Similarities and Differences of Orbitoides & Omphalocyclus Microspheric Forms with Selected Examples from Northern Iraq and Turkey and Their New Morphometric Data

  • Muhittin GörmüşEmail author
  • Qahtan Ahmed Al Nuaimy
  • Engin Meriç
Conference paper
Part of the Advances in Science, Technology & Innovation book series (ASTI)


Aqra Formation sediment outcrops are widespread in the northern Iraq. There are different formations in various localities of Turkey which contain rich Orbitoides and Omphalocyclus genera. Megalospheric (A) forms are particularly predominant in the Campanian-Maastrichtian aged siliciclastic and carbonate sediments. External and internal parameters of both genera are correlated in selected specimens to bring out differences and similarities especially on microspheric forms of Orbitoides and Omphalocyclus. New morphometric data on more than one hundred individual equatorial thin sections from the carbonate samples of the Aqra Formation show that microspheric individuals of Omphalocyclus include semicircular equatorial chamberlets at the initial part. On later parts thick walled rectangular shaped chamberlets are shown. In contrast, microspheric individuals of Orbitoides mainly comprise semicircular and semi rectangular equatorial chamberlets. Biometrical data on the Orbitoides tests from the Aqra Formation show population abundance of Orbitoides megaloformis and O. gruenbachensis.


Aqra Formation N Iraq Turkey Orbitoides Omphalocyclus Biometry 


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© Springer Nature Switzerland AG 2019

Authors and Affiliations

  • Muhittin Görmüş
    • 1
    Email author
  • Qahtan Ahmed Al Nuaimy
    • 2
  • Engin Meriç
    • 3
  1. 1.Engineering Faculty, Geology DepartmentAnkara UniversityAnkaraTurkey
  2. 2.Northern Technical University/Technical CollegeKirkukIraq
  3. 3.Moda Hüseyin Bey SokakIstanbulTurkey

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