It grows very slowly in clay, silt, loam, silty clay, sandy clay etc. Within this shale are several light gray, silty to clayey shale seams up to thick. Alkalinity problems are more pronounced in clay soils than in loamy, silty or sandy soils. Below the subsoil is a layer of mixed gravel and silty clay loam. It consists mainly of silty brown shale and fine-grained sandstone and siltstone. Black oak grows best on well drained, silty clay to loam soils. The neotropical loess is made of silt or silty clay. Groundwater occurs in silty to sandy layers of the alluvial sediments. Most fossils found are grey or yellow silty mudstone. The pampean loess is sandy or made of silty sand. Thick deposits of silty material resulting from deposition by aeolian processes are often called loess. Down cutting occurred, exposing previous layers, creating terraces that were covered with silty clay alluvium. It also contains important subsidiary elements of silty and argillaceous material. The sediment comprising some point bars might grade downstream into silty sediments. It is mainly applied to drill in sandy soil, clay, silty clay, etc.