“Land is not merely soil; it is a fountain of energy flowing through a circuit of soils, plants, and animals.”
Aldo Leopold

By Robert Fiore, Winemaker

La terre rouge: “red dirt.” Four crystal vessels tastefully hanging on the wall greet the visitor entering the Calvin Holmes Suite at our Knights Valley Estate: one stands out for its rich crimson hue, distinctly different from the other three vessels containing soils and rocks from our Seaview Estate, and from Les Pavots Vineyard and Belle Côte Vineyard in Knights Valley.

The soils from our Oakville Estate are unmistakable. When I walk through each vineyard block tasting berries before harvest, the soft red soil compresses gently under my boots, displaying the hallmark of well-drained, healthy, structured soil. Under the steady guidance of our vineyard manager, Javier Aviña, and Oakville foreman Mario Garcia, the vineyard is impeccably cared for, and the resulting fruit is stunning. Some vines date back to the early 1980s and 1990s. ‘Au Paradis’ Cabernet Sauvignon exhibits high-quality, fine-grained tannins with grace and power, and it all begins with this special terroir. While ‘Le Chapeau Blanc’ Cabernet Franc comes from a single old-vine, 2-acre (0.8-hectare) block at the northern end of the property, it similarly produces wines of extraordinary depth and substance.

Although some of the larger rocks were removed from the soil to allow for drainage and root development, a layer still remains around the vines. This can retain warmth from the sun and assist with water retention by shading the soil.

The rocks that compose the soils for the Au Paradis and Le Chapeau Blanc vineyards originated from volcanic activity over four million years ago. While our Knights Valley Estate vineyards are underlain by rhyolite, both in solidified-lava and ash-flow form, the Oakville Estate vineyards have soils composed of andesite and basalt. The Knights Valley volcanic rocks erupted three million years ago, about one million years after the Oakville volcanic rocks were lain down. The silica content of the magma drastically changed how the two terroirs were conceived: the lower silica content in the Oakville magma allowed gases to escape on its journey through the crust, resulting in a less explosive entrance to the surface and more lava flows, which cooled to the gray andesite rocks that are there today. The more viscous, higher–silica content magma in the Mount Saint Helena volcanics at the Knights Valley Estate resulted in a much more explosive event, producing rhyolitic ash-flow tuff and lavas generally white, tan, or brownish in color.

Gray andesite is the primary rock in the Oakville soils.

Oakville red dirt, which is gray andesite that has been exposed to oxygen.

Teams meticulously hand-harvest the estate, ensuring the fruit is not damaged before arriving at the winery.

Despite the beautiful red soils covering the twelve blocks that contribute to Au Paradis, the actual rocks from which the soils are derived are a light to medium gray color on the interior. Pick up a reddish rock in the vineyard, then smash it open with your geologic hammer, and you will find a gray rock—none will be red throughout the interior. The red exterior comes from the oxidation of iron and aluminum to the familiar reddish rust color. Over a few million years, enough of the gray bedrock has eroded in place into the soil to produce the remarkable red Oakville terroir.

However, the plateau on which the vineyard sits was not always in its current position; it harbors an interesting structural geologic past. At some point, the entire plateau slipped down along a displacement fault, separating the bench from the rest of Pritchard Hill above. Unlike an alluvial fan or landslide, where geologic material of various sizes and compositions are transported by water or gravity and then lain down as a new deposit in a new arrangement, the bench on which our Oakville Estate rests appears to have been brought down en masse, essentially intact from above, along the fault.

“Pick up a reddish rock in the vineyard, then smash it open with your geologic hammer, and you will find a gray rock—none will be red throughout the interior.”

The beautifully tranquil scenery throughout Napa Valley belies a fascinating, active geological history. While the Sierra Nevada range to the east dates back over sixty million years, most of what formed the structure of Napa Valley occurred in the last five million years. Volcanic activity at the southern end of today’s valley was followed by the Stag’s Leap volcanic flows four million years ago, which make up our Oakville Estate. The volcanic flows were originally lain down flat prior to the formation of Napa Valley. However, around three million years ago, compressional forces linked to the San Andreas Fault system began thrusting layers of rocks onto each other, creating what we now know as the Vaca Mountains on the east side of the valley. The western edge of the thrusting formed what is now the Mayacamas Mountains on the west side of the valley. Most of the faults bounding Napa Valley that are active today are linked to the San Andreas Fault system. Although the most recent volcanic rocks in Napa Valley were created almost three million years ago, geothermal activity is still present in the form of hot springs and geysers.

Winemaker Robert Fiore displays the contrasting ash-flow tuff of the Knights Valley Estate, showing the contrast against the red soils of Oakville.

Incredible rock formations are naturally displayed throughout the estates.

Very much as in Burgundy, the position on the slope plays a significant role in determining the qualities of the wines produced from the terroir at the Peter Michael Oakville Estate. The northern end of the vineyard is planted with old-vine Cabernet Franc (1983) on a gentle slope, with the steeper upper portion producing the remarkably concentrated fruit for ‘Le Chapeau Blanc.’ This special block consistently shows wines often equaling Cabernet Sauvignon in terms of density, power, and phenolic compounds. The wines show an uncommon level of depth and polish. At the base of the slope is an exciting younger block of Cabernet Sauvignon.

Across the vineyard lane to the south, the next parcel is planted entirely to older-vine Cabernet Sauvignon. The terraced upper portion is steepest, with wines that exhibit high levels of tannin and color. The midslope portion rivals the terraces in terms of the firmness of tannins, and the two parcels combine as key structural components in the ‘Au Paradis’ blend. The bottom parcel has the gentlest slope, with wines that are distinctly different from their upslope neighbors. Here, the terroir creates an exceptionally polished, fleshy Cabernet Sauvignon with supple, silky tannins that help fill in the body of ‘Au Paradis.’ This block already shows its tender qualities in the fermentation tank and becomes even more refined during barrel aging.

The next parcel to the south is made up of three distinct sections sloping from northeast to southwest. The upper block is planted to old-vine Merlot, with the top rows terraced to account for the steeper slope. These thirty-year-old vines produce highly aromatic wines that contribute floral and fruit elements to the blend. The midslope section features an extraordinary terroir that produces the most complete single-block Cabernet Sauvignon wine on its own from the property: elevated aromatics, great structure, and depth with generous, polished tannins. The bottom portion of the slope is an old-vine Cabernet Sauvignon block contributing more fruit-forward wines to the ‘Au Paradis’ blend. Just to the south in the lower portion of the slope is an island block of old-vine Merlot that tends to ripen just after its northern, upslope Merlot neighbor. The wines offer beautiful aromatics and a juicy liveliness to the final wine.

A structural geologic history of Napa Valley. Starting at the bottom, Figure A represents Napa Valley three million years ago: the volcanic rocks (including the Oakville Estate) depicted in red were already in place and deposited horizontally, and no valley existed. Figure B shows the first compressional events that broke the rock’s horizontal beds and thrust them upon each other. Figure C shows the wearing down, or erosion, of the thrusted rocks to a flatter surface. Figure D shows a second period of thrusting, which helped form the mountain ranges and Napa Valley as it is today.

Continuing across the road to the south is the second half of the Peter Michael Oakville Estate. Other than one larger block of old-vine Cabernet Sauvignon, the vines here are younger, and the rows are oriented northeast to southwest up and down the slope as opposed to across the slope in the older blocks. The first block is planted to Cabernet Franc, which is quickly becoming a star element in the ‘Au Paradis’ blend with its deep raspberry, blackberry, and rose-petal aromas and plush, fleshy midpalate.

Fiore informs three generations of the Michael family about the origins of the estate soils.

An aerial shot showing key geomorphologic features around the Peter Michael Oakville Estate, with the elevation profile along the white line shown below the photo. The top right end shows vineyards on the fairly flat plateau of Pritchard Hill, then moves steeply down the fault scarp, then onto the bench upon which the Oakville Estate rests before descending onto the flat valley floor.

Heavenly clouds float above the golden vines of Oakville.

“The combination of the soil, elevation, slope, aspect, weather, and farming make the Peter Michael Winery Oakville Estate a unique and singular location to grow world-class wine grapes.”

Evening skies over Knights Valley.

Oakville Estate foreman, Mario Garcia, has been with Peter Michael since 2005 and became foreman of the Oakville Estate in 2009.

Throughout the cycle of the growing season, the team meticulously monitors and manages each vine, row by row.

The next two Cabernet Sauvignon blocks to the south comprise an interesting pair in terms of terroir. Here, two blocks with vines from the same genetic source material give entirely different wines. The more northerly of the two blocks is lower in elevation with a gentler slope at about 9 percent grade. In the fermentation tank, the wine’s expressive nose of violets, rose petals, blackberry, and cassis is supported in the palate with soft tannins, a rich but elegant midpalate, and a smooth finish. In contrast, the block to the south is steeper, achieving a 17 percent slope, and is at the highest elevation in the vineyard. The wines here are structured, have a deeper color, and have much firmer tannins, with a nose that is more dominated by black currant and black tea. Together the two contrasting blocks help make a beautiful, complete wine. Running below the Cabernet Franc and younger Cabernet Sauvignon block is the old Cabernet Sauvignon block with its cross-slope row orientation. This block is often the last Cabernet to ripen on the property, and it contributes black cherry and floral notes and plush roundness to the mouthfeel of the blend.

The combination of the soil, elevation, slope, aspect, weather, and farming make the Peter Michael Winery Oakville Estate a unique and singular location to grow world-class wine grapes. Each glass of ‘Au Paradis’ and ‘Le Chapeau Blanc’ tells this story.

The fruit from Oakville is carefully transported to the Knights Valley winery for sorting and eventually transferred to the tanks for fermentation and monitoring by Fiore and his team.

Some of the vines from the original planting needed to be replanted by Aviña and his team.

Flanking the valley floor of Oakville are plateaus to the east and west—the Peter Michael estate rests at 500 feet (152 meters) in elevation on the plateaus of the Vaca Range.

At the end of each fall, Mario and his team carefully lay hay in between the vineyard rows to prevent erosion during the winter months.