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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.

A Paddler's Geology of the Pend Oreille river

By Carol Mack

The geology of the Pend Oreille River is fascinating, but complicated by a history that includes a variety of driving forces. The understanding of many of these forces such as plate tectonics or ice age floods has come about relatively recently, and is still evolving.

Approximately 1,500 million years ago (abbreviated as 1,500 Ma) much of our area was under water, and a distinctive group of sedimentary rocks formed, called the Belt Supergroup. These rocks can still be found in areas from Newport to Riverbend. Then about 750 Ma, what was the continent at that time split up, and northern Pend Oreille County became ocean-front property. Wind, gravity and rivers eroded existing rock formations and carried sand out to sea forming a continental shelf through what is now the northwest corner of the county. These sands eventually compressed into quartzite formations. As time went on (550-250 Ma), ocean life blossomed and sea creatures deposited skeletons and shells that were transformed into a layer of limestone over the quartzite.

Then tectonic plate action dating back to around 150 Ma started building the Rocky Mountains. Large areas of granitic rocks were formed from the mid Pend Oreille River east through Priest Lake as tectonic forces caused crustal melting. Hot chemically-rich fluids from the granitic magma shot through the surrounding rocks and mineralization set up conditions that would later make the Metaline Mining District one of the richest in the state. From 58 to 46 Ma crustal stretching caused local mountain uplifts and faults (including the Newport Fault) that formed the basic geography of today’s Priest River, Pend Oreille and Colville valleys. At this point, the Pend Oreille River most likely flowed to the south, as evidenced by the south-trending angles of tributary streams.

Around 2 Ma, radical climate variations produced a dozen or more episodes of glaciations. The last glacial period covered an area extending south to Newport with ice sheets so thick that only the highest mountain peaks like Abercrombie and Gypsy were visible.

From 12,000 to 9,000 years ago, a special topographical arrangement in northern Idaho permitted ice to repeatedly impound a huge lake called Glacial Lake Missoula. The ice dam failed repeatedly, each time sending hundreds of cubic miles of water across parts of Washington in catastrophic floods, forming the channeled scablands. When the Newport lobe of ice was at its maximum, these floods were directed towards Coeur d’Alene through the Rathdrum Prairie, but as climate warmed and the lobe retreated, floodwaters came down the Pend Oreille valley and southward through the Davis Lake spillway and the Little Spokane River valley with a complex mix of routes. For a while, the entire Pend Oreille River flowed through Scotia Canyon.

As the glacier thinned and retreated further, Glacial Lake Clark formed in the Pend Oreille River valley. Deep layers of fine sediments were deposited in these waters. The mile-high ice to the north was heavy enough to depress the earth’s crust and one theory is that this is what caused the ice age lake to start draining toward Canada. As the ice disappeared and the crust rebounded, the water eventually cut Z Canyon through the bedrock north of Metaline Falls and continued flowing northward across its former headwaters, resulting in a complete river drainage reversal. Smaller post-ice age lakes and seasonal floods have deposited more recent sediments, and as the river shifts position these are being repeatedly rearranged. The shorelines of the lower and middle water trail reaches are largely composed of these sediments.

POINTS OF INTEREST HEADING DOWNRIVER:

Kame Terrace

From RM85 (near Newport) to the north, a gently sloping deposit of sand and gravel outwash is visible above LeClerc Road on river right. It formed between the retreating glacier and the valley wall, sloping southward to Newport. Termed a kame terrace, this deposit blocked numerous side valleys and created a series of lakes including Bead, Marshall, Shearer and Freeman.

Barbed Tributaries

Streams that bend their paths in a opposite direction before entering the river are called barbed tributaries and are characteristic of rivers that have experienced drainage reversal. Examples include Skookum Creek (RM 73.5 Right) and Cee Cee Ah Creek (RM 66.5 Right)

Newport Fault and Tiger Formation rocks

About 50Ma, tectonic movements stretched the local area and a large horseshoe-shaped fault developed, with rock inside the horseshoe area dropping relative to the rocks outside. Newport lies at the southern end of the fault with one arm extending up the Pend Oreille River to Metaline and the other into northern Idaho. Gravity works, and this newly-formed valley was quickly filled with fans of coarse gravel eroded from the mountains. These formed a conglomerate, the Tiger Formation, which varies slightly from site to site. These rocks can be viewed on roadcuts along Hwy 31 including an area north of the entrance to Box Canyon Dam and along LeClerc Road, including large rocks at Manressa Grotto picnic area.

The "Terror of the River"

The viewpoint on Hwy 31 above Box Canyon Dam provides an overlook of the rocks and rapids that stopped David Thompson in his canoe exploration in 1809, and steamboat traffic in following decades until some critical rocks were dynamited to make travel to Metaline Falls possible. Boating is prohibited in the river immediately south of Box Canyon Dam for safety reasons, and the nearest public access point is Edgewater Campground, two miles to the south at RM37 Right.

Metaline Falls

The falls near RM 27 have been partially tamed by the construction of Boundary Dam, but the whirlpools and rocks are still a major hazard to boaters, especially during afternoons and evenings when the reservoir pool level is lowered as electricity is generated at peak demand times. Experienced paddlers may be able to navigate them without incident early in the morning, but be sure to check conditions from the Metaline Falls Bridge before venturing out. A portage trail around the hazard has been proposed as a future Boundary Dam relicensing project, but it may be safer to put in at the north end of the reservoir for now.

Sullivan Creek Mouth

RM 27 Right. In 1859, placer gold was discovered at the mouth of Sullivan Creek, which was named after prospector Michael R.O. Sullivan. The town that instantly appeared was flooded in 1894 and rebuilt on higher ground. The cement plant was built in 1911, with limestone rock delivered by an aerial tram.

Flume Creek

RM 26 Left. This area and others nearby were worked heavily by Chinese miners in 1870 and following years. They also reworked spoil piles of previous miners to extract more gold.

Pend Oreille Mine

RM 25 Tailings, drainpipes, and other workings associated with mining are visible on river right. The limestone/dolomite geology led to rich deposits of minerals, and many mines were prospected along the northern river reach. The Pend Oreille Mine, with tunnels extending under the river in this vicinity, is the largest and most recently operating. Ores containing the minerals sphalerite and galena were processed for zinc and lead. (see www.diggings.org/pomine.html)

Z Canyon

Between Metaline Falls and Boundary Dam, the river cuts through Metaline Limestone and the overlying Ledbetter Slate, with pockets of glacial sediments between rock outcrops. The limestone is approximately 1,500 feet thick and forms vertical cliffs up to 500 feet high. Z Canyon, at RM22, was famous for its narrow zig-zag where the river “turned on its side”. Although reservoir waters are now higher and wider, historical descriptions reported a 50 foot wide chasm, and there are stories of crossing from one side to the other on fallen logs.



References:

Barreca, Joseph, 2010, Geologic Atlas of Pend Oreille County Washington, Map Metrics, Kettle Falls WA www.mapmet. com

Doughty, Ted, Kiver, E,; and Stradling,D., 2002, Significant Dates and Events Affecting Pend Oreille County (compiled for 2002 North Pend Oreille County Geology field trip) www.diggings.org/dates.html accessed 6/22/2012

Kiver, Eugene; Bjornstad, B.; and Nisbet,J., 2012, Missoula Floods, Glaciers, Early People and Explorers in Northeast Washington, Ice Age Floods Institute Cheney-Spokane Chapter www.iceagfloodsewa.org


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