Preservation of biological markers in clasts within impact melt Breccias from the Haughton impact structure, Devon Island

Abstract The 39 ± 2 Ma Haughton impact structure on Devon Island comprises a thick target succession of sedimentary rocks, mainly carbonates. The carbonates contain pre-impact organic matter, including fossil biological markers. Haughton is located in an area where no major thermal event has affected the sedimentary succession after heating caused by impact. This makes Haughton uniquely suitable for studies concerning the preservation of fossil biological markers following an impact event. Melt breccia is the most common impactite at Haughton. It is composed of clasts of the target, mainly carbonates, embedded in a fine groundmass. The groundmass is composed of material that was melted during impact. In this study, fossil biological marker maturity parameters (tricyclic terpane-hopane ratio and pregnane-sterane ratio) and an aromatic maturity parameter [methylphenanthrene ratio (MPR)] were used to compare the degree of thermal alteration in different size fractions of carbonate clasts (<0.5–4 cm in diamet...