Abstract
ABCTRACT Twenty-one surface samples from Avanah Formation dating to Middle Eocene cropping out in Dohuk area, northern Iraq, were studied for their nannofossils with light microscope .The study shows that the formation contains a rich and varied assemblage of nannofossils with a significant development of special forms such as Discoasters and Coccolithes . These forms are useful as stratigraphic indicators in Paleogene sediments and as paleoecological indicators of the studied area. One of these samples had being studied by Scanning Electron Microscope to show some of the diagnostic features of the studied species. The study resulted in the recognition of (12) species belong to (10) genera of calcareous nannofossils. ـــــــــــــــــــــــــــــــــــــــــــ ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ ــــــــ ـــ ةسا رد ةیفینصت ل ضعب عاونأ تا رجحتم ونانلا ةیسلكلا نیسویلال طسولأا / لامش لا ي قا رع
Highlights
In recent years more attention have been paid to the abundant, widely distributed and rapidly evolved calcareous nannofossils .Since the size of these fossils is less than 63 micron, its diagnostic featuers can only be seen under Scanning Electron Microscope which has become more widely available and greatly enhanced the study of nannofossils
Much of the work on the fine structure and formation of these fossils has been made possible by scanning electron microscope
Calcareous nannofossils can be used to help determine the paleotemperature and current patterns of ancient oceans, following Perch –Nielsen (1985) Sphenolithus species are characteristic of low latitude, open sea and warm waters, where as Pontosphaera species are frequent in hemipelagic sediments, both genera as well as Discoasters are well represented in the studied section
Summary
In recent years more attention have been paid to the abundant, widely distributed and rapidly evolved calcareous nannofossils .Since the size of these fossils is less than 63 micron , its diagnostic featuers can only be seen under Scanning Electron Microscope which has become more widely available and greatly enhanced the study of nannofossils. 1984 Discoaster barbadiensis Tan Sin Hok-El-Dawoody and Elewi; 2 No 4, 365 - 382, pl. Occurrences: This species was recorded throughout middle Eocene of USA Bukry (1975), Egypt Eldawoody (1992), Iraq Al-Badrani (2011). Discoaster elegans Bramlette and Sullivan, 1961 Pl. 1, Fig .1
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