Campanian and Maastrichtian Biostratigraphy and Paleoenvironment in Jorband Section, North of Iran

The study of planktonic foraminifera in jorband section reveals two majorevents in campanian- maastrichtian boundary and early-late maastrichtian biodiversification.in this study, occurrence and species richness of planktonicforaminifera in jorband area show the warm marine environment dominant duringearly to late campanian and it could be correlating by tropical and subtropicalbiozones. the warm condition converted to rapid cooling exactly in campanianmaastrichtianboundary. this rapid changing in temperature was not importanteffecting in extinction species but make important differences in number ofspecies. increasing the heterohelicids populations associated with surface dwellersand decreasing of globigerinids show the rapid regression in jorband area in thecampanian-maastrichtian boundary. the cooler condition is dominated duringearly maastrichtian, whereas heterohelicids were associated by rugoglobigerinidsand globigerinelloids. in the late maastrichtian, abundances of double-keeledspecies show high sea level and warmer condition dominated in jorband area inplanoglobulina brazoensis zone (cf5) and racemiguembelina fructicosa zone(cf4).