The influence of tertiary and quaternary deposits on the viticultural potential of the terroirs to be found in Geneva, Switzerland

The 1365 ha of the Genevese vineyard are located at the south-western corner of the Swiss plateau, between 395m and 505 m altitude. The vineyard is spread on quaternary deposits left behind after the melting of glaciers (12000 years BP) and tertiary molassic rocks (Chattien, 24 Ma). A soil map on the scale of 1:7500 was produced from 850 auger probes and 90 soil profiles. Based on this map, 69 parcels of Gamaret and Gamay are used as indicators to study the meso-climate and to follow the vines’ development. Thirty-seven parcels are equipped with temperature sensors at the depths of 2, 10 and 50 cm.
The glacial deposits are either made up of basal tills, mostly compacted, or by lateral and frontal stony tills more or less compacted or by glacio-lacustral and fluviatil deposits which show a textural composition going from clay to coarse gravel. The tertiary rocks present a succession of mudstone and sandstone stratas. The presence of these different deposits means there is great spatial variability. The textural and spatial variability are therefore present in the soils which developed from these parent materials.
More than half of the soils (55%) are located on basal or lateral tills. The glacio-lacustres and the tertiary rocks are to be found under 21 and 26 % of the soils respectively. Seven percent is situated on molasse with shallow till deposit. The CALCOSOLS, BRUNISOLS and LUVISOLS cover 63, 21 and 8 % of the surface respectively. Their clay, calcite and stone content differs widely. The deposits also influence the soils’ thermal and hydrological properties. The soils with excess of water are mostly located on fine textural deposits like mudstone and glacio-lacustral clay and on compacted tills The available water content goes from 50 to 250 mm. The plant behaviour is being observed in an on-going study to better under stand the meso-climate of the vineyard.