Abstract

Jangkang Beach is located in the Deluk village, Bengkalis District, Riau Province, Indonesia. This beach is overgrown by mangrove plants and peat. Its presence resulting varying thickness amount of terrestrial organic material deposited to the shore. Purpose of this research is to determine the characteristics of coastal sediments that influenced by the distribution of terrestrial organic materials and its sedimentary structures. The method is used for field survey that consists of drilling core at five locations, lateral measured section, and granulometric analysis at laboratory. This research resulted in that coastal sediments consist of medium to fine sand, silt, clay, and organic material. The terrestrial organic material deposited at Jangkang Beach has size ±35 cm which is wooden to finely sized with thickness 5–15 cm. Distribution of this material located on littoral zone and number of TOM decreased seaward with increasingly more fine wood. This TOM was deposited above ripple mark sedimentary structure. Ripple mark has slope 100–480 with symmetrical shape. Other sedimentary structures found are bioturbation structure, lenses of TOM, cross lamination, and parallel lamination.