Fig 1 - uploaded by V. N. Podkovyrov
Content may be subject to copyright.
Comparison of fossil chains of fungi: (a) Fractisporonites moniliformis (Clarke, 1965); (b) Arctacellularia ellipsoidea (Hermann, 1976, emend.); and (c) monoserial " microforams " (Elsik, 1969).
Source publication
Possible phylogenetic relationships between the organic-walled microfossils of the form genus Arctacellularia Hermann, 1976, representing chainlike aggregates of cells, and the filaments of the genus Glomovertella Reitlinger, 1948, which comprises variously coiled filaments, are discussed. The possible relationship of these microfossils
with differ...
Contexts in source publication
Context 1
... at the center. Narrow longitudinal cords can be observed along a chain of cells. In the description of the holotype of this species no mention was made of the fact (regarded then as merely coinci- dental) that a chain of cells was located in the vicinity of narrow straight and aseptate filaments slightly over- lapping one another (Pl. 8, fig. 1). More recently, this microbiota yielded specimens which show such a direct association of chainlike aggregates with filaments, which are usually looped in the form of an elongate skein (Pl. 8, figs. 4, 5, 11). Filaments twisted into a skein are located in close proximity and parallel to each other, slightly overlapping one another ...
Context 2
... morphology the chain of the cells of A. doliifor- mis resembles the chains of fungal spores of the Meso- zoic genus Fractisporonites (Clarke, 1965) (Figs. 1a, 1b) in the type of chainlike organization, shape, and dimen- sions of cells and in the presence of thickened intercel- lular walls and narrow cords arranged along the chains. This resemblance to the fossil remains of fungal nature suggests that it will be very promising to compare A. doliiformis with modern organisms, especially with ...
Context 3
... Paleontology provides an emended diagnosis of the genus Arctacellularia and the descrip- tion of the species A. ellipsoidea Hermann, 1976;A. kelleri Hermann et Jankauskas, 1989; and Glomov- ertella miroedikhia sp. nov. E x p l a n a t i o n o f P l a t e 8 Figs. 1-5, 7, 10-12, and 17. Arctacellularia ellipsoidea Hermann, 1979: (1) chain of cells is associated with the remains? of a sporiferous filament (hypha); (1) specimen no. 49/24-XI.72: (1a) general appearance, (1b, 1c) magnified fragments; (2, 17) frag- ments of isolated chains in which some cells divided into two cells: (2) specimen no. 49/8-XI.77; (17) ...
Context 4
... isolated chains with narrow longitudinal cords: (3) specimen no. 49/8-XI.77; (7) specimen no. 49/45-XI.72; (10) specimen no. 49/57-XI.72; (4, 5, 11, 12) chains of cells associated with filaments coiled in loop-shaped pattern: (4) specimen no. 49/59-XI.72, (5) specimen no. 49/22-XI.72, (11) specimen no. 49/22-XI.72, (12) specimen no. 49/3-XI.72. Figs. 6, 8, 14, and 16. Arctacellularia kelleri Jankauskas et Hermann, 1989: (6) specimen no. 49/25-XI.72; (8) specimen no. 49/46-XI.72; (14) specimen no. 49/3-XI.72; (16) specimen no. 49/7-XI.72. Figs. 9, 13, and 15. Glomovertella miroedikhia sp. nov.: (9) specimen no. 49/3-XI.72, (13) ...
Context 5
... coiled in loop-shaped pattern: (4) specimen no. 49/59-XI.72, (5) specimen no. 49/22-XI.72, (11) specimen no. 49/22-XI.72, (12) specimen no. 49/3-XI.72. Figs. 6, 8, 14, and 16. Arctacellularia kelleri Jankauskas et Hermann, 1989: (6) specimen no. 49/25-XI.72; (8) specimen no. 49/46-XI.72; (14) specimen no. 49/3-XI.72; (16) specimen no. 49/7-XI.72. Figs. 9, 13, and 15. Glomovertella miroedikhia sp. nov.: (9) specimen no. 49/3-XI.72, (13) ...
Context 6
... 8, figs. 1-5, 7, 10, 11; Plate 9, fig. 12 Arctacellularia ellipsoidea Hermann: Timofeev et al., 1976, p. 39, pl. 11, figs. 1, 2; Jankauskas, 1982, p. 117, pl. 35, figs. 4, 5, 9, 13; pl. 38, fig. 6, 11; pl. 48, figs. 9, 12; Xing et al., 1985, p. 63, pl. 7, fig. 13;Jankauskas et al. 1989, p. 136, pl. XXXVIII, figs. 1a, 1b, 6, 9, 14;pl. 13, fig. 9; Hofmann and Jackson, 1994, p. ...
Context 7
... 8, figs. 1-5, 7, 10, 11; Plate 9, fig. 12 Arctacellularia ellipsoidea Hermann: Timofeev et al., 1976, p. 39, pl. 11, figs. 1, 2; Jankauskas, 1982, p. 117, pl. 35, figs. 4, 5, 9, 13; pl. 38, fig. 6, 11; pl. 48, figs. 9, 12; Xing et al., 1985, p. 63, pl. 7, fig. 13;Jankauskas et al. 1989, p. 136, pl. XXXVIII, figs. 1a, 1b, 6, 9, 14;pl. 13, fig. 9; Hofmann and Jackson, 1994, p. 16, pl. 12, figs. ...
Context 8
... 8, figs. 1-5, 7, 10, 11; Plate 9, fig. 12 Arctacellularia ellipsoidea Hermann: Timofeev et al., 1976, p. 39, pl. 11, figs. 1, 2; Jankauskas, 1982, p. 117, pl. 35, figs. 4, 5, 9, 13; pl. 38, fig. 6, 11; pl. 48, figs. 9, 12; Xing et al., 1985, p. 63, pl. 7, fig. 13;Jankauskas et al. 1989, p. 136, pl. XXXVIII, figs. 1a, 1b, 6, 9, 14;pl. 13, fig. 9; Hofmann and Jackson, 1994, p. 16, pl. 12, figs. ...
Context 9
... the formation of chains (segmentation or fragmentation of sporiferous hyphae) and the aberration of growth observed in certain cells in chains suggest the polymor- phism characteristic of fungal organisms. Some of the cells in chains are quite rounded (Pl. 8, fig. 2, the low- ermost cell with a pair of cells formed above it). The chain in Pl. 8, fig. 17 shows the same pattern: the rounded cell (third from the bottom) with two pairs of separated cells. The process of cell division was also observed in the chains associated with hyphae (see Pl. 8, figs. 5, 11). These facts may suggest the possibility of further multiserial formation of fungal ...
Context 10
... Dzhezhinskaya Parma; Bushimay Supergroup, Zaire. M a t e r i a l. Five specimens of interconnected microfossils and numerous finds of isolated chains. Hermann et Jankauskas, 1989 Plate 8, figs. 6, 8, 14, and 16;Plate 9, figs. 13-16 Arctacellularia kelleri Hermann et Jankauskas: Jankauskas et al., 1989, p. 136 E x p l a n a t i o n o f P l a t e 9 Figs. 1-3, 5, 7, and 11. Glomovertella eniseica Hermann, 1989: concentric coiling of filaments: (1, 2) specimen no. 49/t-16.1.71; (3, 11) specimen no. 49/5-6.XII.73; (5) specimen no. 49/3-23.II.74; (7, 11) specimen no. 49/5-6.XII.73. Figs. 4 and 6. Glomovertella miroedikhia sp. nov.: (4) specimen no. 49/46-XI.72; (6) specimen no. 49/3-23.II.74. Figs. 8-10. ...
Context 11
... 9 Figs. 1-3, 5, 7, and 11. Glomovertella eniseica Hermann, 1989: concentric coiling of filaments: (1, 2) specimen no. 49/t-16.1.71; (3, 11) specimen no. 49/5-6.XII.73; (5) specimen no. 49/3-23.II.74; (7, 11) specimen no. 49/5-6.XII.73. Figs. 4 and 6. Glomovertella miroedikhia sp. nov.: (4) specimen no. 49/46-XI.72; (6) specimen no. 49/3-23.II.74. Figs. 8-10. Arctacellularia sp.: (8) specimen no. 49a/1, fragmentation of chains into single cells; (9, 10) budding of cells: (9) spec- imen no. 49/46-XI.72, (10) specimen no. 49/2-11.XII.73. Fig. 12. Arctacellularia ellipsoidea Hermann, 1976, chain with a markedly hypertrophied cell, specimen no. 49/57-XI.72. Figs. 13-16. Arctacellularia kelleri ...
Context 12
... (7, 11) specimen no. 49/5-6.XII.73. Figs. 4 and 6. Glomovertella miroedikhia sp. nov.: (4) specimen no. 49/46-XI.72; (6) specimen no. 49/3-23.II.74. Figs. 8-10. Arctacellularia sp.: (8) specimen no. 49a/1, fragmentation of chains into single cells; (9, 10) budding of cells: (9) spec- imen no. 49/46-XI.72, (10) specimen no. 49/2-11.XII.73. Fig. 12. Arctacellularia ellipsoidea Hermann, 1976, chain with a markedly hypertrophied cell, specimen no. 49/57-XI.72. Figs. 13-16. Arctacellularia kelleri Jankauskas et Hermann, 1989: (13) H o l o t y p e. IGGD, no. 49/6-76; Russia, north- western Siberia, Turukhansk Region, Miroedikha River, Miroedikha Formation, Upper Riphean. D e s c r i ...
Context 13
... (6) specimen no. 49/3-23.II.74. Figs. 8-10. Arctacellularia sp.: (8) specimen no. 49a/1, fragmentation of chains into single cells; (9, 10) budding of cells: (9) spec- imen no. 49/46-XI.72, (10) specimen no. 49/2-11.XII.73. Fig. 12. Arctacellularia ellipsoidea Hermann, 1976, chain with a markedly hypertrophied cell, specimen no. 49/57-XI.72. Figs. 13-16. Arctacellularia kelleri Jankauskas et Hermann, 1989: (13) H o l o t y p e. IGGD, no. 49/6-76; Russia, north- western Siberia, Turukhansk Region, Miroedikha River, Miroedikha Formation, Upper Riphean. D e s c r i p t i o n. The cells are single or arranged in pairs, smooth-walled, barrel-shaped and cylindrical. The lateral walls are ...
Context 14
... mature arthrospores that belong to representatives of the quite extensive group of asco- mycetes. At the terminal stage of development the shape of arthrospores changed from ellipsoidal and bar- rel-shaped to cylindrical. The development of single cells shows some degree of variability: they show the beginning of centripileous division (Pl. 8, fig. 16) and budding (Pl. 9, figs. 9, 10). R e m a r k s. Different deviations from the regular oval or cylindrical shapes of cells are due to different states of preservation of ...
Context 15
... to representatives of the quite extensive group of asco- mycetes. At the terminal stage of development the shape of arthrospores changed from ellipsoidal and bar- rel-shaped to cylindrical. The development of single cells shows some degree of variability: they show the beginning of centripileous division (Pl. 8, fig. 16) and budding (Pl. 9, figs. 9, 10). R e m a r k s. Different deviations from the regular oval or cylindrical shapes of cells are due to different states of preservation of ...
Citations
... cf. D. symmetricus Kalgutkar and Jansonius (2000) Dictyosporites tirumalacharii Kalgutkar and Jansonius (2000) Staphlosporonites irregularis Kalgutkar and Jansonius (2000) The tabular structure of Fractisporonites canalis possibly indicates the presence of a parasitic fungus (Kalgutkar and Jansonius, 2000) or closely resembles the external spore formation known as actinomycetes (Hermann and Podkovyrov, 2008). They can survive under extreme conditions (Trenozhnikova and Azizan, 2018) and are prominently found in soil, water bodies, and plant remains (Bhatti et al., 2017). ...
Fungal spores in Neogene organic-rich sediments from the Hongsa coalfield in northwestern Lao PDR were studied in detail. Fungal spores and the significance of palynological associations are employed for interpreting depositional environment and paleoclimate. The palynological assemblages, recovered from 34 samples, were rich and diversified, consisting mainly of pollen grains of vascular plants, spores of pteridophytes, and fungal spores. Of all 67 fungal taxa from 22 genera identified in this study, 21 are Amerosporae, 20 Phragmosporae, 18 Didymosporae, and 8 Dictyosporae. Although diversified, they yielded low to very low frequencies compared to total palynomorphs. Most palynological and fungal spores in this investigation indicate a Miocene age of the deposits. The presence of Dyadosporites, Brachysporisporites, Diporicellaesporites, Pluricellaesporites, and Dictyosporites of subtropical to warm temperate forests associated with a large number of pteridophytes and evergreen to deciduous vegetation can reinforce the hypothesis of terrestrial origin in a humid and warm climate. Variations in relative abundance and diversity of fungal spores in this study indicate paleoenvironmental fluctuations during deposition, which also conform to the climate interpreted from each palynological zone.
... They are comparable to colonial or filamentous forms of either prokaryotes such as modern cyanobacteria Microcrocis, Merismopedium, and Stigonema (Komárek and Anagnostidis, 2008;Komárek, 2013) or eukaryotes such as modern chlorophyte Chlorococcum, Coelastrum (Wehr et al., 2015). Arctacellularia tetragonala has been interpreted as putative chains of fungal spores (Hermann and Podkovyrov, 2008); however, diagnostic characteristics of fungi are needed to support this interpretation. ...
Organic-walled microfossils offer important information on the biospheric evolution in pre-Cryogenian and provide biostratigraphic implications for many Proterozoic fossiliferous sequences that are poorly age constrained for the lack of reliable radiometric date. Recently, macroscopic carbonaceous compression fossils have been reported for the first time from the Tonian Shiwangzhuang Formation of the Tumen Group in western Shandong, North China. However, organic-walled microfossils have never been discovered from this formation up till now. To improve our knowledge about Proterozoic biodiversity in North China, we conducted a micropaleontological survey on the argillaceous limestone samples of the Shiwangzhuang Formation, which also contain macroscopic carbonaceous compression fossils, from the Baishicun section in Anqiu, western Shandong, North China. Our investigation shows that the Shiwangzhuang microfossil assemblage is dominated by smooth-walled sphaeromorphic acritarchs and cyanobacterium-like filaments and relatively low abundance of other acritarchs, including 16 taxa, such as Polysphaeroides filliformis, Ostiana microcystis, Simia annulare, ?Jacutianema sp., Arctacellularia tetragonala, Pellicularia tenera, Polythrichoides lineatus, and Navifusa actinomorpha. The Shiwangzhuang organic-walled microfossil assemblage, although consisting of long-ranging and not age diagnostic taxa, is consistent with a Tonian age suggested by macroscopic carbonaceous compression fossils, including the Chuaria-Tawuia and Sinosabellidites-Protoarenicola-Pararenicola assemblages, revealed from the same fossiliferous horizon of the Shiwangzhuang Formation and by organic-walled microfossil assemblage, including the late Mesoproterozoic to Tonian index fossil Trachyhystrichosphaera aimika, from the underlying Tongjiazhuang Formation. However, it is also worth noting that a Cryogenian or Ediacaran age cannot be completely excluded based just on the Shiwangzhuang microfossils because of their limited biostratigraphic utility.
... There are reports of fossil fungal spores, conidia, sclerocia, fruit ing bodies, and vegetative hyphae found from the Upper Paleozoic to the Quaternary. There are a few paleomy cological records from the Precambrian (Schopf, 1968;Timofeev, 1971;Hermann, 1979;Burzin, 1993; Butter field, 2005; Hermann and Podkovyrov, 2006, 2008a, 2008bNagovitsyn, 2008). The actualistic method in studying fossil organisms allows some understanding of their relationship with closely related extant taxa while taking into account taphonomic effects on morphology and comparison of evidence from life cycles and life styles of ancient organisms. ...
... vesicles (Fig. 4e). The chains of Arctacellularia tetragonala are interpreted as exogenously produced spores of Ascomycetes (Hermann and Podkovyrov, 2008). But this interpretation is far from convincing and on the basis of its morphological similarity to Jacutianema its algal nature seems more plausible. ...
An assemblage of organic walled microfossils (OWM) of 17 taxa belonging to 10 genera is reported from the Neoproterozoic Owk Shale of the Kurnool Group, South India. The assemblage comprises sphaeromorphs, colonial aggregates, filamentous forms, spiral cylindrical filaments belonging to cyanobacteria, problematic acanthomorphic acritarchs, Netromorphic, Sphaeromorphic and Acantomorphic groups. The assemblage includes cyanobacteria: Siphonophycus kestron, S. robustum, S. typicum, S. solidum, Polytrichoides lineatus; Netromorphic acritarch: Arctacellularia tetragonala, Navifusa majensis, Jacutianema solubila; Sphaeromorphic acritarch: Ostiana microcystis, Synsphaeridium spp., Leiosphaeridia minutissima, L. tenuissima, L. crassa, L. jacutica, L. ternate; and Acanthomorphic acritarch: Cavaspina aff. C. acuminata and Variomargosphaeridium aff. V. litoschum. The age conundrum of Kurnool Group (Mesoproterozoic versus Neoproterozoic) is discussed. On the basis of the reported OWM assemblage the age of the Kurnool Group is established as Neoproterozoic.
... The vesicle wall of each is robust and dark, with, faintly granular texture on the surface (Fig. 13I). Individual cells in the Ruyang material are elongate and tetragonal in shape, 24-29 lm wide and 39-46 lm long (n = 6), but may be up to 60 lm long (Hermann and Podkovyrov, 2008). At the junction surface between individual cells, the wall is thickened. ...
... Chains documented from the Ruyang Group are fairly short (up to three connected segments), which is likely a preparation bias. Hermann and Podkovyrov (2008) have recorded the maximum length of Arctacellularia chains to 300 lm. (Yan and Zhu, 1992). ...
... Occurrence: Mesoproterozoic Bylot Supergroup, Baffin Island, Canada (Hofmann and Jackson, 1994); Tonian Bushimay Supergroup, Zaire (Maithy, 1975); Mesoproterozoic Bahraich Group, Ganga Basin, India ; Lower Vindhyan Group, India the Zilmerdak Formation and the Uk Formation, southern Urals, Russia (Jankauskas, 1982;Jankauskas et al., 1989); and the Early Tonian Miroedikha Formation, Siberia, Russia (Hermann and Podkovyrov, 2008). ...
Mesoproterozoic Era was an important time for initial diversification of eukaryotic clades and appearance of the earliest complex cell morphologies. Shales and siltstones of the Ruyang Group, Shanxi Province, North China Craton, record such diverse organic-walled microfossils, in addition to novel morphotypes. Recently, the depositional age of this succession has been constrained to 1744 ± 22 to 1411 ± 27 Ma via zircon U-Pb and Hf isotopic dating. This dating extended back the time of the first appearance of complex eukaryotic characters (e.g. processes, sculpture, layered wall structure) in the fossil record. We have conducted a biostratigraphic investigation of the samples throughout the fossiliferous Ruyang Group to provide an estimate of the relative early eukaryotic diversity in the Mesoproterozoic. Light- and scanning electron microscope observations have documented 26 species, including several that are reported for the first time, and some that were previously known only from younger, Neoproterozoic strata. Diversity was high in the upper Baicaoping Formation, declined in the middle and reached its peak in the upper Beidajian Formation. Novel morphologies among the unicellular Ruyang biota included a variety of processes, from tube-like extensions to hirsute spines, vesicles with velutinous outer membranes, as well as numerous specimens with internal bodies of varying sizes. We have also recorded the globally distributed Mesoproterozoic taxa Dictyosphaera and Tappania, and several morphotypes of Shuiyousphaeridium. Key characters displayed by the Ruyang biota are consistent with reproductive structures (especially cysts) like those among modern protists. These microfossils provided an additional evidence for the ongoing first radiation of Eukarya by at least 1400 Ma.
... -The same species was reported previously as G. eniseica(Yankauskas et al., 211 1989). In a recent publication(Hermann and Podkovyrov, 2008), the emended diagnosis212 allowed the establishment of the new species G. miroedikhia which differs from the former in 213 the parallel arrangement of filaments in the coils instead of a tangle of filaments. It is possible 214 that all spiraling filaments attributed to Glomovertella and Obruchevella are related as 215 suggested by Hofmann and Jackson (1994). ...
... Other species that could be eukaryotic or prokaryotic include relatively large single oval vesicles such as Navifusa actinomorpha Maithy, 1975 (Fig. 8J and K) and Navifusa majensis Pyatiletov, 1980 (Fig. 8L), large vesicles with smaller attached vesicles Coneosphaera sp. (Fig. 8M and N), vesicles forming multicellular chains Arctacellularia tetragonala Maithy, 1975 (Figs. 8O-R, 9A-J and 10) previously interpreted as putative fungi at different stages of their life cycle (Hermann and Podkovyrov, 2008). ...
A well preserved and diversified microfossil assemblage is reported from the Meso–Neoproterozoic Mbuji-Mayi Supergroup in the Kasai oriental Province, central part of Democratic Republic of Congo. A total of 49 taxa belonging to 27 genera were identified, including 11 species of unambiguous eukaryotes, 10 species of possible eukaryotes or prokaryotes and 28 species of probable bacteria. This assemblage is more diverse than previously reported but includes taxa reported in coeval worldwide assemblages. It is characterized by abundant sphaeromorphs, filamentous colonial aggregates and filamentous forms, as well as a relatively low diversity of acanthomorphs including the Late Mesoproterozoic and Early Neoproterozoic index fossil – Trachyhystrichosphaera aimika – reported for the first time in Central Africa. This species co-occurs with other taxa also reported for the first time in Africa: Trachyhystrichosphaera botula, Jacutianema solubila, cf. Tappania sp., Valeria elongata and numerous other taxa. Correlation with other geochronologically constrained successions that contain Trachyhystrichosphaera confirms T. aimika as promising index fossil to define the Late Mesoproterozoic–Early Neoproterozoic interval. The available biostratigraphic data enable suggest a minimum Tonian age for the Mbuji-Mayi Supergroup. This age is consistent with the published and new geochronological data. Comparison with worldwide Proterozoic assemblages permits to define microfossil assemblages useful for biostratigraphy. This study significantly improves our understanding of the diversity of the Late Mesoproterozoic–Early Neoproterozoic biosphere, and in particular the diversification of early eukaryotes, preserved in the Democratic Republic of Congo rock record and more broadly in Africa where micropaleontological investigations are sparse.
... The use of acritarchs for biostratigraphic subdivisions of Precambrian successions is much less straightforward and reliable than in Phanerozoic strata due to the relative dearth of detailed and stratigraphically constrained palynological investigations of Proterozoic successions especially in pre-Ediacaran strata, but also because many acritarch taxa of Proterozoic age appear -at present state of knowledge -to have had slower (morphological) evolutionary rates than their Palaeozoic counterparts (Samuelsson and Butterfield, 2001;Nagovitsin, 2009). However, the currently growing number of highly detailed studies on Meso-and Neoproterozoic organic-walled microfossil assemblages from well-dated successions (e.g., Prasad et al., 2005;Yin et al., 2005;Hermann and Podkovyrov, 2008;Schopf and Bottjer, 2009;Nagy et al., 2009), is undoubtedly showing increasing potential for achieving a sufficiently detailed acritarch biostratigraphy applicable in Precambrian stratigraphy (Sergeev, 2009). In fact, this has been already well demonstrated for the Ediacaran period (Grey, 2005;Willman et al., 2006). ...
Since several decades, geologists disagree about the lithostratigraphic subdivision of the Volta Basin sedimentary infilling. Correlations at the scale of the Volta Basin were up to now largely limited by the discontinuity of outcrops along the basin margin and by the scarcity of stratigraphic constraints within the sedimentary succession. Even if a subdivision of the Volta Basin infilling into three main groups (Bombouaka, Oti, and Obosum Groups) is now generally accepted, there is no agreement for lithostratigraphic subdivision at the formation scale. The Bombouaka Group, which represents first deposits of the Volta Basin sedimentary infilling, is particularly concerned.
... The use of acritarchs for biostratigraphic subdivisions of Precambrian successions is much less straightforward and reliable than in Phanerozoic strata due to the relative dearth of detailed and stratigraphically constrained palynological investigations of Proterozoic successions especially in pre-Ediacaran strata, but also because many acritarch taxa of Proterozoic age appear -at present state of knowledge -to have had slower (morphological) evolutionary rates than their Palaeozoic counterparts (Samuelsson and Butterfield, 2001;Nagovitsin, 2009). However, the currently growing number of highly detailed studies on Meso-and Neoproterozoic organic-walled microfossil assemblages from well-dated successions (e.g., Prasad et al., 2005;Yin et al., 2005;Hermann and Podkovyrov, 2008;Schopf and Bottjer, 2009;Nagy et al., 2009), is undoubtedly showing increasing potential for achieving a sufficiently detailed acritarch biostratigraphy applicable in Precambrian stratigraphy (Sergeev, 2009). In fact, this has been already well demonstrated for the Ediacaran period (Grey, 2005;Willman et al., 2006). ...
As demonstrated by several recent publications, geologists still disagree about the lithostratigraphic subdivision of the Volta basin sedimentary infilling. Correlations at the scale of the Volta basin were up to now largely limited by the discontinuity of outcrops along the basin margin and by the scarcity of stratigraphic constraints within the sedimentary succession. Even if a subdivision of the Volta basin infilling into three main groups (Bombouaka-Kwahu, Oti, and Obosum Groups) is now generally accepted, there is no agreement for lithostratigraphic subdivision at the formation scale. The Bombouaka-Kwahu Group, which represents first deposits of the Volta basin sedimentary infilling, is particularly concerned. During mapping project in Ghana (Mineral Sector Support Programme (MSSP) in Ghana, funded by European Union), authors proceeded to a sedimentological study of the Bombouaka-Kwahu Group deposits on the Kwahu Plateau area. Some samples collected during field mapping were analyzed on a palynological point of view and revealed several layers rich in acritarchs. Silicoclastic sediments composing the Bombouaka-Kwahu Group are distinguished in 12 main facies associations which are interpreted to be representative of both marine and continental environments. Sedimentological study of these facies associations leads to identify a cyclic vertical evolution of deposition settings at different scales, which are interpreted as sequences. The Bombouaka-Kwahu Group is thus composed of three distinct macrosequences (about 300 to 500 meters thick) interpreted as deltaic progradational sequences. Each macrosequence has been used to define formations for mapping, sequence stratigraphy key surfaces being considered as limits for cartographic units. Comparison of sedimentological data collected on the Kwahu Plateau, with those recently published for the Volta basin western margin (Kintampo Massif), shows similarities in sequential signals that are suggestive of a regional continuity of macrosequences. Even if stratigraphic resolution of palynological ages is quite coarse in the Meso - Neoproterozoic successions, the acritarch content of collected samples provides new stratigraphic constraints which, with sedimentological and sequential analysis, is used to discuss lithostratigraphic correlations into the Bombouaka-Kwahu Group at the scale of the Volta basin. Two samples provide acritarch assemblages that are indicative of a post-Mesoproterozoic, early Neoproterozoic (Tonian) age for the two upper macrosequences / formations. The stratigraphic interval deduced from acritarch assemblages is consistent with available stratigraphic data in the Volta basin and particularly with the Rb/Sr age obtained in the Fosse-aux-Lions / Poubougou Formations defined on the northern margin. The stratigraphic equivalence between Fosse-aux-Lions / Poubougou Fm and Abetifi-Anyaboni Fm, and the regional continuity of macrosequence signals are used to discuss correlations at the scale of the Volta basin, between numerous lithostratigraphic subdivisions published on the Bombouaka-Kwahu Group. The correlation table of lithostratigraphic subdivisions we proposed needs to be confirmed by new data acquisition in order (i) to improve stratigraphic constraints for the Bombouaka-Kwahu Group and (ii) to identify and compare preserved macrosequence signals along Volta basin northern margin. If correlations hypotheses are confirmed, geological map of the Volta basin deposits could be largely updated and the knowledge of the beginning of Volta basin history better constrained.
... Other Precambrian micro-organisms previously assigned to the foraminifers (e.g., Milon, 1928: p. 11-12) are now excluded. During the Cambrian, many microfossils attributed to the foraminifers were more likely cyanobacteria or lower ascomycetes (see for discussion Chuvashov et al., 1987;Hermann and Podkovyrov, 2008); e.g., the Reitlingerellida, confused with Ammodiscus by Cherchi and Schroeder (1985: p. 152, pl. 3, figs. 1, 2), or Renalcis of Riding and Brasier (1975). ...
Because the Foraminifera are very sensitive to various environmental parameters (e.g., water temperature, salinity, light, etc.), there are important proxies used for palaeoenvironmental and palaeogeographic reconstructions. The evolution of the structure, shape and size of the mineralized tests of Foraminifera can directly reflect the variation of these parameters through geological time. Furthermore, their biostratigraphic value has been widely demonstrated. In this context, the systematics, evolution and ecological behaviour of the first mineralized Palaeozoic Foraminifera are important to discuss in order to have a clearer picture of former shallow marine environments, and finally understand their distribution through space and time. The systematics of the fossil group of Foraminifera that first developed a mineralized test remains under discussion. These early foraminifers are considered as Textulariata (as generally admitted), recrystallized Fusulinata or an independent group, sometimes called Astrorhizata. In this paper, we argue to assign the early foraminifers to the Fusulinata, and to subdivide this class into six orders: Parathuramminida, Archaediscida and Earlandiida (forming together the subclass Afusulinana n. subcl.), and Tournayellida, Endothyrida and Fusulinida (subclass Fusulinana nom. translat.). These subdivisions are discussed and linked to the first occurrences of the later classes: Miliolata, Nodosariata and Textulariata. The environmental living conditions of the first fossilized foraminifers remain enigmatic during the Early Palaeozoic (Cambrian-Silurian). During the Late Silurian, the unilocular Parathuramminida started to colonize the inner parts of ramps and platforms. The first plurilocular microgranular foraminifers (Semitextulariidae, Nanicellidae, and Eonodosariidae) developed in back-reefal systems and in deeper-water environments (“griottes”-type nodular limestone) from the late Early Devonian to the early Late Devonian. The Moravamminida, another group of possible Protista, are typical markers of Devonian inner ramp systems. The Semitextulariidae, Nanicellidae, and Eonodosariidae did not survive the Frasnian/Famennian crisis. From the Tournaisian to the Serpukhovian (Mississippian subsystem or Early Carboniferous), numerous new genera and species of Archaediscida, Tournayellida and Endothyrida flourished but remained confined to inner ramp environments. In deeper water depositional systems (i.e. coral thrombolite microbialites and/or nodular limestones), a few opportunistic Foraminifera were living up to the disphotic zone. During the Pennsylvanian (Bashkirian to Gzhelian), the habitats extended to more confined, shallower areas of the inner ramp (with Staffelloidea). During the Late Carboniferous and Permian, the larger Fusulinida (Schwagerinoidea) reached the outer platform as they have been commonly reworked in calciturbidites. During the Late Permian, some taxa were even able to live in hypersaline environments such as sabkhas and hypersaline lagoons. Two major biotic crises occurred during the Permian (post-Middle and post-Late Permian crisis), but the number of survivors after the PTE (Permian/Triassic Extinction) is probably higher than previously admitted. From the Cambrian to the Serpukhovian, the Foraminifera were probably all infaunal or living at the sediment/seawater interface. The TROX and TROX-2 models are consequently applicable. Anoxia, often suggested as triggering environmental crises, was likely not systematically lethal for many infaunal foraminifers. The late Tournaisian-Changhsingian Tetrataxis genus was probably the first epiphyte foraminifer, because of its conical, limpet-like test. The Tetrataxidae (e.g., Tetrataxis, Pseudotaxis and Abadehella) constituted the unique trochospirally coiled plurilocular foraminiferal family of the Palaeozoic. The Bradyinoidea, Ozawainelloidea, Staffelloidea, and the Pseudoschwagerinidae (Schwagerinoidea) are other examples of Pennsylvanian-Permian epiphytes but cannot be considered as planktonic taxa. All the other Schwagerinoidea are related to high-energy environments and coarse-grained substrates. Their history, as well as that of the Neoschwagerinoidea, was likely subject to the vicissitudes of their endosymbiotic algae.
