Lepidostrobus haslingdenensis: A new species from the Lancashire Millstone Grit

A collection of microsporangiate cones is described from the topmost Namurian of Rossendale, Lancashire. The microspores are closely comparable with the dispersed spore species Lycospora noctuina, being of a type that has not been previously recorded from a fructification.     

Sequence stratigraphy of the upper Millstone Grit (Yeadonian,Namurian), North Wales

The upper Millstone Grit strata (Yeadonian, Namurian) of North Wales have been studied using sedimentological facies analysis and sequence stratigraphy. These strata comprise two cyclothems, each containing prodelta shales (Holywell Shale) that pass gradationally upwards into delta‐front and delta‐plain deposits (Gwespyr Sandstone Formation). The deltas formed in shallow water (<100 m), were fluvial‐dominated, had elongate and/or sheet geometries and are assigned to highstand systems tracts. Two delta complexes with distinctive sandstone petrographies are identified: (1) a southerly derived, quartzose delta complex sourced locally from the Wales‐Brabant Massif, and (2) a feldspathic delta complex fed by a regional source(s) to the north and/or west. The feldspathic delta complex extended further south in the younger cyclothem. A multistorey braided‐fluvial complex (Aqueduct Grit, c. 25 m thick) is assigned to a lowstand systems tract, and occupies an incised valley that was eroded into the highstand feldspathic delta complex in the younger cyclothem. A candidate incised valley cut into the highstand feldspathic delta complex in the older cyclothem is also tentatively identified. Transgressive systems tracts are thin (<5 m) and contain condensed fossiliferous shales (marine bands). The high‐resolution sequence stratigraphic framework interpreted for North Wales can be readily traced northwards into the Central Province Basin (‘Pennine Basin’), supporting the notion that high‐frequency, high‐magnitude sea‐level changes were the dominant control on stratigraphic architecture. Copyright © 2007 John Wiley & Sons, Ltd.     

The Millstone Grit (namurian) of the southern pennines viewed in the light of eustatically controlled sequence stratigraphy

The overall lithological succession in the Millstone Grit of the southern Pennines was most probably controlled by glacial-eustatic sea-level oscillations and may be interpreted in terms of the systems tracts of sequence stratigraphy. Bands containing thick-shelled goniatites represent ‘condensed sections’ formed at times of maximum flooding. Turbidite-fronted deltas, marking major basin-filling episodes, resemble ‘lowstand systems tracts’. However all sand influxes did not necessarily occur during lowstands. Millstone Grit sheet deltas and elongate deltas resemble lobate and birdfoot deltas in Recent ‘highstand systems tracts’. The prograding fluviodeltaic complexes at the tops of some major turbidite-fronted deltas were braid deltas. So was the sheet-like channel complex of the Rough Rock at the top of the Millstone Grit, but this was probably part of a ‘highstand systems tract’.     

Evidence for relative sea-level falls during deposition of the Upper Carboniferous Millstone Grit,South Wales

Detailed sedimentological facies analysis of the fluvio-deltaic Millstone Grit succession (Upper Carboniferous) of South Wales reveals that a number of cyclothems bounded by marine flooding surfaces (marine bands) in these strata exhibit facies architectures that represent erosion, non-deposition and/or deposition during periods of falling relative sea-level. A major fluvial complex below the Subcrenatum Marine Band, the Farewell Rock, lies within an incised valley, with a regional unconformity (sequence boundary) at its base. This unconformity is marked by deep erosional relief, an identifiable time gap and an angular discordance in bedding. The Cumbriense Quartzite, a correlative unit containing several mature palaeosols, records a depositional hiatus on a terrace-like interfluve that lay beyond the margins of the coeval Farewell Rock valley. Cyclothems in the underlying Middle Shales contain additional surfaces and units of subtler character. Beneath the Cancellatum Marine Band, a thin (15 cm), calcareous siltstone bed (the ‘Amroth Granule Bed’) that directly overlies prodelta shales contains reworked bioclasts, bored phosphorite clasts and quartz granules. Quartz granules in this bed are interpreted to represent relict lowstand, fluviatile? deposits, which were reworked during later transgression. Three further cyclothems contain sharp-based, storm-reworked mouth bars that record an abrupt lowering of wave base, most probably during periods of falling relative sea-level. One of these cyclothems also contains a distributary channel complex, which records an abrupt influx of coarse-grained sediment of ambiguous origin. The significance of these subtle surfaces and units for intracyclothem stratigraphy has rarely been considered; their prevalence in the Middle Shales provides evidence for numerous, high-frequency relative sea-level falls, which were previously unrecognized. These relative sea-level falls appear to alternate coherently with the widespread sea-level rises recorded by the marine bands, suggesting that glacio-eustasy is their most likely driving mechanism. The notion of glacio-eustatic sea-level falls is supported by the correlation of the basal Farewell Rock sequence boundary with sequence boundaries documented in adjacent basins. The angular unconformity and a change in sediment provenance at the base of the Farewell Rock, however, suggest an additional tectonic control on stratigraphic architecture here, namely a short-lived phase of rifting or inversion prior to widespread fluvial incision. Copyright © 1998 John Wiley & Sons, Ltd.     

地面伽马能谱测量在铀矿找矿中的应用研究--以黑龙江省嘉荫县磨石山地区为例

黑龙江省嘉荫县磨石山地区为火山岩分布区,为研究该地区的铀矿分布特征,采用地面伽马能谱测量方法对该地区进行测量,通过地面伽马能谱在该地区的应用,探讨了磨石山地区的铀异常分布特征,表明该方法在铀矿找矿中应用效果明显,为寻找铀矿提供了途径。     

Laminaset geometries in fine grained shallow marine sequences: core data from the Rannoch Formation (North Sea) and outcrop data from the Kennilworth Member (Utah, USA) and the Bencliff Grit (Dorset, UK)

Sandbodies from storm-dominated marine and marginal marine environments commonly contain intervals of laminated fine sandstones. A characteristic of such lamination is the presence of low angle cross lamination. In order to model correctly the effects of such lamination on a waterflood of an oil-bearing shoreface sequence it was necessary to quantify the geometry of the laminaset elements. This challenge has been greatly complicated by the lack of outcrop of the formation of interest. The Middle Jurassic Rannoch Formation of the North Sea only occurs in the subsurface where it is not possible in core to measure the aspect ratio of laminasets directly. In this study, the laminaset geometry data that can be obtained from core (e.g. apparent set thicknesses) were collected for the Rannoch Formation. These data were compared with similar data from potential outcrop analogues in (1) the Cretaceous Kennilworth Member of the Blackhawk Formation in Utah, USA and (2) the Upper Jurassic Bencliff Grit from the Dorset coast, UK. A quantitative analysis of laminaset geometries has been used to compare subsurface core with potential outcrop analogues. The Rannoch Formation core is characterized by numerous low angle truncations. We have measured these features in two wells (means of 7.2° and 12.1°). Mean apparent set thicknesses were 0.24 and 0.19 m. In the outcrop sections studied, truncation angles ranged from 9.6° to 13.4° and mean set thicknesses from 0.24 to 0.34 m. Mean bounding surface dips of 5.8° and 8.6°, and mean laminaset lengths of 2.3 and 4.1 m were also measured. directly in the field and by using photomosaics. On the basis of this comparison, the Kennilworth Member in Utah was found to be the most suitable and the geometries (i.e. aspect ratios) measured there were used to generate an appropriate geometry of Rannoch laminaset geometries for use in engineering studies: laminaset length, 2.0 m; laminaset thickness, 0.2 m.     

岩石破坏的机理再认识

岩石的各种强度准则一直是解释岩石或岩体破坏机理的主要理论。此外,从流变现象出发,通过数值模拟、实验对照、理论分析、进一步对岩石破坏机理的解释进行了探讨,认为受力岩石或岩体内差异流动变形也是导致岩石破坏的原因。     

西安市街道灰尘中铬、镉、铅赋存状态及环境效应

本文通过对街道灰尘中铬、镉、铅三种元素赋存状态研究、铬、铅在街道灰尘中以残渣态为主，镉以有机质结合态为主。虽然铬、铅、镉存在形式稍有差异，但其在街道灰尘中主要以矿物质的形态存在，说明其比较稳定，不易迁移转化，对环境的危害比较持久。在治理措施上应有早遏止微量元素向环境中排放，以免其与灰尘发生相互作用对环境造成长期的危害。     

长江口南槽季节性冲淤变化及其对河流入海水沙响应关系的初步研究

本文利用长江口南槽1989年12个月的实测地形图和大通站相应的水沙资料,采用GIS技术和数理统计技术分析了南槽的地形变化及其与河流来水来沙的关系.结果表明南槽水深与大通站各月平均流量、输沙率和含沙量之间有明显的相关性,说明河口冲淤对流域水沙变化有敏感响应;河槽的响应具有1～1.5月的滞后性.     

国际工程中设计方的责任

建筑工程中的“设计方”一般是指从事工程设计的专业人士,如建筑师和工程师,但也可能包括除施工或供货以外还承担某些工程设计工作的承包商、分包商及供应商。 “设计”并不限于制作建筑及工程图纸或进行结构方面的运算。设计范围极广,甚至包括了某种材料的选用以及为达到某个目的所应采用的工艺。设计的实质就是选择,选择足以满足工程要求