CARBON ISOTOPE (δ13CCARB) CHARACTERIZATION OF LES CANEUVES SECTION, SE FRANCE, AND CORRELATION WITH OAE 1A IN THE ALPINE TETHYS

A section from the Bedoulian substage consisting of yellow and grayish limestones at Les Caneuves, SE France, partially coeval with the La Bédoule section [1-4] was analyzed for TIC, TOC, carbon and oxygen isotopes, and microfacies. SEM and EDS analyses further provided microstructures and elemental composition of the minerals that constitute predominately the calcareous matrix, including scarce dispersed pyrite in small clusters, and quartz. TIC ranges from 86.9 to 92.0 CaCO₃ wt%, whereas TOC varies from 0.13 to a high 0.74 wt% and the values are in inverse correlation with TIC. Macrofossils include very rare ammonites at intermittent levels. The most abundant allochemical constituents throughout the beds are very small planktonic (rare G. blowi) and benthic foraminifera, rare echinoid spines, ostracods, and some traces of organic matter (no more than 1%), in a micrite matrix indicative of a pelagic or hemipelagic environment. The carbon isotope (δ¹³C_carb) values fluctuate from 1.29 to 1.95.

Correlation with previously studied sections within the Tethyan areas [1, 3-8] that include the well-known scheme of carbon isotope segments [5] associated with Lower Aptian successions shows values correlative with carbon isotope segment C3 [5], at the onset of oceanic anoxic event 1a (OAE1a) or “Goguel”/“Livello Selli ” equivalent [5]. The Chemostratigraphic correlation thus supports a chronologic position within the Early Aptian coeval with the G. blowi zone.

References

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