Chitinozoan response to the 'Kellwasser events' : population dynamics and morphological deformities across the Frasnian-Famennian mass extinction

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

Astronomical calibration of the Famennian (Upper Devonian) time scale

The Late Devonian was affected by major, irreversible changes including two of the most severe biodiversity crises in Earth’s history, the so-called Kellwasser and Hangenberg Events (respectively near the Frasnian – Famennian (F-F) and the Devonian – Carboniferous (D-C) boundaries). Currently, hypotheses for the Late Devonian extinctions include sea-level fluctuations and regression, climate cooling, ocean anoxia, massive volcanism and/or bolide impact. Unfortunately, testing these hypotheses is impaired by a lack of sufficient temporal resolution in paleobiological, tectonic and proxy climate records. Recent advances in astronomical calibration have improved the accuracy of the Frasnian time scale and part of the Famennian. However, the time duration of the Famennian Stage remains poorly constrained. During the Late Devonian, an epieric sea in North-America mid-continent occupied the Illinois Basin where a complete Late Frasnian – Early Carboniferous succession of deep-shelf deposits was archived. A record of this sequence is captured in three overlapping cores (H-30, Sullivan Slough and H-32). The H-30 core section spans the F-F boundary; the Sullivan Slough section spans almost all of the Famennian and the H-32 section sampled spans the D-C boundary. To have the best chance of capturing Milankovitch cycles, 2200 rock samples were collected at minimum 5-cm-interval across the entire sequence. Magnetic susceptibility (MS) was measured on each sample and the preservation of climatic information into the signal was verified through geochemical analyses. To estimate the duration of the Famennian stage, we applied multiple spectral techniques and tuned the MS signal using the highly stable 405 k.y. cycle for Sullivan Slough and the obliquity cycle (34.4 k.y.; Waltham, 2015) for the H-30 and H-32 cores. Based on the correlation between the cores and the tuning, we constructed a Famennian astronomical time scale, which indicates a duration of 13.3 m.y. An uncertainty of ± 0.5 m.y. was calculated to assess the errors raising from the stratigraphic position of the F-F and D-C boundaries, and the 405 k.y. cycle counting error. Our estimate duration is very close to the GTS-2012 duration (Becker, 2012) interpolated from the high-resolution (U/Pb) radiometric ages available for the uppermost Devonian

Impact of sedimentary-exhalative hydrothermal systems on marine chemistry and mass extinctions : applications for ore genesis research and mineral exploration

Times of metal-rich brine discharge into ancient ocean basins, associated with the formation of sedimentary-exhalative (sedex) Zn-Pb-Ba ore deposits, coincided with short-duration positive excursions ("spikes") in the global marine Sr isotope record. While these spikes are unexplained by conventional oceanic models, chronostratigraphic correlations, combined with mass balance evidence and oceanographic modeling, suggest that the flux of radiogenic Sr from sedex brines during ore formation is sufficient to explain these previously enigmatic Sr-87/Sr-86 spikes. We review existing Sr-87/Sr-86 data and present new data as verification of these global Sr-87/Sr-86 spikes and their correlations with the formation of giant sedex ore deposits. Major events include an 1 x 10(-4) (similar to 0.7078-similar to 0.7079) excursion contemporaneous with formation of the Rammelsberg deposit at -389 Ma; spikes on the order of 1 to 3 x 10(-4), coeval with formation of the Meggen deposit at similar to 381 Ma, several ore deposits in the Macmillan Pass district at similar to 379 to 375 Ma, and the Silvermines deposits at similar to 352 Ma; and two >6 x 10(-4) spikes coincident with formation of the giant Navan deposit at similar to 346 Ma and Red Dog deposits at similar to 337 Ma. Moreover, the timing of peak 8(87)Sr/Sr-86 spikes correlates with global delta C-13 and delta O-18 spikes,deposition of metal-rich black shales and ironstones, metal-induced malformation (teratology) of marine organisms, and mass extinctions. The relationships among these features were poorly understood, but our new model explains how the flux of key biolimiting nutrients and metals contained in sedex brines, demonstrably equivalent to or exceeding that of the total modern riverine flux to the ocean, spurred ocean eutrophication, which, ultimately, through a series of positive feedback mechanisms, may have triggered global chemical and biological events. If, as we hypothesize, sedex hydrothermal systems are recorded in the global marine isotopic, geologic, and biological records, our findings define a new approach to the study of and exploration for sedex deposits. We demonstrate that fluid inclusion solute chemistry and isotopic and stratigraphic studies of sedex deposits, coupled with chronostratigraphic correlation and high-resolution Sr-87/Sr-86 isotope chemostratigraphy, can be used to answer long-standing questions about geologic processes responsible for formation of these extraordinary deposits. This approach provides evidence for the age, duration, and fluxes of fluids and metals vented into the ocean by these giant hydrothermal systems. Accordingly, the marine Sr-87/Sr-86 curve constitutes a global exploration tool that could be applied to assess the mineral potential of sedimentary basins.To illustrate the potential of this tool to identify favorable stratigraphic ages and basins with potential for undiscovered giant sedex deposits, we highlight several spikes, on par with those characteristic of the Red Dog and Navan deposits, which have not been correlated with known metal deposits. Given these strong temporal correlations, mass balance estimates, and results of ocean chemistry modeling, our study suggests that further work is warranted to determine the extent to which periodic venting of hydrothermal basinal brines into the ocean has influenced the evolution of marine chemistry. Ultimately, these global signatures can be applied to the study of and exploration for sedex deposits

Improved Measurement of the Cabibbo-Kobayashi-Maskawa Angle α Using B0(B¯)→ρ+ρ- Decays

We present results from an analysis of B0(B̅ 0)→ρ+ρ- using 232×106 Υ(4S)→BB̅ decays collected with the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC. We measure the longitudinal polarization fraction fL=0.978±0.014(stat)+0.021/-0.029(syst) and the CP-violating parameters SL=-0.33±0.24(stat)+0.08/-0.14(syst) and CL=-0.03±0.18(stat)±0.09(syst). Using an isospin analysis of B→ρρ decays, we determine the unitarity triangle parameter α. The solution compatible with the standard model is α=(100±13)°

Improved measurement of the Cabibbo-Kobayashi-Maskawa angle α using B0(B)→p+p- decays

We present results from an analysis of B0(B¯¯¯0)→ρ+ρ− using 232×106 Υ(4S)→BB¯¯¯ decays collected with the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC. We measure the longitudinal polarization fraction fL=0.978±0.014(stat)+0.021−0.029(syst) and the CP-violating parameters SL=−0.33±0.24(stat)+0.08−0.14(syst) and CL=−0.03±0.18(stat)±0.09(syst). Using an isospin analysis of B→ρρ decays, we determine the unitarity triangle parameter α. The solution compatible with the standard model is α=(100±13)°