LITHOLOGICAL CONTROL ON THE STATE OF PRESERVATION OF FOSSIL SEED COATS OF WATER PLANTS

In this study 1 Eocene wood sample and 25 fossil Eocene seed coats of water plants from 6 different localities on the south coast of England are analyzed using scanning electron and light microscopy, in additio n to Curie-point pyrolysis-GC(-MS) and solid state C-13 NMR, in order to characterize their morphological and chemical alteration in relatio n to different lithologies. Results from the translucent inner seed co at layers, tegmens, reveal that these tissues consist of aliphatic typ e biomacromolecules similar to cutan. The tegmens remain morphological ly and chemically unaltered. By contrast, the results from the outer s eed coat layers, testae, show that these are composed of polyphenolic macromolecules derived from lignin-celluloses. The testae are, on aver age, morphologically best preserved in fine-grained sediments, whereas best chemical preservation is observed in testae from coarse-grained sediments. Testae associated with pyrite in blue or green fine-grained sediments show poor quality chemical preservation, whereas those from dark brown and grey clays with pyrite show chemical preservation more similar to that of testae from coarse-grained sediments. These result s show that diagenetic alteration of organic matter is not only determ ined by burial history but can also be greatly influenced by differenc es in lithology.