Pollen grains of Angiosperms in the Cenomanian Peruc formation in Bohemia

Abstract

Pollen grains of angiosperms found in the Cenomanian Peruc Beds in Bohemia belong to several morphological groups and represent the terrestrial, paludal and aquatic plants. They involve both the monocotyledon (Monoporopollenites, Monocolpopollenites) and dicotyledon (Tricolpopollenites, Tricolporopollenites, Triporopollenites, Polyporopollenites, Normapolles) trees and herbs. The pollen spectrum, however, is characterized by smooth and sculptured tricolpate and tricolporate pollen grains whose percentage greatly prevails. In the lower layers of the Peruc Beds there are mainly small (10-18µ) tricolpate and tricolporate forms, the larger forms appearing in the upper part of the complex. Changes in the composition of spectrum are observable already during the sedimentation of the 25 m thick formation. Therefore, it cannot yet be excluded whether the lower part of the Peruc Beds does not fall still in the Albian. Most recent investigation has shown that the development of the progressive angiosperm element, termed. by Pflug "Normapolles", which prevails in and is characteristic of the pollen spectrum of the Upper Cretaceous, started in the Cenomanian. In the Peruc Beds primitive forms of this group appear sporadically but quite regularly, and from the top layers a representative showing a more advanced morphology has been recovered. The discrepancies in the results of macropalaeobotanical and palynological investigations led the authoress to the revision of some classic macropalaeobotanical studies (by HEER, VELENOVSKY, VINIKLAR, BAYER). By the example of the fossil genus "Eucalyptus Heel", whose identity with the modern genus Eucalyptus has been disproved (B. PACLTOVA, 1962), she has shown that it is advisable to revise some earlier determinations by means of modern integrated methods, now available.