Journal of African Earth Sciences (1983)最新文献_第8页

Trace fossils assemblage and depositional environment of Turonian calcareous sandstones in the southern Benue Trough, Nigeria 尼日利亚贝努埃海槽南部土伦系钙质砂岩微量化石组合与沉积环境

Journal of African Earth Sciences (1983) Pub Date : 1987-01-01 Epub Date: 2010-07-13 DOI: 10.1016/0899-5362(87)90059-5

Etie B. Akpan, Eyo E. Nyong

{"title":"Trace fossils assemblage and depositional environment of Turonian calcareous sandstones in the southern Benue Trough, Nigeria","authors":"Etie B. Akpan, Eyo E. Nyong","doi":"10.1016/0899-5362(87)90059-5","DOIUrl":"10.1016/0899-5362(87)90059-5","url":null,"abstract":"<div><p>A calcareous sandstone sequence that forms part of the Eze-Aku Formation (Reyment) features an assemblage of ichnofossils in a section exposed on a quarry face. The traces encountered include horizontal burrows, some of which are preserved as casts, lined with organic matter and belonging to the ichnogenera <em>Gyrolithes, Pholeus</em> and <em>Arthrophycus</em>. Three other types of trace fossils are described as horizontal crawling trails, flat impressions and cylindrical shafts without formal names. <em>Gyrolithes</em> are by far the dominant traces in this sequence. The degree of bioturbation is high in every horizon. Body fossils are very rare except for scattered occurrence of fragments of calcitic pelecypod shells.</p><p>Ichnological and lithological considerations suggest that the sediments were deposited in an aerated shallow shelf environment which supported an assemblage of decapods, worms and other shallow water marine benthos. Deposition was generally below wave base under a continuous but relatively slow rate of sedimentation.</p></div>","PeriodicalId":100749,"journal":{"name":"Journal of African Earth Sciences (1983)","volume":"6 2","pages":"Pages 175-180"},"PeriodicalIF":0.0,"publicationDate":"1987-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0899-5362(87)90059-5","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"53876974","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}

引用次数: 8

S-type granite from Jabal Al Hasawnah, west central Libya 来自利比亚中西部Jabal Al Hasawnah的s型花岗岩

Journal of African Earth Sciences (1983) Pub Date : 1987-01-01 Epub Date: 2010-07-13 DOI: 10.1016/0899-5362(87)90043-1

K.M. Oun, M.T. Busrewil

引用次数: 2

Chemical composition of some Senonian bivalvian shells and its significance in paleoecological studies, in the area of Abu Roash, Egypt 埃及阿布罗什地区塞涅世双壳类贝壳的化学成分及其古生态学意义

Journal of African Earth Sciences (1983) Pub Date : 1987-01-01 Epub Date: 2010-07-13 DOI: 10.1016/0899-5362(87)90054-6

A.A. Abdel Aal, M.R. Mohammad, A.I. Rezk

引用次数: 3

The development of the Late Cenozoic alkali basaltic Marsabit Shield Volcano, northern Kenya 肯尼亚北部晚新生代碱玄武质马萨比特盾状火山的发育

Journal of African Earth Sciences (1983) Pub Date : 1987-01-01 Epub Date: 2010-07-13 DOI: 10.1016/0899-5362(87)90089-3

R.M. Key , B.P. Rop , C.C. Rundle

{"title":"The development of the Late Cenozoic alkali basaltic Marsabit Shield Volcano, northern Kenya","authors":"R.M. Key , B.P. Rop , C.C. Rundle","doi":"10.1016/0899-5362(87)90089-3","DOIUrl":"10.1016/0899-5362(87)90089-3","url":null,"abstract":"<div><p>The Marsabit Shield Volcano has a surface area of 6300 km<sup>2</sup> and a volume of about 910 km<sup>3</sup> of alkali basaltic lavas and pyroclastics to a maximum (summit) thickness of about 1200 m. Laterally extensive, fissure-sourced lava flow-units predominate with clinopyroxene, plagioclase ± olivine basal basla units followed by olivine basalts. Minor, youngest flows form narrow tongues from cone sources and are also olivine (± analcime) basalts. Cinder cones, block-and-ash cones and <em>maars</em> are concentrated in two belts controlled by fundamental crustal fractures. Hawaiian type volcanism commenced in the very late Pliocene followed by progressively more violent (Strombolian and Ultravulcanian) activity peaking at some stage in the Quaternary. Final vulcanism was relatively gentle and presently the volcano is extinct. The high concentrations of <em>maars</em> is unique to Marsabit in N. Kenya and due to the location of the Sheild over the major aquifer of the Chalbi Basin The volcanism, although contemporaneous with the tectonics of the Gregory Rift, is spatially separated and indicates a regional supply of mantle in N. Kenya. The lavas followed an alkali basalt fractionation trend from a periodotite (xenoliths present in maars) source. Little crust contramination of the source magma occurred, possiblly because of regional crustal tension during the Late Cenozoic in East Africa.</p></div>","PeriodicalId":100749,"journal":{"name":"Journal of African Earth Sciences (1983)","volume":"6 4","pages":"Pages 475-480, IN1-IN5, 481-491"},"PeriodicalIF":0.0,"publicationDate":"1987-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0899-5362(87)90089-3","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"53877464","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}

引用次数: 21

Variable intra-plate igneous activity in central and north-east Sudan 苏丹中部和东北部多变的板块内火成岩活动

Journal of African Earth Sciences (1983) Pub Date : 1987-01-01 Epub Date: 2010-07-13 DOI: 10.1016/0899-5362(87)90088-1

P.M. Klemenic

{"title":"Variable intra-plate igneous activity in central and north-east Sudan","authors":"P.M. Klemenic","doi":"10.1016/0899-5362(87)90088-1","DOIUrl":"10.1016/0899-5362(87)90088-1","url":null,"abstract":"<div><p>Four Phanerozoic alkaline igneous complexes from central and north-eastern Sudan are compared petrologically. Despite many similarities in terms of mineralogy, petrography and major element geochemistry significant differences are found when trace element and particularly isotopic data are considered. In particular the complexes from north-eastern Sudan have markedly lower <sup>87</sup>Sr/<sup>86</sup>Sr ratios and overall RE element content than those occurring in central Sudan. Such differences could be accounted for by variation in the degree of metasomatic alteration associated with non-hydrous volatiles. However, there is no evidence to suggest that the effect of volatiles has been more prominent in any particular geographic location or complex. The chemical character of the north-eastern complexes is similar to the oceanic island leucocratic lavas of St. Helena and Ascension. Further, the complexes of north-eastern Sudan are associated with a prominnent dyke swarm, suggesting a tensional tectonic environment which may have facilitated the passive emplacement of mantle derived magma. In central Sudan there is no direct evidence of rifting and the alkaline rocks are clearly chemically and isotopically similar to anorogenic rocks which are considered to have evolved from mixtures of mantle and crustal derived material. It is suggested that the differences between the alkaline complexes of eastern and central Sudan are due to the charccter of the source material rather than the effect of metasomatic alteration, although mantle source heterogeneity cannot be ruled out.</p></div>","PeriodicalId":100749,"journal":{"name":"Journal of African Earth Sciences (1983)","volume":"6 4","pages":"Pages 465-474"},"PeriodicalIF":0.0,"publicationDate":"1987-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0899-5362(87)90088-1","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"53877447","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}

引用次数: 5

Notes on some shear zones of northern Somalia 关于索马里北部一些剪切带的说明

Journal of African Earth Sciences (1983) Pub Date : 1987-01-01 Epub Date: 2010-07-13 DOI: 10.1016/0899-5362(87)90075-3

Rosalino Sacchi , Adriano Zanferrari

引用次数: 5

Structure et cinématique des peridotites feldspathiques du Cap Bougaroun (Algérie) 阿尔及利亚布加隆角长石橄榄岩的结构和运动学

Journal of African Earth Sciences (1983) Pub Date : 1987-01-01 Epub Date: 2010-07-13 DOI: 10.1016/0899-5362(87)90009-1

M. Misseri

引用次数: 6

Palynology of Albian-Cenomanian strata in Mersa Matruh well, Western Desert, Egypt 埃及西部沙漠Mersa Matruh井Albian-Cenomanian地层孢粉学

Journal of African Earth Sciences (1983) Pub Date : 1987-01-01 Epub Date: 2010-07-13 DOI: 10.1016/0899-5362(87)90005-4

Ismail Z. Sultan

引用次数: 33

Fluvio-deltaic environment and in situ pedogenesis of Middle Miocene kaolinitic sandstones of the Pugu coastal area of Tanzania 坦桑尼亚普谷沿海地区中中新世高岭石砂岩的河流三角洲环境与原位成土作用

Journal of African Earth Sciences (1983) Pub Date : 1987-01-01 Epub Date: 2010-07-13 DOI: 10.1016/0899-5362(87)90064-9

M.K.D. Mutakyahwa

引用次数: 3

Volume contents and author index 卷内容和作者索引

Journal of African Earth Sciences (1983) Pub Date : 1987-01-01 Epub Date: 2010-07-13 DOI: 10.1016/0899-5362(87)90052-2

引用次数: 0