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Did you know that geologists have recently discovered a reasonable source for the volcanic ash of the John Day formation?
You can learn about this and other recent discoveries in Oregon's geologic and fossil record at the HMSC's annual Fossil Fest.
At 1:30pm, Elizabeth and William Orr will not only be on hand to sign the second edition of their book Oregon Fossils, but will review what's new in the world of geology and paleontology and how these new discoveries relate to and impact fossils. Bring in your own fossil finds and learn more about them from the experts!
"Fossils You Can Find on Oregon Beaches"
Oregon's sandy beaches are known for their shells, sand dollars, agates, and jaspers, as well as for a wide variety of Miocene-era marine and mammal-bone fossils.
Geologically speaking, Oregon coast fossils are found in three formations: the Astoria Formation, 15- to 20-million-year-old sandstone layers mixed with compressed volcanic ash; Nye mudstone, up to 20 million years old; and on south coast stretches of beach, Coledo Formation specimens of dark ash and sand, which are 25–30 million years old. These formations of compacted sand, volcanic ash, and river-borne silt are uplifted from the Pacific Ocean floor by geo-plate movement.
Layers of rock and sediment exposed above sandy beaches between basaltic headlands form the larger, more permanent hills along the Oregon coast. The combination of eroding basalt, mud, and sandstone produces a combination of rocks and fossils mixing on the beaches with sand. There are dozens of species of fossilized marine life, ranging from microscopic algae to the hand-size Panopea abrupta and the dinner plate-size Patinopectins and smaller Vertipectins.
A note about seawalls: While Oregon's beaches are public, the seawalls above them where people's homes and public highways are located generally are not. Do not use tools to remove anything from a seawall--this is a violation of Oregon law.
While clams are the larger and more populous of Oregon's Miocene marine fossils, gastropods (for example, snails) are frequently found, especially in concretions. For some, the attraction of gastropods results from the artistic 180° twist the shell makes during its growth, called torsion. Most gastropods--herbivores and carnivores--use an armored tongue, or "radula," as a tool to drill through shells into their meals. Common Miocene gastropods making Oregon's coast their home include...
Wood and Bone Fossils
In addition to abundant marine fossils, Oregon's coast offers a wide variety of petrified woods. As ocean currents moved along the shoreline and rivers ran into the Pacific Ocean, wood species from other regions were deposited on Oregon's beaches.
Teredo wood appears as brown to black rocks, usually rounded at the ends with a "Swiss cheese" look to them. Fossilized casings from the Teredo marine clam created the pattern when the Teredo, in its larval form, ate its way through chunks of ancient wood. These colonies of small larvae never cross each other's borings, making each piece unique in design and appearance. Other petrified woods are light tan to carbonized black, frequently found in sizes ranging from one inch to two feet across. Look for a dull sheen on wet rocks with parallel wood grain patterns. Softwood species of pines and some hardwoods, including alder, myrtlewood, and oak, as well as petrified palm, are also found on Oregon beaches.
An occasional fossilized leaf impression can be found on or in coastal rocks, recognizable as elm, alder, and Oregon Grape--Mahonia repens.
Petrified wood pieces are also often found in concretions of rounded mudstone or hard gray volcanic ashballs. Sometimes split in half by nature, inside these concretions is often carbonized or fossilized wood that was once carried downstream from the Cascade Mountains. Crabs are one type of arthropod found inside concretions when split open--claws, legs, and occasionally whole crabs.
Another genre of fossil found on Oregon's coast is mammal bone. Usually deposited in hardened sandstone, bone is as abundant as Teredo wood and Anadara shells. Look for light brown or gray rocks with rounded edges and a darker edge or center, which is usually bone.
Most fossils can be found at low tide on sandy beaches, in creek washes, and below the rockier headlands in high-tide rock piles. Fossils found on public beaches may be taken, but they may not be commercially sold without a permit. You cannot legally collect or take fossils from marked "marine gardens" or beaches adjacent to Oregon State, U.S. Forest Service, or BLM parks, campgrounds, and natural areas.
You can find a link to the publication, "Fossils You Can Find on Oregon Beaches" at the Hatfield Link below.
Oregon State University's Hatfield Marine Science Center (in Newport) and the Oregon Museum of Science and Industry (in Portland) are two locations where you'll find exhibits of fossils discovered on Oregon's beaches.