Yuefeng Shen | Université Laval (original) (raw)

Papers by Yuefeng Shen

Facies, 2019

The Late Ordovician succession of the Baltic Basin contains a characteristic fine-grained limesto... more The Late Ordovician succession of the Baltic Basin contains a characteristic fine-grained limestone, which is rich in calcareous green algae. This limestone occurs in surface outcrops and drill-cores in an extensive belt reaching from Sweden across the Baltic Sea to the Baltic countries. This limestone, which is known in the literature under several different lithological names, is described and interpreted, and the term “Baltic limestone facies” is suggested. The microfacies, from selected outcrops from the Åland Islands, Finland and Estonia, consists of calcareous green algae as the main skeletal component in a bioclastic mudstone-packstone lithology with a pure micritic matrix. Three types of calcitarch, which range in diameter from c. 100–180 μm, are common. Basinward, the youngest sections of the facies belt contain coral-stromatoporoid patch reefs andPalaeoporella-algal mounds. The Baltic limestone facies can be interpreted as representing the shallow part of an open-marine lo...

Sedimentary Geology, Oct 1, 2022

The calcareous microproblematicum Halysis Høeg, 1932 occurs in abundance in Ordovician fine-grain... more The calcareous microproblematicum Halysis Høeg, 1932 occurs in abundance in Ordovician fine-grained, reddish carbonate mounds rich in spar-cemented cavities (Katian, Tarim Basin, NW China). Morphological analysis of Halysis suggests a U-shape skeleton punctually attached to a soft substrate of carbonate sand and silt. The skeletons have a maximum width of 12 mm and consist of laterally branching tubes. The tubes display circular to laterallyflattened outlines with a mean diameter ~125 μm. The tube walls consist of an inner and an outer layer of microcrystalline calcite, and a central layer of imbricated, radially arranged calcite tablets. An affinity of Halysis with extant siphonous calcareous green algae (Bryopsidales, Udoteaceae) is likely. If correct, Halysis represents a case of a green alga that acquired its skeleton de novo in accordance with sea-water chemistry (low genetic control, low-magnesium calcite, Ordovician calcite sea). Halysis carbonate mounds are low-relief, inter...

Sedimentology, 2017

Calathid-demosponge carbonate mounds are a feature of Early to Middle Ordovician shallow marine c... more Calathid-demosponge carbonate mounds are a feature of Early to Middle Ordovician shallow marine carbonate depositional environments of tropical to subtropical paleolatitudes. These mounds contain an important amount of autochthonous non-skeletal microcrystalline Cacarbonate (automicrite) conventionally considered microbial in origin. Here, the automicrite of calathid-demosponge carbonate mounds (Tarim Basin, northwest China) is broken down to five distinct fabrics: an in situ peloidal-spiculiferous fabric (AM-1), an in situ peloidal fabric (AM-2), an aphanitic-microtubular fabric (AM-3), a minipeloidal fabric (AM-4) and a laminoid-cerebroid fabric (AM-5). Type AM-1 occurs with AM-2 being succeeded by an This article is protected by copyright. All rights reserved. assemblage of AM-3 and AM-4. Types AM-4 and AM-5 are separated by an erosional disconformity. A good correlation of fluorescence and cathodoluminescence of automicrites indicates that induced and supported organomineralization produced automicrite, probably via the permineralization of non-living organic substrates adsorbing dissolved metal-humate complexes. Using a spreadsheet with six parameters and 17 characters, AM-1 to AM-4 turn out to be non-microbial in origin. Instead, these automicrites represent relics of calcified metazoan tissues such as siliceous sponges, non-spiculate sponges or the basal attachment structures of stalked invertebrates. Fabric AM-5 is a microbial carbonate but is post-mound in origin forming a drape within a reefal framework established by AM-4. The five automicritic fabrics, individually or as an assemblage, are a common element of Ordovician calathiddemosponge carbonate mounds in general. The reassessment of the origins of these automicritic fabrics holds consequences for the understanding of the Great Ordovician Biodiversification Event in terms of community structure, reef ecology and reef evolution. Episodically, these fabrics are also present in other carbonate buildups stretching from the Neoproterozoic over the entire Phanerozoic Eon. The massive calcification of metazoan soft tissue (AM-1 to AM-4) characterizes episodes and conditions of enhanced marine calcification and might be of value to refine secular trends of pCO 2 , Ca-concentration and Mg/Ca ratio at the scale of individual sedimentary basins.

Canadian Journal of Earth Sciences, 2016

Despite the crucial role of epibenthic primary producers (cyanobacteria, green and red algae), no... more Despite the crucial role of epibenthic primary producers (cyanobacteria, green and red algae), no diversity curves for calcimicrobes and calcareous algae are available to assess the pyramiding paleoecology characterizing the Ordovician biodiversification episode. A total of 24 taxa of calcimicrobes and calcareous algae are identified from a Dapingian to lower Katian succession of carbonate sedimentary rocks exposed at the Leyayilitag ridge, Bachu Uplift, Tarim Basin, northwest China. Calcimicrobes (14 taxa), Dasycladales (seven taxa), Bryopsidales (one taxon), and Cyclocrinales (two taxa) contribute to five distinct taphocoenoses characterizing a suite of carbonate mounds. In stratigraphic order, these are calathid sponge mounds, algal calcimicrobial mounds, algal mounds, algal reefs, and calcimicrobial mounds. Within the lower Katian Belodina confluens Zone, the diversity increases substantially from around 5 to more than 20 taxa per 2 Ma. This increase in diversity is based on new...

PALAIOS, 2015

DESCRIPTION Conference abstract for AGU-CGU-GAC-MAC Joint Assembly, 2015, Montreal The manuscript... more DESCRIPTION Conference abstract for AGU-CGU-GAC-MAC Joint Assembly, 2015, Montreal The manuscript was accepted by the journal of PALAIOS.

Despite the crucial role of epibenthic primary producers (cyanobacteria, green and red algae), no... more Despite the crucial role of epibenthic primary producers (cyanobacteria, green and red algae), no diversity curves for calcimicrobes and calcareous algae are available to assess the pyramiding paleoecology characterizing the Ordovician biodiversifica-tion episode. A total of 24 taxa of calcimicrobes and calcareous algae are identified from a Dapingian to lower Katian succession of carbonate sedimentary rocks exposed at the Leyayilitag ridge, Bachu Uplift, Tarim Basin, northwest China. Calcimicrobes (14 taxa), Dasycladales (seven taxa), Bryopsidales (one taxon), and Cyclocrinales (two taxa) contribute to five distinct taphocoenoses characterizing a suite of carbonate mounds. In stratigraphic order, these are calathid sponge mounds, algal calcimicrobial mounds, algal mounds, algal reefs, and calcimicrobial mounds. Within the lower Katian Belodina confluens Zone, the diversity increases substantially from around 5 to more than 20 taxa per 2 Ma. This increase in diversity is based on new calcimicrobes (Bija, Ortonella, Garwoodia, Hedstroemia, Rothpletzella, Phacelophyton, Rauserina) and the diversification of Dasycladales and Cyclocrinales. By comparison, the global diversity of calcimicrobes and calcareous algae (derived from literature data) started to increase earlier, namely within the late Darriwilian Pygodus serra Zone (offset of about 4 Ma). This offset might be due to the peculiar lithology of the Sandbian Tumuxiuke Formation (condensed section of red nodular limestones bounded by disconformities). However, a similar temporal offset is recorded for calathid sponge mounds; therefore, the Tarim tectonic microplate (Tarim Block) might display an endemic–anachronistic character. The diversity curves of Ordovician benthic primary producers (calcimicrobes, calcareous algae) are similar to those recorded by some fossil groups, in particular eleutherozoan echinoderms. Résumé : Malgré le rôle clé des producteurs primaires épibenthiques (cyanobactéries, algues vertes et rouges), aucune courbe de diversité pour les calcimicrobes et les algues calcaires n'est disponible pour évaluer la paléoécologie pyramidale qui caractérise l'épisode de biodiversification ordovicienne. Un total de 24 taxons de calcimicrobes et d'algues calcaires sont identifiés dans une séquence allant du Dapingien au Katien inférieur de roches sédimentaires carbonatées exposée sur la crête de Leyayilitag, dans la zone de soulèvement de Bachu du bassin du Tarim (nord-ouest de la Chine). Des calcimicrobes (14 taxons), dasycladales (sept taxons), bryopsidales (un taxon) et cyclocrinales (deux taxons) font partie de cinq thanatocoenoses distinctes qui caractérisent une suite de monticules carbonatés. En ordre stratigraphique, il s'agit de monticules d'éponges calathides, de monticules algaires et calcimicro-biens, des monticules algaires, des récifs algaires et des monticules calcimicrobiens. Dans la zone a ` Belodina confluens du Katien inférieur, la diversité augmente considérablement d'environ 5 a ` plus de 20 taxons chaque 2 Ma. Cette augmentation de la diversité repose sur de nouveaux calcimicrobes (Bija, Ortonella, Garwoodia, Hedstroemia, Rothpletzella, Phacelophyton, Rauserina) et la diversification des dasycladales et cyclocrinales. En comparaison, la diversité planétaire des calcimicrobes et des algues calcaires (tirée de données publiées) a commencé a ` augmenter plus tôt, soit dans la zone a ` Pygodus serra du Darriwilien tardif (un décalage d'environ 4 Ma). Ce décalage pourrait être le fait de la lithologie particulière de la Formation sandbienne de Tumuxiuke (séquence condensée de calcaires nodulaires rouges limités par des discordances érosionnelles). Cependant, un décalage temporel semblable est observé pour des monticules d'éponges cathalides, de sorte que la microplaque tectonique du Tarim (bloc du Tarim) pourrait présenter un caractère endémique–anachronistique. Les courbes de diversité des producteurs primaires benthiques (calcimicrobes et algues calcaires) de l'Ordovicien sont semblables a ` celles enregistrées par certains groupes de fossiles, en particulier les échinodermes éleuthérozoaires. [Traduit par la Rédaction]

The calcareous microproblematicum Halysis Høeg, 1932 occurs in abundance in Ordovician fine-grain... more The calcareous microproblematicum Halysis Høeg, 1932 occurs in abundance in Ordovician fine-grained, reddish carbonate mounds rich in spar-cemented cavities (Katian, Tarim Basin, NW China). Morphological analysis of Halysis suggests a U-shape skeleton punctually attached to a soft substrate of carbonate sand and silt. The skeletons have a maximum width of 12 mm and consist of laterally branching tubes. The tubes display circular to laterally flattened outlines with a mean diameter , 125 mm. The tube walls consist of an inner and an outer layer of microcrystalline calcite, and a central layer of imbricated, radially arranged calcite tablets. An affinity of Halysis with extant siphonous calcareous green algae (Bryopsidales, Udoteaceae) is likely. If correct, Halysis represents a case of a green alga that acquired its skeleton de novo in accordance with seawater chemistry (low genetic control, low-magnesium calcite, Ordovician calcite sea). Halysis carbonate mounds are low-relief, internally bedded, shallow-water packstone to grainstone banks. Spar-cemented cavities are Halysis-supported shelter cavities (, 90%) and depositional cavities (, 10%) produced from sediment-laden flows. The mounds formed as part of a shallow-subtidal carbonate ramp dominated by algal-pellet sand sheets. Autocyclic drivers (sand propagation via tides, storms) produced increments of sediment burial followed by episodes of omission and algal growth. These mounds should not be mistaken for " shallow-water carbonate mudmounds " nor for algal framework reefs. In terms of facies, texture, biostratinomy and primary porosity, these mounds are considered a miniature version of bryozoan-rich carbonate banks. Twisted and imbricated aggregates of fronds of Halysis produced shelter cavities making up , 5% of the total mound rock volume, thereby reducing accommodation space in sufficient quantity to explain mound formation. A review shows that Halysis presented herein displays the largest and most robust intrageneric growth form compared to occurrences of more basinal settings (Ordovician) as well as much younger carbonate deposits (Silurian to Devonian).

Facies, 2019

The Late Ordovician succession of the Baltic Basin contains a characteristic fine-grained limesto... more The Late Ordovician succession of the Baltic Basin contains a characteristic fine-grained limestone, which is rich in calcareous green algae. This limestone occurs in surface outcrops and drill-cores in an extensive belt reaching from Sweden across the Baltic Sea to the Baltic countries. This limestone, which is known in the literature under several different lithological names, is described and interpreted, and the term “Baltic limestone facies” is suggested. The microfacies, from selected outcrops from the Åland Islands, Finland and Estonia, consists of calcareous green algae as the main skeletal component in a bioclastic mudstone-packstone lithology with a pure micritic matrix. Three types of calcitarch, which range in diameter from c. 100–180 μm, are common. Basinward, the youngest sections of the facies belt contain coral-stromatoporoid patch reefs andPalaeoporella-algal mounds. The Baltic limestone facies can be interpreted as representing the shallow part of an open-marine lo...

Sedimentary Geology, Oct 1, 2022

The calcareous microproblematicum Halysis Høeg, 1932 occurs in abundance in Ordovician fine-grain... more The calcareous microproblematicum Halysis Høeg, 1932 occurs in abundance in Ordovician fine-grained, reddish carbonate mounds rich in spar-cemented cavities (Katian, Tarim Basin, NW China). Morphological analysis of Halysis suggests a U-shape skeleton punctually attached to a soft substrate of carbonate sand and silt. The skeletons have a maximum width of 12 mm and consist of laterally branching tubes. The tubes display circular to laterallyflattened outlines with a mean diameter ~125 μm. The tube walls consist of an inner and an outer layer of microcrystalline calcite, and a central layer of imbricated, radially arranged calcite tablets. An affinity of Halysis with extant siphonous calcareous green algae (Bryopsidales, Udoteaceae) is likely. If correct, Halysis represents a case of a green alga that acquired its skeleton de novo in accordance with sea-water chemistry (low genetic control, low-magnesium calcite, Ordovician calcite sea). Halysis carbonate mounds are low-relief, inter...

Sedimentology, 2017

Calathid-demosponge carbonate mounds are a feature of Early to Middle Ordovician shallow marine c... more Calathid-demosponge carbonate mounds are a feature of Early to Middle Ordovician shallow marine carbonate depositional environments of tropical to subtropical paleolatitudes. These mounds contain an important amount of autochthonous non-skeletal microcrystalline Cacarbonate (automicrite) conventionally considered microbial in origin. Here, the automicrite of calathid-demosponge carbonate mounds (Tarim Basin, northwest China) is broken down to five distinct fabrics: an in situ peloidal-spiculiferous fabric (AM-1), an in situ peloidal fabric (AM-2), an aphanitic-microtubular fabric (AM-3), a minipeloidal fabric (AM-4) and a laminoid-cerebroid fabric (AM-5). Type AM-1 occurs with AM-2 being succeeded by an This article is protected by copyright. All rights reserved. assemblage of AM-3 and AM-4. Types AM-4 and AM-5 are separated by an erosional disconformity. A good correlation of fluorescence and cathodoluminescence of automicrites indicates that induced and supported organomineralization produced automicrite, probably via the permineralization of non-living organic substrates adsorbing dissolved metal-humate complexes. Using a spreadsheet with six parameters and 17 characters, AM-1 to AM-4 turn out to be non-microbial in origin. Instead, these automicrites represent relics of calcified metazoan tissues such as siliceous sponges, non-spiculate sponges or the basal attachment structures of stalked invertebrates. Fabric AM-5 is a microbial carbonate but is post-mound in origin forming a drape within a reefal framework established by AM-4. The five automicritic fabrics, individually or as an assemblage, are a common element of Ordovician calathiddemosponge carbonate mounds in general. The reassessment of the origins of these automicritic fabrics holds consequences for the understanding of the Great Ordovician Biodiversification Event in terms of community structure, reef ecology and reef evolution. Episodically, these fabrics are also present in other carbonate buildups stretching from the Neoproterozoic over the entire Phanerozoic Eon. The massive calcification of metazoan soft tissue (AM-1 to AM-4) characterizes episodes and conditions of enhanced marine calcification and might be of value to refine secular trends of pCO 2 , Ca-concentration and Mg/Ca ratio at the scale of individual sedimentary basins.

Canadian Journal of Earth Sciences, 2016

Despite the crucial role of epibenthic primary producers (cyanobacteria, green and red algae), no... more Despite the crucial role of epibenthic primary producers (cyanobacteria, green and red algae), no diversity curves for calcimicrobes and calcareous algae are available to assess the pyramiding paleoecology characterizing the Ordovician biodiversification episode. A total of 24 taxa of calcimicrobes and calcareous algae are identified from a Dapingian to lower Katian succession of carbonate sedimentary rocks exposed at the Leyayilitag ridge, Bachu Uplift, Tarim Basin, northwest China. Calcimicrobes (14 taxa), Dasycladales (seven taxa), Bryopsidales (one taxon), and Cyclocrinales (two taxa) contribute to five distinct taphocoenoses characterizing a suite of carbonate mounds. In stratigraphic order, these are calathid sponge mounds, algal calcimicrobial mounds, algal mounds, algal reefs, and calcimicrobial mounds. Within the lower Katian Belodina confluens Zone, the diversity increases substantially from around 5 to more than 20 taxa per 2 Ma. This increase in diversity is based on new...

PALAIOS, 2015

DESCRIPTION Conference abstract for AGU-CGU-GAC-MAC Joint Assembly, 2015, Montreal The manuscript... more DESCRIPTION Conference abstract for AGU-CGU-GAC-MAC Joint Assembly, 2015, Montreal The manuscript was accepted by the journal of PALAIOS.

Despite the crucial role of epibenthic primary producers (cyanobacteria, green and red algae), no... more Despite the crucial role of epibenthic primary producers (cyanobacteria, green and red algae), no diversity curves for calcimicrobes and calcareous algae are available to assess the pyramiding paleoecology characterizing the Ordovician biodiversifica-tion episode. A total of 24 taxa of calcimicrobes and calcareous algae are identified from a Dapingian to lower Katian succession of carbonate sedimentary rocks exposed at the Leyayilitag ridge, Bachu Uplift, Tarim Basin, northwest China. Calcimicrobes (14 taxa), Dasycladales (seven taxa), Bryopsidales (one taxon), and Cyclocrinales (two taxa) contribute to five distinct taphocoenoses characterizing a suite of carbonate mounds. In stratigraphic order, these are calathid sponge mounds, algal calcimicrobial mounds, algal mounds, algal reefs, and calcimicrobial mounds. Within the lower Katian Belodina confluens Zone, the diversity increases substantially from around 5 to more than 20 taxa per 2 Ma. This increase in diversity is based on new calcimicrobes (Bija, Ortonella, Garwoodia, Hedstroemia, Rothpletzella, Phacelophyton, Rauserina) and the diversification of Dasycladales and Cyclocrinales. By comparison, the global diversity of calcimicrobes and calcareous algae (derived from literature data) started to increase earlier, namely within the late Darriwilian Pygodus serra Zone (offset of about 4 Ma). This offset might be due to the peculiar lithology of the Sandbian Tumuxiuke Formation (condensed section of red nodular limestones bounded by disconformities). However, a similar temporal offset is recorded for calathid sponge mounds; therefore, the Tarim tectonic microplate (Tarim Block) might display an endemic–anachronistic character. The diversity curves of Ordovician benthic primary producers (calcimicrobes, calcareous algae) are similar to those recorded by some fossil groups, in particular eleutherozoan echinoderms. Résumé : Malgré le rôle clé des producteurs primaires épibenthiques (cyanobactéries, algues vertes et rouges), aucune courbe de diversité pour les calcimicrobes et les algues calcaires n'est disponible pour évaluer la paléoécologie pyramidale qui caractérise l'épisode de biodiversification ordovicienne. Un total de 24 taxons de calcimicrobes et d'algues calcaires sont identifiés dans une séquence allant du Dapingien au Katien inférieur de roches sédimentaires carbonatées exposée sur la crête de Leyayilitag, dans la zone de soulèvement de Bachu du bassin du Tarim (nord-ouest de la Chine). Des calcimicrobes (14 taxons), dasycladales (sept taxons), bryopsidales (un taxon) et cyclocrinales (deux taxons) font partie de cinq thanatocoenoses distinctes qui caractérisent une suite de monticules carbonatés. En ordre stratigraphique, il s'agit de monticules d'éponges calathides, de monticules algaires et calcimicro-biens, des monticules algaires, des récifs algaires et des monticules calcimicrobiens. Dans la zone a ` Belodina confluens du Katien inférieur, la diversité augmente considérablement d'environ 5 a ` plus de 20 taxons chaque 2 Ma. Cette augmentation de la diversité repose sur de nouveaux calcimicrobes (Bija, Ortonella, Garwoodia, Hedstroemia, Rothpletzella, Phacelophyton, Rauserina) et la diversification des dasycladales et cyclocrinales. En comparaison, la diversité planétaire des calcimicrobes et des algues calcaires (tirée de données publiées) a commencé a ` augmenter plus tôt, soit dans la zone a ` Pygodus serra du Darriwilien tardif (un décalage d'environ 4 Ma). Ce décalage pourrait être le fait de la lithologie particulière de la Formation sandbienne de Tumuxiuke (séquence condensée de calcaires nodulaires rouges limités par des discordances érosionnelles). Cependant, un décalage temporel semblable est observé pour des monticules d'éponges cathalides, de sorte que la microplaque tectonique du Tarim (bloc du Tarim) pourrait présenter un caractère endémique–anachronistique. Les courbes de diversité des producteurs primaires benthiques (calcimicrobes et algues calcaires) de l'Ordovicien sont semblables a ` celles enregistrées par certains groupes de fossiles, en particulier les échinodermes éleuthérozoaires. [Traduit par la Rédaction]

The calcareous microproblematicum Halysis Høeg, 1932 occurs in abundance in Ordovician fine-grain... more The calcareous microproblematicum Halysis Høeg, 1932 occurs in abundance in Ordovician fine-grained, reddish carbonate mounds rich in spar-cemented cavities (Katian, Tarim Basin, NW China). Morphological analysis of Halysis suggests a U-shape skeleton punctually attached to a soft substrate of carbonate sand and silt. The skeletons have a maximum width of 12 mm and consist of laterally branching tubes. The tubes display circular to laterally flattened outlines with a mean diameter , 125 mm. The tube walls consist of an inner and an outer layer of microcrystalline calcite, and a central layer of imbricated, radially arranged calcite tablets. An affinity of Halysis with extant siphonous calcareous green algae (Bryopsidales, Udoteaceae) is likely. If correct, Halysis represents a case of a green alga that acquired its skeleton de novo in accordance with seawater chemistry (low genetic control, low-magnesium calcite, Ordovician calcite sea). Halysis carbonate mounds are low-relief, internally bedded, shallow-water packstone to grainstone banks. Spar-cemented cavities are Halysis-supported shelter cavities (, 90%) and depositional cavities (, 10%) produced from sediment-laden flows. The mounds formed as part of a shallow-subtidal carbonate ramp dominated by algal-pellet sand sheets. Autocyclic drivers (sand propagation via tides, storms) produced increments of sediment burial followed by episodes of omission and algal growth. These mounds should not be mistaken for " shallow-water carbonate mudmounds " nor for algal framework reefs. In terms of facies, texture, biostratinomy and primary porosity, these mounds are considered a miniature version of bryozoan-rich carbonate banks. Twisted and imbricated aggregates of fronds of Halysis produced shelter cavities making up , 5% of the total mound rock volume, thereby reducing accommodation space in sufficient quantity to explain mound formation. A review shows that Halysis presented herein displays the largest and most robust intrageneric growth form compared to occurrences of more basinal settings (Ordovician) as well as much younger carbonate deposits (Silurian to Devonian).