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Volume 14
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Reply published on 31 July 2024, see Minerals 2024, 14(8), 789.
Comment of Minerals 2024, 14(3), 246.
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Comment

Comment on Zhang et al. New Age Constraints of the Bilong Co Oil Shale in the Qiangtang Basin, Northern Tibet: Evidence from In Situ U–Pb Dating and Palaeontology. Minerals 2024, 14, 246

by
Jiarun Yin
School of Earth Sciences and Resources, China University of Geosciences (Beijing), 29 College Road, Beijing 100083, China
Minerals 2024, 14(8), 777; https://doi.org/10.3390/min14080777
Submission received: 7 April 2024 / Revised: 12 June 2024 / Accepted: 26 July 2024 / Published: 30 July 2024
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Abstract

:
Two species in question, Tiltoniceras sp. (Zhang et al., 2024, p. 6, Figure 5A,B,E) and “Hildoceratidae sp.”, belong to the misidentification of ammonites, the conclusion drawn by Zhang et al. (2024) lacks reliable evidence from ammonite biochronology to support the U–Pb Dating.

1. Introduction

Recently, a paper proposed the use of two ammonite species for dating Biluoco shale [1]. However, I believe there are inaccuracies in the identification of these specimens. The two species in question are Tiltoniceras sp. [1] (p. 6, Figure 5A,B,E) and “Hildoceratidae sp.” [1] (p. 6, Figure 5C,D,F).

2. Concerning Tiltoniceras sp.

The genus Tiltoniceras [2] is characterized by its moderate to very involute, compressed form, nearly flat whorl sides with rounded umbilical edges and a strong keel on the venter but no sulci; the ribs are moderately strong to fine, striate or smooth, straight, or gently sigmoidal, and strongly projected forward on the venter, but never forming the falcoid or falcate ribbing pattern like that of the specimens shown by Tiltoniceras sp. [1] (p. 6, Figure 5A,B,E). These specimens [1] (p. 6, Figure 5A,B,E) belong to Oppellidae rather than Hildoceratidae, because these specimens lack the diagnostic feature of Tiltoniceras: “…strong keel on the venter but no sulci of Tiltoniceras” [3].
The specimens referred to as “Tiltoniceras sp.” [1] (p. 6, Figure 5A,B,E) should be assigned to Oxycerites sp., and they are comparative with either Oxycerites aspidoides (Oppel, 1857) [4] (see Figure 1 ((Left) A–K) or Oppelia (Oxycerites) nivennensis Grossouvre [5] (p. 25, pl. 4., Figure 6). O. (O.) nivennensis occurs from the topmost Bajocian up to the basal Middle Bathonian [5] (p. 25). Previously, the same specimens as those reported [1] (p. 6, Figure 5A,B) were repeatedly but wrongly referred to as Harpoceras sp. [6,7], Cleviceras cf. elegans (Sowerby) [8,9,10,11], or Harpoceras sp. [8,12,13,14,15,16] [in the Bilong Co (=Biluoco) oil shale, which has been recently reviewed [17] and presented here (see Figure 1 ((Left) A–K)).
In the authors’ reply to my comment, they display another specimen which has been referred to as Tiltoniceras sp. (Figure 1. Comparison of the Tibetan ammonite with ammonite fossils from various regions. (A) Xizang specimen Tiltoniceras sp., lateral view, EH4, Bilong Co section, the Quse Formation, Toarcian). Interestingly, this specimen is actually closer to Oxycerites than those identified as Tiltoniceras in their paper, as it exhibits a highly involute shell and the characteristic ribbing style of Oxycerites. It seems the authors have been misled by this identification of Figure 1A, Xizang specimen Tiltoniceras sp.

3. Regarding “Hildoceratidae sp.”

First, the use of “Hildoceratidae sp.” in the taxonomic article [1] is not standardized. Furthermore, classifying ammonite samples only as part of the Hildoceratidae family, without specifying their genus and species, may not significantly contribute to stratigraphic age. This is because within the scope of a family, there could be a multitude of genera and species that might have appeared at different periods in geological history. Therefore, for a more accurate determination of stratigraphic age, it is typically necessary to classify fossils in a more detailed and precise manner, at least to the genus level, and even to the species level if possible. Only then can these fossils serve as index fossils in biostratigraphy, helping us to determine the age of the strata more accurately.
Secondly, if ammonites from the Hildoceratidae family have been identified, further studies might be needed to determine their specific genus and species. This will allow these fossils to be utilized more effectively in determining the age of the strata.
In my view, these small individual specimens [1] (Figure 5C–F) are likely juvenile specimens of Oxycerites. However, due to poor preservation and compression deformation, their identification results do not provide definitive stratigraphic value.

4. Conclusions

It may not be advisable to classify these poorly preserved specimens as Tiltoniceras sp., as they exhibit more characteristics of Oxycerites. As a result, the misidentification of these ammonites leads to a lack of solid evidence from ammonite biochronology to substantiate the U–Pb dating presented [1].

Conflicts of Interest

The authors declare no conflict of interest.

References

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Minerals 14 00777 g001
Figure 1. (Left) (A–K): Oxycerites aspidoides (Oppel, 1857) [4]; (A), Oxycerites aspidoides and bivalve shell (Bositra and Pseudomytiloides) bed A2020CUGB107. Locality H, the Buqu Formation (QN89), the upper Bajocian. (B), lateral view, internal mould, −108. Locality H, the Buqu Formation, the upper Bajocian. (C), lateral view of macroconchs (body chamber), −109. Locality H, the Buqu Formation (QN89), the upper Bajocian. (D1), internal mould, lateral view, microconchs with lappet, (D2) enlargement of the lappet, −123. Locality H, the Buqu Formation (QN89), the upper Bajocian. (E), lateral view, external mould, −124. Locality H, the Buqu Formation (QN89), the upper Bajocian. (F), lateral view, external mould, −103. Locality B, the Buqu Formation, the upper Bajocian. (G), external mould, X2, −106. Locality B, the Buqu Formation, the upper Bajocian. (H), external mould, Locality Y, the Buqu Formation, the upper Bajocian. −7027. (I), lateral view, internal mould, microconchs (?), −126. Locality H, the Buqu Formation (QN89), the upper Bajocian. (J), internal mould, highly compacted, −7032. Locality Y, the Buqu Formation, the upper Bajocian. (K), fragment of macroconchs (?), external mould, lateral view, −127. Locality H, the Buqu Formation (QN89), the upper Bajocian. (Right) (A,B,E): Tiltoniceras sp. [1] (p. 6, C,D,F): “Hildoceratidae sp.” [1] (p. 6, Figure 5).
Figure 1. (Left) (A–K): Oxycerites aspidoides (Oppel, 1857) [4]; (A), Oxycerites aspidoides and bivalve shell (Bositra and Pseudomytiloides) bed A2020CUGB107. Locality H, the Buqu Formation (QN89), the upper Bajocian. (B), lateral view, internal mould, −108. Locality H, the Buqu Formation, the upper Bajocian. (C), lateral view of macroconchs (body chamber), −109. Locality H, the Buqu Formation (QN89), the upper Bajocian. (D1), internal mould, lateral view, microconchs with lappet, (D2) enlargement of the lappet, −123. Locality H, the Buqu Formation (QN89), the upper Bajocian. (E), lateral view, external mould, −124. Locality H, the Buqu Formation (QN89), the upper Bajocian. (F), lateral view, external mould, −103. Locality B, the Buqu Formation, the upper Bajocian. (G), external mould, X2, −106. Locality B, the Buqu Formation, the upper Bajocian. (H), external mould, Locality Y, the Buqu Formation, the upper Bajocian. −7027. (I), lateral view, internal mould, microconchs (?), −126. Locality H, the Buqu Formation (QN89), the upper Bajocian. (J), internal mould, highly compacted, −7032. Locality Y, the Buqu Formation, the upper Bajocian. (K), fragment of macroconchs (?), external mould, lateral view, −127. Locality H, the Buqu Formation (QN89), the upper Bajocian. (Right) (A,B,E): Tiltoniceras sp. [1] (p. 6, C,D,F): “Hildoceratidae sp.” [1] (p. 6, Figure 5).
Minerals 14 00777 g001
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MDPI and ACS Style

Yin, J. Comment on Zhang et al. New Age Constraints of the Bilong Co Oil Shale in the Qiangtang Basin, Northern Tibet: Evidence from In Situ U–Pb Dating and Palaeontology. Minerals 2024, 14, 246. Minerals 2024, 14, 777. https://doi.org/10.3390/min14080777

AMA Style

Yin J. Comment on Zhang et al. New Age Constraints of the Bilong Co Oil Shale in the Qiangtang Basin, Northern Tibet: Evidence from In Situ U–Pb Dating and Palaeontology. Minerals 2024, 14, 246. Minerals. 2024; 14(8):777. https://doi.org/10.3390/min14080777

Chicago/Turabian Style

Yin, Jiarun. 2024. "Comment on Zhang et al. New Age Constraints of the Bilong Co Oil Shale in the Qiangtang Basin, Northern Tibet: Evidence from In Situ U–Pb Dating and Palaeontology. Minerals 2024, 14, 246" Minerals 14, no. 8: 777. https://doi.org/10.3390/min14080777

APA Style

Yin, J. (2024). Comment on Zhang et al. New Age Constraints of the Bilong Co Oil Shale in the Qiangtang Basin, Northern Tibet: Evidence from In Situ U–Pb Dating and Palaeontology. Minerals 2024, 14, 246. Minerals, 14(8), 777. https://doi.org/10.3390/min14080777

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