Journal of Nannoplankton Research最新文献

{"title":"Use of microbeads to estimate the absolute abundance of nannofossils.","authors":"H. Okada","doi":"10.58998/nina2187","DOIUrl":"https://doi.org/10.58998/nina2187","url":null,"abstract":"","PeriodicalId":186533,"journal":{"name":"Journal of Nannoplankton Research","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116638227","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The potential of nannofossil analysis applied to archaeological studies: the case of Theriace's bronzes.","authors":"A. Fiorentino","doi":"10.58998/jnr2091","DOIUrl":"https://doi.org/10.58998/jnr2091","url":null,"abstract":"The analysis of nannofoss il assemblages has rardy been used in the study of art-works in the past but, recently, the situation has improved. In this context, the nannofossil content of the casting material of the Riace bronze statues was examined in order to locate its provenance and to attempt to identify sites of quarrying. Due to the limited amount of sample material that could be collected from inside the statues, nannofossils were of fundamental relevance in the assignment of ages to the materiaL and more so because no other stratigraphically-meaningful fossi ls were recovered. A decently preserved, Upper Paleocene assemblage was found in one of the statues, which allowed a reasonable hypotheses on provenance to be drawn up . The verification that nannofoss ils could survive the melting process, and that the high temperat ures did not affect their preservation, is important. Therefore, they are very promising for future application in the analysis of archaeological remains. Introduction Two Greek bronze statues, known as the Riace' s bronzes, were recovered some twelve years ago from the Ionian Sea off the coast of Calabria, southern Italy. The statues have been undergoing major restoration for almost two years. All kinds of analyses have been performed during this work, including the study of the palaeontolo.gical content of the casting material. This was aimed at the age determination of the material, in order to locate its area of origin. The analysis of nannofossil assemblages has rarely been used in the study of art-works in the past but , in the last few years, this situation has improved (Svabenick~ , 1993; von Salis, 1995; von Sa1is &Piather, 1995; Yergerio& Meggiolaro, 1995; Meggiolaro et al., 1997; Quinn et al. , 1998, this volume). The casting material is the material used to make the melting cast. Clay is preferably used for this purpose. It constitutes the inside of the model and is covered by wax. Once the wax is modelled, it is also covered by casting material , with a hole left at the top and a hole at the bottom. The melted bronze is then poured through the upper hole. It melts and replaces the wax, which flows out through the lower hole. When the bronze has solidified, the outer cover is removed. The inside of the statue is then emptied through the lower hole, however, it is not possible to remove all of the material, so that small remnants of casting material can still be found attached to the inner surface of the statue (Figure 1). This material is the object of the present study and, where nannofossils were detected, was used to trace possible quarrying sites. Some ofthe material contains reasonably well -preserved nannofossil assemblages, allowing for a coarse age-determination. Methods The Riace 's bronzes have been distinguished as Statue A and Statue B for study purposes (Figure l ). Samples were collected from the residual casting material inside the two statues, at the levels indicated in Figure I , by means of a ","PeriodicalId":186533,"journal":{"name":"Journal of Nannoplankton Research","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117066872","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Late Holocene paleoceanographic changes off south-western Africa as inferred from coccolithophore assemblages.","authors":"Jens Weiser, K. Baumann, Annette Hahn, M. Zabel","doi":"10.58998/jnr2272","DOIUrl":"https://doi.org/10.58998/jnr2272","url":null,"abstract":"Coccolith occurrences in sediment core GeoB 8323-2, from the Benguela Upwelling System off south-western Africa, were analysed to reconstruct the temporal changes in surface water conditions, upwelling intensity and associated productivity during the late Holocene (last 2.25ka BP). Absolute numbers of total coccolithophores are low throughout the core, reaching a maximum of 320 x 106 coccoliths/gram sediment around 770 years BP. Despite the low abundance of coccoliths, coherent patterns of a changing assemblage composition can be identified. These suggest a consistent paleoceanographic development of highly variable Late Holocene environmental change during the last three millennia. Phases of decreased upwelling in the Benguela Upwelling System are indicated by elevated abundances of Florisphaera profunda alongside reduced occurrence of Coccolithus pelagicus and C. braarudii from 2.25–2.00ka BP, ~ 1.00ka BP and during the last 200 years, also accompanied by a reduced species diversity. Sea surface temperatures estimated with a Gephyrocapsa-based transfer function are in the order of 18–20°C. These phases are intersected by periods of colder sea surface temperatures of 16–17°C and increased productivity, as indicated by an opposing trend for the aforementioned species. Given the climatological and oceanographical complexity of the area, deciphering a single driving mechanism for these changes proves difficult. Synchronous changes in the Antarctic sea ice extent, however, give credit to the conceptual model of latitudinal migration of the westerly wind belt and its interaction with the south-easterly trade winds as an important driver for oceanographic changes in the area.","PeriodicalId":186533,"journal":{"name":"Journal of Nannoplankton Research","volume":"108 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117277798","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Phylogeny of coccolithophores and the evolution of calcification.","authors":"J. Young, C. Billard, P. Bown, L. Cros, S. Davis, M. Geisen, M. Kawachi, Steve Mann, L. Medlin, I. Probert, A. G. Saez","doi":"10.58998/jnr2296","DOIUrl":"https://doi.org/10.58998/jnr2296","url":null,"abstract":"","PeriodicalId":186533,"journal":{"name":"Journal of Nannoplankton Research","volume":"2018 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121335805","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cyclagelosphaera wiedmannii new species, a marker for the Callovian.","authors":"V. Reale, S. Monechi","doi":"10.58998/jnr2207","DOIUrl":"https://doi.org/10.58998/jnr2207","url":null,"abstract":"During a biostratigraphic study of Middle-Upper Jurassic calcareous nannofossils, several circular placoliths with a circular central area were observed. These placoliths are similar to Cyc/agelosphaera deflandrei (Manivit, 1966) Roth 1973 in shield structure and optical properties, but are not as large, and have a different stratigraphic range (Callovian). Because of the different strati graphic range and morphological features it is described here as a new species: Cyclagelosphaera wiedmannii . Moshkovitz & Ehrlich ( 1987) in a short note summarize and elucidate the taxonomic problems and distribution of Watznaueria manivitae Bukry 1973; they define a neotype for W. manivitae and describe it as an elliptical to sub-elliptical placolith with an elliptical or sub-elliptical central area. In the light microscope, between crossed nicols, the species is easily recognized by its high birefringence colours. Large high birefringence circular placoliths with a circular central area are instead referred to C. dejlandre i. Unfortunately, due to systematic confusion, the strati graphic ranges of these forms is not well known; Moshkovitz and Ehrlich ( 1987) suggested from literature data and their observ.iltions a range from Callovian to Berrasian for W. manivitae and ?Kimmeridgianffithonian upwards for C. dejlandrei. Recent biostratigraphic studies in France and Italy show that the FO of W. manivitae is older than Callovian: this event has been recognized in the Lower Bajocian in the Digne area (Erba 1990) and in the Aalenian in the Umbria Marche Basin (Reale et al. 1992). The last occurrence of W. manivitae is still uncertain. During the examination ofDSDP Hole 534A(BlakeBahamas Basin), we found in the lower samples circular placoliths with circular central areas and high birefringence colours, that could be related to C. dejlandrei . However, these placoliths have a smaller size (8-9 Jlm) compared with the original description of Manivit ( 1966); total diameter 12 Jlm; diameter of proximal shield 10 Jlm. Also they have a restricted strati graphic range, being confined to the Callovian. The different morphological features and the different stratigraphic range has allowed us to define the new species C. wiedmannii. In order. to constrain the strati graphic range, welldated ammonite samples .have been investigated. In the Quissac section, SE France (Bouder et al., 1993), the FO was found at the base of the macrocephalus Zone in the Lower Callovian. ThefirstoccurrenceofC. wiedmanniihasbeenalso recognized in the lower part ofDSDP Hole 534A (127-2, 30-31cm). Thiseventallowsus to assign an Early Callovian age to the base of the Hole 534A. an older age than previously reported by Roth ( 1983 ). The LO was recognized at DSDP Hole 534A just before the FO of Stephano/ithion bigotii maximum, an event calibrated to the Upper Callovian by Bown et al. (1988) and Gardin, ( 1993 pers. comm.). The FO and LO of C. wiedmannii have been also found in other sections: in the ","PeriodicalId":186533,"journal":{"name":"Journal of Nannoplankton Research","volume":"40 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125113740","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Validation of Homozygosphaera halldalii.","authors":"K. Gaarder","doi":"10.58998/nina2097","DOIUrl":"https://doi.org/10.58998/nina2097","url":null,"abstract":"","PeriodicalId":186533,"journal":{"name":"Journal of Nannoplankton Research","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125379194","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Nannoplankton taxonomy and the International Code of Nomenclature for algae, fungi, and plants (ICN).","authors":"R. Jordan","doi":"10.58998/jnr2137","DOIUrl":"https://doi.org/10.58998/jnr2137","url":null,"abstract":"In 2012, the International Code of Nomenclature for algae, fungi, and plants was published, which has ramifications for nannoplankton workers. The main changes that are relevant to us are: 1) certain forms of electronic publication are now acceptable, 2) English instead of Latin may now be used in descriptions and diagnoses of extant organisms, and 3) the morphotaxon concept for fossil plants and algae has been abandoned. Furthermore, names of genera based on extant types now have priority over those based on fossil types. This may cause a potential problem in the future for at least four genera with fossil types: Cruciplacolithus and Reticulofenestra (nannoplankton) and Dictyocha and Stephanocha (silicoflagellates). Herein, some of the rules and recommendations are explained, with nannoplankton and silicoflagellate examples.","PeriodicalId":186533,"journal":{"name":"Journal of Nannoplankton Research","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125565809","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A new perspective of the central structure and the alignment of neogene discoasters.","authors":"O. Rui, A. Gama, O. Varol","doi":"10.58998/jnr2074","DOIUrl":"https://doi.org/10.58998/jnr2074","url":null,"abstract":"With few exceptions, Neogene star-like Discoasters exhibit diamond shaped distal depressions (concavities) on radial elements. The concavities and the sutures they form appear to be primary morphological features observed on the distal side of the Discoaster. The concavities, sutures and the inner end of rays, bend and extend outwards to form processes (distal bosses). On the proximal side, the boss (when present), results from the inward merging of proximal ridges. Bosses are an integral part of the individual ray element and thus are not often observed in isolation within the sedimentary record. Herein we discuss the relationship between proximal and distal features observed on the centre of star-like Discoasters and speculate these may have been joined on 'male/female' structures comprising two or more Discoasters; on these structures the Discoasters rays are not aligned and seem offset or rotated. This offsetting suggests a mechanism that facilitates the interlocking and possibly the movement between proximal and distal structures.","PeriodicalId":186533,"journal":{"name":"Journal of Nannoplankton Research","volume":"C-18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126767646","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Tegulalithus, a new genus of Early Cretaceous calcareous nannofossils.","authors":"J. Crux","doi":"10.58998/nina2067","DOIUrl":"https://doi.org/10.58998/nina2067","url":null,"abstract":"","PeriodicalId":186533,"journal":{"name":"Journal of Nannoplankton Research","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126965534","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An improved filtering technique for calculation of calcareous nannofossil accumualtion rates.","authors":"H. Okada","doi":"10.58998/jnr2188","DOIUrl":"https://doi.org/10.58998/jnr2188","url":null,"abstract":"","PeriodicalId":186533,"journal":{"name":"Journal of Nannoplankton Research","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114383469","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}