Changes

==Rock densities==

==Rock densities==

The range of densities for all rock types (igneous, metamorphic, and sedimentary) is typically 1.60–3.20 g/cm³. The density values of sedimentary rocks typically range from 1.80 to 2.80 g/cm³. Thus, small variations of density in sedimentary rocks may be invisible to the method. A5–10% error in estimating subsurface densities from gravity is quite common. This is in contrast to [[magnetics]], where typically there are orders of magnitude variations in susceptibilities.

The range of densities for all rock types ([[igneous]], metamorphic, and sedimentary) is typically 1.60–3.20 g/cm³. The density values of sedimentary rocks typically range from 1.80 to 2.80 g/cm³. Thus, small variations of density in sedimentary rocks may be invisible to the method. A5–10% error in estimating subsurface densities from gravity is quite common. This is in contrast to [[magnetics]], where typically there are orders of magnitude variations in susceptibilities.

==Horizontal layers==

==Horizontal layers==

Horizontal layers have no anomalous gravity response. Thus, it is impossible to determine the subsurface density distribution if there are no lateral changes. Layer-cake geology yields no anomalous gravity signal. A bed is considered infinite and horizontal if it is about five times wider in all directions than it is thick, with no [[dip]].

Horizontal layers have no anomalous gravity response. Thus, it is impossible to determine the subsurface density distribution if there are no [[lateral]] changes. Layer-cake geology yields no anomalous gravity signal. A bed is considered infinite and horizontal if it is about five times wider in all directions than it is thick, with no [[dip]].

==Interpretation ranges==

==Interpretation ranges==

==Depth-to-basement determination==

==Depth-to-basement determination==

Gravity is not as good at depth-to-basement or depth-to-density anomaly estimations as other geophysical methods. Though possible to do, it is often difficult to determine the appropriate depth to geologic source unless other constraints exist.

Gravity is not as good at depth-to-basement or depth-to-density anomaly estimations as other [[geophysical methods]]. Though possible to do, it is often difficult to determine the appropriate depth to geologic source unless other constraints exist.

==Positions of geologic bodies==

==Positions of geologic bodies==

[[Category:Predicting the occurrence of oil and gas traps]]  

[[Category:Predicting the occurrence of oil and gas traps]]  

[[Category:Applying gravity in petroleum exploration]]

[[Category:Applying gravity in petroleum exploration]]