Mitchell, Simon F.; Blissett, Donovan
Author Affiliation, Ana.
Department of Geography and Geology
The Cretaceous-Paleocene Summerfield Formation, Jamaica: One or two ignimbrites?
Caribbean Journal of Science
Date of Publication
The stratigraphic succession through the Summerfield Formation (Cretaceous-Paleocene) has previously been interpreted from sections exposed along the road from Guinea Corn to Johns Hall on the northern side of the Central Inlier in Jamaica. Two ignimbrite horizons had been recognised, and the upper one dated as Late Paleocene. Our mapping of this area of the Central Inlier demonstrates that the Summer-field Formation can be divided into 4 units: S1 , thinly bedded calcareous sandstones; S2 , thickly bedded sandstones; S3 , conglomerates with interbedded sandtsones; and S4 , ignimbrite. Along the road from Guinea Corn to Johns Hall, the ignimbrite (S4) is found in the core of a syncline. The apparent existence of two ignimbrites in the Summerfield Formation is the result of interactions between the folding and the course of the road. In fact, there is only one ignimbrite which has been clearly demonstrated by field mapping. The Summerfield Formation is also important in regard to the Cretaceous-Tertiary boundary question in Jamaica, for it overlies the Maastrichtian Guinea Corn Formation and the ignimbrite S4 is of Late Paleocene age. This suggests that the Cretaceous-Tertiary boundary lies either between the Guinea Corn and the Summerfield Formations or within the lower part of the Summerfield Formation.....