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| Titel |
Microanalyzes of remarkable microfossils of the Late Mesoproterozoic–Early Neoproterozoic |
| VerfasserIn |
Yohan Cornet, Jérémie Beghin, Blaise Baludikay, Francois Camille, Jean-Yves Storme, Philippe Compère, Emanuelle Javaux |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250128179
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| Publikation (Nr.) |
 EGU/EGU2016-8138.pdf |
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| Zusammenfassung |
| The Late Mesoproterozoic–Early Neoproterozoic is an important period to investigate the
diversification of early eukaryotes [1]. Following the first appearance of red algae in the Late
Mesoproterozoic, other (morphological or molecular) fossils of crown groups are recorded
during the Early Neoproterozoic, including green algae, sponges, amoebozoa and possibly
fungi. Other microfossils also includes unambiguous eukaryotes, including several distinctive
forms for that time period, such as the acritarchs Cerebrosphaera buickii (∼820–720 Ma),
Trachyhystrichosphaera aimika and T . botula (1100-720 Ma), and the multicellular
eukaryotic problematicum taxon Jacutianema solubila (1100–?720 Ma). To further
characterize the taxonomy of these microfossils and to test hypotheses about their possible
relationships to crown groups, we combine analyzes of their morphology, wall
ultrastructure and microchemistry, using optical microscopy, Scanning and Transmission
Electron microscopy (SEM and TEM), as well as Raman and FTIR microspectroscopy
respectively.
Cerebrosphaera populations from the Svanbergfjellet formation, Spitsbergen, and from
the Kanpa Formation, Officer Basin, Australia, include organic vesicles with dark and
robust walls ornamented by cerebroid folds [2]. Our study shows the occurrence of
complex tri- or bi-layered wall ultrastructures and a highly aromatic composition
[3].
The genus Trachyhystrichosphaera includes various species characterized by the presence
of a variable number of hollow heteromorphic processes [2]. Preliminary infrared
microspectroscopy analyzes performed on two species, T. aimika and T. botula, from
the 1.1 Ga Taoudeni Basin, Mauritania, and from the ∼1.1 - 0.8 Ga Mbuji-Mayi
Supergroup, RDC, indicate a strong aliphatic and carbonyl composition of the wall
biopolymer, with some differences linked to thermal maturity between the two
locations. TEM is also performed to characterize the wall ultrastructure of these two
species.
Various morphotypes of the species Jacutianema solubila from the Svanbergfjellet
Formation, Spitsbergen and from the Taoudeni Basin, Mauritania, are also characterized with
infrared and Raman microspectroscopy as well as with TEM, permitting to test a previous
hypothesis proposing that Jacutianema represents part of the life cycle of a Vaucherian alga
[4].
Deciphering the identity of these distinctive microfossils will improve our understanding
of the timing and pattern of eukaryote stem and crown group diversification in the
mid-Proterozoic, prior to large “snowball Earth” glaciations and during time of changing
ocean chemistry.
[1] Knoll et al. (2006) Philos. Trans. R. Soc. B 361 1023-1038 [2] Butterfield et al. (1994)
Fossils and Strata 34 82p [3] Cornet et al. (in preparation) [4] Butterfield (2004)
Paleobiology 30 (2), 231-25 |
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