Marine influence helps preserve the oil potential of coaly source rocks: Eocene Mangahewa Formation, Taranaki Basin, New Zealand

摘要: Abstract Many Cretaceous–Cenozoic coaly source rocks in Australasian and southeast Asian basins were deposited coastal plain environments, yet the effect of early diagenetic marine influence on their oil potential is not well understood. An integrated organic geochemical petrographic study humic coals from Eocene Mangahewa Formation (Taranaki Basin, New Zealand) was undertaken with predominantly raised mire petrofacies, subordinate proportions planar mires. The total S content 0.63–4.4% (dry, ash-free) indicated very slight to strong degrees influence. Other than minor addition inferred mangrove derived suberinite associated liptodetrinite, degree had no obvious maceral or plant tissue abundance. However, hydrogen index (HI) values up ca. 150% (109 mg HC/g TOC) higher, (C 6+ ) 140% (43 mg/g TOC) higher among more strongly influenced coals. Correlation solvent extract parameters pristane/phytane, C 27 –C 29 diasteranes/steranes, steranes/hopanes, 35 /(C  + C 34 homohopanes oleanane suggested that inundation brackish water into peat forming environment enhanced bio-resistance other lipids through sulfurization, thereby helping preserve inherent H original biomass. Conversely, only a capacity generate paraffinic oil. Total ( n -C non-volatile 15+ potentials instead controlled primarily by abundance leaf cutinite liptodetrinite. This, turn, dependent type facies, facies having better for preservation litter because generally groundwater level. Marine nonetheless beneficial charge rock sequences HIs enhance efficiency quantum expulsion increased saturation coal pore system.