Paleocurrent Analysis of the Sao Khua Formation, Khorat Group, Nong Bua Lamphu region, NE Thailand

摘要

Paleocurrent analysis provides information about the flow directions of rivers, longshore currents, sediment gravity flows, and paleowinds. This can help to interpret a model of paleogeography, which can lead to better predictability of economically-important facies (e.g., oil-saturated porous, permeable sandstone facies). The cross strata in the sandstones of the Sao Khua Formation of the Khorat Plateau are presented with principal modes ranging between 140° and 160° and secondary modes between 160° and 180°, giving a vector resultant angle of 158°. The vector dispersion value (the magnitude of vector mean) is 22.775%. Ripple marks in the Sao Khua Formation are found as interlayers within sandstone beds and in some exposures have a ripple index of 5. The result of vector resultant indicates that the paleocurrent trend of these sand channels was dominantly NE, whilst the small value of the magnitude of vector mean of this study indicates that the channel during the Sao Khua Formation time probably formed a braided channel environment.