Coonawarra origins — not long above sea level

Coonawarra is, of course, Australia’s most-famous patch of cabernet growing dirt and a recent Chateau Shanahan tasting, though far from definitive, gave the region a healthy score card. But it wasn’t thumbs up for all of the wines tasted and, as well, several otherwise appealing drops suffered from over-oaking — a scourge that won’t quite die in Australia.

But before we look at the wines, let’s look at the region. Coonawarra lies about 400 kilometres south of Adelaide on what is now called the Limestone Coast – for good reason – though most South Australians still know it as the ‘south east’.

They’re lucky to have the Limestone Coast in South Australia at all. It could well be Victoria’s ‘far west’, as a glance at the map (or Google earth) shows.

This fertile strip of land is physically separated from South Australia as it lies entirely south of the Murray (if we include Lake Alexandrina as part of the Murray) and is separated from Victoria by nothing more than a line drawn on the map – the western boundary being the sea.

Coonawarra can only be understood in the context of this vast and comparatively recent limestone formation – Coonawarra, for example, having been above the sea for only about seven hundred thousand years.

A series of fossilised sand dunes between Coonawarra and the coast mark former shorelines as the sea retreated in glacial periods and advanced as the climate warmed. But as the land continued to rise, the shorelines shifted steadily to the west.

It seems that what we know as Coonawarra today was once an inter-dunal lagoon, perhaps similar to today’s Coorong, just an hour’s drive northwest.

These recent marine origins explain the presence of limestone beneath the generally shallow topsoils of the region. And these topsoils appear to be derived largely from that limestone bedrock.

Driving through Coonawarra you might say that it’s flat and featureless. But with the water table so close to the surface, variations of only a few metres in elevation make significant differences to land usage – especially to suitability for grape growing.

This would have been quickly apparent to Coonawarra’s early settlers before today’s drainage canals had been excavated or large-scale irrigation had affected the water table.

When John Riddoch established the Coonawarra Fruit Colony in the late nineteenth century – and this was the forerunner of the wine industry – the lower lying parts would’ve been inundated in winter and the main north-south road, around which today’s vineyards are concentrated, almost certainly marked the highest, driest tract of land.

Long before Europeans carved the road, this perennial elevated strip of land would’ve been dry and exposed to the air far more than the seasonally inundated land around it.

Over time this exposure led to the oxidation of the iron content from black ferric oxide to red ferrous oxide – giving Coonawarra’s central strip it’s famous russet colour, known as terra rossa – quite literally ‘red earth’. The surrounding soils remained black and are still subject to flooding.

The early fruit growers discovered that the comparatively well-drained red soils proved more productive than the black soils. As winemaking became the mainstay towards the latter half of the twentieth century, these red soils remained the favoured sites for grape growing, too.

Then, in the early nineties, Australia negotiated a treaty with Europe in which we recognised each other’s wine regions. The problem for Australia was that we had no formal boundaries that could be recognised.

From this grew our Geographic Indications (GI) system under which we defined and recognised in law our wine zones and regions. Thus, the Coonawarra Region became one of several regions within the Limestone Coast Zone.

The at times bitter wrangling over what was and wasn’t in Coonawarra led to the declaration of an area far larger than the popular notion of Coonawarra’s long red strip of terra rossa.

The original twenty-kilometre long cigar-shaped strip might now constitute perhaps five per cent of the declared area.

Admittedly, only a small portion of that is planted to vines. But modern Coonawarra unquestionably has unproven broad acres of land well beyond the original strip. Some of this may prove to be outstanding. But much of it may also be quite ordinary – especially if an end to the long dry floods some of the new plantings.

The recent tasting at Chateau Shanahan is just one of several planned for the next few months – including a look a the much-hyped 1998s – in an attempt to see who and what’s in form in Coonawarra.

We’ll be following this up with a field trip next January to see what’s really happening on the ground and which wines are really worthy of carrying the Coonawarra name.

Copyright © Chris Shanahan