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TitleStratigraphic unconformities: review of the concept and examples from the Middle-Upper Palaeozoic
AuthorKabanov, P
SourceSeismic and Sequence Stratigraphy and Integrated Stratigraphy; by Aiello, G (ed.); Stratigraphy 2017 p. 101-128, https://doi.org/10.5772/intechopen.70373
Year2017
Alt SeriesNatural Resources Canada, Contribution Series 20170095
PublisherInTech
Documentserial
Lang.English
Mediapaper; on-line; digital
File formatpdf
ProvinceAlberta; Northwest Territories
AreaAthabasca oil sands; Mackenzie Valley; Peel area
Subjectssurficial geology/geomorphology; regional geology; general geology; stratigraphy; unconformities; stratigraphic models; stratigraphic traps; disconformities; biostratigraphy; paleosols; erosion; vadose zones; subsurface geology; Devonian; Carboniferous
Illustrationslocation maps; stratigraphic columns; photographs; core logs; tables
ProgramWestern Arctic Project Management, GEM2: Geo-mapping for Energy and Minerals
Released2017 12 06
AbstractOnly about 10% of the geologic time is imprinted in sedimentary strata, and the rest is hidden in non-deposition or erosion surfaces called unconformities. Stratigraphic unconformities (disconformities) are principal bounding surfaces in sequence stratigraphy which a geologist would easily identify in the outcrop but dubiously in the subsurface unless core is available. Proportion of mis-identified and overlooked disconformities in subsurface stratigraphy is quite large, which puts a warning sign on simplistic sequence stratigraphic models. Time imprinted in disconformities can be evaluated with relative weathering maturity of the subaerial profile, cyclostratigraphic calibration, absolute dating, and biostratigraphy. However, using biostratigraphy alone is never enough as biostratigraphic gaps tend to fill with increasing data coverage. Identification of paleo-vadose zones and subaerial exposure profiles is regarded critical for finding stratigraphic unconformities and is the only approach in strata where geophysically mappable fluvial systems are absent. Drowning unconformities are carbonate-platform drowning surfaces that usually produce distinct reflection horizons and have better stratigraphic value in the subsurface than platform-embedded subaerial unconformities. This discussion is supported by examples of subaerial disconformities from the Devonian, Carboniferous, and Permian of Canada and Russia and with an example of a geographically extensive mid-Devonian drowning unconformity from Northwestern Canada.
Summary(Plain Language Summary, not published)
Only about 10% of the geologic time is imprinted in sedimentary strata, and the rest is hidden in non-deposition or erosion surfaces called unconformities. Stratigraphic unconformities (disconformities) are principal bounding surfaces in sequence stratigraphy which are readily identified in outcrop but not so readily in the subsurface. Proportion of overlooked disconformities in subsurface is quite large. Time imprinted in disconformities is evaluated with relative weathering maturity, cyclostratigraphy, absolute dating, and biostratigraphy. However, using biostratigraphy alone is never enough. Drowning unconformities are carbonate-platform drowning surfaces that usually produce good reflection horizons and have better stratigraphic value in the subsurface than subaerial unconformities. This discussion is supported by examples of subaerial disconformities from the Devonian, Carboniferous, and Permian and with an example of a mid-Devonian drowning unconformity from Northwestern Canada.
GEOSCAN ID302712