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For nearly 100 million years, the India subcontinent drifted from Gondwana until its collision with Asia some 50 Ma, during which time the landmass presumably evolved a highly endemic biota. Recent excavations of rich outcrops of 50–52-million-year-old amber with diverse inclusions from the Cambay Shale of Gujarat, western India address this issue. Cambay amber occurs in lignitic and muddy sediments concentrated by near-shore chenier systems; its chemistry and the anatomy of associated fossil wood indicates a definitive source of Dipterocarpaceae. The amber is very partially polymerized and readily dissolves in organic solvents, thus allowing extraction of whole insects whose cuticle retains microscopic fidelity. Fourteen orders and more than 55 families and 100 species of arthropod inclusions have been discovered thus far, which have affinities to taxa from the Eocene of northern Europe, to the Recent of Australasia, and the Miocene to Recent of tropical America. Thus, India just prior to or immediately following contact shows little biological insularity. A significant diversity of eusocial insects are fossilized, including corbiculate bees, rhinotermitid termites, and modern subfamilies of ants (Formicidae), groups that apparently radiated during the contemporaneous Early Eocene Climatic Optimum or just prior to it during the Paleocene-Eocene Thermal Maximum. Cambay amber preserves a uniquely diverse and early biota of a modern-type of broad-leaf tropical forest, revealing 50 Ma of stasis and change in biological communities of the dipterocarp primary forests that dominate southeastern Asia today.

The application of pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) to the analysis of natural resins and resinites based on dlterpenold carboxylic acids has been Investigated, In order to determine the usefulness of this technique for the analysis of these materials. It has been found that Py-GC/MS analyses using simultaneous pyrolytic methylation (SPM) provide an accurate Indication of the composition of these materials, except with respect to compounds with an additional hydroxy and/or carbonyl functionality. Resin acid methyl esters (RAMES) are efficiently produced In situ by copyrolysls with tetramethylammonlum hydroxide. Pyrolysis did not result In significant thermal degradation or Isomerization of the RAMES characterized In this study. Some dehydration of RAME alcohols Is observed however, and both hydroxy-and carbonyl-containing RAMES undergo undesirable side reactions with the methylating reagent, which results In the formation of nitrogen-containing products. The optimum pyrolysis temperature for low-to moderate-rank resinites using the conditions employed In this study was found to be 480 °C. Py-GC/MS analyses without In situ methylation were found to provide generally less adequate data for structural and compositional analyses.

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Amber is one of the few gemstones based on an organic structure. Found over most of the world, it is the fossil form of sticky plant exudates called resins. Investigation of amber by modern analytical techniques provides structural information and insight into the identity of the ancient plants that produced the source resin. Mass spectrometric analysis of materials separated by gas chromatography has identified specific compounds that are the basis of a reliable classification of the different types of amber. NMR spectroscopy of bulk, solid amber provides a complementary classification. NMR spectroscopy also can be used to characterize modern resins as well as other types of plant exudates such as gums, gum resins, and kinos, which strongly resemble resins in appearance but have very different molecular constitutions.