GEOLOGY, TERROIR, AND THE WINEMAKER'S DANCE

Winegrowers are subject to an array of analytical, intellectual, sensory, kinesthetic, and intuitive input. The feel of breeze on the skin, the crunch of soil beneath the boot, the touch of a vine tendril, a glimpse of the grapes, all are as important as the spreadsheet that reports tonnage, the analyses of acid and pH, or the sophisticated new technologies now being introduced. Winegrowers integrate this information in a natural and magical human way and manifest the result in the wine they produce. We have called this process The Winemaker’s Dance. Each winemaker dances to a different melody or rhythm, finding their own way of making sense of the data that is available to them. In the realm of geology, winegrowers’ understanding of substrate has been limited in the past to information provided by soil analysis, a descriptive discipline. In studies in Napa and Sonoma, we have concluded that drainage and accessibility to water—attributes controlled dominantly by substrate texture and structure, mainly the result of geological processes—are the primary controls on grape quality and character, not soil type. We encourage winegrowers to characterize properties from a geological perspective and we are suggesting that they think about vineyard substrate in geological, and thus genetic, terms in addition to those of soil analysis. One person characterized our approach, perhaps jokingly, as “agricultural heresy,” though we are suggesting only the addition of geological notes to the tunes and rhythms of the dance, with the notion that this information will enhance and expand understanding of vineyard variability and the effect of physical terroir on grapes and wine. Three vineyards in Napa and Sonoma help illustrate some of the directions this work is taking. Benoist Vineyard is a 1280 acre parcel planted with 570 acres of grapes, and underlain by three bedrock units as well as recent alluvial sediments. Stag’s Leap Wine Cellars’ Fay and SLV vineyards grow mainly on alluvial fan sediments, but show considerable internal variability. The vineyards at Rudd Estate sit at the base of the Vaca Mountains on the lowermost of several uplifted and down-dropped pediment surfaces. Half the vineyard acreage is developed on bedrock, half on an alluvial fan.