نتایج جستجو برای: microfossils
تعداد نتایج: 531 فیلتر نتایج به سال:
Dietary reconstructions based on plant microfossils, such as starch grains and phytoliths, have been useful in increasing our understanding of past human populations. Microfossils have been recovered from sediments, stone tools, and, more recently, dental calculus. Methods for recovering microfossils from dental calculus have yet to be firmly established and there is some question about potenti...
Doubly polished thin sections, originally prepared for fluid inclusion studies, present great advantages in the study of microfossils in volcanic rocks. Better visibility and light conditions, variation in thickness of the thin sections and the possibility to combine fluid inclusion studies with microfossil studies lead to a wide range of advantages over ordinary thin sections. This includes th...
Ion microprobe measurements of carbon isotope ratios were made in 30 specimens representing six fossil genera of microorganisms petrified in stromatolitic chert from the approximately 850 Ma Bitter Springs Formation, Australia, and the approximately 2100 Ma Gunflint Formation, Canada. The delta 13C(PDB) values from individual microfossils of the Bitter Springs Formation ranged from -21.3 +/- 1....
Cryogenian cap carbonates that overlie Sturtian glacial deposits were formed during a post-glacial transgression. Here, we describe microfossils from the Kakontwe Formation of Zambia and the Taishir Formation of Mongolia-both Cryogenian age, post-Sturtian cap carbonates-and investigate processes involved in their formation and preservation. We compare microfossils from these two localities to a...
In rocks of late Paleoproterozoic and Mesoproterozoic age (ca. 1700-1000 million years ago), probable eukaryotic microfossils are widespread and well preserved, but assemblage and global diversities are low and turnover is slow. Near the Mesoproterozoic-Neoproterozoic boundary (1000 million years ago), red, green, and chromophytic algae diversified; molecular phylogenies suggest that this was p...
Prof. Xiao’s current research focuses on the biological evolution and environmental changes in the Proterozoic Eon (2500 to 543 million years ago). He has been working on some of the most important and exquisitely preserved microfossils from the ca. 600-million-year-old Doushantuo Formation in South China. These microfossils include multicellular red algae and animal embryos at successive cleav...
Microfossils are very important in order to establish terrain correlations, allowing to determinate the age of geological layers with a high grade of accuracy. They are also the fund of any micropaleontological studies. Actual techniques used to extract microfossils are manual, and require of a high amount of time and human resources. This fact make interesting the study of other more complex t...
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