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Back-Scattered Electron Microscopy (BSEM) - a tool for the study of graptolites
 
-----The 1970's saw the application of the scanning electron
microscopy (SEM) to graptolite studies. First SEM studies
of graptolitic material were published in Poland by
Roman
Kozłowski (1971) and in Great Britain by Barry Rickards et
al.
(1971). The conventional mode of SEM use is an invaluable
tool  for examining graptolite morphology and fine structure.
These conventional three-dimmensional SEM images are
obtained by measuring the secondary electron signal.

-----If the back-scattered electron signal is recorded an
image with mean atomic number contrast is produced.
Recently, Bernd-D. Erdtman and Yuandong Zhang (2004)
applied the Back-Scattered Electron Microscopy (BSEM)
technique to study graptolites. They wrote:
   


-----"On some specimens, carbonized periderm tissues are finely preserved and coalified to a black color, which results in a rather
sharp contrast with the lighter micritic-clay matrix. If these specimens were coated for SEM examination, these structures would be
completely covered by gold or palladium and consequently indiscernible and would no longer be available for light microscope
investigation, unlike those 3-dimensional parts which can be well observed and studied through scanning electron microscopy. For
this reason, we attempted examination of selected specimens without coating through SEM by Back Scatter Electron Imaging, a
technique available in the Technical University of Berlin (SEM brand name:
Hitachi S-2700)."
----" The normal SEM pictures of the specimens were unsatisfactory as the structures visible under light microscope could not be
discerned, but the simultaneous BSEM images were surprisingly clear and informative. "  " ...BSEM images illustrate both the
chemical compositional differences on the surface layer and the surface morphology of the sample. On our BSEM pictures of
Psigraptus jacksoni, the carbonized fuselli are marked as dark lines, whereas the rock matrix is brighter because of the dominance
of silicon and heavy elements. The surface morphology of those field, where the periderm has broken off and only films have
remained, has also been illustrated in the BSEM images (...)."

--
BSEM micrograph published by Zhang and Erdtmann (2004) showing Psigraptus jacksoni Rickards & Stait, 1984
from the Tremadocian of NE China.
Zhang, Y. and Erdtmann, B.-D. 2004. Tremadocian (Ordovician) biostratigraphy and graptolites at Dayangcha (Baishan, Jilin, NE China).-
Paläontologische Zeitschrift 78 (2), 32-354.
 
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Edited by
Piotr Mierzejewski, the Count of Calmont