@article{2-s2.0-105046306414,

title = {Characterisation of bituminite and testing reproducibility of vitrinite and bituminite reflectance measurements in organic‑carbon-rich intervals of the Kimmeridge Clay Formation: ICCP Identification of Dispersed Organic Matter Working Group round robin exercises},

author = { J. Kus and A.G. Borrego and B. Bielowicz and P.J. Crosdale and M.E. Damoulianou and D. Flores and C. Fonseca and P.A. Gonçalves and P.C. Hackley and M. Hámor-Vidó and S. Henne and B. Holstein and I. Jelonek and S. Kalaitzidis and M.S. Luzhbina and J.G. Mendonça Filho and T.R. Menezes and M. Misz-Kennan and R. Orban and W. Pickel and N.V. Pronina and P. Ranasinghe and J. Reyes and G. Siavalas and A.K. Singh and P.K. Kumar Singh and I. Suárez-Ruiz and I. Sýkorová and Q. Luo and D. Životić and P.B. Wignall and  Iccp},

url = {https://doi.org/10.1016/j.coal.2026.105072},

doi = {10.1016/j.coal.2026.105072},

issn = {01665162},

year  = {2026},

date = {2026-01-01},

journal = {International Journal of Coal Geology},

volume = {325},

publisher = {Elsevier B.V.},

abstract = {Three round robin exercises (RRE) aimed at characterizing bituminite and testing the reproducibility of random vitrinite (VRo %) and bituminite (BitRo %) reflectance measurements on samples of dispersed organic matter from organic‑carbon rich shale intervals of Kimmeridge Clay Formation were conducted in 2016, 2018, and 2020. This work was conducted by the Identification of Dispersed Organic Matter Working Group (IDOM WG) of the International Committee for Coal and Organic Petrology (ICCP). The Kimmeridge Clay Formation represents the major marine source rock for the North Sea hydrocarbon province. Samples collected from Kimmeridge Bay, Dorset, England, United Kingdom and Filey Bay, North Yorkshire, England, United Kingdom outcrops and the 16/17–14 well in the Tiffany oil field, Viking Graben, North Sea, were analyzed by 19 to 23 participants in 15 to 17 laboratories from 14 to 15 countries. Samples contain moderate to high organic matter content [5.32 to 12.10 wt% total organic carbon (TOC) content] with thermal maturity ranging from immature to thermally mature (Tmax 418 to 445 °C). Participants used a standard description sheet to record bituminite morphological characteristics, including its form, size, mode of appearance, and impurities, for use in the revision of the bituminite definition. The usage of previously published classifications of bituminite types (e.g.; bituminite I sensu Teichmüller and Ottenjann; 1977) in the RRE was not found to be helpful. The indistinct, amorphous character of boundaries of bituminite, and the poor preparation of whole rock pellets for the 2018 and 2020 RRE hampered identification of bituminite. Mean random BitRo %, including outlying values, varied in all three RRE from 0.19 to 0.35% and is reported here for the first time. Application of the criterion standard deviation (SD) < 0.15 × BitRo % to exclude outlying BitRo % values showed virtually no change in modified BitRo % in immature samples (2016 and 2018 RRE) and an unexpected increase to 0.43% BitRo in the thermally mature sample (2020 RRE). Mean VRo values, including outliers in the three RRE, range from 0.47 to 0.71%, confirming the immature to thermally mature nature of samples of the Kimmeridge Clay Formation used in this study. Application of the criterion SD < 0.15 × VRo to exclude outlying values results in a comparable range of modified VRo values and a decrease in group standard deviation. Precision of VRo values (including outlying values) evaluated via the averaged unsigned multiple of the standard deviation rule (< 1.5) showed moderate to high precision comparable to historical values from similar RRE. An average reproducibility limit (RL) of 0.29% (including outlying values) showed an improvement in reproducibility relative to similar historical RRE (0.35%), which was attributed to the application of a common methodology (ASTM D7708; 2014b; 2023) to enhance the quality of data from the reflectance test method.},

note = {0},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2-s2.0-85062285436,

title = {Mercury Spikes Indicate a Volcanic Trigger for the Late Ordovician Mass Extinction Event: An Example from a Deep Shelf of the Peri-Baltic Region},

author = { J. Smolarek-Lach and L. Marynowski and W. Trela and P.B. Wignall},

url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85062285436&doi=10.1038%2fs41598-019-39333-9&partnerID=40&md5=2241b962ef650d98c001033a4f67c00c},

doi = {10.1038/s41598-019-39333-9},

issn = {20452322},

year  = {2019},

date = {2019-01-01},

journal = {Scientific Reports},

volume = {9},

number = {1},

publisher = {Nature Publishing Group},

abstract = {The Late Ordovician mass extinction (LOME) was the second largest Phanerozoic crisis, but its cause remains elusive. Several triggering mechanisms have been proposed over the years, including bioevolutionary events, oceanographic changes, and geotectonic processes. Here, we report the presence of Hg spikes in the Zbrza PIG-1 borehole from the Upper Ordovician deep shelf sections of the peri-Baltic region. A strong positive anomaly in the lower late Katian (Hg/TOC = 2537.3 ppb/wt%) was noted. No correlation between Hg and TOC (R 2 = 0.07) was distinguished in the Hirnantian, although several positive anomalies were found. Because the Hg/Mo ratio showed trends very similar to those of Hg/TOC, it seems likely that TOC values reflect the redox conditions. In order to evaluate the role of anoxia in levels of Hg enrichment several redox indicators were measured. These showed that the elevated mercury values in the Hirnantian are not caused by anoxia/euxinia because euxinic biomarkers (maleimides and aryl isoprenoids) are present in very low abundance and pyrite framboids are absent. In total, positive Hg/TOC anomalies occur in the lower late Katian, at the Katian - Hirnantian boundary, and in the late Hirnantian. The lack of a strong Hg/TOC correlation, Ni enrichments, and the absence of ‘anoxic indicators’ (no biomarkers; no framboids; low Mo concentration) at these levels, supports the interpretation that Hg enrichment is due to enhanced environmental loading. We conclude that our Hg and Hg/TOC values were associated with volcanic pulses which triggered the massive environmental changes resulting in the Late Ordovician mass extinction. © 2019, The Author(s).},

note = {17},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2-s2.0-85047823298,

title = {Mercury enrichments and the Frasnian-Famennian biotic crisis: A volcanic trigger proved?},

author = { G. Racki and M. Rakociński and L. Marynowski and P.B. Wignall},

url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85047823298&doi=10.1130%2fG40233.1&partnerID=40&md5=63e78531d000adffba52e62fdc2e45b6},

doi = {10.1130/G40233.1},

issn = {00917613},

year  = {2018},

date = {2018-01-01},

journal = {Geology},

volume = {46},

number = {6},

pages = {543-546},

publisher = {Geological Society of America},

abstract = {The Frasnian-Famennian (F-F) global event, one of the five largest biotic crises of the Phanerozoic, has been inconclusively linked to rapid climatic perturbations promoted in turn by volcanic cataclysm, especially in the Viluy large igneous province (LIP) of Siberia. Conversely, the triggers of four other Phanerozoic mass extinction intervals have decisively been linked to LIPs, owing to documented mercury anomalies, shown as the diagnostic proxy. Here, we report multiple Hg enrichments in the two-step late Frasnian (Kellwasser) crisis interval from paleogeographically distant successions in Morocco, Germany, and northern Russia. The distinguishing signal, > 1 ppm Hg in the domain of closing Rheic Ocean, was identified in different lithologies immediately below the F-F boundary and approximately correlated with the onset of the main extinction pulse. This key Hg anomaly, comparable only with an extreme spike known from the end-Ordovician extinction, was not controlled by increased bioproductivity in an anoxic setting. We suggest, therefore, that the global chemostratigraphic pattern near the F-F boundary records a greatly increased worldwide Hg input, controlled by the Center Hill eruptive pulse of the Eovariscan volcanic acme, but likely not manifested exclusively by LIP(s). Consequently, all five major biotic crises of the Phanerozoic have now been more reliably linked to volcanic cataclysms. © 2018 Geological Society of America.},

note = {83},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2-s2.0-84879418132,

title = {Evidence for shallow-water 'Upper Kellwasser' anoxia in the Frasnian-Famennian reefs of Alberta, Canada},

author = { D.P.G. Bond and M. Zatoń and P.B. Wignall and L. Marynowski},

url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879418132&doi=10.1111%2flet.12014&partnerID=40&md5=70d3011059f3579abe1f3445b42b5716},

doi = {10.1111/let.12014},

issn = {00241164},

year  = {2013},

date = {2013-01-01},

journal = {Lethaia},

volume = {46},

number = {3},

pages = {355-368},

abstract = {The Frasnian-Famennian extinction witnessed the global devastation of both level-bottom and reef communities in low latitudes. Marine extinctions in offshore level-bottom communities are associated with two widespread, transgressive, anoxic 'Kellwasser Events' that support an anoxia-extinction link. Typical Kellwasser facies of bituminous limestones and shales are not obviously recorded in shallow-water settings, and thus, it is unclear whether anoxia played a role in reef losses. We evaluate geochemical, petrographic and facies evidence for oxygen restriction from an extremely shallow-water carbonate platform in Alberta. Sequence stratigraphy places the Frasnian-Famennian boundary at a sequence boundary that tops a laminated mudstone and interrupts carbonate platform deposition. Two transgressive pulses have been identified, one of which is associated with the second, major transgression of T-R cycle IId of the Devonian eustatic sea-level curve. Geochemical proxies indicate that these transgressions were accompanied by influx of dysoxic or anoxic waters. Organic carbon and U enrichment in the Frasnian, particularly just below the Frasnian-Famennian boundary, points to episodic dysoxic conditions that probably persisted into the basal Famennian and were coincidental with the global Upper Kellwasser Event. This study provides the first evidence for the smoking gun of an anoxia-driven extinction in very shallow waters, implicating this potent killer in the demise of the Devonian reefs. © 2013 The Lethaia Foundation.},

note = {39},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2-s2.0-70349816455,

title = {Comment on "Mantle plume: The invisible serial killer - Application to the Permian-Triassic boundary mass extinction", by E. Heydari, N. Arzani and J. Hassanzadeh [Palaeogeography, Palaeoclimatology, Palaeoecology 264 (2008) 147-162]},

author = { P.B. Wignall and G. Racki},

url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-70349816455&doi=10.1016%2fj.palaeo.2009.02.031&partnerID=40&md5=e09d26beb0677e177baf6fd0755e93b7},

doi = {10.1016/j.palaeo.2009.02.031},

issn = {00310182},

year  = {2009},

date = {2009-01-01},

journal = {Palaeogeography, Palaeoclimatology, Palaeoecology},

volume = {283},

number = {1-2},

pages = {99-101},

publisher = {Elsevier B.V.},

abstract = {In a recent paper (Heydari; E.; Arzani; N.; Hassanzadeh; J.; 2008. Mantle plume: the invisible serial killer - application to the Permian-Triassic boundary mass extinction. Palaeogeography; Palaeoclimatology; Palaeoecology 264; 147-162) the cause of the end-Permian mass extinction was once again associated with the eruption of the Siberian Traps. However, this work considered the vast outpouring of flood basalts to be an incidental sideshow to the main event: the catastrophic release of huge volumes of methane to the atmosphere. This was attributed to a selection of sources - marine gas hydrates, thermogenic methane and methane from permafrost - that have been proposed by many authors previously. Uniquely, they suggest that the mantle plume (envisaged to have sourced the flood basalts) impinged beneath oceanic crust to the north of the Siberian flood basalts and that feeder dykes in the continental slope to the south heated sediments and released methane. There is no evidence for either of these two new proposed facets to end-Permian volcanism. The paper invokes an "oceanic acid bath" kill mechanism and dismisses claims for ocean anoxia at this time instead suggesting that end-Permian oceans were as well ventilated as those pertaining today. This latter claim simply ignores a vast body of sedimentological, palaeoecological and geochemical evidence for widespread anoxia in ocean and shelf settings at this time. The former claim for ocean acidity is equally suspect and based on the notion that a transition from calcite to aragonite-precipitating seas occurred at the Permian-Triassic boundary. However, previous studies have suggested that this interval occurs within a phase of "aragonite seas" and it is significant that most of the principal contributors to carbonate sediment in the Late Permian (calcareous algae and foraminifera) secreted aragonite. © 2009 Elsevier B.V. All rights reserved.},

note = {3},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2-s2.0-58949084608,

title = {Redox conditions during sedimentation of the Middle Jurassic (Upper Bajocian-Bathonian) clays of the Polish Jura (south-central Poland)},

author = { M. Zatoń and L. Marynowski and P. Szczepanik and D.P.G. Bond and P.B. Wignall},

url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-58949084608&doi=10.1007%2fs10347-008-0159-z&partnerID=40&md5=9c8cf6a16bf80921337cd2d75125ec29},

doi = {10.1007/s10347-008-0159-z},

issn = {01729179},

year  = {2009},

date = {2009-01-01},

journal = {Facies},

volume = {55},

number = {1},

pages = {103-114},

abstract = {Depositional redox conditions of the uppermost Bajocian-Bathonian (Middle Jurassic) ore-bearing clays of the Gnaszyn/Kawodrza area in the Polish Jura have been determined using an integrated geochemical (Th/U and U/Th ratios; degree of pyritisation (DOP); sulphur stable isotopes; biomarker analysis) and petrographic approach (measurements of pyrite framboid diameters; and microfacies analysis). The Th/U and U/Th ratios indicate that oxic conditions prevailed on the sea-floor during this interval, and 34S isotopes suggest open-system conditions. DOP values, however, are rather scattered, and may reflect oxic, dysoxic, or anoxic conditions. We consider that the DOP values result from reducing conditions within the sediment and the chemistry of the pore-waters, rather than true sea-floor redox conditions. Pyrite framboid populations also indicate that dysoxic conditions prevailed within the sediment, beneath an oxygenated water column. Biomarker data did not provide any evidence of water column stratification or anoxia during sedimentation of the Middle Jurassic clays. © Springer-Verlag 2008.},

note = {33},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2-s2.0-77956743329,

title = {Chapter 10 late permian double-phased mass extinction and volcanism: an oceanographic perspective},

author = { G. Racki and P.B. Wignall},

url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956743329&doi=10.1016%2fS0920-5446%2805%2980010-X&partnerID=40&md5=472d4629759478fe8a5559f2e41a7479},

doi = {10.1016/S0920-5446(05)80010-X},

issn = {09205446},

year  = {2005},

date = {2005-01-01},

journal = {Developments in Palaeontology and Stratigraphy},

volume = {20},

number = {C},

pages = {263-297},

abstract = {The two mass extinctions of the Late Permian, end-Guadalupian and end-Changhsingian events, coincide with intense volcanic paroxysms located both in subpolar and tropical realms. For the Siberian Traps eruptions in particular, thermal destabilization of methane hydrates in extensive bipolar reservoirs initiated catastrophic release of CH4 that may have triggered a subsequent runaway greenhouse culminated through the Permian-Triassic (P-Tr) boundary interval. In addition, increased geothermal heat and volcano-ice interactions since the early Late Permian resulted finally in unusual high-latitude warmth via catastrophic methane release. This combination of factors suggests excessive permafrost melting with a consequent inflow of heated and low-salinity waters. This is postulated to have provoked shutdown of the ocean thermohaline system, and thus to have caused the superanoxic event of the P-Tr boundary timespan, even if many global feedbacks and interactions were acting earlier in concert towards progressive warming and destabilized oceanic circulation and biogeochemical cycling. Both larger than hitherto assumed, Chinese and Siberian volcanic cataclysms are considered as the main driving force of profound P-Tr oceanic stagnation and superanoxia, nutrient stress and bioproductivity crash, in action in the geodynamically activated activity (due to plate boundary reorganization and accelerated rifting processes), fragile ecosystem. This end-Permian crisis acme was recorded in the Late Changhsingian-Griesbachian Chert Gap and overall 'fossilization low' through ∼10 Ma, and the consequent biogeochemical and ecological peculiarities of the 'dead"/survival intervals. In contrast, a specific volcanogenic/tectonoeustatic scenario for the end-Guadalupian crisis may be focused on the Phanerozoic sea-level minimum and/or an extraordinary concomitant uplift of the Gondwana supercontinent. © 2005 Elsevier B.V. All rights reserved.},

note = {71},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2-s2.0-10244260465,

title = {Geochemical and ecological aspects of lower Frasnian pyrite-ammonoid level at Kostomłoty (Holy Cross Mountains, Poland)},

author = { G. Racki and A. Piechota and D.P.G. Bond and P.B. Wignall},

url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-10244260465&partnerID=40&md5=bfa699d9a75116080c1dfebba9f0c623},

issn = {16417291},

year  = {2004},

date = {2004-01-01},

journal = {Geological Quarterly},

volume = {48},

number = {3},

pages = {267-282},

abstract = {The lower Frasnian (transitans Zone with Ancyrodella priamosica = MN 4 Zone) rhythmic basin succession of marly limestones and shales (upper Szydłówek Beds) at Kostomłoty, western Holy Cross Mts., Central Poland, contains a record of the transgressive-hypoxic Timan Event in this drowned part of southern Laurussian shelf. The unique facies consists of organic-rich marly shales and a distinctive pyritic, goniatite level, 1.6 m thick. The faunal assemblage is dominated by pyritized shells of diminutive mollusks with cephalopods (including goniatites Epitornoceras and Acanthoclymenia), buchioline bivalves (Glyptohallicardia) and styliolinids. This interval is marked by moderately low Th/U ratios and pyrite framboid size distributions suggestive of dysoxic rather than permanent euxinic conditions. The scarcity of infauna and bioturbation resulted in finely laminated sedimentary fabrics, as well as the low diversity of the presumed pioneer benthos (mostly brachiopods). In the topmost part of the Szydłówek Beds, distinguished by the Styliolina coquina interbedded between limestone-biodetrital layers, the above geochemical proxies and C-isotope positive shift indicate a tendency to somewhat increased bottom oxygen deficiency and higher carbon burial rate linked with a bloom of pelagic biota during high-productivity pulse. The geochemical and community changes are a complex regional record of the initial phase of a major perturbation in the earth-ocean system during a phase of intermittently rising sea level in the early to middle Frasnian, and associated with the highest positive C-isotope ratios of the Devonian.},

note = {52},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2-s2.0-1842537085,

title = {Comment on: Orbital cyclostratigraphy of the Devonian Frasnian-Famennian transition in South China, by Gong, Y.M., Li, B.H., Wang, Y., Wu, Y., Palaeogeogr. Palaeoclimatol. Palaeoecol. 168 (2001), 237-248},

author = { G. Racki and P.B. Wignall},

url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-1842537085&doi=10.1016%2fj.palaeo.2003.11.015&partnerID=40&md5=72500e7177a2d0c0d5fcfe5cba9a6b73},

doi = {10.1016/j.palaeo.2003.11.015},

issn = {00310182},

year  = {2004},

date = {2004-01-01},

journal = {Palaeogeography, Palaeoclimatology, Palaeoecology},

volume = {205},

number = {1-2},

pages = {169-170},

publisher = {Elsevier B.V.},

abstract = {The four-order orbital cyclostratigraphy scheme of the Frasnian-Famennian transition in South China of Gong et al. (Palaeogeogr. Palaeoclimatol. Palaeoecol. 168 (2001) 237) is criticized. Its dubious character is related to unreliable documentation of the four-order hierarchical Milankovitch cyclicity, paired with a highly speculative idea of modification of the causal orbital parameters in the mass extinction time interval by alleged bolide impact. © 2004 Elsevier B.V. All rights reserved.},

note = {1},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2-s2.0-2542543592,

title = {Extent and duration of marine anoxia during the Frasnian-Famennian (Late Devonian) mass extinction in Poland, Germany, Austria and France},

author = { D.P.G. Bond and P.B. Wignall and G. Racki},

url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-2542543592&doi=10.1017%2fS0016756804008866&partnerID=40&md5=54612dd38679c67f098fdab2321f3ec5},

doi = {10.1017/S0016756804008866},

issn = {00167568},

year  = {2004},

date = {2004-01-01},

journal = {Geological Magazine},

volume = {141},

number = {2},

pages = {173-193},

publisher = {Cambridge University Press},

abstract = {The intensity and extent of anoxia during the two Kellwasser anoxic events has been investigated in a range of European localities using a multidisciplinary approach (pyrite framboid assay; gamma-ray spectrometry and sediment fabric analysis). The results reveal that the development of the Lower Kellwasser Horizon in the early Late rhenana Zone (Frasnian Stage) in German type sections does not always coincide with anoxic events elsewhere in Europe and, in some locations, seafloor oxygenation improves during this interval. Thus, this anoxic event is not universally developed. In contrast, the Upper Kellwasser Horizon, developed in the Late linguiformis Zone (Frasnian Stage) in Germany correlates with a European-wide anoxic event that is manifest as an intensification of anoxia in basinal locations to the point that stable euxinic conditions were developed (for example; in the basins of the Hoy Cross Mountains; Poland). The interval also saw the spread of dysoxic waters into very shallow water (for instance; reefal) locations, and it seems reasonable to link the contemporaneous demise of many marine taxa to this phase of intense and widespread anoxia. In basinal locations, euxinic conditions persisted into the earliest Famennian with little change of depositional conditions. Only in the continental margin location of Austria was anoxia not developed at any time in the Late Devonian. Consequently it appears that the Upper Kellwasser anoxic event was an epicontinental seaway phenomenon, caused by the upward expansion of anoxia from deep basinal locales rather than an 'oceanic' anoxic event that has spilled laterally into epicontinental settings. © 2004 Cambridge University Press.},

note = {199},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2-s2.0-33847023367,

title = {Eutrophication by decoupling of the marine biogeochemical cycles of C, N, and P: A mechanism: For the Late Devonian mass extinction: Comment},

author = { G. Racki and P.B. Wignall},

url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-33847023367&doi=10.1130%2f0091-7613%282001%29029%3c0469%3aEBDOTM%3e2.0.CO%3b2&partnerID=40&md5=c6403c0af43a0eb1ca1ab650a6510b28},

doi = {10.1130/0091-7613(2001)029<0469:EBDOTM>2.0.CO;2},

issn = {00917613},

year  = {2001},

date = {2001-01-01},

journal = {Geology},

volume = {29},

number = {5},

pages = {469-470},

publisher = {Geological Society of America},

abstract = {[No abstract available]},

note = {4},

keywords = {},

pubstate = {published},

tppubtype = {article}

}