Authors: Francisco Riquelme Paul Northrup José Luis RuvalcabaSil Vivian Stojanoff D Peter Siddons Jesús AlvaradoOrtega
Publish Date: 2013/12/10
Volume: 116, Issue: 1, Pages: 97-109
Abstract
Chiapas amber is a natural occurring fossil resin structurally composed of long macromolecule chains with semicrystalline phases associated with both fossil and polymerization process The most conspicuous characteristic of this fossil polymer is that it preserves ancient organic inclusions In the present work PIXE/RBS spectrometry particleinduced Xray emission/Rutherford backscattering were combined with complementary Kedge XANES spectroscopy Xray absorption nearedge structure to identify the amount of sulfur in Chiapas amber Initially the amber samples were examined using infrared reflected photomicrography Amber is transparent to infrared light and so embedded plants and animals are easily visible showing them in extraordinary detail as if they were immersed in a waterlike solution The PIXE/RBS data show that the proportion of sulfur in amber is significantly higher than that found in recently formed resins consistent with the biogeochemical process that transforms the resin into amber during longterm burial in geological deposits The sulfur Kedge XANES spectra from amber confirm the sulfur abundance and reveal sulfur species in the reduced and intermediate oxidation states in amber Almost no oxidized sulfur was found whereas the recent resins show mostly oxidized sulfur fractions This indicates that labile oxidized sulfur decays during fossilization and resin maturation must occur under conditions of oxygen depletion The implications of the presence of sulfur in amber for organic preservation is also discussed here Sulfur compounds work as a polymer additive that promotes intense resin solidification This restricts the early oxidantspecific biodegradation of the embedded biomatter and over geological time provides greater stability against chemical changesWe thank Karim López Francisco Jaimes and Mauricio Escobar for their technical support during the experimental runs at the Pelletron Accelerator Laboratory IFUNAM We also thank Dr Lauro Bucio from IFUNAM for the valuable comments that enriched the manuscript discussion We thank Biol Gerardo Carbot and Biol Marco A Coutiño from the Museo de Paleontologia ‘Eliseo Palacios Aguilera’ Chiapas they facilitated the holotype of H allendis and sample T2 The editor and referees provided useful suggestions that improved the manuscript This research is part of the PhDgranting program in Biological Sciences at the UNAM financially supported by CONACYT also partially supported by UNAMPAPIIT IN106011 and IN403210 grants as well as CONACYT 131944 MOVIL II endowment
Keywords: