PRELIMINARY TAPHONOMIC RESEARCH OF MESOZOIC FOSSIL INSECTS FROM CHINA

Mesozoic was an important stage in the insect evolutionary process. Mesozoic Insects are abundant in China, and pave the way to explore insect systematics and evolutionary. Their stratigraphy and surrounding rocks also provide clues to the preservation and taphonomy of fossils.

Herein, we reviewed these insect-bearing localities, and presented the updated geological ages of these fossil layers based on isotopic dating results and stratigraphic investigations, and also present a primary discussion about the surrounding minerals of fossils. We have updated the composition of insect fauna, and analyzed qualitatively and quantitatively on the matrix of mineral composition of Mesozoic insect fauna, which could provide important clues to taphonomic mechanisms and to lay a foundation for further study of the sedimentary environment and diagenetic evolution. Based on XRD results, the mineral composition in matrix from Mesozoic insects was mainly in plagioclase, quartz, clays, carbonate, some with minor anacite, pyrite, gypsum, amphibole. Clay minerals of the matrix were taken illite, smectite, and chlorite in main, their total content was around 2-47%. The remaining contents are quartz and carbonate minerals. Among these, illite was the abundant clay species with amount of 31-88%. And then the smectite and chlorite.

We also used the Scanning Electron Microscope (SEM) equipped with an energy dispersive spectrometer (EDS) to investigate the surface morphology and microstructure, and to analyse elemental distribution on both fossils and its surrounding rocks. Compression fossil insects are commonly preserved in organic remains and with some calcium carbonate accumulated alongside the fossilization process. Pyritized insect fossils from Chaoyangshan of Inner Mongolia are a special case, which are preserved in “fossil envelop” model with in situ pyrite framboids and microcrystallines. These differences show various mechanisms of fossilization, from which we can infer some relevant paleo-environmental information and also provide theoretical support for fossil taphonomy.

KEY WORDS: Mesozoic, fossil insects, mineral composition, preservation, taphonomy