Upper Cretaceous Planktonic Foraminifera from the Putah Creek Subsurface Section along the Yolo-Solano County Line, California

• Main Author: Takayanagi Yokichi
• Format: Report
• Language: English
• Published: Tohoku University 1965
• Subjects: Forbes; Planktonic foraminifera
• Online Access: http://hdl.handle.net/10097/28779; https://tohoku.repo.nii.ac.jp/?action=repository_uri&item_id=11976; https://tohoku.repo.nii.ac.jp/?action=repository_action_common_download&item_id=11976&item_no=1&attribute_id=18&file_no=1

The Upper Cretaceous planktonic Foraminifera from the Putah Creek subsurface section are described, and six local concurrent-range zones are proposed on the basis of their stratigraphic distributions. The subsurface section of the Upper Cretaceous along the Putah Creek on the Yolo-Solano County line, in the southwestern part of the Sacramento Valley, comprises seven formations, the Forbes, Guinda, Funks, Sites, Yolo, Venado and one unnamed one in descending order. From these formations 36 planktonic species are discriminated, including one new to science. The species belonging to Heterohelix, Gublerina, Globigerinelloides, Schackoina, Hedbergella, Praeglobotruncana, Globotruncana and Rugoglobigerina are described, illustrated and their stratigraphic ranges are ascertained. As the result six foraminiferal zones are defined by the overlapping ranges of the planktonic forms, and they are correlated with the stages of the European standard as follows : Globotruncana imbricata zone with the lower Turonian, Globotruncana fornicata/Globotruncana coronata zone with the upper Turonian, Hedbergella loetterli zone with the lower Coniacian, Globotruncana schneegansi zone with the upper Coniacian, Globotruncana area zone with the Santonian, and the Globotruncana subcircumnodifer zone with the Campanian. A marked change in the planktonic foraminiferal components is recognized before and after the upper Globotruncana schneegansi zone. In this respect, some paleoecological considerations are given based upon the sedimentary environment and climate as related with the change in planktonic species stock. Consequently a change of the sedimentary environment was accompanied with a reduction of the marine area during the later phase of that zone and local prevalence of colder water since the post-Globotruncana schneegansi zone.