I am not sure I follow your question, geologically related or from geochemistry perspective? Do you mean to characterize the biomarkers from the rock extract itself? Samples can be from outcrops, cuttings, SWC or core. It is advisable to go through screening evaluation first such as TOC, RE pyrolysis, Vitrinite Reflectance (vitrinite-like or graptolites) and Kerogen Typing analysis. Through the result you can then determine whether your sample met the organic content minimum requirement to proceed further analysis of GC, GCMS, MS-MS and stable carbon isotope of aromatic and saturate fractions. From these analysis you will obtain variety of biomarkers characterizing your sample, including the age-related biomarker of Pre-Cambrian. I hope this help.

Of course, from the kerogen (immobile) phase as long as no obvious mistakes are made. Nothing is 100% since human errors arise but this is by far the best bet.

for perspective, they were arguing about extractable biomarkers from Archean rocks for 15 years. The HyPy of kerogen couldn’t find any hopanes or steranes about 12 years ago.

inner versus outer bitumeno’s comparisons are unreliable in many cases...and lead to cherry picking of data. As we have seen.

gordon

First step, i) pick out rocks of suitable thermal maturity (preferably prior to peak oil window-maturity) as gauged from HAWK pyrolysis or elemental analysis screening, ii) use proven analytical methodology with full procedural blanks on a series of samples (depth series from core or outcrop), iii) use a combination of bitumen and kerogen analyses, iv) make sure the molecular distributions are self-consistent with i), ii) and iii).