Biomarker signatures of Upper Cretaceous to Paleogene hydrocarbon source rocks from the Latrobe Group, Gippsland Basin

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Abstract

Gas chromatography-mass spectrometry analyses have been carried out to investigate the geochemical characteristics of the Latrobe Group shales and coaly shales from the Gippsland Basin, Australia. The depositional environment, source of organic matter and thermal maturity of hydrocarbon source rocks in the study area were evaluated using molecular biomarker analyses. The distribution of isoprenoid alkanes and pentacyclic triterpanes reveals an oxic environment with fresh water (pristane/phytane > 3.0, gammacerane index < 0.3). The carbon preference indices (CPI) and odd-to-even predominance ratios of the n-alkanes are higher than 1.0, suggesting terrigenous higher plant-derived organic matter in the sediments. The high predominance of C29 sterane over C27 sterane, as well as the occurrence of conifer and angiosperm biomarkers (e.g., labdane, isopimarane, phyllocladane, rimuane, oleanane, retene, anthracene, and cadalene), corroborates input from higher vascular land plants. Biomarker and aromatic thermal maturity indices, such as the methylphenanthrene index, the methylnaphthalene ratio, C31 22S/(22S+22R) hopanes, C30 ap/(ap+pa) hopanes and C29 aaa 20S/(20S+20R) steranes, indicate rather thermally immature hydrocarbon source rocks, in agreement with the above CPI data. This maturity trend is also supported by the triaromatic sterane index [TA(I)/TA(I+II)], which is generally lower than 0.2.
Original languageEnglish
Pages (from-to)1-4
Number of pages4
JournalASEG Extended Abstracts
Volume2018
Issue number1
DOIs
Publication statusPublished - 2018
EventAustralasian Exploration Geoscience Conference (1st : 2018) - Sydney, Australia
Duration: 18 Feb 201821 Feb 2018

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Keywords

  • Gippsland Basin
  • Latrobe Group
  • Hydrocarbon Source Rocks
  • Biomarker
  • Cretaceous

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