The First Record of a Representative of the Toarcian Early Aalenian Belemnites in Kimberlites of the Obnazhennaya Pipe (Northeastern Siberian Platform)
A rostrum fragment of a representative of the ToarcianEarly Aalenian (the latest Early Jurassicthe earliest Middle Jurassic) belemnites Arcobelus cf. krimholzi (Sachs, 1970) was found for the first time in kimberlites of the Obnazhennaya pipe of the Kuoika kimberlite field (northeastern Siberian Platform, Olenek Uplift). It was shown that the belemnite records previously known here and dated to the Late Jurassic or Early Cretaceous may be of BajocianBathonian (Middle Jurassic) age. The stage of kimberlite magmatism of 177 1.5 Ma, recently established in the northeastern part of the Siberian craton according to UPb geochronological data, falls on the time of the existence of belemnites of the genus Arcobelus. The estimated Late BajocianEarly Bathonian age of the representative of the genus Pachyteuthis, previously found in kimberlites of the Obnazhennaya pipe, is consistent with the 40Ar/39Ar age (167 Ma), as well as with the age based on some paleomagnetic data (168 11 Ma) reported for the pipe. Taking into consideration the new data on belemnites, the internal part of the shelf should be extended to the territory of the Kuoika kimberlite field in the paleogeographic schemes of the northeastern part of the Siberian Platform during the ToarcianEarly Bathonian.
