M. Kamoun, M. Langer, Chahira Zaibi, M. Ben Youssef
Abstract. Thapsus was one of the Roman Empire's largest harbors and is situated next to an easily defended promontory on Tunisia's coast in northern Africa. It was provided with a huge stone and cement breakwater mole that extended almost 1 km into the sea. We examined sedimentological and micropaleontological proxies from 14C-dated core material and shifts in microfauna and macrofauna community structure to infer patterns of sediment dynamics and the chronology of events that shaped the coastal evolution in the Dzira Lagoon at Thapsus over the past 4000 years. The sedimentological and faunal record of environmental changes reflect a sequence of events that display a transition from an open to a semi-closed lagoon environment. At around 4070 cal yr BP and again between 2079 and 1280 cal yr BP, the data reveal two transgressive events and a deposition of sandy sediments in a largely open marine lagoon environment. The transgressive sands overlay marine carbonate sandstones that are upper Pleistocene in age. A gradual closure of the lagoon from 1280 cal yr BP until today is indicated by decreasing species richness values, lower abundances of typical marine taxa, and increasing percent abundances of fine-grained sediments. The environmental transition from an open to a closed lagoon setting was also favored by the construction of an extensive harbor breakwater mole, changes in longshore current drift patterns, and the formation of an extensive sand spit.
摘要塔普苏斯是罗马帝国最大的港口之一，位于北非突尼斯海岸一个容易防守的海角旁边。它有一个巨大的石头和水泥防波堤，延伸到海中近1公里。我们研究了沉积学和微古生物学的代用物，这些代用物来自14c年代的岩心材料，以及小动物和大型动物群落结构的变化，以推断出在过去4000年里形成塔普苏斯DziraLagoon海岸演化的沉积动力学模式和事件的年代学。环境变化的沉积学和动物记录反映了一系列事件，显示了从开放到半封闭的泻湖环境的转变。在大约4070 calyr BP和2079 - 1280 calyr BP之间，数据显示了两次海侵事件和一次沙质沉积物沉积，主要发生在开阔的海洋泻湖环境中。海侵砂覆在上更新世海相碳酸盐岩上。从1280 cal yr BP到今天，泻湖逐渐关闭，物种丰富度值下降，典型海洋分类群的丰度降低，细粒沉积物的丰度百分比增加。从开放式泻湖到封闭式泻湖的环境转变也得益于大规模港口防波堤的建设，沿岸洋流漂移模式的变化，以及广泛和吐槽的形成。
{"title":"Meghalayan environmental evolution of the Thapsus coast (Tunisia) as inferred from sedimentological and micropaleontological proxies","authors":"M. Kamoun, M. Langer, Chahira Zaibi, M. Ben Youssef","doi":"10.5194/jm-41-129-2022","DOIUrl":"https://doi.org/10.5194/jm-41-129-2022","url":null,"abstract":"Abstract. Thapsus was one of the Roman Empire's largest harbors and is situated next to\u0000an easily defended promontory on Tunisia's coast in northern Africa. It was\u0000provided with a huge stone and cement breakwater mole that extended almost 1 km into the sea. We examined sedimentological and micropaleontological\u0000proxies from 14C-dated core material and shifts in microfauna and\u0000macrofauna community structure to infer patterns of sediment dynamics and\u0000the chronology of events that shaped the coastal evolution in the Dzira\u0000Lagoon at Thapsus over the past 4000 years. The sedimentological and faunal record of environmental changes reflect a sequence of events that\u0000display a transition from an open to a semi-closed lagoon environment. At\u0000around 4070 cal yr BP and again between 2079 and 1280 cal yr BP, the data reveal two transgressive events and a deposition of sandy sediments in\u0000a largely open marine lagoon environment. The transgressive sands overlay\u0000marine carbonate sandstones that are upper Pleistocene in age. A gradual\u0000closure of the lagoon from 1280 cal yr BP until today is indicated by\u0000decreasing species richness values, lower abundances of typical marine taxa,\u0000and increasing percent abundances of fine-grained sediments. The\u0000environmental transition from an open to a closed lagoon setting was also\u0000favored by the construction of an extensive harbor breakwater mole, changes\u0000in longshore current drift patterns, and the formation of an extensive\u0000sand spit.\u0000","PeriodicalId":54786,"journal":{"name":"Journal of Micropalaeontology","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2022-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48638995","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
P. Pearson, E. John, B. Wade, S. D’haenens, C. Lear
Abstract. Muricate planktonic foraminifera comprise an extinct clade that was diverse and abundant in the Paleogene oceans and are widely used in palaeoclimate research as geochemical proxy carriers for the upper oceans. Their characteristic wall texture has surface projections called “muricae” formed by upward deflection and mounding of successive layers of the test wall. The group is generally considered to have lacked “true spines”: that is, acicular calcite crystals embedded in and projecting from the test surface such as occur in many modern and some Paleogene groups. Here we present evidence from polished sections, surface wall scanning electron microscope images and test dissections, showing that radially orientated crystalline spine-like structures occur in the centre of muricae in various species of Acarinina and Morozovella and projected from the test wall in life. Their morphology and placement in the wall suggest that they evolved independently of true spines. Nevertheless, they may have served a similar range of functions as spines in modern species, including aiding buoyancy and predation and especially harbouring algal photosymbionts, the function for which we suggest they probably first evolved. Our observations strengthen the analogy between Paleogene mixed-layer-dwelling planktonic foraminifera and their modern spinose counterparts.
{"title":"Spine-like structures in Paleogene muricate planktonic foraminifera","authors":"P. Pearson, E. John, B. Wade, S. D’haenens, C. Lear","doi":"10.5194/jm-41-107-2022","DOIUrl":"https://doi.org/10.5194/jm-41-107-2022","url":null,"abstract":"Abstract. Muricate planktonic foraminifera comprise an extinct\u0000clade that was diverse and abundant in the Paleogene oceans and are widely\u0000used in palaeoclimate research as geochemical proxy carriers for the upper\u0000oceans. Their characteristic wall texture has surface projections called\u0000“muricae” formed by upward deflection and mounding of successive layers of\u0000the test wall. The group is generally considered to have lacked “true\u0000spines”: that is, acicular calcite crystals embedded in and projecting from\u0000the test surface such as occur in many modern and some Paleogene groups.\u0000Here we present evidence from polished sections, surface wall scanning\u0000electron microscope images and test dissections, showing that radially\u0000orientated crystalline spine-like structures occur in the centre of muricae\u0000in various species of Acarinina and Morozovella and projected from the test wall in life. Their\u0000morphology and placement in the wall suggest that they evolved\u0000independently of true spines. Nevertheless, they may have served a similar\u0000range of functions as spines in modern species, including aiding buoyancy\u0000and predation and especially harbouring algal photosymbionts, the function\u0000for which we suggest they probably first evolved. Our observations\u0000strengthen the analogy between Paleogene mixed-layer-dwelling planktonic\u0000foraminifera and their modern spinose counterparts.\u0000","PeriodicalId":54786,"journal":{"name":"Journal of Micropalaeontology","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2022-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45922417","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Micaela Chaumeil Rodríguez, E. Mattioli, J. P. Pérez Panera
Abstract. Standard Early Jurassic biostratigraphic studies were performed in the boreal and Tethys realms (western Europe and northern Africa), and biozonations from these areas are the most accurate of the world. Comparatively, investigations in the Pacific realm are scarce, and, in Argentina, they are limited to contributions based on oil-industry subsurface and outcrop reports for the Los Molles Formation. A focused systematic analysis was not previously addressed in the area. The Neuquén Basin in west–central Argentina offers a unique opportunity to study the Early Jurassic calcareous nannofossil history in the south-eastern Pacific Ocean. Calcareous nannofossil assemblages from El Matuasto I section (Los Molles Formation) represent one of the earliest records for the Early Jurassic in the Neuquén Basin and one of the few for the eastern Pacific realm. A detailed systematic analysis allowed the recognition of major bioevents and a comparison with worldwide associations and biostratigraphic schemes. A thorough taxonomic discussion of the Early Jurassic nannofossil species of the Neuquén Basin is presented for the first time. Herein, the taxonomic features of coccoliths recorded in the Neuquén Basin are settled. The age of the calcareous nannofossil assemblages recorded in El Matuasto I is early–late Pliensbachian, covering the NJT4a to NJT4c subzones. Similarities between the Neuquén Basin and localities from the proto-Atlantic region suggest an effective connection between the Pacific and Tethyan basins during the Pliensbachian.
{"title":"Lower Jurassic calcareous nannofossil taxonomy revisited according to the Neuquén Basin (Argentina) record","authors":"Micaela Chaumeil Rodríguez, E. Mattioli, J. P. Pérez Panera","doi":"10.5194/jm-41-75-2022","DOIUrl":"https://doi.org/10.5194/jm-41-75-2022","url":null,"abstract":"Abstract. Standard Early Jurassic biostratigraphic studies were\u0000performed in the boreal and Tethys realms (western Europe and northern\u0000Africa), and biozonations from these areas are the most accurate of the\u0000world. Comparatively, investigations in the Pacific realm are scarce, and, in\u0000Argentina, they are limited to contributions based on oil-industry\u0000subsurface and outcrop reports for the Los Molles Formation. A focused\u0000systematic analysis was not previously addressed in the area. The\u0000Neuquén Basin in west–central Argentina offers a unique opportunity to\u0000study the Early Jurassic calcareous nannofossil history in the\u0000south-eastern Pacific Ocean. Calcareous nannofossil assemblages from El\u0000Matuasto I section (Los Molles Formation) represent one of the earliest\u0000records for the Early Jurassic in the Neuquén Basin and one of the few\u0000for the eastern Pacific realm. A detailed systematic analysis allowed the\u0000recognition of major bioevents and a comparison with worldwide associations\u0000and biostratigraphic schemes. A thorough taxonomic discussion of the Early\u0000Jurassic nannofossil species of the Neuquén Basin is presented for the\u0000first time. Herein, the taxonomic features of coccoliths recorded in the\u0000Neuquén Basin are settled. The age of the calcareous nannofossil\u0000assemblages recorded in El Matuasto I is early–late Pliensbachian, covering\u0000the NJT4a to NJT4c subzones. Similarities between the Neuquén Basin and\u0000localities from the proto-Atlantic region suggest an effective connection\u0000between the Pacific and Tethyan basins during the Pliensbachian.\u0000","PeriodicalId":54786,"journal":{"name":"Journal of Micropalaeontology","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2022-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44026562","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. Applications of fossil shells of planktonic foraminifera to decipher past environmental change and plankton evolution require a robust operational taxonomy. In this respect, extant planktonic foraminifera provide an opportunity for benchmarking the dominantly morphological species concepts and classification of the group by considering ecological, physiological and genetic characters. Although the basic framework of the taxonomy of extant planktonic foraminifera has been stable for half a century, many details have changed, not the least in light of genetic evidence. In this contribution, we review the current taxonomy of living planktonic foraminifera, presenting a comprehensive standard that emerged from the meetings and consultations of the SCOR/IGBP Working Group 138 “Planktonic foraminifera and ocean changes”. We present a comprehensive annotated list of 50 species and subspecies recognized among living planktonic foraminifera and evaluate their generic and suprageneric classification. As a result, we recommend replacing the commonly used names Globorotalia menardii by G. cultrata and Globorotalia theyeri by G. eastropacia, recognize Globorotaloides oveyi as a neglected but valid living species, and propose transferring the three extant species previously assigned to Tenuitella into a separate genus, Tenuitellita. We review the status of types and designate lectotypes for Globoturborotalita rubescens and Globigerinita uvula. We further provide an annotated list of synonyms and other names that have been applied previously to living planktonic foraminifera and outline the reasons for their exclusion. Finally, we provide recommendations on how the presented classification scheme should be used in operational taxonomy for the benefit of producing replicable and interoperable census counts.
{"title":"Taxonomic review of living planktonic foraminifera","authors":"G. Brummer, M. Kučera","doi":"10.5194/jm-41-29-2022","DOIUrl":"https://doi.org/10.5194/jm-41-29-2022","url":null,"abstract":"Abstract. Applications of fossil shells of planktonic foraminifera\u0000to decipher past environmental change and plankton evolution require a\u0000robust operational taxonomy. In this respect, extant planktonic foraminifera\u0000provide an opportunity for benchmarking the dominantly morphological species\u0000concepts and classification of the group by considering ecological,\u0000physiological and genetic characters. Although the basic framework of the\u0000taxonomy of extant planktonic foraminifera has been stable for half a\u0000century, many details have changed, not the least in light of genetic\u0000evidence. In this contribution, we review the current taxonomy of living\u0000planktonic foraminifera, presenting a comprehensive standard that emerged\u0000from the meetings and consultations of the SCOR/IGBP Working Group 138\u0000“Planktonic foraminifera and ocean changes”. We present a comprehensive\u0000annotated list of 50 species and subspecies recognized among living\u0000planktonic foraminifera and evaluate their generic and suprageneric\u0000classification. As a result, we recommend replacing the commonly used names\u0000Globorotalia menardii by G. cultrata and Globorotalia theyeri by G. eastropacia, recognize Globorotaloides oveyi as a neglected but valid living species, and\u0000propose transferring the three extant species previously assigned to\u0000Tenuitella into a separate genus, Tenuitellita. We review the status of types and designate\u0000lectotypes for Globoturborotalita rubescens and Globigerinita uvula. We further provide an annotated list of synonyms and\u0000other names that have been applied previously to living planktonic\u0000foraminifera and outline the reasons for their exclusion. Finally, we\u0000provide recommendations on how the presented classification scheme should be\u0000used in operational taxonomy for the benefit of producing replicable and\u0000interoperable census counts.\u0000","PeriodicalId":54786,"journal":{"name":"Journal of Micropalaeontology","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2022-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42769210","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. The middle Eocene sedimentary sequence drilled at Ocean Drilling Program Site 1260 (Leg 207), Demerara Rise, western equatorial Atlantic, yielded a rich and diverse radiolarian fauna. The exceptionally expanded and complete sedimentary record of this site, as well as the existence of an orbital chronological framework, allowed us to study a number of radiolarian bioevents with a very fine temporal resolution. We compiled a well-resolved succession of 71 radiolarian bioevents (first occurrences, last occurrences, and evolutionary transitions) and provided calibrations to the geomagnetic polarity timescale and astronomical timescale. Comparison of the radiolarian successions at ODP Site 1260A with the northwestern Atlantic IODP Site U1403 and the IODP Sites U1331, U1332, and 1333, situated in eastern equatorial Pacific, allowed the demonstration of the synchroneity of primary radiolarian bioevents that underpin the middle Eocene zonal scheme. Several secondary bioevents were also found to be synchronous between the two oceans and were therefore used to define seven new subzones for the low-latitudinal middle Eocene sequences: Siphocampe ? amygdala interval subzone (RP13a), Coccolarnacium periphaenoides interval subzone (RP13b), Artostrobus quadriporus interval subzone (RP14a), Sethochytris triconiscus interval subzone (RP14b), Podocyrtis (Podocyrtopsis) apeza interval subzone (RP14c), Artobotrys biaurita interval subzone (RP15a), and Thyrsocyrtis (Pentalocorys) krooni interval subzone (RP15b). This refined radiolarian biozonation has significantly improved stratigraphic resolution and age control for the late middle Eocene interval (an average of two subzones per 1.5 million years). A substantial diachronism was also found in 20 secondary radiolarian bioevents between the two oceans. The majority of radiolarian species appear to have evolved first in the equatorial Atlantic Ocean and subsequently in the equatorial Pacific. However, the reasons for this pattern of diachroneity currently remain uncertain and would require a greater sampling coverage to be elucidated.
{"title":"Astronomical calibration of late middle Eocene radiolarian bioevents from ODP Site 1260 (equatorial Atlantic, Leg 207) and refinement of the global tropical radiolarian biozonation","authors":"Mathias Meunier, T. Danelian","doi":"10.5194/jm-41-1-2022","DOIUrl":"https://doi.org/10.5194/jm-41-1-2022","url":null,"abstract":"Abstract. The middle Eocene sedimentary sequence drilled at Ocean\u0000Drilling Program Site 1260 (Leg 207), Demerara Rise, western equatorial\u0000Atlantic, yielded a rich and diverse radiolarian fauna. The exceptionally\u0000expanded and complete sedimentary record of this site, as well as the\u0000existence of an orbital chronological framework, allowed us to study a\u0000number of radiolarian bioevents with a very fine temporal resolution. We\u0000compiled a well-resolved succession of 71 radiolarian bioevents (first\u0000occurrences, last occurrences, and evolutionary transitions) and provided\u0000calibrations to the geomagnetic polarity timescale and astronomical timescale. Comparison of the radiolarian successions at ODP Site 1260A with the\u0000northwestern Atlantic IODP Site U1403 and the IODP Sites U1331, U1332, and\u00001333, situated in eastern equatorial Pacific, allowed the demonstration of the\u0000synchroneity of primary radiolarian bioevents that underpin the middle\u0000Eocene zonal scheme. Several secondary bioevents were also found to be\u0000synchronous between the two oceans and were therefore used to define seven\u0000new subzones for the low-latitudinal middle Eocene sequences: Siphocampe ? amygdala interval\u0000subzone (RP13a), Coccolarnacium periphaenoides interval subzone (RP13b), Artostrobus quadriporus interval subzone (RP14a),\u0000Sethochytris triconiscus interval subzone (RP14b), Podocyrtis (Podocyrtopsis) apeza interval subzone (RP14c), Artobotrys biaurita interval subzone\u0000(RP15a), and Thyrsocyrtis (Pentalocorys) krooni interval subzone (RP15b). This refined radiolarian\u0000biozonation has significantly improved stratigraphic resolution and age\u0000control for the late middle Eocene interval (an average of two subzones per\u00001.5 million years). A substantial diachronism was also found in 20 secondary\u0000radiolarian bioevents between the two oceans. The majority of radiolarian\u0000species appear to have evolved first in the equatorial Atlantic Ocean and\u0000subsequently in the equatorial Pacific. However, the reasons for this\u0000pattern of diachroneity currently remain uncertain and would require a\u0000greater sampling coverage to be elucidated.\u0000","PeriodicalId":54786,"journal":{"name":"Journal of Micropalaeontology","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2022-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42105822","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Schönfeld, V. Beccari, Sarina Schmidt, S. Spezzaferri
Abstract. Living Ammonia species and an inventory of dead assemblages from Adriatic subtidal, nearshore environments were investigated at four stations off Bellaria, Italy. Ammonia falsobeccarii, Ammonia parkinsoniana, Ammonia tepida, and Ammonia veneta were recognized in the living (rose-bengal-stained) fauna, and Ammonia bellaria n. sp. is described herein for the first time. Ammonia beccarii was only found in the dead assemblage. The biometry of 368 living individuals was analysed by using light microscopic and scanning electron microscopic images of three aspects. A total of 15 numerical and 8 qualitative parameters were measured and assessed, 5 of which were recognized to be prone to a certain subjectivity of the observer. The accuracy of numerical data as revealed by the mean residuals of parallel measurements by different observers ranged from 0.5 % to 5.5 %. The results indicated a high degree of intraspecific variability. The test sizes of the individual species were log-normally distributed and varied among the stations. Parameters not related to the growth of the individuals, i.e. flatness of the tests, dimensions of the second-youngest chamber, proloculus, umbilical and pore diameter, sinistral–dextral coiling, and umbilical boss size, were recognized as being species-distinctive in combination. They may well supplement qualitative criteria that were commonly used for species discrimination such as a lobate outline, a subacute or rounded peripheral margin, or the degree of ornamentation on the spiral and umbilical sides. The averages of the measured parameters were often lower than the range of previously published values, mainly because the latter were retrieved from a few adult specimens and not from the whole assemblage as in the present approach. We conclude that the unprecedented high proportions of Ammonia beccarii in the northern Adriatic may well be artificial. A robust species identification without genetic analyses is possible by considering designated biometric parameters. This approach is also applicable to earlier literature data, and their re-assessment is critical for a correct denomination of recent genotypes.
{"title":"Biometry and taxonomy of Adriatic Ammonia species from Bellaria–Igea Marina (Italy)","authors":"J. Schönfeld, V. Beccari, Sarina Schmidt, S. Spezzaferri","doi":"10.5194/jm-40-195-2021","DOIUrl":"https://doi.org/10.5194/jm-40-195-2021","url":null,"abstract":"Abstract. Living Ammonia species and an inventory of dead assemblages from Adriatic\u0000subtidal, nearshore environments were investigated at four stations off\u0000Bellaria, Italy. Ammonia falsobeccarii, Ammonia parkinsoniana, Ammonia tepida, and Ammonia veneta were recognized in the living (rose-bengal-stained)\u0000fauna, and Ammonia bellaria n. sp. is described herein for the first time. Ammonia beccarii was only found\u0000in the dead assemblage. The biometry of 368 living individuals was analysed\u0000by using light microscopic and scanning electron microscopic images of three\u0000aspects. A total of 15 numerical and 8 qualitative parameters were measured and\u0000assessed, 5 of which were recognized to be prone to a certain\u0000subjectivity of the observer. The accuracy of numerical data as revealed by\u0000the mean residuals of parallel measurements by different observers ranged\u0000from 0.5 % to 5.5 %. The results indicated a high degree of intraspecific\u0000variability. The test sizes of the individual species were log-normally\u0000distributed and varied among the stations. Parameters not related to the\u0000growth of the individuals, i.e. flatness of the tests, dimensions of the\u0000second-youngest chamber, proloculus, umbilical and pore diameter,\u0000sinistral–dextral coiling, and umbilical boss size, were recognized as being\u0000species-distinctive in combination. They may well supplement qualitative\u0000criteria that were commonly used for species discrimination such as a lobate\u0000outline, a subacute or rounded peripheral margin, or the degree of\u0000ornamentation on the spiral and umbilical sides. The averages of the\u0000measured parameters were often lower than the range of previously published\u0000values, mainly because the latter were retrieved from a few adult specimens\u0000and not from the whole assemblage as in the present approach. We conclude\u0000that the unprecedented high proportions of Ammonia beccarii in the northern Adriatic may\u0000well be artificial. A robust species identification without genetic analyses\u0000is possible by considering designated biometric parameters. This approach is\u0000also applicable to earlier literature data, and their re-assessment is\u0000critical for a correct denomination of recent genotypes.\u0000","PeriodicalId":54786,"journal":{"name":"Journal of Micropalaeontology","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2021-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49088239","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
F. Hoem, I. Sauermilch, Suning Hou, H. Brinkhuis, F. Sangiorgi, P. Bijl
Abstract. Improvements in our capability to reconstruct ancient surface-ocean conditions based on organic-walled dinoflagellate cyst (dinocyst) assemblages from the Southern Ocean provide an opportunity to better establish past position, strength and oceanography of the subtropical front (STF). Here, we aim to reconstruct the late Eocene to early Miocene (37–20 Ma) depositional and palaeoceanographic history of the STF in the context of the evolving Tasmanian Gateway as well as the potential influence of Antarctic circumpolar flow and intense waxing and waning of ice. We approach this by combining information from seismic lines (revisiting existing data and generating new marine palynological data from Ocean Drilling Program (ODP) Hole 1168A) in the western Tasmanian continental slope. We apply improved taxonomic insights and palaeoecological models to reconstruct the sea surface palaeoenvironmental evolution. Late Eocene–early Oligocene (37–30.5 Ma) assemblages show a progressive transition from dominant terrestrial palynomorphs and inner-neritic dinocyst taxa as well as cysts produced by heterotrophic dinoflagellates to predominantly outer-neritic/oceanic autotrophic taxa. This transition reflects the progressive deepening of the western Tasmanian continental margin, an interpretation supported by our new seismic investigations. The dominance of autotrophic species like Spiniferites spp. and Operculodinium spp. reflects relatively oligotrophic conditions, like those of regions north of the modern-day STF. The increased abundance in the earliest Miocene of Nematosphaeropsis labyrinthus, typical for modern subantarctic zone (frontal) conditions, indicates a cooling and/or closer proximity of the STF to the site . The absence of major shifts in dinocyst assemblages contrasts with other records in the region and suggests that small changes in surface oceanographic conditions occurred during the Oligocene. Despite the relatively southerly (63–55∘ S) location of Site 1168, the rather stable oceanographic conditions reflect the continued influence of the proto-Leeuwin Current along the southern Australian coast as Australia continued to drift northward. The relatively “warm” dinocyst assemblages at ODP Site 1168, compared with the cold assemblages at Antarctic Integrated Ocean Drilling Program (IODP) Site U1356, testify to the establishment of a pronounced latitudinal temperature gradient in the Oligocene Southern Ocean.
{"title":"Late Eocene–early Miocene evolution of the southern Australian subtropical front: a marine palynological approach","authors":"F. Hoem, I. Sauermilch, Suning Hou, H. Brinkhuis, F. Sangiorgi, P. Bijl","doi":"10.5194/jm-40-175-2021","DOIUrl":"https://doi.org/10.5194/jm-40-175-2021","url":null,"abstract":"Abstract. Improvements in our capability to reconstruct ancient\u0000surface-ocean conditions based on organic-walled dinoflagellate cyst\u0000(dinocyst) assemblages from the Southern Ocean provide an opportunity to\u0000better establish past position, strength and oceanography of the subtropical\u0000front (STF). Here, we aim to reconstruct the late Eocene to early Miocene\u0000(37–20 Ma) depositional and palaeoceanographic history of the STF in the\u0000context of the evolving Tasmanian Gateway as well as the potential influence of\u0000Antarctic circumpolar flow and intense waxing and waning of ice. We approach\u0000this by combining information from seismic lines (revisiting\u0000existing data and generating new marine palynological data from Ocean Drilling Program (ODP) Hole 1168A)\u0000in the western Tasmanian continental slope. We apply improved taxonomic\u0000insights and palaeoecological models to reconstruct the sea surface\u0000palaeoenvironmental evolution. Late Eocene–early Oligocene (37–30.5 Ma)\u0000assemblages show a progressive transition from dominant terrestrial\u0000palynomorphs and inner-neritic dinocyst taxa as well as cysts produced by\u0000heterotrophic dinoflagellates to predominantly outer-neritic/oceanic\u0000autotrophic taxa. This transition reflects the progressive deepening of the\u0000western Tasmanian continental margin, an interpretation supported by our new\u0000seismic investigations. The dominance of autotrophic species like Spiniferites spp. and\u0000Operculodinium spp. reflects relatively oligotrophic conditions, like those of regions\u0000north of the modern-day STF. The increased abundance in the earliest Miocene\u0000of Nematosphaeropsis labyrinthus, typical for modern subantarctic zone (frontal) conditions, indicates a\u0000cooling and/or closer proximity of the STF to the site . The absence of\u0000major shifts in dinocyst assemblages contrasts with other records in the region\u0000and suggests that small changes in surface oceanographic conditions\u0000occurred during the Oligocene. Despite the relatively southerly\u0000(63–55∘ S) location of Site 1168, the rather stable oceanographic\u0000conditions reflect the continued influence of the proto-Leeuwin Current\u0000along the southern Australian coast as Australia continued to drift\u0000northward. The relatively “warm” dinocyst assemblages at ODP Site 1168,\u0000compared with the cold assemblages at Antarctic Integrated Ocean Drilling Program (IODP) Site U1356, testify to the\u0000establishment of a pronounced latitudinal temperature gradient in the\u0000Oligocene Southern Ocean.\u0000","PeriodicalId":54786,"journal":{"name":"Journal of Micropalaeontology","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2021-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45178548","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yemao Hou, Mario Canul‐Ku, Xindong Cui, R. Hasimoto-Beltrán, Min Zhu
Abstract. Vertebrate microfossils have broad applications in evolutionary biology and stratigraphy research areas such as the evolution of hard tissues and stratigraphic correlation. Classification is one of the basic tasks of vertebrate microfossil studies. With the development of techniques for virtual paleontology, vertebrate microfossils can be classified efficiently based on 3D volumes. The semantic segmentation of different fossils and their classes from CT data is a crucial step in the reconstruction of their 3D volumes. Traditional segmentation methods adopt thresholding combined with manual labeling, which is a time-consuming process. Our study proposes a deep-learning-based (DL-based) semantic segmentation method for vertebrate microfossils from CT data. To assess the performance of the method, we conducted extensive experiments on nearly 500 fish microfossils. The results show that the intersection over union (IoU) performance metric arrived at least 94.39 %, meeting the semantic segmentation requirements of paleontologists. We expect that the DL-based method could also be applied to other fossils from CT data with good performance.
{"title":"Semantic segmentation of vertebrate microfossils from computed tomography data using a deep learning approach","authors":"Yemao Hou, Mario Canul‐Ku, Xindong Cui, R. Hasimoto-Beltrán, Min Zhu","doi":"10.5194/jm-40-163-2021","DOIUrl":"https://doi.org/10.5194/jm-40-163-2021","url":null,"abstract":"Abstract. Vertebrate microfossils have broad applications in evolutionary\u0000biology and stratigraphy research areas such as the evolution of hard\u0000tissues and stratigraphic correlation. Classification is one of the basic\u0000tasks of vertebrate microfossil studies. With the development of techniques\u0000for virtual paleontology, vertebrate microfossils can be classified\u0000efficiently based on 3D volumes. The semantic segmentation of different\u0000fossils and their classes from CT data is a crucial step in the\u0000reconstruction of their 3D volumes. Traditional segmentation methods adopt\u0000thresholding combined with manual labeling, which is a time-consuming process. Our\u0000study proposes a deep-learning-based (DL-based) semantic segmentation method for\u0000vertebrate microfossils from CT data. To assess the performance of the\u0000method, we conducted extensive experiments on nearly 500 fish microfossils.\u0000The results show that the intersection over union (IoU) performance metric\u0000arrived at least 94.39 %, meeting the semantic segmentation requirements\u0000of paleontologists. We expect that the DL-based method could also be applied\u0000to other fossils from CT data with good performance.\u0000","PeriodicalId":54786,"journal":{"name":"Journal of Micropalaeontology","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2021-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48900814","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
B. Wade, M. Aljahdali, Y. Mufrreh, A. Memesh, S. AlSoubhi, Iyad S. Zalmout
Abstract. The Rashrashiyah Formation of the Sirhan Basin in northern Saudi Arabia contains diverse assemblages of planktonic foraminifera. We examined the biostratigraphy, stratigraphic range and preservation of upper Eocene planktonic foraminifera. Assemblages are well-preserved and diverse, with 40 species and 11 genera. All samples are assigned to the Priabonian Globigerinatheka semiinvoluta Highest Occurrence Zone (E14), consistent with calcareous nannofossil biostratigraphy indicating Zone CNE17. Well-preserved planktonic foraminifera assemblages from the lower part of the upper Eocene are rare worldwide. Our study provides new insights into the stratigraphic ranges of many species. We find older (Zone E14) stratigraphic occurrences of several species of Globoturborotalita previously thought to have evolved in the latest Eocene (Zone E15, E16) or Oligocene; these include G. barbula, G. cancellata, G. gnaucki, G. pseudopraebulloides, and G. paracancellata. Older stratigraphic occurrences for Dentoglobigerina taci and Subbotina projecta are also found, and Globigerinatheka kugleri occurs at a younger stratigraphic level than previously proposed. Our revisions to stratigraphic ranges indicate that the late Eocene had a higher tropical–subtropical diversity of planktonic foraminifera than hitherto reported.
{"title":"Upper Eocene planktonic foraminifera from northern Saudi Arabia: implications for stratigraphic ranges","authors":"B. Wade, M. Aljahdali, Y. Mufrreh, A. Memesh, S. AlSoubhi, Iyad S. Zalmout","doi":"10.5194/jm-40-145-2021","DOIUrl":"https://doi.org/10.5194/jm-40-145-2021","url":null,"abstract":"Abstract. The Rashrashiyah Formation of the Sirhan Basin in northern Saudi\u0000Arabia contains diverse assemblages of planktonic foraminifera. We examined\u0000the biostratigraphy, stratigraphic range and preservation of upper Eocene\u0000planktonic foraminifera. Assemblages are well-preserved and diverse, with\u000040 species and 11 genera. All samples are assigned to the Priabonian\u0000Globigerinatheka semiinvoluta Highest Occurrence Zone (E14), consistent with calcareous nannofossil\u0000biostratigraphy indicating Zone CNE17. Well-preserved planktonic\u0000foraminifera assemblages from the lower part of the upper Eocene are rare\u0000worldwide. Our study provides new insights into the stratigraphic ranges of\u0000many species. We find older (Zone E14) stratigraphic occurrences of several\u0000species of Globoturborotalita previously thought to have evolved in the latest Eocene (Zone\u0000E15, E16) or Oligocene; these include G. barbula, G. cancellata, G. gnaucki, G. pseudopraebulloides, and G. paracancellata. Older stratigraphic\u0000occurrences for Dentoglobigerina taci and Subbotina projecta are also found, and Globigerinatheka kugleri occurs at a younger stratigraphic\u0000level than previously proposed. Our revisions to stratigraphic ranges\u0000indicate that the late Eocene had a higher tropical–subtropical diversity of\u0000planktonic foraminifera than hitherto reported.\u0000","PeriodicalId":54786,"journal":{"name":"Journal of Micropalaeontology","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2021-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46064059","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. We present a taxonomic revision of the family Fasciculithaceae focused on forms that characterize the early evolution of this family group, which are currently included within the genera Gomphiolithus, Diantholitha, Lithoptychius and Fasciculithus. The investigation approach is based on a combined light microscope (LM) and scanning electron microscope (SEM) analysis of specimens from well-preserved ODP–DSDP site material (ODP Site 1209; Site 1262; ODP Site 1267; DSDP Site 356; DSDP Site 119) and outcrops (Bottaccione and Contessa, Italy; Qreiya, Egypt) across the Danian–Selandian transition. The direct LM–SEM comparison of the same individual specimen provides clarification of several taxa that were previously described only with the LM. One new genus (Tectulithus), five new combinations (Tectulithus janii, Tectulithus merloti, Tectulithus pileatus, Tectulithus stegastos and Tectulithus stonehengei) and six new species are defined (Diantholitha pilula, Diantholitha toquea, Lithoptychius galeottii, Lithoptychius maioranoae, Tectulithus pagodiformis and Fasciculithus realeae). The main characteristics useful to identify fasciculiths with the LM are provided, together with a 3D–2D drawing showing the main structural features. The accurate taxonomic characterization grants the development of an evolutionary lineage that documents a great fasciculith diversification during the late Danian and early Selandian. Four different well-constrained events have been documented: the lowest occurrence (LO) of Gomphiolithus, the paracme of Fasciculithaceae at the top of Chron C27r (PTC27r), the radiation of Diantholitha (LO Diantholitha), the paracme of Fasciculithaceae at the base of Chron C26r (PBC26r), the radiation of Lithoptychius (LO Lithoptychius) and the radiation of Tectulithus (lowest common occurrence of Tectulithus) that shows the biostratigraphic relevance of this group across the Danian–Selandian transition.
{"title":"Revised taxonomy and early evolution of fasciculiths at the Danian–Selandian transition","authors":"F. Miniati, C. Cappelli, S. Monechi","doi":"10.5194/jm-40-101-2021","DOIUrl":"https://doi.org/10.5194/jm-40-101-2021","url":null,"abstract":"Abstract. We present a taxonomic revision of the family\u0000Fasciculithaceae focused on forms that characterize the early evolution of\u0000this family group, which are currently included within the genera\u0000Gomphiolithus, Diantholitha, Lithoptychius and Fasciculithus. The investigation approach is based on a combined light microscope\u0000(LM) and scanning electron microscope (SEM) analysis of specimens from\u0000well-preserved ODP–DSDP site material (ODP Site 1209; Site 1262; ODP Site\u00001267; DSDP Site 356; DSDP Site 119) and outcrops (Bottaccione and Contessa,\u0000Italy; Qreiya, Egypt) across the Danian–Selandian transition. The direct\u0000LM–SEM comparison of the same individual specimen provides clarification of\u0000several taxa that were previously described only with the LM. One new genus\u0000(Tectulithus), five new combinations (Tectulithus janii, Tectulithus merloti, Tectulithus pileatus, Tectulithus stegastos and Tectulithus stonehengei) and six new species are defined\u0000(Diantholitha pilula, Diantholitha toquea, Lithoptychius galeottii, Lithoptychius maioranoae, Tectulithus pagodiformis and Fasciculithus realeae). The main characteristics useful to identify fasciculiths with\u0000the LM are provided, together with a 3D–2D drawing showing the main\u0000structural features. The accurate taxonomic characterization grants the\u0000development of an evolutionary lineage that documents a great fasciculith\u0000diversification during the late Danian and early Selandian. Four different\u0000well-constrained events have been documented: the lowest occurrence (LO) of\u0000Gomphiolithus, the paracme of Fasciculithaceae at the top of Chron C27r (PTC27r), the\u0000radiation of Diantholitha (LO Diantholitha), the paracme of Fasciculithaceae at the base of Chron\u0000C26r (PBC26r), the radiation of Lithoptychius (LO Lithoptychius) and the radiation of Tectulithus (lowest common\u0000occurrence of Tectulithus) that shows the biostratigraphic relevance of this group across\u0000the Danian–Selandian transition.\u0000","PeriodicalId":54786,"journal":{"name":"Journal of Micropalaeontology","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2021-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49022046","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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