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TitleThe Santonian-Campanian boundary positive carbon isotope excursion and Late Cretaceous climatic trends Pacific coast Canada
AuthorZakharov, Y D; Haggart, J W; Beard, G; Safronov, P P
Source9th International Symposium on the Cretaceous System, abstract book; 2013 p. 49
Alt SeriesEarth Sciences Sector, Contribution Series 20130117
Meeting9th International Symposium on the Cretaceous System; Ankara; TR; September 1-5, 2013
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
ProgramGeoscience for New Energy Supply (GNES), Frontier basin analysis
ProgramGeoscience for New Energy Supply (GNES), Frontier basin analysis
AbstractThis study presents oxygen and carbon isotope fluctuations identified in well-preserved ammonite and bivalve fossils of the Upper Cretaceous Nananimo Group from Vancouver and Hornby islands. 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 some regions. The lack of laminated black shales at the Santonian-Campanian boundary interval in British Columbia, with associated heavy d13C values, seems to be in agreement with the idea that most of the world's oceans were characterized by oxygen-rich, but not anoxic, deep waters during Coniacian-Campanian time. Palaeotemperatures for the late Santonian-Campanian of British Columbia, determined on the basis of oxygen isotopic analysis, suggest a direct 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 (11.3-26.4oC) and the bivalve Inoceramus sp. (about 19.7oC), 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 33.7oC, which we assume to represent the regional expression of the early Campanian warming event.
Summary(Plain Language Summary, not published)
This contribution is a conference presentation of results to be published in a scientific journal paper on the same topic. Potential hydrocarbon-bearing sedimentary rocks preserved in southwest British Columbia contain isotopes of oxygen and carbon molecules that are related to biological productivity and climatic patterns during Late Cretaceous time, about 85-65 million years ago. The new data show that the sedimentary rocks are rich in organic matter and could potentially have served as a source rock for hydrocarbons. Warming and cooling trends documented by the isotopic succession are similar to global patterns and 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.