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WSU/Pend Oreille Extension introduced the Sense of Place series in 1999, with a focus on place-based stewardship education. Since 2001, a partnership with the Kalispel Tribe of Indians Natural Resources Department (KNRD) has supported this newsletter and allowed us to expand class offerings through EPA funding. Further staff support comes through Renewable Resources Extension Act (RREA). Many thanks to our partners and to you, our readers, for your continued enthusiasm for "digging" into the natural history and culture of this part of the world.

Eroding Turbidites and Riverine Puzzles


by Sandie Durand • Cascara Consulting

Depending on the project site and scope, my native plant restoration work has varying degrees of complexity, but one constant ingredient is that every site will be bordered by scenic beauty and the natural wonders of Pend Oreille. A glance in any direction presents enticing possibilities for observation and discovery, and that imparts an appealing sense of adventure each morning when I head out the door for work. On a cool, drizzly day…I sometimes need that added incentive to close the door behind me…

During a September shoreline project, I found myself planting native willow adjacent to an ancient, eroding “turbidite” formation, with curiously shaped clay stones emerging along its face and a tenacious aspen sapling defying the odds. What a fascinating discovery! Over time, weathering and river action have released a consid- erable number of clay stones known as “concre- tions” from the graded bedding, scattering them directly beneath the geological formation and across the shoreline. Many of us may find these odd stones and puzzle over them as we explore stretches of the river and yet, rarely do we have the opportunity to determine their place of origin. Different locations on the river seem to offer distinctly different shapes, which also contributes to the mystique surrounding these stones.

Turbidite formations and concretions are found worldwide and some display a striking resem- blance to the ones we see here in Pend Oreille. (I have included a few Web links at the end of the article for you to explore some snowy win- ter evening.) Not being a geologist or a fluvial geomorphologist, I’m more familiar with roots than rocks…but there are connections between the two. Geological formations can sometimes provide clues to a region’s botanical past in the form of fossils. Concretions form around a cen- tral nucleus, such as a grain of sand or organic material from leaves, roots, insects, bone, etc., but not all concretions contain fossils. Let’s have a look at some definitions to help fill in a few puzzle pieces.

Turbidite geological formations have their origins in turbidity current deposits from a form of underwater avalanche that are responsible for distributing vast amounts of sediment. Wikipedia (see online link below)

A turbidity current or density current is a current of rapidly moving, sediment-laden water moving down a slope through air, water, or another fluid. The current moves because it has a higher density and turbidity than the fluid through which it flows. Wikipedia (see online link below)

A concretion is a volume of sedimentary rock in which a mineral cement fills the porosity (i.e. the spaces between the sediment grains). Concretions are often ovoid (egg shaped) or spherical (round) in shape, although irregular shapes also occur. The word 'concretion' is derived from the Latin con meaning 'together' and crescere meaning 'to grow'. Concretions form within layers of sedimentary strata that have already been deposited. They usually form early in the burial history of the sediment, before the rest of the sediment is hardened into rock. This concretionary cement often makes the concretion harder and more resistant to weathering than the host stratum. Wikipedia (see online link below)

Clay stone concretions are known by many names around the world. For example, they are called “Imatra Stones” in Finland, “Fairy Stones” in Scotland, Ireland and Quebec, and “Mud-babies” or “Clay Dogs” in Connecticut. Locally, we call them “Clay Rocks.” The stones have been carried as charms and a collection of these “Charmstones” was donated to The National Museum of Scotland by Dr. John Alexander Smith in 1857; believed to have been collected during the 17th or 18th century from Fairy Dean, near Melrose, Roxburghshire, Scotland.

Books on turbidites and concretions can be found ranging from highly technical publications to charming, yet knowl- edgeable selections, like the following by J. M. Arms Sheldon, whose clay stone collections from the Connecticut River area included animal forms. A number of her clay stone descriptions within the 110 year old text parallel ours of the Pend Oreille and I encourage you to seek out a copy of the complete text online for a fun read. I believe each of us who have come across one or more of these enchanting stones can relate to her words below.

“Since my childhood the so-called “clay stones” of our valley have excited, first, my curiosity, and in later days my deep interest. It has been, therefore, a keen delight to picture in lasting form some of the many rare specimens I have unearthed, and to record the observations made during happy days upon the green banks and the blue waters of the dear old Connecticut.” (Sheldon, J. M. Arms. “Concretions from the Champlain Clays of the Connecticut Valley” Montreal Society of Natural History. Boston: 1900. Original text is in the Cornell University Library.)

Over the next few years as I monitor and photograph progress of the 200 mixed native willow plugs that were planted along the turbidite formation’s shoreline, I will also record changes in the formation itself for my own curiosity. The young aspen clone, whose roots found their way downslope through the formation cracks to sunlight and growth, will be of particular interest to me in the coming years. The natural dynamics of deer and beaver browse, river action and root inhibiting dense clay will all challenge this spunky little sprout…but so far…it seems to know more about its hopeful future than do I…

I ask a favor in closing…should you find locations where these stones lie scattered upon the shoreline and feel the magnetic urge to collect, please do so sparingly and remember…they contribute to our beautiful river’s wildscape and to the unexpected delight of any who may follow in your footsteps and puzzle over them.

“The cure for boredom is curiosity. There is no cure for curiosity.” Dorothy Parker

Online Information:
http://en.wikipedia.org/wiki/Concretion
http://en.wikipedia.org/wiki/turbidite
http://earthquake.usgs.gov/learn/glossary/?term=turbidites

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