Agriculture Reference
In-Depth Information
Glacial gravel
Figure 1.6
Soil formed on a glacial
outwash deposit overlying older
weathering granite in the Cauquenas
region, Chile. The scale is 15 cm.
(White, 2003)
terraces. The finer sedimentary material is carried farthest from the river
before settling out, whereas the coarser sand particles (up to 2 mm diame-
ter), gravel (2 to 60 mm), stones and boulders (>60 mm) are deposited pro-
gressively nearer the river, usually forming terraces. Soils formed on better
drained alluvial deposits are used extensively for vineyards in the Riverina
region and Riverland-Sunraysia region, Australia. Examples of gravelly allu-
vial deposits under vineyards occur in of New Zealand's Hawke's Bay region,
as on the Gimblett Gravels, well known for Cabernet Sauvignon and Syrah
(Shiraz) wines, and the Marlborough region, renowned for its Sauvignon Blanc
(figure 1.7).
Soils on Sandstone
Sandstone, as the name implies, is made up of grains of sand comprising miner-
als such as quartz, feldspar, or simply rock fragments in the size range 0.06 to
2 mm. Classed as sedimentary rocks, formed by the consolidation of original
deposits of weathered materials moved by wind or water, sandstones generally
form soils of low fertility because of a paucity of weatherable minerals. When
sandstone has been weathering for a long time under rainfall >1,000 mm, deep
