渤海湾西北岸牡蛎礁体对区域性构造活动与水动型海面变化的响应   总被引：9，自引：2，他引：7       下载免费PDF全文

范昌福  王宏  李建芬  裴艳东  王福  商志文 《第四纪研究》2005,25(2):235-244

渤海湾地区广泛分布的古海面标志物,为建立该地区的相对海面变化曲线提供了良好的基础。过去20年来该地区已相继建立了一些相对海面变化曲线,但在讨论影响古海面标志物高程的因素时,未将构造活动与水动型海面变化及均衡作用对高程的贡献量加以区分。文章以该地区7个点的古海面标志物及相关层位的高程测量与年代学测定结果,经与地区性预测海面变化曲线进行对比后,定量讨论了该地区海面变化(包括绝对海面变化与冰川、水均衡作用)与构造活动对古海面标志物高程的贡献;并以壳体的稳定同位素、地层记录与古地震研究资料讨论了牡蛎礁体在建礁过程中所记录的构造下沉。  相似文献   

海岸带整治修复评价标准探索   总被引：2，自引：0，他引：2       下载免费PDF全文

王琪  韩宇  陈培雄 《海洋开发与管理》2017,34(3):12-19

海岸带整治修复工作的开展有利于贯彻落实科学发展观,促进海洋生态文明建设;有利于落实海洋功能区划制度,强化海洋综合管理;有利于促进海洋生态环境保护,保障海洋生态安全;有利于优化海岸资源配置,规范海域开发秩序;有利于改善海岸景观质量,提升海域资源价值;有利于履行各级海洋行政主管部门的职责,提升海洋综合管理水平。但在我国现有的标准体系中,在国家层面尚没有与海岸带整治修复相关的标准,海岸带整治修复缺乏系统的过程控制、质量管理、结果评价标准。文章基于浙江省海岸带开发利用现状和面临的问题,为了更好地推进海岸带整治修复工作顺利开展和实施,研究探索海岸带整治修复评价标准。  相似文献   

Long-Term and Short-Term Variations of Sea Level in Eastern Canada: A Review     

Karim Hilmi  Tad Murty  Mohammed I. El Sabh  Jean-Pierre Chanut 《Marine Geodesy》2013,36(1-2):61-78

This is a review of sea level data performed at three selected stations (Québec-Lauzon, Harrington Harbour,and Halifax) in eastern Canada in order to investigate the seasonal trends and other long-term and short-term changes which occurred since the beginning of the 20th century. Stations situated in riverine or estuarine regions (e.g., Québec-Lauzon) are significantly affected by freshwater flow in their annual cycle of sea level changes and exhibit a definite maximum in spring and minimum in autumn-winter. Other stations situated in the eastern half of the Gulf of St. Lawrence (e.g., Harrington Harbour) or near the open Atlantic coast (Halifax) mainly follow the general cycle of subarctic regions, with lows in spring-summer and highs in autumn-winter. Such seasonal variations appear to be related to the atmospheric pressure and baroclinic current variations. Secular trends in mean sea level in eastern Canadian waterbodies show a mean rise of about 2.56 mm/yr -1 due to tectonic motions, that is, land subsidence. At several stations in eastern Canada, evidence is found for the influence of the nodal tide (18.6 years), the sunspot cycle (10.8 years), the lunar perigee (8.47 years), the pole tide (14.5 months), the annual cycle (12 months), and semiannual tidal cycle (6 months) in sea level records. Beside long-term oscillations with periods of more than one year, evidence is found for high energetic semidiurnal and diurnal tides where they contribute largely (from 90-95%) to short term variability of sea level. In the residual signal (variations of sea level--tidal variations), short-term variations between 2 to 30 days can be attributed to meterological forcing (atmospheric pressure and winds), longitudinal seiches (2-10 h), atmospheric tides (12 h and 24 h) and inertial oscillations (16-18 h). A regressive model showed that the water discharge from the St. Lawrence River contributes 29% to the monthly residual sea level at Québec-Lauzon. The atmospheric pressure and winds contribute respectively 8.1% and 8.9% at this station. They contribute 52.1% and 7.7% at Harrington Harbour and 41.8% and 14.3% at Halifax. The regression coefficients of residual sea level on atmospheric pressure are respectively estimated to be -1.507 cm. ( hPa ) -1 ( - 0.345 cm. ( hPa ) -1 ), -0.776 cm. ( hPa ) -1 ( - 0.112 cm. ( hPa ) -1 ) and -0.825 cm. ( hPa ) -1 ( - 0.008 cm. ( hPa ) -1 ) at the three stations. Compared to the coefficient of the inverted barometer, estimated to be -1 cm. ( hPa ) -1 , these effects of the atmospheric pressure on sea level variations seem to be amplified at Que´bec-Lauzon by the wind effects (and water discharge) while they are reduced at Harrington Harbour and Halifax.  相似文献   

Remote Sensing of Mangrove Change Along the Tanzania Coast   总被引：1，自引：1，他引：0  

Yeqiao Wang  Gregory Bonynge  Jarunee Nugranad  Michael Traber  Amani Ngusaru  James Tobey 《Marine Geodesy》2013,36(1-2):35-48

This article contributes to the understanding of the changes in distribution and total area of mangrove forests along the mainland Tanzania coast over the past decade. Mangroves are recognized as critical coastal habitat requiring protection and special attention. The Tanzania coastline forms a suitable habitat for establishment of mangrove forests. Mangrove forests are distributed from Tanga in the north to Mtwara in the south covering approximately 109,593 hectares from 1988-1990 and about 108,138 hectares in 2000. The largest continuous mangrove stands are found in the districts of Rufiji, Kilwa, Tanga-Muheza, and Mtwara. Comparison of data between these two time periods shows that the geographic coverage of mangroves has no dramatic change in the past decade. The Tanzania Mangrove Management Project and other closely related programs and efforts pertaining to mangrove conservation contribute to direct restoration and natural regeneration of mangroves. This study documents the changes of mangroves and demonstrates that remote sensing and GIS offer important data and tools in the advancement of coastal resource management and ecosystem monitoring. Application of geographic information technologies is critical for improved coastal resources management and decision making for sustainable development in Tanzania.  相似文献   

The Jurassic Coast: Geoscience and education – An overview     

Jonathan Larwood 《Proceedings of the Geologists' Association. Geologists' Association》2019,130(3-4):265-273

  相似文献   

Tidal modeling of the Hudson-Raritan estuary     

L.Y. Oey  G.L. Mellor  R.I. Hires 《Estuarine, Coastal and Shelf Science》1985,20(5):511-527

Tidal flow characteristics in the Hudson-Raritan Estuary are studied with a two-dimensional, depth-averaged finite difference model. Rivers are modeled as one-dimensional channels with variable width and depth and are calculated as part of the two-dimensional calculations at no extra computational cost. An extensive comparison of numerical, tidal calculations with observational data than has previously appeared in the literature is presented. Computed velocity and tidal elevation fields compare well with observations. Comparison with observations at the Sandy Hook-Rockaway Point transect indicates that the barotropic tidal residual current contributes significantly to the overall steady circulation in the harbor. The residual current is mainly induced by the coastal geometry and bottom topography through the nonlinear inertia effects.  相似文献   

Development of inverted metamorphic isograds in the western metamorphic belt, Juneau, Alaska   总被引：3，自引：0，他引：3  

G. R. HIMMELBERG  D. A. BREW  A. B. FORD 《Journal of Metamorphic Geology》1991,9(2):165-180

An inverted metamorphic gradient is preserved in the western metamorphic belt near Juneau, Alaska. The western metamorphic belt is part of the Coast plutonic–metamorphic complex of western Canada and southeastern Alaska that developed as a result of tectonic overlap and/or compressional thickening of crustal rocks during collision of the Alexander and Stikine terranes. Detailed mapping of pelitic single-mineral isograds, systematic changes in mineral assemblages, and silicate geothermometry indicate that thermal peak metamorphic conditions increase structurally upward over a distance of about 8 km. Peak temperatures of metamorphism increase progressively from about 530 °C for the garnet zone to about 705 °C for the upper kyanite–biotite zone. Silicate geobarometry suggests that the thermal peak metamorphism occurred under pressures of 9–11 kbar. The metamorphic isograds are in general parallel to the tonalite sill that is regionally continuous along the east side of the western metamorphic belt, although truncation of the isograds north of Juneau indicates that the sill intrusion continued after the isograds were established. Our preferred interpretation of the cause of the inverted gradient is that it formed during compression of a thickened wedge of relatively wet and cool rocks in response to heat flow associated with the formation and emplacement of the tonalite sill magma. Garnet rim compositions and widespread growth of chlorite suggest partial re-equilibration of the schists under pressures of 5–6 kbar during uplift in response to final emplacement and crystallization of the tonalite sill. The combined results of this study with previous studies elsewhere in the western metamorphic belt indicate that high-T/high-P metamorphism associated with the collision of the Alexander and Stikine terranes was a long-lived event, extending from about 98 Ma to about 67 Ma.  相似文献   

Residue levels of HCHs,DDTs and PCBs in shellfish from coastal areas of east Xiamen Island and Minjiang Estuary,China   总被引：8，自引：0，他引：8  

Chen W  Zhang L  Xu L  Wang X  Hong L  Hong H 《Marine pollution bulletin》2002,45(1-12):385-390

Shellfish samples were collected from the coastal cultivating areas of east Xiamen Island and Minjing Estuary, China and analyzed for hexachlorocyclohexanes (HCHs), DDTs and polychlorinated biphenyls (PCBs) by GC. Concentration ranges of HCHs, DDTs and PCBs in the coastal area of east Xiamen Island were 0.18–345, 75.2–2143 and ND-23 ng g⁻¹ dry wt., respectively; those for Minjiang Estuary were ND-5.07, 21.5–2396 and ND-6.78 ng g⁻¹ dry wt., respectively. The results showed that the organochlorines were evidently accumulated in marine bivalve molluscs, particularly in oyster. The concentrations of organocholorine pollutants in shellfish samples varied with the sampling locations, the season of collection and organism species, but were generally higher than those in the sediments. The concentrations of DDTs in the shellfish were high as compared with HCHs and PCBs, so that DDTs can be considered as the typical organochlorines in the survey areas. The residue levels and compositions of HCHs, DDTs and PCBs are discussed.  相似文献   

Ekman transport patterns in the area close to the Galician coast (NW, Spain)     

J. M. Cabanas  I. Alvarez 《Journal of Atmospheric & Ocean Science》2005,10(4):325-341

A 40 year time series of daily and monthly Ekman transport is analysed in an oceanic area 150 km offshore Cape Finisterre (43°N, 11°W). The periodicity of the signal showed an annual component (365 days), a seasonal fluctuation (50 days) and a time scale related to passing storms (20 days). The Ekman transport showed different seasonal patterns. Thus, the summer pattern is characterized by transport pointing seaward (upwelling favourable) practically perpendicular to the shoreline, while the winter pattern is characterized by transport pointing landward (downwelling favourable). Although the most favourable upwelling conditions were observed during summer, for the last 15 years the frequency of observed winter upwelling events is higher due to the prevalence of northerly winds.  相似文献   

Contourite origin for shelf and upper slope sand sheet, offshore Antarctica   总被引：1，自引：0，他引：1  

Antonio B. Rodriguez  John B. Anderson† 《Sedimentology》2004,51(4):699-711

A widespread (3200 km²), thick (10 cm to > 100 cm) sand deposit exists on the continental shelf and upper slope offshore of the Pennell Coast, Antarctica. The sand body occurs at water depths between 200 and 1200 m. The mean grain size of the sand varies from 3·3 phi to 1·2 phi, and the composition is dominantly volcanic. The only source for this volcanic material is Cape Adare, a volcanic headland. Sands are transported up to 70 km from Cape Adare by a westward‐flowing circumpolar boundary current that impinges on the upper slope and shelf. Radiocarbon dates from the sand and from the glacial unit beneath it indicate that the deposit formed within the past 9000 years. The occurrence of this sand sheet demonstrates the ability of contour currents to assemble extensive sand bodies on the shelf and upper slope and the relatively rapid rate at which these deposits may form.  相似文献