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TitleLate Cretaceous climatic trends and a positive carbon isotope excursion at the Santonian-Campanian boundary in British Columbia, northeastern Pacific
AuthorZakharov, Y D; Haggart, J W; Beard, G; Safronov, P P
SourceSedimentary Geology vol. 295, 2013 p. 77-92,
Alt SeriesEarth Sciences Sector, Contribution Series 20130061
Mediapaper; on-line; digital
File formatpdf
ProvinceBritish Columbia
NTS92B/13; 92C/16; 92F/01; 92F/02; 92F/08; 92G/04
AreaVancouver Island; Duncan; Nanaimo
Lat/Long WENS-125.0000 -123.5000 49.5000 48.7500
Subjectspaleontology; geochronology; Upper Cretaceous; Campanian; Santonian; fossils; fossil distribution; fossil assemblages; paleotemperatures; isotopes; carbon isotopes; Paleozoic; Cretaceous
Illustrationslocation maps; stratigraphic columns; tables; photographs; photomicrographs; charts; plots
ProgramFrontier basin analysis, Geoscience for New Energy Supply (GNES)
AbstractThis study presents oxygen and carbon isotope data obtained from well-preserved ammonite and bivalve fossils of the Upper Cretaceous Nanaimo Group of southwestern British Columbia, Canada. Palaeotemperatures for the late Santonian-Campanian of British Columbia, determined on the basis of oxygen isotopic analysis, suggest a õdirect relationship with basic Late Cretaceous climatic trends (e.g. temperature fall toward the cool climates of the Maastrichtian). The coolest Campanian palaeotemperatures were calculated from the ammonite Pachydiscus cf. ootacodensis (Stoliczka) (11.3 - 26.4 °C) and the bivalve Inoceramus vancouverensis Shumard (about 19.7 °C), from the late Campanian Occidentalis Zone (Northumberland Formation). In contrast, the highest palaeotemperatures were obtained from the shells of presumed earliest Campanian bivalves and varied between 25.1 and 33.7 °C, which we assume to represent the regional expression of the early Campanian warming event.
The Santonian-Campanian boundary in British Columbia is associated with a positive d13C excursion (to 4.2permil) which appears to be contemporaneous with the Santonian-Campanian Boundary Event reported recently from other regions (i.e., Europe, Tunisia, Japan, and Tibet). The lack of organic-rich laminated black shales (indicating strong oxygen depletion in the marine realm) through the Santonian-Campanian of the Nanaimo Group, including the Santonian-Campanian boundary interval, seems to be in agreement with the suggestion that most of the world's oceans were characterised by oxygen-rich deep waters during Coniacian-Campanian time.
Summary(Plain Language Summary, not published)
Potential hydrocarbon-bearing sedimentary rocks preserved in the Georgia basin of southwest British Columbia contain isotopes of oxygen and carbon molecules that are related to biological productivity and climatic patterns during Late Cretaceous time, approximately 85-65 million years ago. The new data show that the sedimentary rocks of southwest British Columbia are rich in organic matter, which could potentially have served as a source for the development of hydrocarbons. Warming and cooling trends documented by the succession of these isotopes in the rocks of Georgia basin are similar to global patterns and such patterns can be used to more precisely correlate the rocks of southwest British Columbia with those of Europe and elsewhere in the Pacific Ocean basin. The new isotopic data help to better understand the history of accumulation of potential oil and gas-bearing strata of the western Canada region, enhancing petroleum industry understanding of these sedimentary basins and serving to focus exploration efforts.