Calcareous nannofossil biostratigraphy and depositional history of the late Cretaceous to early Miocene sequence of Iraq
This thesis presents a new calcareous nannofossil based zonation scheme for Iraq based upon the examination of 515 drill cutting, conventional core and bit samples from both southern and northern Iraq. This zonation consists of 13 zones and 7 subzones covering the Late Cretaceous to Early Miocene. To date no detailed nannofossil zonation scheme was available for Iraq and therefore the nannofossil zonation presented here breaks new ground. The new zonation scheme has also been successfully correlated with the established global calcareous nannofossil zonation schemes of Martini (1971), Okada and Burky (1980) and Varol (1989). In addition, this zonation has been correlated with nannofossil zonation schemes applied in other Middle Eastern countries. These correlations have enabled Iraq to be put into a global and regional stratigraphic framework. The new zonation scheme has also been integrated with global planktonic foraminiferal zonation schemes and both planktonic and benthonic foraminiferal zonation schemes previously produced for Iraq. This was done to assess the dates previously assigned to the formations being analysed during this study. The new nannofossil scheme has also been correlated with the magnetobiostratigraphic timescale so that the timing of tectonic events, the duration of hiatuses and sedimentation rates could be assessed for the study area. This information has been used to refine the existing sediment deposition models believed to be active in Iraq during the time period studied. Finally, concentrations of certain nannofossil groups noted in the study area during particular time periods are explained with reference to regional and global environmental conditions associated with local salinity changes and global warming and cooling.