The Kuibis Subgroup (~551- <547.36 Ma) in the Nama Basin records an important fauna assemb... more The Kuibis Subgroup (~551- <547.36 Ma) in the Nama Basin records an important fauna assemblage change during the Ediacaran. Current models support a transition from a more diverse ‘White Sea’ biotic assemblage to a less diverse ‘Nama’ biotic assemblage, for which the drivers remain unresolved. In spite of this decrease in diversity, the Nama assemblage hosts the first appearance of metazoan biomineralization in the geologic record. High resolution chemostratigraphic data are required to globally anchor the timeline of Earth System changes leading to this innovation of life. In order to track these changes at high-resolution, we performed a sampling campaign of Namibian cores from the ICDP project ‘Geological Research through Integrated Neoproterozoic Drilling: The Ediacaran-Cambrian Transition’ (GRIND-ECT), which focuses on terminal Ediacaran stratigraphy of the Witputs and Vioolsdrif sub-basins of southern Namibia. Here we present new Carbon and Oxygen isotope data for carbonate rocks of the Kuibis Subgroup retrieved from drill core 1G. This core records an approximately 200 m-thick succession of mixed carbonate-siliciclastic sedimentary rocks of that unit. Both dolostones and limestones within the lowermost 100 m display negative δ13C values between -5 and 0 ‰, consistent with laterally-correlative outcrop data that record the Basal Nama Excursion (BANE). The oxygen isotope profile recorded in core 1G is also very distinctive throughout the BANE. It starts with a negative shift of the δ18O values from -5 to -15 ‰, which then progressively increase to values around -12 ‰. The uppermost 100 m of core 1G display a gradual increase in δ13C values that reach +5 ‰ and are accompanied by increasing δ18O values that approach -10 ‰. The 0 ‰ crossing point (carbon isotope value) occurs at ~90 m depth, below strata that confidently record the first appearance of fossils of biomineralizing animals. Magnesium isotopic and paleontological data added to our high-resolution carbon isotope profile have the potential to refine the knowledge about the biological and environmental changes of this time period.
The Neoproterozoic-Paleozoic transition was marked by profound modifications in the Earth-Life sy... more The Neoproterozoic-Paleozoic transition was marked by profound modifications in the Earth-Life system, as evidenced by intense perturbations in biogechemical cycles and the appearance of complex macroscopic life. Many questions remain regarding the relationship and feedback between the biotic and abiotic processes that operated in that period, particularly the interconnections between changes in paleoclimate, tectonics, and the biological evolution. Here we present new geochemical data for the Nama Group, South Namíbia, sampled as part of the ICDP GRIND (Geological Research through Integrated Neoproterozoic Drilling) project, a global scientific collaboration that aims to study, in an integrated and multidisciplinary way, different sedimentary sequences in Namibia, China and Brazil, which encompass the terminal Ediacaran and the base of the Cambrian. Our sampling was carried out in the entire stratigraphic interval of the Nama Group in a 5 m resolution, always respecting the variations in facies and fossiliferous content and avoiding highly disturbed strata. X-ray fluorescence analyses were conducted 745 samples through a portable XRF device. The preliminary results of major elements, such as Si, Al, Ti, Sr and Ca, show major environmental shifts in the stratigraphic column, usually reflecting facies variations. The preliminary data presented herein is of key importance for the subsequent studies in the drill cores of the GRIND project, comprising geochronology, isotope analyses and paleontology.
The Kuibis Subgroup (~551- <547.36 Ma) in the Nama Basin records an important fauna assemb... more The Kuibis Subgroup (~551- <547.36 Ma) in the Nama Basin records an important fauna assemblage change during the Ediacaran. Current models support a transition from a more diverse ‘White Sea’ biotic assemblage to a less diverse ‘Nama’ biotic assemblage, for which the drivers remain unresolved. In spite of this decrease in diversity, the Nama assemblage hosts the first appearance of metazoan biomineralization in the geologic record. High resolution chemostratigraphic data are required to globally anchor the timeline of Earth System changes leading to this innovation of life. In order to track these changes at high-resolution, we performed a sampling campaign of Namibian cores from the ICDP project ‘Geological Research through Integrated Neoproterozoic Drilling: The Ediacaran-Cambrian Transition’ (GRIND-ECT), which focuses on terminal Ediacaran stratigraphy of the Witputs and Vioolsdrif sub-basins of southern Namibia. Here we present new Carbon and Oxygen isotope data for carbonate rocks of the Kuibis Subgroup retrieved from drill core 1G. This core records an approximately 200 m-thick succession of mixed carbonate-siliciclastic sedimentary rocks of that unit. Both dolostones and limestones within the lowermost 100 m display negative δ13C values between -5 and 0 ‰, consistent with laterally-correlative outcrop data that record the Basal Nama Excursion (BANE). The oxygen isotope profile recorded in core 1G is also very distinctive throughout the BANE. It starts with a negative shift of the δ18O values from -5 to -15 ‰, which then progressively increase to values around -12 ‰. The uppermost 100 m of core 1G display a gradual increase in δ13C values that reach +5 ‰ and are accompanied by increasing δ18O values that approach -10 ‰. The 0 ‰ crossing point (carbon isotope value) occurs at ~90 m depth, below strata that confidently record the first appearance of fossils of biomineralizing animals. Magnesium isotopic and paleontological data added to our high-resolution carbon isotope profile have the potential to refine the knowledge about the biological and environmental changes of this time period.
The Neoproterozoic-Paleozoic transition was marked by profound modifications in the Earth-Life sy... more The Neoproterozoic-Paleozoic transition was marked by profound modifications in the Earth-Life system, as evidenced by intense perturbations in biogechemical cycles and the appearance of complex macroscopic life. Many questions remain regarding the relationship and feedback between the biotic and abiotic processes that operated in that period, particularly the interconnections between changes in paleoclimate, tectonics, and the biological evolution. Here we present new geochemical data for the Nama Group, South Namíbia, sampled as part of the ICDP GRIND (Geological Research through Integrated Neoproterozoic Drilling) project, a global scientific collaboration that aims to study, in an integrated and multidisciplinary way, different sedimentary sequences in Namibia, China and Brazil, which encompass the terminal Ediacaran and the base of the Cambrian. Our sampling was carried out in the entire stratigraphic interval of the Nama Group in a 5 m resolution, always respecting the variations in facies and fossiliferous content and avoiding highly disturbed strata. X-ray fluorescence analyses were conducted 745 samples through a portable XRF device. The preliminary results of major elements, such as Si, Al, Ti, Sr and Ca, show major environmental shifts in the stratigraphic column, usually reflecting facies variations. The preliminary data presented herein is of key importance for the subsequent studies in the drill cores of the GRIND project, comprising geochronology, isotope analyses and paleontology.
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