The Middle Miocene Fatha (Lower Fars) Formation, Iraq

Abstract

The Middle Miocene Fatha Formation (previously Lower Fars Formation) in northern Iraq was deposited in a broad and shallow foreland basin adjacent to the Zagros and Taurus Mountains. It forms a transgressive-regressive sequence comprising numerous shallowing-upward cycles of alternating mudrocks, limestones, gypsum and/or anhydrite and halite. These cycles reflect rapid changes in accommodation space in settings that ranged from open and restricted hypersaline marine to continental (sabkha and fluvio-deltaic). In the marginal parts of the basin, continental siliciclastics (red and variegated marls, silts and fine sandstones) represent either aeolian deposition or a combined lagoonal- and/or fluvial-dominated delta system. Eustasy, rather than tectonics, caused the high-frequency cyclicity seen in the Fatha Formation. We present twelve sections dominated by evaporites from the Sinjar and Fatha sub-basins to represent the main lithologic constituents of the formation. Our detailed analysis of the sedimentary succession focuses on the three main lithofacies (siliciclastics, carbonates and evaporites). Petrographic, geochemical and scanning electron microscope analysis of these units are presented. We identified a range of carbonate lithotypes: marly, arenaceous (detrital), organic-rich (fossiliferous), dolomitic limestone and dolomite. Dolomitic limestones occur mostly in the lower part of the lower member of the formation, which was deposited in a barred lagoonal environment with high salinity. The presence of peloidal lime-wackestone with bioclasts, particularly in the upper part of the lower member of the formation, may reflect quiet, shallow-water marine conditions with moderate depths and low energy. The bioclastic-peloidal grainstone-packstone microfacies, with a common and diverse fossil assemblage, may reflect high to moderate energy, shallow-water environments. Evaporites comprise the main sediments of the Fatha Formation. Nodular gypsum is the dominant gypsum type, although laminated, thick-bedded, and secondary gypsum (selenite and satin spar) also occur. In the subsurface, anhydrite and halite are the principal minerals.

Paleocene to Miocene southern Tethyan carbonate factories of the Southwestern and Western Central Asia

“…The abundance of non-skeletal facies related to restricted conditions (Flugel, 2004) peaks in the early Miocene and in particular in the Aquitanian. This is also supported by the lithostratigraphic information provided by Al-Juboury and McCann (2008) and Ameen-Lawa and Ghafur (2015) for Iraq, Reuter et al (2009) and Mohammadi et al (2013) for Iran. During the Miocene the convergence between the African-Arabian and Eurasian plate lead to the progressive restriction and then to the closure of the Mediterranean-Indian Ocean Seaway (e.g., Rogl et al, 1998;Robertson et al, 2012).…”

“…1). The Arabian and Levant regions (i.e., the eastern and central part of the study area), during the late Eocene -Oligocene, were also affected by a regional uplift testified by large hiatuses (Alsharhan and Nairn, 1995;Whittle et a., 1995;Buchbinder et al, 2005;Al-Juboury and McCann, 2008;Agard et al, 2011;Avni et al, 2012;Farouk et al, 2013;Bernecker, 2014;Coletti et al, 2019;Sadooni and Alsharhan, 2019). This event has been related to the development of the Afar Dome and the opening of the Red Sea (Ziegler, 2001;Avni et al, 2012;Bernecker, 2014).…”

“…The collision between the Arabian and Eurasian plates probability initiated during the latest Eocene -early Oligocene and was entirely completed before ca. 14 Ma (middle Miocene) (Ballato et al, 2010;Agard et al, 2011;Cornacchia et al, 2018;Bialik et al, 2019;GholamiZadeh et al, 2021), leading to the end of marine sedimentation in most of the Mesopotamian and Iranian regions (i.e., the central part of the study area) during the Miocene (Ziegler, 2001;Al-Juboury and McCann, 2008;Mossadegh et al, 2009;Reuter et al, 2009;Mohammadi et al, 2013;Sissakian, 2013;Ameen-Lawa and Ghafur, 2015;Sadooni and Alsharhan, 2019) (Fig. 1).…”

Mineralogy and Petrography of Fatha gypsum rocks in Zurbatiyah area, eastern Iraq

“…Evaporites form about 50 % of the total thickness of the middle Miocene Fatha Formation in Iraq. [6] the evaporites are wide spread thus It consists essentially of minerals such as gypsum, anhydrite and rock salt such as halite. Fatha Formation characterized by rhythmic nature [1,7].…”

“…The Upper member stated with first appearance of the reddish brown mudstone [7]. Fatha Formation deposted in shallow marine, supra-tidal and lagoonal environments [6,7]. M. O. Ali [8]…”