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A preliminary study on sediment flux in the Changjiang Delta during the postglacial period 总被引：12，自引：0，他引：12
During the last 7000 years since the Changjiang Delta was formed, how much sediment brought by the Changjiang River remained in the modern Changjiang Delta? And how much sediment was delivered into the sea and adjacent coasts? These are very important que… 相似文献
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Richard M. Tipping 《第四纪科学杂志》1988,3(2):171-182
Recent publications have presented palynological data from the early postglacial period in the British Isles, which have been interpreted as reflecting sequential glacial retreat following the Loch Lomond Stadial, The methodologies and results of these studies were examined and were concluded to be insufficient to demonstrate glacial retreat. A more cautious methodology was adopted and tested at several pollen sites in the Awe valley, Scotland. The results differed from previous studies in not demonstrating the sequence of palynological changes predicted from the hypothesis. These results need to be replicated at other localities, however, before the deglacial chronology hypothesis can be dismissed. Proposals to test the hypothesis further are suggested. 相似文献
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《Norsk geografisk tidsskrift. Norwegian journal of geography》2012,66(2):79-84
Absolute gravity observations yield insight into geophysical phenomena such as postglacial rebound, change in the Earth's hydrological cycle, sea level change, and changes in the Earth's cryosphere. In the article, the first gravity values at 16 Norwegian stations measured by a modern absolute gravimeter of the FG5 type are presented. The gravity observations were corrected for Earth tides, varying atmospheric pressure, polar motion, and ocean tide loading. The ocean tide loading corrections were subject to special attention. A model based on locally observed ocean tides was applied at some of the stations. The authors estimated the total uncertainties of the gravity values to range from 3 to 4 µgal (1 µgal = 10?8 m s?2). These errors are of magnitude one order less than previously presented absolute gravity values from Norway. The final gravity values are time tagged and will change due to postglacial rebound. The maximum effect is expected to be approximately ?1 µgal yr?1. 相似文献
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Mira Markovaara-Koivisto Antti E.K. Ojala Jussi Mattila Ilmo Kukkonen Ilkka Aro Arto Pullinen Pekka Hänninen Maarit Middleton Aleksi Sutinen Juha Majaniemi Timo Ruskeeniemi Raimo Sutinen 《地球表面变化过程与地形》2020,45(12):3011-3024
The cyclic nature of glaciations and related postglacial faulting represents a risk for the deep geological disposal of spent nuclear fuel in areas likely to be affected by future glaciations. Seismic history was therefore studied by means of detecting geomorphological structures on airborne laser scanning digital elevation models and underground by excavating in an esker and trenching across a postglacial fault located in northern Fennoscandia. OLS dating and assessing the geomorphological structures was used for timing of the seismic history. The results suggest that the faulting of different segments in the Pasmajärvi complex is due to at least two late Weichselian events, which probably occurred both subglacially and postglacially. The most reliable input for the moment magnitude estimates was vertical slip profiles, and therefore these estimates (MW ≈ 6.4–6.9) are suggested. © 2020 John Wiley & Sons, Ltd. 相似文献
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元素地球化学研究表明,长江与黄河对冰后期的苏北滨海平原发育与苏北南黄海潮成砂体的形成影响巨大。冰后期早期长江物质影响大于黄河。黄河供给泥沙量较少,且对本区影响主要在北部、中部地区。公元1128年黄河改道由苏北入海之后,黄河影响范围明显大于长江。长江仅由个别狭窄的汊道提供有限的物质而影响范围较小。古长江主流并未由琼港地区入海,而携带大量物质建设潮成砂体。最近2000年来本区沉积物主要由黄河提供。分析表明元素地球化学方法在沉积物物源判别时,可有效的避免水动力因素影响,取得较好的效果。 相似文献
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Glaciation and deglaciation in Fennoscandia during the last glacial cycles has significantly perturbed the Earth's equilibrium figure. Changes in the Earth's solid and geoidal surfaces due to external and internal mass redistributions are recorded in sequences of ancient coastlines, now either submerged or uplifted, and are still visible in observations of present‐day motions of the surface and glacially induced anomalies in the Earth's gravitational field. These observations become increasingly sophisticated with the availability of GPS measurements and new satellite gravity missions.
Observational evidence of the mass changes is widely used to constrain the radial viscosity structure of the Earth's mantle. However, lateral changes in earth model properties are usually not taken into account, as most global models of glacial isostatic adjustment assume radial symmetry for the earth model. This simplifying assumption contrasts with seismological evidence of significant lateral variations in the Earth's crust and upper mantle throughout the Fennoscandian region.
We compare predictions of glacial isostatic adjustment based on an ice model over the Fennoscandian region for the last glacial cycle for both radially symmetric and fully 3‐D earth models. Our results clearly reveal the importance of lateral variations in lithospheric thickness and asthenospheric viscosity for glacially induced model predictions. Relative sea‐level predictions can differ by up to 10–20 m, uplift rate predictions by 1–3 mm yr−1 and free‐air gravity anomaly predictions by 2–4 mGal when a realistic 3‐D earth structure as proposed by seismic modelling is taken into account. 相似文献
Observational evidence of the mass changes is widely used to constrain the radial viscosity structure of the Earth's mantle. However, lateral changes in earth model properties are usually not taken into account, as most global models of glacial isostatic adjustment assume radial symmetry for the earth model. This simplifying assumption contrasts with seismological evidence of significant lateral variations in the Earth's crust and upper mantle throughout the Fennoscandian region.
We compare predictions of glacial isostatic adjustment based on an ice model over the Fennoscandian region for the last glacial cycle for both radially symmetric and fully 3‐D earth models. Our results clearly reveal the importance of lateral variations in lithospheric thickness and asthenospheric viscosity for glacially induced model predictions. Relative sea‐level predictions can differ by up to 10–20 m, uplift rate predictions by 1–3 mm yr
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Li Congxian 《海洋学报(英文版)》1993,12(4):573-584
-On the basis of the data obtained from the investigations on some rivers in China and Australia, the author discusses the spatial and temporal changes of various portions of fluvial-estuarine system during postglacial sea-level rising in present coastal and deltaic areas. The evolution of a fluvial-estuarine system can be divided into four development stages: early transgression, late transgression, stationary and regression. Early transgression brought about filling-in of the paleo-valley formed in low stand of sea level. In response to late transgression the estuaries were created, during the stationary stage the big swamp was developed. The regression led to estuaries to be filled with sediments and then became deltas. At the same locality the fluvial-estuarine system changed with time. In the transgressive period the lower reach of a river changed into an estuary, and then became nearshore area. In the regressive period the nearshore area changed into an estuary , and then became delta. 相似文献