Abstract
A large leaf was discovered on a piece of fossilized resin from Jambi Province, Sumatra. Based on its location, mid-Miocene age, and structural similarity to modern leaves of members of the family Dipterocarpaceae, it is tentatively assigned to the genus ?Dipterocarpus. This action is supported by the presence of Group B resinites as determined by the use of carbon-13 NMR Spectroscopy. The fossil leaf was surrounded by a hard sub-bituminous coal that had been subjected to high temperatures and pressures that destroyed most of the resinite. The presence of a light brown covering surrounding the fossil suggests that there was erosion of silicified sandstone. The leaf would fall within the Malesian floristic Region together with some 25,000 other species of flowering plants. The Dipterocarpaceae predominately inhabit tropical regions of the Old World. Conditions that occurred in Sumatra when the leaf was fossilized probably greatly resembled those in the state coal mine in Wonthaggi. These Australian lignitic coals still contain associated fossil resin in the form of plant material such as leaves; however, acids destroyed most animal remains. The Sumatran resin that contained the fossil leaf under study was likely subjected to intense volcanic activity, as revealed by XRD studies. Trace amounts of Tonstein minerals i.e. quartz, illite, and mica (muscovite) are related to volcanic ash falls. In fact, volcanic activity and its relationship to the increased production of resin during the Miocene may have continued since the middle of the twentieth century