How Bandon's Face Rock Was Created A Wild S. Oregon Coast Geologic Tale

Published 03/02/21 at 5:50 AM PDT
By Oregon Coast Beach Connection staff

(Bandon, Oregon) – At Bandon, on the southern Oregon coast, one face is a familiar one to just about everyone that’s been there. The rock structure known as Face Rock offshore is burned into people’s brains upon first sight, with its wrinkled, mummy-like appearance and stark, face-like features. To borrow a modern phrase, “you can’t unsee that.” (Photo courtesy Manuela Durson - see Manuela Durson Fine Arts for more)

Its native people’s origin story is a wild one and striking as well, telling of an Indian girl who was lured out to sea farther and farther until she was turned to stone, along with a pack of kittens nearby.

Face Rock’s scientific origin is much older and much more complex. She – called Ewauna by original Coquille tribes - actually clocks in at somewhere between 56 million to 201 million years old. This is not just because scientists can’t entirely pin down when it formed but because its formation took numerous stages that are in different periods over that time. It has bits and pieces of many different time periods inside it.

Oregon Coast Beach Connection talked at length with Coos Bay geologist Ron Metzger (Southwestern Oregon Community College) and geologist / author Marli Miller (UofO). One thing is clear, this trip back through time is ….well, trippy. (See her books like Roadside Geology of Oregon)

“The age of Face Rock would be one thing; the age of the rocks in Face Rock would be another,” starts off Metzger, with no small degree of crypticness. Yet when you realize what that means it utterly fills you with awe.

(Photos above courtesy Donna Belt and Bandon Visitors Center)

Basically, according to Metzger, Face Rock is part of something called the Sixes River Terrane, a deep bedrock formation that runs through much of this part of the southern Oregon coast. Its creation is all over the place in that long period of 201 to 56 million years ago. This chunk was under the ocean most of the time and eventually uplifted, sank back down, did this a few more times (probably) and eventually wound up near the surface.

Somewhere in that period, these sea stacks that form Face Rock, the Kittens and Komax (her dog) were carved out of some larger structure by erosion – some mass of rock that was maybe a higher structure or simply something that jutted out from where greater Bandon is now. It’s even possible the 1700 quake and tsunami had something to do with carving out some of its shape.

Then again, Metzger said, the face shape we see could’ve been there for thousands of years.

Hence the idea that the age of the face shape is different than the rocks inside it.

But oh the fiery, freaky tale those rocks tell – as well as the other rock formations around Bandon.

What Face Rock is made of is called a melange – a mixture of various rocks. Some of it is bluechist (a really hard rock), some is lava, lots of sedimentary rock (stuff that floated down to the bottom of the ocean), and more.

“In this case likely mudstone and fine sandstone matrix with jumbled blocks (metamorphic),” Metzger said. “So generally, yes to ocean floor sediments, tectonics leading to subducted sea stacks - resulting in metamorphics – like the famous Bandon Blueschist.”

Metamorphics? No, it’s not an evil comic book character. For this we have to go back farther in time.

Here’s another weird bit: the Sixes River Terrane originally came from somewhere else, starting maybe 200 million years ago. It formed through another subduction zone (like our big, nasty Cascadia Subduction Zone), at some other location offshore. Miller said scientists aren’t positive where it came from, but they know it slowly, over millions and millions of years, got pushed over here. It could be from as far away as California.

A terrane is a massive rock formation created via a subduction zone (where two continental plates meet) that then moves along and is welded to some other continental shelf. Continental plates move at something like the rate of a finger nail growing, so yes – that’s a lot of movement in 200 million years or so.

When this terrane formed in those sizzling zones between plates, a lot of rocks fell into it but didn’t always have a chance to heat up. These rocks are metamorphics, like bluechist.

“These sediments came in and got mixed,” Miller said. “They were carried to great depths really quickly, so there was not a lot of time for them to heat up. It was an assemblage of minerals under high pressure but low temperature conditions.”

This is what’s inside Face Rock. Miller said geologists have inspected it – either up close or through high resolution photos – so they know its composition.

The technical term for the age of Face Rock and the Sixes River Terrane is “Mesozoic in age (undifferentiated Cretaceous-Jurassic),” Metzger said.

In turn, the Sixes Terrane is part of a larger terrane called the Franciscan Terrane, which contains numerous chunks of lands beneath the south coast region. The Franciscan typifies the rather insane complexity of geology on the southern coast. It’s not like the northern half, where many of the things we see have the same origin.

Photo Oregon State Parks and Recreation Department

Of south Oregon coast geology Miller emphatically says: “It IS a dozen different things.”

“The Franciscan especially is just a mess,”Miller said. “The idea that all these terranes came together and got mixed up together in this subduction zone nicely explains why it’s so hard to explain.”

Bandon Beach itself is a kind of metaphor for this area’s diverse geology. There’s so much going on here that you don’t know about.

“Just walk about the sea stacks at Bandon - a lot of them are sandstone,” Miller said. “But a lot of them are highly fractured and faulted. Go down the beach and another block is different altogether. It’s really wild to see all these different rock types kind of thrown together.” More photos below

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Courtesy Donna Belt and Bandon Visitors Center

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