Evidence for mixing of migrated hydrocarbons and indigenous organic matter in the Paleocene deepest core in IODP Expedition 378 Hole U1553D, Campbell Plateau, New Zealand

IF 2.6 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Marine Geology Pub Date : 2025-05-07 DOI:10.1016/j.margeo.2025.107576

Simon C. George , Lian Jiang , Blanca Ausín , Eleni Anagnostou , Ann G. Dunlea , Laurel B. Childress , Ursula Röhl , Deborah J. Thomas

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Abstract

International Ocean Discovery Program (IODP) Expedition 378 recovered a continuous, > 580 m thick Paleogene sedimentary sequence at Site U1553 on the Campbell Plateau, south of the South Island of New Zealand. Oil stain samples are rarely recovered during scientific ocean drilling, but one was recovered from the deepest Paleocene core in Hole U1553D (579.94 m CSF-A), associated with high amounts of methane and wet gases detected by on-board instrumentation, that led to drilling any deeper being prevented. This oil stain was analysed by gas chromatography–mass spectrometry and gas chromatography–triple quadrupole mass spectrometry, and compared with the indigenous Paleocene organic matter.

The n-alkane distribution of the oil stain sample is bimodal, suggesting mixing of a thermogenic migrated oil with a signal from the indigenous Paleocene sediments. This is confirmed by the ≥C₂₇ hopanoid and steroid biomarkers in the oil stain sample which are very similar to the immature Unit Vb early Paleocene sediments, including the presence of neohop-13(18)-enes, ββ hopanes, and βαα steranes. The C₁₀–C₂₀ aromatic compound distributions are in the molecular weight range where there is a mixed signal. The migrated thermogenic oil and gas were derived from a marine source rock containing a significant contribution from terrigenous and probably coniferous organic matter, deposited in a dysoxic depositional environment. Vertical migration of thermogenic oil and gas penetrated the early Paleocene sediments, but did not reach into the Eocene section due a significant permeability barrier associated with a middle–late Paleocene unconformity. Deeper drilling and geophysical investigation are required to understand the putative Cretaceous or older strata in this region.

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新西兰坎贝尔高原378孔U1553D古新世最深处运移烃与原生有机质混合的证据

国际海洋发现计划（IODP）的378号探险队发现了一个连续的，>；新西兰南岛南部坎贝尔高原U1553遗址上580米厚的古近系沉积层。在科学海洋钻探过程中很少回收油渍样本，但在U1553D孔（579.94 m CSF-A）最深的古新世岩心中回收了一个油渍样本，与船上仪器检测到的大量甲烷和湿气有关，导致钻探更深的钻探被阻止。采用气相色谱-质谱联用、气相色谱-三重四极杆质谱联用对油样进行了分析，并与当地古新世有机质进行了对比。油渍样品的正构烷烃分布呈双峰型，表明热源运移油与古新世原生沉积物的信号混合。油斑样品中的≥C27类藿烷和甾类生物标志物与早古新世未成熟的Vb单元沉积物非常相似，包括新藿烷-13(18)-烯、ββ藿烷和βαα甾烷的存在，证实了这一点。C10-C20芳香族化合物分布在分子量范围内，存在混合信号。运移的热生油气来自海相烃源岩，其中陆源有机质占很大比重，可能有针叶有机质，沉积于欠氧沉积环境。热生油气垂直运移穿透了早古新世沉积层，但由于中晚古新世不整合相关的显著渗透率障碍，未进入始新世剖面。需要进行更深入的钻探和地球物理调查，以了解该地区假定的白垩纪或更古老的地层。

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来源期刊

Marine Geology 地学-地球科学综合

CiteScore

6.10

自引率

6.90%

发文量

175

审稿时长

21.9 weeks

期刊介绍： Marine Geology is the premier international journal on marine geological processes in the broadest sense. We seek papers that are comprehensive, interdisciplinary and synthetic that will be lasting contributions to the field. Although most papers are based on regional studies, they must demonstrate new findings of international significance. We accept papers on subjects as diverse as seafloor hydrothermal systems, beach dynamics, early diagenesis, microbiological studies in sediments, palaeoclimate studies and geophysical studies of the seabed. We encourage papers that address emerging new fields, for example the influence of anthropogenic processes on coastal/marine geology and coastal/marine geoarchaeology. We insist that the papers are concerned with the marine realm and that they deal with geology: with rocks, sediments, and physical and chemical processes affecting them. Papers should address scientific hypotheses: highly descriptive data compilations or papers that deal only with marine management and risk assessment should be submitted to other journals. Papers on laboratory or modelling studies must demonstrate direct relevance to marine processes or deposits. The primary criteria for acceptance of papers is that the science is of high quality, novel, significant, and of broad international interest.