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Hopanoid breakdown products (HBPs) and their influence on tetra- and tricyclic terpane (cheilanthane) oil-source rock parameters

Created 19/11/2025

Updated 10/01/2026

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Tricyclic and tetracyclic terpane ratios are used as biomarker proxies for depositional environments and to classify crude oils and source rocks. However, the biological precursors and diagenetic drivers of these proxies are not well understood. This study reports on the discovery of tricyclic and tetracyclic breakdown products of pentacyclic hopanoids that co-elute with 14α-C19 and βα-C20–C22 cheilanthanes and C24 tetracyclic terpane in gas chromatograms. This includes hopanoid breakdown products (HBPs) that are identical to 14α-C19 cheilanthane and C24 tetracyclic terpane, biomarkers that are commonly used as indicators of terrigenous organic matter in source rocks and their derived hydrocarbon products. These HBPs were generated by pyrolysis of C30 diplopterol, a common compound found in the cell membranes of almost all hopanoid-producing bacteria, some lichens and higher plants. HBPs are common in rock-extracted bitumens and crude oils from the Neoproterozoic to the Cenozoic and across a wide range of thermal maturities. Comparison of the relative abundance of HBPs and cheilanthanes against commonly used tricyclic and tetracyclic terpane parameters shows that HBPs can drive or strongly influence terpane-based paleoenvironmental proxies. This study begins to rationalise why some of these parameters indicate specific depositional environments and proposes new ratios that quantify the impact of HBPs on biomarker proxies.

Citation: Liyanage, T., van Maldegem, L.M., Hope, J., Schaeffer, P., Adam, P., Nytoft, H.P., Edwards, D. & Brocks, J., 2025. Hopanoid breakdown products (HBPs) and their influence on tetracyclic and tricyclic terpane (cheilanthane) oil-source rock parameters, Organic Geochemistry, 210, 105085. https://doi.org/10.1016/j.orggeochem.2025.105085

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Field Value
Title Hopanoid breakdown products (HBPs) and their influence on tetra- and tricyclic terpane (cheilanthane) oil-source rock parameters
Language eng
Licence Not Specified
Landing Page https://data.gov.au/data/en/dataset/46fed849-7a4a-43bc-aa8a-2550dda5405d
Contact Point
Geoscience Australia Data
clientservices@ga.gov.au
Reference Period 10/12/2025
Geospatial Coverage
Map data © OpenStreetMap contributors
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Data Portal Geoscience Australia

Data Source

This dataset was originally found on Geoscience Australia "Hopanoid breakdown products (HBPs) and their influence on tetra- and tricyclic terpane (cheilanthane) oil-source rock parameters". Please visit the source to access the original metadata of the dataset:
https://ecat.ga.gov.au/geonetwork/srv/eng/csw/dataset/hopanoid-breakdown-products-hbps-and-their-influence-on-tetra-and-tricyclic-terpane-cheilanthan