Terpenoid compositions and botanical origins of Late Cretaceous and Miocene amber from China.

The terpenoid compositions of the Late Cretaceous Xixia amber from Central China and the middle Miocene Zhangpu amber from Southeast China were analyzed by gas chromatography-mass spectrometry (GC-MS) to elucidate their botanical origins. The Xixia amber is characterized by sesquiterpenoids, abietane and phyllocladane type diterpenoids, but lacks phenolic abietanes and labdane derivatives. The molecular compositions indicate that the Xixia amber is most likely contributed by the conifer family Araucariaceae, which is today distributed primarily in the Southern Hemisphere, but widely occurred in the Northern Hemisphere during the Mesozoic according to paleobotanical evidence. The middle Miocene Zhangpu amber is characterized by amyrin and amyrone-based triterpenoids and cadalene-based sesquiterpenoids. It is considered derived from the tropical angiosperm family Dipterocarpaceae based on these compounds and the co-occurring fossil winged fruits of the family in Zhangpu. This provides new evidence for the occurrence of a dipterocarp forest in the middle Miocene of Southeast China. It is the first detailed biomarker study for amber from East Asia.

为阐明其植物来源，采用气相色谱 - 质谱联用仪（GC - MS）对中国中部晚白垩世的西峡琥珀以及中国东南部中新世中期的漳浦琥珀的萜类化合物组成进行了分析。西峡琥珀以倍半萜类、枞烷型和叶枝杉烷型二萜类为特征，但不含酚类枞烷和半日花烷衍生物。其分子组成表明，西峡琥珀很可能源自南洋杉科针叶树。如今，南洋杉科主要分布于南半球，但古植物学证据显示，在中生代，该科植物广泛分布于北半球。中新世中期的漳浦琥珀以基于齐墩果烷型和乌苏烷型的三萜类以及基于杜松烯的倍半萜类为特征。基于这些化合物以及在漳浦同时出现的该科带翅化石果实，漳浦琥珀被认为源自热带被子植物龙脑香科。这为中国东南部中新世中期存在龙脑香林提供了新证据。这也是东亚琥珀首次详细的生物标志物研究。