Znaczenie geologiczne ryncholitów

Abstract

Geological value of Ryncholites For the determination of age the value of rhyncholites is rather low. The group of Rhyncholithes allows only to distinguish between the Triassic, the Jurassic and Cretaceous taken together, and the Tertiary. The group of Rhynchoteuthis allows to distinguish seven zones in the time from the Middle Pliensbachian to the Barremian (Fig. 5) throughout the Western Tethys. On the other hand, rhyncholites are very good indices of faunal provinces. From the Bajocian to the Aptian inclusively the tearing and piercing forms of Rhynchoteuthis are limited to the Tethys; the crushing forms occur much more frequently in the Tethys than in the adjoining epicontinental areas. The ryncholites have not been hitherto found in the Mesozoic of the Boreal and Circumpacific realms. It seems that rhyncholites are also good bathymetric indices. The tearing and piercing forms of Rhynchoteuthis have been hitherto found exclusively in facies considered to be deep water. In the radiolarites and nodular limestones the specimens of ryncholites are mostly directed with their lower surface upwards, thus providing a top-and-bottom criterion.