The (Hellnmaria-Red Tops Boundary) HERB negative excursion is well known from the deep water, distal slope deposits at the Green Point section, western Newfoundland, Canada. However, the absence of fossils prohibits the precise biostratigraphic constraint of the HERB excursion at the Green Point section. The deeper water strata at the nearby Martin Point South section represent middle to distal slope deposition and are here used to present the continuous carbon-isotope stratigraphy for the upper part of the Furongian Series in the allochthonous Cow Head Group, western Newfoundland, Canada. The Furongian strata are characterised by moderate to low sedimentation rates and the investigated succession at the Martin Point South section provides a complete sedimentary record. The Furongian strata are referred to the Martin Point Member of the Green Point Formation of the Cow Head Group and consist of black, dark grey and green shale, ribbon lime mudstone and grey, brown weathering siltstone. A total of 33 samples were microdrilled from the most micritic material and analysed for carbon isotope geochemistry from the lower part of the succession (ca 58 m thick) at Martin Point to reconstruct a δ13C profile. The most striking carbon-isotope anomaly detected is the HERB isotope carbon excursion with a clear double peak at the base of the Eoconodontus notchpeakensis conodont Zone. Up section, the HERB is succeeded by a second significant negative excursion in the lower middle part of the E. notchpeakensis Zone and the isotope curve of the E. notchpeakensis Zone concludes with a positive carbon isotope event that marks the beginning of the Cordylodus proavus conodont Zone. The HERB excursion is well developed, complete and biostratigraphically constrained in the Martin Point South section, thus it forms an important proxy for regional and intercontinental correlation and for the discussion on the base of unnamed Stage 10.
The Cambrian HERB excursion (Furongian) from the Martin Point Formation of the Cow Head Gropu, western Newfoundland, Canada.
BAGNOLI, GABRIELLA;
2016-01-01
Abstract
The (Hellnmaria-Red Tops Boundary) HERB negative excursion is well known from the deep water, distal slope deposits at the Green Point section, western Newfoundland, Canada. However, the absence of fossils prohibits the precise biostratigraphic constraint of the HERB excursion at the Green Point section. The deeper water strata at the nearby Martin Point South section represent middle to distal slope deposition and are here used to present the continuous carbon-isotope stratigraphy for the upper part of the Furongian Series in the allochthonous Cow Head Group, western Newfoundland, Canada. The Furongian strata are characterised by moderate to low sedimentation rates and the investigated succession at the Martin Point South section provides a complete sedimentary record. The Furongian strata are referred to the Martin Point Member of the Green Point Formation of the Cow Head Group and consist of black, dark grey and green shale, ribbon lime mudstone and grey, brown weathering siltstone. A total of 33 samples were microdrilled from the most micritic material and analysed for carbon isotope geochemistry from the lower part of the succession (ca 58 m thick) at Martin Point to reconstruct a δ13C profile. The most striking carbon-isotope anomaly detected is the HERB isotope carbon excursion with a clear double peak at the base of the Eoconodontus notchpeakensis conodont Zone. Up section, the HERB is succeeded by a second significant negative excursion in the lower middle part of the E. notchpeakensis Zone and the isotope curve of the E. notchpeakensis Zone concludes with a positive carbon isotope event that marks the beginning of the Cordylodus proavus conodont Zone. The HERB excursion is well developed, complete and biostratigraphically constrained in the Martin Point South section, thus it forms an important proxy for regional and intercontinental correlation and for the discussion on the base of unnamed Stage 10.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
