For the Geologically minded wine-critic, terroir is the signpost of destiny. Already, the geologist with his training and sharp eyes can see landscapes that are long gone, present only in fragments, but the critic of the wine who knows the deepest history of a place can take that fragment and taste it. The critic can parse the wine in his glass like a dead language, and make it alive by saying, “This wine smells of the ancient sea crashing upon wild shores,” and mean every word. This is why I feel terroir in wines is intensely important. Terroir doesn’t only tell you where the grape is from today, but it tells you where the grapes were from in the deepest of yesterdays.
Sonoita is the oldest commercial wine region in Arizona, and so far, Arizona’s only registered AVA. Grape growing here begins with Spanish missionaries in the 1700’s, with the planting of Mission Vines (known also as Listan Prieto, see a review of one here at http://azwinemonk.com/2014/09/25/2013-sonoita-vineyards-arizona-mission/) As the Missions for which these vines were planted faded into obscurity, some of these vines remained growing well into the 1970’s and 80’s. It is at about this time when the modern story of winemaking in Sonoita begins, with a geology professor named Gordon Dutt. Trying to find a good cash crop for Arizona that could withstand drought conditions, Gordon contemplated viticulture and began to look for places to test this theory.
Around thirty or so years ago, Gordon Dutt, a pioneering vintner and university professor was shown some gnarly old trunks of their vines on a hilltop by a local rancher on the old Babocamori Spanish Land Grant that sprawled across the Sonoita Plains of Southern Arizona. He then decided that the landscape around the Sonoita Plains was where he’d begin to grow. Viticulture was established once more in the landscape of the Sonoita Plains in 1979; Mission grapes were one of those which were planted here, once more. Soon, other vineyards followed suit; and an AVA followed. The geology of Sonoita and Elgin, it seemed to Dutt, was perfectly suited for grape growing; low hills at the foothills of the mountains, filled with alluvial gravels and with a good aquifer.
The Story of Sonoita’s geology begins in the Precambrian/Proterozoic. Rocks in this area are rare, only found at the summits of the nearby mountains, and they form the underlying basement of the whole region. The next oldest rocks which appear in the local region are Paleozoic ocean sediments; the majority of which are from the Naco formation. These limestones are roughly the same age as the red rocks of Sedona; remnants of the tropical Pedregosa sea once more, though here, the sea was much deeper. Brachiopods and horn corals are indicators of waters that were at least 100 or so feet deep.
There’s a space in the rock record between these layers and the next oldest rocks, which are from the Mesozoic era, specifically the Jurassic period. These volcanic deposits are largely welded tuff, intermingled with some lava flows, and occasionally interrupted by sandstone and conglomerate deposits. At that time, the area of Sonoita was part of what is known by geologists as the Mogollon Highlands; part of a subduction arc with volcanoes that erupted fairly regularly, back when Arizona was much closer to the coast. In essence, this part of Arizona looked very similar to the Andes during the Jurassic period, with tall, somewhat explosive stratovolcanoes that reached towards the skies. These rocks form much of the Canelo Hills. Some of these volcanic rocks are interspersed with wind-blown sandstone, possibly related to the vast sand ergs in the north which created the Navajo Sandstone.
Deposition continued into the early Cretaceous when the rock record denotes riverbeds leading to the nearby sea; massive conglomerates with rounded pebbles, interspersed with occasional volcanic rocks. In some parts of the region, some marine limestone can be found; indicating when an arm of the now Gulf of Mexico briefly intruded into the Southeastern part of the state. As far as I’m aware, the Cretaceous sedimentary rocks of Sonoita haven’t been explored for fossils, but in the nearby Whetstone mountains, remains of small titanosaur sauropods, such as Sonorasaurus, have been uncovered, along with petrified wood and fossil leaves, which indicates a forested environment; ginkgoes, cycads, and early flowering plants intermingled with conifers similar to sequoias. It is quite likely that this environment also covered the Sonoita region. Yes, that’s right, there were probably dinosaurs in Sonoita. These sedimentary rocks are then covered up by more volcanic rocks at the close of the Cretaceous and early Tertiary, as the volcanoes continued erupting at the close of the Laramide orogeny; some are effusive in nature (lavas, ash beds, and welded tuff), while others are intrusive (granite).
There is another gap in the rock record, and when they return, they are erosional deposits that mark the beginning of the basin and range faulting cycle which began to create the landscape which we see today in Southeastern Arizona; mountains and valleys filled with debris. These deposits consist of conglomerate, sandstone, mudstone, limestone, and rock-avalanche breccia, which were then uplifted, and faulted. As this faulting episode continued, creating the Basin and Range province, the nearby mountains rose, and the valleys dropped, between 16 million and 2 million years ago. These valleys began to fill with sediment, and in the Sonoita/Elgin area, these sediments include some limestones, intermingled with the standard conglomerates and sandstones, and most of the vineyards in the Sonoita and Elgin area are growing upon deposits of this age. (The major glaring exception is Charon vineyards, which are located in a deposit of granite dating from sometime during the Cretaceous.)
The close of the development of Sonoita geologically are alluvial fan deposits on the East side of the valley, and some continued deposition during the Holocene at the northern part of the Sonoita basin, which created final touches to the landscape in the Sonoita basin we see today.
Vines and mountains in Sonoita, at Hops N’ Vines
With this interesting geology, Sonoita is one of the most difficult regions for growing, due to the nature of soil conditions, despite being the oldest. To grow quality fruit in the Sonoita region, according to Mark Beres of Flying Leap, require serious knowledge of soil chemistry, and it has been a steep learning curve. The amount of calcium in the soils here is five times higher than that in the Kansas Settlement. Oftentimes, the correct acidification of irrigation water used for the vines is the key to success in the region (along with investments in soil amendments and wine nutrition), because the soils of Sonoita are quite high in bicarbonates. Furthermore, the groundwater here is low in boron and has a high carbonate content as well, thanks to the erosion of the nearby limestones into the valley below, and the deposits of limestone which have been laid down intermittently in the valley floor during the last 16 million years. This often means that the wines in Sonoita are generally a higher pH than anywhere in the state. This means that the wines of this region, and the terroir here, often is superficially similar to regions of Spain or Italy. While I need more experience with wines from Sonoita compared to other parts of the state, what I’ve generally noticed is that reds from Sonoita tend to have more hints of black pepper and Virginia pipe tobacco; whites have a sort of sandstone minerality, and hints of anise and orange zest. Both red and white wines here have hints of tangerine.
Wineries which are growing in the Sonoita/Elgin area include: AZ Hops N’ Vines, Rancho Rossa Vineyards, Callaghan Vineyards, Flying Leap Vineyards and Distillery, Hannah’s Hill, Lightning Ridge Cellars, Sonoita Vineyards, Dos Cabezas WineWorks, Willhelm Family Vineyards, Kief-Joshua vineyards, Charron Vineyards, the Village of Elgin Winery, and Silverstrike Winery. Canello Hills winery also used to be here. There are also a few other private vineyards as well.