Abstract
In mainland Southeast Asia, Permian–Triassic successive subduction of the Paleo-Tethyan oceanic lithosphere formed an island-arc system called the Sukhothai Zone, along the margin of the Indochina Block. This zone has been considered to extend from Northern Thailand to southwestern Yunnan of China, but so far lacked concrete evidence from northern Laos in between. This makes basic geotectonic subdivision of mainland Southeast Asia ambiguous. In this study Triassic foraminifers from limestone distributed in the Long area of Luang Namtha Province (northwestern Laos) solve this problem. The relevant limestone has a kilometer-sized extent and was previously assigned to the Carboniferous–Early Permian based only on lithological grounds in regional geological mapping. Its Triassic age is demonstrated for the first time based on foraminifers. We discriminated from this limestone Aulotortus sinuosus, A. tumidus, Ophthalmidium danneri, Endotriada tyrrhenica, Endoteba obturata, Endotebanella kocaeliensis, Diplotremina astrofimbriata, Duostomina biconvexa, and Palaeolituonella majzoni, and concluded that the fauna is referable to the Carnian (early Late Triassic). Cement-rich reefal sediments consisting of Carniphytes multisiphonatus-microbial boundstone and sparse-allochem bioclastic grainstone containing abundant fragments of Plexoramea gracilis are common in this limestone. They suggest open-marine sedimentation on a shallow carbonate platform, possibly comparable to a cement-dominated upper-slope “Tubiphytes” reef environment found elsewhere in the Triassic. In neighboring mainland Thailand, Carnian limestone with similar lithological and paleontological properties is found only in the Doi Long Formation distributed in the Sukhothai Zone. This evidence provides a firm basis for the tectonostratigraphic correlation of the Sukhothai Zone, in northern Laos. Consequently, our study is critical in giving a clue to clarify the distribution and extension in northern Laos of a Permian–Triassic island-arc domain, the Sukhothai Zone, which is one of the major tectonostratigraphic units comprising mainland Southeast Asia. In this paper, we also described two encrusting foraminifers having multi-chambered (septate) shells, which have been seldom documented in Triassic foraminiferal literature.
| Original language | English |
|---|---|
| Pages (from-to) | 88-99 |
| Number of pages | 12 |
| Journal | Gondwana Research |
| Volume | 61 |
| DOIs | |
| Publication status | Published - Sep 1 2018 |
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Keywords
- Late Triassic foraminifera
- Northern Laos
- Sukhothai Zone
- Tectonostratigraphy
- “Tubiphytes”-microbial reefal limestone
ASJC Scopus subject areas
- Geology
Cite this
The Sukhothai Zone (Permian–Triassic island-arc domain of Southeast Asia) in Northern Laos : Insights from Triassic carbonates and foraminifers. / Ueno, Katsumi; Kamata, Yoshihito; Uno, Koji; Charoentitirat, Thasinee; Charusiri, Punya; Vilaykham, Khamseng; Martini, Rossana.
In: Gondwana Research, Vol. 61, 01.09.2018, p. 88-99.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - The Sukhothai Zone (Permian–Triassic island-arc domain of Southeast Asia) in Northern Laos
T2 - Insights from Triassic carbonates and foraminifers
AU - Ueno, Katsumi
AU - Kamata, Yoshihito
AU - Uno, Koji
AU - Charoentitirat, Thasinee
AU - Charusiri, Punya
AU - Vilaykham, Khamseng
AU - Martini, Rossana
PY - 2018/9/1
Y1 - 2018/9/1
N2 - In mainland Southeast Asia, Permian–Triassic successive subduction of the Paleo-Tethyan oceanic lithosphere formed an island-arc system called the Sukhothai Zone, along the margin of the Indochina Block. This zone has been considered to extend from Northern Thailand to southwestern Yunnan of China, but so far lacked concrete evidence from northern Laos in between. This makes basic geotectonic subdivision of mainland Southeast Asia ambiguous. In this study Triassic foraminifers from limestone distributed in the Long area of Luang Namtha Province (northwestern Laos) solve this problem. The relevant limestone has a kilometer-sized extent and was previously assigned to the Carboniferous–Early Permian based only on lithological grounds in regional geological mapping. Its Triassic age is demonstrated for the first time based on foraminifers. We discriminated from this limestone Aulotortus sinuosus, A. tumidus, Ophthalmidium danneri, Endotriada tyrrhenica, Endoteba obturata, Endotebanella kocaeliensis, Diplotremina astrofimbriata, Duostomina biconvexa, and Palaeolituonella majzoni, and concluded that the fauna is referable to the Carnian (early Late Triassic). Cement-rich reefal sediments consisting of Carniphytes multisiphonatus-microbial boundstone and sparse-allochem bioclastic grainstone containing abundant fragments of Plexoramea gracilis are common in this limestone. They suggest open-marine sedimentation on a shallow carbonate platform, possibly comparable to a cement-dominated upper-slope “Tubiphytes” reef environment found elsewhere in the Triassic. In neighboring mainland Thailand, Carnian limestone with similar lithological and paleontological properties is found only in the Doi Long Formation distributed in the Sukhothai Zone. This evidence provides a firm basis for the tectonostratigraphic correlation of the Sukhothai Zone, in northern Laos. Consequently, our study is critical in giving a clue to clarify the distribution and extension in northern Laos of a Permian–Triassic island-arc domain, the Sukhothai Zone, which is one of the major tectonostratigraphic units comprising mainland Southeast Asia. In this paper, we also described two encrusting foraminifers having multi-chambered (septate) shells, which have been seldom documented in Triassic foraminiferal literature.
AB - In mainland Southeast Asia, Permian–Triassic successive subduction of the Paleo-Tethyan oceanic lithosphere formed an island-arc system called the Sukhothai Zone, along the margin of the Indochina Block. This zone has been considered to extend from Northern Thailand to southwestern Yunnan of China, but so far lacked concrete evidence from northern Laos in between. This makes basic geotectonic subdivision of mainland Southeast Asia ambiguous. In this study Triassic foraminifers from limestone distributed in the Long area of Luang Namtha Province (northwestern Laos) solve this problem. The relevant limestone has a kilometer-sized extent and was previously assigned to the Carboniferous–Early Permian based only on lithological grounds in regional geological mapping. Its Triassic age is demonstrated for the first time based on foraminifers. We discriminated from this limestone Aulotortus sinuosus, A. tumidus, Ophthalmidium danneri, Endotriada tyrrhenica, Endoteba obturata, Endotebanella kocaeliensis, Diplotremina astrofimbriata, Duostomina biconvexa, and Palaeolituonella majzoni, and concluded that the fauna is referable to the Carnian (early Late Triassic). Cement-rich reefal sediments consisting of Carniphytes multisiphonatus-microbial boundstone and sparse-allochem bioclastic grainstone containing abundant fragments of Plexoramea gracilis are common in this limestone. They suggest open-marine sedimentation on a shallow carbonate platform, possibly comparable to a cement-dominated upper-slope “Tubiphytes” reef environment found elsewhere in the Triassic. In neighboring mainland Thailand, Carnian limestone with similar lithological and paleontological properties is found only in the Doi Long Formation distributed in the Sukhothai Zone. This evidence provides a firm basis for the tectonostratigraphic correlation of the Sukhothai Zone, in northern Laos. Consequently, our study is critical in giving a clue to clarify the distribution and extension in northern Laos of a Permian–Triassic island-arc domain, the Sukhothai Zone, which is one of the major tectonostratigraphic units comprising mainland Southeast Asia. In this paper, we also described two encrusting foraminifers having multi-chambered (septate) shells, which have been seldom documented in Triassic foraminiferal literature.
KW - Late Triassic foraminifera
KW - Northern Laos
KW - Sukhothai Zone
KW - Tectonostratigraphy
KW - “Tubiphytes”-microbial reefal limestone
UR - http://www.scopus.com/inward/record.url?scp=85047905170&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85047905170&partnerID=8YFLogxK
U2 - 10.1016/j.gr.2018.04.013
DO - 10.1016/j.gr.2018.04.013
M3 - Article
AN - SCOPUS:85047905170
VL - 61
SP - 88
EP - 99
JO - Gondwana Research
JF - Gondwana Research
SN - 1342-937X
ER -