The mystery of rock(s)

No, not the majesty of roll. It’s the mystery of terroir in the northern Willamette Valley.

Such was the title of Dr. Scott Burns’ presentation the other night to the Geological Society of Oregon. More than 60 people filled a lecture hall at Portland State University, where Burns works, to learn about the geology and soils of our local winegrowing region.

Burns is a passionate speaker, not what you might expect in a geologist. He began by apologizing for his scratchy voice, worn out from a heavy dose of consultation and media requests in the wake of recent rain-triggered landslides. Then he launch into a high volume, fast-paced hour-long presentation covering everything from the origins of the Oregon wine industry to, eventually, terroir. His voice held up fine.

Burns is rare in bringing obviously extensive knowledge about geology together with great knowledge and clear passion for wine. Frankly, I expected a geologist who knew little, really, about wine, but Burns is one of the most articulate and, in my opinion, informed wine lovers out there. Generous too.

I was hoping he’d spend less time on background material and more on the rocks. This was a geology meeting after all, my first ever. But the audience was clearly beyond the typical rockhound, so I suppose Burns was smart to give context even if it was old news.

But once Burns started talking about the earth, wow. He provided great information I hope I convey at least mostly accurately. First of all, good news. The soils are old here, meaning low nutrient levels in general for grape growing. 96% of grapes in the region are on either very old, or just about very old soils.

The underlying geology of the northern Willamette Valley largely consists of volcanic basalts and ancient marine sediments. The basalts came from lava flows originating hundred of miles to the east approximately 14-16 million years ago. The marine sediments were once under the ocean before being pushed into hills and mountains by tectonic activity.

Local soils largely came from Missoula flood sediments from approximately 15,000 years ago, when receding glaciers from the last Ice Age repeatedly flooded the Willamette Valley, leaving gorgeous soils on the valley floor. The old soils are up on the hills, windblown deposits along with eroded bedrock. Soil depths vary widely, from nothing to a few feet, to more than 50 feet.

The most common soil types in northern Willamette Valley wine regions are Jory and Willakenzie, with a variety of others mostly represented in far fewer planted acres. Jory soils are most commonly found in the Dundee Hills, where occasionally deep red soils cover volcanic basalts. You also find some Jory in the Eola Hills, though more of the up-and-coming Nekia soils. Nekia is like Jory, volcanic but only a few feet deep. Roots here get down into the bedrock easily.

Willakenzie soils are apparently being reclassified more specifically than before. But as we know them, they are marine sediments found in the Chehalem Mountains and Ribbon Ridge (I believe also in sites around Yamhill/Carlton and McMinnville Foothills). Burns said wines from Willakenzie soils produce red-fruited wines, while Jory soils produce black-fruited wine. But I think that’s mixed up.

Demonstrating the different tastes of soil types, Burns closed by generously poured samples of two 2001 Chehalem Pinot Noir.

First the Stoller Vineyard, from the far west of the Dundee Hills on a lower hill exposed perfectly to the sun. Jory soils all the way. This wine smelled rich and alcoholic, with macerated cherries and a roasted quality. It was actually quite nice, wood-marked as both wines are, but soft and a little squishy.

I preferred the Ridgecrest Vineyard, with its wood spicy, light black currant aroma and brighter flavor. Willakenzie soils here, Chehalem Mountain appellation. But I think micro-climate played a bigger different here than soil, with the heat of Stoller showing clearly versus the cooler profile of the higher elevation Ridgecrest.

So are all Geological Society meetings like this? The meeting ended, but there was a buffet after-party in the department office that looked interesting. Then I thought, don’t push your luck. So off into the rainy night.