Papers by Philippe Steemans
Ameghiniana, Jan 1, 2007
... has been reported from the uppermost Furnas Formation, in the Paraná Basin (PISA locality,Din... more ... has been reported from the uppermost Furnas Formation, in the Paraná Basin (PISA locality,Dino and Rodrigues, 1995), considered as ... 1999, 2000), which thus seems to be younger than levels analysed from the Villavicencio Formation in the Precordillera of Mendoza. ...
Geologica Belgica, 2021
Accurate palyno-analysis by S. Loboziak (from 1980 to 1983) of 28 samples from the Upper Givetian... more Accurate palyno-analysis by S. Loboziak (from 1980 to 1983) of 28 samples from the Upper Givetian to the Middle Frasnian Blacourt, Beaulieu and Ferques Formations and of 44 samples of the Upper Frasnian to the Lower Famennian Hydrequent Formation are re-evaluated. Chelinospora concinna, Verrucosisporites bulliferus, Cirratriradites jekhowskyi, Lophozonotriletes media first occurrences are major criteria for Lower and Middle Frasnian, well calibrated by conodonts. Cymbosporites acanthaceus, Rugospora bricei, Grandispora gracilis, Diducites plicabilis, Corbulispora vimineus first occurrences allow to subdivide the Upper Frasnian where conodonts are poorly present. Samarisporites triangulatus versus Auroraspora pseudocrista taxonomy and stratigraphic significance are discussed. The reconnaissance borehole Nieuwkerke-De Seule (95W152), near the limit of the Upper Palaeozoic subcrop on the Brabant Massif (West Flanders, Belgium, 75 km east of the Boulonnais), which has intersected conodo...
Brazilian Paleofloras, 2019
To Philippe Gerrienne, You were my friend and my colleague, and you were also the friend of a lot... more To Philippe Gerrienne, You were my friend and my colleague, and you were also the friend of a lot of people. You were one of the most brilliant palaeobotanists of the Devonian. Worldly recognized and respected by all of your colleagues. Our discipline has lost a famous scientist, and more importantly, we have lost a man of heart. Philippe passed away on June 29th 2019-Philippe Steemans.
Archaeological assemblage 1A at Scladina Cave, Belgium has yielded artefacts from a Middle Palaeo... more Archaeological assemblage 1A at Scladina Cave, Belgium has yielded artefacts from a Middle Palaeolithic occupation dating to between 40,000 and 37,000 BP. Fifty-two fragments of a black, friable rock with a black streak were found in association with approximately 200 burned bone fragments and several thousand lithic artefacts. This black material (silica-rich graphite-bearing siltstone) is interpreted as a pigment brought to the site by Neandertals. This is a very unique dis- covery, as European archaeological research has so far only recorded black pigments composed of manganese oxides from the Middle Palaeolithic. The pigment was analysed by petrography, X-Ray diffraction (XRD), X-Ray fluorescence (XRF), inductively coupled plasma mass spectrometry (ICP-MS), and Raman microspectrometry. Raman microspectrometry is a non-destructive method able to distinguish the attributes of black sili- ceous materials that originate from different tectono-sedimentary contexts. By measuring the d...
Review of Palaeobotany and Palynology, 2021
The Rhynie chert (Aberdeenshire, Scotland, UK) plant Horneophyton lignieri is likely one of the m... more The Rhynie chert (Aberdeenshire, Scotland, UK) plant Horneophyton lignieri is likely one of the most studied elements of Lower Devonian floras considering both macro and microremains. Intriguingly, while larger plant fragments are exceptionally fossilized, in situ spores are not necessarily well-preserved in the chert: they are dark brown and intensively torn overall. However, spore masses are often dominated by single spores, which can be taxonomically attributed. Mainly, Horneophyton spores have been described as belonging to Apiculiretusispora type and Emphanisporites cf. decoratus, this last one being currently accepted in general. Here, we document new Horneophyton spore morphologies, that are sometimes quite different. Such morphologies include, but are not restricted to, Ambitisporites, Dibolisporites or Retusotriletes. All these observed spore morphotypes belong to the same palaeobiological entity, as they have been found in the same parent plant. These findings show that the sporangia of a same plant species may deliver diverse taxa of coeval isolated spores. But most importantly, if these spores are found in sediments, they would most probably be identified as different dispersed miospore taxa. This highlights that caution is needed when comparing plant diversity with the dispersed spore fossil record. Moreover, we confirm the presence of Emphanisporites decoratus inside most of the sporangia of Horneophyton lignieri, and its high morphological variability. We further discuss the role of the different states of maturation and preservation, as well as taphonomy-induced features, on observed spore diversity.
Review of Palaeobotany and Palynology, 2021
Abstract Palynological investigations have been carried out on samples from the Upper Devonian Ho... more Abstract Palynological investigations have been carried out on samples from the Upper Devonian Hongguleleng Formation of Western Junggar, Xinjiang, NW China. In total, 26 miospore species belonging to 19 genera and 28 acritarch species assigned to 19 genera have been recognized from the lower member of the Hongguleleng Fm. in the Bulongguoer section. The palynofloral assemblages, in particular the miospore taxa, are similar to those from the eastern European early Famennian Corbulispora vimineus–Geminospora vasjamica (VV) and Cyrtospora cristifer–Diaphanospora zadonica (CZ) miospore biozones, albeit quantitatively and qualitatively depauperate. The miospore assemblage zone is also consistent with the previous zonal schemes in light of brachiopod and conodont fauna assemblages, as well as carbon isotope geochemistry, that indicates a correspondence to the Palmatolepis crepida conodont Biozone. Part of the earliest Famennian Corbulispora vimineus–Geminospora vasjamica (VV) (more or less equivalent to the Palmatolepis triangularis conodont Biozone) miospore Biozone is most likely to be missing in the Hongguleleng Fm. of the Bulongguoer section. The palynostratigraphy and sedimentary sequence in Western Junggar are very similar to those from some other regions of western and eastern Europe, which increases the knowledge of the evolution of the paleoclimate, paleogeography and regional sedimentary environment of the Central Asian Orogenic Belt (CAOB), Eastern European Platform, and Laurussia.
Review of Palaeobotany and Palynology, 2021
Gondwanan floras of Late Devonian age are poorly known. In Australia, the rare studies that have ... more Gondwanan floras of Late Devonian age are poorly known. In Australia, the rare studies that have been published on Late Devonian plants are old and need reinvestigation. This paper is an account of the plant macro-and microremains found in the Mandowa Mudstone at Barraba, New South Wales. According to the miospores, plants are late to latest Famennian in age. The record of anatomically preserved specimens is diversified, with nine taxa assigned to the Lycopsida, Cladoxylopsida, Iridopteridales and Archaeopteridales. One specimen is referrable to the spermatophytes. Several taxa are specific to Barraba, i.e., the lycopsid genera Cymastrobus and Lycaugea, the iridopteridalean genus Keraphyton, the cladoxylopsid species Polyxylon australe, and possibly a plant represented by a large Hierogramma branch showing exarch protoxylem strands. The adpression record is dominated by axes of the cosmopolitan lycopsid genus Leptophloeum. It also includes specimens interpreted as seed plants such as a possible ovule resembling Pseudosporogonites, and two types of foliage differing by their petiole width. One of this foliage consists of delicate fronds broadly comparable to those of Cosmosperma. The closest flora from Barraba is the late Famennian-earliest Tournaisian flora of the New Albany Shale in eastern USA, suggesting floral connexion and comparable environmental conditions between Northern Gondwana and Southern Laurussia.
Geologica Belgica, 2020
It is revealed that the lowest 1010 m of the Saint-Ghislain borehole (-4393 to -5403 m), of which... more It is revealed that the lowest 1010 m of the Saint-Ghislain borehole (-4393 to -5403 m), of which cuttings are available, constitutes a crucial source of information to investigate, amongst others, the deep geothermal potential within the Brabant Parautochthon, underlying the Mons Basin, Hainaut. The lithological succession of this interval was reconstructed based mainly on visual analysis and calcimetry of 852 cutting samples as well as four core samples. Additionally, palynological, magnetic susceptibility and X-ray diffraction analyses were conducted in order to complement the dataset. The lower section of the investigated borehole sequence mainly consists of grey calcareous shale while the middle section is dominated by blue-grey shaly limestone and the upper section is mainly composed of green shale. Palynomorphs found at -5261 m suggest an uppermost Givetian–Lower Frasnian age. A new lithostratigraphical interpretation of the deepest part of the Saint-Ghislain borehole is prop...
Revue de Micropaléontologie, 2017
Core samples from the QSIM-801 water well, drilled in central Saudi Arabia, cover a 93-feet inter... more Core samples from the QSIM-801 water well, drilled in central Saudi Arabia, cover a 93-feet interval spanning the transition between the Sajir Member of the Saq Formation, that consists mainly of sandstones of tidal sand flat environment, and the Hanadir Member of the Qasim Formation, characterized by argillaceous graptolitic mudstones, corresponding to a tidal delta front. The samples contain abundant, exceptionally well-preserved and diverse palynomorphs which include cryptospores, acritarchs, chitinozoans, cuticle-like fragments, and other problematic organic-walled microfossils. The studied interval is biostratigraphically well constrained by the presence of chitinozoans of the formosa and pissotensis Zones of late early to late Darriwilian age (Middle Ordovician), in the uppermost Saq Formation and Hanadir Member. The biostratigraphic age of the Sajir Member considered to span the Dapingian-Darriwilian boundary is re-discussed with results herein. The uppermost part of the Sajir Member yielded the ichnofossil Phycodes fusiforme. Acritarch assemblages from the Sajir Member of the Saq Formation are poorly diversified, dominated by sphaeromorphs. More diverse assemblages of acritarchs, associated with enigmatic forms, occur in the Hanadir Member of the Qasim Formation. The contact between the two formations, and the transition between the palynomorph assemblages, are sharp, suggesting a stratigraphic hiatus. The quantitative analysis allows to discuss the paleoenvironmental changes and possibly climatic changes and the hypothesis of ice house conditions during this period. Among the diagnostic acritarch taxa observed, are Frankea Breviuscula, F. longiuscula, Baltisphaeridium ternatum, Dasydorus cirritus, Dicrodiacrodium ancoriforme, Poikilofusa ciliaris, Pterospermopsis colbathii and Uncinisphaera fusticula. These are associated to other typical forms known to range across the Lower-Middle Ordovician boundary, such as Aremoricanium rigaudae, Aureotesta clathrata, Barakella fortunata, B. rara, Baltisphaeridium klabavense, Glaucotesta latiramosa and some Striatotheca spp. Galeate and peteinoids acritarchs are also well represented, as well as tiny forms of the ultraplanctonic size class. Three new species are proposed: Frankea longiuscula var. darriwilense, Micrhystridium regulum, and Tyrannus proteus. Repeated occurrences throughout the section of cryptospores, problematic microfossils such as organic filaments, cuticle-like tissues, striated and pigmented leiospheres frequently in clusters, are interpreted to reflect recurrent terrestrial and freshwater inputs in the depositional environment. Single-specimen, high-resolution analyses using Confocal Laser Scanning Microscopy on the enigmatic form Tyrannus proteus nov. sp. show fluorescence emission spectra and microstructural properties significantly different from those of typical marine acritarchs from the same levels. Résumé Les échantillons du sondage QSIM-801, foré dans la partie centrale d'Arabie Saoudite pour des recherches d'eau, couvrent un intervalle de 93 pieds, à la transition entre le Membre Sajir de la Formation Saq, avec essentiellement des grès, caractéristiques d'une zone intertidale sableuse, et le Membre Hanadir de la Formation Qasim, qui consiste en boues argileuses à graptolites de front de delta. Dans ces échantillons, les palynomorphes sont abondants et bien conservés, comprenant des cryptospores, des acritarches, des chitinozoaires, des fragments de
Journal of South American Earth Sciences, 2018
Marine and terrestrial palynomorphs from the Loma de los Piojos section of the Precordillera Basi... more Marine and terrestrial palynomorphs from the Loma de los Piojos section of the Precordillera Basin, western Argentina, were analyzed. The studied section embraces the upper part of the Lower Devonian Talacasto Formation and the whole Lower-Middle? Devonian Punta Negra Formation, which constitute the Gualilán Group. Terrestrial palynomorphs dominate the Lower Devonian Talacasto Formation whereas marine palynomorphs dominate the Lower-Middle? Devonian Punta Negra Formation.
Revue de Micropaléontologie, 2017
The QSIM-801 well from Central Saudi Arabia contains beds transitional between the Sajir Member o... more The QSIM-801 well from Central Saudi Arabia contains beds transitional between the Sajir Member of the Saq Formation and the Hanadir Member of the Qasim Formation. Core samples from these beds yielded rich assemblages of well-preserved palynomorphs of low thermal maturity. They are dominated by marine forms (acritarchs, chitinozoans and scolecodonts) but also include relatively abundant and diverse terrestrial forms (cryptospores and dispersed phytodebris), especially in samples from the upper part of the Sajir Member. The cryptospore assemblage is taxonomically consistent with other Middle Ordovician assemblages previously reported from Saudi Arabia, and is concordant with the late Dapingian to early Darriwillian (Llanvirn) age of the Sajir-Hanadir transitional beds, as suggested by palynological evidence (i.e., presence of Siphonochitina formosa and Linochitina pissotensis chitinozoan zones in the basal Hanadir). It includes a variety of monads and permanent dyads and tetrads, which are often characterized by well-developed surface ornamentation such as microgranulation, as well as, in some instances, by thick walls displaying distinct layering.
Historical Biology, 2015
Abstract A new well-preserved spore assemblage has been discovered from the Lower Devonian Noguer... more Abstract A new well-preserved spore assemblage has been discovered from the Lower Devonian Nogueras Formation of Mezquita de Loscos (Teruel Province, north-eastern Spain). The palynoflora includes 34 spore species belonging to 20 genera, among which 14 are new for the locality, e.g. Apiculiretusispora, Brochotriletes, Cirratriradites, Iberoespora, Knoxisporites and Verrucosisporites. The assemblage is mainly composed of trilete spores, while tripapillate and monolete forms are also observed. An early Pragian age is suggested for the fossil site. Specimens of Latosporites ovalis, a species previously well-documented only from the late Pragian–Emsian of Saudi Arabia and Brazil, are found in this assemblage and represent to date the earliest known occurrence of this species. Besides the description of the palynoflora, we also provide here a synthesis of the plant-bearing localities of the study area.
Review of Palaeobotany and Palynology, 2011
Abstract A restudy of Devonian palynological assemblages of samples from the A1-69 borehole, dril... more Abstract A restudy of Devonian palynological assemblages of samples from the A1-69 borehole, drilled in the Ghadamis Basin, western Libya, North Africa has led to the discovery of numerous well-preserved megaspores amongst abundant miospores, rare acritarchs and rare chitinozoans. Thirteen samples from base to top, 1496 ft (456 m) up to 965 ft (294 m), contain the richest Devonian megaspore assemblages from northwestern Gondwana. The section is dated by a rich diverse miospore assemblage indicating the presence of the ...
Review of Palaeobotany and Palynology, 2019
The present study concerns the palynology (mainly miospores), and geochemistry of the Jaciara sec... more The present study concerns the palynology (mainly miospores), and geochemistry of the Jaciara section, situated 5 km from the town of Jaciara, Mato Grosso, in the Paraná Basin of Brazil. The age of this outcrop is considered to be Early Devonian. A study of the whole assemblage has highlighted a diversified association of miospores. Their distribution throughout the samples is somewhat erratic, which sometimes complicates the determination of the biostratigraphic attribution. However the following markers have been identified: Apiculiretusispora brandtii, Brochotriletes bellatulus, Cymbohilates baqaensis, Cymbosporites asymmetricus, Cymbosporites wellmanii, Devonomonoletes sp. 1 in Breuer and Steemans (2013), Dibolispotites sp. 2 in Breuer and Steemans (2013), Dictyotriletes subgranifer, Distaverrucosisporites steemansii, Latosporites ovalis, Scylaspora costulosa, Verrucosisporites nafudensis, Verrucosisporites onustus, Verruciosisporites stictus, Zonotriletes brevivelatus, and Zonotriletes simplicissimus. The finding of these miospores allowed recognition of the following biozones established in Saudi Arabia: the papillensis-baqaenisis Biozone, Pragian in age; the ovalis-biornatus Biozone (ovalis, milleri, asymmetricus subzones), late Pragian to early Emsian in age; and possibly the lindlarensis-sextantii Biozone, middle Emsian in age. The presence of many taxa in common with other Gondwanan basins, particularly those from Saudi Arabia, North Africa and South America, corroborates the paleogeographical relationship between different regions of Gondwana, even between those located in very different paleolatitudes. New geochemical analyses were also performed and add more information toward the understanding of the local paleoenvironmental evolution.
Uploads
Papers by Philippe Steemans