the Wyoming border north of Greeley and east of I-25. The eastern site is in northwestern Logan and northeastern Weld counties.  Lesser outcrops extend between the two sites and also form the northern bluffs of the S. Platte River valley in eastern Logan County. 

The cliffs are protected from fire by their barrenness, and thus support outlying populations of foothills plant species such as ponderosa pine, Rocky Mountain juniper, limber pine, and mountain mahogany.  These montane plants combine with prairie grasses to form communities unique to the escarpment. Clay lenses within the sandstone layers support a different type of barrens community, one dominated by hard cushion plants such as Stenotus acaulis, Phlox, Hymenoxys acaulis and the rare plants Cryptantha cana and Parthenium (Bolophyta) alpinum.  The rocks are rich in Miocene, Eocene and Paleocene vertebrate fossils, and the bluffs support a high concentration of nesting raptors.