Changes

==Anomalies and lateral migration==

==Anomalies and lateral migration==

If the structural or geologic setting of the area suggests that microseepage may be predominantly lateral or pathway selective, such as along dipping stratigraphic surfaces and unconformities, the interpretation will be more difficult since geochemical anomalies may then not be located vertically above a trap. Which of these migration scenarios is more likely in your area of investigation? What is the relationship of the anomalies to outcrop geology, mapped structural closures, stratigraphic pinch-outs, faults, or basement highs? Because relationships between surface geochemical anomalies and subsurface accumulations can be complex, proper interpretation requires integration of surface geochemical data with geologic, geophysical, and hydrologic data. The importance of such integration cannot be overstated.<ref name=ch18r46>Thrasher, J., A., Fleet, A., J., Hay, S., J., Hovland, M., Duppenbecker, S., 1996b, [http://archives.datapages.com/data/specpubs/memoir66/17/0223.htm Understanding geology as the key to using seepage in exploration: the spectrum of seepage styles], in Schumacher, D., Abrams, M., A., eds., Hydrocarbon Migration and Its Near-Surface Expression: [http://store.aapg.org/detail.aspx?id=75 AAPG Memoir 66], p. 223–241</ref>

If the structural or geologic setting of the area suggests that microseepage may be predominantly lateral or pathway selective, such as along dipping stratigraphic surfaces and unconformities, the interpretation will be more difficult since geochemical anomalies may then not be located vertically above a trap. Which of these migration scenarios is more likely in your area of investigation? What is the relationship of the anomalies to outcrop geology, mapped structural closures, stratigraphic pinch-outs, faults, or basement highs? Because relationships between surface geochemical anomalies and subsurface accumulations can be complex, proper interpretation requires integration of surface geochemical data with geologic, geophysical, and hydrologic data. The importance of such integration cannot be overstated.<ref name=ch18r46>Thrasher, J., A., Fleet, A., J., Hay, S., J., Hovland, M., Duppenbecker, S., 1996, [http://archives.datapages.com/data/specpubs/memoir66/17/0223.htm Understanding geology as the key to using seepage in exploration: the spectrum of seepage styles], in Schumacher, D., Abrams, M., A., eds., Hydrocarbon Migration and Its Near-Surface Expression: [http://store.aapg.org/detail.aspx?id=75 AAPG Memoir 66], p. 223–241</ref>

==Hydrocarbon composition from macroseeps==

==Hydrocarbon composition from macroseeps==