Dinantian sedimentation and the basement structure of the Derbyshire Dome

The depositional history of the Dinantian on the Derbyshire Dome can be divided into three phases: (1) pre-Holkerian: onlap of an irregular basement surface by evaporite and carbonate sediments, (2) Holkerian to Asbian: sedimentation on a carbonate shelf formed by the merging of early Dinantian depocentres following burial of the basement topography, and (3) Brigantian: formation of intrashelf basins and the development of a carbonate ramp on part of the pre-existing shelf. A model of the basement structure underlying the Derbyshire Dome is presented to explain the location of the Brigantian intrashelf basins and carbonate ramp. The basement consists of two main tilted fault blocks separated by a smaller tilt block. Movement on faults bounding the tilt blocks caused the development of intrashelf basins. The basin margins were controlled by structures which developed in the cover sediments. The carbonate ramp present during the late Brigantian developed in response to an eastward tilting of the basement.     

三维椭球形盆地对球面波的散射

针对三维沉积盆地对球面波的散射问题,发展一种快速宽频间接边界元方法(IBEM).利用ANSYS建立求解模型,基于Intel-Fortran编译器编译相应的计算程序,对基岩半空间三维半椭球形盆地对球面波的散射进行了数值分析,着重探讨入射波频率、波源埋深、波源与不规则地形(沉积盆地)距离等参数对地震动特性的影响规律,计算方...     

Local and regional constraints on relative sea-level changes in southern Isle of Skye,Scotland, since the Last Glacial Maximum

New relative sea-level (RSL) data constrain the timing and magnitude of RSL changes in the southern Isle of Skye following the Last Glacial Maximum (LGM). We identify a marine limit at ~23 m OD, indicating RSL ~20 m above present c. 15.1 ka. Isolation basin data, supported by terrestrial and marine limiting dates, record an RSL fall to 11.59 m above present by c. 14.2 ka. This RSL fall occurs across the time of global Meltwater Pulse 1A, supporting recent research on the sources of ice melting. Our new data also help to resolve some of the chronological issues within the existing Isle of Skye RSL record and provide details of the sub-Arctic marine environment associated with the transition into Devensian Lateglacial climate at c. 14.5 k cal a bp , and the timing of changes in response to the Loch Lomond Stadial climate. Glacio-isostatic adjustment (GIA) model predictions of RSL deviate from the RSL constraints and reflect uncertainties in local and global ice models used within the GIA models. An empirical RSL curve provides a target for future research.     

The Cwm Llwyd Outlier,Carmarthenshire, South‐West Wales – Britain's deepest karstic subsidence or Variscan pull‐apart structure?

The Cwm Llwyd Outlier of Namurian Middle Shales in the central part of the Black Mountain escarpment of South Wales is an unusual structure. It occupies a topographic depression located more than 2 km from the main outcrop of the Middle Shales and has a stratigraphic discordance with its wall‐rocks of more than 300 m. Previous interpretations advocating a karstic origin imply that this is the deepest known subsidence in Great Britain. However, although the outlier lies among some of the finest epikarst landforms in the country, several factors indicate that the subsidence was not caused by a karstic mechanism. These include the amount of stratigraphic displacement in contrast to the depth of available vertical space in the putative host Carboniferous Limestone, the relatively simple form of the outlier, and the absence of brecciation, marginal solution residues and associated palaeoendokarst features in the adjacent wall‐rocks. The outlier is re‐interpreted here as the product of faulting which occurred during a Variscan strike‐slip or transpressive tectonic regime, producing local sinistral transtension that may have been re‐activated in the Palaeogene period. Remapping the outlier at a scale of 1:2 500 indicates that the present structure is related principally to a left‐stepping offset between the Cwm Llwyd and Llwyn Celyn faults. Analogies are drawn with the Cainozoic pull‐apart structures in Southwest England. Near‐surface reddening and kaolinization of the beds probably represent pre‐Pleistocene weathering. Copyright © 2006 John Wiley & Sons, Ltd.