A study of paleotemperatures of the post-Aptian Cretaceous, using the oxygen isotope method for measuring temperatures, is here reported. The investigation, an elaboration of the initial exploratory one reported earlier (Urey et al., 1951), was made by using belemnite guards, Inoceramus, brachiopod and oyster fragments, chalks, and bioclastic matrix materials. The samples were collected primarily from western European localities and from the southeastern part of the United States. A few samples were from Greenland, Japan, Australia, India, and Algeria. The results indicate a progressive rise in ocean temperatures from the Cenomanian, climaxing in the Coniacian-Santonian, followed by a general decline to the Maestrichtian. This climatic history is particularly evident from the many belemnite data and corroborated by the data for the other associated burial elements. The validity of temperatures measured by the use of various fossils is evaluated from the point of view of the preservation of original skeletal material and from considerations of what fraction of local temperature amplitude is recorded by different forms. The study also indicates that during the Coniacian-Santonian temperature climax, marginal subtropical ocean temperatures extended northward into the present-day cold-temperate belt, with this northward displacement decreasing toward Maestrichtian time. It appears from the belemnite data and from the paleogeographical distribution of belemnites in the post-Aptian Cretaceous that the belemnites became stenothermal following Albian times. A study of the temperatures recorded by the unusually well-preserved elements of the Maestrichtian Coon Creek assemblage from Tennessee permitted a comparison with the recorded temperatures of the present-day Bermuda biota. A parallelism between the temperatures recorded by these two faunal assemblages appears to be present.
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Nov 1, 1969
A Longinelli 
