Changes

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! To increase confidence in your correlation …

! To increase confidence in your correlation … || Because …

! Because …

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| Measure as many different properties as possible

| Measure as many different properties as possible || All positive correlations are based on circumstantial evidence. Therefore, measuring more properties means acquiring more evidence.

| All positive correlations are based on circumstantial evidence. Therefore, measuring more properties means acquiring more evidence.

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| Use detailed molecular and isotopic comparisons (e.g., GC/MS or compound-specific isotope analyses)

| Use detailed molecular and isotopic comparisons (e.g., GC/MS or compound-specific isotope analyses) || Molecular and [[Wikipedia:Isotope geochemistry|isotopic techniques]] are very sensitive and provide much “fingerprint” detail about sample compositions.

| Molecular and [[Wikipedia:Isotope geochemistry|isotopic techniques]] are very sensitive and provide much “fingerprint” detail about sample compositions.

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| Analyze as many samples as possible

| Analyze as many samples as possible || A large number of samples provides background information on natural variation that could otherwise be confused with genetic differences.

| A large number of samples provides background information on natural variation that could otherwise be confused with genetic differences.

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| Use samples that have suffered as little postgenetic transformation as possible

| Use samples that have suffered as little postgenetic transformation as possible || Postgenetic transformations—especially [http://www.oiltracers.com/services/exploration-geochemistry/oil-biodegradation.aspx biodegradation], cracking, and [http://www.gazprominfo.com/terms/topping-gas/ gas stripping] of oils—can make positive correlations very difficult. Also, all oil–source rock correlations are complicated by the fact that significant compositional changes occur as the oil is expelled from the source rock and migrates.

| Postgenetic transformations—especially [http://www.oiltracers.com/services/exploration-geochemistry/oil-biodegradation.aspx biodegradation], cracking, and [http://www.gazprominfo.com/terms/topping-gas/ gas stripping] of oils—can make positive correlations very difficult. Also, all oil–source rock correlations are complicated by the fact that significant compositional changes occur as the oil is expelled from the source rock and migrates.

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| Use source rock samples that are mature, not postmature

| Use source rock samples that are mature, not post mature || Since many source rock samples are immature, a comparison with mature oils can be difficult—not only because physical appearances and molecular distributions are different, but also because extracts from immature rocks are sometimes genetically unrelated and compositionally dissimilar to mature extracts and oils.<ref name=ch08r26>Kohnen, M., E., L., Schouten, S., Sinninghe Damste, J., S., de Leeuw, J., W., Merrit, D., Hayes, J., M., 1992, The combined application of organic sulphur and isotope geochemistry to assess multiple sources of palaeobiochemicals with identical carbon skeletons: Organic Geochemistry, vol. 19, p. 403–419, DOI: 10.1016/0146-6380(92)90008-L.</ref>

| Since many source rock samples are immature, a comparison with mature oils can be difficult—not only because physical appearances and molecular distributions are different, but also because extracts from immature rocks are sometimes genetically unrelated and compositionally dissimilar to mature extracts and oils.<ref name=ch08r26>Kohnen, M., E., L., Schouten, S., Sinninghe Damste, J., S., de Leeuw, J., W., Merrit, D., Hayes, J., M., 1992, The combined application of organic sulphur and isotope geochemistry to assess multiple sources of palaeobiochemicals with identical carbon skeletons: Organic Geochemistry, vol. 19, p. 403–419, DOI: 10.1016/0146-6380(92)90008-L.</ref>

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