STUDY OF MIOGYPSINIDS (OLIGOCENE-MIOCENE) IN THE KIRKUK AREA, NORTHEASTERN IRAQ

Abstract

This study examines well-exposed outcrops and subsurface successions of bioclastic limestone from the Qara Chaugh–Dagh and Khabaz Well-3 sections in the Kirkuk area, northeastern Iraq. The carbonates were deposited within a shallow, open-marine setting during the Oligocene–Miocene (Chattian–Aquitanian). Larger foraminifera belonging to the Miogypsinidae are abundant throughout both the lower and upper parts of these carbonate sequences. Detailed biometric and morphological analyses of Miogypsinids indicate that the oldest representatives of the genus Miogypsina occur in the lower part of the Qara Chaugh–Dagh section, while the Khabaz Well-3 sequence is characterised by Miogypsinoides complanata and M. formosensis. Early Miocene assemblages dominated by Miogypsina s.s. are commonly associated with Miogypsinoides, many of which are closely related to M. bantamensis. Based on mean embryonic size, two distinct assemblage types of Miogypsinoides are recognised within the Early Aquitanian sediments: Type I, possessing a smaller embryon (D₁ = 120–135 µm) similar to African associations, and Type II, with a larger embryon (D₁ = 210–230 µm) comparable to European assemblages. These results provide new insight into the biostratigraphic and palaeobiogeographic distribution of Miogypsinids in the Zagros Basin and contribute to refining correlations across the Oligocene–Miocene boundary in the Middle East.