ac5b02815_si_001.pdf (6.43 MB)
Large-Field Electron Imaging and X‑ray Elemental Mapping Unveil the Morphology, Structure, and Fractal Features of a Cretaceous Fossil at the Centimeter Scale
journal contribution
posted on 2015-10-06, 00:00 authored by Naiara
C. Oliveira, João H. Silva, Olga A. Barros, Allysson P. Pinheiro, William Santana, Antônio
A. F. Saraiva, Odair P. Ferreira, Paulo T. C. Freire, Amauri J. PaulaWe used here a scanning electron
microscopy approach that detected
backscattered electrons (BSEs) and X-rays (from ionization processes)
along a large-field (LF) scan, applied on a Cretaceous fossil of a
shrimp (area ∼280 mm2) from the Araripe Sedimentary
Basin. High-definition LF images from BSEs and X-rays were essentially
generated by assembling thousands of magnified images that covered
the whole area of the fossil, thus unveiling morphological and compositional
aspects at length scales from micrometers to centimeters. Morphological
features of the shrimp such as pleopods, pereopods, and antennae located
at near-surface layers (undetected by photography techniques) were
unveiled in detail by LF BSE images and in calcium and phosphorus
elemental maps (mineralized as hydroxyapatite). LF elemental maps
for zinc and sulfur indicated a rare fossilization event observed
for the first time in fossils from the Araripe Sedimentary Basin:
the mineralization of zinc sulfide interfacing to hydroxyapatite in
the fossil. Finally, a dimensional analysis of the phosphorus map
led to an important finding: the existence of a fractal characteristic
(D = 1.63) for the hydroxyapatite–matrix interface,
a result of physical-geological events occurring with spatial scale
invariance on the specimen, over millions of years.
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Keywords
Centimeter ScaleWezinc sulfide interfacingMapping UnveilAraripe Sedimentary BasinhydroxyapatiteCretaceous Fossilscale invariancebackscattered electronsionization processesscanning electron microscopy approachphosphorus mapphotography techniquesFractal Featureslength scalesfossilization eventLF BSE imagesMorphological features
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