GEOC 47 |
| Terpenoid resin is produced by all families and most genera of conifers (order Pinales, formerly Coniferales), and the distribution of terpenes present in most conifer resins is characteristic of the originating genera. Hence, the composition of conifer resins is of considerable chemotaxanomic value and in fossil samples (ambers) may be useful for addressing questions concerning the phylogeny of extinct taxa. Analyses of early Cretaceous (Barremian) amber from the English Wealden, Isle of Wight, southern England, by pyrolysis-gas chromatography-mass spectrometry, show that the terpene distribution of this amber consists almost exclusively of abietane-type and labdanoid diterpenes. The macrofossil record in the deposits of the Isle of Wight is dominated by the extinct Mesozoic conifer family Cheirolepidiaceae. However, the diterpene distribution in this amber is similar to diterpene distributions in resins of the modern conifer family Pinaceae. The Pinaceae are represented in the Wealden deposits of Southern England by only one extinct member, Pityites solmsii (Seward) Seward. Furthermore, in addition to abietanes and labdanoids, modern pinaceous resins typically include at least minor amounts of (iso)pimarane-type diterpenes, whereas (iso)pimaranes are effectively absent in the diterpene distribution observed in these samples. The potential implications of these data to the phylogeny of early Cretaceous conifers in these deposits will be discussed. This amber also represents the oldest amber to date to yield useful chemotaxonomic data. |
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The David J. Clifford Memorial Symposium
1:30 PM-3:45 PM, Tuesday, August 21, 2007 Boston Park Plaza -- St. James Rm, Oral
Sci-Mix
Division of Geochemistry |