Carbon isotopic excursions and detailed ammonoid and conodont biostratigraphies around Smithian–Spathian boundary in the Bac Thuy Formation, Vietnam

Komatsu, Toshimitsu; Takashima, Reishi; Shigeta, Yasuteru; Maekawa, Takumi; Tran, Huyen Dang; Cong, Tien Dinh; Sakata, Susumu; Dinh, Hung Doan; Takahashi, Osamu

doi:10.1016/j.palaeo.2016.04.017

Cited by 24 publications

(13 citation statements)

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“…Late Smithian occurrences of Nv. pingdingshanensis were also reported by Orchard and Zonneveld ( 2009 ), Komatsu et al ( 2016 ), Leu et al ( 2019 ) and Maekawa and Jenks ( 2021 ). As a consequence, the FO of Nv.…”

Section: Discussionsupporting

confidence: 62%

“…The Nanpanjiang basin, presently situated at the southern margin of the South China Block, includes several isolated platforms and extends as far south as the “An Chau” basin in northern Vietnam (Enos, 2006 ; Feng et al, 2015 ; Galfetti et al, 2008 ; Komatsu et al, 2016 ), where intercalated volcanic rocks become abundant. In the Nanpanjiang basin, Early Triassic marine record includes abundant benthos, ammonoids and conodonts (e.g.…”

Section: Introductionmentioning

confidence: 99%

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A Unitary Association-based conodont biozonation of the Smithian–Spathian boundary (Early Triassic) and associated biotic crisis from South China

et al. 2022

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The Smithian–Spathian boundary (SSB) crisis played a prominent role in resetting the evolution and diversity of the nekton (ammonoids and conodonts) during the Early Triassic recovery. The late Smithian nektonic crisis culminated at the SSB, ca. 2.7 Myr after the Permian–Triassic boundary mass extinction. An accurate and high-resolution biochronological frame is needed for establishing patterns of extinction and re-diversification of this crisis. Here, we propose a new biochronological frame for conodonts that is based on the Unitary Associations Method (UAM). In this new time frame, the SSB can thus be placed between the climax of the extinction and the onset of the re-diversification. Based on the study of new and rich conodont collections obtained from five sections (of which four are newly described here) in the Nanpanjiang Basin, South China, we have performed a thorough taxonomical revision and described one new genus and 21 new species. Additionally, we have critically reassessed the published conodont data from 16 other sections from South China, and we have used this new, standardized dataset to construct the most accurate, highly resolved, and laterally reproducible biozonation of the Smithian to early Spathian interval for South China. The resulting 11 Unitary Association Zones (UAZ) are intercalibrated with lithological and chemostratigraphical (δ13Ccarb) markers, as well as with ammonoid zones, thus providing a firm basis for an evolutionary meaningful and laterally consistent definition of the SSB. Our UAZ8, which is characterized by the occurrence of Icriospathodus ex gr. crassatus, Triassospathodus symmetricus and Novispathodus brevissimus, is marked by a new evolutionary radiation of both conodonts and ammonoids and is within a positive peak in the carbon isotope record. Consequently, we propose to place the SSB within the separation interval intercalated between UAZ7 and UAZ8 thus leaving some flexibility for future refinement and updating.

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Section: Discussionsupporting

confidence: 62%

Section: Introductionmentioning

confidence: 99%

A Unitary Association-based conodont biozonation of the Smithian–Spathian boundary (Early Triassic) and associated biotic crisis from South China

et al. 2022

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“…The late Smithian was one of the hottest intervals during Early Triassic time, with extreme temperatures both in the upper tropical ocean and on land (Sun et al 2012). This is reflected by a pronounced negative δ 13 C excursion (CIE), with a magnitude of ∼6 ‰, in both carbonate and organic material (Payne et al 2004;Galfetti et al 2007b;Tong et al 2007;Horacek et al 2009;Hermann et al 2011;Clarkson et al 2013;Grasby et al 2013a,b;Wignall et al 2016;Komatsu et al 2016). During this Late Smithian Thermal Maximum (LSTM), upper water column temperatures at equatorial latitudes are estimated to have approached 38°C, with sea surface temperature possibly exceeding 40°C, as inferred from oxygen isotope ratios of conodont apatite (Sun et al 2012).…”

Section: Introductionmentioning

confidence: 99%

The Smithian–Spathian boundary in North Greenland: implications for extreme global climate changes

et al. 2019

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Smithian–lower Anisian strata in Peary Land, North Greenland, were deposited at ∼45° N on the northern margin of Pangaea in offshore to upper shoreface settings. The well-constrained succession (palynology and ammonite biostratigraphy) documents a remarkable shift from lycophyte spore-dominated assemblages in the upper Smithian to gymnosperm pollen-dominated ones in the lower Spathian in concert with a marked shift of +6 ‰ in δ13Corg. Correlation with other Smithian–Spathian boundary sections that record terrestrial floral changes indicates that the recovery of gymnosperms began earlier in the mid-latitudes of the Southern Hemisphere than in the Northern Hemisphere. The lycophyte-dominated Late Smithian Thermal Maximum is here interpreted as reflecting dry and hot climatic conditions with only brief seasonal precipitation unable to sustain large areas of gymnosperm trees, but able to revive dehydrated lycophytes. This suggests that the Late Smithian Thermal Maximum was a time of widespread aridity, which is also supported by red bed deposition in many areas globally, even as far south as Antarctica. The shift to gymnosperm-dominated vegetation during the cooling across the Smithian–Spathian boundary reflects a change to seasonally more humid climatic conditions favouring gymnosperm recovery, and could have been initiated by increased albedo over land due to the widespread aridity during the Late Smithian Thermal Maximum. The recovery of gymnosperm vegetation would have helped to draw down CO2 from the atmosphere and exacerbate global cooling.

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“…Wang et al (2019) placed the SSB well after the onset of the CIE in South China, based on the first occurrence of the conodont index Novispathodus pingdingshanensis. However, the first occurrence of this species appears to be globally diachronous (Zhang et al, 2019), as it has been shown to co-occur with late Smithian taxa as well (e.g., Xenoceltites, Komatsu et al, 2016;Goudemand et al, 2012;Orchard & Zonneveld, 2009; Glyptophiceras, Romano et al, 2013;Scythogondolella milleri, Leu et al, 2018). The late Smithian extinction unfolded in a stepwise pattern, with a first diversity decrease of ammonoids during the early late Smithian Wasatchites tardus Zone (Brühwiler et al, 2010).…”

mentioning

confidence: 99%

Are Early Triassic extinction events associated with mercury anomalies? A reassessment of the Smithian/Spathian boundary extinction

Hammer

Jones

Schneebeli‐Hermann

et al. 2019

Earth-Science Reviews

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High concentrations of mercury, possibly connected with widespread volcanism of the Siberian Traps, have previously been associated with the Smithian/Spathian (Early Triassic) boundary (SSB) in the Sverdrup Basin, Tethyan sections in India and China, as well as with a shallow-water record in western Spitsbergen. We confirm this Hg/TOC anomaly in the deeper water record at Wallenbergfjellet, central Spitsbergen. However, both paleontological age control and carbon isotopes indicate that the Hg anomaly occurred mainly within strata of middle Smithian age.Therefore, this Hg anomaly is unlikely to be directly causally related to mechanisms contributing to the late Smithian global extinction of nektonic faunas. The TOC and trace element data suggest generally more oxygenated conditions during the Smithian compared to the Spathian, which is at odds with the hypothesis that oxygen depletion may have been a global kill mechanism for the SSB extinction. Further work is needed to assess if precise timing and paleogeographic distribution of anoxia shows any consistent pattern or not during the Smithian and Spathian. The very abrupt lower limb of the positive carbon isotope excursion (CIE) and the coarser grain size immediately below the boundary between the Lusitaniadalen Member and the Vendomdalen Member indicate a substantial stratigraphic gap of latest Smithian age, a previously neglected signal shared with many other boreal SSB sections. Ammonoid age control also indicates that the onset of the late Smithian gap in the high 2 latitudes was earlier than in the Tropics. The gradual end of the positive CIE contrasts with the frequent spike shape observed in tropical shelf records and is definitively earliest Spathian in age.The middle Smithian Hg anomaly in the Boreal record is only visible in the Hg/TOC values, and is associated with a possible shift in organic matter type from terrestrial to marine in the case of Spitsbergen. This suggests that the middle Smithian Hg/TOC anomaly in Spitsbergen may not unequivocally originate from volcanism, and calls for additional caution before interpreting Hg spikes as a volcanic proxy.

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Carbon isotopic excursions and detailed ammonoid and conodont biostratigraphies around Smithian–Spathian boundary in the Bac Thuy Formation, Vietnam

Cited by 24 publications

References 38 publications

A Unitary Association-based conodont biozonation of the Smithian–Spathian boundary (Early Triassic) and associated biotic crisis from South China

A Unitary Association-based conodont biozonation of the Smithian–Spathian boundary (Early Triassic) and associated biotic crisis from South China

The Smithian–Spathian boundary in North Greenland: implications for extreme global climate changes

Are Early Triassic extinction events associated with mercury anomalies? A reassessment of the Smithian/Spathian boundary extinction

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