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Communication Dans Un Congrès Année : 2018

X-ray tomography contribution to the palaeobiology of Upper Cretaceous planktonic foraminifera

Isabelle Kruta
Coroyer G.
  • Fonction : Auteur
Isabelle Rouget
Daniele Grosheny
  • Fonction : Auteur

Résumé

External test characters of Upper Cretaceous planktonic foraminifera are commonly com- pared to those of extant species. Similarities are used to interpret their life position: globu- lar pustulose forms (Whiteinella and Muricohedbergella) are supposed to have inhabited the upper part of the water column, whereas heavier keeled species (Rotalipora and Thalmanin- nella) would have evolved below the thermocline. However, this model cannot be applied to all time intervals. Indeed, during, Paleogene forms with a well-developed keel (Morozovel- lids) were common in the upper part of the water column. With the development of non-destructive X-Ray tomography, it is now possible to qualita- tively and quantitatively characterize all the ontogenetic stages of the planktonic foraminifera. Indeed, morphological test changes and internal volumes can be precisely constrained for each chamber. CT techniques were therefore used to study, for the rst time, the growth patterns of three well-preserved Cenomanian species (Whiteinella aprica, Rotalipora cushmani and Thalmaninnella greenhornensis) from the Greenhorn Formation of the Great Plains (South Dakota, US). The ontogenetic succession of their chambers has been compared to those of recent fossil species (Miocene up to Holocene) still inhabiting oceans. Surprisingly, the re- sults would show that the globular W. aprica and the keeled R. cushmani have the same growth pattern which is similar to the thermocline dweller Globorotalia menardii. Th. green- hornensis growth pattern is clearly di erent and belongs to the deep dwellers group. Those results are important as they will allow a better understanding of the extinction steeps of rotaliporids (Rotalipora and Thalmaninnella) during the onset of the Oceanic Anoxic Event 2.
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Dates et versions

hal-03066608 , version 1 (15-12-2020)

Identifiants

  • HAL Id : hal-03066608 , version 1

Citer

Delphine Desmares, Isabelle Kruta, Coroyer G., Isabelle Rouget, Daniele Grosheny. X-ray tomography contribution to the palaeobiology of Upper Cretaceous planktonic foraminifera. The 5th International Palaeontological Congress, Jul 2018, Paris, France. ⟨hal-03066608⟩
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