CHUCKANUT DRIVE: EOCENE TROPICAL PARADISE

A trip along Chuckanut Drive, in northwestern Washington is a chance to view incredible diversity from sea to sky.

An amazing array of plants and animals call this coastline home. 

For the fossil enthusiast, it is a chance to slip back in time and have a bird’s eye view of a tropical paradise preserved in the Eocene strata of various fossil sites. 

Snug up against the Pacific Ocean, this 6000m thick exposure yields a vast number of tropical and flowering plants that you might see in Mexico today. Easily accessible by car, this rich natural playground makes for an enjoyable daytrip just one hour south of the US Border.

Over vast expanses of time, powerful tectonic forces have massaged the western edge of the continent, smashing together a seemingly endless number of islands to produce what we now know as North America and the Pacific Northwest. Intuition tells us that the earth’s crust is a permanent, fixed outer shell – terra firma.

Aside from the rare event of an earthquake or the eruption of Mount St. Helen’s, our world seems unchanging, the landscape constant. In fact, it has been on the move for billions of years and continues to shift each day. As the earth’s core began cooling, some 4.5 billion years ago, plates, small bits of continental crust, have become larger and smaller as they are swept up in or swept under their neighboring plates. 

Large chunks of the ocean floor have been uplifted, shifted and now find themselves thousands of miles in the air, part of mountain chains far from the ocean today or carved by glacial ice into valleys and basins.

Two hundred million years ago, Washington was two large islands, bits of continent on the move westward, eventually bumping up against the North American continent and calling it home. Even with their new fixed address, the shifting continues; the more extreme movement has subsided laterally and continues vertically. 

The upthrusting of plates continues to move our mountain ranges skyward – the path of least resistance. This dynamic movement has created the landscape we see today and helped form the fossil record that tells much of Washington’s relatively recent history – the past 50 million years.

Chuckanut Drive is much younger than other parts of Washington. The fossils found there lived and died some 40-55 million years ago, very close to where they are now, but in a much warmer, swampy setting. The exposures of the Chuckanut Formation were once part of a vast river delta; imagine, if you will, the bayou country of the Lower Mississippi. The siltstones, sandstones, mudstones and conglomerates of the Chuckanut Formation were laid down about 40-54 million years ago during the Eocene epoch, a time of luxuriant plant growth in the subtropical flood plain that covered much of the Pacific Northwest.

This ancient wetland provided ideal conditions to preserve the many trees, shrubs & plants that thrived here. Plants are important in the fossil record because they are more abundant and can give us a lot of information about climate, temperature, the water cycle and humidity of the region. 

The Chuckanut flora is made up predominantly of plants whose modern relatives live in tropical areas such as Mexico and Central America. If you are interesting in viewing a tropical paradise in your own backyard, look no further than the Chuckanut. 

Images and tag lines: Glyptostrobus, the Chinese swamp cypress, is perhaps the most common plant found here. Also abundant are fossilized remains of the North American bald cypress, Taxodium; Metasequoia (dawn redwood), Lygodium (climbing fern), large Sabal (palm) and leaves from a variety of broad leaf angiosperm plants such as (witch hazel), Laurus (laurel), Ficus (fig) and Platanus (sycamore), and several other forms.

While less abundant, evidence of the animals that called this ancient swamp home are also found here. Rare bird, reptile, and mammal tracks have been immortalized in the outcrops of the Chuckanut Formation. Tracks of a type of archaic mammal of the Orders Pantodonta or Dinocerata (blunt foot herbivores), footprints from a small shorebird, and tracks from an early equid or webbed bird track give evidence to the vertebrates that inhabited the swamps, lakes and river ways of the Pacific Northwest 50 million years ago.

The movement of these celebrity vertebrates was captured in the soft mud on the banks of a river, one of the only depositional environments favorable for track preservation.

FOSSIL FAUNA OF THE OLYMPIC PENINSULA

Vertipecten fucanus (Dall, 1898), Clallam Formation, WA

Some water-worn samples of the fossil bivalve Vertipecten fucanus from Lower Miocene deposits in the Clallam Formation.

These lovelies were collected on the foreshore near Clallam Bay, Olympic Peninsula, northwestern Washington on a lovely fossil field trip I did with my mother years ago.

Range zones of pectinid bivalves provide a principal means of age determination and correlation of shallow-water, inshore facies from California, through to Washington state and up to the head of the Gulf of Alaska.

Until Addicott's study from 1976, the area was considered middle Miocene. The new Lower Miocene designation can be credited in large part to the restricted stratigraphic range of Vertipecten fucanus (Dall, 1898) and the restricted and overlapping ranges of several other fossil mollusks collected from Alaska to California.

Neogene marine sediments of the West Coast of North America were deposited in a series of widely spaced basins that extended geographically from the western and northern Gulf of Alaska (60°N) to southern California (33°N). Rich molluscan faunas occur extensively throughout these deposits and form the basis for biostratigraphic schemes that are useful for correlating within and between individual basins.

Arturia angustata nautiloid, Clallam Formation, WA

Early biostratigraphic work was concerned with faunas from particular horizons and with the stratigraphic range of diverse taxa, such as Pecten and Turritella, without reference to other fossil groups.

Succeeding work increasingly dealt with the relationships of molluscan zones to benthic and, later, planktonic foraminiferal stages. In recent years the age limits of Neogene molluscan stages have become better documented by reference to planktonic microfossils from dated DSDP cores and onshore faunas. As our tools get better, our insight into these faunal groups and their correlation with their cousins to the south and over in the Pacific become clearer.

Neogene molluscan faunas from California, the Pacific Northwest states (Oregon and Washington), and southern Alaska have been treated separately due to differences in faunal composition and geographic isolation. As a result, a different biostratigraphic sequence has been described for each region.

Pacific Northwest stages have been formally named and defined. This naming structure is also used informally for Alaskan faunas. California Neogene stages were proposed early in this century, are in need of redescription, and their usage is informal. Precise correlations between the three regional sequences have not yet been achieved, due to the low number of co-occurring species and the general lack of planktonic microfossils in these largely shallow-water faunas. The objectives of ongoing research include the documentation of the faunas of California and Pacific Northwest stages; formal description of California stages; an improved correlation between regional stage sequences; refinement of age estimates for stage boundaries; and, the establishment of Neogene stages for Alaskan faunas.

BERLIN-ICHTHYOSAUR STATE PARK

At least 37 incomplete fossil specimens of the marine reptile have been found in hard limestone deposits of the Luning Formation, in far northwestern Nye County of Nevada. 

This formation dates to the late Carnian age of the late Triassic period when present-day Nevada and parts of the west were covered by an ancient ocean.

The first researcher to recognize the Nevada fossil specimens as ichthyosaurs was Siemon W. Muller of Stanford University. 

Muller had the work of Sir Richard Owen to build upon from Owen's 1840 publications. That being said, there are very few contenders for a species that boasts vertebrae over a foot wide and weighing in at almost 10 kg or 21 lbs. 

Muller contacted the University of California Museum of Paleontology at Berkeley. Surface collecting by locals continued at the site but no major excavation was planned.

Almost a quarter of a century after Muller's initial correspondence to the UCMP, Dr. Charles L. Camp received correspondence further detailing the finds from a lovely Mrs. Margaret Wheat of Fallon. She wrote to Camp in September of 1928 to say that she'd been giving the quarry section a bit of a sweep, as you do, and had uncovered a nice aligned section of vertebrae with her broom. The following year, Dr. Charles L. Camp went out to survey the finds and began working on the specimens, his first field season of many, in 1954.

Back in the 1950s, these large marine reptiles were rumoured to be "marine monsters," as the concept of an ichthyosaur was not well understood by the local townsfolk. Excitement soon hit West Union Canyon as the quarry began to reveal the sheer size of these mighty beasts. In the end, the ichthyosaur bones were left in situ to better understand how they were laid down over 200 million years ago.

Camp continued to work with Wheat at the site and brought on Sam Welles to help with excavations. The team understood the need for protection at the site. They canvassed the Nevada Legislature to establish the Ichthyosaur Paleontological State Monument. You can one of the Park Rangers above giving a tour within the lovely building they built on the site to protect the fossils.

In 1957, the site was incorporated into the State Park System and Berlin-Ichthyosaur State Park was born. The park Twenty years later, in 1977, the population of Nevada weighed in and the Legislature designated Shonisaurus popularis as the State Fossil of Nevada.

Know Before You Go — Berlin-Ichthyosaur State Park

This is a wonderful place to explore for a very reasonable sum of $5.00 US. Open year-round (though check regarding accessibility during Covid). They have accessible outcrops just outside the park boundary where you can collect ammonoid fossils. 

Contact information: Tel: 775-964-2440 / Email: bisp@parks.nv.gov. 

Address: State Route 844, Austin, NV 89310, United States. Area: 4.58 km². Elevation: 6,975 ft (2,126 m); Tel: +1 775-964-2440; http://parks.nv.gov/parks/berlin-ichthyosaur

SABRE-TOOTH SALMON

This toothy specimen is an Oncorhynchus nerka, a Pleistocene Sockeye Salmon from outcrops along the South Fork Skokomish River, Olympic Peninsula, Washington State, USA.

The area is home to the Skokomish — one of nine tribes of the Twana, Coast Salish First Nations in the northern-mid Puget Sound area of western Washington state in the United States. 

Each of the Tribal Nations are known by their locations — Dabop, Quilcene or salt-water people, Dosewallips, Duckabush, Hoodsport, Skokomish or Skoko'bsh, Vance Creek, Tahuya, and Duhlelap or Tule'lalap. The name Skokomish means river people or people of the river in the language of the Twana, sqʷuqʷóbəš or sqWuqWu'b3sH.

Closer to my home farther north in the Pacific Northwest on northern Vancouver Island are the Kwakiutl or Kwakwaka'wakw, speakers of Kwak'wala. Here, sockeye salmon are known as ma̱łik. You would likely recognize these fossils' modern counterparts from their distinctive red bodies and greenish heads. 

Their descendants had been absent from the Skokomish River for more than a decade up to 2014 when construction to augment the negative impact of the Cushman Reservoir was undertaken to restore their natural habitat.

The fossil specimens include individuals with enlarged breeding teeth and worn caudal fins. It is likely that these salmon acted very similar to their modern counterparts with males partaking in competitive and sneaky tactics to gain access to the sexiest (large and red) females who were ready to mate. These ancient salmon had migrated, dug their nests, spawned and defended their eggs prior to their death. For now, we're referring to the species found here as Oncorhynchus nerka, as they have many of the characteristics of sockeye salmon, but also several minor traits of the Pink Salmon, Oncorhynchus gorbuscha.

I had expected to learn that the locality contained a single or just a few partial specimens, but the fossils beds are abundant with large, 45–70 cm, four-year-old adult salmon concentrated in a beautiful sequence of death assemblages.

Oncorhynchus nerka, Pleistocene Sockeye Salmon

Gerald Smith, a retired University of Michigan professor was shown the specimens and recognized them as Pleistocene, a time when the northern part of North America was undergoing a series of glacial advances and retreats that carved their distinctive signature into the Pacific Northwest.

It looks as though this population diverged from the original species about one million years ago, possibly when the salmon were deposited at the head of a proglacial lake impounded by the Salmon Springs advancement of a great glacier known as the Puget lobe of the Cordilleran Ice Sheet. 

Around 17,000 years ago, this 3,000 foot-thick hunk of glacial ice had made its way down from Canada, sculpting a path south and pushing its way between the Cascade and Olympic Mountains. The ice touched down as far south as Olympia, stilled for a few hundred years, then began to melt.

After the ice began melting and retreating north, the landscape slowly changed —  both the land and sea levels rising — and great freshwater lakes forming in the lowlands filled with glacial waters from the melting ice. The sea levels rose quite considerably, about one and a half centimetres per year between 18,000 and 13,000 years ago. The isostatic rebound (rising) of the land rose even higher with an elevation gain of about ten centimetres per year from 16,000 to 12,500 years ago.

Around 14,900 years ago, sea levels had risen to a point where the salty waters of Puget Sound began to slowly fill the lowlands. Both the land and sea continued to rise and by 5,000 years ago, the sea level was about just over 3 meters lower than it is today. The years following were an interesting time in the geologic history of the Pacific Northwest. The geology of the South Fork Skokomish River continued to shift, undergoing a complicated series of glacial damming and river diversions after these salmon remains were deposited.

Today, we find their remains near the head of a former glacial lake at an elevation of 115 metres on land owned by the Green Diamond Company. The first fossil specimens were found back in 2001 by locals fishing for trout along the South Fork Skokomish River.

Upon seeing the fossil specimens, Smith teamed up with David Montgomery of the University of Washington, Seattle, along with N. Phil Peterson and Bruce Crowley, a Late Oligocene Mysticete specialist from the Burke Museum, to complete fieldwork and author a paper.

The fossil specimen you see here is housed in the Burke Museum collection. They opened the doors to their new building and exhibitions in the Fall of 2019. These photos are by the deeply awesome John Fam from a trip to see the newly opened exhibits this year. If you fancy a visit to the Burke Museum, check out their website here: https://www.burkemuseum.org/.

David B. Williams did up a nice piece on historylink.org on the Salmon of the Puget lowland. You can find his work here: https://www.historylink.org/File/20263

If you'd like to read more of the papers on the topic, check out:

• Smith, G., Montgomery, D., Peterson, N., and Crowley, B. (2007). Spawning sockeye salmon fossils in Pleistocene lake beds of Skokomish Valley, Washington. Quaternary Research, 68(2), 227-238. doi:10.1016/j.yqres.2007.03.007.
• Easterbrook, D.J., Briggs, N.D., Westgate, J.A., and Gorton, M.P. (1981). Age of the Salmon Springs Glaciation in Washington. Geology 9, 87–93.
• Hikita, T. (1962). Ecological and morphological studies of the genus Oncorhynchus (Salmonidae) with particular consideration on phylogeny. Scientific Reports of the Hokkaido Salmon Hatchery 17, 1–97.

If you fancy a read of Crowley's work on Late Oligocene Mysticete from Washington State, you can check out:  Crowley, B., & Barnes, L. (1996). A New Late Oligocene Mysticete from Washington State. The Paleontological Society Special Publications, 8, 90-90. doi:10.1017/S2475262200000927

WASHINGTON'S PILLOW BASALT RHINOCERAS

The Miocene pillow basalts from the Lake Roosevelt National Recreation Area of central Washington hold an unlikely fossil. 

What looks to be a rather unremarkable ballooning at the top of a cave is actually the mould of a small rhinoceros, preserved by sheer chance as its bloated carcass sunk to the bottom of a shallow lake just prior to a volcanic explosion.

We have known about this gem for a long while now. The fossil was discovered by hikers back in 1935 and later cast by the University of California palaeontologists in 1948. 

The Dirty Thirties & The Great Depression

These were the Dirty Thirties and those living in Washington state were experiencing the Great Depression along with the rest of the country and the world. Franklin D. Roosevelt was President of the United States, navigating the States away from laissez-faire economics. 

Charmingly, Roosevelt would have his good name honoured by this same park in April of 1946, a few years before researchers at Berkeley would rekindle interest in the site.

Both hiking and fossil collecting was a fine answer to these hard economic times and came with all the delights of discovery with no cost for natural entertainment. And so it was that two fossil enthusiast couples were out looking for petrified wood just south of Dry Falls on Blue Lake in Washington State. While searching the pillow basalt, the Frieles and Peabodys came across a large hole high up in a cave that had the distinctive shape of an upside-down rhinoceros.

This fossil is interesting in all sorts of ways. First, we so rarely see fossils in igneous rocks. As you might suspect, both magma and lava are very hot. Magma, or molten rock, glows a bright red/orange as it simmers at a toasty 700 °C to 1300 °C (or 1300 °F to 2400 °F) beneath the Earth's surface.

A Rhinoceros Frozen in Lava

During the late Miocene and early Pliocene, repeated basaltic lava floods engulfed about 63,000 square miles of the Pacific Northwest over a period of ten to fifteen million years. After these repeated bathings the residual lava accumulated to more than 6,000 feet.

As magma pushes up to the surface becoming lava, it cools to a nice deep black. In the case of our rhino friend, this is how this unlikely fellow became a fossil. Instead of vaporizing his remains, the lava cooled relatively quickly preserving his outline as a trace fossil and remarkably, a few of his teeth, jaw and bones. The lava was eventually buried then waters from the Spokane Floods eroded enough of the overburden to reveal the remains once more.

Diceratherium tridactylum (Marsh, 1875)

Diceratherium (Marsh, 1875) is known from over a hundred paleontological occurrences from eighty-seven collections.

While there are likely many more, we have found fossil remains of Diceratherium, an extinct genus of rhinoceros, in the Miocene of Canada in Saskatchewan, China, France, Portugal, Switzerland, and multiple sites in the United States.

He has also been found in the Oligocene of Canada in Saskatchewan, and twenty-five localities in the United States — in Arizona, Colorado, Florida, Nebraska, North Dakota, Oregon, South Dakota, Washington and Wyoming.  

Diceratherium was a scansorial insectivore with two horns and a fair bit of girth. He was a chunky fellow, weighing in at about one tonne (or 2,200 lbs). That is about the size of a baby Humpback Whale or a walrus.

Back in the Day: Washington State 15 Million-Years Ago

He roamed a much cooler Washington state some 15 million years ago. Ice dams blocked large waterways in the northern half of the state, creating reservoirs. Floodwaters scoured the eastern side of the state, leaving scablands we still see today. In what would become Idaho, volcanic eruptions pushed through the Snake River, the lava cooling instantly as it burst to the surface in a cloud of steam. 

By then, the Cascades had arrived and we had yet to see the volcanic eruptions that would entomb whole forests up near Vantage in the Takama Canyon of Washington state. 

Know Before You Go

You are welcome to go see his final resting site beside the lake but it is difficult to reach and comes with its own risks. Head to the north end of Blue Lake in Washington. Take a boat and search for openings in the cliff face. You will know you are in the right place if you see a white "R" a couple hundred feet up inside the cliff. Inside the cave, look for a cache left by those who've explored here before you. Once you find the cache, look straight up. That hole above you is the outline of the rhino.

If you don't relish the thought of basalt caving, you can visit a cast of the rhino at the Burke Museum in Seattle, Washington. They have a great museum and are pretty sporting as they have built the cast sturdy enough for folk to climb inside. 

The Burke Museum 

The Burke Museum recently underwent a rather massive facelift and has re-opened its doors to the public. You can now explore their collections in the New Burke, a 113,000 sq. ft. building at 4300 15th Ave NE, Seattle, WA 98105, United States. Or visit them virtually, at https://www.burkemuseum.org/

Photo: Robert Bruce Horsfall - https://archive.org/details/ahistorylandmam00scotgoog, Public Domain, https://commons.wikimedia.org/w/index.php?curid=12805514

Reference: Prothero, Donald R. (2005). The Evolution of North American Rhinoceroses. Cambridge University Press. p. 228. ISBN 9780521832403.

Reference: O. C. Marsh. 1875. Notice of new Tertiary mammals, IV. American Journal of Science 9(51):239-250