Aqueous and petroleum fluid flow associated with sand injectites   总被引：1，自引：0，他引：1  

Rene Jonk  John Parnell  Andrew Hurst 《Basin Research》2005,17(2):241-257

Field, petrographic and fluid inclusion characteristics of sand injectites from five outcrop localities and from the subsurface of the Tertiary of the south Viking Graben are described. Although the case studies are from a wide variety of sedimentological, stratigraphic and tectonic settings, and hence their diagenetic evolutions differ significantly, it is possible and useful to assign diagenetic events to three distinct phases of fluid flow associated with sand injectites in sedimentary basins. Firstly, there is fluid flow associated with the injection of the fluid–sediment mix during shallow burial. Early diagenetic imprints in sand injectites reveal that basinal fluids, which may be released during movement along deeper‐seated faults, can be associated with this process and thus the injection process may reveal information on the timing of basin‐scale movement of fluids. Secondly, following the injection process, basinal fluids continue to migrate through uncemented injectites and mix with the ambient meteoric and/or marine pore fluids that invade injectites from the overlying and surrounding host sediments. Early, often pervasive, carbonate cementation is common within sand injectites and rapidly turns sand injectites into flow barriers during shallow (<1 km) burial. If early carbonate cementation is not pervasive, fluid inclusions in late quartz cement (～>2 km of burial) reveal additional information on fluid flow associated with sand injectites during deeper burial. The latest phase of fluid flow occurs when sand injectites are reactivated as preferential fluid conduits during phases of deformation, when well‐cemented subvertical sand injectites become sites of focussed brittle deformation (fracturing). This study shows that sand injectites are a common and volumetrically important type of structural heterogeneity in sedimentary basins and that long‐lived fluid flow associated with sand injectites in very different settings can be assessed and compared systematically using a combination of petrography and fluid inclusion studies.  相似文献   

Fluidization and injection in the deep-water sandstones of the Eocene Alba Formation (UK North Sea)   总被引：4，自引：0，他引：4  

Davide Duranti  Andrew Hurst 《Sedimentology》2004,51(3):503-529

The Nauchlan Member of the Late Eocene Alba Formation (UK North Sea) consists of a deep‐water channel fill that was extensively modified by post‐depositional sand remobilization and injection. Sandstone textures, facies associations and the geometry of the channel fill were affected. A suite of sand‐rich facies was produced by large‐scale fluidization and injection within the channel fill and above it. These facies, termed here unstratified facies, are characterized by the absence of stratification surfaces and by discordant relationships with bedding in the adjacent succession. They reflect variable degrees of disruption of the primary sedimentary structures caused by escaping pore fluid, the velocity of which is estimated at least in the order of 0·1 ms^?1. Adjacent mudstones were severely disrupted by hydraulic fracturing, and fragments of fractured mudstone were incorporated into the fluidized sand. Average porosity was decreased in the sandstones affected by fluidization. Two main phases of sand injection are inferred to occur at different burial depths. A shallow burial phase (below 100 m) produced thin dykes with ptygmatic folds. The second phase occurred at the boundary between Eocene and Oligocene (≈ 300 m burial depth) and resulted in large‐scale tabular wing‐like dykes that project from the edges of the channel fill. The significant pore‐fluid overpressure, which was required to hydraulically fracture the thick mudstone seal and to fluidize the large volume of sand, was likely to be built up by static liquefaction of the source sand and was possibly enhanced by hydrocarbon gas influx.  相似文献   

Precipitation in the Venezuelan Andes in the context of regional climate     

Dr. R. S. Pulwarty  R. G. Barry  C. M. Hurst  K. Sellinger  L. F. Mogollon 《Meteorology and Atmospheric Physics》1998,67(1-4):217-237

Summary Rainfall regimes are primarily unimodal in central and eastern Venezuela but bimodal (peaks in May–June and September-October-November with a minimum in July–August) in the northwest. There is a sharp transition across the Andes suggesting a topographic-circulation connection. However, a mid-summer minimum also occurs at other locations in Venezuela and Central America during individual years. This paper addresses the nature and control of the regimes including the role of large-scale circulation features and convection as indicated by outgoing longwave radiation data. Altitudinal characteristics of precipitation in the Andes and their spatial variability are also investigated. The development of the minimum within the rainy season annual cycle is shown to be related to the combined effects of the evolution of sea surface temperatures in the east Pacific warm pool and reinforced in the area of the Andes by enhanced easterlies during July and August.Abbreviations used in text ENSO El Nino-Southern Oscillation - EPWP East Pacific Warm Pool - ITCZ Inter-tropical Convergence Zone - MEI Multivariate ENSO Index - MSM Mid-Summer Minimum - NCEP National Centers for Environmental Prediction - OLR Outgoing Longwave Radiation - SOI Southern Oscillation Index - SST Sea Surface Temperature With 13 Figures  相似文献   

GPS-assisted GLONASS orbit determination   总被引：1，自引：0，他引：1  

D. Kuang  Y. E. Bar-Sever  W. I. Bertiger  K. J. Hurst  J. F. Zumberge 《Journal of Geodesy》2001,75(11):569-574

 Using 1 week of data from a network of GPS/GLONASS dual-tracking receivers, 15-cm accurate GLONASS orbit determination is demonstrated with an approach that combines GPS and GLONASS data. GPS data are used to define the reference frame, synchronize receiver clocks and determine troposphere delay for the GLONASS tracking network. GLONASS tracking data are then processed separately, with the GPS-defined parameters held fixed, to determine the GLONASS orbit. The quality of the GLONASS orbit determination is currently limited by the size and distribution of the tracking network, and by the unavailability of a sufficiently refined solar pressure model. Temporal variations in the differential clock bias of the dual-tracking receivers are found to have secondary impact on the orbit determination accuracy. Received: 5 January 2000 / Accepted: 15 February 2001  相似文献   

Sr evolution in the West Greenland-Labrador craton: a model for early Rb depletion in the mantle     

Richard W Hurst 《Geochimica et cosmochimica acta》1978,42(1):39-44

A model for Sr evolution in the West Greenland-Labrador region is proposed based on the available data for granitic gneisses ranging in age from 3.6 AE to 1.9 AE and for recent continental tholeiites from West Greenland. The evolution of initial Sr isotopic composition is consistent with a two-stage model for the mantle in this area with a constant Rb/Sr ratio of 0.014 ± 0.002 from ～ 4.45 AE through the present. The model suggests the mantle may have been depleted in Rb ～ 4.45 AE ago if the Earth was originally chondritic with respect to Rb and Sr. This age of differentiation is consistent with recently proposed terrestrial differentiation based on Pb Pb analyses of ancient Amîtsoq gneiss feldspars (～4.47 AE, Gancarz and Wasserburg, 1977). A linear regression of the gneisses, if extrapolated to the present, predicts the present value of Sr⁸⁷/Sr⁸⁶ of the mantle in this area to be 0.7034 ± 0.0003 which is the measured Sr isotopic composition of the recent Svartenhuk tholeiites. Various implications of the model with respect to early Earth history, mantle evolution and pre-emplacement histories of gneissic suites are discussed.  相似文献   

How long is a hillslope?   总被引：1，自引：0，他引：1       下载免费PDF全文

Stuart W.D. Grieve  Simon M. Mudd  Martin D. Hurst 《地球表面变化过程与地形》2016,41(8):1039-1054

Hillslope length is a fundamental attribute of landscapes, intrinsically linked to drainage density, landslide hazard, biogeochemical cycling and hillslope sediment transport. Existing methods to estimate catchment average hillslope lengths include inversion of drainage density or identification of a break in slope–area scaling, where the hillslope domain transitions into the fluvial domain. Here we implement a technique which models flow from point sources on hilltops across pixels in a digital elevation model (DEM), based on flow directions calculated using pixel aspect, until reaching the channel network, defined using recently developed channel extraction algorithms. Through comparisons between these measurement techniques, we show that estimating hillslope length from plots of topographic slope versus drainage area, or by inverting measures of drainage density, systematically underestimates hillslope length. In addition, hillslope lengths estimated by slope–area scaling breaks show large variations between catchments of similar morphology and area. We then use hillslope length–relief structure of landscapes to explore nature of sediment flux operating on a landscape. Distinct topographic forms are predicted for end‐member sediment flux laws which constrain sediment transport on hillslopes as being linearly or nonlinearly dependent on hillslope gradient. Because our method extracts hillslope profiles originating from every ridgetop pixel in a DEM, we show that the resulting population of hillslope length–relief measurements can be used to differentiate between linear and nonlinear sediment transport laws in soil mantled landscapes. We find that across a broad range of sites across the continental United States, topography is consistent with a sediment flux law in which transport is nonlinearly proportional to topographic gradient. © 2016 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.  相似文献   

Harold Edwin Hurst: the Nile and Egypt,past and future     

John Sutcliffe  Stephen Hurst  Ayman G. Awadallah  Emma Brown  Khaled Hamed 《水文科学杂志》2016,61(9):1557-1570

ABSTRACT

H.E. Hurst spent some 60 years studying the Nile for the Egyptian government, and laid the foundation for a monumental set of hydrological records and investigations. His studies of the size of over-year reservoirs needed to maintain a given yield from Nile flows showed that this was greater than that based on random series. This finding, known as the Hurst phenomenon, was confirmed by other natural series and led to important advances in practical and theoretical statistics. His work led to the design of the Aswan High Dam and to continued research in Egypt.