Abstract:Triassic deposits in the Bangong-Nujiang Suture Zone are important for understanding its tectonic nature and evolutionary history, but have not been systematically studied due to a lack of biostratigraphic data. For a long time, the Upper Triassic Quehala Group featuring clasolite has been regarded as the only rocky unit. In recent years, the silicite-dominated Gajia Formation that bears radiolarian fossils was suggested to represent Ladinian to Carnian deposits. The Upper Permian and Lower Triassic rocks have… Show more
“…Regionally, the revised Wuga Formation correlates with the Rhaetian Quehala Formation of the central BNSZ, a clastic succession. Norian rocks have been described from the central BNSZ (Mailonggang Formation) 12 , the Lhasa Terrane (Mailonggang Formation and Jiangrang Formation) 30 – 33 , and the South Qiangtang Terrane (Riganpeico Formation) 34 where they are made up largely of thick-bedded limestone and dolomite (Fig. 4 ).…”
Section: Discussionmentioning
confidence: 99%
“… Figure 4 The Norian (A) and Rhaetian (B) sediments in the BNSZ, Lhasa Terrane, and South Qiangtang Terrane. ①-Mailonggang section (conodonts) 30 ; ②-Yawa section (conodonts and corals) 32 ; ③-DibuCo section (conodonts) 31 ; ④-NamuCo section (corals) 33 ; ⑤,⑥-sections within the South Qiangtang Terrane (corals) 34 ; ⑦-DaruCo section (corals) 12 ; ⑧-ZhaxicobuCo section (conodonts; this paper); LS Lhasa Terrane, SQ South Qiangtang Terrane, LSSZ LongmuCo-Shuanghu Suture Zone, BNSZ Bangong-Nujiang Suture Zone, IYSZ Indus-Yarlung Zangbo Suture Zone. Red solid lines define boundaries between different tectonic terranes.…”
Section: Discussionmentioning
confidence: 99%
“…The debate centers on three opinions regarding the tectonic significance of the BNSZ. One view holds that the BNSZ was not represented by an ocean during the Triassic 6 , 8 , 11 , 12 . A contrary argument maintains that the BNSZ was a long-standing ocean that existed from Late Paleozoic to Cretaceous time 2 , 5 .…”
Section: Introductionmentioning
confidence: 99%
“…1 B). These deposits include cherty strata that host Carnian radiolarians and conodonts described from the Dingqing area 16 ; chert-dominated deposits containing Ladinian radiolarians in the Gajia area 14 ; and dolomite-dominated rocks bearing Late Permian corals and Early Triassic to Anisian conodonts and limestone that yields Norian corals documented from the Ban’ge area 12 . These findings confirm that Triassic deposits are well represented in the central and east BNSZ (Fig.…”
Section: Introductionmentioning
confidence: 99%
“…1 ). The marked similarity of the Triassic succession of the central BNSZ with deposits of the Lhasa and Qiangtang terranes suggests that the BNSZ was an extension of these terranes rather than a geographic barrier separating them in Late Permian to Triassic time 12 .…”
The Bangong-Nujiang Suture Zone (BNSZ) of Tibet (Xizang) has been interpreted to represent a relic of the Bangong-Nujiang Ocean. However, the existence of this ocean during Triassic time remains a point of contention. A sedimentary succession spanning the Upper Permian through Triassic described from the central BNSZ suggests that the Lhasa and South Qiangtang terranes were contiguous thus negating the existence of a terrane-separating ocean during Triassic time. However, the apparent lack of Triassic deposits in the west BNSZ has called into question the existence of Triassic deposits in the central region of the BNSZ. Our biostratigraphic work in the Wuga Formation of the Gaize area has yielded abundant Norian conodonts thus confirming the existence of Upper Triassic deposits in the west BNSZ. The clastic deposits of the Wuga Formation are herein interpreted to be of Rhaetian age. Moreover, intercalated limestone and chert are termed the Dongnale Formation of Norian age. The Norian to Rhaetian succession can be correlated with strata of the central BNSZ as well as with deposits of the Lhasa Terrane and the South Qiangtang Terrane. Similar stratigraphies among these regions through the Late Triassic suggests a shared depositional setting and that the BNSZ was not an ocean in Norian and Rhaetian time.
“…Regionally, the revised Wuga Formation correlates with the Rhaetian Quehala Formation of the central BNSZ, a clastic succession. Norian rocks have been described from the central BNSZ (Mailonggang Formation) 12 , the Lhasa Terrane (Mailonggang Formation and Jiangrang Formation) 30 – 33 , and the South Qiangtang Terrane (Riganpeico Formation) 34 where they are made up largely of thick-bedded limestone and dolomite (Fig. 4 ).…”
Section: Discussionmentioning
confidence: 99%
“… Figure 4 The Norian (A) and Rhaetian (B) sediments in the BNSZ, Lhasa Terrane, and South Qiangtang Terrane. ①-Mailonggang section (conodonts) 30 ; ②-Yawa section (conodonts and corals) 32 ; ③-DibuCo section (conodonts) 31 ; ④-NamuCo section (corals) 33 ; ⑤,⑥-sections within the South Qiangtang Terrane (corals) 34 ; ⑦-DaruCo section (corals) 12 ; ⑧-ZhaxicobuCo section (conodonts; this paper); LS Lhasa Terrane, SQ South Qiangtang Terrane, LSSZ LongmuCo-Shuanghu Suture Zone, BNSZ Bangong-Nujiang Suture Zone, IYSZ Indus-Yarlung Zangbo Suture Zone. Red solid lines define boundaries between different tectonic terranes.…”
Section: Discussionmentioning
confidence: 99%
“…The debate centers on three opinions regarding the tectonic significance of the BNSZ. One view holds that the BNSZ was not represented by an ocean during the Triassic 6 , 8 , 11 , 12 . A contrary argument maintains that the BNSZ was a long-standing ocean that existed from Late Paleozoic to Cretaceous time 2 , 5 .…”
Section: Introductionmentioning
confidence: 99%
“…1 B). These deposits include cherty strata that host Carnian radiolarians and conodonts described from the Dingqing area 16 ; chert-dominated deposits containing Ladinian radiolarians in the Gajia area 14 ; and dolomite-dominated rocks bearing Late Permian corals and Early Triassic to Anisian conodonts and limestone that yields Norian corals documented from the Ban’ge area 12 . These findings confirm that Triassic deposits are well represented in the central and east BNSZ (Fig.…”
Section: Introductionmentioning
confidence: 99%
“…1 ). The marked similarity of the Triassic succession of the central BNSZ with deposits of the Lhasa and Qiangtang terranes suggests that the BNSZ was an extension of these terranes rather than a geographic barrier separating them in Late Permian to Triassic time 12 .…”
The Bangong-Nujiang Suture Zone (BNSZ) of Tibet (Xizang) has been interpreted to represent a relic of the Bangong-Nujiang Ocean. However, the existence of this ocean during Triassic time remains a point of contention. A sedimentary succession spanning the Upper Permian through Triassic described from the central BNSZ suggests that the Lhasa and South Qiangtang terranes were contiguous thus negating the existence of a terrane-separating ocean during Triassic time. However, the apparent lack of Triassic deposits in the west BNSZ has called into question the existence of Triassic deposits in the central region of the BNSZ. Our biostratigraphic work in the Wuga Formation of the Gaize area has yielded abundant Norian conodonts thus confirming the existence of Upper Triassic deposits in the west BNSZ. The clastic deposits of the Wuga Formation are herein interpreted to be of Rhaetian age. Moreover, intercalated limestone and chert are termed the Dongnale Formation of Norian age. The Norian to Rhaetian succession can be correlated with strata of the central BNSZ as well as with deposits of the Lhasa Terrane and the South Qiangtang Terrane. Similar stratigraphies among these regions through the Late Triassic suggests a shared depositional setting and that the BNSZ was not an ocean in Norian and Rhaetian time.
A new foraminiferal fauna is reported from the upper part of the Xiala Formation in the Zhari Namco section in the central Lhasa Block, which contains three species of fusulines and 26 species of small foraminifers. The presence of Reichelina and Codonofusiella in the fauna suggests a Wuchiapingian age. A review of the Lopingian faunas in several localities in the Lhasa Block indicates that this block was under a shallow marine environment during the Lopingian, rather than an uplifted terrestrial environment as previously recognized. The Lopingian palaeobiogeography as well as the sequences of the Lhasa Block differs greatly from the adjacent South Qiangtang, Karakorum and South Pamir blocks, and the Tethys Himalaya region of the Indian Plate. It further suggests that the Lhasa Block was separated from the South Qiangtang Block in the north by the Bangong‐Nujiang Ocean and the Tethys Himalaya area in the south by the Neotethys Ocean during the Lopingian time. Furthermore, the dissimilarity of the Guadalupian and Lopingian strata and faunas between the Lhasa and Karakorum blocks and similarity between the Lhasa and Tengchong blocks, may suggest that the Lhasa and Tengchong blocks were linked together during the Permian.
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