Fossils are of interest to most everyone, even to those of us slowly becoming fossils.
The easiest place to see fossils in Southern Oregon is in the cliffs along Interstate 5 behind a long line of cement barriers north of the Siskiyou Summit. If you are curious enough to go looking, park safely off the road and walk back about 100 feet behind the barriers. And please don't collect fossils; leave them for others to observe and study.
Some fossils can be seen in fallen rocks, although if you look carefully at the steep cliffs you'll see thin whitish bands in the Hornbrook Formation's greenish sandstone. These thin channels with fossil-rich sands were carved into underlying sandstone during ancient ocean storms. Fossils lie at the base of those channels.
These fossils belong to a "thanotoceonosis," or death assemblage, named after Thanatos, the Greek god of death. Indeed, these once "happy as a clam" organisms were rudely torn from the beach during huge storms, washed out to sea and deposited.
Most fossils fracture when the rock breaks, showing only profiles unless the rock breaks around the shells to reveal familiar clam shapes. You'll find off-white to light brown, spiky-looking fossil clam shells of Pterotrigonia Klamathensis and Calva regina Popenoe that look like today's "butter clam."
However, 90-million-year-old clams aren't good to eat, no matter how long they're steamed. There are coiled snails (16 species), scaphopods (shaped like tiny horns of plenty), rare shark teeth and, if you're lucky, a sea urchin, oyster, starfish or coral.
Some of the pale green sandstone weathers to a brownish cast. In such rock, material forming the fossil is gone, leaving only a mold of the fossil. In some sandstone, Callianasid shrimp ("ghost shrimp") hunkered down in their burrows are preserved. However, it's likely all you'll find are their large claws, similar to an index finger raised in the "We're No. 1" fist seen at modern sporting events.
Rare ammonites (like bumpy, coiled nautiloids), flattened during burial into small "paleo-Frisbee" shapes, are found in gray shale.
The most abundant fossils are microfossils, studied by micropaleontologists (I'll skip the obvious joke about tiny scientists), which formed the base of the oceanic food chain. These easily overlooked fossils are found most commonly in gray shale or mudstone. They're the size of a fat pinhead (the fossils, not the micropaleontologists). Using a magnifier you might see them as roundish gray spots showing subtle ribbing. Don't be discouraged if you can't find any: most dissolve under pressure and truly take a trained eye to find.
Mea culpa: In my last column, I should have wrote that the contact between the Western and High Cascades near Lost Creek Reservoir is found along Highway 62, not 140. Even professors make misteaks.
Jad D'Allura is emeritus professor of the former Southern Oregon University Geology Department. Reach him at firstname.lastname@example.org.