Sequence Development and Engineering Geological Survey of the Nfayil and Injana Formations in Abdulla Abo- Najam area Al-Qadissiya Governorate (Middle of Iraq)

Abstract

Surface sections of the Nfayil Formation (Middle Miocene) and Injana Formation (Upper Miocene) are studied in Abdulla Abo-Najam area Al-QadissiyaGovernorate Middle of Iraq. The Nfayil Formation consists of marls interbedded with limestones and marly limestone while the Injana Formation consists of alternating sandstones, siltstones and claystone. The Nfayil Formation is deposited mainly within the restricted, shoal and shallow open marine conditions. While Injana Formation is deposited in meandering river. Seven 4th order cycles can be recognized within the Nfayil- Injana succession in the study area. These cycles are asymmetrical and each represent period of sea level rise following episode of stillstand. A type two sequence boundary (SB-2) occurs between the Nfayil Formation and the Injana Formation. This succession is developed in an area of low subsidence, which reflects the major effect of eustacy as the main controlling factor in sequence development. Engineering Geological Survey results showed that the uniaxial compressive strength of rocks in the study area ranges from the maximum value of 36 N/mm2 in Nfayil Formation, to the minimum value of 8 N/mm2 in Nfayil Formation, and the average is 22.865 N/mm2 depending on the point load index (Is)., in the study area the uniaxial compressive strength is classified into very low to low uniaxial compressive strength.