Density Mass per unit volume, expressed in grams per cubic centimeter. Rock or formation densities are usually measured as either saturated bulk densities or grain densities. For gravity interpretation, the contrasts between rock bulk densities are of primary interest since these contrasts are responsible for the anomalous gravity field. Rock bulk densities have been shown to vary as a function of geologic age, lithology and depth of burial. The density of one rock unit relative to another.
Density contrasts can be either positive or negative.
The relationship between the change in density with a change in depth. In many areas of the world with thick clastic sections the increase in density with an increase in depth has been shown to be primarily a function of compaction. However, age, lithology and porosity may also influence the relationship. The relationship is important in gravity modeling because a gravity anomaly may be caused by a gradational change in density rather than a relatively abrupt density contrast , such as that which may occur at a fault, contact, or unconformity. A model of the geology in which layers or bodies of given lithologies are replaced by equi-density layers or bodies.