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411.
C.A. Kogbe 《Cretaceous Research》1981,2(2):129-186
The Iullemmeden Basin (Mali-Niger-Benin-Nigeria) of tectono-epeirogenic origin was invaded several times by epicontinental transgressions during the Cretaceous and Paleocene.Three major subdivisions are recognized in the Nigerian section of the basin (the “Sokoto Basin”): (1) the lower, continental beds (= Continental Intercalaire) of Late Jurassic to Early Cretaceous age, (2) intermediate marine and brackish water deposits and (3) “Continental T Terminal” of upper Eocene-Miocene age.The geology of the Iullemmeden Basin is reviewed and updated. The relationships between the “Continental Intercalaire” of francophone authors and the Illo and Gundumi Formations are analysed and the type sections of the latter described. It is suggested that the Illo and Gundumi Formations are lateral equivalents.Detailed information on the formations of the Maastrichtian Rima Group is presented. It is concluded that there is no age difference of consequence between the Paleocene Dange, Kalambaina and Gamba Formations.The epicontinental transgressions are interpreted as coming from the north-east, east of the Hoggar massif during the Cenomanian and Turonian and west of the Hoggar during the Maastrichtian and Paleocene. The Sokoto Paleocene molluscan fauna is considered to be terminal Paleocene to Eocene and somewhat younger than the Ewekoro association of coastal Nigeria.A new interpretation of the Continental Terminal is presented. The structural history of the Sokoto Basin is reviewed and partly re-interpreted in the light of new field evidence. 相似文献
412.
AbstractThe shape and structural development of the box-like Parrabel Dome (PD) within the Hastings Block is poorly understood because it has only been weakly cleaved, complexly folded and extensively faulted in comparison to the adjoining blocks. Better characterising this block will provide important controls on the tectonics of the southern New England Orogen. The structural development of the PD and southern Hastings Block (SHB) provides evidence of the degree of rotation, translation and deformation of the Hastings Block, a key terrane within the southern New England Orogen. A major decollement under the Hastings Block–Nambucca Block was suggested to facilitate south-directed deformation caused by the developing Coffs Harbour Orocline. The orientation of bedding and the stratigraphic facing of some fault blocks within the northern Hastings Block (NHB) are consistent with development of the PD, while other fault blocks indicate significant disruption of the NHB prior to, during and after dome development. A deep-seated fault is suggested by the gravity worm analysis consistent with the boundary zone between the PD, NHB-Yarrowitch Block and the east-dipping and younging sequences in the SHB. The eastern limb of the PD underwent clockwise rotation after formation. Fault blocks have been rotated and translated within a restraining bend as the NHB moved post-PD formation northwest along the interface between the NHB and SHB.
- KEY POINTS
The Hastings Block was translated and rotated into its current position from the southeastern end of the Tamworth Belt.
Gravity worm data indicate a boundary between northern and southern Hastings Block.
The Hastings and Nambucca blocks have been detached from the basement Gondwana rocks.
Fault block analysis within the Parrabel Dome, northern Hastings Block indicates relocation of some blocks by faulting.
413.
城市化的发展,使市政道路改造工程越来越多,如何科学有效地利用拟建期的勘察资料,节约勘察成本,成为工程勘察关注的焦点。通过对场地地形地貌和地质构造、地层和水文地质条件、岩土物理力学性质、场地稳定性评价和地震效应、岩土工程重点分析评价等岩土工程要素进行分析,对比前后各要素,探讨勘察资料的时效性,进而确定勘察点布置和深度,以及取土(水)样和原位测试工作量。最后以具体工程为例,探讨勘察要点,指出利用拟建期的勘察资料应主要考虑4.0m以内的地层变化,重点勘察路基破损的路段。 相似文献
414.
为研究一种有效、合理的测定路基动模量的方法,在分析便携式地震波地质分析仪的工作原理和测试特点的基础上,根据弹性动力学和表面波谱分析理论,阐述了便携式地震波地质分析仪的测试原理,并推导了测试路基动模量计算公式。结合路基测试实际工作要求,提出了便携式地震波地质分析仪器的测试步骤及技术要点。通过在路基进行大量点点对应的便携式地震波地质分析仪、便携式落锤弯沉仪和承载板回弹模量测试以及动态圆锥贯入仪贯入测试和灌砂法压实度测试,建立了便携式地震波地质分析仪动模量与其他各指标之间的相关关系。结果表明,便携式地震波地质分析仪与其他检测方法具有很好的相关性,相关系数均大于0.8。结果表明,应用便携式地震波地质分析仪快速检测路基动模量是合理、可行的,可以用于路基施工过程的质量控制,为路面结构设计提供参数和依据。 相似文献
415.
钻孔埋管注盐法整治季节冻土区路基冻害现场试验研究 总被引:1,自引:0,他引:1
以季节冻土区青藏铁路环青海湖段路基冻害为背景,通过选取典型冻害断面,从水分、温度和土性三个方面分析了环湖段路基冻害成因。根据路基病害处理中成熟应用的注浆和注盐法,提出采用钻孔埋管注盐法整治路基病害技术,通过现场冻胀观测,检验注盐法整治路基的有效性。结果表明:环湖段路基冻害主要是由于路基土体内存在一层低液限低渗透性的粉质黏土,黏粒含量高,含水率大,冻深最大为1.5 m,粉质黏土层冻结,引起路基冻胀。结合现场试验段,对用盐量、盐的成分、施工工艺与参数提出合理的施工建议。现场冻胀监测表明,钻孔埋管注盐段路基的冻胀量明显降低,可用于季节冻土区路基冻害的整治治理。 相似文献
416.
417.
为实现震后路基边坡的快速修复,提出基于树根桩加固的震后公路路基边坡综合修复技术。根据路基震害及地质环境对路基边坡的影响分析因素,采用树根桩技术及气泡轻质填土技术修复路基边坡;利用三维有限差分法模拟树桩加固气泡轻质填土修复后路基边坡得到参数值,再结合强度折减法计算得到的路基边坡稳定系数,最后得到优化树根桩的设计参数,以实现震后路基边坡综合修复。以上方法通过仿真模拟实验,得到最优的树根桩排距为2.5 dm。 相似文献
418.