Sequence stratigraphy of the upper cretaceous Tanjero formation, Eastern Darbandikhan, Northern Iraq

With this sequence stratigraphy aimed study, spectacularly exhumed Campanian- Maastrichtian deep marine turbidities of Tanjero Formation near eastern part of Darbandikhan, to the northeastern part of Iraq was examined. A 1333 m thick sedimentary measured section was logged in detail for this study located near Iranian border at Sirwan valley nearby Sarshata village, to the east of the Darbandikhan town. The log starts from lower contact of the formation underling Campanian- Maastrichtian Shiranish Formation and finishes at the upper contact overlying Paleocene-Middle Eocene Kolosh Formation. From the shale intervals of the log 25 samples were collected and analyised containing deep marine microfossils. Abathomphalus, Gansserina, Globotruncana, Globotruncanita, Heterohelix, Hedbergella, Pseudotextularia, Pseudoguembelina, Racemiguembelina, Rugoglobigerin genera and 17 species of planctonic foraminifera along the logs were found. Late Maastrichtian Abathomphalus mayaroensis zone and bathyal environment have been identified by assemblage of the planktonic foraminifera, and Krithe sp. Ostracode genus has been identified in the uppermost level of the log which has been used for identifying infraneritic bathyal environment for the study area. Palaeoflow data measured from flute marks and clast imbrications and analyised on a rose diagram show that the flow direction was toward the SW. This means the source area of the formation was located to the NE. Sequence stratigraphy in term of parasequence and parasequence sets has been studied depending on the grain sizes and bed thickness changings along the measured log indicate that the formation includes third-order depositional systems. In the study area stratigraphic succession of the formation is separated into two (lower and upper sequences) depositional successions. Around 15% thickness of the Tanjero Formation is deposited in the lower sequence which contains Highstand Systems Tract (HST) resulted in progradational to aggraditional parasequence. Approximately 85% thickness of the formation belongs to the upper sequence; the upper sequence is bounded by (sequence boundary 1) SB1 in the lower part and (sequence boundary 2) SB2 in the upper part. The upper sequence comprises Lowstand Systems Tract (LST), Transgressive Systems Tract (TST) and Highstand Systems Tract (HST) resulted in progradational paracequence, Retrogradational parasequence and progradational to aggraditional parasequence respectively. These parasequence data indicate that the sea level during the late Maastrichtian starts with high level (HTS), after that falls (LTS), then arises again with a transgression (TST), then keeps its level (HST) for a while for the study area. Keywords: Sequence Stratigraphy, Late Cretaceous, Tanjero Formation, Darbandikhan, northeastern Iraq.