Critical analysis of the type section of the Balambo Formation (Valanganian-Turonian), Sirwan valley, Kurdistan Region, NE-Iraq

Volume 1 , Issue 1 , January 216 , Pages 189-202

Authors

¹ Department of Geology, University of Sulaimani, Sulaimani City

² Institutions for strategic studies and scientific research-Sulaimani City

The Balambo Formation (Garau Formation in Iran) and its equivalents such as Shuaiba,

Qamchuqa and Mauddud are very significant formations since they occur nearly in all oil

fields in Iraq and Iran. The first definition of its type section was carried out in 1947 in

the Sirwan Valley on the southwestern limb of the Balambo Anticline, about 11 km to

the southwest of Halabja town, 3 km to the east of Kawta village. In the present study,

the first definition is critically analyzed in the field and laboratory by foraminifera and

nannofossils aging. The analysis shows many problems in the thickness, stratigraphy,

location and its relation to Kometan and Shiranish formations. Many structural and

topographic characteristics (of the section) are shown to prove that the thickness of the

type section is less than that indicated previously in the first definition. In the definition

of the type locality, the Kometan Formation was not recorded, while the present study

confirms its occurrence, with a thickness of about 80 m.. The lithological and

Paleontological studies showed that the Kometan Formation has the age of Turonian –

Late Campanian and has conformable contact with both Balambo and Shiranish

formations. This does not coincide with the definition, which did not mention the

Kometan Formation and recorded the presence of erosional unconformity (missing

sediment of Santonian-Middle Campanian) under Shiranish Formation. The location of

the type section is not clear and it is combination of the three different sections in three

different areas which are located in the imbricated Zone. Topographically and

structurally, the section is so complex that a nowadays geologists will never think to

select it as a type section for definition a stratigraphical units.

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