Gamma-ray spectrometry across the Upper Devonian basin succession at Kowala in the Holy Cross Mountains (Poland)

The Upper Devonian sequence at Kowala in the Holy Cross Mountains was logged using gamma-ray spectrometry, for investigating the changes of oxygenation level in the Late Devonian basin. The Th/U ratio indicates that oxygen levels were low throughout the Late Frasnian interval, with low peaks during the Kellwasser Events showing anoxic conditions in the basin. The F-F boundary interval was also oxygen deficient, but there may have been a brief reoxygenation at the boundary itself. By the Famennian crepida Zone, the basin gradually began to reoxygenate, but in the trachytera Zone another anoxic event, the Annulata Event occurred, causing a bloom rather than extinction of specially adapted taxa such as Guerichia. Thus the gamma-ray spectrometry data suggests that basinal anoxia prevailed through much of the Late Frasnian. The F-F extinction might have been the result of prolonged stresses imposed on the ecosystem, particularly during the euxinic Upper Kellwasser Event

Gamma-ray spectrometry across the Upper Devonian basin succession at Kowala in the Holy Cross Mountains (Poland)

The Upper Devonian sequence at Kowala in the Holy Cross Mountains was logged using gamma-ray spectrometry, for investigating the changes of oxygenation level in the Late Devonian basin. The Th/U ratio indicates that oxygen levels were low throughout the Late Frasnian interval, with low peaks during the Kellwasser Events showing anoxic conditions in the basin. The F-F boundary interval was also oxygen deficient, but there may have been a brief reoxygenation at the boundary itself. By the Famennian crepida Zone, the basin gradually began to reoxygenate, but in the trachytera Zone another anoxic event, the Annulata Event occurred, causing a bloom rather than extinction of specially adapted taxa such as Guerichia. Thus the gamma-ray spectrometry data suggests that basinal anoxia prevailed through much of the Late Frasnian. The F-F extinction might have been the result of prolonged stresses imposed on the ecosystem, particularly during the euxinic Upper Kellwasser Event

Palynofloras of the Chigua (Devonian) and Malimán (Mississippian) formations from the Precordillera Argentina: age, correlation and discussion of the D/C boundary

Se presenta el análisis cualitativo y cuantitativo de las asociaciones palinológicas obtenidas de las formaciones Chigua (Devónico) y Malimán (Mississippiano), aflorantes en la Cuenca Río Blanco, Precordillera Argentina. La relación estratigráfica entre ambas unidades es mediante una discordancia angular. Una detallada correlación de ambas palinofloras con otras coetáneas permite su datación precisa. La palinoflora de la Formación Chigua es correlacionable con la Zona G. lemurata-C. magnificus del Givetiano temprano de Euramerica. El alcance estratigráfico de las especies autóctonas halladas en la Formación Malimán sustentan una edad viséana temprana, aunque la presencia de algunas especies del Tournaisiano tardío sugieren que esta edad podría estar representada en la parte inferior de la formación. Esta palinoflora es correlacionada con 1) la Zona Endoculeospora larga del Viséano de Australia, 2) las zonas CM y Pu del Tournaisiano tardío – Viséano temprano de Euramerica y 3) la palinoflora de la Formación Itacua atribuida al Viséano temprano presente en el extremo sur de Bolivia. El hiato estratigráfico entre ambas formaciones está avalado por las distintas edades de las palinofloras encontradas y por el rango estratigráfico de los palinomorfos retrabajados registrados en la Formación Malimán. Así, se documentan dos períodos de acumulación de sedimentos durante el Frasniano y probablemente durante el Tournaisiano temprano. La ausencia de formas retrabajadas del Devónico más tardío (Famenniano tardío o “Struniano”) sugiere que no habría depositación durante este intervalo. Otros palinomorfos retrabajados del Silúrico Tardío y Devónico Temprano se encuentran en la Formación Malimán. La mezcla de palinomorfos del Silúrico al Tournaisiano temprano se vincula con la erosión penecontemporánea de áreas levantadas que habrían conformado la Protoprecordillera, por una combinación de procesos tectónicos y glacio-eustáticos durante el Frasniano tardío, Fameniano y Tournaisiano temprano.A qualitative and quantitative analysis is presented of palynological assemblages recovered from outcrops of the Chigua (Devonian) and Malimán (Mississippian) formations, in the Río Blanco Basin, Precordillera of Argentina. An angular unconformity separates these two formations. Both units are dated precisely in comparison with palynofloras elsewhere. The Chigua Formation is correlatable with the early Givetian G. lemurata-C. magnificus Zone of Euramerica. The stratigraphic ranges of the non-reworked taxa in the Malimán Formation support an early Viséan age. However, the presence of some late Tournaisian species suggests that the lower part of the formation correspond to this age. The palynoflora of the Malimán Formation suggests correlation with 1) the Viséan Endoculeospora larga Assemblage of Australia, 2) the late Tournaisian – early Viséan CM and Pu zones of Euramerica, and 3) the early Viséan assemblage of the Itacua Formation of southernmost Bolivia. A hiatus comprising Frasnian to early Tournaisian is confirmed on the basis of the different ages of the two assemblages and the stratigraphic ranges of reworked palynomorphs found in the Malimán Formation. These, attest to sedimentation and subsequent erosion of Frasnian and probably also Tournaisian strata. The absence of reworked forms of the latest Devonian (late Famennian or “Strunian”) suggests a corresponding period of non-deposition. The Malimán Formation also contains reworked palynomorphs of Late Silurian and Early Devonian ages. The reworking of palynomorphs documents the penecontemporaneous erosion of uplifted areas that would have conformed the Protoprecordillera, due to late Frasnian, Famennian and early Tournaisian tectonic and glacio-eustatic processes affecting the area involved.Fil: Rodriguez Amenabar, Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Geología; ArgentinaFil: Di Pasquo Lartigue, Maria. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Geología; ArgentinaFil: Azcuy, Carlos Leopoldo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Geología; Argentin

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

The lower Frasnian (transitans Zone with Ancyrodella priamosica = MN 4 Zone) rhythmic basin succession of marly limestones and shales (upper Szydlówek Beds) at Kostomloty, western Holy CrossMts., 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, 1.6m thick. The faunal assemblage is dominated by pyritized shells of diminutivemollusks 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 Szydlówek 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

Disrupted continental environments around the Devonian-Carboniferous Boundary: introduction of the tener event

Recent refinements of the palynological stratigraphic scheme around the Devonian-Carboniferous Boundary in southern Belgium result in new questions on the effect of the Hangenberg Biocrisis on spores and on the validity of some ‘biozones’. Verrucosisporites nitidus, the guide taxa of the last Devonian palynozone (LN zone) is lacking in many sections and its presence is only acknowledged in proximal settings. Hence the LN zone is considered as an ecozone rather than a biozone. Moreover, investigation of the uppermost part of the uppermost Famennian shows that the palynological assemblages is dominated by abnormal forms of Retispora lepidophyta, notably by R. lepidophyta var. tener which seems to be characteristic of this interval in Western Europe. It is thus proposed to introduce the global tener event as a potential marker of the Hangenberg Biocrisis on land and in proximal marine settings. This profusion of abnormal spores is thought to be related to climatic variation possibly in link with global cooling below the Devonian-Carboniferous Boundary

The Frasnian-Famennian brachiopod extinction events: a preliminary review

Preliminary review of taxonomy of the brachiopod order Atrypida and its stratigraphic distribution in the late Frasnian Kellwasser Crisis of several regions of Laurussia, western Siberia and South China point to their moderate diversity and stepdown but irregular extinction pattern. The distinctive character of the late Frasnian atrypid fauna is emphasised by several relict genera, marked by recurrent and possibly aberrant characters (mainly in ornamentation types), tendency to size reduction and homeomorphy in some taxa. The transgressive/hypoxic Lower Kellwasser Event and preceding eustatic changes during the Palmatolepis rhenana Zone had only a regional destructive effect, and were linked rather to an enhanced dispersal of the last generic set of atrypids. The Variatrypinae, Spinatrypinae and Iowatrypa-group seem to belong to the latest surviving atrypids. The final demise of the remaining atrypids (and some other articulate brachiopods, e.g., gypidulids) coincided with the transgressive/hypoxic Upper Kellwasser Event, followed by catastrophic eustatic fall during the late Palmatolepis linguiformis Zone (F-F Event). This was probably exacerbated by accelerated submarine volcano-hydrothermal activity, and consequent progressive regional eutrophication, and climatic destabilization. The level-bottom rynchonellid-inarticulate biofacies crosses the fatal F-F boundary horizon without major changes. No reliable data exist for the presence of atrypids in the Famennian survival and recovery biota, even for the smooth lissatrypid Peratos. Sustained competition from radiating and diversiffing productid-cyrtospirifrid-athyrid faunas may have provide an additional biotic factor in the collapse of the Frasnian shelly benthos at the time of stress, as well as in a post-extinction offshore repopulation from inner shelf habitats

Biostratigraphic and structural research in the Guedelhinha–Lançadoiras–Algaré sector in the context of the geology of the Neves–Corvo mine region, Iberian Pyrite Belt

ABSTRACT: Based on drill hole sampling and sedimentary rock dating by palynology, the present research focuses on the palynostratigraphic events established in the key geological section of Guedelhinha–Lançadoiras–Algaré located in the Portuguese Neves–Corvo mine region, Iberian Pyrite Belt. The age data allow detailing the lithostratigraphic sequence and further understanding the complex structural setting, representing an important contribution to the geological knowledge of this sector located to the immediate WNW of the Neves–Corvo VMS deposit. The combination of the studied events allows the reconstruction of the Devonian-Carboniferous sedimentation and paleoenvironments along the Iberian Pyrite Belt. Several stratigraphic hiatuses identified in the Neves–Corvo region by the palynological record are confirmed, mainly occurring from the mid Frasnian to mid Famennian, from the early and mid Strunian, and from the early to late Tournaisian, which were mainly coincident with the worldwide extinction events, in particular during Frasnian–Famennian and Late Devonian times. Extensional tectonics and related gravitational faults, local uplift mechanisms and intense volcanic activity could also explain the lack of palynological data and sedimentary hiatus. In this research, the importance of the late Strunian times in the Iberian Pyrite Belt (Miospore Biozone LN of the Neves Formation) is highlighted, confirming the contemporaneity of felsic volcanism, hydrothermalism, sulphide mineralization precipitation and black shale anoxic sedimentation.info:eu-repo/semantics/acceptedVersio

Extent and duration of marine anoxia during the Frasnian– Famennian (Late Devonian) mass extinction in Poland, Germany, Austria and France

Abstract – The intensity and extent of anoxia during the two Kellwasser anoxic events has been investigated in a range of European localities using amultidisciplinary 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 conditionswere developed (for example, in the basins of the Holy 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