Abstract
Despite of the recent influx of reports describing important fossil specimens from the Mesozoic Jehol Biota detailed information on the mechanism of fossilization and paleoenvironment in which these fossils were deposited is scanty. We present an analysis of microenvironment based upon scanning electron microscope observations of in situ pyrite framboids and microcrystallines of plant and vertebrate feather fossils in the JeholBiota. Pyrite microcrystallines and framboids occur extensively inside and on surface of plant fossils. Framboids found on feathers and in sedimentary matrix were in a lower abundance. These framboids have diameters ranging from 6 μm to 31 μm with an average of 20 μm indicating a dysoxic aqueous condition with free oxygen level less than 30 μmol/L for the microenvironment where these framboids were formed. The outgrowth of framboids inside plant tissues suggests the presence of water molecules and free oxygen at the cellular level during pyritization the relative timing between tissue decay and framboid formation implies a rapid tissue degradation occurred during the very early stage of fossilization. This line of reasoning is consistent with the observation that cell level structure of plant fossils from these deposits is rarely preserved. We propose a fossil envelop model to accommodate the different geo-chemical conditions between the microenvironment surrounding the fossil material and the macroenvironment of background lake bottom water.
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Supported by the Major State Basic Research Development Program of China (G2000077700), the Pilot Project of Knowledge Innovation, CAS (KZCX2-114), and the National Natural Science Foundation of China (Grant Nos. 39930020 and 40028201)
Supported by the Major State Basic Research Development Program of China (G2000077700), the Pilot Project of Knowledge Innovation, CAS (KZCX2-114), and the National Natural Science Foundation of China (Grant Nos. 39930020 and 40028201)
Notes
Supported by the Major State Basic Research Development Program of China (G2000077700), the Pilot Project of Knowledge Innovation, CAS (KZCX2-114), and the National Natural Science Foundation of China (Grant Nos. 39930020 and 40028201)