Stratigraphic value of Discoasters and some other microfossils related to Recent coccolithophores

Abstract

Much scientific work has been done on Recent Coccolithophoridae and some fossil forms have been described, but little attention has been given to their value in biostratigraphy. Some largely extinct forms which may be closely related to these minute algae have been known under the generic term Discoaster. The systematic position of the discoasters is uncertain; originally Ehrenberg re- garded them as inorganic "Crystalldrusen," but it is now evident that they are the skeletal remains of nannoplanktonic organisms. Despite the little taxonomic work done and the difficulties involved, present data indicate the probability that the discoasters, especially, may aid in world-wide correlation of certain Tertiary time horizons. The very small (about 10 microns) calcareous remains of these organisms are common in some late Mesozoic and Tertiary rocks, particularly in those of open-sea deposition, and constitute the main bulk of some chalky sediments. Distinctive forms characteristic of certain parts of the Tertiary are found on both sides of the Pacific and Atlantic oceans, including the Caribbean and Mediterranean regions, and elsewhere. Some of these are described and some data presented on their strati- graphic distribution.