Geology of recently recognized lithologies inside the Red Bed Series in the Chwarta-Mawat area, Kurdistan Region, NE-Iraq

Abstract

The sequence of the coastal siliciclastic facies of the Paleocene-Eocene Zagros Foreland Basin is well exposed in the Chwarta-Mawat area, north of Sulaimani Governorate, northeastern Iraq. According to previous studies, this sequence is designated as Red Beds Series (RBS), consisting of more than 2000 m of fine and coarse red and grey clastics. The present study found recently recognized lithologies (RRLs) about 100 thick inside the series and encompassed green marlstone with subsidiary detrital limestone which has significant tectonic and paleogeographic results. The petrography, biostratigraphy, and boundary conditions studies are applied to uncover their origin. The new lithologies are deposited in the subsiding basin in the Imbricate Zone during the Middle Eocene. During this age, the Tertiary Foreland Basin was separated by a paleohigh into two basins, (northern and southern basins). In the northern basin, the RRLs have deposited as deep facies of the Naopurdan Formation while in the southern basin the Pila Spi Formation was deposited as lagoonal facies. The former formation was deposited as reefal facies in the shelf area of the northern basin to the northeast Chawrta and Mawat Towns. The RRLs, units one and two of the series (in the Thrust Zone) are correlated respectively with Pila Spi, Sinjar and Gercus formations in the High Folded Zone. These correlations are shown on the stratigraphic columns and paleogeographic models with the aid of nannofossil and benthonic foraminiferal studies. This study is the most important step for solving the tectonic and paleogeographic setting of northeastern Iraq and for a better understanding of the Zagros Collisional belt.