Remarks on the Geology and Wines of McLaren Vale
Monday, 6th February, 2012
In August, 2010, a geological map of the McLaren Vale wine region was published. This is the final version of a preliminary map from 2000. I love maps and to me both are works of art though the full blown 2010 version is a thing of beauty. This map shows in great detail the many geological formations from very young to old which underlie this famous vineyard region.
Maps whether they are topographical or technical like a geological map impart information quickly and we know that the general reader also finds them very useful as the biggest selling wine books are wine atlases.
The idea of mapping the geology of the wine regions of South Australia dates back to the mid 1970s. Then a group at the South Australian Department of Mines and Energy in Adelaide, including the geologists William (Bill) Fairburn, Jeff Olliver and Wolfgang Priess and a geological survey employee Philip White*, tossed around the idea that a detailed knowledge of the geology would be helpful in understanding the wine regions.
Philip White, writing in August, 2010, remembers these discussions over lunch; "Supervisor of many of these was my boss, the legendary Bob Wildy. Red wine, and much of it, was compulsory. The regular comparison and discussion of wines from the various South Australian viticulture regions led invariably to posturings on their relative geology. But not very deeply."
To think that a group of people with geological knowledge were discussing concepts of wine and geology in Adelaide in the mid to late 1970s is quite remarkable and this is valuable information for future wine historians.
One of these geologists, Bill Fairburn was so intrigued by the idea that at some time in the late 1970s or possibly later, he went on a tour to study the geology of the French wine regions. Upon return Fairburn proposed that the department should properly map the wine regions of South Australia. This was not accepted though Fairburn at some future point began privately mapping McLaren Vale and the Barossa Valley.
Thus in 2000 what I gather was the private mapping of Fairburn, with support from the Geological Survey Branch, now incorporated into Primary Industries and Resources South Australia (PIRSA), was officially published as the Geology of the McLaren Vale Region, this being the map referred to earlier. My copy is not dated.
Around this time another map titled The Geology of the Barossa Valley was officially published with the assistance of PIRSA again based on the private mapping of Fairburn. The map and notes are more detailed than that of the McLaren Vale brochure and I assume are later. There is also a preliminary map titled, Geology of the Clare Valley Wine Region, also dating to this time.
We owe a great deal of thanks to Bill Fairburn for his years of toil and for bringing this information to publishable form and to Philip White for bringing the completed version of McLaren Vale to fruition in 2010.
There is now a large body of work about geology and soils and how these may relate to wine flavours. These ideas are explored on this site under Regional Studies and Terroir. There are many believers that the soils and geology have a large impact on wine flavours, indeed quite extravagant claims are made. The notes titled 'Terroir' accompanying the McLaren Vale 2010 map say; "Nevertheless, McLaren Vale wines from similar terranes are expected to have distinctive characteristics as demonstrated in the Barossa Valley, 50km northeast of Adelaide, during wine tastings in 2008." This tasting demonstrated no such thing.
Geology Soils and Climate
My own adventures in mapping wine regions, which I refer to as landscape mapping, began in the late 1990s and lead to the publication of 'The Red Soils of Coonawarra' in 2002. I have continued to explore the wine regions of Australia and have spent a lot of time in the Limestone Coast in the south-east corner of South Australia and have almost completed my own version of the landscape of the Barossa Valley, this being quite different to a geological map. I have also spent time in the Murray-Darling Basin, the Clare Valley, McLaren Vale, Eden Valley and the Adelaide Hills, Langhorne Creek, the Hunter Valley, the major regions of W.A. and further afield in New Zealand, Argentine and Chile all the while asking 'what is it that really drives the diversity of wine flavours'.
Having a geological background I thought that detailed mapping of soils and the aspect and origin of the landscape surface may produce some ideas and I proceeded along this line. Even so I did accept that the major impact on flavour was the climate and this has been well known for thousands of years; after all there are good and bad seasons and more recently the difference in flavour of wines from cool and warm climates are most obvious. What myself and others were doing was looking for reasons to explain localised and subtle taste shifts. Who knew, perhaps the answer was in the soil?
The more I observed, the more I agreed with the views of those, such as Gladstone's, that the great generator of wine flavour was climate. I now think it is how the vine gets its supply of water, and what is dissolved in it, to be the only impact that the soil, rotten rock and the aspect of the landscape have on wine flavours.
And of course it will be in the detail of daily weather changes where the answers will be found. It is not hard to imagine that as data is gathered about daily and hourly climate shifts produced for example by cooling winds from a nearby ocean; the diurnal temperature range; affects of cloud cover, humidity and dozens of other subtle temperature changes that these alone can account for all of the myriad subtleties in wine flavour.
While we can often taste these differences, it will be left to scientists to prove that the taste change is due to a build-up of particular flavour molecules which are favoured by these climate-temperature shifts. Likewise flavour molecules may also be destroyed or changed under these climate conditions.
So while I applaud the publication of the Geology of the McLaren Vale Wine Region and I'm sure it will give many readers much pleasure it cannot tell us anything about the wine flavours of the region. The spread of rotten rock and soil that cloaks the geology in which the vines grow also shows great diversity but again will have no direct bearing on flavours, if these are defined as flavour molecules that are developed because the vine has access to some compound not found elsewhere. For those who dispute this, the final say will of course rest with scientists who will have to prove if it is true or not, and they will do this by linking a flavour compound back to a sub-surface origin.
The Flavours of McLaren Vale
With that said, it may well be, and perhaps is likely, that some vines will grow better in some soils than others and perhaps a more vigorous vine or less vigorous vine fruits in a manner that alters grape flavours.
The major influence then on the wine flavours of McLaren Vale, or at least that part that is brought to the winery by the grapes, will be the interplay between the prevailing climate moving in from the Southern Ocean and over the waters of the Gulf, and the heat of the continent.
McLaren Vale also rests in an unusual embayment created by the Wilunga fault which allows for numerous micro climates which vary between those vineyards close to the ocean and those jammed into the far north-east corner of Blewitt Springs-Clarendon.
Indeed this part of the coastline has four similar embayment's; McLaren Vale, Reynella, Adelaide and further north, the plains of Angle Vale. Regrettable that our chances of studying the differences of the southern three is lost due to urban sprawl consuming the vineyards of Adelaide and Reynella and its probably agreed by most winemakers that the Angle Vale plains are simply too warm for fine wine.
* Philip White after leaving his job as a geological assistant went on to a career as a free lance writer, including a 20 year stint as the wine writer for the Advertiser in Adelaide and is well known in wine circles for his essays on wine. We interviewed Philip at A Lunch with Philip White . You can read White's articles about the geology of McLaren Vale by going to his site, Drinkster, where they are archived in August 2010.