The Ingta Formation is a geological unit containing green sandstones and shales; it crops out in the Canadian Mackenzie Mountains.[2] Its age is poorly constrained, though it straddles the Precambrian/Cambrian boundary.[1] Below the boundary its ichnofauna comprises subhorizontal Planolites burrows; above it, Phycodes burrows immediately appear, with Nemakit-Daldyn SSFs appearing soon after.[1]
| Ingta Formation | |
|---|---|
| Stratigraphic range: | |
| Type | Geological formation |
| Thickness | up to 312 metres (1,020 ft) |
| Lithology | |
| Primary | Interbedded Shale & Sandstone |
| Other | Subordinate limestone units |
| Location | |
| Country |  Canada |
Stratigraphy
editThe formation is overlain by either the Backbone Ranges Formation and the Vampire Formation, depending on the locality. These two formations have a common base with the Ingta formation, and both continue onwards until the base of the Sekwi Formation. [3]
Depositional environment
editThe rocks are submarine, and were deposited in a nearshore to offshore location on the continental shelf, with no freshwater influence evident—although overlying units bear evidence of deltaic and braided river deposits.[4]
Palaeontology
editThe formation has yielded a range of SSFs including eggs and embryos, anabaritids, Protohertzina, Zhejiangorhabdion, and phosphatized tubes, spines and plates.[5]
References
edit- ^ a b c Narbonne, G.; Aitken, J. (1995). "Neoproterozoic of the Mackenzie Mountains, northwestern Canada". Precambrian Research. 73 (1–4): 101–121. doi:10.1016/0301-9268(94)00073-Z.
- ^ Baudet, D.; Aitken, J. D.; Vanguestaine, M. (1989). "Palynology of uppermost Proterozoic and lowermost Cambrian formations, central Mackenzie Mountains, northwestern Canada". Canadian Journal of Earth Sciences. 26 (1): 129–148. Bibcode:1989CaJES..26..129B. doi:10.1139/e89-011.
- ^ Dewing, K; Sharp, R J; Ootes, L; Turner, E C; Gleeson, S (2006). Geological Survey of Canada, Current Research (Online) no. 2006-A4. ISBN 978-0-662-43134-3.
- ^ MacNaughton, R.; Dalrymple, R.; Narbonne, G. U. Y. (1997). "Early Cambrian braid-delta deposits, Mac Kenzie Mountains, north-western Canada". Sedimentology. 44 (4): 587. doi:10.1046/j.1365-3091.1997.d01-41.x.
- ^ Pyle, L. J.; Narbonne, G. Y. M.; Nowlan, G. S.; Xiao, S.; James, N. P. (2006). "Early Cambrian Metazoan Eggs, Embryos, and Phosphatic Microfossils from Northwestern Canada". Journal of Paleontology. 80 (5): 811. doi:10.1666/0022-3360(2006)80[811:ECMEEA]2.0.CO;2.
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