Iraqi National Journal of Earth Science

ABSTRACT
Lepidocyclina(Nephrolepidina) kirkukensis a new Foraminifera is recorded
from the Late Oligocene Baba Formation (Kirkuk and Bai-Hassan Oil
Fields, North Iraq). The new species is described and figured based on
variations in (Ai, C and α ) parameters in agreement with the principles of nepionic acceleration as defined by Tan Sin Hock. The paleoenvironment of the Lepidocyclina (Nephrolepidina) kirkukensis is concluded as shallow marine according to the lithological features and faunal association.

The Sangaw region is located at the western part of Zagros orogenic belt at the boundary between Low and High Folded Zones, Sulaimani governorate in Kurdistan region. The area characterized by low amplitude folds that are trending northwest southeast and arranged in en echelon pattern. The exposed formations are Eocene Pila Spi (limestone), middle Miocene Fat`ha(lagoon) and Upper Fars (clastics) formations. Many large and small sinkholes are found around Ashdagh anticline; some of them about 50 m in diameter and about 30 m deep. Some are developed into complicated cave systems with collaps blocks and breccias in addition to narrow passages and fissures. The largest of them is located directly to the west of Darzilla village at the southeastern plunge of Ashdagh anticline. The sinkholes occur in Fat`ha and in the Pila Spi Formations. The walls of the sinkholes are covered by secondary gypsum, sulfur, bitumen and secondary calcite. Inside the cave collapse, breccias and blocks with lensoidal stratified clayey sediments as weathering product could be seen. The water is acidic (pH=4) inside the caves and discharges as large spring (200L/S) with white milky color; it is called in the local Kurdish language, “Awa Spi “which means white stream. The weathering of the carbonate rocks is intense inside the cave and appears as honeycombs and rills mark which have very rough surface with dull color. The sinkholes were produced from the dissolution of thick gypsum and limestone beds. The origin of these caves has been proposed to be hypogenic speleogenesis due to the presence of gypsum and bitumen. These materials with the aid of bacteria enrich the water with H2S which aciditfies the water and precipitates the sulfur
and secondary gypsum on the cave wall. The formation of H2SO4 by oxidaton of
H2S is the main reason that aid the sinkhole hypogene generation in Sangaw area.
A realistic model is drawn to interpret and connect the following:
1- The stratigraphy and structure of the area encourage the generation of underground stagnant pond suitable for reacting with the emanating H2S necessary for the hypogene generation of the sinkholes and precipitation of secondary native sulfur and gypsum.2- dissolution of gypsum and its reduction by bacteria. 3- upward migration of bitumen from nearby oil traps(hydrocarbon accumulation).

ABSTRACT
Eight samples of Shiranish Formation were obtained from Balad well No. 8, (northern Baghdad) central Iraq. Details investigated carried out identify calcareous nannofossils, where identified sixteen species; eleven descried from other region and five left under open name because of lack of material or rare of samples, On the basis of stratigraphic distribution of the species, two biozones proposed these are :

Recently a new lithology is found at the middle part of Tanjero Formation (Maastrichtian) and consists of a bluish marl succession about 100m thick in Sulaimayia area. This succession is lithologically similar to Shiranish Formation and has nearly same color and stacking pattern which didn’t described in the original description in the type section of Tanjero Formation. Geographically
it can be seen in Piramagroon and Sharazoor plains, Chaqchaq valley
(to the northwest of Sulaimani City) and Dokan area. The biostratigraphy of this succession indicates Early Maastrichtian to Early Late Maastrichtian which includes four interval zones of:
Racemiguembelina fructicosa Interval Zone (CF4) (Early late Maastrichtian), Pseudotextularia intermedia Interval Zone (CF5) (Early Maastrichtian)
Contusotruncana contusa Interval Zone (CF6) (Early Maastrichtian)
Gansserina gansseri Interval Zone (CF7) (Early Maastrichtian)
As concerned to the affinity of this succession two possibilities can be assigned:
1-Middle part of Tanjero Formation.
2-lentils of Shiranish Formation inside Tanjero Formation.
This study prefers the first assignation as the foraminiferal assemblages show that the marly succession is not belonging to Shiranish which has, in the studied area, the age of Campanian. Another reason for this assignation is that the environment and sequence stratigraphy, tectonics of Tanjero Formation is more understandable than the first assignation (If it is included in the Shiranish Formation). The record of this new lithology and submergence of the type section of the formation under the water of Darbandikhan (dam) impose selection of a new type section or a supplementary type section for the formation either in Dokan or Chwarta areas where there are representatives of the new lithology inside the Tanjero Formation and the sections are well exposed.