Wang et al Newsletters on Stratigraphy 48(3) 241-

1. Introduction

South China is an internationally significant region forthe study of Upper Ordovician stratigraphy, havingbeen selected as the site of the Global Boundary Stra-totype Section and Point (GSSP) for the base of the Hirnantian Series, at the Wangjiawan section near

Yichang, western Hubei (Chen et al. 2006). High-reso-lution correlation of Hirnantian strata is vitally impor-tant for a better understanding of the end-Ordovicianmass extinction event that was associated with exten-sive global cooling and glaciation. In South China, theHirnantia fauna-bearing Kuanyinchiao Formation,which is interpreted as representing cool-water carbon-

Newsletters on Stratigraphy, Vol. 48/3 (2015), 241–252 Article Published online June 2015; published in print August 2015

Late Hirnantian (latest Ordovician) carbonate rocks and shelly fossils in Shiqian,northeastern Guizhou, Southwest China

Guangxu Wang1, Renbin Zhan1, Ian G. Percival2, Bing Huang1, Yue Li3, and Rongchang Wu3

With 7 figures

Abstract. The Kuanyinchiao Formation has generally been regarded as representing the only carbonate sediments deposited during the Hirnantian (Late Ordovician) interval in South China, where the HirnantianGSSP is situated. Reinvestigation of several key Ordovician–Silurian boundary sections in Shiqian, north-eastern Guizhou Province, Southwest China, reveals a lithologically distinct carbonate unit with abundantshelly fossils, including tabulate and rugose corals, conodonts, brachiopods, trilobites and stromatoporoids,many showing close Silurian affinities and suggesting a level stratigraphically much higher than the Kuanyin -chiao Formation. This observation, together with further evidence that graptolites indicative of the Akido-graptus ascensus biozone are present in immediately overlying rocks at a nearby section, implies that theseshelly fossiliferous strata are of latest Hirnantian age (possibly straddling the Ordovician–Silurian boundary).Hence they were most likely deposited after the Hirnantian glaciation, rather than representing glacial coolwater sediments (the Kuanyinchiao Formation) as was previously thought. Ordovician–Silurian boundary se-quences in South China typically reflect global glacio-eustatic sea-level changes. Owing to their unique lithol-ogy and palaeontology, these newly recognized carbonate rocks, here formally named the Shiqian Formation,add substantially to our knowledge of Ordovician–Silurian stratigraphy in this region.

Key words. Hirnantian, Ordovician, Carbonates, Glaciation, Fossils, South China

© 2015 Gebrüder Borntraeger, Stuttgart, GermanyDOI: 10.1127/nos/2015/0062

www.borntraeger-cramer.de0078-0421/2015/0062 $ 3.00

Authors’ addresses:1 State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Acad-emy of Sciences, Nanjing 210008, China. E-Mail: [email protected], [email protected], [email protected] Geological Survey of New South Wales, 947-953 Londonderry Road, Londonderry, NSW 2753, Australia. E-Mail:[email protected] Key Laboratory of Economic Stratigraphy and Palaeogeography, Nanjing Institute of Geology and Palaeontology, Chi-nese Academy of Sciences, Nanjing 210008, China. E-Mail: [email protected], [email protected] author: Guangxu Wang

eschweizerbart_xxx

ate sedimentation, is conformably or disconform ablyoverlain by shales or mudstones of the transgressiveLungmachi Formation (assigned mainly to the Llan-dovery Series of the Lower Silurian). Hence there areno reliable records of postglacial carbonate rocks andshelly fossils through the Ordovician–Silurian transi-tion in this region (Rong et al. 2010, Zhan et al. 2010,Rong et al. 2011). The lack of a complete carbonate se-quence across the boundary is one of the major reasonsfor the problematical correlation between the GSSP

area and shallow-water carbonate platforms in low lat-itudes, where graptolites are either absent or very rare(Delabroye and Vecoli 2010, Bergström et al. 2012).

This paper focuses on the extensively exposed Ordovician–Silurian boundary carbonates in the Shi -qian area of northeastern Guizhou, Southwest China(Fig. 1). Following Ge et al. (1979), who initially confirmed the presence of boundary strata at Xiang-shuyuan and nearby localities (which they called the“Kuanyinchiao Bed”), Hu et al. (1983) correlated all

Guangxu Wang et al.242

Fig. 1. Localities of the Ordovician–Silurian boundary sections (black triangles in right panel) cited in this study. Note thatthe Longkou-Kuaizishan section (Shiqian County) and the Wenjiadian section (Sinan County) are not shown (see text forinformation on their localities).

eschweizerbart_xxx

these rocks with the Kuanyinchiao Formation. Thisview has subsequently been widely accepted (e. g., Heand Chen 2003, Li 2004, Li et al. 2005, Rong et al.2011, Wang 2013).

Our recent extensive investigation in this area, however, indicates the presence of late Hirnantian car-bonates containing shelly fossils, which necessitates a revision of the stratigraphic framework for theserocks. Preliminary results have been briefly reported(Wang and Zhan 2014, Wang et al. 2014). The presentpaper aims to present a comprehensive elaboration ofthese results, and to further consider their stratigraphicand palaeogeographical implications. A new litho -stratigraphic name, the Shiqian Formation, is proposedfor the only known carbonate rocks of late Hirnantianage in China.

2. Lithostratigraphy and shelly fauna

In the Shiqian area, Ordovician–Silurian boundarystrata crop out at many localities (Fig. 1). These rocksdisconformably overlie the middle Katian-age Linh -siang Formation (previously referred to as the Chien -tsaokou Formation by Hu et al. 1983, He and Chen2003), and in turn are disconformably overlain by the“Lungmachi Formation” (Ge et al. 1979, Hu et al.1983, Rong and Zhan 2004). According to Hu et al.(1983), uneven erosion surfaces are present on the topsurface of the Linhsiang Formation and also on thoserocks here referred to the Shiqian Formation. The over-lying strata, which consist of grey yellow mudstone in-tercalated with several bioclastic limestone lenses (Niet al. 2015), are distinctly different from the typicalgraptolitic black shales of the Lungmachi Formation.

Rocks around the Ordovician–Silurian boundaryare variably developed in the area, as discussed below.

2.1 Tunping

The stratigraphically most complete boundary sequen -ce is exposed at this locality, about 8.3 km north ofShiqian county town, and hence the section can beused as a standard for correlation in the Shiqian area(Fig. 2a). Hu et al. (1983) recognized three lithologi-cally distinct intervals, in ascending order Interval 2,Interval 3 and Interval 4. Our observations on thelithology and palaeontology of Interval 4 show that itcan be subdivided into two layers (4a and 4b). The sequence is briefly described as follows:

(1) Interval 4b (Fig. 2a, g). This consists of bioclasticlimestone, 0.8 m thick. Corals present include therugosan Eurogrewingkia? sp., tabulates Paleo-favosites schmidti and Halysites sp., in addition totrilobite fragments (Hu et al. 1983, Wang 2014).

(2) Interval 4a (Fig. 2a, f). It is composed of grey in -tra clastic limestone with a thickness of 0.6 m. Nofossils have been found at this level (Wang 2014).

(3) Interval 3 (Fig. 2a, e). This layer consists of greyish yellow calcareous mudstone, 0.8 m thick.It yields abundant specimens of the rugosan Meitanolasma polytabulatum (He, 1986) (Wang2014). Hu et al. (1983) also documented the bra-chiopod “Hirnantia” sp., trilobite Dalmanitina sp.and bryozoan Hallopora sp. from this interval.

(4) Interval 2 (Fig. 2a). The lithology is grey argilla-ceous limestone, ranging in thickness from 0.3 mto 0.6 m. It contains abundant specimens of the rugosan Meitanolasma polytabulatum (Hu et al.1983, Wang 2014).

2.2 Other localities

South of the Tunping section, Ordovician–Silurianboundary strata are commonly represented by bioclas-tic limestone approximately 1 m thick at various local-ities. As depicted in Figure 3, intervals 2, 3 and 4a ofthe boundary rocks exposed in the Tunping section areentirely missing from those localities where the entirecarbonate succession is confined to strata correlatedonly with Interval 4b, based on similar lithology andcomparable fossil content. At Xiangshuyuan (Fig. 1),the layer contains tabulate corals Paleofavositesschmidti, Propora thebesensis and Halysites sp., ru-gosans Eurogrewingkia? sp., Grewingkia cf. bilater-alis and Axiphoria sp. (Wang 2014), and conodontOzarkodina aff. hassi (Wang and Aldridge 2010). Li etal. (2005) reported abundant peloids and ooids fromthis layer. At Laichao (Fig. 1, Fig. 2b, c, d), the tabu-lates Propora thebesensis and Catenipora sp. occur(Wang 2014), while at Sigou, the tabulate Sibiriolitessp. was documented from this horizon (Ge et al. 1979).Representative shelly macrofossils from the Ordovi-cian–Silurian boundary strata are illustrated in Fig. 4.

In addition, the equivalent limestone was reportedfrom Wenjiadian, Sinan County, about 20 km north-west of Shiqian county town. It contains the tabulatesCatenipora sp. and Schedohalysites sp., rugosansBrachyelasma sp. and Grewingkia sp., and stromato-poroid Ecclimadictyon (Ge et al. 1979).

Late Hirnantian (latest Ordovician) carbonate rocks 243

eschweizerbart_xxx

3. Age of carbonate rocks in the boundary successions

Based on regional correlations in South China (Zhanand Jin 2007), the Linhsiang Formation underlying theboundary succession is known to be of middle Katianage. The overlying “Lungmachi Formation” at Xiang-

shuyuan contains graptolites indicative of the Para -kidograptus acuminatus to Cystograptus vesiculosusbiozones, suggesting a middle Rhuddanian age (Rongand Zhan 2004). However, Li (2004) found graptolitesof the Akidograptus ascensus biozone in the basal partof the “Lungmachi Formation” at Longkou-Kuaizi -shan, Baisha, about 19 km west of Shiqian county


Fig. 2. Lithostratigraphy of the Ordovician–Silurian boundary succession at Tunping and Laichao, Shiqian, northeasternGuizhou. (a), (e)–(g) lithological succession at the Tunping section; (a) outcrop photo; (e) thin section of Interval 3 showinglithology of carbonaceous mudstone with rugose corals; (f) thin section of Interval 4a showing lithology of intraclastic lime-stone, note the presence of oncoids; (g) thin section of Interval 4b showing lithology of bioclastic limestone; (b)–(d) litho-logical succession at the Laichao section; (b) outcrop photo; (c) thin section of Interval 4b showing lithology of bioclasticlimestone; (d) enlargement of upper centre of the thin section in (c). Note that numbers and letters contained within circlesindicate stratigraphic divisions in this study. Scale bars represent 2 mm.

eschweizerbart_xxx

town, implying an age not younger than the earliestRhuddanian for this level, further constraining the ageof the boundary beds.

Variable development of the carbonates in the bound-ary successions at different localities further compli-cates this situation. Previous investigations have sug-gested that all the boundary intervals should be assignedto the early–middle Hirnantian Kuanyinchiao Forma-tion (Ge et al. 1979, Hu et al. 1983) (Fig. 5a). The pre-liminary scheme of Wang et al. (2014) considered Interval 4b to be stratigraphically much higher, whereasIntervals 2, 3 and 4a were retained within the Kuan -yinchiao Formation (Fig. 5b). Reassessment of the bio -stratigraphy of various fossil groups allows a more re-fined alternative scheme (Fig. 5c). In view of the faunaldifference between Interval 4b and the underlying stra-ta, it is appropriate to discuss their age assignment.

3.1 Age assignment of Interval 4b

Tabulate corals from this interval, consisting of Paleo -favosites, Propora and Halysites, have never been re-ported in the early–middle Hirnantian KuanyinchiaoFormation, whereas this fauna shows close similaritiesto that from the middle Rhuddanian Wulipo Bed atGaojiang, Meitan County. Wang et al. (2014) thus con-cluded that these tabulates represented a survival fauna

following the Hirnantian glaciation and mass extinc-tion. This conclusion is strongly reinforced by the factthat Propora and Paleofavosites also occur in the suc-ceeding middle Rhuddanian “Lungmachi Formation”at the Xiangshuyuan section (Ni et al. 2015). Further-more, rugose corals in this interval are small-sizedforms exhibiting thin septa (Wang 2014) that differconsiderably from the cool water rugose coral fauna of the Kuanyinchiao Formation, which is dominatedby diverse streptelasmatids that are characterized bycomparatively large coralla and strongly dilated septa(He et al. 2007).

Wang and Aldridge (2010) documented Ozarkodinaaff. hassi, the only conodont species to occur in Inter-val 4b at Xiangshuyuan. More recent work (Wang2013) has confirmed the presence of this species in thebasal part of the Xiangshuyuan Formation (upperRhuddanian), indicating its Silurian aspect. Interest-ingly, no reliably dated conodonts have been reportedfrom the Kuanyinchiao Formation across its vast dis-tribution on the Yangtze Platform. However, Amor-phognathus ordovicicus was confirmed from slightlyolder strata (Normalograptus extraordinarius grapto-lite Biozone) in the Wufeng Formation in South China(Chen et al. 2000, Chen et al. 2006). It should be notedthat Ozarkodina hassi itself seems to be of no signifi-cant biostratigraphic value, since it ranges from Hir-


Fig. 3. Stratigraphic corre-lation of the Ordovician–Sil-urian boundary successionbetween Tunping (a) andother localities to the south(b) in the Shiqian area, north-eastern Guizhou. Note thatnumbers in parentheses indi-cate lithostratigraphic divi-sions used in this study.

eschweizerbart_xxx


Fig. 4. Representative shelly macrofossils of the Ordovician–Silurian boundary in the Shiqian area. (a) and (b) Transverseand longitudinal sections of Paleofavosites schmidti from Interval 4b at Tunping; (c) Transverse section of Halysites sp. fromInterval 4b at Laichao; (d) and (e) Longitudinal and transverse sections of Propora thebesensis from Interval 4b at Laichao;(f) and (g) Longitudinal and transverse sections of Eurogrewingkia? sp. from Interval 4b at Xiangshuyuan; (h) and (i) Trans-verse and longitudinal sections of Meitanolasma polytabulatum (He, 1986) from Interval 3 at Tunping; (j) and (k) Dorsaland ventral valves of Cathaysiorthis? sp. from Interval 3 at Tunping.

eschweizerbart_xxx

nantian to late Llandovery (Wang and Aldridge 2010,Bergström 2011, Wang 2013).

In summary, fossils from Interval 4b in the Shiqianarea display low diversity and strong Silurian affini-ties, in contrast to the early–middle Hirnantian shellyfauna. This suggests that fossils from Interval 4b rep-resent a shelly fauna developed after the Hirnantianglacial stage. This interpretation is also in good agree-ment with the sedimentological evidence which indi-cates rocks from this interval represent warm-watermarine carbonates (Li et al. 2005).

Considering all the points above and also the factthat graptolites of the Akidograptus ascensus biozoneare found in immediately overlying strata, we suggestthat Interval 4b is probably of late Hirnantian age,though the possibility of an earliest Rhuddanian agecannot be completely excluded.

3.2 Age assignment of strata below Interval 4b

These rocks are generally considered as correspondingto the Kuanyinchiao Formation based on faunal evi-dence (Hu et al. 1983, Wang et al. 2014). However,

reconsideration of such evidence suggests these strataprobably lie stratigraphically much higher and repre-sent postglacial sediments, as discussed below.

Rugose corals from the intervals 2 and 3 consist ofonly one species, Meitanolasma polytabulatum, oc -curring in extremely high abundance (Wang 2014).Though this genus is also present in the early–middleHirnantian coral fauna, rugosans from the Shiqian areashow more similarities to those from the middle Rhud-danian Wulipo Bed, which yields the same genus andalso has similar low diversity. Brachiopods previouslyidentified as “Hirnantia” sp. (Hu et al. 1983), fromrocks assigned to Interval 3, are questionably reas-signed to Cathaysiorthis (Rong et al. 2008, 2013) andprobably belong to the Cathaysiorthis Fauna. The lat-ter fauna, dated as late Hirnantian-earliest Rhuddan-ian, has been regarded as a survival fauna associatedwith the waning of the Hirnantian glaciation (Rong etal. 2008, 2013). Additional support is provided by thefact that rocks from Interval 4a are rich in peloids andoncoids (Fig. 2f), typically indicative of warm waterdeposition.

Similar to the shelly fauna present in rocks of Inter-val 4b, fauna from Intervals 2, 3, and 4a are also likely


Fig. 5. Comparison of various interpretations of the stratigraphy of the Ordovician–Silurian boundary strata in Shiqianarea, northeastern Guizhou.

eschweizerbart_xxx

to represent postglacial warm-water shelly fauna. Fur-thermore, in view of their stratigraphic relationshipunderlying Interval 4b, we interpret all these intervalsto be of late Hirnantian age.

3.3 Discussion

The age determination for boundary carbonates in theShiqian area implies a stratigraphic gap between rocksof middle Katian and late Hirnantian age, which is ingood agreement with the widely accepted Hirnantianglaciation scenario (e. g., Brenchley et al. 2006, Harperet al. 2014) (Fig. 6). In this model, there was a signifi-cant sea-level drop during the early–middle Hirnant-ian, producing a widespread depositional hiatus. Theprevious early–middle Hirnantian age assignment ap-plied to these rocks makes it extremely difficult to ex-

plain how warm water carbonate sediments could bedeposited in a near-shore setting corresponding to theregression associated with the glacial maximum, andtherefore that age determination is rejected in favourof our conclusion that these carbonate rocks are post-glacial and younger, most likely latest Hirnantian.

4. Shiqian Formation (new lithostratigraphic unit)and its implications

The carbonate rocks spanning the Ordovician–Siluri-an boundary on the Yangtze platform of South Chinaare sporadically distributed in a near-shore area alongthe Qianzhong Oldland (Rong et al. 2011). To date,


Fig. 6. Palaeogeographical change of the Shiqian area through the Ordovician–Silurian transition and its correlation withHirnantian glaciation and associated sea-level change. (a) Pre-Hirnantian carbonate sedimentation; (b) Exposure spanningthe late Katian to the middle Hirnantian interval; (c) Late Hirnantian carbonate sedimentation associated with sea-level rise;(d) Middle Rhuddanian siliciclastic sedimentation after possible hiatus; (e) Generalized diagram showing the Hirnantianglaciation and its associated sea-level change, modified from Brenchley et al. (2006).

eschweizerbart_xxx

these rocks have generally been recognized as early–middle Hirnantian Kuanyinchiao Formation, or elseassigned to the middle Rhuddanian Wulipo Bed (Rongand Zhan 2004).

However, the Ordovician–Silurian boundary stratathat are restricted to the Shiqian and Sinan areas differconsiderably from the Kuanyinchiao Formation whichis widely distributed in the northern part of GuizhouProvince. The main lithology of what is now recog-nized as the Shiqian Formation is a grey bioclasticlimestone, which is quite distinct from the typical darkgrey micritic limestone of the Kuanyinchiao Forma-tion (Zhan et al. 2010). Shelly fauna from the bio -clastic limestone is dominated by tabulate corals (see section 2), contrasting with that of the KuanyinchiaoFormation, which is characterized by the developmentof Hirnantia brachiopod fauna and streptelasmatid rugosans, and the absence of tabulate corals and con-odonts. The Ordovician–Silurian boundary strata inthe Shiqian area are of late Hirnantian age and repre-sent post-glacial warm water carbonate sediments, incontrast to the Kuanyinchiao Formation consisting ofsediments deposited during the climax of the glacialevent.

Ordovician–Silurian boundary strata in the Shiqianarea also differ greatly in many respects from the Wu -lipo Bed in the Meitan area, though both are interpret-ed as postglacial warm-water carbonates. The WulipoBed, of middle Rhuddanian age, typically consists ofyellowish brown calcareous limestone and greyishgreen mudstone, and is mainly distributed in MeitanCounty, northern Guizhou (Rong and Zhan 2004).

All these striking differences require introduction ofa new lithostratigraphic unit, the Shiqian Formation,which is formally proposed herein (see Appendix).

The recognition of late Hirnantian carbonates con-taining shelly fossils completes the carbonate sequen -ce of the Ordovician–Silurian boundary in the Hir-nantian GSSP area of South China (Fig. 7). This con-tributes to the establishment of carbon isotope chemo -stratigraphy through the Ordovician–Silurian transi-tion in the region (see reviews in Fan et al. 2009, Mun-necke et al. 2011), and also necessitates reconsidera-tion of the patterns of faunal turnover of various shellyfossil groups in South China. Further research on theseideas will enhance correlation between the GSSP areaand other carbonate-dominated regions lacking grap-tolites.


Fig. 7. Correlation of carbonate rocks across the Ordovician–Silurian boundary (in grey colour) on the Yangtze Platformof South China.

eschweizerbart_xxx

5. Conclusions

The principal results of this study are summarized asfollows:

(1) At Tunping of Shiqian, where the stratigraphicallymore complete Ordovician–Silurian boundary sequence is better exposed than elsewhere in theregion, Interval 4 can be subdivided into two litho-logically distinct layers, with Interval 4a overlainby Interval 4b. Only Interval 4b strata can be correlated with limestone (commonly about 1 mthick) at other localities to the south.

(2) The boundary beds are most likely of late Hirnant-ian age (possibly ranging to the earliest Rhuddan-ian), rather than early–middle Hirnantian (andtherefore equated to the Kuanyinchiao Formation)as previously thought. Considering their uniquelithological components, fossils, geographic dis-tribution and age, a new lithostratigraphic unit, theShiqian Formation, is introduced herein.

(3) The new unit, together with the previously knownearly–middle Hirnantian Kuanyinchiao Forma-tion and middle Rhuddanian Wulipo Bed, com-prises a complete carbonate sequence across theOrdovician–Silurian boundary on the YangtzePlatform of South China, enabling precise correla-tion throughout the Hirnantian GSSP region.

Acknowledgements. We thank Wang Yi, Tang Peng,Liang Yan and Luan Xiaocong for their help in the field. RongJiayu and Wang Yi provided constructive comments on anearlier version of the manuscript. We also thank three anony-mous reviewers for their helpful suggestions which improvedthe final paper. Financial support for this study came from theNational Natural Science Foundation of China (41221001,41290260 and 41472006) and the State Key Laboratory ofPalaeobiology and Stratigraphy. Ian Percival publishes withpermission of the Director of the Geological Survey of NewSouth Wales. This paper is a contribution to the IGCP Project591 – The Early to Middle Paleozoic Revolution.

References

Bergström, S. M., Calner, M., Lehnert, O., Noor, A., 2011. Anew upper Middle Ordovician–Lower Silurian drillcorestandard succession from Borenshult in Östergötland,southern Sweden: 1. Stratigraphical review with regionalcomparisons. GFF 133, 149–171.

Bergström, S. M., Kleffner, M., Schmitz, B., 2012. Late Or-dovician–Early Silurian δ13C chemostratigraphy in theUpper Mississippi Valley: implications for chronostrati -

graphy and depositional interpretations. Earth and Envi-ronmental Science Transactions of the Royal Society ofEdinburgh 102, 159–178.

Brenchley, P. J., Marshall, J. D., Harper, D. A. T., Buttler,C. J., Underwood, C. J., 2006. A late Ordovician (Hirnant-ian) karstic surface in a submarine channel, recordingglacio-eustatic sea-level changes: Meifod, central Wales.Geological Journal 41, 1–22.

Chen, X., Rong, J. Y., Fan, J. X., Zhan, R. B., Mitchell, C. E., Harper, D. A. T., Melchin, M. J., Peng, P. A., Fin -ney, S. C., Wang, X. F., 2006. The Global Boundary Stra-totype Section and Point (GSSP) for the base of the Hir-nantian Stage (the uppermost of the Ordovician System).Episodes 29, 183–196.

Chen, X., Rong, J. Y., Mitchell, C. E., Harper, D. A. T., Fan,J. X., Zhan, R. B., Zhang, Y. D., Li, R. Y., Wang, Y., 2000.Late Ordovician to earliest Silurian graptolite and bra-chiopod biozonation from the Yangtze region, South Chi-na, with a global correlation. Geological Magazine 137,623–650.

Delabroye, A., Vecoli, M., 2010. The end-Ordovician glacia-tion and the Hirnantian Stage: A global review and ques-tions about Late Ordovician event stratigraphy. Earth-Science Reviews 98, 269–282.

Fan, J. X., Peng, P. A., Melchin, M. J., 2009. Carbon isotopesand event stratigraphy near the Ordovician–Silurianboundary, Yichang, South China. Palaeogeography, Pa -laeo climatology, Palaeoecology 276, 160–169.

Ge, Z. Z., Rong, J. Y., Yang, X. C., Liu, G. W., Ni, Y. N.,Dong, D. Y., Wu, H. J., 1979. Silurian system of South-west China. In: Nanjing Institute of Geology and Pa lae -ontology (Ed.), The carbonate biostratigraphy of South-west China. Science Publishing House, Beijing, p. 155–220 (in Chinese).

Harper, D. A., Hammarlund, E. U., Rasmussen, C. M., 2014.End Ordovician extinctions: A coincidence of causes.Gondwana Research 25, 1294–1307.

He, X. Y., 1986. New material of rugose corals of the LateOrdovician Guanyinqiao Bed in Bijie. Professional Pa-pers of Stratigraphy and Palaeontology 14, 29–47 (inChinese with English abstract).

He, X. Y., Chen, J. Q., 2003. New information on the LateOrdovician and Early Silurian rugose corals in northernGuizhou Province. Acta Palaeontologica Sinica 42, 174–185 (in Chinese with English abstract).

He, X. Y., Chen, J. Q., Xiao, J. Y., 2007. Combination features,paleobiogeographic affinity and mass extinction of the lat-est Ordovician (Hirnantian) rugosan fauna from northernGuizhou, China. Acta Geologica Sinica 81, 23–41.

Hu, Z. X., Gong, L. Z., Yang, S. W., Wang, H. D., 1983. Or-dovician–Silurian boundary in Shiqian, Guizhou. Journalof Stratigraphy 7, 140–142 (in Chinese).

Li, Y., 2004. Late Ordovician to Early Silurian Reef Evolu-tion in South China. In: Rong, J. Y., Fang, Z. J. (Eds.),Mass extinction and recovery-evidences from the Palaeo-zoic and Triassic of South China. University of Scienceand Technology of China Press, Hefei, p. 187–222 (inChinese with English abstract).


eschweizerbart_xxx

Li, Y., Matsumoto, R., Kershaw, S., 2005. Sedimentary andbiotic evidence of a warm-water enclave in the cooleroceans of the latest Ordovician glacial phase, YangtzePlatform, South China block. Island Arc 14, 623–635.

Munnecke, A., Zhang, Y. D., Liu, X., Cheng, J. F., 2011. Stable carbon isotope stratigraphy in the Ordovician ofSouth China. Palaeogeography, Palaeoclimatology, Pa -laeoecology 307, 17–43.

Ni, C., Deng, X., Li, Y., 2015. Biodiversity of the “Lung-machi Formation” limestones at the Xiangshuyuan sec-tion, Shiqian, NE Guizhou. Acta MicropalaeontologicaSinica 32, 96–104 (in Chinese with English abstract).

Rong, J. Y., Chen, X., Wang, Y., Zhan, R. B., Liu, J. B.,Huang, B., Tang, P., Wu, R. C., Wang, G. X., 2011. North-ward expansion of Central Guizhou Oldland through the Ordovician and Silurian transition: Evidence and im-plications. Science in China Series D Earth Sciences 41,1407–1415 (in Chinese).

Rong, J. Y., Chen, X., Zhan, R. B., Fan, J. X., Wang, Y.,Zhang, Y. D., Li, Y., Huang, B., Wu, R. C., Wang, G. X.,Liu, J. B., 2010. New observation on Ordovician–Siluri-an boundary strata of Southern Tongzi Country, northernGuizhou, Southwest China. Journal of Stratigraphy 34,337–348 (in Chinese with English abstract).

Rong, J. Y., Huang, B., Zhan, R. B., Harper, D. A. T., 2008.The earliest Silurian Cathaysiorthis Fauna (brachiopods)of East China and its evolutionary significance. ActaPalaeontologica Sinica 47, 141–167 (in Chinese withEnglish abstract).

Rong, J. Y., Huang, B., Zhan, R. B., Harper, D. A. T., 2013.Latest Ordovician and earliest Silurian brachiopods suc-ceeding the Hirnantia Fauna in Southeast China. SpecialPapers in Palaeontology 90, 1–142.

Rong, J. Y., Zhan, R. B., 2004. Survival and recovery of bra-chiopods in Early Silurian of South China. In: Rong, J. Y.,

Fang, Z. J. (Eds.), Mass extinction and recovery – evi-dences from the Palaeozoic and Triassic of South China.University of Science and Technology of China Press,Hefei, p. 97–126 (in Chinese with English abstract).

Wang, C. Y., 2013. Silurian conodonts in China. Universityof Science and Technology of China Press, Hefei, 230 p.(in Chinese with English abstract).

Wang, C. Y., Aldridge, R. J., 2010. Silurian conodonts fromthe Yangtze Platform, South China. Special papers inPalaeontology 83, 1–136.

Wang, G. X., 2014. Coral faunas across the Ordovician–Sil-urian transition of South China: implications on paleobio-geography and macroevolution, Ph. D. Thesis, Universityof Chinese Academy of Sciences, Beijing, China, 179 p.

Wang, G. X., Zhan, R. B., 2014. Preliminary report of a lateHirnantian shelly fauna in Shiqian, northeastern Guizhou,southwest China. In: Bauert, H., Hints, O., Meidla, T.,Männik, P. (Eds.), 4th Annual Meeting of IGCP 591, Estonia, 10–19 June 2014. Abstracts and Field Guide.University of Tartu, Tartu, p. 100.

Wang, G. X., Zhan, R. B., Deng, Z. Q., Yu, C. M., 2014. Latest Ordovician and earliest Silurian tabulate corals ofSouth China. GFF 136, 290–293.

Zhan, R., Jin, J., 2007. Ordovician–Early Silurian (Llan-dovery) Stratigraphy and Palaeontology of the UpperYangtze Platform, South China. Science Press, Beijing,169 p.

Zhan, R. B., Liu, J. B., Percival, I. G., Jin, J. S., Li, G. P.,2010. Biodiversification of Late Ordovician Hirnantiafauna on the Upper Yangtze Platform, South China. Sci-ence China-Earth Sciences 53, 1800–1810.

Manuscript received: December 18, 2014; rev. version ac-cepted: April 17, 2015.


eschweizerbart_xxx

Appendix

Shiqian Formation (nov.)

Derivation of name: from Shiqian County, the maindistribution area of this formation (Fig. 1).

Synonymy: the formation includes rocks previouslydesignated as the ʻKuanyinchiao Bedʼ, ʻKuanyinchiaoFormationʼ, and the ʻunnamed limestoneʼ in the area.

Constituent units: no formal members are proposed,but the formation contains several informal strati-graphic intervals, including Intervals 2, 3, 4a, 4b in as-cending order.

Distribution: the formation mainly occurs in Shiqianarea, but has also been reported from Wenjiadian, SinanCounty, about 20 km northwest of Shiqian county town.Another possible locality is Longkou-Kuaizi shan, Bai -sha Town, about 19 km west of Shiqian county town.

Type area: designated as Tunping (GPS: 27° 35�10.1� N, 108° 13� 17.9� E), about 8.3 km north of Shi -qian county town, where the stratigraphically more

complete Ordovician–Silurian sequence (i. e., Inter-vals 2, 3, 4a, 4b) is well exposed (Fig. 4).

Boundary relationships: the formation disconform -ably overlies the Linhsiang Formation, and is overlaindisconformably by the “Lungmachi Formation”.

Thickness: 2.3–2.6 m thick in the type area, but thinsto approximately 1 m at other localities, where only Interval 4b occurs.

Lithological variation: grey argillaceous limestone atthe base, overlain by greyish yellow calcareous mud-stone (both with numerous rugose corals), succeededin the upper part by unfossiliferous grey intraclasticlimestone, overlain by grey bioclastic limestone withabundant fauna.

Age: late Hirnantian (Late Ordovician), possibly ex-tending to the earliest Rhuddanian (early Llandovery,Silurian).


eschweizerbart_xxx

Documents

Wang et al Newsletters on Stratigraphy 48(3) 241-