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The measured Tangnale Formation section near the Langjiu Power Station, Zuozuo Township, Gar County. T 1-2 t, Tangnale Formation; P 3 x, Xiala Formation; HS-27, sample numbers and positions.
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Most geologists believe that there are no Early and Middle Triassic strata in the W. Gandisê stratigraphic subregion, but
the present authors have found Early Triassic conodonts for the first time in the Shiquanhe area, including five conodonts
genera (Form genera): Pachycladina, Neohindeodella, Cornudina, Hadrodontina and Hibbardella sp. etc. Then...
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Context 1
... section is located in the western part of Zuozuo Township, about 20 km east to Shiquanhe Town, in Gar County, Tibet (Figure 1). The section begins from the Langjiu Power Station (80°20′50″E, 32°23′58″N), and terminates near Tangnale (80°21′28″E, 32°29′38″N); it is about 10 km long, in which the succession of the Tri- assic system is as follows (Figure 2 ------Parallel unconformity------ Underlying strata: the Xiala Formation limestone ...
Context 2
... section is located in the western part of Zuozuo Township, about 20 km east to Shiquanhe Town, in Gar County, Tibet (Figure 1). The section begins from the Langjiu Power Station (80°20′50″E, 32°23′58″N), and terminates near Tangnale (80°21′28″E, 32°29′38″N); it is about 10 km long, in which the succession of the Tri- assic system is as follows (Figure 2 ------Parallel unconformity------ Underlying strata: the Xiala Formation limestone ...
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Citations
... Overlying clastic rocks can be correlated to the Dibuco Formation of Rhaetian to Early Jurassic (Wu et al., 2021c). Lower Triassic dolomite referred to as the Zuozuo Formation (Ji et al., 2007c) and the Tangnale Formation (Zheng et al., 2007) has been described from the Shiquanhe area west of the Longgar-Nanmulin SSR. The Lower Triassic Mujiuco Formation yielding the conodonts Pachycladina obliqua and Hadrodontina anceps have also been described from the Rendo area of Zhongba County and the Comai area in Angren County (Wu et al., , 2021a Liu et al. (2020) documented a sequence of Lower to Middle Triassic fine-grained clastic rocks containing bivalves that may have accumulated at the margin of the abyssal to semi-abyssal slope facies in the southern part of the Longgar-Nanmulin SSR, an area that had been considered to lack rocks of this age. ...
... Chen (2016) revealed the presence of Hardrontina in the P-H-P assemblage in the Gaize area, west BNSZ, and Wu et al. (2019) documented the presence of Hadrodontina and Pachycladina in deposits of the Shemari area of Ban'ge County. Elements of P-H-P assemblage Hadrodontina and Pachycladina have been reported from the western Shiquanhe area (Zheng et al., 2007), the Zhongba area , the Angren area (Wu et al., 2021a), and the Namuco area (Wu et al., 2017) of Gangdis. The occurrence of P-H-P assemblage in strata of North Qiangtang, South Qiangtang, BNSZ, and Gangdis suggest that these areas were part of the Asian province of the low latitude Tethys realm, lying in shallow water evaporite carbonate platform to coastal tidal or intertidal regions at the edge of Eurasia. ...
... The passive continental margin sedimentary system of the Eurasian continent lay to the north of the basin and shallowed to the north (Ji et al., 2008(Ji et al., , 2018a. This interpretation is based on the recognition of a Triassic marine succession in the original "Gangdis Old land area" (Ji et al., 2006(Ji et al., , 2007b(Ji et al., , 2007cWu et al., 2007;Zheng et al., 2007). The fundamental difference of the "two continents and one basin" model and the "three continents and two geosynclines" view is that the Gangdis and South Qiangtang blocks were marine sedimentary areas according to the former rather than regions of uplift and denudation during the Triassic (Ji et al., 2008;Ji et al., 2018b). ...
Rocks of the Qinghai-Tibetan Plateau (QTP) host abundant Triassic fossils. So far, the well established marine fossil sequences based on ammonoids, conodonts, bivalves, brachiopods, radiolarians, and terrestrial spora-pollen sequence have become standard for biostratigraphic correlation of the QTP. For much of Triassic time, the QTP occupied a marine setting as suggested by the dominance of marine deposits. The main sedimentary types represented in the Triassic successions include littoral to shallow marine clastic rocks, shallow marine carbonate platform carbonates, bathyal to abyssal slope carbonates intercalated with clastic and siliceous deposits, coal-bearing clastic strata contained within paralic facies deposits, and littoral and terrestrial volcaniclastic rocks. These deposits are organized into four stages in ascending order: (1) Early Triassic deposits that record marine transgression, including extensive shallow marine carbonate platform strata. (2) Middle Triassic Ladinian to Late Triassic Carnian deposits, including thin-bedded limestone, fine clastics, and siliceous rocks, that accumulated at greater depths than underlying Early Triassic strata and reflect the peak of the transgression. Magmatic activity appears to have occurred in some areas during this stage. (3) Late Triassic Norian deposits that record the onset of marine regression as suggested by the widespread occurrence of platform carbonates. It is noteworthy that stage 3 deposits of the Qin-Qi-Kun area in the northernmost region of the QPT is dominated by terrestrial strata and displays evidence of local erosion. (4) Late Triassic Rhaetian littoral and shallow marine clastic and coal-bearing deposits that preserve the record of continued marine regression continued. The Indus-Yarlungzangbo Suture Zone (IYSZ) appears to have been the rifting axis during Triassic time as suggested by sedimentary facies trends that reflect deepening to south and north. Thus, the Himalaya Block to the south of the IYSZ was part of the passive margin of Gondwana whereas the north side of the IYSZ, including the Gangdis (or Lhasa) and South Qiangtang blocks, belonged to the passive margin of Eurasia. The similarity of rocks of the Bangongco-Nujiang Suture Zone (BNSZ) to the north of the IYSZ with those of the Gangdis Block to the south and the South Qiangtang Block to the north does not support the contention that the BNSZ was a rift axis during Triassic time. Results of palaeobiological research also suggest that the IYSZ rather than BNSZ was a biogeographic boundary during the Triassic. Early and Middle Triassic break-up of Pangea was accompanied on the QTP by rifting along the IYSZ. The expression of crustal shortening induced by the Indosinian Orogeny on the QTP is largely a change of sedimentary facies induced by Late Triassic uplift. Deposits of the Gangdis to South Qiangtang regions of the QTP record a transition from shallow marine carbonate platform deposits to littoral and paralic coal-bearing strata. Moreover, the stratigraphic succession of the Qin-Qi-Kun area preserves a transition from littoral clastic deposits to terrestrial facies and local erosion.
... We reinvestigated the conodont succession at the Tulong section, in order to improve the resolution of conodont biostratigraphy and provide a better time scale for correlation among the Himalaya Terrane (mid-latitudes of southern hemisphere), South China, Europe, and North America (low-and mid-latitudes of northern hemisphere). (Tian, 1982;Garzanti et al., 1998); 2, Selong section (Yao and Li, 1987;Orchard et al., 1994;Wang and Wang, 1995;Mei, 1996;Jin et al., 1996;Garzanti et al., 1998;Wang et al., 2017;Yuan et al., 2018); 3, Pulang area (Zhao and Zhang, 1991); 4, Zhada area (Zhao and Zhang, 1991); 5, Mailonggang section (Ji et al., 2003); 6, Zishisang section (Zhang et al., 2005); 7, Talikeganlishan section (Zhu et al., 2006); 8, Dibucuo section Ji et al., 2007); 9, Langjiu section (Zheng et al., 2007); 10, Shemari section (Wu et al., 2013(Wu et al., , 2019; 11, Wenbudangsang section (Zhou, 2012;Wu et al., 2014); 12, Rendo area (Wu et al., 2018); 13, Gyirong section (Garzanti et al., 1998); 14, Dzaghar section (Garzanti et al., 1998 ...
The Himalaya Terrane of southern Tibet exposes successive shallow-marine carbonate deposits from the Lower to Upper Triassic, and is a key region for studying the Triassic conodont biostratigraphy at the northern margin of the Indian Plate. On the basis of newly collected samples from the Kangshare and Laibuxi formations at the Tulong section, 11 conodont species of 7 genera were identified, and four conodont zones were established, namely, the Novispathodus abruptus Zone (lower Spathian, first reported in Tibet), the Columbitella jubata Zone (middle Spathian), the Triassospathodus symmetricus Zone (upper Spathian), and the Chiosella timorensis Zone (lowermost Anisian) in ascending order. The first occurrence (FO) of Chiosella timorensis indicates the Olenekian–Anisian boundary (OAB) at Bed 25, upper part of the Kangshare Formation. The regional and global correlation of these conodont zones is synthesized.
... It is only recently that the dolomite has yielded Early Triassic conodonts from shallow water facies exposed in the Namuco area (Wu et al., 2017). Lower Triassic deposits of the dolomite-based succession include the Tangna'le Formation of the westernmost Lhasa Terrane (Zheng et al., 2007) and the Mujiuco Formation of the central Lhasa Terrane (Cheng et al., 2002;Wu et al., 2017;Ji et al., 2018b) (Fig. 5). Details of Middle Triassic deposits of the dolomite-based succession are lacking though preliminary field investigations suggest they are dominated by limestone-bearing conglomerate (Ji et al., 2018b) (Fig. 5). ...
... Conodont biostratigraphy suggests that Triassic marine carbonates accumulated in the Coqen and Shiquanhe areas (Fig. 1) (e.g., Ji et al., 2006Ji et al., , 2007Zheng et al., 2007). However, these data yield conflicting interpretations as well. ...
... Recognition of Triassic dolomite in the Comai area confirms that the dolomite deposits described from the Rendo section and Namuco section can be correlated with each other (Fig. 6D). It is noteworthy that the dolomite maintains a thickness of greater than 1000 m from the westernmost Shiquanhe area (Zheng et al., 2007) to the eastern Xainza and Namuco areas (Cheng et al., 2002;Wu et al., 2018). Thus, it appears that the eastern Lhasa Terrane, like the west, was part of an extensive carbonate platform (Fig. 6D). ...
... It is only recently that the dolomite has yielded Early Triassic conodonts from shallow water facies exposed in the Namuco area (Wu et al., 2017). Lower Triassic deposits of the dolomite-based succession include the Tangna'le Formation of the westernmost Lhasa Terrane (Zheng et al., 2007) and the Mujiuco Formation of the central Lhasa Terrane (Cheng et al., 2002;Wu et al., 2017;Ji et al., 2018b) (Fig. 5). Details of Middle Triassic deposits of the dolomite-based succession are lacking though preliminary field investigations suggest they are dominated by limestone-bearing conglomerate (Ji et al., 2018b) (Fig. 5). ...
... Conodont biostratigraphy suggests that Triassic marine carbonates accumulated in the Coqen and Shiquanhe areas (Fig. 1) (e.g., Ji et al., 2006Ji et al., , 2007Zheng et al., 2007). However, these data yield conflicting interpretations as well. ...
... Recognition of Triassic dolomite in the Comai area confirms that the dolomite deposits described from the Rendo section and Namuco section can be correlated with each other (Fig. 6D). It is noteworthy that the dolomite maintains a thickness of greater than 1000 m from the westernmost Shiquanhe area (Zheng et al., 2007) to the eastern Xainza and Namuco areas (Cheng et al., 2002;Wu et al., 2018). Thus, it appears that the eastern Lhasa Terrane, like the west, was part of an extensive carbonate platform (Fig. 6D). ...
The Lhasa Terrane of Tibet is critical to understanding Early Triassic crustal convergence of Gondwana and Eurasia. However, its palaeo-position during this period remains obscure. This paper considers the disputed tectonic nature of the Lhasa Terrane during Triassic time. The debate has taken the form of two schools of thought regarding the Lhasa Terrane. One holds that the terrane was a stable carbonate platform during Triassic time. The opposing view maintains that the Lhasa Terrane occupied a compressional orogenic belt. These contrasting explanations stem mainly from the absence of a sedimentary record, especially in the southern part of the Lhasa Terrane of Tibet. We report on results of a biostratigraphic investigation of a dolomite unit considered to be of Guadalupian age in the Comai area, southern Lhasa Terrane. This work yielded the ellisonid conodont species Pachycladina rendona n. sp. Wu and Ji suggesting an Early Triassic age and a low latitude depositional setting of the dolomite. Further, these findings favor correlation of the dolomite with the upper member of the Upper Permian to Lower Triassic Mujiuco Formation. Results of the present study, especially the newly collected Pachycladina fauna, suggest that the Lhasa Terrane was an element of a low-latitude carbonate platform that had separated from Gondwana during the Early Triassic. It is hoped that our findings will promote further research of the Triassic sedimentary history and paleogeographic evolution of the Lhasa Terrane.
... More recently, work has focused on the west Gangdise and southern Qiangtang regions. In the Zozo area of Shiquanhe County, key PTB conodonts have been discovered, such as the Late Permian (Changhsingian) Neogondolella changxingensis (Ji et al., 2007b), Early Triassic (Induan to Olenekian) taxa including rare specimens of Neospathodus and Gladigondolella (Ji et al., 2007b), and relatively abundant Pachycladina (Zheng et al., 2007). Similarly, the late Olenekian species N. homeri was found in South Qiangtang, north of the Bangongco-Nujiang suture zone (Zhang et al., 2005). ...
Sorkh Shale Formation in Rabat-e-Shur stratigraphic section, west of the Tabas Depression, has been biostratigraphically investigated in this research. The Sorkh Shale Formation, with 48 meters thickness in this section, consists of shale, marl, and marly limestones, which are underlain by the Permian Jamal Formation and are overlain by the Triassic Shotori Formation dolomites. Nine conodont species belonging to four genera, Ellisonia, Hadrodontina, Parachirognathus, and Pachycladina were identified for the first time from this formation. The mentioned conodont assemblage is divided into three biozones: Hadrodontina aequabilis, Hadrodontina anceps, and Pachycladina obliqua. These taxa are in good agreement with the previously reported euryhaline assemblages from the near-shore and shallow water Western Tethyan realms in the south and east of Europe in the Early Triassic (Late Griesbachian-Middle Smithian). These conodont biozones are used for a better understanding of the distribution and affinities of the Early Triassic conodonts in West Asia, their paleobiogeographical rank, their significant role in the Early Triassic chronostratigraphy and their importance in bio-correlation of different section worldwide. Examination of the conodont alteration index of the obtained taxa from the Sorkh Shale Formation demonstrates CAI=5 during the late Griesbachian, CAI=4 in the Smithian, and CAI=6-8 in the Dienerian substages which is placed in the barren Zone for hydrocarbon production.
Biostratigraphical, geochemical and palaeomagnetic studies have demonstrated that the Lhasa Terrane occupied a low‐latitude southern hemisphere region during Late Permian to Early Triassic time. However, the palaeogeographical relationship of the South Qiangtang and the Lhasa terranes remains a topic of debate. The principal dispute focusses are on whether the Bangong‐Nujiang Suture Zone (BNSZ) separating the terranes was an ocean during the Late Permian to Early Triassic. Resolution of this problem requires the recognition and investigation of Permian ‐ Triassic boundary (PTB) deposits and fossils of the Lhasa Terrane, especially proximal to the E‐W trending Longgar‐Gongbujiangda Fault, a region that has heretofore been considered devoid of these deposits. Our investigation of the Longgar area reveals that carbonate deposits correlated with the Middle Permian Xiala Formation are similar to PTB rocks described from elsewhere. We recovered conodont faunas spanning the Wuchiapingian and Changhsingian stages of the Permian and the Early Triassic Olenekian stage. Our results demonstrate that the studied carbonate succession ranges from the Upper Permian to the Upper Triassic (perhaps to the Lower Jurassic). The documented conodont succession demonstrates that PTB strata accumulated in the Longgar area. Thus, Late Permian and Early Triassic conodonts described from the Lhasa Terrane suggest a connection with the South Qiangtang Terrane. The BNSZ during this period of time was part of a carbonate platform that connected the Lhasa Terrane and the South Qiangtang Terrane.
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 never been excavated and thus are considered to be absent. This research, however, reveals that fossils aged from the Late Permian to Anisian of the Middle Triassic and Norian of the Late Triassic have been preserved in the central Bangong-Nujiang Suture Zone, which provides evidence of Upper Permian to early Middle Triassic deposits and provides new insights on the Upper Triassic strata as well. A new Triassic strata succession is thus proposed for the Bangong-Nujiang Suture Zone, and it demonstrates great similarities with those from Lhasa to the south and Qiangtang to the north. Therefore, we deduce that the Bangong-Nujiang Suture Zone was under a similar depositional setting as its two adjacent terranes, and it was likely a carbonate platform background because limestones were predominant across the Triassic. The newly acquired biostratigraphic data indicate that Lhasa and Qiangtang could not have been located on two separate continents with disparate sedimentary settings; therefore, the Bangong-Nujiang Suture Zone likely did not represent a large ocean between them. This conclusion is supported by lithostratigraphic and paleomagnetic research, which revealed that Lhasa and Qiangtang were positioned at low to middle latitudes during the Early Triassic. Combining this conclusion with fossil evidence, we suggest that the three main Tibetan terranes were in the same palaeobiogeographic division with South China, at least during the Latest Permian to Early Triassic. The Early Triassic conodont species Pachycladina obliqua is probably a fossil sign of middle to low latitudes in palaeogeography.
