Geologic Trip, Rogue Valley

Barneburg Hill

Barneburg Hill (1680’) is a prominent hill in south-central Rogue Valley that rises nearly 300 feet above the valley floor. From the top of the hill there are spectacular views of the Rogue Valley and the nearby Klamath and Cascade mountains. Buildings and houses of the Rogue Valley Manor cover much of the hill.  

 

As shown in the adjacent map and cross section, this part of Rogue Valley is formed from marine sedimentary rocks of the Cretaceous Hornbrook Formation. Most of these rocks are mudstone and siltstone that is easily eroded. These soft rocks form the lower parts of Bear Creek Valley. Sandstones and conglomerates also occur parts of the Hornbrook Formation. Barneburg Hill is formed from some especially thick sandstones and conglomerates that are very hard and have resisted erosion.

 

All of the sedimentary rocks in Bear Creek Valley dip gently to the east. Due to the eastward tilt, the hard sandstone lies along the west side and crest of the hill, the conglomerate occurs on the upper slope of the east side, and the mudstones and siltstones occur in the lower areas. 

 

Most of Barneburg Hill is covered by buildings, houses, streets,  parking lots, gardens and lawns, so there are few places to see the rocks. However, you can see the rocks if you know where to look and what to look for. During construction of the Terrace building several large blocks of sandstone from the crest of the hill were excavated and these blocks can now be seen along the paths west of the Health Center. These large blocks of sandstone are extremely hard and most have layers of pebbles. Thick sandstone beds are also exposed at the end of Quail Point Court where the sandstone forms a scenic waterfall.

 

It is difficult to find good exposures of the conglomerate on Barneburg Hill since the matrix of the conglomerate weathers rapidly and the conglomerate falls apart. However, the cobbles in the conglomerate are hard and remain behind, showing the general location of the conglomerate beds. Look for the cobbles in the garden areas from the RV storage area northward along Horizon Lane to the Rose Garden below the Manor. The cobbles are typically round, about the size of an orange, and consist of a mixture of various metamorphic and igneous rocks along with some vein quartz. These cobbles were likely derived by erosion of the early Klamath Mountains roughly 100 million years ago.

 

The mudstones and siltstones occur on the lower part of Barneburg Hill below Village Center Drive. It is difficult to see these rocks since they crumble easily and rapidly turn to mud when wet. The best place to see the mudstone and siltstone is where the rocks have been excavated during building projects. The photo shows mudstone and siltstone exposed during excavation for the Lake Village project.

 

Barneburg Hill is the largest of several hills between Medford and Talent that have been formed from sandstone and conglomerate of the Hornbrook Formation. Interstate 5 cuts into Barneburg Hill and many of the other hills providing good exposures of these rocks in the road cuts along the highway.

 

External Website

ODGM:  Geologic Map, Bear Creek Valley

 

 

Return to: Rogue Valley

The path west of the Health Center winds between several large blocks of hard sandstone that were excavated from the top of Barneburg Hill during construction of the Terrace. Most of these sandstones have layers of pebbles included within the sandstone.  

The thick hard sandstone of Barneburg Hill forms a scenic The waterfall on Quail Point Court is formed from sandstone beds of Barneburg Hill.

Note the round cobbles near the drain along this path in the garden below the Manor building. The cobbles were derived from a conglomerate bed that occurs in this  area along the upper slope of the east side of Barneburg Hill.

 

Closer look at the cobbles from the conglomerate: the pebbles are formed from many different types of metamorphic and igneous rocks that were eroded from the Klamath Mountains about 100 million years ago. 

Thin beds of mudstone and siltstone of the Hornbrook Formation that were exposed during construction of the Lake Village. These rocks crumble and turn into mud when wet. Most of the floor of Bear Creek Valley is formed from these soft rocks. For scale, the stake is about one foot high.