FORAMINIFERAL BIOSTRATIGRAPHY AND PALEOECOLOGY OF THE MAASTRICHTIAN THROUGH DANIAN SEDIMENTS OF THE ZIARAT-KOLA SECTION, CENTRAL ALBORZ MOUNTAINS, IRAN

To reconstruct the Maastrichtian through lower Danian biostratigraphy of northern Iran, 212 meters of the Ziarat-Kola section in the central Alborz Mountains was sampled. The sequence is comprised of monotonous grey-green to light grey marl the lower contact of which is a disconformity, while the upper contact is uncertain. Sixty-five species belonging to 28 genera were identified and seven biozones were described. Following the research of Li, Keller, Bolli and Shutskaya the biozones include 1) a Racemiguembelina fructicosa biozone, 2) a Pseudoguembelina hariaensis biozone, 3) a Pseudoguembelina palpebr biozone, 4) a Parvularugoglobigerina eugubina biozone, 5) a Parasubbotina pseudobulloides biozone, 6) a Subbotina triloclinoides biozone, and 7) a Globonomalina compressa-Preamurica inconstans biozone. An age of Maastrichtian through lower Danian is assigned to the section based upon these species. Four major episodes indicating changes in oxygen abundance and productivity were determined based upon the benthic foraminifera morphogroups, these include from bottom to top: Episode 1) Low oxygen and high food supply with an infauna to epifauna morphotype ratio of 1.5; Episode 2) with an infauna to epifauna ratio of 1 indicating intermediate oxygen and food supply; Episode 3) with increasing infauna and decreasing epifauna indicating low oxygen and high food supply; and Episode 4 with an infauna to epifauna ratio of .11 indicating high oxygen and low food supply. These episodes reflect major changes in the ecology of the marine environment including water depth and continental sediment contribution.