Unlocking The Rocks

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CONTRIBUTION TO THE 2008 GREENOCK CREEK VINEYARDS AND CELLARS NEWSLETTER

by PHILIP WHITE – September 2008

Time for some rough science. While global warming is such a hot topic cough cough it seemed perfectly appropriate to take a little geology lesson: geology shows we’ve had global warming before. So, like, how bad can things get?

Before you check out Snowball Earth on Wikipedia, let me quote a report of Hoffman, Kaufman, Halverson and Schrag, suggesting one of the things that happened at the bottom of the Neoproterozoic groups which underly Greenock.

“… biological productivity in the surface ocean collapsed for millions of years. This collapse can be explained by a global glaciation (that is, a snowball Earth), which ended abruptly when subaerial volcanic outgassing raised atmospheric carbon dioxide to about 350 times the modern level….resulting in a warming of the snowball Earth to extreme greenhouse conditions. The transfer of atmospheric carbon dioxide to the ocean would result in the rapid precipitation of calcium carbonate in warm surface waters, producing the cap carbonate rocks observed globally.”

I’m sure they make a big difference, but there were no Hummers in those days.

It was also high time the Barossa seriously compared local wines according to their geological sites. But fearing that they may end up with a geology somehow less desirable than others, some vignerons have opposed such an approach for decades. Their excuse? They say they don’t want an appellation imposed like those of France. My response? It’s not a man-made imposition. It’s in the ground beneath you. It was there first.

So a highlight of my thirty years of wine writing finally exploded like a firework, when, in June, I was invited to assist the Barossa winemakers assemble a blind tasting of 52 unfinished 2008 shiraz wines from across the breadth and length of the Valley, from Lyndoch to Kalimna. These were tasted in brackets roughly according to their geological sources, as set out in The Geology of the Barossa Valley, a brochure and map by revered government geologist, W. A. Fairburn. This work, which has the authority of having been gnawed over by the author's scientific peers, is available from Primary Industry and Resources SA. We also had input from the contrary geologist-turned tea-trader turned wine-merchant turned wine-blogger David Farmer, who is writing a book on Barossa geology, and who disagrees with some of Fairburn's mapping.

The tasting was astonishing, while predictable enough. Neighbouring vineyards in each precinct offered flavours and aromas in common, and these characteristics changed from precinct to precinct. This pioneering tasting, conducted with thirty wine writers from around the world, will no doubt be the first of many such exercises, and marks the beginning of a whole new database of gastro-geology.

The base rocks around Seppeltsfield, the Greenock Creek homestead, and Roennfeldt Road are all from that Neoproterozoic, the geological era in which multi-cellular life first appeared. This era stretches from about 550 million years ago to 1.2 billion years. Just for reference, the Universe seems about 13 - 15 billion years old; Earth about 4.5 billion. While these old rocks are generally below the topsoil, they do extrude, and have of course influenced and added to the formation of much of that soil, which very directly influences the flavours of the grape.

But it’s those base rocks that really interest me, particularly when I read back labels and brochures claiming “our vines are grown in some of the oldest soils on Earth”. Most of the Barossa geology formed in the Tertiary and Quaternary, the last 50 million years; its soils are only tens of thousands of years old: most of them are such recent alluviums they’re barely soils at all. “To the geologist, soil is the dandruff of the Earth”, my friend Wolfgang Preiss, Chief Geologist of the Geological Survey in PIRSA, sagely uttered on a recent field trip.

The Greenock Creek vineyards are on four quite distinct formations. The creeklines, both at the homestead and Roennfeldt’s, are very recent alluviums, just tens of thousands of years old. The cabernet, the Creek Block shiraz, and most of the Apricot Block are in such alluviums. These deposits fill the creeklines between the sharply-dipping older strata which protrude in the ridges.

These include the blue-grey dolomitic siltstones - Willunga slate, for example - of the Tapley Hill Formation, deposited as sediments in still deep lakes that once covered the area about 750 million years ago. The Seven Acre and part of the home blocks are in this formation.

Below that lies the Yudnamutana Subgroup. This dark mix of siltstone-derived soil with blotches of bright quartzite and pebbly dolomite is up to 800 million years of age. These layers reappear in Clare and the Adnyamathanha country of the North Flinders. They are pocked with dropstones, which were deposited by floating glacial ice floes. These rocks were one of the fascinations of the great geologist and explorer, Sir Douglas Mawson. Alice’s and part of the Apricot Block are in Yudnamutana.

The Hopeless Hill, on Roennfeldt’s, is on the border of the Yudnamutana and the underlying Burra Group, where we get to really ancient glittery micaceous schists, metasiltstones, calcsilicates and quartzites. These are as old as it gets in the Barossa. The Roennfeldt shiraz, cabernet and the Cornerstone Grenache are in Upper Burra.

In geology, there are many arguments. But having finally got this sorted better than ever before, I’ll never approach Greenock Creek wines in the same way. The distinguishing characters of each vineyard already make much more sense, and the differences between the Greenock Creek/Marananga/Seppeltsfield/Roennfeldt vineyards and the much younger formations in the rest of the Valley become even more meaningful.

So that’s the ancient history. Contemporary history includes the salination, through introduced irrigation water, of the young creekline sediments and clays. And, of course, it includes current weather and climate. People are finally beginning to understand my salination theories. Now, the pace at which the climate is changing must force closer investigation, much quicker than anybody has imagined necessary. If, in a couple of decades, man can change the soil sufficiently to kill a vineyard, like the poor old Creek Block, never irrigated, but dying through salination from upstream irrigators, we can surely bugger up our air.

Or maybe old Mother Earth will just carry on doing what she did before. Now and again, as geology shows, something makes her lose her cool.

PS.

Just to put all this perspective, Don Francis, professor of geology at McGill University in Montreal, has since reported in Science journal that his team has found a sample of Nuvvuagittuq greenstone on Hudson Bay that they believe is 250 million years older than any other rocks known.

"The rocks contain a very special chemical signature - one that can only be found in rocks which are very, very old," he said. "Originally, we thought they were maybe 3.8 billion years old. Now we have pushed the Earth's crust back by hundreds of millions of years. That's why everyone is so excited."

Before this study, the oldest whole rocks were from a 4.03 billion-year-old body known as the Acasta Gneiss, in Canada's Northwest Territories, and the oldest Australia had to offer were 4.36 billion years old mineral grains called zircons from Western Australia.

The greenstone contains fine ribbon-like bands of alternating magnetite and quartz, typical of rock precipitated in deep sea hydrothermal vents - which have been touted as potential habitats for early life on Earth.

"These ribbons could imply that 4.3 billion years ago, Earth had an ocean, with hydrothermal circulation," said Francis. "Now, some people believe that to make precipitation work, you also need bacteria. If that were true, then this would be the oldest evidence of life. But if I were to say that, people would yell and scream and say that there is no hard evidence."

(This additional information was taken from http://news.bbc.co.uk/2/hi/science/nature/7639024.stm )

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Tasting the dirt

by PHILIP WHITE - This was first published in The Independent Weekly in May 2008

Now that the vintage Band-aids are coming off, it was a great treat last week to taste a sweeping selection of the Barossa’s 2008 shiraz. All were single-barrel samples, so anything could happen on the blender’s bench between now and the bottle.

I say Band-aids, because never before have I witnessed so many industrial accidents during a vintage. Knuckles, fingertips, toes, feet, noggins - all bore the brunt of humans working utterly ridiculous hours under totally unfair pressure in close proximity to great big things made from steel, many of which move.

But the Band-aids are coming off the wines, too: it’s now much easier to see the true nature of these woody babies. And while this tasting did NOT include much wine picked after the arrival of the worst heat wave on record, it certainly included fifty or so of the best of those picked in the sublime cool before that heat, and they’re very good.

The tasting was also a ground-breaker in that we poured the wines in groups according to their geological sources. I’ve gone on a lot lately about geology, but suddenly, in the local haute couture of wine, geology is the New Black. Even James Halliday was quoting what sounded like precise geological ages, reporting Brian Croser’s wines in The Weekend Australian last Saturday.

There’d been constant opposition to organizing a Barossa tasting on geological bases since I first suggested it in 1983. People thought it would become an appellation which they did not want; others obviously would do anything to avoid discovering that their geology wasn’t everybody’s favourite. My response has always been to suggest that this delineation is not a man-made imposition or regulation, because it is, very simply, already in the ground. It is there. Why not consider it? That’s what we did at Yalumba last week, and I don’t think things will ever be the same.

To those who are reluctant to admit to a direct influence on wine flavour from geology, which includes soils, subsoils, bedrock and whatever, I suggest they mount a similar tasting and look for the taste of salt. Salt is, of course, just one of the many compounds which come from geology, and, through the roots of the plant, very directly influences the flavour of the wine. Each year, more and more of the vineyards along the Barossa’s creek lines produce salty flavours.

This happens, too, in Clare, Padthaway, McLaren Vale, Langhorne Creek and just about everywhere. Australia is, after all, mainly comprised of ancient sea beds. It’s full of salt.

Just as wine is eighty per cent water. And water is, as John Gilbert wisely pointed out last week, “the ultimate solvent”. This becomes sap, which becomes juice. Then, apart from all the glycerols, fragrances, polyalcohols and other alcohols, on top of the thirty or forty organic acids in wine, as well as all the nitrogenous stuff, like the amino acids, apart from all the polyphenols and tannins, the pigments and vitamins, come the mineral salts of chlorides, phosphates and sulphates, locked onto calcium, magnesium, potassium, and sodium – all through the water, the sap – before you begin thinking about the trace elements: fluorine, boron, iodine, silicon, zinc, iron, manganese and what not.

So as we tasted our way through, and across, the Barossa’s natural history, we discovered little glimpses of this pretty flavour and that common to certain sub-regions. This infernally complex wave of new knowledge will snowball as more such tastings produce more intelligence, eventually making it much easier for blenders to produce better wine, and much easier for those single-vineyard producers with truly unique geology to win praise for their distinction.

Call such a technology an appellation if you will, but at least realise that it’s coming up from beneath. It was here first.

And if we’re really about to tackle the very best of France and the Old World, instead of drowning in the sickening downward gurgle of the discount gutter, we shall have to very quickly learn about our geology, just as the French have learned theirs for many centuries, and have regulated their plantings accordingly.

There will be many spats. Former geologist and tea and liquor merchant, David Farmer, is obviously exciting some Barossa winemakers with his theorizing, and he seems keen to prove the map I promoted here last week, W. A. Fairburn’s learned work from PIRSA, is wrong, which brings the Coonawarra boundary dispute to mind, but, you know, oh well. Get published; get it all approved by your peers, and on we’ll go.

The day after this tasting, I was greatly pleasured to taste the 2008 barrels of Greenock Creek Vineyards and Cellars according to the various local geologies, and suggest they are the most profoundly stimulating wines I have seen yet from 2008. Not the slightest hint of Band-aid.