SEDIMENTOLOGICAL , PETROGRAPHICAL AND CLAY MINERAIOGICAL STUDY OF THE GRAVEL AND CONGLOMERETE FACIES OF THE NORTHERN PART OF SAMARRA CITY ,IRAQ

Abstract

The gravels, conglomerates and the associated sediments in the studeid area, most probaly were deposited in an alluvial –fan environment . Sedimentologically, the sediments consist of three facies association: gravel and conglomerate(facies Q1),sand and sandstone (facies Q2)and gypcrete, gypseous mud and gypseous mudstone (facies Q3).These Facies most likely represent a mid-fan deposits and their material had been transported to the fan by stream flow condition . The petrography of gravels, sands and sandstones (The coarse sediments) reveal that the sedimentary rock fragments are the main constituents. The study indicates local origin of these sediments and had been derived from the older formations exposed in the north and northeast of the studied area .
The clay minerals of the fine grained sediments include: montmorillonite, chlorite, kaolonite and palygorskite. The palygorskite is considered as authogenic in origin whereas the other minerals are detrital.