Leonid Popov | National Museum of Wales (original) (raw)
Papers by Leonid Popov
Scientific Reports , 2019
The Tremadocian (Early Ordovician) is currently considered a time span of greenhouse conditions w... more The Tremadocian (Early Ordovician) is currently considered a time span of greenhouse conditions with tropical water surface temperature estimates, interpolated from oxygen isotopes, approaching 40 °C. In the mid-latitude Baltoscandian Basin, conodonts displaying low δ 18 O values, which suggest high temperatures (>40 °C) in the water column, are in contrast with the discovery of contemporaneous glendonite clusters, a pseudomorph of ikaite (CaCO 3 ·6H 2 O) traditionally considered as indicator of near-freezing bottom-water conditions. The massive precipitation of this temperature sensitive mineral is associated with transgressive conditions and high organic productivity. As a result, the lower Tremadocian sediments of Baltoscandia apparently contain both "greenhouse" pelagic signals and near-freezing substrate indicators. This paradox points to other primary controlling mechanisms for ikaite precipitation in kerogenous substrates, such as carbonate alkalinity, pH and Mg/Ca ratios, as recently constrained by laboratory experiments. Preservation of "hot" conodonts embedded in kerogenous shales rich in δ 18 o-depleted glendonites suggests both the onset of sharp thermal stratification patterns in a semi-closed basin and the assumed influence of isotopically depleted freshwater yielded by fluvial systems. Except one rather controversial note 1 , the record of glendonites displays an apparent gap from Neopoterozoic 2 to Permian 3 times. However, similar calcareous nodular aggregates embedded in Tremadocian black shales of the East Baltic (Fig. 1a), the so-called "antraconites", have been known for more than 150 years. These aggregates are documented from 24 geographical localities in the Türisalu and Koporiye formations (Cordylodus angulatus-Paltodus deltifer pristinus zones) and sporadically in the Orasoja Member (upper part of the Kallavere Formation; Cordylodus angulatus-Paltodus deltifer pristinus zones), exposed along 600 km of the Baltic-Ladoga Glint 4 , a transect linking North Estonia to the eastern St Petersburg area (Fig. 1b). All these units were accumulated in the
The Silurian biostratigraphy, lithostratigraphy, and facies of Central Iran including the Kashmar... more The Silurian biostratigraphy, lithostratigraphy, and facies of Central Iran including the Kashmar (Boghu Mountains), Tabas (Derenjal Mountains, Ozbak-Kuh), Anarak (Pole Khavand) and Kerman regions is reviewed and updated. The current state of knowledge of the Silurian in the Zagros Basin, Alborz, Kopet-Dagh and Talysh regions, as well as in a few areas scattered across the Sabzevar Zone, and the Sanandaj-Sirjan terranes is also reviewed. Silurian volcanism in various parts of Iran is briefly discussed. The end of the Ordovician coincided with a widespread regression across Iran synchronous with the Hirnantian glaciation, and only in the Zagros Basin is there a continuous Ordovician–Silurian transition represented by graptolitic black shales of the Sarchahan Formation. In the Central-East Iranian Platform marine sedimentation re-commenced in the early to mid Aeronian. By the Sheinwoodian, carbonate platform depositional environments were established along its northeastern margin. In other parts of Iran (e.g., Kopet-Dagh and the Sabzevar Zone), siliciclastic sedimentation continued probably into the late Silurian. The Silurian conodont and brachiopod biostratigraphy of Central Iran is significantly updated facilitating a precise correlation with the Standard Global Chronostratigraphic Scale, as well as with key Silurian sections in other parts of Iran. The Silurian lithostratigraphy is considerably revised and two new lithostratigraphical units, namely the Boghu and Dahaneh-Kalut formations, are introduced.
Acta Geologica Polonica, 2017
Popov, L.E. and Cocks, L.R.M. 2017. Late Ordovician palaeogeography and the positions of the Kaza... more Popov, L.E. and Cocks, L.R.M. 2017. Late Ordovician palaeogeography and the positions of the Kazakh ter-ranes through analysis of their brachiopod faunas. Acta Geologica Polonica, 67 (3), 323–380. Warszawa. Detailed biogeographical and biofacies analyses of the Late Ordovician brachiopod faunas with 160 genera, grouped into 94 faunas from individual lithotectonic units within the Kazakh Orogen strongly support an archipelago model for that time in that area. The Kazakh island arcs and microcontinents within several separate clusters were located in the tropics on both sides of the Equator. Key units, from which the Late Ordovician faunas are now well known, include the Boshchekul, Chingiz-Tarbagatai, and Chu-Ili terranes. The development of brachiopod biogeography within the nearly ten million year time span of the Late Ordovician from about 458 to 443 Ma (Sandbian, Katian, and Hirnantian), is supported by much new data, including our revised identifications from the Kazakh Orogen and elsewhere. The Kazakh archipelago was west of the Australasian segment of the Gondwana Supercontinent, and relatively near the Tarim, South China and North China continents, apart from the Atashu-Zhamshi Microcontinent, which probably occupied a relatively isolated position on the southwestern margin of the archipelago. Distinct faunal signatures indicate that the Kazakh terranes were far away from Baltica and Siberia throughout the Ordovician. Although some earlier terranes had joined each other before the Middle Ordovician, the amalgamation of Kazakh terranes into the single continent of Kazakhstania by the end of the Ordovician is very unlikely. The Late Ordovician brachiopods from the other continents are also compared with the Kazakh faunas and global provincialisation statistically determined.
The Pol-e Khavand area south-east of the town of Anarak preserves important clues for understandi... more The Pol-e Khavand area south-east of the town of Anarak preserves important clues for understanding geological evolution of Central Iran during the Palaeozoic. New observations confirm the non-conformable relationship between Doshakh metamorphites and overlying unmetamorphosed Lower Palaeozoic sediments, suggesting accretion of the volcanic arc in front of the Yazd block sometime in the late Cambrian to early Ordovician. The newly introduced volcano-sedimentary Polekhavand Formation preserves evidence of a ?Late Cambrian to Early Ordovician post-collisional bimodal volcanism and related extensional regime in the Pol-e Khavand area during that time. The Middle to Upper Ordovician interval of the studied succession is assigned to the newly introduced Chahgonbad Formation. The Darriwilian age of the base of this lithostratigraphical unit is demonstrated by the brachiopods Tritoechia and Yangtzeella which co-occur with a diverse a cephalopod assemblage. The low diversity fauna including brachiopods Hibernodonta sp., Hindella sp., Rostricellula cf. ambigena and trilobites Vietnamia cf. teichmulleri suggest a Katian age for the upper part of the unit. There is insufficient evidence for the existence of the hypothetical Palaeo-Tethys suture zone south of the Pol-e Khavand area.
Journal of Paleontology, 2005
Seven genera and eight species of lingulate brachiopods were recovered from the House Limestone a... more Seven genera and eight species of lingulate brachiopods were recovered from the House Limestone and lower Fillmore Formation, Ibex area, Utah, USA. These strata are assigned to the upper Skullrockian Stage and lower Stairsian Stage of the Ibexian Series (Iapetognathus Conodont Zone to Low Diversity Interval) and are correlated with the Tremadocian Series of the Acado-Baltic Faunal Province. The fauna includes two new linguloid species, Spinilingula prisca and Wahwahlingula sevierensis, one new siphonotretoid species, Schizambon obtusus, and two new acrotretoid species, Eurytreta fillmorensis and Ottenbyella ibexiana. The last species is the first record of the genus in North America and suggests a correlation of the basal Fillmore Formation with the Ceratopyge Limestone in Sweden. A Siphonobolus? covered by long hollow spines may be one of the oldest siphonotretides with such ornament. This fauna and those described previously from older Utah strata document the biodiversification of the Cambrian-Ordovician lingulate brachiopods and demonstrate their potential for regional and intercontinental correlation.
Journal of the Geological Society, 2013
Geobios, Jan 1, 2001
The Tritoechiidae are redefined following study of nine species of the genera Tritoechia, Eremoto... more The Tritoechiidae are redefined following study of nine species of the genera Tritoechia, Eremotoechia, Martellia Pomatotrema, Protambonites and Korinevskia nov. gen. in Kazakhstanian brachiopod faunas from the upper Tremadoc to lower Caradoc. Six species are new: Tritoechia crassa, T. tokmakensis, Eremotoechia inchoata, E. spissa, Martellia reliqua and Pomatotrema fecunda. In key characters of shell morphology the Tritoechiidae demonstrate close affinity with billingsellids and are therefore reassigned to the superfamily Billingselloidea.La Famille Tritoechiidae est redéfinie sur la base de l'étude de neuf espèces appartenant aux genres Tritoechia, Eremotoechia, Martellia Pomatotrema, Protambonites et Korinevskia nov. gen. de la faune de brachiopodes du Kazakhstan du Trémadoc supérieur au Caradoc inférieur. Six nouvelles espèces sont décrites Tritoechia crassa, T. tokmakensis, Eremotoechia inchoata, E. spissa, Martellia reliqua et Pomatotrema fecunda. Les caractères diagnostiques de la coquille des Tritoechiidés attestent de fortes affinités avec les Billingsellidés; de ce fait les Tritoechiidés sont rapportés à la Superfamille Bilingselloidea.
M. 2008: Organophosphatic stem group brachiopods: implications for the phylogeny of the subphylum... more M. 2008: Organophosphatic stem group brachiopods: implications for the phylogeny of the subphylum Linguliformea. Fossils and Strata , No. 54, pp. 3-11. ISSN 0024-1164 The recognition of potential organophosphatic-shelled stem group brachiopods has important implications for the understanding of brachiopod phylogeny. These groups fall outside the two currently recognized classes of the subphylum Linguliformea -the Lingulata and Paterinata. However, their organophosphatic shell structure and evidence of penetrative setae demonstrate that they are linked phylogenetically with the linguliforms. The proposed Early Cambrian stem-group brachiopods include the problematic, possibly vermiform, organophosphatic sclerite-bearing tannuolinids and the more brachiopod-like Mickwitzia and Heliomedusa . A columnar shell fabric, which was considered previously as a derived feature of acrotretids, is now known also from the tannuolinid Micrina as well as from Mickwitzia , thus indicating that this type of shell structure may be a plesiomorphic character; it was retained in acrotretids and some lingulids, like the Lingulellotretidae, which is here shown to include a wide variety of columnar fabrics. A columnar shell structure ( sensu lato ) is also identified here from the enigmatic South American Ordovician linguliform brachiopod Bistramia. The shells of Mickwitzia and Heliomedusa also have various types of thicker cylindrical columns ('tubes'), some of which were clearly open to the exterior surface and can be inferred to have contained setal structures penetrating the shell. Identical perforations are present in Micrina , and a similar function can be inferred for both the columnar fabric of some recently discovered paterinids described here and possibly also of some siphonotretids, indicating that these groups may also be closer to the stem of the brachiopods. ᮀ Brachiopoda, Lingulellotretidae, Linguliformea, Paterinida, phylogeny, shell structure, Siphonotretida. Lars E. Holmer [lars.holmer@pal.uu.se] and Michael Streng [michael.streng@geo.uu.se],
Journal of Paleontology, 2005
Seven genera and eight species of lingulate brachiopods were recovered from the House Limestone a... more Seven genera and eight species of lingulate brachiopods were recovered from the House Limestone and lower Fillmore Formation, Ibex area, Utah, USA. These strata are assigned to the upper Skullrockian Stage and lower Stairsian Stage of the Ibexian Series (Iapetognathus Conodont Zone to Low Diversity Interval) and are correlated with the Tremadocian Series of the Acado-Baltic Faunal Province. The fauna includes two new linguloid species, Spinilingula prisca and Wahwahlingula sevierensis, one new siphonotretoid species, Schizambon obtusus, and two new acrotretoid species, Eurytreta fillmorensis and Ottenbyella ibexiana. The last species is the first record of the genus in North America and suggests a correlation of the basal Fillmore Formation with the Ceratopyge Limestone in Sweden. A Siphonobolus? covered by long hollow spines may be one of the oldest siphonotretides with such ornament. This fauna and those described previously from older Utah strata document the biodiversification of the Cambrian-Ordovician lingulate brachiopods and demonstrate their potential for regional and intercontinental correlation.
Philosophical Transactions of The Royal Society B: Biological Sciences, 1996
Two trilobite faunas of late Ordovician (Sandbian and Katian) age are described from the silicicl... more Two trilobite faunas of late Ordovician (Sandbian and Katian) age are described from the siliciclastic Karagach Formation, western Tarbagatai Range, eastern Kazakhstan. They comprise 15 families and 24 genera and include the new taxa Agerina acutilimbata sp. nov., Birmanites akchiensis sp. nov., Dulanaspis karagachensis sp. nov. and Kimakaspis kovalevskyi gen. et sp. nov. Most of the Karagach Formation yields graptolites characteristic of the Diplograptus foliaceus [multidens] Biozone, which are associated with the older trilobite fauna; the uppermost part, which is the source of the younger trilobite fauna, contains Orthograptus quadrimucronatus and
Dicranograptus hians which suggest a younger age, equating with the lowermost Ensigraptus caudatus Biozone, and the base of the Katian Stage. Most of the trilobite genera in both faunas have a wide geographical distribution in the late Ordovician, although Dulanaspis and Sinocybele are characteristic
of low latitude eastern peri-Gondwanan faunas.
The Llandovery deposits of Iran preserve an important record of the biotic recovery of the benthi... more The Llandovery deposits of Iran preserve an important record of the biotic recovery of the
benthic faunas in temperate latitude Gondwana after the Terminal Ordovician Mass Extinction.
During that time, the terranes of Kopet-Dagh and Central Iran probably formed part of the
Gondwana domain. Genera characteristic of the open shelf are mostly derived from pan-tropical
Rhuddanian faunas and contain a significant proportion of taxa which survived the Terminal
Ordovician Mass Extinction. A significant number of taxa from shallow shelf biofacies show
links to contemporaneous and older faunas of South China. Major components of the benthic
fauna including tabulate and rugose corals, brachiopods, bryozoans and ostracods, as well as
cephalopods, were new to the region and show clear links to contemporaneous low latitude
faunas (e.g. Laurentia, Baltica and South China). During the Aeronian, peri-Gondwanan terranes
of Central Iran, Kope-Dagh and Afghanistan supported shallow water faunas bearing a common
biogeographical signature, suggesting that they were positioned in relatively close proximity to
each other, and probably lay in temperate southern palaeolatitudes. Data from Iran also show
that major patterns of biofacies differentiation known for the most of the Silurian Period were
developed during the Aeronian Age.
Alcheringa: An Australasian Journal of Palaeontology, 1994
The Early Triassic (late Induan to early Olenekian) Lingula borealis Bittner, from the Russkii Is... more The Early Triassic (late Induan to early Olenekian) Lingula borealis Bittner, from the Russkii
Island on the Pacific cost of south-eastern Russia is revised, based on re-examination of the type material.
Although this species, like most described Triassic lingulids, has remained very poorly understood due to
the lack of information on important characters, such as musculature and mantle canals, it has been commonly
recorded in subsequent studies and included in attempts at understanding the patterns of extinction
and recovery at around the Permian–Triassic boundary. Linguliform brachiopods are some of the notable
survivors of this significant mass extinction event. Lingula borealis has previously been referred to Lingularia
and provisionally synonymised with Lingularia similis Biernat & Emig. Here, it is shown that it
differs from Lingularia similis mainly in characters of mantle canals, musculature and most importantly
in details of the pedicle nerve impression. In Lingularia borealis, the impression of the pedicle nerve is
symmetrical and goes almost straight between the individual ventral umbonal muscle scars, whereas in
Lingularia similis it is asymmetrically positioned towards the smaller left component of the ventral umbonal
muscle scar. Shell structures and details of preserved ontogenies have also proven to be important
for the discrimination of lingulid taxa, but cannot be provided from the types of Lingularia borealis.
Despite many major advances in recent years, three key challenges remain in bringing clarity to t... more Despite many major advances in recent years, three key challenges remain in bringing clarity to the early history of the phylum: (1) identifying the origin, morphology and life modes of the first brachiopods; (2) understanding the relationships of the major groups to each other and higher sister taxa; and (3) unravelling the roles of the Cambrian and Ordovician radiations that set the agenda for much of subsequent brachiopod evolution. Since some 95% of all brachiopod taxa are extinct, the fossil record is the primary source of data to frame and test models for the evolution of the phylum. The acquisition of new, and the redescription of existing faunas, in precise spatial and temporal frameworks, using new and well-established analytical and investigative techniques, are as important as ever.
Palaeogeography, Palaeoclimatology, Palaeoecology, 2011
High-latitude Hirnantian diamictites (Dargaz Formation) and lower-Silurian kerogenous black shale... more High-latitude Hirnantian diamictites (Dargaz Formation) and lower-Silurian kerogenous black shales (Sarchahan Formation) are locally exposed in the Zagros Mountains. The glaciogenic Dargaz deposits consist of three progradational/retrogradational cycles, each potentially controlled by the regional advance and retreat of the Hirnantian ice sheet. Glacial incisions of sandstone packages change laterally from simple planar to high-relief (b 40 m deep) scalloped truncating surfaces that join laterally forming complex polyphase unconformities that scour into the underlying Seyahou Formation. The glaciated source area was to the present-day west, in the region of the Arabian Shield, where numerous tunnel valleys have been reported. Based on a study of palynomorphs and graptolites, the glaciomarine Dargaz diamictites are dated as Hirnantian, whereas the youngest Sarchahan black shales are diachronous throughout the Zagros, ranging from the Hirnantian persculptus to the earliest Aeronian (Llandovery) triangulatus zones. The diachronism is related to onlapping geometries capping an inherited glaciogenic palaeorelief that preserved different depth incisions and source areas. Our data suggest the presence of Hirnantian satellite ice caps adjacent the Zagros margin of Arabia and allow us to fill a gap in the present knowledge of the peripheral extension of the Late Ordovician ice sheet.
Earth and Environmental Science Transactions of the Royal Society of Edinburgh, 2014
Brachiopods are among the most common components of the Late Ordovician benthic faunal assemblage... more Brachiopods are among the most common components of the Late Ordovician benthic faunal assemblages recorded in the Faraghan Mountains, Zagros Ranges, Iran. A total of 19 species referable to 16 genera are identified, including seven new species; namely Drabovia elegans, Hibernodonta bonehensis, Hedstroemina zakeenensis, Jezercia faraghani, Protomendacella multicostata, Tafilaltia dargazensis and Tafilaltia seyahouensis. Reported brachiopod assemblages are oligotaxic (2-3 species per assemblage) to monotaxic. The only exception is the medium diversity Aegiromena-Hedstroemina Association, with up to ten species, which occurs at the lower part of the A. nigerica Zone. Low diversity patterns were probably controlled by the palaeogeographical position of the region in high southern latitudes throughout the Ordovician. Paterula sp. and Iranospirifer sp. are the only brachiopods documented from the Silurian (Llandovery) Sarchahan Formation. This paper gives the first detailed report of shelly fossils from the Llandovery 'hot shale' of the Arabian margin of Gondwana. Most of the Katian genera, and many of their species, are shared with neighbouring high-to mid-latitude peri-Gondwanan margins,
This paper reviews the global biogeography and affinities of the Bradoriida, a group of Cambrian–... more This paper reviews the global biogeography and affinities of the Bradoriida, a group of Cambrian–early Ordovician arthropods. Bradoriida appear in the fossil record during the early Cambrian, just prior to the earliest trilobite faunas. Seven families may form a natural (monophyletic) group of Bradoriida sensu stricto, comprising Cambriidae, Kunmingellidae, Comptalutidae, Bradoriidae, Hipponicharionidae, Beyrichonidae and Svealutidae. Amongst the Bradoriida sensu lato, some forms that lie outside these families have carapace designs that suggest an ostracod affinity, particularly Altajanella and Vojbokalina. Bradoriida formed a major element of the 'Cambrian evolutionary fauna' and are components of the Chengjiang, Burgess Shale, and Buen Formation Lagerstätten. Bradoriida achieved global distribution from the Atdabanian (early Cambrian). Their diversity peaked during the early and middle Cambrian, with highest diversity at the species and genus level amongst the palaeo-tropical faunas of the South China (17 genera) and east Gondwana palaeocontinental regions (23 genera). By contrast Laurentian faunas were of much lower diversity (10 genera for the whole Cambrian). Bradoriid diversity declined rapidly from the latest middle Cambrian, a trend that may be related to the major extinction of trilobites at the base of the late Cambrian. The youngest Bradoriida comprise a few, rare Ordovician forms. Bradoriids appear to have occupied well-oxygenated marine shelf facies. The biogeographical patterns of early and middle Cambrian Bradoriida suggest climatic control on their distribution (temperate and tropical faunas), together with palaeogeographical constraints that also reflect trilobite provinciality. Kunmingellids and comptalutids were restricted to palaeo-tropical/subtropical sites, but migrated between South China, Siberia and eastern Gondwana palaeocontinents. They are absent from the mid-and high latitude faunas of the western Gondwana, Avalonia and Baltica palaeocontinental areas that were dominated by hipponicharionids, beyrichonids and Bradoriidae. The Laurentia palaeocontinent was isolated from the main zones of bradoriid diversity, but its faunas include a number of early and middle Cambrian Bradoriidae (Indota, Bradoria, Walcottella), and the region was colonised by cosmopolitan cambriids during the early Cambrian and by supposed pelagic svealutids (Liangshanella and Anabarochilina) during the middle Cambrian. The genera Walcottella, Dielymella and Bullaluta were endemic to Laurentia. One species of Anabarochilina that possibly dwelt near the sea-surface achieved an equatorial to high southern latitude (70° S) distribution during the late middle Cambrian (Lejopyge laevigata Biozone), perhaps reflecting a reduced latitudinal temperature gradient for near surface ocean waters.
Scientific Reports , 2019
The Tremadocian (Early Ordovician) is currently considered a time span of greenhouse conditions w... more The Tremadocian (Early Ordovician) is currently considered a time span of greenhouse conditions with tropical water surface temperature estimates, interpolated from oxygen isotopes, approaching 40 °C. In the mid-latitude Baltoscandian Basin, conodonts displaying low δ 18 O values, which suggest high temperatures (>40 °C) in the water column, are in contrast with the discovery of contemporaneous glendonite clusters, a pseudomorph of ikaite (CaCO 3 ·6H 2 O) traditionally considered as indicator of near-freezing bottom-water conditions. The massive precipitation of this temperature sensitive mineral is associated with transgressive conditions and high organic productivity. As a result, the lower Tremadocian sediments of Baltoscandia apparently contain both "greenhouse" pelagic signals and near-freezing substrate indicators. This paradox points to other primary controlling mechanisms for ikaite precipitation in kerogenous substrates, such as carbonate alkalinity, pH and Mg/Ca ratios, as recently constrained by laboratory experiments. Preservation of "hot" conodonts embedded in kerogenous shales rich in δ 18 o-depleted glendonites suggests both the onset of sharp thermal stratification patterns in a semi-closed basin and the assumed influence of isotopically depleted freshwater yielded by fluvial systems. Except one rather controversial note 1 , the record of glendonites displays an apparent gap from Neopoterozoic 2 to Permian 3 times. However, similar calcareous nodular aggregates embedded in Tremadocian black shales of the East Baltic (Fig. 1a), the so-called "antraconites", have been known for more than 150 years. These aggregates are documented from 24 geographical localities in the Türisalu and Koporiye formations (Cordylodus angulatus-Paltodus deltifer pristinus zones) and sporadically in the Orasoja Member (upper part of the Kallavere Formation; Cordylodus angulatus-Paltodus deltifer pristinus zones), exposed along 600 km of the Baltic-Ladoga Glint 4 , a transect linking North Estonia to the eastern St Petersburg area (Fig. 1b). All these units were accumulated in the
The Silurian biostratigraphy, lithostratigraphy, and facies of Central Iran including the Kashmar... more The Silurian biostratigraphy, lithostratigraphy, and facies of Central Iran including the Kashmar (Boghu Mountains), Tabas (Derenjal Mountains, Ozbak-Kuh), Anarak (Pole Khavand) and Kerman regions is reviewed and updated. The current state of knowledge of the Silurian in the Zagros Basin, Alborz, Kopet-Dagh and Talysh regions, as well as in a few areas scattered across the Sabzevar Zone, and the Sanandaj-Sirjan terranes is also reviewed. Silurian volcanism in various parts of Iran is briefly discussed. The end of the Ordovician coincided with a widespread regression across Iran synchronous with the Hirnantian glaciation, and only in the Zagros Basin is there a continuous Ordovician–Silurian transition represented by graptolitic black shales of the Sarchahan Formation. In the Central-East Iranian Platform marine sedimentation re-commenced in the early to mid Aeronian. By the Sheinwoodian, carbonate platform depositional environments were established along its northeastern margin. In other parts of Iran (e.g., Kopet-Dagh and the Sabzevar Zone), siliciclastic sedimentation continued probably into the late Silurian. The Silurian conodont and brachiopod biostratigraphy of Central Iran is significantly updated facilitating a precise correlation with the Standard Global Chronostratigraphic Scale, as well as with key Silurian sections in other parts of Iran. The Silurian lithostratigraphy is considerably revised and two new lithostratigraphical units, namely the Boghu and Dahaneh-Kalut formations, are introduced.
Acta Geologica Polonica, 2017
Popov, L.E. and Cocks, L.R.M. 2017. Late Ordovician palaeogeography and the positions of the Kaza... more Popov, L.E. and Cocks, L.R.M. 2017. Late Ordovician palaeogeography and the positions of the Kazakh ter-ranes through analysis of their brachiopod faunas. Acta Geologica Polonica, 67 (3), 323–380. Warszawa. Detailed biogeographical and biofacies analyses of the Late Ordovician brachiopod faunas with 160 genera, grouped into 94 faunas from individual lithotectonic units within the Kazakh Orogen strongly support an archipelago model for that time in that area. The Kazakh island arcs and microcontinents within several separate clusters were located in the tropics on both sides of the Equator. Key units, from which the Late Ordovician faunas are now well known, include the Boshchekul, Chingiz-Tarbagatai, and Chu-Ili terranes. The development of brachiopod biogeography within the nearly ten million year time span of the Late Ordovician from about 458 to 443 Ma (Sandbian, Katian, and Hirnantian), is supported by much new data, including our revised identifications from the Kazakh Orogen and elsewhere. The Kazakh archipelago was west of the Australasian segment of the Gondwana Supercontinent, and relatively near the Tarim, South China and North China continents, apart from the Atashu-Zhamshi Microcontinent, which probably occupied a relatively isolated position on the southwestern margin of the archipelago. Distinct faunal signatures indicate that the Kazakh terranes were far away from Baltica and Siberia throughout the Ordovician. Although some earlier terranes had joined each other before the Middle Ordovician, the amalgamation of Kazakh terranes into the single continent of Kazakhstania by the end of the Ordovician is very unlikely. The Late Ordovician brachiopods from the other continents are also compared with the Kazakh faunas and global provincialisation statistically determined.
The Pol-e Khavand area south-east of the town of Anarak preserves important clues for understandi... more The Pol-e Khavand area south-east of the town of Anarak preserves important clues for understanding geological evolution of Central Iran during the Palaeozoic. New observations confirm the non-conformable relationship between Doshakh metamorphites and overlying unmetamorphosed Lower Palaeozoic sediments, suggesting accretion of the volcanic arc in front of the Yazd block sometime in the late Cambrian to early Ordovician. The newly introduced volcano-sedimentary Polekhavand Formation preserves evidence of a ?Late Cambrian to Early Ordovician post-collisional bimodal volcanism and related extensional regime in the Pol-e Khavand area during that time. The Middle to Upper Ordovician interval of the studied succession is assigned to the newly introduced Chahgonbad Formation. The Darriwilian age of the base of this lithostratigraphical unit is demonstrated by the brachiopods Tritoechia and Yangtzeella which co-occur with a diverse a cephalopod assemblage. The low diversity fauna including brachiopods Hibernodonta sp., Hindella sp., Rostricellula cf. ambigena and trilobites Vietnamia cf. teichmulleri suggest a Katian age for the upper part of the unit. There is insufficient evidence for the existence of the hypothetical Palaeo-Tethys suture zone south of the Pol-e Khavand area.
Journal of Paleontology, 2005
Seven genera and eight species of lingulate brachiopods were recovered from the House Limestone a... more Seven genera and eight species of lingulate brachiopods were recovered from the House Limestone and lower Fillmore Formation, Ibex area, Utah, USA. These strata are assigned to the upper Skullrockian Stage and lower Stairsian Stage of the Ibexian Series (Iapetognathus Conodont Zone to Low Diversity Interval) and are correlated with the Tremadocian Series of the Acado-Baltic Faunal Province. The fauna includes two new linguloid species, Spinilingula prisca and Wahwahlingula sevierensis, one new siphonotretoid species, Schizambon obtusus, and two new acrotretoid species, Eurytreta fillmorensis and Ottenbyella ibexiana. The last species is the first record of the genus in North America and suggests a correlation of the basal Fillmore Formation with the Ceratopyge Limestone in Sweden. A Siphonobolus? covered by long hollow spines may be one of the oldest siphonotretides with such ornament. This fauna and those described previously from older Utah strata document the biodiversification of the Cambrian-Ordovician lingulate brachiopods and demonstrate their potential for regional and intercontinental correlation.
Journal of the Geological Society, 2013
Geobios, Jan 1, 2001
The Tritoechiidae are redefined following study of nine species of the genera Tritoechia, Eremoto... more The Tritoechiidae are redefined following study of nine species of the genera Tritoechia, Eremotoechia, Martellia Pomatotrema, Protambonites and Korinevskia nov. gen. in Kazakhstanian brachiopod faunas from the upper Tremadoc to lower Caradoc. Six species are new: Tritoechia crassa, T. tokmakensis, Eremotoechia inchoata, E. spissa, Martellia reliqua and Pomatotrema fecunda. In key characters of shell morphology the Tritoechiidae demonstrate close affinity with billingsellids and are therefore reassigned to the superfamily Billingselloidea.La Famille Tritoechiidae est redéfinie sur la base de l'étude de neuf espèces appartenant aux genres Tritoechia, Eremotoechia, Martellia Pomatotrema, Protambonites et Korinevskia nov. gen. de la faune de brachiopodes du Kazakhstan du Trémadoc supérieur au Caradoc inférieur. Six nouvelles espèces sont décrites Tritoechia crassa, T. tokmakensis, Eremotoechia inchoata, E. spissa, Martellia reliqua et Pomatotrema fecunda. Les caractères diagnostiques de la coquille des Tritoechiidés attestent de fortes affinités avec les Billingsellidés; de ce fait les Tritoechiidés sont rapportés à la Superfamille Bilingselloidea.
M. 2008: Organophosphatic stem group brachiopods: implications for the phylogeny of the subphylum... more M. 2008: Organophosphatic stem group brachiopods: implications for the phylogeny of the subphylum Linguliformea. Fossils and Strata , No. 54, pp. 3-11. ISSN 0024-1164 The recognition of potential organophosphatic-shelled stem group brachiopods has important implications for the understanding of brachiopod phylogeny. These groups fall outside the two currently recognized classes of the subphylum Linguliformea -the Lingulata and Paterinata. However, their organophosphatic shell structure and evidence of penetrative setae demonstrate that they are linked phylogenetically with the linguliforms. The proposed Early Cambrian stem-group brachiopods include the problematic, possibly vermiform, organophosphatic sclerite-bearing tannuolinids and the more brachiopod-like Mickwitzia and Heliomedusa . A columnar shell fabric, which was considered previously as a derived feature of acrotretids, is now known also from the tannuolinid Micrina as well as from Mickwitzia , thus indicating that this type of shell structure may be a plesiomorphic character; it was retained in acrotretids and some lingulids, like the Lingulellotretidae, which is here shown to include a wide variety of columnar fabrics. A columnar shell structure ( sensu lato ) is also identified here from the enigmatic South American Ordovician linguliform brachiopod Bistramia. The shells of Mickwitzia and Heliomedusa also have various types of thicker cylindrical columns ('tubes'), some of which were clearly open to the exterior surface and can be inferred to have contained setal structures penetrating the shell. Identical perforations are present in Micrina , and a similar function can be inferred for both the columnar fabric of some recently discovered paterinids described here and possibly also of some siphonotretids, indicating that these groups may also be closer to the stem of the brachiopods. ᮀ Brachiopoda, Lingulellotretidae, Linguliformea, Paterinida, phylogeny, shell structure, Siphonotretida. Lars E. Holmer [lars.holmer@pal.uu.se] and Michael Streng [michael.streng@geo.uu.se],
Journal of Paleontology, 2005
Seven genera and eight species of lingulate brachiopods were recovered from the House Limestone a... more Seven genera and eight species of lingulate brachiopods were recovered from the House Limestone and lower Fillmore Formation, Ibex area, Utah, USA. These strata are assigned to the upper Skullrockian Stage and lower Stairsian Stage of the Ibexian Series (Iapetognathus Conodont Zone to Low Diversity Interval) and are correlated with the Tremadocian Series of the Acado-Baltic Faunal Province. The fauna includes two new linguloid species, Spinilingula prisca and Wahwahlingula sevierensis, one new siphonotretoid species, Schizambon obtusus, and two new acrotretoid species, Eurytreta fillmorensis and Ottenbyella ibexiana. The last species is the first record of the genus in North America and suggests a correlation of the basal Fillmore Formation with the Ceratopyge Limestone in Sweden. A Siphonobolus? covered by long hollow spines may be one of the oldest siphonotretides with such ornament. This fauna and those described previously from older Utah strata document the biodiversification of the Cambrian-Ordovician lingulate brachiopods and demonstrate their potential for regional and intercontinental correlation.
Philosophical Transactions of The Royal Society B: Biological Sciences, 1996
Two trilobite faunas of late Ordovician (Sandbian and Katian) age are described from the silicicl... more Two trilobite faunas of late Ordovician (Sandbian and Katian) age are described from the siliciclastic Karagach Formation, western Tarbagatai Range, eastern Kazakhstan. They comprise 15 families and 24 genera and include the new taxa Agerina acutilimbata sp. nov., Birmanites akchiensis sp. nov., Dulanaspis karagachensis sp. nov. and Kimakaspis kovalevskyi gen. et sp. nov. Most of the Karagach Formation yields graptolites characteristic of the Diplograptus foliaceus [multidens] Biozone, which are associated with the older trilobite fauna; the uppermost part, which is the source of the younger trilobite fauna, contains Orthograptus quadrimucronatus and
Dicranograptus hians which suggest a younger age, equating with the lowermost Ensigraptus caudatus Biozone, and the base of the Katian Stage. Most of the trilobite genera in both faunas have a wide geographical distribution in the late Ordovician, although Dulanaspis and Sinocybele are characteristic
of low latitude eastern peri-Gondwanan faunas.
The Llandovery deposits of Iran preserve an important record of the biotic recovery of the benthi... more The Llandovery deposits of Iran preserve an important record of the biotic recovery of the
benthic faunas in temperate latitude Gondwana after the Terminal Ordovician Mass Extinction.
During that time, the terranes of Kopet-Dagh and Central Iran probably formed part of the
Gondwana domain. Genera characteristic of the open shelf are mostly derived from pan-tropical
Rhuddanian faunas and contain a significant proportion of taxa which survived the Terminal
Ordovician Mass Extinction. A significant number of taxa from shallow shelf biofacies show
links to contemporaneous and older faunas of South China. Major components of the benthic
fauna including tabulate and rugose corals, brachiopods, bryozoans and ostracods, as well as
cephalopods, were new to the region and show clear links to contemporaneous low latitude
faunas (e.g. Laurentia, Baltica and South China). During the Aeronian, peri-Gondwanan terranes
of Central Iran, Kope-Dagh and Afghanistan supported shallow water faunas bearing a common
biogeographical signature, suggesting that they were positioned in relatively close proximity to
each other, and probably lay in temperate southern palaeolatitudes. Data from Iran also show
that major patterns of biofacies differentiation known for the most of the Silurian Period were
developed during the Aeronian Age.
Alcheringa: An Australasian Journal of Palaeontology, 1994
The Early Triassic (late Induan to early Olenekian) Lingula borealis Bittner, from the Russkii Is... more The Early Triassic (late Induan to early Olenekian) Lingula borealis Bittner, from the Russkii
Island on the Pacific cost of south-eastern Russia is revised, based on re-examination of the type material.
Although this species, like most described Triassic lingulids, has remained very poorly understood due to
the lack of information on important characters, such as musculature and mantle canals, it has been commonly
recorded in subsequent studies and included in attempts at understanding the patterns of extinction
and recovery at around the Permian–Triassic boundary. Linguliform brachiopods are some of the notable
survivors of this significant mass extinction event. Lingula borealis has previously been referred to Lingularia
and provisionally synonymised with Lingularia similis Biernat & Emig. Here, it is shown that it
differs from Lingularia similis mainly in characters of mantle canals, musculature and most importantly
in details of the pedicle nerve impression. In Lingularia borealis, the impression of the pedicle nerve is
symmetrical and goes almost straight between the individual ventral umbonal muscle scars, whereas in
Lingularia similis it is asymmetrically positioned towards the smaller left component of the ventral umbonal
muscle scar. Shell structures and details of preserved ontogenies have also proven to be important
for the discrimination of lingulid taxa, but cannot be provided from the types of Lingularia borealis.
Despite many major advances in recent years, three key challenges remain in bringing clarity to t... more Despite many major advances in recent years, three key challenges remain in bringing clarity to the early history of the phylum: (1) identifying the origin, morphology and life modes of the first brachiopods; (2) understanding the relationships of the major groups to each other and higher sister taxa; and (3) unravelling the roles of the Cambrian and Ordovician radiations that set the agenda for much of subsequent brachiopod evolution. Since some 95% of all brachiopod taxa are extinct, the fossil record is the primary source of data to frame and test models for the evolution of the phylum. The acquisition of new, and the redescription of existing faunas, in precise spatial and temporal frameworks, using new and well-established analytical and investigative techniques, are as important as ever.
Palaeogeography, Palaeoclimatology, Palaeoecology, 2011
High-latitude Hirnantian diamictites (Dargaz Formation) and lower-Silurian kerogenous black shale... more High-latitude Hirnantian diamictites (Dargaz Formation) and lower-Silurian kerogenous black shales (Sarchahan Formation) are locally exposed in the Zagros Mountains. The glaciogenic Dargaz deposits consist of three progradational/retrogradational cycles, each potentially controlled by the regional advance and retreat of the Hirnantian ice sheet. Glacial incisions of sandstone packages change laterally from simple planar to high-relief (b 40 m deep) scalloped truncating surfaces that join laterally forming complex polyphase unconformities that scour into the underlying Seyahou Formation. The glaciated source area was to the present-day west, in the region of the Arabian Shield, where numerous tunnel valleys have been reported. Based on a study of palynomorphs and graptolites, the glaciomarine Dargaz diamictites are dated as Hirnantian, whereas the youngest Sarchahan black shales are diachronous throughout the Zagros, ranging from the Hirnantian persculptus to the earliest Aeronian (Llandovery) triangulatus zones. The diachronism is related to onlapping geometries capping an inherited glaciogenic palaeorelief that preserved different depth incisions and source areas. Our data suggest the presence of Hirnantian satellite ice caps adjacent the Zagros margin of Arabia and allow us to fill a gap in the present knowledge of the peripheral extension of the Late Ordovician ice sheet.
Earth and Environmental Science Transactions of the Royal Society of Edinburgh, 2014
Brachiopods are among the most common components of the Late Ordovician benthic faunal assemblage... more Brachiopods are among the most common components of the Late Ordovician benthic faunal assemblages recorded in the Faraghan Mountains, Zagros Ranges, Iran. A total of 19 species referable to 16 genera are identified, including seven new species; namely Drabovia elegans, Hibernodonta bonehensis, Hedstroemina zakeenensis, Jezercia faraghani, Protomendacella multicostata, Tafilaltia dargazensis and Tafilaltia seyahouensis. Reported brachiopod assemblages are oligotaxic (2-3 species per assemblage) to monotaxic. The only exception is the medium diversity Aegiromena-Hedstroemina Association, with up to ten species, which occurs at the lower part of the A. nigerica Zone. Low diversity patterns were probably controlled by the palaeogeographical position of the region in high southern latitudes throughout the Ordovician. Paterula sp. and Iranospirifer sp. are the only brachiopods documented from the Silurian (Llandovery) Sarchahan Formation. This paper gives the first detailed report of shelly fossils from the Llandovery 'hot shale' of the Arabian margin of Gondwana. Most of the Katian genera, and many of their species, are shared with neighbouring high-to mid-latitude peri-Gondwanan margins,
This paper reviews the global biogeography and affinities of the Bradoriida, a group of Cambrian–... more This paper reviews the global biogeography and affinities of the Bradoriida, a group of Cambrian–early Ordovician arthropods. Bradoriida appear in the fossil record during the early Cambrian, just prior to the earliest trilobite faunas. Seven families may form a natural (monophyletic) group of Bradoriida sensu stricto, comprising Cambriidae, Kunmingellidae, Comptalutidae, Bradoriidae, Hipponicharionidae, Beyrichonidae and Svealutidae. Amongst the Bradoriida sensu lato, some forms that lie outside these families have carapace designs that suggest an ostracod affinity, particularly Altajanella and Vojbokalina. Bradoriida formed a major element of the 'Cambrian evolutionary fauna' and are components of the Chengjiang, Burgess Shale, and Buen Formation Lagerstätten. Bradoriida achieved global distribution from the Atdabanian (early Cambrian). Their diversity peaked during the early and middle Cambrian, with highest diversity at the species and genus level amongst the palaeo-tropical faunas of the South China (17 genera) and east Gondwana palaeocontinental regions (23 genera). By contrast Laurentian faunas were of much lower diversity (10 genera for the whole Cambrian). Bradoriid diversity declined rapidly from the latest middle Cambrian, a trend that may be related to the major extinction of trilobites at the base of the late Cambrian. The youngest Bradoriida comprise a few, rare Ordovician forms. Bradoriids appear to have occupied well-oxygenated marine shelf facies. The biogeographical patterns of early and middle Cambrian Bradoriida suggest climatic control on their distribution (temperate and tropical faunas), together with palaeogeographical constraints that also reflect trilobite provinciality. Kunmingellids and comptalutids were restricted to palaeo-tropical/subtropical sites, but migrated between South China, Siberia and eastern Gondwana palaeocontinents. They are absent from the mid-and high latitude faunas of the western Gondwana, Avalonia and Baltica palaeocontinental areas that were dominated by hipponicharionids, beyrichonids and Bradoriidae. The Laurentia palaeocontinent was isolated from the main zones of bradoriid diversity, but its faunas include a number of early and middle Cambrian Bradoriidae (Indota, Bradoria, Walcottella), and the region was colonised by cosmopolitan cambriids during the early Cambrian and by supposed pelagic svealutids (Liangshanella and Anabarochilina) during the middle Cambrian. The genera Walcottella, Dielymella and Bullaluta were endemic to Laurentia. One species of Anabarochilina that possibly dwelt near the sea-surface achieved an equatorial to high southern latitude (70° S) distribution during the late middle Cambrian (Lejopyge laevigata Biozone), perhaps reflecting a reduced latitudinal temperature gradient for near surface ocean waters.
The Tremadocian (Early Ordovician) is currently considered a time span of greenhouse conditions w... more The Tremadocian (Early Ordovician) is currently considered a time span of greenhouse conditions with tropical water surface temperature estimates, interpolated from oxygen isotopes, approaching 40°C. In the high-latitude Baltoscandian Basin, these data are in contrast with the discovery of glendonite, a pseudomorph of ikaite (CaCO3•6H2O) and valuable indicator of near-freezing bottom-water conditions. The massive precipitation of this climatically sensitive mineral is associated with transgressive conditions and high organic productivity. Surprisingly, the precipitation of glendonite is contemporaneous with the record of conodonts displaying low δ18O values, which would suggest high temperatures (>40°C) in the water column. Therefore, the early Tremadocian sediments of Baltoscandia contain both “greenhouse” pelagic signals and near-freezing substrate indicators. This apparent paradox suggests both the influence of isotopically depleted freshwater yielded by fluvial systems, and the onset of sharp thermal stratification patterns in a semi-closed basin, which should have played an important role in moderating subpolar climates and reducing latitudinal gradients.