Hiekkakerroksilla

Hiekkakerroksilla is a Finnish term meaning “on sand layers” or “in sand layers.” In a geological context it refers to sedimentary sequences where sand is the dominant material, often used to describe a specific stratigraphic interval within a borehole, outcrop, or sedimentary basin. The phrase may also appear in field descriptions to indicate the location of samples or features relative to sandy units.

Formation and characteristics

Sand layers form through deposition by water or wind. In aqueous environments, they accumulate from rivers, deltas, beaches, or continental shelves, while aeolian (wind-blown) processes create dune and dune-field deposits. Typical sand grains measure roughly 0.062 to 2 mm in diameter, and sand layers may show structures such as cross-bedding, ripple marks, and planar lamination. Over time, burial leads to compaction and, in some cases, cementation, producing a more consolidated sandstone. The color of sand layers can range from pale to reddish-brown, and their porosity and permeability commonly make them important as aquifers or reservoirs in subsurface geology.

Significance

Sand layers serve as key markers in stratigraphy, helping to interpret past environments, climate changes, and sediment supply. They can preserve paleogeographic information and are frequently used as references in groundwater studies, mineral exploration, and archaeological investigations. In Finland and other Nordic regions, sand layers are often linked to glaciofluvial processes, coastal sands, and esker systems.

Methods and study

Geologists study sand layers using field logging, grain-size analysis, sedimentary facies interpretation, and dating techniques such as luminescence or radiometric methods to establish age and depositional context.

See also: sedimentology, stratigraphy, sedimentary structures, groundwater geology, esker systems.