NWT RESEARCH DATABASE

Regions: Sahtu Settlement Area

Tags: sedimentary rocks, Neoproterozoic

Objective(s): To investigate three of the most intriguing questions of the Neoproterozoic Era (1000-541 million years ago, Ma) by performing a field-based examination of sedimentary rocks in the Mackenzie Mountains of Northwest Territories. These questions include: 1) what are the stratigraphic expressions and significance of the Bitter Springs and Shuram carbon isotope excursions (CIEs); 2) did environmental conditions or biological composition shape the morphology of the first complex reefs on Earth?; and 3) why did the first morphologically complex animals (“Ediacaran Biota”) apparently appear in the deep ocean?

Project Description: This licence has been issued for the scientific research application No. 5717. This proposal aims to investigate three of the most intriguing questions of the Neoproterozoic Era (1000-541 million years ago, Ma) by performing a field-based examination of sedimentary rocks in the Mackenzie Mountains of Northwest Territories. These questions include: 1) what are the stratigraphic expressions and significance of the Bitter Springs and Shuram carbon isotope excursions (CIEs); 2) did environmental conditions or biological composition shape the morphology of the first complex reefs on Earth?; and 3) why did the first morphologically complex animals (“Ediacaran Biota”) apparently appear in the deep ocean? The researchers will attempt to answer these questions by studying spectacularly exposed sedimentary rocks along two extremely well-preserved shelf-to-slope transects. These paleo-water depth transects will be constructed by linking together rock exposures that span the length of the Mackenzie Mountains, arguably the best place in the world to conduct such a study. From an educational perspective, the results will shed light on the history of the rocks in Northwest Territories and the relationship between environmental change and biotic evolution both in northwestern Canada and globally. The proposed research is to investigate the Neoproterozoic Little Dal and Rackla groups at several locations in the Mackenzie Mountains over the course of five summers (2022–2026). These camps were selected based on preliminary field data collected in 2011 and 2014, which began to establish a stratigraphic record across a proximal shelf-to-slope succession of marine sediments. Fieldwork will be completed between June 15th and August 15th each year, as this is the best time to work in the high mountainous terrain. The researchers plan to spend at least 6-7 days at each location listed in the proposal, in additional to several days in Whitehorse and/or Norman Wells before and after fieldwork to organize gear and ship samples to/from our respective institutions. Many potential camp sites have been included to give flexibility on what localities we visit and how the final logistics work out for access into the field area. Ideally, all these sites will be visited at least once over the course of the five-year project. Herein, the Mackenzie Mountains are separated into three broad regions: southern, central, and northern Mackenzies, each of which has a unique access point. In the southern Mackenzie Mountains (Thundercloud Ranges, Backbone Ranges, and Coppercap Mountain Camps, Fig. 1), we propose to access the field areas by helicopter from Tungsten, NWT, or through a fixed-wing aircraft to Root River (in collaboration with South Nahanni Outfitters) and then via helicopter organized through the local outfitter. In the central Mackenzie Mountains (Sekwi Brook, Moosehorn River, Rouge Mountain, June Lake, Sekwi Brook, Godlin River, and Boomerang Lake, Fig. 1), The researchers propose to access the field area with a helicopter from Mac Pass at the end of the Canol Highway. Finally, we propose to access the northern Mackenzies (Tawuia and Table Top/Table East Reefs and Shale Lake Camp) via helicopter from Norman Wells. The researchers propose to establish a lightweight, helicopter-based fly camp in each location and subsequently carry out all fieldwork on foot from the respective basecamp. At each location, field work will consist of mapping geological strata on topographic maps and measuring stratigraphic sections by describing sedimentary strata meter by meter. Additionally, small samples of carbonate rock will be collected at ~1 meter intervals for carbonate carbon and oxygen isotope chemostratigraphy and redox-sensitive metal isotope geochemistry, to be analyzed at the various listed institutions. Lastly, the researchers will collect both volcanic rocks for U-Pb geochronology, and Neoproterozoic body- and trace-fossils (preserved on small centimeter-scale sedimentary rock fragments called talus) if they are discovered while working. The stratigraphic location and sedimentological context in which these fossils are being preserved will also be recorded. All rock samples to be collected are normal rock samples with no aesthetic or commercial value. We will attempt to minimize the amount of sample being removed and use our rock hammers as little as possible. In addition, easily accessible broken or fractured outcrops will be targeted to avoid excessive hammer use. This proposed work is highly remote and does not take place in any NWT communities. The only community we will travel through is Norman Wells. We propose to be in constant communication with members of the Northwest Territories Geological Survey (whom are already aware of our proposed activities – please contact Beth Fischer for any questions), as well as any other institutions recommended by the Aurora Institute. We will most certainly abide by any and all guidelines set forth in our permit application with respect to public or government engagement. The fieldwork for this study will be conducted from: June 25 - August 15, 2024