Changes

==Seeps==

==Seeps==

Oil and gas seeps, if present, are also valuable analogs because they permit direct correlation of seeping hydrocarbons with soil gas and fluorescence data as well as other microbial or geochemical data. Old producing fields may not provide good analogs since production and pressure decline may have reduced or even eliminated their surface geochemical expression.<ref name=ch18r15>Horvitz, L., 1969, Hydrocarbon prospecting after thirty years, in Heroy, W., B., ed., Unconventional Methods in Exploration for Petroleum and Natural Gas: Dallas, Southern Methodist Univ. Press, p. 205–218.</ref>

Oil and gas seeps, if present, are also valuable analogs because they permit direct correlation of seeping hydrocarbons with soil gas and fluorescence data as well as other microbial or geochemical data. Old producing fields may not provide good analogs since production and pressure decline may have reduced or even eliminated their surface geochemical expression.<ref name=ch18r15>Horvitz, L., 1969, Hydrocarbon prospecting after thirty years, in W. B. Heroy, ed., Unconventional Methods in Exploration for Petroleum and Natural Gas: Dallas, Southern Methodist Univ. Press, p. 205–218.</ref>

==Sample density==

==Sample density==