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1.
Stable oxygen isotope analysis and measurement of several dissolved cations and anions of bulk meltwater samples have provided information about the hydrochemical environment of the glacial hydrological system at Imersuaq Glacier, an outlet tongue from the Greenland ice‐sheet, West Greenland. The samples were collected at frequent intervals during the period 20–28 July 2000 in a small (<20 L s?1) englacial meltwater outlet at the glacier margin. The results document the following findings: (i) a marked diurnal variation of δ18O is related to the composition of oxygen isotope provenances, mainly near‐marginal local superimposed ice and basal up‐sheared ice further up‐glacier; (ii) a relationship is seen between all base cations (Na+, K+, Ca2+, Mg2+), SO42? and δ18O, indicating that solute acquisition is provided by solid–solution contact with the up‐sheared ice—as the relationship with Cl? is weak the influence of seasalt‐derived solutes is small in the area; (iii) when the melt rate is high, two diurnal maxima of δ18O values and solute concentrations are measured, and it is suggested that a snow meltwater component is responsible for the second maximum of δ18O—a short residence time leads to a delayed decrease in ion concentrations. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
2.
渤海新近系浅水三角洲沉积体系与大型油气田勘探 总被引:32,自引:8,他引:24
新近纪渤海具有构造稳定、沉降缓慢、湖泊水域范围大、内部无分割、地形平缓、坡度小等特点,广泛发育浅水三角洲,从而形成渤海海域新近系良好的储盖组合和优越的油气成藏条件。浅水三角洲砂岩储层由于受河流作用的控制,砂体具有明显的方向性,存在明显的分叉现象,与曲流河相比,砂体连通性较好,砂体等厚图呈典型的朵叶状。湖相厚层泥岩普遍发育,与浅水三角洲砂体组成多套垂向优质储盖组合。浅水三角洲发育于渤海新近纪至今处于生烃的峰期主力富烃凹陷的有利区带,新构造运动造成新近纪以来凹陷主力源岩生烃峰期与新构造运动的同步耦合,为渤海大型浅水三角洲成因的优质储层油气成藏创造了优越条件,可以形成大型油气田。因此,重视并充分挖掘渤海浅水三角洲储层类型油气藏的勘探潜力将是追求浅层优质油藏、进一步增储上产的方向所在。 相似文献
3.
深水沉积层序特点及构成要素 总被引:6,自引:0,他引:6
本文在回顾当前国际上深水沉积研究热点的基础上,结合在墨西哥湾深水研究的成果系统描述了深水沉积的定义、形成机理、深水沉积层序及深水沉积构成要素的特点.深水沉积主要是在重力流作用下深水环境的沉积,主要形成于相对水平面下降和早期上升的时期,主要分布在低位体系域中.深水层序以凝缩段为边界,块状搬运沉积最早形成并直接位于层序界面上,其上被河道-天然堤沉积所覆盖.典型深水沉积的要素主要由河道、天然堤及越岸沉积、板状砂、块状搬运沉积等构成,这些沉积要素时空上有序地分布.深水河道是物源的主要通道和沉积的重要场所,从上游至下游河道弯曲度增加,能量逐渐减弱.侧向迁移明显,垂向上由富砂的顺直河道演化为相对富泥的弯曲河道.天然堤及越岸沉积以泥质为主,天然堤沿河道呈楔状分布,其近端砂岩含量高,地层厚且倾角较陡;远端砂岩含量低,地层薄且平缓,侧向连续性好但垂向连续性差.板状砂主要为深水扇前缘非限制性沉积,可分为块型和层型.块型侧向连续性好,同时垂向连通性高.层型侧向连续性好,垂向连通性差.块状搬运沉积主要是低水位期坡上沉积物失稳形成的各类滑塌体及碎屑流,其对下伏地层侵蚀明显,分布广泛,变形构造常见,可作为油气良好的封盖层. 相似文献
4.
We study the reaction of a global ocean–sea ice model to an increase of fresh water input into the northern North Atlantic under different surface boundary conditions, ranging from simple restoring of surface salinity to the use of an energy balance model (EBM) for the atmosphere. The anomalous fresh water flux is distributed around Greenland, reflecting increased melting of the Greenland ice sheet and increasing fresh water export from the Arctic Ocean. Depending on the type of surface boundary condition, the large circulation reacts with a slow-down of overturning and gyre circulations. Restoring of the total or mean surface salinity prevents a large scale redistribution of the salinity field that is apparent under mixed boundary conditions and with the EBM. The control run under mixed boundary conditions exhibits large and unrealistic oscillations of the meridional overturning. Although the reaction to the fresh water flux anomaly is similar to the response with the EBM, mixed boundary conditions must thus be considered unreliable. With the EBM, the waters in the deep western boundary current initially become saltier and a new fresh water mass forms in the north-eastern North Atlantic in response to the fresh water flux anomaly around Greenland. After an accumulation period of several decades duration, this new North East Atlantic Intermediate Water spreads towards the western boundary and opens a new southward pathway at intermediate depths along the western boundary for the fresh waters of high northern latitudes. 相似文献
5.
Ice Sheet-Thermohaline Circulation Interactions in a Climate Model of Intermediate Complexity 总被引:3,自引:0,他引:3
A vertically integrated dynamic ice sheet model is coupled to the atmosphere-ocean-sea ice-land surface climate model recently
developed by Wang and Mysak (2000). The background lateral (east-west) ice sheet discharge rate used by Gallee et al. (1992) is reduced and the planetary emissivity is increased (to parameterize the cooling effect of a decrease of the atmospheric
CO2 concentration), in order to build up substantial ice sheets during a glacial period and hence set the stage for ice sheet-thermohaline
circulation (THC) interactions. The following iceberg calving scheme is then introduced: when the maximum model height of
the North American ice sheet reaches a critical value (2400 m), a prescribed lateral discharged rate is imposed on top of
the background discharge rate for a finite time. Per a small prescribed discharge rate, repeated small iceberg calving events
occur, which lead to millennial-scale climate cycles with small amplitudes. These are a crude representation of Dansgaard-Oeschger
oscillations. Over one such cycle, the zonally averaged January surface air temperature (SAT) drops about 1.5°C at 72.5°N.
However, a large prescribed lateral discharge rate leads to the shut down of the THC. In this case, the January SAT drops
about 5°C at 72.5°N, the sea ice extent advances equatorward from 57.5° to 47.5°N and the net ice accumulation rate at the
grid of maximum ice sheet height is reduced from 0.24 to 0.15 m/y. Since data strongly suggest that a collapsed THC was not
a steady state during the last glacial, we restore the THC by increasing the vertical diffusivity in the North Atlantic Ocean
for a finite time. The resulting climate cycles associated with conveyor-on and conveyor-off phases have much larger amplitudes;
furthermore, the strong iceberg calving events lead to a larger loss of ice sheet mass and hence the period of the oscillations
is longer (several thousand years).
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
6.
7.
Mauro Cacace Ulf Bayer Anna Maria Marotta 《International Journal of Earth Sciences》2008,97(5):899-913
The large-scale crustal deformations observed in the Central European Basin System (CEBS) are the result of the interplay
between several controlling factors, among which lateral rheological heterogeneities play a key role. We present a finite-element
integral thin sheet model of stress and strain distribution within the CEBS. Unlike many previous models, this study is based
on thermo-mechanical data to quantify the impact of lateral contrasts on the tectonic deformation. Elasto-plastic material
behaviour is used for both the mantle and the crust, and the effects of the sedimentary fill are also investigated. The consistency
of model results is ensured through comparisons with observed data. The results resemble the present-day dynamics and kinematics
when: (1) a weak granite-like lower crust below the Elbe Fault System is modelled in contrast to a stronger lower crust in
the area extending north of the Elbe Line throughout the Baltic region; and (2) a transition domain in the upper mantle is
considered between the shallow mantle of the Variscan domain and the deep mantle beneath the East European Craton (EEC), extending
from the Elbe Line in the south till the Tornquist Zone. The strain localizations observed along these structural contrasts
strongly enhance the dominant role played by large structural domains in stiffening the propagation of tectonic deformation
and in controlling the basin formation and the evolution in the CEBS. 相似文献
8.
东南极Lambert冰川-Amery冰架系统平衡通量分布的计算 总被引:2,自引:1,他引:2
通过对Lambert冰川盆地(LGB)考察路线上约1 700 km长的LGB剖面和距冰架末端约50 km、长150 km的A剖面, 分别利用GPS冰流速值及雷达测厚值进行冰通量的计算得出:每年流过LGB剖面的冰通量为43.95 Gta-1, 而通过A剖面的冰通量仅为26. 42 Gt*a-1, Amery冰架底部净融化量为7.8 Gt*a-1. 整个Lambert冰川-Amery冰架系统(LAS)地区的表面净物质平衡总量约为90 Gt*a-1; LGB地区的表面净物质平衡总量为46 Gt*a-1. 通过分析得出, 整个LAS地区及LGB地区均处于物质正平衡状态, 而LAS流域的上游区域S'则处于物质负平衡状态. 相似文献
9.
10.