An integrated study of upper Campanian-lower Maastrichtian carbon isotopes and calcareous plankton biostratigraphy of the Kurdistan Region, northeastern Iraq

作者：Farouk Sherif^*; Thibault Nicolas; Jaff Rawand B N; Faris Mahmoud; Ahmad Fayez; Khashaba Ahmed

来源：Cretaceous Research, 2018, 82: 64-80.

DOI：10.1016/j.cretres.2017.09.020

• Late Cretaceous
• Plankton diachronism
• Eastern Tethys

New carbon (delta C-13) isotope records calibrated by planktonic bioevents provide general support for a late Campanian age assignment of the Shiranish Formation (Fm.) and its boundaries in the Dokan section (NE Iraq). The Shiranish Fm. is characterised at the base by a mid-Campanian unconformity as can be interpreted by absences of nannofossil zones CC20-21. The Shiranish Fm. then spans nannofossil bio-zones CC22-CC23a (UC15d-e(TP) to UC16a(TP)). Results obtained on carbon isotopes suggest that diagenesis affected and compromised a few carbonate samples in the uppermost 50 m of the section. However, once these samples are discarded, pristine trends suggest that the top of the section records a negative carbon isotope excursion that is interpreted as CMBa-c events that straddle the Campanian-Maastrichtian boundary. This interpretation is supported by the lowermost occurrence of planktic foraminifers Rugo-globigerina scotti and Contusotruncana contuse some 30 m above the base of the negative excursion and 10 m below a positive excursion identified as the Maastrichtian M1+ event. Discrepancies in the strat-igraphic range of several planktic foraminifer bioevents are highlighted and advocate for the need of many more integrated records of planktic foraminifer and nannofossil biostratigraphy alongside carbon isotope stratigraphy in the eastern Tethys in order to improve regional and global schemes.

• 出版日期2018-2