The Regional Setting
Marlborough is the most exciting new wine region developed in the last three decades anywhere in the world. Over 50% of New Zealand wine is now produced in Marlborough.
The landscape is similar to other New Zealand wine areas with a valley made up of a sequence of stranded river terraces which step down to the Wairau River. It is on these terraces which have two distinct ages; 14,000 years and younger, and 14,000 years to 24,000 years, that most of the vineyards are planted. These are called here the younger and older terraces.
The Wairau River valley extends west south west from Cloudy Bay for well over 75 kilometres narrowing steadily and follows an important fault line, the Alpine fault which cuts through much of the South Island. This is a very active fault that slides from left and right (termed a strike slip) and on average moves about 3-4 mm/year although this happens in sudden jolts.
Towards it outfall the Wairau Valley is about 12 kilometres wide. The widest part which is favoured for vines extends south westerly for about 25 kilometres from Cloudy Bay and for most of this distance is some 10 kilometres in width. Currently the Wairau River hugs the northern edge of the valley. The younger terrace north of the Wairau River is in places wide enough for vineyards.
Significant rivers and creeks drain into this valley from the southern side and two are of importance; the Waihopai River and the Omaka River and their associated valleys. Both of these valleys and other smaller stream valleys are planted with vines.
The Waihopai River and the Omaka River meet on the Wairau River plain near the town of Renwick to form the Opawa River which remarkably does not flow into the Wairau River. This is recent and the current pattern of these three rivers is an excellent illustration of how streams swing, back and forth, over the surface of a valley; depositing sediment and eroding and sorting sediments in a process that is repeated and repeated.
The Wairau Valley sediments cover a size range from large oval cobbles up to 20cm across down to fine rock flour and all of these sizes are mixed together with little apparent sorting by grain size. This lack of regular banding or bedding is typical of sediments that are deposited quickly. Water action normally separates the coarser from the finer fractions which are often deposited in different layers.
Compared to the more southerly vineyards areas such as in Otago, the Marlborough vineyard sediments are further from the mostly glacial source of the sediments. Because the sediments have travelled further the flowing water has more of a chance to grade the sediments despite them looking unsorted. This grading could affect grape flavours by altering the water retention properties of the sediments and thus the way the vine takes up water.
The landscape changes south of the town of Blenheim, and continues along the fringing hilly slopes going west and up into the Waihopai Valley, a distance of some 30 kilometres. Many of the bed rocks here are older than the two terraces referred to and in particular a pronounced series of rolling hills that trend north east are made of a rock produced by the uplift and erosion of the Southern Alps about 2.0-1.8 million years ago (note: there is some confusion over the age of these sediments and parts may be younger). This surface was quite widespread over a large part of the northern end of the south island and is now preserved in a few areas mostly around Nelson.
This 'southern edge' is a most interesting viticultural region with many new plantings. Most of the vineyards are on the younger and older, flat, river terraces of the Wairau Valley, although not necessarily deposited by that river, while the newer plantings along the southern edge are pushing up the slopes of the more gentle hills. Perhaps the grapes from these plantings will express different flavours?
Geologically this region is also exciting as there are older river terraces preserved from 24,000 years to 300,000 years old plus outwash fans and even landslide deposits. These and the much older surface previously referred to and now exposed as rolling hills, termed the Hillersden Gravel, have been exposed by repeated minor faulting. This parallel faulting pattern has exposed a wonderful melange of soft rock and soil types and a wide variety of slopes and facings, many ideal for vineyards. Let’s hope vignerons can make the most of this. The sudden bedrock changes in this region remind me of how faulting has bought to the surface in Alsace a wonderful array of rock types that may influence the variety of wine types.
The Various Vineyard Settings
To understand Marlborough it is divided into four vineyard landscapes.
The main plantings are on the younger and older terrace sediments which are largely flat lying and are confined to the Wairu Valley. These two terraces are sufficiently different to be separated into two landscape surfaces.
Fringing the valley on the southern side, from south of Blenheim and up the arms of major rivers, the Waihopi and Omaka, and other streams, vineyards are planted on the older terrace. It is likely that the climate along the major river valleys of the Waihopi and Omaka are sufficiently different to the Wairau Valley to warrant at least these regions being seen as a separate landscape. These vineyards are also flat lying though in places sufficient erosion has taken place for some vineyards to show relief.
And lastly the southern fringing area contains many remnant pockets of older river sediments from 24,000 years to 300,000 years and importantly, rolling hills of a much older rock, approximately 2.0-1.8 million years, termed the Hillersden Gravel. This is a poorly consolidated gravely, sandy, silty rock the erosion of which will have contributed some of the sediments to the younger alluvial terraces. Vineyards are planted on a wide variety of different land surfaces many with pronounced slopes and these are sufficiently different to the flat lying terraces to be called a different landscape.
The Younger Terrace - Younger than 14,000 years
Vines are planted on the younger terrace both north and south of the Wairau River. Compared with the older terrace the cobble beds look more uniform in their sorting with a smaller fraction of fine material. This may well affect grape flavours principally in the way in which the vine can access water especially in hot periods. There are a number of vineyards on terraces north of the river though the bulk of plantings lie on the south side. The sediments east of the road leading north to Picton from Blenheim towards Cloudy Bay were only briefly looked at though it would be surprising, being near the ocean outfall, if they did not show a different sediment grading to those further up-river.
The Older Terrace - 14,000 to 24,000 years
Large areas of the older terrace are covered with fine pale sediment which being younger represents a change from the fast flowing stream that deposited the underlying unsorted cobble beds to a gentler depositional stage. This fine sediment varies rapidly in thickness across vineyards. These sediments are presumably water borne and were separated from coarser sediments upstream. They may also be partly or largely windblown. Time did not allow the distinction to be made.
This surface layer and the wide variety and unsorted, jumbled nature of the coarse, pebbly, underlying sediments make this terrace different to the younger terrace.
In some seasons it is likely that the water uptake from these sediments will differ from the younger terrace because of the larger percentage of finer particle fractions. Also, where the fine surface sediment is thick will have a marked effect on the vines growth.
The Older Terrace - 14,000 to 24,000 years along the Steams That Flow from the South West
A distinction is made between the older terrace associated with the Wairu River and the older terrace that fringes the Waihopai River and the Omaka River and the five or six smaller streams that drain north east off the mountains along the southern edge of the Wairau Valley.
It is not immediately clear though how much of the older terrace was deposited by the Wairu River and how much by the steams flowing from the south-west. It may not make a great difference to how vines grow but sediment from the two sources will have some differences, hence the reason to treat this area separately. Also the protected nature of the valleys will affect the climate influence and should alter ever so slightly how the vines grow.
Most of these vineyards are flat lying although some are on rolling surfaces.
The Sloping Southern Fringe and Older Sediments
South of Blenheim and Renwick recent faulting and erosion has created a series of generally north-east trending hills that has exposed the Hillersden Gravel a land surface developed perhaps two million years ago. Rivers and streams, notably the Fairhall, Waihopai and the Omaka flow between these hills.
Along these valleys and up the gentler slopes vineyards are expanding into a most exciting viticultural region.
The Nearby Awatere Valley - South East of Marlborough
About 20 kilometres south east of Blenheim is the Awatere Valley and its associated river. This valley like the Wairau trends north east –south west. Time did not allow a detailed study of this valley but the same sediment groupings of younger and older terraces have been formed in a similar manner to Marlborough.
The sediments types and ages do though change more rapidly than in the Wairau Valley so a great diversity may underlie any vineyard. I often think this is a good thing for making interesting more complex wines. It must also be noted that the sediments in this valley are much thinner than in the Wairau.
Observations about Terroir from Visiting Marlborough
As a general comment the vineyard settings are all remarkably similar and should make similar wines. Some differences in the sediments and landscape have been noted though the overriding feeling you get about Marlborough is that the influence of flavour will be less the land and more the climate and different approaches to vineyard management and wine making. For example vineyards on the younger terrace level are only one step removed from hydroponic farming.
This is an area not about tiny differences in local terroirs (and what if any these have on wine tastes I have not decided) but about broad acre farming. The influences will be from the closeness to the ocean and the prevailing weather. It is the site of the whole region not the individual vineyards that are important. The individual differences that will occur will be more man made.
The surfaces that make this landscape are remarkably similar to that of much of Argentine but not of course with the altitude. Thinking about Marlborough and Argentine (Mendoza) makes a reflection back to Australia useful.
Marlborough and Mendoza are identified by a young landscape and soils, or really non soils, have been formed not by the physical and chemical degradation of underlying rock but by sediment that has been transported and was formed by the physical break-up of rock by glaciers. For a view on the viticultural landscape of Argentine go to Wine Notes from a Trip to Argentine
Most of the dry land vineyard landscapes in Australia are very old with many metres of degraded rock below the soils and from which in part the soils have developed.
What the vines are planted in could not be more dissimilar. Yet the tastes, making allowance for the latitude are not dissimilar giving a hint that the bedrock and soils and how they were formed has little direct effect the taste of the wine, and it is the general climatic setting and how water is made available to the plant that is of overriding importance.
Standing on the river terrace at the Seresin winery looking north east across the Wairau River valley. The river lies at the base of the distant range. The vineyards pictured are on sediments of the younger terrace.
Examining a cutting of the older river terrace near the Seresin winery on Bedford Road. This terrace is about four metres higher than the younger terrace which is cut by the Wairau River. Pale sediment from half to one metre deep overlies several metres of cobble and pebble river wash which is poorly sorted with little if any bedding. The fine grained, pale sediment is reworked river wash having been separated from the pebbles and cobbles upstream and deposited down stream. In places it shows a modest 'A' soil horizon. It may also be partly or largely wind blown sediment (loess) which is interspersed with the river wash. It is younger than the underlying pebbly terrace but associated with that depositional phase.
Vineyards in this large flat area west of Blenheim are planted in the fine, pale sediment or directly into the pebbly terrace of the older terrace. Many vineyards show a combination of both as the pale sediment varies rapidly in thickness.
The bank of Marchbur River which has sliced through the poorly graded older terrace sediments. This is a lovely cross section of the type of river wash making up the older terrace on which so many important vineyards are growing. This exposure is just to the east of the town of Wairau River and the vineyard areas are further east again.
A bank created by the Wairau River cutting through the younger terrace. The river swings back and forth across the terrace constantly eroding and redepositing sediment. You would need to see more exposures but the impression is that the younger terrace is more uniformly sorted than the older terrace. The grade of cobbles and pebbles is more uniform with fewer of them being odd shapes and less rounded, even angular, that you see in the older terrace. Also there are fewer small pebbles. There also appears to be a lower percentage of finer sediment and very fine rock flour filling the interstices between the rocks than the older terrace. This rock flour would be constantly disturbed and flushed out to sea and replaced by new sediment especially at times of low river flow.
It could be that the sediments of the older and younger terrace are sufficiently different to affect grape flavours principally through water uptake which would be noticeable in times of vine stress.
Many kilometres south west along the Waihopai River with the last vines well behind. A brilliant exposure showing the basement rocks unconformable overlain by older terrace sediments and fine pale river wash or possible wind blown loess soils.