Evaluation of microfacies, sedimentary environment and original mineralogy of the Garau Formation in Aligudarz section, Lorestan

Since the Garau Formation is important as a source rock in the Zagros sedimentary basin, in this research, tried to identify and introduce microfacies, sedimentary model, and sedimentary geochemistry of this formation in Aligudarz section located in the southeast of Lorestan.

Aligudarz section (southeast of Lorestan) is located in the high Zagros zone and in the geographical range of north latitude 33°04′05″ and east longitude 49°00′17″. To identifying microfacies and sedimentary environment, 235 thin sections were prepared and studied. Also, 40 samples were analyzed by atomic absorption spectrometer (AAS) to determine the range of values of major and minor elements (Ca, Mg, Sr, Na, Mn, and Fe).

The Garau Formation thickness in Aligudarz section is 483 m, and lithology consists mainly of limestone, shale and shaly limestone. The lower boundary of the Garau Formation with brrecia limestones is equivalent to the Gotnia Formation in the form of unconformity and the upper boundary is not clear due to its location in the syncline core. Study of this section microscopic sections led to the identification of 7 microfacies in the deep-sea facies belt. Based on the major and minor elements and the ratio of these elements to each other, original mineralogy composition has been mainly aragonite and have been affected by two types of dissolution in closed and open systems. And also has anoxic conditions or an increase in the effect of meteoric diagenesis. The original mineralogy composition has been mainly aragonite and have been affected by two types of dissolution in closed and open systems. Due to anoxic conditions or an increase in the effect of meteoric diagenesis.

Thickness of this section is 483 meters, and lithology consists mainly of limestone, shale and shaly limestone. The lower boundary of the Garau Formation with brrecia limestones is equivalent to the Gotnia Formation in the form of unconformity and the upper boundary is not clear due to its location in the syncline core.The most important biological components identified in different parts of the Garau Formation include radiolarian, planktonic foraminifera (Globigerinelloides, Hedbergella, Leupoldina). Among the most important non-carbonate compounds are iron oxides.The Garau Formation is formed in the deep-sea facies belt belonging to a ramp-type carbonate platform. The original mineralogy has been mainly aragonite and have been affected by two types of dissolution in closed and open diagenetic systems, possibly due to anoxic conditions or an increase in the effect of meteoric diagenesis