Selective loss of carbohydrates from plant remains during coalification

Abstract

Fossil leaves of Oleinites willsii, Banksieaephyllum angustum, associated organic matter and rhizomes of Gleichenia sp. isolated from Yallourn brown coal deposits, Latrobe Valley, Victoria, Australia and their living relatives have been analysed by high-resolution solid-state 13C nuclear magnetic resonance spectroscopy, infrared spectroscopy and pyrolysis—gas chromatography—mass spectrometry. The fossil leaves and rhizomes retain carbohydrates and, on a carbon basis, the amounts of carbohydrates in the fossil rhizomes and their living relatives appear to be similar. On the other hand, the amount of carbohydrates in the fossil leaves is substantially less than in the living relatives. The organic matter found intimately associated with the fossil leaves is quite different in structure from the fossil leaves themselves and bears a closer resemblance to humic acids and the smallest (<75μm) fractions of Yallourn brown coal. Since the fossil leaves are found in stratified beds, interfolded with associated organic matter, it is suggested that during coalification the leaves and associated organic matter undergo independent transformations and are brought together by water transport.