Geology of the Walla Walla Area Dr. John D Winter Department of Geology The French use the term “Terroir” to describe the complex interplay of temperature, sunshine, rainfall, soil, bedrock, viticultural practice, and other physical factors that influence the character and quality of wine

Defined by elevation contour on S and E, and by lines approximating drainage divide on the N Revised effective April 27, 2001 VAs defined by US Bureau of Alcohol, Tobacco, and Firearms- define by geography Appelations of France defined in terms of wine characteristics

The Modern Plates

Three types of plate boundaries

Age of the ocean crust

Hot Spots

Convergent boundary Three sub-types l Ocean-Continent l Ocean-Ocean l Continent-Continent Can you name an example of each?

Plate Tectonics in the Pacific Northwest

Igneous Processes

The Edge of the North American Craton Mantle has low Rb which  87 Sr over time, so low 87 / 86 Old continental crust has high Rb so high 87 / 86

Terranes of NE Oregon

Filling of the Columbia Embayment Westward roll-back of subduction Fills Columbia Embayment Stabilized near present location for ~ 40 Ma Cascade range: Uplift affects climate on east side Volcanoes supply ash to winds and area

The Columbia River Basalts

Aerial extent of the N2 Grande Ronde flow unit (approximately 21 flows). Aerial extent of the N2 Grande Ronde flow unit (approximately 21 flows).

The Columbia River Basalts Location of the exposed feeder dikes red) and vents (blue V's) of the southeastern portion of the Columbia River Basalts.

WW CRBs probably result from SRP- Yellowstone hot-spot- difficult to explain northward deflection

The Columbia River Basalts Basalts yield excellent soils in Hawaii and other tropical areas where rainfall is high and the climate is warm Our soils in WW are not derived from the underlying basalts- an unusual feature

Continental Glaciation ~ 125,000 until 13,000 years ago

Continental Glaciation Wind-blown Loess deposits

Palouse Hills to north of WW: > 10,000 km 2 and up to 75m thick (depends on sub-loess topography)

The Great Floods ~ 12,000 years ago Ice dam founders and releases up to 2500 km3 of water out across the plateau

The Great Floods ~ 12,000 years ago J Harlan Bretz in 1930’s- a controversial proposal

The Great Floods ~ 12,000 years ago

The Great Floods ~ 12,000 years ago- Burlingame Canyon Suggests up to 90 individual floods WW received silts as “slackwater” deposits Sediments range from gravels near Wallula to massive silts and sands toward Blue Mts Winds continue to redistribute loess, silts, ash, etc.

Uplift of Blue Mts. Erosion by river system Mill Creek, Cottonwood, Birch Creek...Walla Walla River Valley erosion in Blues  floodplain sediments in WW valley

Walla Walla River Floodplain Note Horse Heaven Hills- anticline of folded CRBs

Surface geological units Note old WWVA boundaries- pre-2000 vineyards are in black Strong correlation between units and elevation (also climate) Basalts at highest elevations and where erosion exposes them Loess at higher elevations than slackwater deposits (north and on Blues-Horse Heaven Hills)- mostly silt Slackwater deposits: mostly sand and silt in WWVA Loess and slackwater silts are glacial- derived from Canada- qtz-feldspar..not basaltic Floodplain at lowest elevation-locally cobbles, gravel, sand, silt, clay- highly variable From Meinert and Busacca, Geoscience Canada, 27,

Soil textural classes WW very low in clay except in some areas of the WW River floodplain

Soil Types From Meinert and Busacca, Geoscience Canada, 27, ~75 soil types in WW Soil Survey, can lump into ~8 groups (remember strong elevation-rainfall gradient too) 1- Cobble-loam-silt of floodplains and terraces of WW River and tributaries: long used for orchards- most vineyards now on the terraces with thin loess Well-drained, and low organics- permits good control of grape vigor by management of water and nutrients 2- Loamy to silty in same floodplain-terrace areas Poorly-drained, saline and alkaline- good for onions- Three Rivers on a well- drained terrace close to these 3- Loess over slackwater deposits on dissected terraces and uplands Well-drained and silty Woodward Canyon Vineyard Where loess thin (<60 cm) and low elevation cost of water may be a problem 4- Similar to 3- Loess over slackwater on dissected terraces Silty, uniform, low to mod organic matter- extensive vineyards 5- Excessively drained sandy soils of dunes with < 30 cm/yr rain some juice grapes 6- Silty soils of deep loess on uplands cm/yr rainfall 7- Silty soils of deep loess on uplands cm/yr rainfall- more organics 8- Loamy to cobbly well-drained soils on steep mountain slopes- Figgins Mill Creek Upland Vineyard is only one yet

Wind and rainfall patterns From Meinert and Busacca, Geoscience Canada, 27,

SW-NE Cross Section WW vineyards on four fundamentally different substrates: slackwater terrace, loess, river gravel, and floodplain silt Majority are in loess, either thick over basalt or thin over slackwater silts (which in turn are on basalt) Again, well-drained silts with low organics allow the vintner to manage moisture and nutrients Overly fertile floodplain soils develop strong vegetal flavors Good slopes allow good airflow too- colder air sinks away so fewer frost problems Cristophe Baron’s Caillouxe – searched with Kevin Pogue for very cobbly floodplain area- Forces roots deep, heated cobbles radiate, calcic soils stress vines combine to - > very concentrated fruit

Some Examples From Meinert and Busacca, Geoscience Canada, 27,

Examples Pepper Bridge cabernet on thin loess Vineyard-covered “island” of slackwater deposits on WW River floodplain Cottonwood Creek vineyard chardonnay grapes on floodplain silts over gravel From Meinert and Busacca, Geoscience Canada, 27,

Examples Caillouxe vineyard syrah on floodplain gravels. E shows trench and deep roots. From Meinert and Busacca, Geoscience Canada, 27,

Examples Seven Hills on 2 meters of loess (over slackwater deposits) Canyon-bottom floodplain soils are better for fruity wines, such as Biscuit Ridge Gewurtztraminer) Mill Creek Upland vineyard tries out the higher-elevation loess Generalizations: Low-precipitation during growing season, low organics, well-drained silts allows the vintner to control moisture and nutrients to develop vigor and complexity (and yield) Highest quality vineyards lower their yield to 2-3 tons/acre (compared to 4-5 ton statewide average) W  E variation in elevation & rainfall, plus variations in soils, drainage, organic content, water table level of loess, slackwater deposits, floodplain  Rich diversity of Terroirs Latitude affects summer sunlight and temperatures (day and night) Unique geological and soil features in WW suggest that our wines “may develop flavor and quality characteristics that set them apart from other wine-producing areas”