Depositional Environment of the Bara Formation, Fort Ranikot Area, Sindh

Abstract

Bara Formation is well exposed at Ranikot Fort area. Twenty two samples of the Bara Formation from the eastern flank of the Ranikot anticline of Fort Ranikot area have been investigated to interpret its environment of deposition. The values of different statistical parameters of the studied sediments for their grain size data, e.g., mean, median, standard deviation, skewness, and kurtosis were determined for plotting the cumulative curves and histograms to analyze the data. The 92% negative and 8% positive values of skewness, respectively, indicated that the studied sediments are composed of coarse grained to fine grained sediments and were deposited under the high-low energy conditions of fluviatile environment. The presence of abundant amounts of Quartz (SiO2) in the bulk-rock samples also suggested fluviatile environment. The inclusive graphic standard deviation diagrams and the size distribution data also indicates that fine-medium grained sediments were deposited in the study area. Occurrence of three groups of sediments e.g., sediments from lower lagoon; sediments from upper lagoon and river; and the sediments from the dead-end marsh channels from the deeper parts of the basin of deposition have been recognized. The kurtosis values indicate that studied sediments are composed of Platykurtic, Leptokurtic and Mesokurtic groups of sediments, respectively.