Micro-ablation, a new technique to remove drilling fluids and other contaminants from fragmented and fissile rock material

Jarrett, Amber J. M.; Schinteie, Richard; Hope, Joseph; Brocks, Jochen J.

doi:10.1016/j.orggeochem.2013.06.005

Cited by 43 publications

(37 citation statements)

References 16 publications

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“…Because of this scarcity, such ancient steroids are easily overprinted with anthropogenic petroleum products that will usually have a Phanerozoic source (Brocks et al ., , ; Brocks, ). Therefore, the analyses in this study are accompanied by rigorous tests for syngeneity, including comprehensive laboratory blanks and quantitative elucidation of contaminants on rock surfaces (Jarrett et al ., ; Schinteie & Brocks, ).…”

Section: Resultsmentioning

confidence: 99%

“…Given the ubiquitous presence of contaminant petroleum products on rock surfaces, observed in this and previous studies (Brocks et al ., , ; Rasmussen et al ., ; Brocks, ; Jarrett et al ., ; Schinteie & Brocks, ; French et al ., ), we posit that it is best to err on the side of caution and interpret previously reported ergostanes, stigmastanes, and C 30 steranes from the Chuar Group as allochthonous. According to this view, C 26 and C 27 sterols are not only the dominant but possibly the sole conventional sterane precursors in the Chuar Group.…”

Section: Discussionmentioning

confidence: 99%

“…() and Brocks (). Fissile mudstones and shales, and pieces of rock too small to be cut by saw, were treated using the microablation technique (Jarrett et al ., ). The exterior and interior portions of each sample were ground to powder (>240 mesh) using a steel puck mill (Rocklabs Ltd., Onehunga, New Zealand).…”

Section: Samples and Methodsmentioning

confidence: 97%

“…Detailed MS operating conditions for full‐scan and MRM analyses are given in Jarrett et al . (). The GC was equipped with a 60 m DB‐5 MS capillary column (0.25 mm i.d., 0.25 μm film thickness; Agilent JW Scientific, Agilent Technologies, Santa Clara, CA, USA), and helium was used as the carrier gas at a constant flow of 1 mL min −1 .…”

Section: Samples and Methodsmentioning

confidence: 99%

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Early sponges and toxic protists: possible sources of cryostane, an age diagnostic biomarker antedating Sturtian Snowball Earth

et al. 2015

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The period 800-717 million years (Ma) ago, in the lead-up to the Sturtian Snowball glaciation, saw an increase in the diversity of eukaryotic microfossils. To afford an independent and complementary view of this evolutionary period, this study presents the distribution of eukaryotic biomarkers from three pre-Sturtian successions across the supercontinent Rodinia: the ca. 780 Ma Kanpa Formation of the Western Australian Officer Basin, the ca. 800-740 Ma Visingsö Group of Sweden, and the 740 Ma Chuar Group in Arizona, USA. The distribution of eukaryotic steranes is remarkably similar in the three successions but distinct from all other known younger and older sterane assemblages. Cholestane was the only conventional structure, while indigenous steranes alkylated in position C-24, such as ergostane, stigmastane, dinosterane and isopropylcholestane, and n-propylcholestane, were not observed. This sterane distribution appears to be age diagnostic for the pre-Sturtian Neoproterozoic. It attests to the distinct evolutionary state of pre-Snowball eukaryotes, pointing to a taxonomic disparity that was still lower than in the Ediacaran (635-541 Ma). All three basins also show the presence of a new C28 sterane that was tentatively identified as 26-methylcholestane, here named cryostane. The only known extant organisms that can methylate sterols in the 26-position are demosponges. This assignment is plausible as molecular clocks place the appearance of the earliest animals into the pre-Sturtian Neoproterozoic. The unusual 26-methylsterol may have protected sponges, but also other eukaryotes, against their own membranolytic toxins. Some protists release lytic toxins to deter predators and kill eukaryotic prey. As conventional membrane sterols can be the site of attack for these toxins, sterols with unusual side-chain modification protect the cell. This interpretation of cryostane supports fossil evidence of predation in the Chuar Group and promotes hypotheses about the proliferation of eukaryophagy in the lead-up to the Cryogenian.

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Samples and Methodsmentioning

confidence: 97%

Section: Samples and Methodsmentioning

confidence: 99%

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Early sponges and toxic protists: possible sources of cryostane, an age diagnostic biomarker antedating Sturtian Snowball Earth

et al. 2015

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“…Other biomarker studies of Archean, Paleoproterozoic and Mesoproterozoic sedimentary rocks, conducted in the era of heightened contamination awareness, reveal a similar picture of non-detection of eukaryote-specific 24-alkylated steranes (Blumenberg et al, 2012;Flannery and George, 2014;Hoshino et al, 2015) or their detection at levels than cannot be reliably distinguished from contamination (Luo et al, 2015;Zhang et al, 2016). Finally, new methodologies for evaluating the thermal regime experienced by sedimentary organic matter (Ferralis et al, 2016), the cleaning of contaminated rock samples prior to analysis (Jarrett et al, 2013) and a focus on directed identification and sampling of pockets of well-preserved Proterozoic and Archean sediments (Bruisten et al, 2013) suggest that the pre-Cambrian biomarker record can be elaborated and imbued with greater confidence.…”

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confidence: 96%

Paleoproterozoic sterol biosynthesis and the rise of oxygen

Gold

Caron

Fournier

et al. 2017

Nature

102

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The Record of Precambrian Steroidal HydrocarbonsThe record of sterane and triterpane hydrocarbon biomarkers in Archean and Proterozoic sedimentary rocks has come under extremely thorough scrutiny in recent times. Concerns about contamination, and doubts about reports of steroidal hydrocarbons in the 2.7 billion year-old Fortescue Group sediments of the Pilbara Craton (Brocks et al., 1999), were initially raised in 2003(Brocks et al., 2003. These potential problems became increasingly difficult to dismiss when new and improved types of geochemical analyses were devised and applied. For example, Brocks and colleagues showed that a selection of rock and sediment samples from a range of localities were ubiquitously contaminated with petroleum-and plastic-derived organic compounds . Analyses of thin slices of sediment core showed that spatial distributions of hydrocarbons could be used to distinguish indigenous hydrocarbons from surface contaminants in Archean shales (Brocks, 2011). In another example, the carbon isotopic data values of in situ and insoluble kerogen and pyrobitumen in rock formations that had previously yielded biomarkers were discrepant from those of the extractable hydrocarbons, meaning that the latter could not be indigenous (Rasmussen et al., 2008).

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A framework for the extraction and interpretation of organic molecules in speleothem carbonate

Wynn

Brocks

2014

Rapid Comm Mass Spectrometry

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Micro-ablation, a new technique to remove drilling fluids and other contaminants from fragmented and fissile rock material

Cited by 43 publications

References 16 publications

Early sponges and toxic protists: possible sources of cryostane, an age diagnostic biomarker antedating Sturtian Snowball Earth

Early sponges and toxic protists: possible sources of cryostane, an age diagnostic biomarker antedating Sturtian Snowball Earth

Paleoproterozoic sterol biosynthesis and the rise of oxygen

A framework for the extraction and interpretation of organic molecules in speleothem carbonate

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