NWT RESEARCH DATABASE

Regions: Dehcho Region

Tags: physical sciences, geology, paleontology, stratigraphy, fossil coral reefs

Objective(s): To examine the settlement, development and decline of the fossil corals as a response to environmental conditions in the Liard region during Mississippian to Early Pennsylvanian times (358.9 to 314.6 million years ago).

Project Description: The principal aim of this project is to examine the settlement, development and decline of the fossil corals as a response to environmental conditions in the Liard region during Mississippian to Early Pennsylvanian times (358.9 to 314.6 million years ago). The study will be conducted against the background of the worldwide expansion of corals in the Viséan age (346.7 - 330.9 million years ago) and their decline in numbers and species diversity at the end of the Serpukhovian age (323.2 Ma). The particular objectives include a study of post-mortem changes to the corals, taxonomy (naming of fossils), stratigraphy (study of layered sedimentary rocks), study of depositional environments, and establishment of the geographic distribution of the corals. Determining the depositional environments will involve evaluating the ancient sedimentation conditions and settings including water depth, sea-surface temperature, bottom conditions and processes, and the sources (provenance) and amounts of sand and silt. In the field area, the research team plan to measure and describe two or more stratigraphic sections through the Banff, Flett, Golata and Mattson formations. The section measurement will involve determining the thicknesses of packages of layered sedimentary rock at outcrops. The most important section is at Jackfish Gap, there the research team will measure the thickness of the Flett, Golata, and Mattson formations. The team plan to measure other stratigraphic sections including the ones at Bluefish and Jackfish mountains. By measuring the sections, the team will obtain samples and basic stratigraphic and sedimentologic data. Measurement of several sections will permit the team to evaluate regional and vertical lithological and paleoenvironmental trends. For section measurement, the will use tape measures and 1.5 m long telescopic poles (Jacob staves) divided into 10 cm intervals. As the sections are measured, the team will sample them for fossils (mainly corals, brachiopods, and microfossils called conodonts) and representative rock samples (mainly fist size and smaller) for geochemistry and petrographic work (study of rock with microscopes). Sampling will have a negligible impact on the environment because only hand-held equipment will be used, trenches will not be excavated, and no holes will be drilled. The research team will identify and describe the best fossil corals collected in the field. At the Institute of Geology in Poznan, thin sections and serial peals will be made from the corals and they will examine and describe them. The research team will make thin sections from representative limestone and sandstone samples to facilitate their identification and determine their clast composition and textures. The thin-section analyses of limestone will be used to determine environments of deposition. The stable carbon and oxygen isotopes (d13C and d18O) trends will be analyzed within the measured sections using brachiopod shells and powder derived from systematically collected limestone samples. The isotopic analyses will be obtained at the Isotope Dating and Environment Research Laboratory in Warsaw. Resulting graphs showing trends in isotope values (d13Ccarbonate and d18Ocarbonate) will be compared with available Carboniferous isotope curves from other parts of the world. The resulting graphs will be treated as records of changes of sea-surface temperature and rates of carbon sequestration. The research team will publish results of the project in widely available geological journals. The team also plan to communicate the results at scientific conferences. As for the talks for communities in the NWT – if people in local communities are interested in the work, the team could give a summary presentation at a meeting of the tribal councils in Fort Liard and Fort Simpson. The research team could also discuss geological aspects of the region that are of specific interest to First Nations People. Presentations about geology and fossils in the local schools are also possible if there is interest. The fieldwork for this study will be conducted from July 4, 2019 to August 1, 2019.