Textural characteristics and environmental interpretation of the lower miocene siliciclastic succession, dafin formation, Rabigh area, Saudi Arabia

الملخص EN

The main textural characteristics such as grain-size parameters, roundness and sphericity of the exposed Lower Miocene siliciclastic succession in Rabigh area indicate their deposition in a river system.

The succession is composed of several cycles, each of which consists of fining-upward channel conglomerates, sandstones, and flood plain mudstones that confirm their formation in a river system.

Grain size analysis of 54 selected samples representing the lower sandstone member of Dafin Formation showed that the grain size distribution is varying from gravel to mud.

These are classified into slightly gravelly sand, gravelly sand, sand (specify sorting), muddy sandy gravel, and less frequent muddy sand, gravelly muddy sand or slightly gravelly muddy sand categories.

The sand showed mostly bimodal distribution in addition to unimodal class, with a mean size ranges from very coarse to very fine.

The degree of sorting ranges from moderately well sorted to very poorly sorted.

The skewness of the sand, on the other hand, ranges from strongly coarse skewed to slightly fine skewed and kurtosis ranges from platy kurtic to very leptokurtic.

The Dafin sandstones are texturally immature.

Roundness and sphericity of 100 to 150 sand grains of 24 samples indicate that the roundness ranges from subangular to very angular, and the sphericity is low.

The results of the textural parameters, lithology, cyclicity and sedimentary structures of the Dafin siliciclastics support the finingupward character and the predominance of bimodal class which reflect their deposition in a river system.