Lagerdensitet

Lagerdensitet is a term used in geology and materials science to describe the density of a defined layer or stratum. It represents how much mass is present in a given volume of that layer, and is typically expressed in kilograms per cubic meter (kg/m^3) or grams per cubic centimeter (g/cm^3). In geological contexts the value often reflects the combined influence of mineralogy and porosity; the bulk density of a layer depends on both the density of the solid grains (grain density) and the amount and characteristics of pore space that may be filled with air or fluids.

Measurement methods include laboratory and field approaches. In the lab, bulk density is determined by weighing a rock or soil sample and measuring its volume, frequently using water displacement or pycnometry. In the field, downhole density logging (using gamma-gamma or neutron–density tools) provides in-situ estimates of formation density, which are crucial for interpreting subsurface stratigraphy and rock properties.

Factors affecting lagerdensitet include mineral composition, cementation, compaction, porosity, and fluid saturation. Denser minerals (such as dense oxides or sulfides) raise the density, while higher porosity or fluids within the pores lower the bulk density. The concept is important in seismic interpretation, hydrogeology, petroleum geology, and geotechnical engineering, where density contrasts help identify layer boundaries, aquifers, and reservoir zones.

Typical values vary widely by rock type. Unconsolidated sediments might range around 1.5–2.0 g/cm^3, sandstone around 2.2–2.6 g/cm^3, limestone about 2.3 g/cm^3, shale near 2.4 g/cm^3, and dense igneous rocks like granite or basalt often exceed 2.6–3.0 g/cm^3.