Growth, Duplication and Lateral Mutual Compressive Deformation of Akouemma hemisphaeria on the Seafloor of Okondja Basin at 2.2 Ga (Gabon)  

作　　者：Ambroise Edou-Minko Mathieu Moussavou Tomohiko Sato Yusuke Sawaki Simplice Ndong Ondo Richard Maire Guillaume Fleury Michel Mbina Mounguengui Anders Kaestner Richard Ortega Stéphane Roudeau Asuncion Carmona Makaya Mvoubou Benjamin Musavu Moussavou Osamu Sasaki Shigenori Maruyama 

机构地区：[1]Université des Sciences et Techniques de Masuku, Franceville, Gabon [2]Earth-Life Science Institute (ELSI), Tokyo Institute of Technology, Tokyo, Japan [3]Department of Earth Science and Astronomy, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan [4]UMR 5319 Passages, Maison des Suds, CNRS-Université Bordeaux-Montaigne, Pessac, France [5]Muséum d’Histoire Naturelle de Toulouse, Toulouse, France [6]Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, Villigen, Switzerland [7]CENBG, Univ. Bordeaux, CNRS, IN2P3, UMR 5797, Gradignan, France [8]Tohoku University Museum, Université de Tohoku, Sendai, Japan

出　　处：《International Journal of Geosciences》2017年第9期1172-1191,共20页地球科学国际期刊（英文）

摘　　要：A colony of macro-fossils Akouemma hemisphaeria has been described in the Paleoproterozoic sedimentary basin of Okondja, Gabon. These fossils are classified into two groups according to their spheroidal or elongated forms. The spheroidal shapes are similar, have a tripartite structure with two hemispheres and a median disc and gradually pass to the elongated forms. These elongated forms have a pronounced bipartite tendency to two “hemispheres” separated by a median surface, and often have several ovoid “pieces” attached. The elongated specimens show both lateral growth marks and signs of fission. Growth marks are characterized by unidirectional homogeneous side elongations and lateral bud-like protuberances. The signs of fission are marked by circular furrows perpendicular to the direction of elongation, called “constriction furrows” with varying depths depending on the degree of fission of the specimen and internal vertical “division planes”. All of these ovoid and elongated specimens have undergone significant initial deformations due mainly to mutual lateral compressions in tabular beds. The Akouemma hemisphaeria macro-organisms, which were primitive probably sessile organisms, lived on the seafloor. They provide the oldest known record of macro-organisms on Earth having vegetative growth and asexual reproduction by budding, lateral elongation and fission. Their mutual lateral deformations would result from their growth.A colony of macro-fossils Akouemma hemisphaeria has been described in the Paleoproterozoic sedimentary basin of Okondja, Gabon. These fossils are classified into two groups according to their spheroidal or elongated forms. The spheroidal shapes are similar, have a tripartite structure with two hemispheres and a median disc and gradually pass to the elongated forms. These elongated forms have a pronounced bipartite tendency to two “hemispheres” separated by a median surface, and often have several ovoid “pieces” attached. The elongated specimens show both lateral growth marks and signs of fission. Growth marks are characterized by unidirectional homogeneous side elongations and lateral bud-like protuberances. The signs of fission are marked by circular furrows perpendicular to the direction of elongation, called “constriction furrows” with varying depths depending on the degree of fission of the specimen and internal vertical “division planes”. All of these ovoid and elongated specimens have undergone significant initial deformations due mainly to mutual lateral compressions in tabular beds. The Akouemma hemisphaeria macro-organisms, which were primitive probably sessile organisms, lived on the seafloor. They provide the oldest known record of macro-organisms on Earth having vegetative growth and asexual reproduction by budding, lateral elongation and fission. Their mutual lateral deformations would result from their growth.

关 键 词：PALEOPROTEROZOIC Francevillian Group Okondja BASIN Akouemma hemisphaeria GROWTH DUPLICATION 

分 类 号：R73[医药卫生—肿瘤]