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Hilary A. Mcmanus - One of the best experts on this subject based on the ideXlab platform.
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organellar phylogenomics inform systematics in the green algal family hydrodictyaceae chlorophyceae and provide clues to the complex evolutionary history of plastid genomes in the green algal tree of life
American Journal of Botany, 2018Co-Authors: Hilary A. Mcmanus, Louise A. Lewis, Karolina Fucikova, Paul O Lewis, Kenneth G. KarolAbstract:PREMISE OF THE STUDY Phylogenomic analyses across the green algae are resolving relationships at the class, order, and family levels and highlighting dynamic patterns of evolution in organellar genomes. Here we present a within-family phylogenomic study to resolve genera and species relationships in the family Hydrodictyaceae (Chlorophyceae), for which poor resolution in previous phylogenetic studies, along with divergent morphological traits, have precluded taxonomic revisions. METHODS Complete plastome sequences and mitochondrial protein-coding gene sequences were acquired from representatives of the Hydrodictyaceae using next-generation sequencing methods. Plastomes were characterized, and gene order and content were compared with plastomes spanning the Sphaeropleales. Single-gene and concatenated-gene phylogenetic analyses of plastid and mitochondrial genes were performed. KEY RESULTS The Hydrodictyaceae contain the largest sphaeroplealean plastomes thus far fully sequenced. Conservation of plastome gene order within Hydrodictyaceae is striking compared with more dynamic patterns revealed across Sphaeropleales. Phylogenetic analyses resolve Hydrodictyon sister to a monophyletic Pediastrum, though the morphologically distinct P. angulosum and P. duplex continue to be polyphyletic. Analyses of plastid data supported the neochloridacean genus Chlorotetraedron as sister to Hydrodictyaceae, while conflicting signal was found in the mitochondrial data. CONCLUSIONS A phylogenomic approach resolved within-family relationships not obtainable with previous phylogenetic analyses. Denser taxon sampling across Sphaeropleales is necessary to capture patterns in plastome evolution, and further taxa and studies are needed to fully resolve the sister lineage to Hydrodictyaceae and polyphyly of Pediastrum angulosum and P. duplex.
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Plastomes of the green algae Hydrodictyon reticulatum and Pediastrum duplex (Sphaeropleales, Chlorophyceae)
PeerJ, 2017Co-Authors: Hilary A. Mcmanus, Daniel J. Sanchez, Kenneth G. KarolAbstract:Background Comparative studies of chloroplast genomes (plastomes) across the Chlorophyceae are revealing dynamic patterns of size variation, gene content, and genome rearrangements. Phylogenomic analyses are improving resolution of relationships, and uncovering novel lineages as new plastomes continue to be characterized. To gain further insight into the evolution of the chlorophyte plastome and increase the number of representative plastomes for the Sphaeropleales, this study presents two fully sequenced plastomes from the green algal family Hydrodictyaceae (Sphaeropleales, Chlorophyceae), one from Hydrodictyon reticulatum and the other from Pediastrum duplex. Methods Genomic DNA from Hydrodictyon reticulatum and Pediastrum duplex was subjected to Illumina paired-end sequencing and the complete plastomes were assembled for each. Plastome size and gene content were characterized and compared with other plastomes from the Sphaeropleales. Homology searches using BLASTX were used to characterize introns and open reading frames (orfs) ≥ 300 bp. A phylogenetic analysis of gene order across the Sphaeropleales was performed. Results The plastome of Hydrodictyon reticulatum is 225,641 bp and Pediastrum duplex is 232,554 bp. The plastome structure and gene order of H. reticulatum and P. duplex are more similar to each other than to other members of the Sphaeropleales. Numerous unique open reading frames are found in both plastomes and the plastome of P. duplex contains putative viral protein genes, not found in other Sphaeropleales plastomes. Gene order analyses support the monophyly of the Hydrodictyaceae and their sister relationship to the Neochloridaceae. Discussion The complete plastomes of Hydrodictyon reticulatum and Pediastrum duplex, representing the largest of the Sphaeropleales sequenced thus far, once again highlight the variability in size, architecture, gene order and content across the Chlorophyceae. Novel intron insertion sites and unique orfs indicate recent, independent invasions into each plastome, a hypothesis testable with an expanded plastome investigation within the Hydrodictyaceae.
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testing the boundaries of the green algal species Pediastrum alternans chlorophyceae using conventional geometric morphometric and phylogenetic methods
Phycologia, 2016Co-Authors: Joanna Lenarczyk, Hilary A. McmanusAbstract:Abstract: This article focuses on a detailed morphological and molecular analysis of the microscopic green alga Pediastrum alternans as it exhibits ambiguous morphology, questionable phylogenetic position and scattered distribution. The species, originally described from lakes close to the Baltic Sea in Denmark, was recently renamed PseudoPediastrum alternans based on rDNA sequencing of one culture from Namibia. In the present study, the African culture was morphologically and genetically compared with a culture identified as Ps. alternans from a coastal lake from northern Poland and a culture of Ps. boryanum var. longicorne from southern Poland. Conventional measurements, statistical and geometric morphometric analyses of the number of cells in coenobia, cell shape and size and wall ornamentation showed significant differences in the morphology of the three cultures. The analyses supported the phylogenetic distinction of the cultures based on rDNA and chloroplast DNA sequencing. Cultures of Pseudopediast...
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molecular phylogenetic relationships in the freshwater family hydrodictyaceae sphaeropleales chlorophyceae with an emphasis on Pediastrum duplex 1
Journal of Phycology, 2011Co-Authors: Hilary A. Mcmanus, Louise A. LewisAbstract:The freshwater green algal family Hydrodictyaceae (Sphaeropleales, Chlorophyta) has traditionally consisted of four coenobial genera, Pediastrum Meyen 1829, Hydrodictyon Roth 1797, Sorastrum Kutzing 1845, and Euastropsis Lagerheim1894. Two recent molecular phylogenetic studies demonstrated the need for reevaluation of the generic and species boundaries in this morphology-rich family. This study expands the previous work to include phylogenetic analyses of 103 ingroup isolates representing North America, Europe, and Australia, with an emphasis on the common and geographically widespread species Pediastrum duplex. Nucleotide sequence data were collected from the nuclear LSU (26S rDNA) and the chloroplast RUBISCO LSU (rbcL) genes, totaling >3,000 aligned characters. The 26S and rbcL data sets were analyzed using maximum-likelihood (ML) and Bayesian phylogenetic methods. In addition, SEM was used to examine the wall morphology of a majority of the isolates. The results supported previous indications that the P. duplex Meyen 1829 morphotype is nonmonophyletic and resolved some previously ambiguous relationships recovered in earlier phylogenetic estimations using fewer isolates. These new data allowed testing of the recent taxonomic revisions of the family that split Pediastrum into five genera. Some of the previous revisions by Buchheim et al. (2005) were well supported (erection of Stauridium and Monactinus), while others were not (Pediastrum, PseudoPediastrum, ParaPediastrum).
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distinguishing multiple lineages of Pediastrum duplex with morphometrics and a proposal for lacunastrum gen nov 1
Journal of Phycology, 2011Co-Authors: Hilary A. Mcmanus, Louise A. Lewis, Eric T SchultzAbstract:Accurately defining species boundaries in the green algae (Chlorophyta) is integral for studies of biodiversity and conservation, water-quality assessments, and the use of particular species as paleoindicators. Recent molecular phylogenetic and SEM analyses of the family Hydrodictyaceae (Chlorophyta) resolved three phylogenetic lineages of isolates with the Pediastrum duplex Meyen 1829 phenotype. The present study employed analyses of cell shape and cell wall ultrastructure to determine if the three lineages possessing the P. duplex morphotype were distinguishable. Only one of the groups, containing isolates with the P. duplex var. gracillimum West et G. S. West phenotype, was shown to be morphologically distinct from the other two P. duplex groups. The erection of a new genus, Lacunastrum, is proposed to recognize this group as a separate taxon.
Ahmed Mansour - One of the best experts on this subject based on the ideXlab platform.
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reply to the comment of anan et al on palynological palaeoenvironmental and sequence stratigraphical analyses of a turonian coniacian sequence beni suef basin eastern desert egypt implication of Pediastrum rhythmic signature by tahoun et al 2017 marine and petroleum geology 88 871 887
Marine and Petroleum Geology, 2018Co-Authors: Sameh S Tahoun, Amr S Deaf, Ahmed MansourAbstract:Abstract Herein, we reply to the allegations made by Anan et al. (2018) who claimed that the rhythmic signature of Pediastrum originally recorded and interpreted for the first time by (Tahoun et al., 2017), is a simulation of the work of El Atfy et al. (2017). This is not possible because we submitted our manuscript (which comes from an earlier version previously submitted to JMPG) almost simultaneously with the online publication of El Atfy et al. (2017); therefore, we had no chance to incorporate their work. Anan et al. (2018) raised such claims, because we provided scientific criticism to El Atfy et al. (2017) and did not follow their work blindly. Moreover, our work has different aims and approaches with respect to those used by El Atfy et al. (2017). Our main idea was to study and explain how the vertical cyclic signature of Pediastrum is connected to sea level cyclicity and to use this vertical stratigraphic signature in paleoenvironmental and sequence stratigraphic interpretation. This aim was not tackled before by Brenac and Richards (2001) and El Atfy et al. (2017). Moreover, our work was based on palynological, geophysical and lithologic data, not on mineralogical data as made by El Atfy et al., 2017). In our paper (Tahoun et al. (2017) we decided to discuss the work of El Atfy et al. (2017) because they tried to relate Pediastrum to regressive sequence systems. We found their work has several scientific mistakes that would raise much scientific controversy and lead to unsubstantiated conclusions. In our opinion, El Atfy et al. (2017) did not use reliable data and failed to provide proper scientific evidence to their conclusion. Following El Atfy et al. (2017), Anan et al. (2018) related an alleged acme of Pediastrum to regressive systems tracts, without providing any quantitative evidence of the acme and/or making a sequence stratigraphic analysis of their studied sections. Not surprisingly, the failure of Anan et al. (2018) to provide any quantitative data to support their alleged acme reinforces our argument that their study was not based on genuine data. Moreover, Anan et al. (2018) tried to flatten the conclusion made by Tahoun et al. (2017) by underestimating its sounding Pediastrum rhythmic signature-based results. Anan et al. (Op. cit.) also tried to bend the clear fact that our ideas differ from that of El Atfy et al. (2017) to look as it was their own, which is not true. Therefore, we encourage the palynologists community to read critically the work of Tahoun et al. (2017) and the work defended by Anan et al. (2018) and their allegations to confidently scrutinize the aims, data quality, and approaches presented therein to come up with an independent judgment. A detailed reply to allegations and comments of Anan et al. (Op. cit.) are handled in the forthcoming sections.
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palynological palaeoenvironmental and sequence stratigraphical analyses of a turonian coniacian sequence beni suef basin eastern desert egypt implication of Pediastrum rhythmic signature
Marine and Petroleum Geology, 2017Co-Authors: Sameh S Tahoun, Amr S Deaf, Ahmed MansourAbstract:Abstract Sixteen samples from the “E” to “B” members of the Abu Roash Formation encountered in the Beni Suef Basin, Eastern Desert of Egypt were palynologically analyzed for palaeoenvironmental and sequence stratigraphic investigations. The integrated palynofacies and lithofacies analysis of the studied section indicates deposition of five alternating regressive and transgressive sequences in well-oxygenated, proximal shelf settings. The Abu Roash “E” and the upper “D” to the lower “C” members were deposited during pronounced regressive phases in oxic, shallow marginal marine settings. The upper “B” Member was deposited during a recurring regressive phase but of a lower magnitude in oxic, shallow inner neritic conditions. The lower “D” Member was deposited during a minor transgression phase in dysoxic, shallow inner neritic settings. While the upper “C” to the lower “B” section was deposited during a stronger transgressive episode in a relatively deep, inner neritic environment of prominent dysoxic conditions. This interchange in the depositional setting was documented by the pronounced and concurrent, cyclic nature of the freshwater algae, peridinioid dinoflagellate cysts, pteridophyte spores, and reworked sporomorphs with variable intensities. Their increasing and conversely their diminishing trends clearly reflect alternating regressive-transgressive periods of reduced and relatively normal salinity conditions, respectively. Overall, sedimentation of the studied Abu Roash section indicates a recurring rise in sea level, which accentuated during the earliest Santonian time. The analogous peaking in the Pediastrum signals with those of the pteridophyte spores and reworked taxa indicate a good connection between these Pediastrum signals and the pronounced fluviatile influxes of terrigenous sediments during regressive phases. Accordingly, this can be used to identify regressive sequence boundaries and hence the clastic reservoirs. Even with the small counts recorded herein, we believe high ratios of peridinioid/gonyalulacoid dinocysts are significantly paralleled by peaking signals of freshwater algae and regressive sedimentation phases. This must be preliminary documented here. Probably future palynological studies will be able to fully interpret and address this important Pediastrum rhythmic event in different sequence stratigraphic settings. The palynological parameters, age controlled sporomorph marker taxa, lithology, and gamma ray data were used to differentiate the Abu Roash members into three distinctive 3rd order depositional sequences (AR SQ1, AR SQ2, and AR SQ3). These sequences match well with the global stratigraphic sequences Tu 3, Tu 4, and Co 1 and connect the local rise in sea level to the global eustatic sea level rise.
Louise A. Lewis - One of the best experts on this subject based on the ideXlab platform.
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organellar phylogenomics inform systematics in the green algal family hydrodictyaceae chlorophyceae and provide clues to the complex evolutionary history of plastid genomes in the green algal tree of life
American Journal of Botany, 2018Co-Authors: Hilary A. Mcmanus, Louise A. Lewis, Karolina Fucikova, Paul O Lewis, Kenneth G. KarolAbstract:PREMISE OF THE STUDY Phylogenomic analyses across the green algae are resolving relationships at the class, order, and family levels and highlighting dynamic patterns of evolution in organellar genomes. Here we present a within-family phylogenomic study to resolve genera and species relationships in the family Hydrodictyaceae (Chlorophyceae), for which poor resolution in previous phylogenetic studies, along with divergent morphological traits, have precluded taxonomic revisions. METHODS Complete plastome sequences and mitochondrial protein-coding gene sequences were acquired from representatives of the Hydrodictyaceae using next-generation sequencing methods. Plastomes were characterized, and gene order and content were compared with plastomes spanning the Sphaeropleales. Single-gene and concatenated-gene phylogenetic analyses of plastid and mitochondrial genes were performed. KEY RESULTS The Hydrodictyaceae contain the largest sphaeroplealean plastomes thus far fully sequenced. Conservation of plastome gene order within Hydrodictyaceae is striking compared with more dynamic patterns revealed across Sphaeropleales. Phylogenetic analyses resolve Hydrodictyon sister to a monophyletic Pediastrum, though the morphologically distinct P. angulosum and P. duplex continue to be polyphyletic. Analyses of plastid data supported the neochloridacean genus Chlorotetraedron as sister to Hydrodictyaceae, while conflicting signal was found in the mitochondrial data. CONCLUSIONS A phylogenomic approach resolved within-family relationships not obtainable with previous phylogenetic analyses. Denser taxon sampling across Sphaeropleales is necessary to capture patterns in plastome evolution, and further taxa and studies are needed to fully resolve the sister lineage to Hydrodictyaceae and polyphyly of Pediastrum angulosum and P. duplex.
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molecular phylogenetic relationships in the freshwater family hydrodictyaceae sphaeropleales chlorophyceae with an emphasis on Pediastrum duplex 1
Journal of Phycology, 2011Co-Authors: Hilary A. Mcmanus, Louise A. LewisAbstract:The freshwater green algal family Hydrodictyaceae (Sphaeropleales, Chlorophyta) has traditionally consisted of four coenobial genera, Pediastrum Meyen 1829, Hydrodictyon Roth 1797, Sorastrum Kutzing 1845, and Euastropsis Lagerheim1894. Two recent molecular phylogenetic studies demonstrated the need for reevaluation of the generic and species boundaries in this morphology-rich family. This study expands the previous work to include phylogenetic analyses of 103 ingroup isolates representing North America, Europe, and Australia, with an emphasis on the common and geographically widespread species Pediastrum duplex. Nucleotide sequence data were collected from the nuclear LSU (26S rDNA) and the chloroplast RUBISCO LSU (rbcL) genes, totaling >3,000 aligned characters. The 26S and rbcL data sets were analyzed using maximum-likelihood (ML) and Bayesian phylogenetic methods. In addition, SEM was used to examine the wall morphology of a majority of the isolates. The results supported previous indications that the P. duplex Meyen 1829 morphotype is nonmonophyletic and resolved some previously ambiguous relationships recovered in earlier phylogenetic estimations using fewer isolates. These new data allowed testing of the recent taxonomic revisions of the family that split Pediastrum into five genera. Some of the previous revisions by Buchheim et al. (2005) were well supported (erection of Stauridium and Monactinus), while others were not (Pediastrum, PseudoPediastrum, ParaPediastrum).
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distinguishing multiple lineages of Pediastrum duplex with morphometrics and a proposal for lacunastrum gen nov 1
Journal of Phycology, 2011Co-Authors: Hilary A. Mcmanus, Louise A. Lewis, Eric T SchultzAbstract:Accurately defining species boundaries in the green algae (Chlorophyta) is integral for studies of biodiversity and conservation, water-quality assessments, and the use of particular species as paleoindicators. Recent molecular phylogenetic and SEM analyses of the family Hydrodictyaceae (Chlorophyta) resolved three phylogenetic lineages of isolates with the Pediastrum duplex Meyen 1829 phenotype. The present study employed analyses of cell shape and cell wall ultrastructure to determine if the three lineages possessing the P. duplex morphotype were distinguishable. Only one of the groups, containing isolates with the P. duplex var. gracillimum West et G. S. West phenotype, was shown to be morphologically distinct from the other two P. duplex groups. The erection of a new genus, Lacunastrum, is proposed to recognize this group as a separate taxon.
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120 exploration of morphological variation within the genus Pediastrum meyen 1829 chlorophyceae chlorophyta
Journal of Phycology, 2003Co-Authors: Hilary A. Mcmanus, Louise A. LewisAbstract:Monographic works on the green algal genus, Pediastrum Meyen 1829 (Chlorophyceae, Chlorophyta), have described species, varieties and forms based on such characteristics as the size and shape of the marginal cells, pattern of cell wall sculpturing and extent of cell wall sculpturing. Depending on the author, the number of taxa assigned to the genus Pediastrum varies. Due to the lack of quantitative value to these characteristics, it has been difficult for other researchers to assign appropriate taxonomy to wild isolates. A molecular phylogeny including multiple strains from both culture collections and wild samples confirms relationships found by previous molecular studies on fewer taxa, in which the family Hydrodictyaceae forms a monophyletic group within the Sphaeropleales, and that the genera Hydrodictyon and Sorastrum are derived from Pediastrum. Hydrodicyton forms a monophyletic clade and consists of three species, H. reticulatum, H. africanum, and H. patenaeforme. Multiple isolates of H. reticulatum reveal little genetic variation between different geographic localities. Inclusion of wild isolates permits a more thorough exploration of morphological variation within the genus Pediastrum, and what characters may be taxonomically informative, particularly in the species P. boryanum and P. duplex. Wild isolates sampled from different areas also offers information regarding geographic variation and potential morphological convergence.
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Phylogenetic Relationships Among Pediastrum sPP. and Hydrodictyon sPP.
Journal of Phycology, 2002Co-Authors: Hilary A. Mcmanus, Louise A. LewisAbstract:Within the class Chlorophyceae, the family Hydrodictyaceae (order Sphaeropleales) consists of taxa that form flat or net-like coenobia and reproduce asexually by way of biflagellated zoospores. Two taxa within this family, Pediastrum and Hydrodictyon, share many features during development, especially the manner of daughter colony formation. The colonies of Pediastrum differ from Hydrodictyon in that growth is planar resulting in two-dimensional colonies, while three-dimensional nets are formed in Hydrodictyon. Studies of the Chlorophyceae using morphological and ultrastructural data, as well as molecular sequence data, have supported the close relationship of Pediastrum and Hydrodictyon and they have remained in the family Hydrodictyaceae throughout major classification revisions. However, in these studies only single species of Pediastrum (P. duplex) and Hydrodictyon (H. reticulatum) were included, therefore the exact relationship of these two taxa could not be explored. Preliminary molecular data from a second species of Pediastrum, P. boryanum, indicate that Hydrodictyon may be derived from Pediastrum. In this analysis, H. reticulatum resolves as sister taxon to P. duplex with P. boryanum the ancestral taxon. Further molecular studies of the family Hydrodictyaceae allow exploration of the relationships between Pediastrum spp. and Hydrodictyon spp., and assist in determining whether they are monophyletic. Preliminary analyses include H. reticulatum and H. africanum and several species of Pediastrum, P. duplex, P. boryanum, P. tetras, P. biradiatum and P. simplex. An understanding of the phylogenetic relationships among the species of Pediastrum and Hydrodictyon will allow a more complete comparison of colony formation.
Sameh S Tahoun - One of the best experts on this subject based on the ideXlab platform.
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reply to the comment of anan et al on palynological palaeoenvironmental and sequence stratigraphical analyses of a turonian coniacian sequence beni suef basin eastern desert egypt implication of Pediastrum rhythmic signature by tahoun et al 2017 marine and petroleum geology 88 871 887
Marine and Petroleum Geology, 2018Co-Authors: Sameh S Tahoun, Amr S Deaf, Ahmed MansourAbstract:Abstract Herein, we reply to the allegations made by Anan et al. (2018) who claimed that the rhythmic signature of Pediastrum originally recorded and interpreted for the first time by (Tahoun et al., 2017), is a simulation of the work of El Atfy et al. (2017). This is not possible because we submitted our manuscript (which comes from an earlier version previously submitted to JMPG) almost simultaneously with the online publication of El Atfy et al. (2017); therefore, we had no chance to incorporate their work. Anan et al. (2018) raised such claims, because we provided scientific criticism to El Atfy et al. (2017) and did not follow their work blindly. Moreover, our work has different aims and approaches with respect to those used by El Atfy et al. (2017). Our main idea was to study and explain how the vertical cyclic signature of Pediastrum is connected to sea level cyclicity and to use this vertical stratigraphic signature in paleoenvironmental and sequence stratigraphic interpretation. This aim was not tackled before by Brenac and Richards (2001) and El Atfy et al. (2017). Moreover, our work was based on palynological, geophysical and lithologic data, not on mineralogical data as made by El Atfy et al., 2017). In our paper (Tahoun et al. (2017) we decided to discuss the work of El Atfy et al. (2017) because they tried to relate Pediastrum to regressive sequence systems. We found their work has several scientific mistakes that would raise much scientific controversy and lead to unsubstantiated conclusions. In our opinion, El Atfy et al. (2017) did not use reliable data and failed to provide proper scientific evidence to their conclusion. Following El Atfy et al. (2017), Anan et al. (2018) related an alleged acme of Pediastrum to regressive systems tracts, without providing any quantitative evidence of the acme and/or making a sequence stratigraphic analysis of their studied sections. Not surprisingly, the failure of Anan et al. (2018) to provide any quantitative data to support their alleged acme reinforces our argument that their study was not based on genuine data. Moreover, Anan et al. (2018) tried to flatten the conclusion made by Tahoun et al. (2017) by underestimating its sounding Pediastrum rhythmic signature-based results. Anan et al. (Op. cit.) also tried to bend the clear fact that our ideas differ from that of El Atfy et al. (2017) to look as it was their own, which is not true. Therefore, we encourage the palynologists community to read critically the work of Tahoun et al. (2017) and the work defended by Anan et al. (2018) and their allegations to confidently scrutinize the aims, data quality, and approaches presented therein to come up with an independent judgment. A detailed reply to allegations and comments of Anan et al. (Op. cit.) are handled in the forthcoming sections.
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palynological palaeoenvironmental and sequence stratigraphical analyses of a turonian coniacian sequence beni suef basin eastern desert egypt implication of Pediastrum rhythmic signature
Marine and Petroleum Geology, 2017Co-Authors: Sameh S Tahoun, Amr S Deaf, Ahmed MansourAbstract:Abstract Sixteen samples from the “E” to “B” members of the Abu Roash Formation encountered in the Beni Suef Basin, Eastern Desert of Egypt were palynologically analyzed for palaeoenvironmental and sequence stratigraphic investigations. The integrated palynofacies and lithofacies analysis of the studied section indicates deposition of five alternating regressive and transgressive sequences in well-oxygenated, proximal shelf settings. The Abu Roash “E” and the upper “D” to the lower “C” members were deposited during pronounced regressive phases in oxic, shallow marginal marine settings. The upper “B” Member was deposited during a recurring regressive phase but of a lower magnitude in oxic, shallow inner neritic conditions. The lower “D” Member was deposited during a minor transgression phase in dysoxic, shallow inner neritic settings. While the upper “C” to the lower “B” section was deposited during a stronger transgressive episode in a relatively deep, inner neritic environment of prominent dysoxic conditions. This interchange in the depositional setting was documented by the pronounced and concurrent, cyclic nature of the freshwater algae, peridinioid dinoflagellate cysts, pteridophyte spores, and reworked sporomorphs with variable intensities. Their increasing and conversely their diminishing trends clearly reflect alternating regressive-transgressive periods of reduced and relatively normal salinity conditions, respectively. Overall, sedimentation of the studied Abu Roash section indicates a recurring rise in sea level, which accentuated during the earliest Santonian time. The analogous peaking in the Pediastrum signals with those of the pteridophyte spores and reworked taxa indicate a good connection between these Pediastrum signals and the pronounced fluviatile influxes of terrigenous sediments during regressive phases. Accordingly, this can be used to identify regressive sequence boundaries and hence the clastic reservoirs. Even with the small counts recorded herein, we believe high ratios of peridinioid/gonyalulacoid dinocysts are significantly paralleled by peaking signals of freshwater algae and regressive sedimentation phases. This must be preliminary documented here. Probably future palynological studies will be able to fully interpret and address this important Pediastrum rhythmic event in different sequence stratigraphic settings. The palynological parameters, age controlled sporomorph marker taxa, lithology, and gamma ray data were used to differentiate the Abu Roash members into three distinctive 3rd order depositional sequences (AR SQ1, AR SQ2, and AR SQ3). These sequences match well with the global stratigraphic sequences Tu 3, Tu 4, and Co 1 and connect the local rise in sea level to the global eustatic sea level rise.
Amr S Deaf - One of the best experts on this subject based on the ideXlab platform.
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reply to the comment of anan et al on palynological palaeoenvironmental and sequence stratigraphical analyses of a turonian coniacian sequence beni suef basin eastern desert egypt implication of Pediastrum rhythmic signature by tahoun et al 2017 marine and petroleum geology 88 871 887
Marine and Petroleum Geology, 2018Co-Authors: Sameh S Tahoun, Amr S Deaf, Ahmed MansourAbstract:Abstract Herein, we reply to the allegations made by Anan et al. (2018) who claimed that the rhythmic signature of Pediastrum originally recorded and interpreted for the first time by (Tahoun et al., 2017), is a simulation of the work of El Atfy et al. (2017). This is not possible because we submitted our manuscript (which comes from an earlier version previously submitted to JMPG) almost simultaneously with the online publication of El Atfy et al. (2017); therefore, we had no chance to incorporate their work. Anan et al. (2018) raised such claims, because we provided scientific criticism to El Atfy et al. (2017) and did not follow their work blindly. Moreover, our work has different aims and approaches with respect to those used by El Atfy et al. (2017). Our main idea was to study and explain how the vertical cyclic signature of Pediastrum is connected to sea level cyclicity and to use this vertical stratigraphic signature in paleoenvironmental and sequence stratigraphic interpretation. This aim was not tackled before by Brenac and Richards (2001) and El Atfy et al. (2017). Moreover, our work was based on palynological, geophysical and lithologic data, not on mineralogical data as made by El Atfy et al., 2017). In our paper (Tahoun et al. (2017) we decided to discuss the work of El Atfy et al. (2017) because they tried to relate Pediastrum to regressive sequence systems. We found their work has several scientific mistakes that would raise much scientific controversy and lead to unsubstantiated conclusions. In our opinion, El Atfy et al. (2017) did not use reliable data and failed to provide proper scientific evidence to their conclusion. Following El Atfy et al. (2017), Anan et al. (2018) related an alleged acme of Pediastrum to regressive systems tracts, without providing any quantitative evidence of the acme and/or making a sequence stratigraphic analysis of their studied sections. Not surprisingly, the failure of Anan et al. (2018) to provide any quantitative data to support their alleged acme reinforces our argument that their study was not based on genuine data. Moreover, Anan et al. (2018) tried to flatten the conclusion made by Tahoun et al. (2017) by underestimating its sounding Pediastrum rhythmic signature-based results. Anan et al. (Op. cit.) also tried to bend the clear fact that our ideas differ from that of El Atfy et al. (2017) to look as it was their own, which is not true. Therefore, we encourage the palynologists community to read critically the work of Tahoun et al. (2017) and the work defended by Anan et al. (2018) and their allegations to confidently scrutinize the aims, data quality, and approaches presented therein to come up with an independent judgment. A detailed reply to allegations and comments of Anan et al. (Op. cit.) are handled in the forthcoming sections.
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palynological palaeoenvironmental and sequence stratigraphical analyses of a turonian coniacian sequence beni suef basin eastern desert egypt implication of Pediastrum rhythmic signature
Marine and Petroleum Geology, 2017Co-Authors: Sameh S Tahoun, Amr S Deaf, Ahmed MansourAbstract:Abstract Sixteen samples from the “E” to “B” members of the Abu Roash Formation encountered in the Beni Suef Basin, Eastern Desert of Egypt were palynologically analyzed for palaeoenvironmental and sequence stratigraphic investigations. The integrated palynofacies and lithofacies analysis of the studied section indicates deposition of five alternating regressive and transgressive sequences in well-oxygenated, proximal shelf settings. The Abu Roash “E” and the upper “D” to the lower “C” members were deposited during pronounced regressive phases in oxic, shallow marginal marine settings. The upper “B” Member was deposited during a recurring regressive phase but of a lower magnitude in oxic, shallow inner neritic conditions. The lower “D” Member was deposited during a minor transgression phase in dysoxic, shallow inner neritic settings. While the upper “C” to the lower “B” section was deposited during a stronger transgressive episode in a relatively deep, inner neritic environment of prominent dysoxic conditions. This interchange in the depositional setting was documented by the pronounced and concurrent, cyclic nature of the freshwater algae, peridinioid dinoflagellate cysts, pteridophyte spores, and reworked sporomorphs with variable intensities. Their increasing and conversely their diminishing trends clearly reflect alternating regressive-transgressive periods of reduced and relatively normal salinity conditions, respectively. Overall, sedimentation of the studied Abu Roash section indicates a recurring rise in sea level, which accentuated during the earliest Santonian time. The analogous peaking in the Pediastrum signals with those of the pteridophyte spores and reworked taxa indicate a good connection between these Pediastrum signals and the pronounced fluviatile influxes of terrigenous sediments during regressive phases. Accordingly, this can be used to identify regressive sequence boundaries and hence the clastic reservoirs. Even with the small counts recorded herein, we believe high ratios of peridinioid/gonyalulacoid dinocysts are significantly paralleled by peaking signals of freshwater algae and regressive sedimentation phases. This must be preliminary documented here. Probably future palynological studies will be able to fully interpret and address this important Pediastrum rhythmic event in different sequence stratigraphic settings. The palynological parameters, age controlled sporomorph marker taxa, lithology, and gamma ray data were used to differentiate the Abu Roash members into three distinctive 3rd order depositional sequences (AR SQ1, AR SQ2, and AR SQ3). These sequences match well with the global stratigraphic sequences Tu 3, Tu 4, and Co 1 and connect the local rise in sea level to the global eustatic sea level rise.