The botanical provenance and taphonomy of Late Cretaceous Chatham amber, Chatham Islands, New Zealand
2019 (English)In: Review of Palaeobotany and Palynology, ISSN 0034-6667, E-ISSN 1879-0615, Vol. 260, p. 16-26Article in journal, News item (Refereed) Published
Abstract [en]
Fossil resin (amber) has been recently reported as common, but small, sedimentary components throughout thelower Upper Cretaceous (Cenomanian; 99–94 Ma) strata of the Tupuangi Formation, Chatham Islands, easternZealandia. From these deposits, resin has also been identified and obtained from well-preserved, coalified specimensof the conifer fossil Protodammara reimatamorioriMays and Cantrill, 2018. Here, we employed attenuatedtotal reflectance Fourier-transform infrared spectroscopy (ATR-FTIR) to both dispersed and in situ amber specimens.These resulted in very similar chemical signatures, indicating that these fossils are likely from the same orclosely-related botanical sources. The FTIR data are typical of a conifer source within the ‘cupressaceous resins’category of Tappert et al. (2011). Carbon-13 nuclear magnetic resonance spectroscopy (13C NMR) facilitatedthe probable identification of these ambers as ‘Class Ib' (sensu Anderson et al. 1992). Based on these spectraldata sets, the likely botanical sources of the amber were either Araucariaceae or Cupressaceae; both of these coniferfamilies were common and widespread in the Southern Hemisphere during the Cretaceous. However, themorphology and anatomy of P. reimatamoriori support an affinity to the latter family, thus indicating that the Cretaceousamber of the Chatham Islands was generally produced by members of the Cupressaceae. Comparing theFTIR data to the published spectra of modern resins, we also identify a band ratio which may aid in distinguishingbetween the FTIR spectra of Araucariaceae and Cupressaceae, and outline the limitations to this approach. A highconcentration of ester bonds in Chatham amber specimens, which exceeds typical Cupressaceae resins, is probablycaused by taphonomic alteration via thermal maturation. The source of thermal alteration was likely preburialwildfires,conditions forwhich P. reimatamoriori was adapted to as part of its life cycle. A comparison of ambersof the Chatham Islands with modern resins and amber from various localities in Australasia reveals that,taphonomic influences aside, Chatham amber has a unique signature, suggesting that members of the basalCupressaceae (e.g., Protodammara) were not major contributors to other documented Australasian amber deposits.The closest analogy to Chatham amber deposits appears to be the Upper Cretaceous Raritan Formation,USA, which is characterised by its rich amber, charcoal and Cupressaceae fossil assemblages. This study furthersupports the hypotheses that the early Late Cretaceous south polar forests were dominated by Cupressaceae,and regularly disturbed by wildfires.
Place, publisher, year, edition, pages
Amsterdam: Elsevier, 2019. Vol. 260, p. 16-26
Keywords [en]
Amber, Chemotaxonomy, FTIR, 13C NMR, Cupressaceae, Principal component analysis
National Category
Evolutionary Biology Geology
Research subject
Ecosystems and species history; The changing Earth
Identifiers
URN: urn:nbn:se:nrm:diva-2932DOI: 10.1016/j.revpalbo.2018.08.004OAI: oai:DiVA.org:nrm-2932DiVA, id: diva2:1260537
Note
Fieldwork and research supported by National Geographic Society (grant 9761-15) awarded to C.M.; additional financial support provided by the Paleontological Society and Monash University.
2018-11-032018-11-032019-01-08Bibliographically approved