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TitleSequence and tectonostratigraphy of the Neoproterozoic (Tonian-Cryogenian) Amundsen Basin prior to supercontinent (Rodinia) breakup
AuthorThomson, D; Rainbird, R HORCID logo; Krapez, B
SourcePrecambrian Research vol. 263, 2015 p. 246-259, Open Access logo Open Access
Alt SeriesEarth Sciences Sector, Contribution Series 20130363
PublisherElsevier BV
Mediapaper; on-line; digital
File formatpdf
NTS77B; 77C; 77D; 87A; 87C; 87D
AreaAmundsen Basin
Lat/Long WENS-116.0000 -107.0000 70.0000 68.5000
Subjectstectonics; stratigraphy; tectonostratigraphic zones; tectonic interpretations; tectonic setting; tectonic environments; tectonic evolution; lithostratigraphy; subsidence; crustal evolution; crustal movements; sedimentary rocks; carbonate rocks; Jago Bay Formation; Minto Inlet Formation; Wynniatt Formation; Shaler Supergroup; Precambrian; Proterozoic
Illustrationslocation maps; stratigraphic sections; photographs
ProgramGEM: Geo-mapping for Energy and Minerals PGE/Base Metals - Victoria Island (NWT and Nunavut)
AbstractIntracontinental basins lack obvious compartments and extensional faults, however they often lie inboard of, and have the same timing as rifted continental margins. Neoproterozoic successions of NW Laurentia are an example where rift basins and intracontinental basins have a similar spatial and temporal relationship.
Tonian-Cryogenian strata of the Jago Bay, Minto Inlet and Wynniatt formations, part of the upper Shaler Supergroup were deposited in the intracontinental Amundsen Basin. This study is the first sequence stratigraphic description of pre-rift strata from the Amundsen Basin, where five, third-order sequences, defined by maximum surfaces of regression, subaerial unconformities, and shoreline ravinement surfaces, are now identified. Sequences are interpreted as third-order, transgressive-regressive cycles, however their genesis is open to interpretation. The pre-breakup succession in the Amundsen Basin has sequence architectures that differ from adjacent fault-bound rift basins. There is little evidence for progradation, which resulted in broad layer-cake stratigraphy where shallow-water facies predominate, deposited on a gently sloping ramp. Assignment of subsidence mechanism is difficult, however the identification of sequences and subsidence patterns prior to break-up of Rodinia has implications for understanding sequence architecture.
Correlation of third-order sequences between the Amundsen and Fifteenmile basins is compromised by differing rates and regimes of subsidence. However, we propose that the upper Shaler Supergroup and Little Dal Group of the Mackenzie Mountains Supergroup are equivalent to the entire Fifteenmile Group. Analysis of pre-rift strata in the Amundsen Basin supports multi-phase, non-correlative break-up of Rodinia along the NW-margin of Laurentia.
Summary(Plain Language Summary, not published)
The manuscript presents a new sequence stratigraphic framework for early Neoproterozoic sedimentary rocks of the upper Shaler Supergroup, which was deposited in the intracontinental Amundsen Basin of northwestern Canada, before the break-up of supercontinent Rodinia. Discussion of the hierarchy of sedimentary sequences as well as patterns and generation of basin subsidence have implications for understanding the stratigraphic architecture of similar basins. Revised sequence stratigraphic and tectonic correlations with sedimentary rocks and structures in the northern Cordillera are presented. This study supports multi-phase, non-correlative break-up of Rodinia along the NW-margin of Laurentia, the cratonic core of North America. This work is relevant and timely paper because of recent publications on the sedimentology, sequence stratigraphy, stable isotope stratigraphy, and geochronology of both the Amundsen and adjacent basins and adds perspective on the evolution of Rodinia from a more interior (within Laurentia) vantage point.

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