Keywords : Planktic foraminifera
Cretaceous / Paleogene Boundary Analysis by Planktic Foraminiferal Biozonation in the Western Zagros Fold-Thrust Belt (Smaquli valley), Sulaimani Governorate, NE-Iraq
Kirkuk University Journal-Scientific Studies,
2020, Volume 15, Issue 3, Pages 45-81
The current work focuses to study the foraminifera assemblages within the Cretaceous/Paleogene (K/PG) boundary outcropped in the High Folded Zone in Smaquli valley (Gali section), Kurdistan Region, and Northeastern Iraq. The boundary is nearly located between Tanjero and Kolosh Formations and their exposure mainly consists of thick succession of deep marine turbidities (flysch) and hemipelagic sediments. The study aims to indicate biological fossils assemblages and physical expressions that inherited from globally important events of the end of cretaceous. The study has extraited expressions of the well exposed successions of fine grains from which 8 biozones are identified in the uppermost section of Shiranish formation, the Shiranish- Tanjero transition area and the Tanjero formation through biostratigraphy (biozonation) and lithostratigraphic analyses. These zones, from the bottom to top, are upper part of Globotruncana aegyptiaca Interval Zone (CF8), which belongs to Upper part of Shiranish Formation, (Early Maastrichtian) and lower part of Tanjero Formation. The second, third, fourth and fifth zones are Gansserina gansseri Interval Zone (CF7), Contusotruncana contusa Interval Zone (CF6) (Early Maastrichtian) and Pseudotextularia intermedia Interval Zone (CF5), Racemiguembelina fructicosa Interval Zone (CF4) respectively and all belong to lower part of Tanjero Formation (Early Maastrichtian). The sixth, seventh and eighth zones are Pseudoguembelina hariaensis Interval Zone (CF3), Pseudoguembelina palpebra Interval Zone (CF2), Plummerita hantkeninoides Total Range Zone (CF1) respectively that belong to upper part of Tanjero Formation (Late Maastrichtian). Moreover, four biozones of Danian (Early Paleocene) are recorded in the lower part of Kolosh Formation which are Guembelitria cretacea Interval Zone (p0), (base of Danian), Parvularugoglobigerina eugubina Total Range Zone (pα), (base of Danian), Parvularugoglobigerina eugubina-Subbotina triloculinoides Interval Zone (P1a) (Early Danian), Subbotina triloculinoides–Praemurica inconstans Interval Zone (P1b), (Middle Danian). The lithostratigraphic and biostratigraphic study revealed that no physical events (conglomerate, erosional surface, paleosoil and hardground) and has a conformable and gradational existence, which is evidenced by continuous sedimentation of the same sediments and no chronostratigraphic gaps within K / PG boundary. Biologically, it shows the gradual extinction of the Cretaceous planktic foraminifera and the sudden emergence of the Paleogene ones.