The comparison of controlling factors of sand sedimentation using mineral composition and provenance in Bogowonto river, Purworejo, Central Java and Progo river, Kulonprogo, Yogyakarta

The characteristics of sediment deposits in the fluvial system reflect the sedimentary process. Grain’s “figure”, mineral composition, and source deposits (provenance) are the parameters which to identify the process. This study aims to determine the controlling factors of river sedimentation by comparing the parameters in the Bogowonto river, Purworejo, Central Java and Progo river, Kulonprogo, Yogyakarta. The methods of this research were provenance and thin section analyses covering all samples collected from upstream to downstream along the rivers. The six samples comprise three samples from the Bogowonto river and three samples from the Progo river representing upstream, middle, and downstream areas. The mineral composition of sand in Bogowonto river are Quartz about 16.67%, Feldspar 20.67%, Mafic minerals 20%, Opaque 36%, and Lithic about 6.67%. While, in the Progo river consist of Quartz 23.33%, Feldspar about 25.67%, Mafic minerals 23.33%, Opaque 17.67%, and Lithic occupy around 10%. Dickinson & Suczek’s diagram indicates the sources of the Bogowonto river and the Progo river sediment come from the volcanic arc (dissected arc) that happened during Oligonece to Holocene period due to subduction tectonic setting. The high feldspar and coarse grain size in Progo indicates the young sediment material with a low energy mechanism, while the high opaque mineral in Bogowonto shows the dominant basaltic source and massive weathered host rocks. The high amount of lithic in the Progo river is interpreted as a variative source from rock formations due to long stream erosion