PATTERNS OF SUMATRAN DOMED PEATLANDS: FROM ALLUVIAL TO COASTAL SETTINGS

Sumatran rain-fed and domed (ombrogenous) mires, supporting growths of large and tall trees at the edge, and small trees and shrubs at the center, are commonly used as models for thick coal deposits worldwide.

A study of the Batang Hari and Sungai Kumpeh River flood plains located near Jambi, Sumatra shows variations in the character of the Kumpeh, Dendang, and Endapan domed peatlands. The Kumpeh and Dendang peatlands, situated between the anastomosing Batang Hari and Sungai Kumpeh Rivers, have well developed domed topography despite the influences of active and abandoned meander channels and headward erosion of short-headed tributaries that have formed reentrants into the peatlands and aggraded flood-plain levee sediments along the peatland margins. This resulted in areally small (240-540 km²), discontinuous, lenticular peat deposits <9 m thick that have accumulated at 1.6 to 2 mm/yr. In contrast, the Endapan peatland, which formed domed to flat topography from the edge of the Batang Hari and Sungai Kumpeh Rivers to the coast, is a blanket-like (4,000 km²) peat deposit >11 m thick that accumulated at 7.85 cm/yr.

These data indicate that raised peatlands (Kumpeh and Dendang) along rivers reflect buildup of flood sediments that sustained robust vegetation, which in turn, accumulated topographically raised peat (<9 m thick) that reduced the extent of flooding. Conversely, flat coastal peatlands (Endapan) reflect peat accumulation (>11 m thick) from stunted vegetation that was removed from flood-sustaining nutrients. ¹⁴C dates of the Sumatran peats range from 4,250±210 to 7,580±340 BP in the alluvial plain, and 3,790±80 to 4,490±140 BP toward the coast; that is, the peatlands encroached seaward about 6 m/yr accompanied by increased peat accumulation. Thus, knowledge of distribution patterns of these peats may provide a key to the development of minable coal deposits.