Two cores from the central Caribbean (cores A254-BR-C and CP-28), which include older Pleistocene sediments, have been analyzed by the O18/O16 method. Core A254-BR-C has been dated, in part, by C14 and Pa231/Th230 measurements. Both apparently contain major hiatuses, but their stratigraphy has been clarified by correlations among the isotopic temperature curves and the curves representing the percentages of right-coiled specimens of Globorotalia truncatulinoides, together with correlations among the core levels where Globorotalia menardii flexuosa disappears and among other levels where Globorotalia truncatulinoides becomes rare. The generalized temperature curve, previously constructed, has been extended to an estimated age of 375,000 years ago, but the extension should not be considered generally valid until substantiated by isotopic analysis of suitable cores as yet not available.
The methods used by Ericson, Ewing, Wollin, and associates, for estimating past temperatures from the micropaleontology of deep-sea cores, and the correlations advocated between deep-sea and continental stratigraphies are critically reviewed.
The evidence provided by cores A254-BR-C and CP-28 adds to the contention that the repeated glaciations of the Pleistocene were triggered by summer insolation minima in the high northern latitudes.