Paleoenvironment in Jorband Section, North of Iran

The study of planktonic foraminifera in Jorband section reveals two major events in Campanian- Maastrichtian boundary and early-late Maastrichtian bio-diversification. In this study, occurrence and species richness of planktonic foraminifera in Jorband area show the warm marine environment dominant during early to late Campanian and it could be correlating by tropical and subtropical biozones. The warm condition converted to rapid cooling exactly in Campanian-Maastrichtian boundary. This rapid changing in temperature was not important effecting in extinction species but make important differences in number of species. Increasing the heterohelicids populations associated with surface dwellers and decreasing of globigerinids show the rapid regression in Jorband area in the Campanian-Maastrichtian boundary. The cooler condition is dominated during early Maastrichtian, whereas heterohelicids were associated by rugoglobigerinids and globigerinelloids. In the late Maastrichtian, abundances of double-keeled species show high sea level and warmer condition dominated in Jorband area in Planoglobulina brazoensis zone (CF5) and Racemiguembelina fructicosa zon