TY - JOUR
T1 - Middle Triassic foraminifers from northern Laos and their paleobiogeographic significance
AU - Miyahigashi, Akira
AU - Hara, Hidetoshi
AU - Hisada, Ken ichiro
AU - Nakano, Nobuhiko
AU - Charoentitirat, Thasinee
AU - Charusiri, Punya
AU - Khamphavong, Keo
AU - Martini, Rossana
AU - Ueno, Katsumi
N1 - Funding Information:
We are grateful to the Department of Geology, Lao P.D.R., for logistics support, including the permission for fieldwork. Thanks are also extended to Drs. Daniel Vachard and Roberto Rettori for their constructive review comments, Dr. Anthony J. Barber for correcting the English style, and to Dr. Gilles Escarguel, the Editor in chief of the journal, for editorial suggestions, all of which were helpful in improving our manuscript. Part of this research was accomplished during sabbatical stay of K.U. at the University of Geneva; he thanks the Fukuoka University for permitting the stay. The research was also supported by the Swiss NSF project 200020_156422 to R.M. This research is part of the IGCP589 Project.
Publisher Copyright:
© 2017 Elsevier Masson SAS
PY - 2017/12
Y1 - 2017/12
N2 - Triassic foraminifers are reported for the first time from limestones in the upper part of the Nam Sam Suite distributed in the Sam Neua area of northern Laos. The study area is located in the northern part of the Indochina Block, based on the basic geotectonic subdivision of mainland Southeast Asia. The fauna consists of 17 taxa and includes age-diagnostic Pilammina densa, Pilamminella grandis, Citaella dinarica, C.? deformata, Arenovidalina amylovoluta, and Diplotremina astrofimbriata. It is referable to the middle Anisian (Pelsonian) of the Middle Triassic. The microfacies of the studied samples are subdivided into three types, suggesting low wave-energy uppermost subtidal, moderately wave-agitated uppermost subtidal, and intertidal environments, respectively. Two species are specific to the intertidal microfacies. A notable paleontological feature is the dominance of P. densa, shown by the large number of individuals in the foraminiferal assemblage. This could be related to its opportunistic nature in the stressful conditions of the intertidal environment. We also consider that C.? deformata may be ecologically adapted to a hypersaline environment. The Sam Neua fauna shares several important species, such as C. dinarica, P. densa, P. grandis, and A. amylovoluta, with those found in the Sibumasu Block, Sukhothai Zone, and South China Block, suggesting that these major geotectonic domains in mainland Southeast Asia formed a single paleobiogeographic province during Anisian time. In view of paleogeography, the present results point toward a rather restricted (narrow) Paleo-Tethyan ocean basin allowing faunal interchanges among separated Eastern Tethyan continental blocks during the Middle Triassic.
AB - Triassic foraminifers are reported for the first time from limestones in the upper part of the Nam Sam Suite distributed in the Sam Neua area of northern Laos. The study area is located in the northern part of the Indochina Block, based on the basic geotectonic subdivision of mainland Southeast Asia. The fauna consists of 17 taxa and includes age-diagnostic Pilammina densa, Pilamminella grandis, Citaella dinarica, C.? deformata, Arenovidalina amylovoluta, and Diplotremina astrofimbriata. It is referable to the middle Anisian (Pelsonian) of the Middle Triassic. The microfacies of the studied samples are subdivided into three types, suggesting low wave-energy uppermost subtidal, moderately wave-agitated uppermost subtidal, and intertidal environments, respectively. Two species are specific to the intertidal microfacies. A notable paleontological feature is the dominance of P. densa, shown by the large number of individuals in the foraminiferal assemblage. This could be related to its opportunistic nature in the stressful conditions of the intertidal environment. We also consider that C.? deformata may be ecologically adapted to a hypersaline environment. The Sam Neua fauna shares several important species, such as C. dinarica, P. densa, P. grandis, and A. amylovoluta, with those found in the Sibumasu Block, Sukhothai Zone, and South China Block, suggesting that these major geotectonic domains in mainland Southeast Asia formed a single paleobiogeographic province during Anisian time. In view of paleogeography, the present results point toward a rather restricted (narrow) Paleo-Tethyan ocean basin allowing faunal interchanges among separated Eastern Tethyan continental blocks during the Middle Triassic.
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U2 - 10.1016/j.geobios.2017.09.004
DO - 10.1016/j.geobios.2017.09.004
M3 - Article
AN - SCOPUS:85033564863
VL - 50
SP - 441
EP - 451
JO - Geobios
JF - Geobios
SN - 0016-6995
IS - 5-6
ER -