Planktonic Foraminiferal Biostratigraphy and Faunal Turnover across the Cretaceous-Tertiary Boundary in Southwestern Iran

TitlePlanktonic Foraminiferal Biostratigraphy and Faunal Turnover across the Cretaceous-Tertiary Boundary in Southwestern Iran
Publication TypeJournal Article
Year of Publication2007
AuthorsDarvishzad, B, Ghasemi-Nejad, E, Ghourchaei, S
JournalJournal of Sciences, Islamic Republic of Iran
Volume18
Issue2
Pagination39-149
Type of ArticleUniversity of Tehran
KeywordsCretaceous-Tertiary Boundary; Biostratigraphy; Plankton foraminifera
Abstract

The Kabirkuh section in the Ilam Province of southwestern Iran contains one of the most complete Late Maastrichtian to early Danian sequences similar to those known from the eastern Tethys realm. The Cretaceous-Tertiary boundary is marked by a 1-2 cm thick kidney-red shale in the uppermost Gurpi Formation. All Late Maastrichtian planktonic foraminiferal biozones CF1 to CF4 (equivalent to the Abathomphalus mayaroensis zone) and Danian zones P0 (Parvularugo-globigerina extensa), P1a (Parvularugoglobigerina eugubina) and Parasubbotina pseudobulloides are present. Faunal studies show that all but six of the Cretaceous species identified (22 of 29 species) disappeared at or below the K-T boundary in zone CF1 (P. hantkeninoides). Another 6 species (Heterohelix globulosa, H. navarroensis, H. dentata, Hedbergella monmouthensis, H. holmdelensis, Guembelitria cretacea) appear to have survived into the early Danian. Early disappearances appear to be environmen tally controlled. Coarse ornamented species with small populations disappeared first, whereas small species with little or no ornamentation and generally large populations tended to survive after the environment changing. This indicates a pattern of gradual and selective faunal turnover in planktonic foraminifera during the latest Maastrichtian and into the earliest Danian that is similar to that observed at the El Kef stratotype of Tunisia, as well as K-T sequences in Egypt, Italy, Spain and Mexico.  PDF

URLhttp://jsciences.ut.ac.ir