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The well-preserved Llandovery (lower Silurian) succession of Anticosti Island (Quebec, eastern Canada) contains an expanded Aeronian–Telychian boundary interval when compared to other coeval basins. This boundary interval on Anticosti Island also includes two of the most important Llandovery biogeochemical events, the late Aeronian and Valgu events. These two events were previously documented in the Jupiter and Chicotte formations through the study of conodont, graptolite, and brachiopod biostratigraphy and δ13 C chemostratigraphy. Despite these multiple investigations, the exact position of the Aeronian–Telychian stage boundary on Anticosti Island has not been firmly established. Here we locally define and globally correlate chitinozoan biozones to refine the position of this stage boundary. The Ancyrochitina ramosaspina biozone, recognized in the Ferrum Member of the Jupiter Formation, correlates with the global Conochitina alargada biozone and indicates an Aeronian age. The Eisenackitina dolioliformis biozone suggests mostly a Telychian age for the Pavillon Member of the Jupiter Formation and the Chicotte Formation. Three new species are defined, namely Conochitina asselinae sp. nov., Spinachitina glooscapi sp. nov., and Ancyrochitina wilsonae sp. nov. (registration date: 4 December 2024, publication LSID: urn:lsid:zoobank.org:pub:11184506-F273-4D7A-BC28-A1BB4BC8FCD8, asselinae LSID: D282DA9D-6A9C-4B9E-AA6C-9ADC4473E95B, glooscapi LSID: 5801DC12-4EA1-439F-B7C8-FAF7C1B9D2C7, wilsonae LSID: 549EEF2F-7F19-4E6D-9F8E-384594B2FE65). Our new chitinozoan data, combined with previous studies, allow a comparison with the well-studied Baltic succession, confirming that limited unconformities mark the Aeronian–Telychian boundary interval on Anticosti Island, in contrast to the less complete coeval location. Our refined age model for the Aeronian to Telychian succession of Anticosti Island provides a solid baseline to study further Llandovery biochemical events in the aftermath of the Late Ordovician mass extinction. [ABSTRACT FROM AUTHOR]

Fossil (zoo)plankton dynamics during Devonian ocean‐anoxic and extinction events can shed light on the palaeoceanographic and geochemical processes that shaped the middle Palaeozoic biosphere. However, datasets on (Upper) Devonian marine palynology, illustrating such dynamics, remain underexplored. The type section of the Sweetland Creek Shale in Iowa (USA) offers a detailed conodont zonation for the upper Frasnian and across the Frasnian–Famennian boundary, records the Upper and Lower Kellwasser events and has pristine preservation of organic material, making this an ideal section to study the effects of this catastrophic event on chitinozoan zooplankton populations. A total of 3998 specimens were recovered, imaged and classified into 12 distinct species, 10 of which were previously unknown. This study demonstrates the unrealized potential of chitinozoans as a regional biostratigraphic tool in the Upper Devonian. The Lower Kellwasser Event is characterized by a drop in chitinozoan abundance and the run up to the Upper Kellwasser Event marks a period of rapid species turnover rates. Interestingly, every assemblage in this interval is nearly monospecific. Patterns of changing spine morphologies in Fungochitina pilosa, Ramochitina sp. A and Saharochitina sp. A are herein explored as potential ecophenotypic expressions. We identify Angochitina monstrosa as a new disaster species. The discovery of two teratological chitinozoans specimens, in combination with the presence of the disaster species Angochitina monstrosa and deformation in contemporaneous conodonts, supports our previous discovery that marine teratology is a feature of many Palaeozoic extinction events, possibly triggered by the injection of hydrothermal brines into the ocean. [ABSTRACT FROM AUTHOR]

Sedimentary-exhalative (sedex) ore deposits were formed by discharge of metal-rich brines into ancient ocean basins. Chemical, isotopic, and geologic data from several Paleozoic sedex districts suggest that the brine discharges also supplied enormous quantities of radiogenic Sr and biolimiting nutrients to the oceans. Seven middle Paleozoic sedex events appear to coincide with short-duration positive excursions (“spikes”) in the global marine Sr-isotope record that are not explained by current oceanic models. These strong temporal correlations, combined with mass balance evidence and oceanographic modeling, suggest the flux of radiogenic Sr-rich sedex brines may have been sufficient to cause these prominent spikes. If these sedex hydrothermal events are recorded in the secular record, then the 87 Sr/ 86 Sr record may provide a unique tool for ore genesis studies and for assessing the mineral potential of sedimentary basins of different ages. The apex of these enigmatic 87 Sr/ 86 Sr spikes correlate with global δ 13 C and δ 18 O spikes, periods of global anoxia, deposition of metal-rich black shales, deposition of ironstones, climate change, metal-induced malformation (teratology) of marine organisms and significant mass extinctions. While the relationships among these phenomena remain poorly understood and diverse models for these events have been proposed, most invoke an increased flux of biolimiting nutrients resulting in ocean eutrophication. Evidence that the flux of key biolimiting nutrients and metals contained in sedex brines may have been equivalent to or surpass that of the total modern riverine flux to the ocean suggests that these sedex brine exhalations may have triggered global chemical and biological events. [ABSTRACT FROM AUTHOR]

The late Katian Elkhorn event is a biogeochemical perturbation preceding the Late Ordovician mass extinction (LOME) with an exceptional record in the United States (U.S.). Results of our recent studies in this interval allow revised temporal ordering to strata across multiple basins providing insights into the magnitude of environmental disturbance and associated processes and feedbacks. The record of the Elkhorn event spans portions of the Appalachian and Midcontinent basins in the eastern U.S. and the Williston Basin and Cordilleran margin in the west. Our work focuses heavily on the Midcontinent Basin in particular, as it shares many characteristics of size, tectonic setting, and lithofacies with the Baltic Basin, providing the potential for resolving global signatures of the event. In its type-area, the Cincinnatian Series ends with the Elkhorn event. The succession is marked by shallowing from subtidal to marginal marine facies, capped by a karstic sequence boundary. Our new conodont data demonstrate that an overlying white to pink crinoidal grainstone package, previously assigned to the basal Silurian “white” Brassfield Formation near the Ohio-Indiana state line, is in fact Upper Ordovician. Further, δ13Ccarb values in this unit are elevated, in line with later phases of the Elkhorn event (2‰ more positive than reported Rhuddanian values). These findings support a correlation of the grainstone interval with the Fernvale Formation of central Tennessee. To the east, much of the northern Appalachian Basin was overfilled with widespread marginal marine to terrestrial red beds by the onset of the Elkhorn event, while the Midcontinent Basin to the west remained relatively sediment starved. In the southern Midcontinent, the mid-Elkhorn event sequence boundary was onlapped by ironstone deposition (lower Fernvale Formation). The ironstones are overlain by sparry and hematitic grainstones with localized bioherms. In Arkansas, where the Fernvale is thickest (>30 m), the sparry phase gives way upward to manganese carbonates and bioherms. Across the region, the Fernvale is, in turn, cut by a sequence boundary, suggesting a yet higher Katian sequence, and is perforated by paleokarst pockets that are filled and overlain by upper Katian (Ka4) sediments. This sequence boundary is onlapped by black shales and the thickest (>10 m) phosphorite of the Ordovician at the end of the Elkhorn event. Previous studies have suggested age equivalence of the Elkhorn and Paroveja δ13Ccarb excursions in Laurentia and Baltica. Despite the attraction of aligning the latest Richmondian and Pirgu regional stages, our data sets demonstrate that this is a miscorrelation. Critical to this revision are new integrated biostratigraphic and chemostratigraphic data sets in a transect from the margin of the Appalachian Basin into the Midcontinent Basin. The new data reveal that the Elkhorn Shale and Fernvale Formation are overlain by the Brainard and laterally equivalent Sylvan, and Mannie shales. These shale successions contain graptolites of the complanatusand pacificus zones. Thus, the Elkhorn event occurred in the latest manitoulinensis Zone, suggesting correlation with the Baltic Moe δ13Ccarb excursion. Our extensive new data sets provide regional chronostratigraphic correlation of strata deposited during the Elkhorn event. When temporally ordered, these records provide evidence for high amplitude sea level oscillations, major redox fluctuations, and reef pulses that demonstrate the waxing and waning of continental ice sheets on Gondwana and the spread of oceanic anoxia only a few million years before the LOME. These findings further call into question traditional models of rapid glaciation during a long-lived greenhouse state as the sole driver of the LOME and emphasize the need for new integrated Upper Ordovician research initiatives to better characterize Katian events. [ABSTRACT FROM AUTHOR]

Study of a subsurface core (named F688) from northern Indiana provides integrated data sets linking Katian chronostratigraphic records of the Appalachian and Midcontinent basins. The F688 core shows a variety of shallow- and deep-water facies containing numerous, well-preserved and zonally significant fossil species and diagnostic chemostratigraphic patterns. The succession belonging to the Cincinnatian Regional Stage in the F688 core is 210 m thick. Detailed benchtop examination of the succession revealed several phosphatic intervals, rich brachiopod faunas, multiple graptolitic horizons, and at least two tephras. Elemental analysis was conducted at 60 cm spacing quantifying lithofacies composition. Based on these results, the succession was assigned to six previously defined lithostratigraphic units (Kope, Waynesville, Liberty, Whitewater, Elkhorn, and Fort Atkinson formations). This lithostratigraphic succession shares components with both the Appalachian and Midcontinent basins, suggesting deposition near their shared margin. Twenty samples yielded abundant, well-preserved, low-diversity conodont assemblages with long-ranging taxa that clearly demarcate the position of the Ordovician–Silurian boundary at the top of the succession in the core. More than fifty palynologic samples, targeting graptolite-bearing intervals, were processed for chitinozoans and produced important new insights. The Kope Formation contains the chitinozoan species Belonechitina kjellstromi, Hercochitina downiei, and Clathrochitina sp. nov., co-occurring with a graptolite assemblage suggestive of the Geniculograptus pygmaeus Zone. Samples from the overlying Waynesville Formation produced graptolites indicative of the upper G. pygmaeus to Paraorthograptus manitoulinensis zones co-occurring with the long-ranging chitinozoan species Belonechitina micracantha and Plectochitina spongiosa as well as several new species of the genera Tanuchitina and Hercochitina. Higher in the core, the Liberty, Whitewater, Elkhorn, and Fort Atkinson formations yielded chitinozoan species characteristic of the upper Katian biozones of Anticosti Island and Nevada, such as Tanuchitina anticostiensis, Hercochitina longi, and Eisenackitina ripae. Results of δ13Ccarb analysis reveal partial preservation of the Kope, Waynesville, and Elkhorn excursions. A tephra in the rising limb of the Waynesville Excursion yielded needle-shaped clear zircons that will provide a high-precision U-Pb age. The Fort Atkinson Formation is overlain by the Brassfield Formation containing Silurian conodonts and δ13Ccarb values suggesting an Aeronian age. Chronostratigraphic data from our study of the F688 core resolves longstanding uncertainty about correlations between strata of Katian Age in the Appalachian and Midcontinent basins. Integration of core F688 with our other regional chronostratigraphic data in the Midcontinent Basin demonstrates that the Fort Atkinson Formation of the Indiana and Illinois subsurface is age equivalent to the Fernvale Formation of Tennessee, Arkansas, and Oklahoma. Across this area, the Fernvale is overlain by graptolitic shales of the uppermost P. manitoulinensis to basal Dicellograptus complanatus graptolite zones. By contrast, the type Fort Atkinson Formation of Iowa is interpreted to occur completely within the younger D. complanatus Zone. These regional correlations taken as a whole suggest that the uppermost Katian (all of Ka4) and all but the uppermost Hirnantian are missing throughout much of the Appalachian Basin. By contrast, the Midcontinent Basin contains a much more complete upper Katian and Hirnantian succession. Our comprehensive approach is correcting temporal miscorrelation and providing robust chronostratigraphic context for study of biogeochemical events, which will further enable us to disentangle proxy data and identify the processes that drove the Katian diversity peak and culminated in the Late Ordovician mass extinction. [ABSTRACT FROM AUTHOR]