Pisoni Vineyards from Below:
A Short History of Monterey County’s Geology

Late afternoon light over the vineyards beneath the Santa Lucia Highlands.
The foothills of the Santa Lucia Highlands, bask in a brief moment of sun.

Wine is often described in terms of its minerality, and winemakers are quick to consider the role soil composition plays in grape-growing. But we don’t often think about the rocks whose slow shifts across the eons have played their own part in supporting the complex amalgam of compounds in the earth that lies above them. At Pisoni, we work in accord with the annual cycle of seasons. But we also like to take the long view of the land that sustains us. In the piece that follows, we approach our vineyards from Earth’s time rather than our own. We hope you enjoy this geological journey through the region we love.

The rocks below what John Steinbeck called in East of Eden “the thin flinty soil” around Salinas have been around a long time. How long? Cast your mind back fifteen thousand years ago to the time when the ancestors of California’s present-day Ohlone peoples settled by Monterey Bay to hunt and fish after walking across the land bridge over the Bering Strait. Then unspool the thread of time a hundred times this length, to the beginning of the Miocene Epoch some 23 million years back when mammals came to be. Now toss the line ten times farther than you just unspooled it and find yourself in the middle of the Jurassic when dinosaurs strode the Earth and the first flowering plants opened colors to the sun our sky had never seen. From this point, unspool the line hundreds of millions of years more, before the birth of fungi and fish, and take in for a moment the late Precambrian when only algae ruled the Earth.

During the Precambrian era, some of the stone below the rocky soils of the Santa Lucia Highlands where our vineyards are located solidified from molten material deep within the crust. But in those early days of Earth, the rocky material geologists would come to call the Sur Series after identifying it along the coast at Big Sur actually resided far to the south in the Mojave Desert.

During the Nevadan orogeny that took place in Jurassic and Cretaceous times and that began some 165 million years ago, the tectonic plates that meet on the western edge of the American continent began to collide. This collision continued–it continues still in northern California, as it does in Oregon and Washington. 80 million years before we appeared on the scene, during a particularly dynamic period of igneous activity not long before the dinosaurs became extinct, melted material erupted through Earth’s crust. Eventually, the material that intruded into the Sur Series and Sierra de Salinas rock and which composes the Salinian Block hardened into the granite climbers walk up Yosemite’s Half Dome as well as the unyielding stone Gary drilled down into to find a wellsite for our vineyards. If you wanted to explore one of these intruded granite batholiths from toe to tip, you would need to descend 6-9 miles below where hikers and vineyard managers like Mark Pisoni walk—as far a distance below ground as planes fly when they cruise above Earth’s surface.

Until around 24 million years ago, the Sur Series with its intruded granite remained in the Mojave Desert area. After the plates that meet at the edge of the American continent began to slip past each other in parallel, they created the coastline we see as well as the area through which the San Andreas fault runs. Gradually, the rock mixture that now lies below our land was dragged piecemeal some two hundred miles north. Like a sheared deck of cards, the rocks crept and slid into their current placement, which runs from the area around Bodega Bay south to Mount Pinos in the Los Padres National Forest.

A rare cutaway of Monterey County’s geology; detailing the current and prehistoric past of this region.

Our land sits atop alluvial fans, fan-like deposits of sediment that spread out on valley floors below fast-flowing mountain streams. Composed of the igneous granite that makes up the Salinian Block as well as the bands of schist and gneiss produced at very high temperatures, these deposits of sediment are older than the alluvial fans that underpin the rock of the Santa Lucia Highlands north of our vineyards.

By contrast, and less ancient, are the materials of the Franciscan complex distributed throughout the California coast ranges and the San Francisco Peninsula. Much of this stone, churned and mixed as if with a blender by the movements of tectonic plates, formed during the Cretaceous Period and the late Jurassic. It, too, is composed of metamorphic rock, but contains largely shale and sandstone mixed in with chert, greenstone, and serpentine–materials formed under pressure from rock that is oceanic in origin.

A close look at an interlay of rocks and gravel soils on Pisoni Vineyards.

The Franciscan Complex and the other materials that make up the Salinian Block all developed out of the relationship between three tectonic plates: the Pacific, the North American, and the Farallon. (Consider how much energy, in the form of heat, you give off when you rub your hands together quickly. Now, think of the hard, brittle sections of the Pacific and the North American plates gliding above Earth’s mantle as giant hands pressing and sliding alongside one another, and imagine how much stress is created.) The Farallon, an oceanic plate like the Pacific, slowly got pushed underneath the North American plate and is lost to us now. At the area where the Farallon began to dive underneath the North American plate (subducted, geologists say), there was a great deal of friction, which ripped off pieces of both the Pacific and North American plates. This subduction zone, created from the press of two opposing sides, was put under great stress. (Imagine that you’ve cupped a substance like bread or cereal or even a chocolate chip cookie between your hands. When you rub them together, that substance gets heated and twisted and broken—and your hands become a sticky mess.) Just so, the rock caught betwixt and between the two plates was churned and turned and melded by the pressure into metamorphic material. Most of the Farallon was pushed miles below the surface into Earth’s mantle ten million or more years ago. But the diverse material at the area where it began to slip under the North American plate eighty million years before that remains. This material, chemically changed through the process of metamorphosis, created the single mountain range known as the Sierra de Salinas–a mountain now comprised of bands of schist and gneiss with extended alluvial fans where the current-day Santa Lucia Highlands reside.

Geologic map of California
The overview of California’s dynamic geology. Observing the granite-based rocks (indicated in red), one can see the path they had taken from Southern California to where they were been pushed and dragged up through the coastal range and all they way to Point Reyes.

The faulting produced by the movement of these plates and which dragged the stone of the Salinian Block into its current location witnessed massive activity until 3 million years ago. During this period–yesterday on Earth’s calendar–the San Andreas and its neighbor, the San Gregorio, began to slide against each other very rapidly. Compression pushed the western plate of the Pacific toward the eastern North American plate. This collision wrinkled the Earth’s crust, uplifting slabs of the Salinian block into the Santa Lucia Range. While the rest of the Salinian Block is igneous and origin and dates to Precambrian times, the Santa Lucias are made of metamorphic rock laid down during the Cretaceous Period of the Mesozoic Era.

Here, in this foggy, windswept place, our vineyards are located. Climatic changes that occurred after their initial formation have introduced even more complexity to the rock of this region. During the end of the last ice age, the ocean crept further inland and laid marine sediments atop the coarser soils eroded from the peaks. It turns out that the “thin flinty soil” Steinbeck wrote of in East of Eden is made of stronger stuff than he supposed. Composed of schist and gneiss (unlike the sandstones of Sonoma and the limestones and clays of Burgundy), it is full of decomposed granite. At Pisoni we work hard to create wine that possesses complexity. But it is the complex materials created by Earth’s enduring labor that make all our efforts possible.


Written by Anne Goldman


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