(Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences, Nanjing 2 10008)

R. neves

(Palynology Research Center, University of Sheffield, UK, Sheffield S 13JD)

In this paper, microspore groups were found and studied for the first time near the sub-stratigraphic section of the international Devonian-Carboniferous boundary in Guilin, mainly at the end of Late Devonian in Gu Ping section, and two spore fossil zones, Pmr and Pml, were established. They are two spore belts at the end of late Devonian, which can be widely compared with Belarus, Poland, western Europe and central Hunan. The paper also discusses four stages of the evolution of the late Late Devonian microfauna flora in the above areas: ① Retispora lepidophyta is the main stage; (2) the existence stage of Chlorella and Echinococcus; ③ V.pusillites as the main stage; (4) The reproductive stage of LEPIDOPTERA insects. Pmr and Pml in Guilin area correspond to the above-mentioned stages ③ and ④ respectively. The paper also discusses the shortcomings of taking the disappearance of phytoplankton and needle algae as the Devonian-Carboniferous boundary.

Late Devonian; Microspores; Guilin, Guangxi

1 Introduction

Nanbiancun section in Guilin, Guangxi is a sub-stratigraphic section of the international Devonian-Carboniferous boundary (Figure 1). Because the profile is located in a set of slope facies in the front of carbonate platform, there are abundant biological fossils, and a corresponding fossil assemblage zone has been established here, including 8 conodonts, brachiopods, trilobites and ostracods from late Devonian to early Carboniferous, but no microspores have been found. There is a layer of 4mm thick black shale (the 49th layer) at 74.3cm below the D/C boundary of the profile, which was once considered to be equivalent to the Hangenberg shale in Germany and the Changshun shale in Guizhou. After many efforts (including previous work and the work of the author), no valuable microspores were obtained in this extremely thin black shale (Nanbiancun section and Toutoucun section). However, near Xinjian, 3km northwest of Guping, that is, about 10km away from Guilin, platform-valley facies (depression) strata are developed. Very rich and well-preserved late Devonian microspores were found in gray-black argillaceous shale and silty shale, which can be roughly divided into two assemblage zones. They can be widely compared with the late Devonian microspores in western Europe, Poland and the former Soviet Union. The discovery of this microspore undoubtedly makes up for the lack of microspore research on the Devonian-Carboniferous boundary in Guilin, and also makes new contributions to improving the level of paleontology research near the sub-layer profile.

Figure 1 Location Diagram of Gu Ping Section

A- limited platform facies; B- open platform to marginal platform facies; C- platform foreland slope facies; D- concave phase; Lithofacies of continental dike in e depression

Microspore biostratigraphy

2. 1 microspore assemblage at the top of Devonian in Gu Ping section, Guilin.

Microspore samples are mainly collected from the outcrop of the first member of Luzhai Formation above siliceous rocks (Liujiang Formation), and the lithology is mainly gray, gray-black interbedded sand, mud and shale. * * * Collected 15 samples, and after analysis, 8 samples contained abundant and well-preserved Late Devonian terminal microspore assemblages. They are described as follows:

Significant microspores (bottom-to-top sample number GP-2-GP-8) were obtained in the stratum where samples were collected, which was tentatively named as Pmr combination. At its bottom (GP-2), there are mainly Chrysophyta, Verruca and Oncospora with chronological significance. Their appearance undoubtedly indicates that this assemblage is the top microspore assemblage of the Late Devonian. However, it is the most developed in the class Cinnabaris, such as dense spore class. A, D.sp.B, and Acyclospora, which is similar to the category of cingulate, but in fact it is not cingulate and clustered. Halo-odorous oxides account for the majority. The molecules related to the microspore also include rugospora sp. Microcirculation is a special phenomenon. Pholiota sp. , Vallatisporites sp. Camptotriletes cf. Prionatus, Knoxisporites cf. Literatus, Tumulispora Monstrosa, Gorgonispora sp. Reticulata. Cladosporium sp. Christian policy association. Strange flowers and willows, etc. Further up, Vallatisporites puilites-tumulispora malevkensis, T. Robus-tospinosus sp.11month, an exotic HYMENOPTERA insect (sample GP-3-GP-8). Other microspores with the above-mentioned representative molecules * * * are: Tumulispora monstrosa, T. Varverrucata, Apiciculturetusipolites Hu Na-Nens, Grandisporasp. A, g. See Cornus officinalis, Acanthopanax. Densitosporium spitsbergen Pleistosporium sp. , Alternaria compressa, Alternaria sp., Alternaria sp., Alternaria sp., Acacia sp., Agaricus sp. ，Petrotriletes sp .，Convolutispora permixta，C.major，Pustulatisporites cf.dolbii，Cymbosporites cf.magnificus，Auroraspora macra，A.cf.corporiga， Planis-Porites sp. Rugospora cf. Corporata, R.sp, Camptotriletes paprothii, Latosporites sp. Microsporum. , Bascaudaspora sp., Echinococcus microcarpa, Acupora tricornis, K.sp, Echinococcus microcarpa, Echinococcus microcarpa, Coccidium vulgaris, Acupora radiata. Kraeusselispolities cf. Hibernaicus, Crassispora Catena, Bacillus sp .Velamisporites See Caperatus et al.

It is worth noting that in the sample GP-9, there are also the top microspore-producing layer, and there are also broken molecules of the variety of micromonospora. Now it is temporarily named Pml subband, because the proportion of micromonospora is 2% ~ 3%. This phenomenon can be compared with other parts of the world, especially Belarus (discussed below).

Table 1 Comparison of Microspores with Other Animal Fossils in Gu Ping Section, Guilin

2.2 Comparison with other animal fossils in the same period

There are some other fossils on this section, such as ammonites, ostracods and odontoids. Among them, the original 60-layer Luzhai Formation in Gu Ping profile (Guilin1:50,000 regional geological survey report, 1988) is rich in ostracods, R. (R.) Costa, r .(r .)stri Tula and Maternell La Hemisphaerica. They are the main molecules in the hemispherical-double spherical zone at the top of the Rheinland Famen stage in Germany, and are also found in Luofu, Nandan, Guangxi. Chrysanthemum stone Tornoceras? Species are only found in the Middle and Upper Devonian.

Two combinations developed in Guilin. Minor-Vallatisporites Puilites-Tumulispora Malevkensis and V. Puilites-T. Malevkensis-T. Robustostrinosus SP. Their characteristics can be similar to those of Hua Mu, Dushan, Central Hunan and Pripyati Depression in South China. For example, Yang Yuncheng, such as V. Puillites and V. Vallatus, and some other spore genera and species are very poor. The number of LEPIDOPTERA insects is very small, and the number of delicate individuals is greatly reduced. However, the Tu-mulispora of some species has increased sharply, so this zone is called the V. Puillites-T. (PM) zone. This is the most important fossil belt in Russia after the LL belt, LE belt and PLE belt in the Late Devonian. The conodonts born with this band are Siphonodella Praesulcata, Pseudopolinatus fusiformis (Avchimovitch, v.i.et al). It is the standard molecule of upper Devonian microspore zone LN(R.lepidophyta-V.nitidus) in western Europe. V.nitidus is the topmost P-band molecule (V.pusillites) in the Late Devonian, and it is also compared with the LN zone in Western Europe [29]. We know that the definition of LN band is based on the first appearance of V.nitidus and the gradual disappearance of R.lepidophyta. The appearance of microspores in Gu Ping section of Guilin reflects this trend, which has always been characterized by the prosperity of v.puillites-t.malevkensis-t.robustostrinosus sp. Nova Exophytic HYMENOPTERA insects, but broken LEPIDOPTERA insects appear at the top. There is a similar phenomenon in the Beqiaogur section of the Mugodzar Mountains in the former Soviet Union. R. Lepidopyta was found in the top ML (T.malevkensis-R. Lepidopyta) belt of the Late Devonian, while T.malevkensis and R.lepidophytavar.minor co-produced in the PM belt of Belarus [28]. In addition, the Mugoazhary area is equivalent to the rare R.lepidophyta var.tenera in the 2b section. As already introduced [24], there is a similar situation in central Hunan. Of the three sub-bands of the PL band (V. Puillites-R. Lepi-Dophyta), the lower sub-band only shows the output of R.lepidophyta, while the central Asian band * * * also has the same output, and the upper sub-band is dominant, but R. Lepidita has not been seen yet. At the top of the upper sub-zone, that is, at the top of the Meng Gong 'ao Formation, there was no previously discovered chlorophyta. Fang Xiao Si [32] claimed to have discovered chlorophyta and established a new formation-Tian Xin Formation. If it is true, it has a very similar evolution and development process with Guilin.

4 Devonian-Carboniferous microspore biostratigraphy

4. 1 Four stages of microspore evolution at the end of Late Devonian

To sum up, Guilin has a relatively consistent evolutionary relationship with the late Devonian microspores in Poland, the former Soviet Union, central Hunan and Guizhou, China. The characteristics of late Devonian microspore groups in these areas can be summarized into four stages. In the 1 stage, the lone vegetable is dominant or only produces lone vegetable, such as the lower sub-region of PL belt in central Hunan, L belt in eastern Russia platform [29] and Ra belt in western Pomerania [33], and the lone vegetable can reach14%; The second stage is marked by the birth of R.lepidophyta and V. Puillites * * *, such as the Central Asian belt of PL belt in central Hunan, the PLE sub-belt of P belt in Russia mentioned earlier, and the LL and LE belts in western Europe should be equivalent to this stage; The third stage is dominated by chrysotile, such as the upper sub-zone of PL belt in central Hunan, the PM sub-zone of Russian P belt and the Pmr combination of Guilin. Most LN belts in western Europe also belong to this stage, and Poland seems to have missed this stage. The fourth stage, that is, the re-eclosion stage, is generally represented by the varieties and varieties of Lepidium. For example, the Tian Xin Formation in central Hunan is said to have produced Lepidium. Lepidophyta var. Tenera was produced in ML belt of 2b section of Berchogur section in Mugodzhar mountain area of former Soviet Union, and lepidophyta var.minor was produced in Pml combination in Guilin area. The combination of Pmr and Pml in Guilin area corresponds to the above-mentioned stage 3 and stage 4 respectively. Fig. 2 reflects the evolution of microspores at the end of late Devonian.

4.2 Puzzlement and lack of Devonian-Carboniferous microspore boundary

In practice, it is often confusing to regard the scale algae and needle algae as the standard of Devonian-Carboniferous microspore boundary. Near the conodont boundary, the proportion of these two microspores is quite small. This makes it difficult to tell whether it is missing or disappearing. In other words, when R.lepidophyta is less than 1% [30], the molecule is often very rare and difficult to find, so it may be concluded that the molecule disappears. South China has such an example. The Meng Gong 'ao Formation in Malanbian section of Xinshao county in central Hunan belongs to Early Carboniferous, but no Lepidoptera fossils have been found at the top of Upper Devonian. In fact, Yang Yuncheng [24] and Fang Xiao Si [32] found LEPIDOPTERA fossils in Meng Gong 'ao Formation and even at the top.

In addition, according to the concrete practice of modern punctuated equilibrium theory on speciation and stratigraphic boundary division in different periods, the boundary between many periods depends on the first appearance of some new animal and plant species. From this point of view, the Devonian-Carboniferous microspore boundary is based on the disappearance of R.lepidophyta and V.pusillites, which obviously has its inherent shortcomings.

Fig. 2 Four stages of microspore evolution at the end of Late Devonian.

5 conclusion

The sporopollen data near the Devonian-Carboniferous boundary subtype profile in Guilin were obtained for the first time, and two microspore assemblages were established at the end of late Devonian. These combinations can be compared with those in Hunan, Guizhou, the lower reaches of the Yangtze River, Belarus, Poland and the Rhine. It is found that the microspore evolution in the late Devonian strata in the above areas has gone through four stages. Namely: ① the dominant stage of LEPIDOPTERA; ② The growth stages of Dryopteris Dryopteris and Dryopteris Needles * * *; ③ V.pusillites as the main stage; ④ In the re-eclosion stage, the Pmr combination and Pml combination in Guilin correspond to the above stage ③ and ④ respectively. According to the above evolutionary stages, it is not difficult to distinguish whether these standard fossils are missing or disappearing in practice, especially when the proportion of R.lepidophyta is relatively small. At the same time, it is pointed out that according to R.lepidophyta and V.pusillites, the disappearance of the traditional Devonian-Carboniferous sporopollen boundary has its inherent shortcomings.

Description of new fossil species

Tumulispoa staplin & jansonius genus 1964

Epinephelus robusta 1 1 month

Full-size nameplate Ⅰ-9 (page 68), sheet GP-4- 1

Description Triceratops, with rings and holes, triangular equatorial outline, round or conical top. The three rays are obvious and extend to the equator in a straight line or wave shape. The outer layer of the (outer wall) extends along the equator to form a prominent black ring with a thickness of 10μm, and gradually tapers at the distance of 2/3 from the equator. The outer layer and ring of the outer wall of the far pole face have thick spinous processes at the base, which are separated or connected at the base to form a rough crown (tumor) ridge. The thorn length is 6 ~10μ m, and the base diameter is 3 ~ 6μ m. The inner layer is usually not obvious.

Measure 32 ~ 65μ m (according to 5 fossils)

Compared with other species of Tumulispora, this new species has obvious and thick spines. The length of thorns is generally 6 ~ 10 micron, and they are usually connected at the base to form a rough crown (tumor) ridge.

Origin and horizon: South China, Guilin, top of Upper Devonian.

Thank you, John Utting, for carefully reading the full text and making valuable comments.

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Chart description

The specimens are deposited in Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences. They all occur in the second member of Luzhai Formation in Gu Ping section of Guilin. Unless otherwise specified, all photos are magnified 750 times.

1, 2— Reticularia lepidoides (Kedo)Playford, 1976

3-Cladosporium.

4, 7— Naumova)Playford, 1964

5、6—Vallatisporites pusillites(Kedo)Dolby & Neves， 1970

8-Knoxvomica.

9— Echinococcus crassipes, a new species

10— The genus Myxosporium.

1 1、 12—malevkensis(Kedo)Turnau， 1978

Paleontological geography history