Pub Date : 2020-05-20DOI: 10.1344/geologicaacta2020.18.7
Z. Larena, C. Arenas, J. Baceta, X. Murelaga, Oier Suárez-Hernando
Stratigraphic and sedimentological study of distal alluvial and lacustrine deposits in the Plana de la Negra-Sancho Abarca area (western-central Ebro Basin, NE Iberia) within the early and middle Miocene allows five main lithofacies to be characterized and mapped within two tectosedimentary units, construction of a sedimentary facies model and discussion on allogenic controls on sedimentation. In this area, the boundary between tectosedimentary units T5 and T6 appears to be conformable and is marked by the change from dominant clastics to carbonates. Correlation of the studied outcrops with nearby sections that already had magnetostratigraphic and biostratigraphic data allows the studied succession to be dated from C5Dr to C5Cn (Burdigalian-Langhian), placing the boundary T5/T6 at ca. 16.1-16.05Ma. Seven vertical facies sequences document deposition of distal alluvial clastics and palustrine and lacustrine carbonates. Sandstones and mudstones represent low-sinuosity channels and lateral and terminal splays by unconfined flows runnig across the alluvial plain, associated to the Pyrenean-derived Luna fluvial system. The carbonates contain charophytes, ostracods, bivalves and gastropods, indicating deposition in 2-4m deep lakes. Laminated carbonate facies record reworking of shore carbonates and the influx fine-siliciclastic sediment offshore. Abundant bioturbation and desiccation features indicate episodic submergence and subaerial exposure. Four main episodes of alluvial and associated palustrine/lacustrine facies belt shifts are identified. Alluvial deposition in the studied T5 unit is related to low lake level conditions, rather than to a Pyrenean uplift. The maximum extent of the freshwater carbonates occur at the base of unit T6. This is consistent with conditions of increasing humidity of the Middle Miocene Climatic Optimum.
通过对Plana de la Negra-Sancho Abarca地区(伊比利亚东北部埃布罗盆地中西部)早中新世和中中新世远端冲积和湖泊沉积的地层学和沉积学研究，在两个构造沉积单元内对5个主要岩相进行了表征和绘制，建立了沉积相模型，并讨论了沉积的异体控制作用。该区T5和T6构造沉积单元的界线较为整合，主要由碎屑岩为主向碳酸盐岩为主转变。将所研究的露头与附近已有磁地层和生物地层资料的剖面进行对比，可以将所研究的演替期定在C5Dr至C5Cn (burdigian - langhian)，将T5/T6界定在约16.1-16.05Ma。7个垂向相序列记录了远端冲积碎屑和滩湖碳酸盐的沉积。砂岩和泥岩代表了冲积平原上不受限制的水流形成的低弯曲度河道和侧向和末端的带状地带，与比利牛斯山脉衍生的Luna河系有关。碳酸盐中含有叶绿类、介形虫、双壳类和腹足类，表明沉积在2 ~ 4m深的湖泊中。层状碳酸盐相记录了海岸碳酸盐的改造和近海细硅质沉积的流入。丰富的生物扰动和干燥特征表明间歇性淹没和陆上暴露。确定了四个主要的冲积带和相关的湖湖相带移动期。研究的T5单元的冲积物沉积与低湖面条件有关，而不是与比利牛斯山脉隆起有关。淡水碳酸盐岩的最大范围出现在T6单元的底部。这与中新世中期气候适宜期湿度增加的条件是一致的。
{"title":"Stratigraphy and sedimentology of distal-alluvial and lacustrine deposits of the western-central Ebro Basin (NE Iberia) reflecting the onset of the middle Miocene Climatic Optimum","authors":"Z. Larena, C. Arenas, J. Baceta, X. Murelaga, Oier Suárez-Hernando","doi":"10.1344/geologicaacta2020.18.7","DOIUrl":"https://doi.org/10.1344/geologicaacta2020.18.7","url":null,"abstract":"Stratigraphic and sedimentological study of distal alluvial and lacustrine deposits in the Plana de la Negra-Sancho Abarca area (western-central Ebro Basin, NE Iberia) within the early and middle Miocene allows five main lithofacies to be characterized and mapped within two tectosedimentary units, construction of a sedimentary facies model and discussion on allogenic controls on sedimentation. In this area, the boundary between tectosedimentary units T5 and T6 appears to be conformable and is marked by the change from dominant clastics to carbonates. Correlation of the studied outcrops with nearby sections that already had magnetostratigraphic and biostratigraphic data allows the studied succession to be dated from C5Dr to C5Cn (Burdigalian-Langhian), placing the boundary T5/T6 at ca. 16.1-16.05Ma. Seven vertical facies sequences document deposition of distal alluvial clastics and palustrine and lacustrine carbonates. Sandstones and mudstones represent low-sinuosity channels and lateral and terminal splays by unconfined flows runnig across the alluvial plain, associated to the Pyrenean-derived Luna fluvial system. The carbonates contain charophytes, ostracods, bivalves and gastropods, indicating deposition in 2-4m deep lakes. Laminated carbonate facies record reworking of shore carbonates and the influx fine-siliciclastic sediment offshore. Abundant bioturbation and desiccation features indicate episodic submergence and subaerial exposure. Four main episodes of alluvial and associated palustrine/lacustrine facies belt shifts are identified. Alluvial deposition in the studied T5 unit is related to low lake level conditions, rather than to a Pyrenean uplift. The maximum extent of the freshwater carbonates occur at the base of unit T6. This is consistent with conditions of increasing humidity of the Middle Miocene Climatic Optimum.","PeriodicalId":55107,"journal":{"name":"Geologica Acta","volume":"1 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2020-05-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"66404843","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-05-19DOI: 10.1344/geologicaacta2020.18.8
J. Serra-Kiel, V. Vicedo, J. Baceta, G. Bernaola, A. Robador
A taxonomic study of the larger foraminifera found in Paleocene rocks from the Pyrenean basin has led to the description of sixty taxa including two new species: Alveolina korresensis and Valvulineria bacetai . In this work, we present a chronostratigraphic recalibration of the Paleocene Shallow Benthic Zones (SBZ 1 to SBZ 4) based on correlation with calcareous nannofossil and planktic foraminifera biozones, all integrated within the stratigraphic framework of Paleocene platform to basin depositional sequences established for the whole Pyrenean domain. The samples were collected in autochtonous and parautochtonous deposits from ten key shallow platform stratigraphic sections, representative from coastal to platform margin depositional settings. The results from two base of slope sections with numerous intercalations of calcareous turbidites with penecontemporaneous platform-derived biota have been integrated in the study. The regional chronostratigraphic framework is derived from magneto-biochronological studies carried out in the Zumaia section, global reference section for the Danian-Selandian and Selandian-Thanertian GSSPs. The new calibration of the Paleocene SBZs is summarized as follows. The SBZ 1 is constrained to the first 1.09 m.y. of the Paleocene; this first Paleogene biozone lacks distinct larger foraminifera biomarkers and thus is defined by an association of non-exclusive taxa composed of Valvulineria patalaensis , Stomatorbina ? binkhorsti , P .? antiqua and Bangiana hanseni . The SBZ 2 now appears as the biozone encompassing most of the Danian stage (from ca. 64.91 m.y. to 61.6 m.y.), and is characterized by the association of Haymanella elongata , Haymanella paleocenica , Kayseriella decastroi , Rotospirella conica , Pyrenerotalia depressa , Elazigina dienii and Paralockhartia eos . The SBZ 2-SBZ 3 boundary coincides with the base of the Selandian stage (ca. 61.6 m.y.). The SBZ 3 biozone is defined by Glomalveolina primaeva , Periloculina slovenica , Vania anatolica , Coskinon rajkae , Fallotella alavensis , Cribrobulimina carniolica , Miscellanea yvettae , Miscellanea juliettae , Miscellanites primitivus , Miscellanites minutus , Ranikothalia soldadensis , Nummulites heberti and Discocyclina seunesi . The SBZ 3-SBZ 4 boundary is now ascribed to ca. 57.2 m.y. The SBZ 4 biozone appears characterized by Glomalveolina levis , Alveolina korresensis , Hottingerina lukasi , Daviesina garumnensis , Assilina yvettae , Assilina azilensis and Nummulites catari . The SBZ 4-SBZ 5 boundary is placed at the Paleocene-Eocene boundary event (ca. 56.0 m.y.).
{"title":"Paleocene Larger Foraminifera from the Pyrenean Basin with a recalibration of the Paleocene Shallow Benthic Zones","authors":"J. Serra-Kiel, V. Vicedo, J. Baceta, G. Bernaola, A. Robador","doi":"10.1344/geologicaacta2020.18.8","DOIUrl":"https://doi.org/10.1344/geologicaacta2020.18.8","url":null,"abstract":"A taxonomic study of the larger foraminifera found in Paleocene rocks from the Pyrenean basin has led to the description of sixty taxa including two new species: Alveolina korresensis and Valvulineria bacetai . In this work, we present a chronostratigraphic recalibration of the Paleocene Shallow Benthic Zones (SBZ 1 to SBZ 4) based on correlation with calcareous nannofossil and planktic foraminifera biozones, all integrated within the stratigraphic framework of Paleocene platform to basin depositional sequences established for the whole Pyrenean domain. The samples were collected in autochtonous and parautochtonous deposits from ten key shallow platform stratigraphic sections, representative from coastal to platform margin depositional settings. The results from two base of slope sections with numerous intercalations of calcareous turbidites with penecontemporaneous platform-derived biota have been integrated in the study. The regional chronostratigraphic framework is derived from magneto-biochronological studies carried out in the Zumaia section, global reference section for the Danian-Selandian and Selandian-Thanertian GSSPs. The new calibration of the Paleocene SBZs is summarized as follows. The SBZ 1 is constrained to the first 1.09 m.y. of the Paleocene; this first Paleogene biozone lacks distinct larger foraminifera biomarkers and thus is defined by an association of non-exclusive taxa composed of Valvulineria patalaensis , Stomatorbina ? binkhorsti , P .? antiqua and Bangiana hanseni . The SBZ 2 now appears as the biozone encompassing most of the Danian stage (from ca. 64.91 m.y. to 61.6 m.y.), and is characterized by the association of Haymanella elongata , Haymanella paleocenica , Kayseriella decastroi , Rotospirella conica , Pyrenerotalia depressa , Elazigina dienii and Paralockhartia eos . The SBZ 2-SBZ 3 boundary coincides with the base of the Selandian stage (ca. 61.6 m.y.). The SBZ 3 biozone is defined by Glomalveolina primaeva , Periloculina slovenica , Vania anatolica , Coskinon rajkae , Fallotella alavensis , Cribrobulimina carniolica , Miscellanea yvettae , Miscellanea juliettae , Miscellanites primitivus , Miscellanites minutus , Ranikothalia soldadensis , Nummulites heberti and Discocyclina seunesi . The SBZ 3-SBZ 4 boundary is now ascribed to ca. 57.2 m.y. The SBZ 4 biozone appears characterized by Glomalveolina levis , Alveolina korresensis , Hottingerina lukasi , Daviesina garumnensis , Assilina yvettae , Assilina azilensis and Nummulites catari . The SBZ 4-SBZ 5 boundary is placed at the Paleocene-Eocene boundary event (ca. 56.0 m.y.).","PeriodicalId":55107,"journal":{"name":"Geologica Acta","volume":"18 1","pages":"1-69"},"PeriodicalIF":1.5,"publicationDate":"2020-05-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41812967","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-04-03DOI: 10.1344/geologicaacta2020.18.6
C. Soriano
In the coming years the Anthropocene will be likely submitted to formalization by the Anthropocene Working Group as a chronostratigraphic unit of the Geologic Time Scale. This has generated an increasing debate among detractors and defenders of its formalization in general, and of the proposal by the Anthropocene Working Group in particular. Here, the main issues regarding the Geologic Time Scale and the rules to formalize units, the empirical data supporting the Anthropocene formalization and the critiques to formalize it are critically reviewed. The procedure to formalize the Anthropocene is not dissimilar from those of the other units of the Geologic Time Scale and has been essentially based on stratigraphic and geologic criteria. Following the recommendation of the Anthropocene Working Group and based on the empirical evidence on the Anthropocene as it is expressed in strata and, more important, on the immanent and structural link between the Anthropocene and the reproduction of capital, it is proposed to define Capitalian as a Stage of the Anthropocene Epoch. In this way, a truly comprehensive understanding of the Earth history is obtained, which comprises the ultimate causes of the ongoing planetary transformation and its stratatigraphic expression.
{"title":"On the Anthropocene formalization and the proposal by the Anthropocene Working Group","authors":"C. Soriano","doi":"10.1344/geologicaacta2020.18.6","DOIUrl":"https://doi.org/10.1344/geologicaacta2020.18.6","url":null,"abstract":"In the coming years the Anthropocene will be likely submitted to formalization by the Anthropocene Working Group as a chronostratigraphic unit of the Geologic Time Scale. This has generated an increasing debate among detractors and defenders of its formalization in general, and of the proposal by the Anthropocene Working Group in particular. Here, the main issues regarding the Geologic Time Scale and the rules to formalize units, the empirical data supporting the Anthropocene formalization and the critiques to formalize it are critically reviewed. The procedure to formalize the Anthropocene is not dissimilar from those of the other units of the Geologic Time Scale and has been essentially based on stratigraphic and geologic criteria. Following the recommendation of the Anthropocene Working Group and based on the empirical evidence on the Anthropocene as it is expressed in strata and, more important, on the immanent and structural link between the Anthropocene and the reproduction of capital, it is proposed to define Capitalian as a Stage of the Anthropocene Epoch. In this way, a truly comprehensive understanding of the Earth history is obtained, which comprises the ultimate causes of the ongoing planetary transformation and its stratatigraphic expression.","PeriodicalId":55107,"journal":{"name":"Geologica Acta","volume":"18 1","pages":"1-10"},"PeriodicalIF":1.5,"publicationDate":"2020-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48263511","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-03-09DOI: 10.1344/geologicaacta2020.18.5
C. Cruz, H. Sant’Ovaia, F. Noronha
Northern Portugal is characterized by the occurrence of numerous W hydrothermal deposits spatially associated with granites. The primary goal of this work is to establish a relationship between the magnetic behavior of the granites and the redox conditions during magma genesis, as this can influence the occurrence of mineralizations, namely of W (Mo). To this end, the magnetic mineralogy of the granites of the Lamas de Olo Pluton, a posttectonic pluton in northern Portugal, with associated W (Mo) occurrences was characterized and compared with the magnetic mineralogy of other post-tectonic Variscan plutons. This pluton is composed of different biotite granites: Lamas de Olo, Alto dos Cabecos and Barragem. To better characterize its magnetic behavior, different analytical techniques that complement previous magnetic susceptibility studies were performed. The magnetic mineralogy of Lamas de Olo Pluton was then compared with other post-tectonic Variscan plutons such as the Vila Pouca de Aguiar, Peneda-Geres and Lavadores-Madalena plutons. The presence of magnetite in some of these granites is important because it points to melt-oxidized conditions not commonly found in Iberian Variscan granites. Our study shows that granite areas where magnetite and/or magnetite/ilmenite coexist are important targets for W (Mo) mineralizations. The results indicate that a few plutons have granites with a complex redox history which leads to the formation of magnetite and ilmenite.
葡萄牙北部的特点是出现了大量与花岗岩空间相关的W热液矿床。这项工作的主要目标是建立花岗岩的磁性行为与岩浆生成过程中的氧化还原条件之间的关系，因为这会影响矿化作用的发生，即W（Mo）的发生。为此，对葡萄牙北部构造后深成岩体Lamas de Olo Pluton花岗岩的磁性矿物学进行了表征，并与其他构造后华力西深成岩体的磁性矿物学相比较。该深成岩体由不同的黑云母花岗岩组成：Lamas de Olo、Alto dos Cabecos和Barragem。为了更好地表征其磁性行为，采用了不同的分析技术来补充以前的磁化率研究。然后将Lamas de Olo Pluton的磁性矿物学与其他后构造华力西深成岩体进行了比较，如Vila Pouca de Aguiar、Peneda Geres和Lavadores Madalena深成岩体。其中一些花岗岩中磁铁矿的存在很重要，因为它表明了伊比利亚华力西期花岗岩中不常见的熔融氧化条件。我们的研究表明，磁铁矿和/或磁铁矿/钛铁矿共存的花岗岩区域是W（Mo）矿化的重要目标。结果表明，少数深成岩体具有复杂的氧化还原历史，导致磁铁矿和钛铁矿的形成。
{"title":"Magnetic mineralogy of Variscan granites from northern Portugal: an approach to their petrogenesis and metallogenic potential","authors":"C. Cruz, H. Sant’Ovaia, F. Noronha","doi":"10.1344/geologicaacta2020.18.5","DOIUrl":"https://doi.org/10.1344/geologicaacta2020.18.5","url":null,"abstract":"Northern Portugal is characterized by the occurrence of numerous W hydrothermal deposits spatially associated with granites. The primary goal of this work is to establish a relationship between the magnetic behavior of the granites and the redox conditions during magma genesis, as this can influence the occurrence of mineralizations, namely of W (Mo). To this end, the magnetic mineralogy of the granites of the Lamas de Olo Pluton, a posttectonic pluton in northern Portugal, with associated W (Mo) occurrences was characterized and compared with the magnetic mineralogy of other post-tectonic Variscan plutons. This pluton is composed of different biotite granites: Lamas de Olo, Alto dos Cabecos and Barragem. To better characterize its magnetic behavior, different analytical techniques that complement previous magnetic susceptibility studies were performed. The magnetic mineralogy of Lamas de Olo Pluton was then compared with other post-tectonic Variscan plutons such as the Vila Pouca de Aguiar, Peneda-Geres and Lavadores-Madalena plutons. The presence of magnetite in some of these granites is important because it points to melt-oxidized conditions not commonly found in Iberian Variscan granites. Our study shows that granite areas where magnetite and/or magnetite/ilmenite coexist are important targets for W (Mo) mineralizations. The results indicate that a few plutons have granites with a complex redox history which leads to the formation of magnetite and ilmenite.","PeriodicalId":55107,"journal":{"name":"Geologica Acta","volume":"18 1","pages":"1-20"},"PeriodicalIF":1.5,"publicationDate":"2020-03-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46550374","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-02-18DOI: 10.1344/geologicaacta2020.18.4
F. Ortí, J. Guimerà, A. Götz
The present study provides new data of the Middle-Upper Triassic successions and their deformation in the eastern Iberian Chain, where contractional tectonics during the Cenozoic disrupted this Mediterranean type of Triassic rocks. The succession, divided into three Muschelkalk units, was studied in the Alt Palancia area. In this area, both the lower and upper Muschelkalk consist of two main types of sub-units, those made up of carbonate and those of carbonate-marl alternation. The marked similarity observed between the evaporite units of the middle Muschelkalk and the Keuper humpers their unambiguous discrimination in the field. The integration of geological mapping, stratigraphic logging, palynological dating and gypsum isotope analysis carried out provided that: i) a change in the structural style, facies, and depositional thickness occurs across a SW to NE transect at both sides of the Espina-Espada Fault, providing evidence for the extensional activity of this major structure; ii) palynological data assign Anisian age to the Rot facies and the lower and the middle Muschelkalk units, and Ladinian to the upper Muschelkalk unit; iii) the δ 34 SCDT and δ 18 OSMOW values of gypsum reveal as a useful proxy to discriminate between the middle Muschelkalk (δ 34 S: 15.6 to 17.8‰) and the Keuper (δ 34 S: 14 to 15.5‰) units; and iv) the isotopic signature also helps to identify clayey-marly gypsiferous outcrops made up of the two evaporite facies due to tectonic juxtaposition. These results confirm the Mediterranean type of Triassic rocks for the entire Alt Palancia and other areas to the NE. This multidisciplinary approach reveals as a robust methodology to study Triassic basins in Iberia and to other geological domains where the carbonate-evaporite successions have been greatly disrupted by tectonism.
{"title":"Middle-Upper Triassic stratigraphy and structure in the Alt Palància region (eastern Iberian Chain): A multidisciplinary approach","authors":"F. Ortí, J. Guimerà, A. Götz","doi":"10.1344/geologicaacta2020.18.4","DOIUrl":"https://doi.org/10.1344/geologicaacta2020.18.4","url":null,"abstract":"The present study provides new data of the Middle-Upper Triassic successions and their deformation in the eastern Iberian Chain, where contractional tectonics during the Cenozoic disrupted this Mediterranean type of Triassic rocks. The succession, divided into three Muschelkalk units, was studied in the Alt Palancia area. In this area, both the lower and upper Muschelkalk consist of two main types of sub-units, those made up of carbonate and those of carbonate-marl alternation. The marked similarity observed between the evaporite units of the middle Muschelkalk and the Keuper humpers their unambiguous discrimination in the field. The integration of geological mapping, stratigraphic logging, palynological dating and gypsum isotope analysis carried out provided that: i) a change in the structural style, facies, and depositional thickness occurs across a SW to NE transect at both sides of the Espina-Espada Fault, providing evidence for the extensional activity of this major structure; ii) palynological data assign Anisian age to the Rot facies and the lower and the middle Muschelkalk units, and Ladinian to the upper Muschelkalk unit; iii) the δ 34 SCDT and δ 18 OSMOW values of gypsum reveal as a useful proxy to discriminate between the middle Muschelkalk (δ 34 S: 15.6 to 17.8‰) and the Keuper (δ 34 S: 14 to 15.5‰) units; and iv) the isotopic signature also helps to identify clayey-marly gypsiferous outcrops made up of the two evaporite facies due to tectonic juxtaposition. These results confirm the Mediterranean type of Triassic rocks for the entire Alt Palancia and other areas to the NE. This multidisciplinary approach reveals as a robust methodology to study Triassic basins in Iberia and to other geological domains where the carbonate-evaporite successions have been greatly disrupted by tectonism.","PeriodicalId":55107,"journal":{"name":"Geologica Acta","volume":"18 1","pages":"1-26"},"PeriodicalIF":1.5,"publicationDate":"2020-02-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41388210","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-02-07DOI: 10.1344/geologicaacta2020.18.3
C. Paul, J. C. Gutiérrez-Marco
Restudy of an Ordovician diploporite specimen from the Middle Ordovician of central Spain reveals that the species ‘Calix’ inornatus MELENDEZ has four ambulacra, each with two equal facets, an oval hydropore and a smooth thecal surface. In contrast, the type species of Calix has four ambulacra, each with four facets added in a clockwise direction during growth, a trilobed hydropore, and a theca with spiny plates. Other aristocystitid genera with four ambulacra have one facet per ambulacrum. ‘Calix’ inornatus differs from all other aristocystitid genera and warrants a new generic name, for which we propose Enodicalix .
{"title":"Enodicalix (Diploporita, Aristocystitidae): A new echinoderm genus from the Middle Ordovician of Spain","authors":"C. Paul, J. C. Gutiérrez-Marco","doi":"10.1344/geologicaacta2020.18.3","DOIUrl":"https://doi.org/10.1344/geologicaacta2020.18.3","url":null,"abstract":"Restudy of an Ordovician diploporite specimen from the Middle Ordovician of central Spain reveals that the species ‘Calix’ inornatus MELENDEZ has four ambulacra, each with two equal facets, an oval hydropore and a smooth thecal surface. In contrast, the type species of Calix has four ambulacra, each with four facets added in a clockwise direction during growth, a trilobed hydropore, and a theca with spiny plates. Other aristocystitid genera with four ambulacra have one facet per ambulacrum. ‘Calix’ inornatus differs from all other aristocystitid genera and warrants a new generic name, for which we propose Enodicalix .","PeriodicalId":55107,"journal":{"name":"Geologica Acta","volume":"18 1","pages":"1-8"},"PeriodicalIF":1.5,"publicationDate":"2020-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45303717","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-01-29DOI: 10.1344/geologicaacta2020.18.2
G. Ripp, I. Izbrodin, M. Rampilov, A. Tomilenko, E. Lastochkin, V. F. Posokhov
The paper presents the mineralogical and geochemical characteristics of two groups of hydrothermal rocks and their relation with subalkaline granites of the Ermakovskoe deposit. The first group includes fluorite-phenakite-bertrandite ore bodies, occurring outside the granite massif. The second group is presented by silicification bodies with sulfates, phosphates, kaolinite, muscovite and hematite. It bears REE (rare earth elements) mineralization (monazite, florencite, xenotime) and occurs within the massif. Our research included isotopic analyses of Sr, Nd and O, studies of trace, including rare-earth element compositions and age determination (U-Pb) of apatite from F-Be ores. Geochemical and isotopic studies are not according with relation between F-Be ores and granites. This is proven by the absence of Be-mineralization in granites and schlieren pegmatites, and a sharp difference in composition of their fluid phases. A reductive fluid specification forming F-Be ores (containing CH 4 , H 2 , N 2 , CO 2 and H 2 S), contrasts sharply with fluid specification of granites. The granites are characterized by high oxygen fugacity, due to ferrous iron, sulfates and phosphates. Besides isotopic composition of oxygen in quartz (7.4 and 5.1‰ δ 18 О V-SMOW respectively), initial Sr ratios (0.7056-0.7065 and 0.707-0.709 respectively) and REE compositions are different.
{"title":"Relationship of F-Be mineralization to granites and syenites at the Ermakovka deposit (Western Transbaikalia)","authors":"G. Ripp, I. Izbrodin, M. Rampilov, A. Tomilenko, E. Lastochkin, V. F. Posokhov","doi":"10.1344/geologicaacta2020.18.2","DOIUrl":"https://doi.org/10.1344/geologicaacta2020.18.2","url":null,"abstract":"The paper presents the mineralogical and geochemical characteristics of two groups of hydrothermal rocks and their relation with subalkaline granites of the Ermakovskoe deposit. The first group includes fluorite-phenakite-bertrandite ore bodies, occurring outside the granite massif. The second group is presented by silicification bodies with sulfates, phosphates, kaolinite, muscovite and hematite. It bears REE (rare earth elements) mineralization (monazite, florencite, xenotime) and occurs within the massif. Our research included isotopic analyses of Sr, Nd and O, studies of trace, including rare-earth element compositions and age determination (U-Pb) of apatite from F-Be ores. Geochemical and isotopic studies are not according with relation between F-Be ores and granites. This is proven by the absence of Be-mineralization in granites and schlieren pegmatites, and a sharp difference in composition of their fluid phases. A reductive fluid specification forming F-Be ores (containing CH 4 , H 2 , N 2 , CO 2 and H 2 S), contrasts sharply with fluid specification of granites. The granites are characterized by high oxygen fugacity, due to ferrous iron, sulfates and phosphates. Besides isotopic composition of oxygen in quartz (7.4 and 5.1‰ δ 18 О V-SMOW respectively), initial Sr ratios (0.7056-0.7065 and 0.707-0.709 respectively) and REE compositions are different.","PeriodicalId":55107,"journal":{"name":"Geologica Acta","volume":"18 1","pages":"1-13"},"PeriodicalIF":1.5,"publicationDate":"2020-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43445893","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-01-29DOI: 10.1344/geologicaacta2020.18.1
E. Shcherbinina, A. Iakovleva, Y. Gavrilov, O. Golovanova, N. Muzylev
The lower Eocene sediments from the classical Paleogene section exposed along the Kheu River, northern Caucasus, southern Russia are here studied. This ca. 50m thick succession is lithologically contrasting: the lower and upper parts are composed by soft marls separated by a thick Radiolaria-rich unit of non-calcareous and low-calcareous mudstones with intercalations of compact cherty layers. According to nannofossil and dinocyst biostratigraphy, the unique intercalation of Total Organic Carbon (TOC)-rich sediment (sapropelitic bed) in the lower part of the lower Eocene correspond to the Paleocene-Eocene Thermal Maximum (PETM) and a series of sapropelitic interlayers in the upper marly part of the lower Eocene succession correlates with the Early Eocene Climatic Optimum (EECO). The study of nannofossil and dinocyst assemblages enabled detailed zonal subdivision and first-order calibration of nannofossil and dinocyst bio-events during this time-span. The studied interval of the section embraces the complete succession of nannofossil zones NP9-NP13 of Martini, 1971, CP8-CP11 of Okada and Bukry, 1980 and CNP11-CNE5 of Agnini et al., 2014. By means of dinocyst stratigraphy, the succession of Apectodinium hyperacanthum, Axiodinium augustum, Deflandrea oebisfeldensis, Dracodinium astra, Stenodinium meckelfeldense, Dracodinium varielongitudum, Ochetodinium romanum/Samlandia chlamydophora and Areosphaeridium diktyoplokum zones are identified in the Ypresian part of the Kheu section.
{"title":"Lower Eocene sedimentary succession and microfossil biostratigraphy in the central northern Caucasus basin","authors":"E. Shcherbinina, A. Iakovleva, Y. Gavrilov, O. Golovanova, N. Muzylev","doi":"10.1344/geologicaacta2020.18.1","DOIUrl":"https://doi.org/10.1344/geologicaacta2020.18.1","url":null,"abstract":"The lower Eocene sediments from the classical Paleogene section exposed along the Kheu River, northern Caucasus, southern Russia are here studied. This ca. 50m thick succession is lithologically contrasting: the lower and upper parts are composed by soft marls separated by a thick Radiolaria-rich unit of non-calcareous and low-calcareous mudstones with intercalations of compact cherty layers. According to nannofossil and dinocyst biostratigraphy, the unique intercalation of Total Organic Carbon (TOC)-rich sediment (sapropelitic bed) in the lower part of the lower Eocene correspond to the Paleocene-Eocene Thermal Maximum (PETM) and a series of sapropelitic interlayers in the upper marly part of the lower Eocene succession correlates with the Early Eocene Climatic Optimum (EECO). The study of nannofossil and dinocyst assemblages enabled detailed zonal subdivision and first-order calibration of nannofossil and dinocyst bio-events during this time-span. The studied interval of the section embraces the complete succession of nannofossil zones NP9-NP13 of Martini, 1971, CP8-CP11 of Okada and Bukry, 1980 and CNP11-CNE5 of Agnini et al., 2014. By means of dinocyst stratigraphy, the succession of Apectodinium hyperacanthum, Axiodinium augustum, Deflandrea oebisfeldensis, Dracodinium astra, Stenodinium meckelfeldense, Dracodinium varielongitudum, Ochetodinium romanum/Samlandia chlamydophora and Areosphaeridium diktyoplokum zones are identified in the Ypresian part of the Kheu section.","PeriodicalId":55107,"journal":{"name":"Geologica Acta","volume":"18 1","pages":"1-15"},"PeriodicalIF":1.5,"publicationDate":"2020-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47500171","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-11-08DOI: 10.1344/geologicaacta2019.17.10
I. Urraza, S. Delpino, L. E. Grecco
Amphibolites included in the metapelitic sequence and as xenoliths in intrusive magmatic rocks outcropping in the southern sector of the Alumine Igneous-Metamorphic Complex (AIMC), Neuquen, Argentina, are studied in detail in order to determine their origin and their subsequent metamorphic evolution. Field evidence and wholerock geochemistry indicate that these rocks were derived from a Mid-Ocean Ridge Basalt (MORB)-type protolith, and were accreted as tectonic slices into the metapelitic sequence that mainly formed the basal accretionary prism associated with a pre-Andean SW-NE subduction setting. Phase relationships, geochemistry of mineral assemblages and geothermobarometry indicate the presence of at least two metamorphic events (M 1 1.9−3.9kbar, 677−745oC and M 2 6.4kbar, 723oC) framed in a counterclockwise P-T path, comparable to those previously determined for the metapelitic country-rocks and metatroctolites outcropping in the same sector of the AIMC. Based on regional correlations and the agreement in the petrological, geochemical, geochronological and structural characteristics, we suggest that the MORB-derived Norquinco amphibolites and neighboring aluminous metasedimentary basement rocks of the AIMC belong to the eastern prolongation of the Western Series of the Coastal Accretionary Complex of Central Chile in west-central Argentina territory.
{"title":"MORB-derived amphibolites in the Paleozoic basement of the Aluminé Igneous-Metamorphic Complex,.","authors":"I. Urraza, S. Delpino, L. E. Grecco","doi":"10.1344/geologicaacta2019.17.10","DOIUrl":"https://doi.org/10.1344/geologicaacta2019.17.10","url":null,"abstract":"Amphibolites included in the metapelitic sequence and as xenoliths in intrusive magmatic rocks outcropping in the southern sector of the Alumine Igneous-Metamorphic Complex (AIMC), Neuquen, Argentina, are studied in detail in order to determine their origin and their subsequent metamorphic evolution. Field evidence and wholerock geochemistry indicate that these rocks were derived from a Mid-Ocean Ridge Basalt (MORB)-type protolith, and were accreted as tectonic slices into the metapelitic sequence that mainly formed the basal accretionary prism associated with a pre-Andean SW-NE subduction setting. Phase relationships, geochemistry of mineral assemblages and geothermobarometry indicate the presence of at least two metamorphic events (M 1 1.9−3.9kbar, 677−745oC and M 2 6.4kbar, 723oC) framed in a counterclockwise P-T path, comparable to those previously determined for the metapelitic country-rocks and metatroctolites outcropping in the same sector of the AIMC. Based on regional correlations and the agreement in the petrological, geochemical, geochronological and structural characteristics, we suggest that the MORB-derived Norquinco amphibolites and neighboring aluminous metasedimentary basement rocks of the AIMC belong to the eastern prolongation of the Western Series of the Coastal Accretionary Complex of Central Chile in west-central Argentina territory.","PeriodicalId":55107,"journal":{"name":"Geologica Acta","volume":" ","pages":""},"PeriodicalIF":1.5,"publicationDate":"2019-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47454162","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Andrade, P. Legoinha, Z. Stroynowski, F. Abrantes
Proboscia barboi and Proboscia curvirostris are two important diatom biostratigraphic markers from the high latitudes of the North Pacific and North Atlantic Oceans, dating back to the Pliocene-Pleistocene time. This study analyzes the biostratigraphic events and describes the morphology of P. barboi and P. curvirostris , particularly the morphologic variations of the latter species, based on observations of samples of Core U1340A from the IODP Expedition 323 in the Bering Sea. In Site U1340, the First Occurrence of P. curvirostris is observed at 1.52Ma and its First Common Occurrence at 1.39Ma, where morphologic variations were found abundantly. The Last Occurrence of P. curvirostris was found at 0.33Ma, while P. barboi ’s Last Occurrence is found at 0.67Ma. Based on the morphological similarity and known biostratigraphic distribution, previous authors have assumed that P. curvirostris descends from P. barboi , although this hypothesis is still in debate. At 1.39Ma P. curvirostris shows an increased size and thickness, which is typical of P. barboi , and some specimens display an incipient structure characteristic of P. curvirostris - the secondary spine. This morphology is intermediate between the two species and suggests an evolutionary transition from P. barboi to P. curvirostris . However, P. curvirostris already existed since 1.9Ma in the subarctic indicating that its speciation happened much earlier than 1.39Ma. Furthermore, since P. barboi co-occurs with P. curvirostris in the North Pacific, this evolutionary process was cladogenetic. Besides being evidence for a phylogenetic relationship, the abundant occurrence of intermediate forms at 1.39Ma may constitute a bioevent for a short time interval in the Bering Sea.
{"title":"Morphology, biostratigraphy, and evolution of PliocenePleistocene diatoms Proboscia barboi...","authors":"J. Andrade, P. Legoinha, Z. Stroynowski, F. Abrantes","doi":"10.1344/105.000005518","DOIUrl":"https://doi.org/10.1344/105.000005518","url":null,"abstract":"Proboscia barboi and Proboscia curvirostris are two important diatom biostratigraphic markers from the high latitudes of the North Pacific and North Atlantic Oceans, dating back to the Pliocene-Pleistocene time. This study analyzes the biostratigraphic events and describes the morphology of P. barboi and P. curvirostris , particularly the morphologic variations of the latter species, based on observations of samples of Core U1340A from the IODP Expedition 323 in the Bering Sea. In Site U1340, the First Occurrence of P. curvirostris is observed at 1.52Ma and its First Common Occurrence at 1.39Ma, where morphologic variations were found abundantly. The Last Occurrence of P. curvirostris was found at 0.33Ma, while P. barboi ’s Last Occurrence is found at 0.67Ma. Based on the morphological similarity and known biostratigraphic distribution, previous authors have assumed that P. curvirostris descends from P. barboi , although this hypothesis is still in debate. At 1.39Ma P. curvirostris shows an increased size and thickness, which is typical of P. barboi , and some specimens display an incipient structure characteristic of P. curvirostris - the secondary spine. This morphology is intermediate between the two species and suggests an evolutionary transition from P. barboi to P. curvirostris . However, P. curvirostris already existed since 1.9Ma in the subarctic indicating that its speciation happened much earlier than 1.39Ma. Furthermore, since P. barboi co-occurs with P. curvirostris in the North Pacific, this evolutionary process was cladogenetic. Besides being evidence for a phylogenetic relationship, the abundant occurrence of intermediate forms at 1.39Ma may constitute a bioevent for a short time interval in the Bering Sea.","PeriodicalId":55107,"journal":{"name":"Geologica Acta","volume":" ","pages":""},"PeriodicalIF":1.5,"publicationDate":"2019-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44033895","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：