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傅再扬  危福泉  吴绍祖  龙政强 《大地测量与地球动力学》2007,27(1):34-39

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From non‐tidal shelf to tide‐dominated strait: The Miocene Bonifacio Basin,Southern Corsica     

MICHELLE FERRANDINI  JEAN FERRANDINI  MIGUEL SANTIAGO  ISABELLE THINON  JEAN‐PIERRE ANDRÉ  YVES BARTHET  POL GUENNOC  BERNADETTE TESSIER 《Sedimentology》2013,60(2):599-623

This study documents a change from a non‐tidal to tide‐dominated shelf system that occurred between Corsica and Sardinia (the Bonifacio Basin, Western Mediterranean) during the early to middle Miocene. The non‐tidal deposits formed on a low‐energy siliciclastic shelf surrounded by progradational coralline algal ramps at full highstand. The tidal deposits consist of an up to 200 m thick succession of siliciclastic to coralline‐rich cross‐beds formed by large sub‐tidal dunes. Based on outcrop and sub‐surface data, it is possible to conclude that the tidal currents were amplified as a consequence of the rapid subsidence of the basin centre due to tectonic activity. It is suggested that this tectonic event initiated the strait between Corsica and Sardinia. The strait was deep enough to allow the tidal flux to be significantly increased, generating a localized strong tidal current at the junction between the Western Mediterranean and the East Corsica Basin.  相似文献   

Controls on microbial activity and tidal flat evolution in Shark Bay,Western Australia     

Ricardo J. Jahnert  Lindsay B. Collins 《Sedimentology》2013,60(4):1071-1099

Microbial deposits at Shark Bay constitute a diverse living microbial carbonate system, developed in a semi‐arid, highly evaporative marine setting. Three tidal flats located in different embayments within the World Heritage area were investigated in order to compare microbial deposits and their Holocene evolution. The stressing conditions in the intertidal–subtidal environment have produced a microbial ecosystem that is trapping, binding and biologically inducing CaCO₃ precipitation, producing laminated stromatolites (tufted, smooth and colloform), non‐laminated thrombolitic forms (pustular) and cryptomicrobial non‐laminated forms (microbial pavement). A general shallowing‐upwards sedimentary cycle was recognized and correlated with Holocene sea‐level variations, where microbial deposits constitute the younger (2360 years bp ) and shallower sedimentary veneer. In addition, sediments have been documented with evidence of exposure during the Holocene, from 1040 to 940 ¹⁴C years bp , when sea‐level was apparently lower than present. Filamentous bacteria constitute the dominant group in the blister, tufted and smooth mat types, and coccus bacteria dominate the pustular, colloform and microbial pavement deposit types. In the subtidal environment within colloform and pavement structures, microbial communities coexist with organisms such as bivalves, serpulids, diatoms, green algae (Acetabularia), crustaceans, foraminifera and micro‐gastropods, which are responsible for exoskeleton supply and extensive bioturbation. The internal fabric of the microbial deposits is laminated, sub‐laminar, scalloped, irregular or clotted, depending on the amount of fine‐grained carbonate and the natural ability of microbial communities to trap and bind particles or induce carbonate precipitation. Nilemah tidal flat contains the thickest (1·3 m) and best‐developed microbial sedimentary system; its deposition pre‐dated the Rocky Point and Garden Point tidal flats, with the most positive isotope values for δ¹³C and δ¹⁸O, reflecting strong microbial activity in a highly evaporative environment. There is an evolutionary series preserved within the tidal flats reflecting relative ages and degree of salinity elevation.  相似文献   

Description of littoral,alongshore sediment movement from empirical eigen‐function analysis     

D. J. Clarke  I. G. Eliot 《Australian Journal of Earth Sciences》2013,60(3-4):327-341

Measurements of 18 closely spaced beach profiles spanning Warilla Beach, N.S.W., over a 5‐year period have been examined for alongshore exchanges in beachface configuration. Horizontal slices of beach corresponding with berm, upper swash, upper and lower intertidal zones were examined by empirical orthogonal function (EOF) analysis. The first four EOF's for each of the four slices contain over 90% of the total variance for each slice. In each instance the first eigen‐function mode represents the onshore‐offshore component of beach response, and accounts for 50 to 60% of the variance. Subsequent modes describe alongshore exchange of sediment associated with large, standing, cellular water circulations of the embayment. Sediment shunts along each horizontal slice are determined by identification of nodal points in the eigen‐functions. These represent pivotal points through which sediment is transferred. The patterns of exchange vary considerably from slice to slice, reflecting change in the dominant beach processes from swash processes in the top of the beach to wave, tidal and current processes on the lower beach slope. Despite their disparity, similar periodicities are determined for the sediment exchanges in each slice. The amplitude spectra of the time series associated with each eigen‐function indicate that the exchanges take place at 24, 12 and 6 monthly periods.  相似文献   

珠江口盆地惠州地区新生界珠海组和珠江组重力流沉积特征^*          下载免费PDF全文

乔博  张昌民  李少华  杜家元  朱锐 《古地理学报》2013,15(1):69-76

通过2口井的岩心观察,在珠江口盆地惠州地区新生界珠海组和珠江组,发现有重力流沉积。该地区重力流沉积的主要特征是：滑塌构造发育广泛,是本区最主要的重力流沉积;液化沉积中泄水构造发育;浊流沉积中鲍马序列不完整。惠州地区的重力流沉积是三角洲前缘砂体垮塌再搬运沉积而形成的。在重力流沉积中还发现有潮汐作用的存在,潮汐作用和重力流沉积伴生。通过对惠州地区重力流沉积特征的研究,认为不能简单地将重力流沉积等同于浊流沉积;重力流沉积不仅局限在深水地区,在相对浅水地区也会发育。建议正确理解鲍马序列并予以合理使用。  相似文献   

On summer stratification and tidal mixing in the Taiwan Strait     

Jia ZHU  Jianyu HU  Zhiyu LIU 《Frontiers of Earth Science》2013,(2)

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滇西北衙地区中三叠统北衙组风暴沉积特征及其古地理意义          下载免费PDF全文

董黎阳  王剑  尹福光  王鹏  周业鑫 《沉积与特提斯地质》2013,(4):6-15

在滇西北衙地区中三叠统北衙组中首次发现风暴沉积,其表现为砾屑灰岩、网纹状灰岩的频繁互层,见丰富的风暴沉积构造。通过对笔架山及倒流箐剖面详细的野外观察及室内分析,识别出4种类型的风暴沉积序列。研究区风暴沉积的背景沉积为薄层网纹状灰岩,发育波状层理、鸟眼等构造,指示潮坪环境。潮坪风暴沉积在研究区的首次发现,对区内中三叠世古地理、古气候的研究具有重要的意义。  相似文献   

沙埕港湾口断面潮流及余流特征分析     

万凯  鲍献文  姚志刚  万修全  夏颖颖 《海洋与湖沼》2014,45(4):669-675

基于对沙埕港湾口断面的连续走航观测资料, 成功构建了沿走航断面的10 个站点的连续海流序列, 并分析了潮流、余流、潮通量等水文要素。分析结果表明, 沙埕港湾口水道潮流类型为正规半日潮流, 涨潮最先出现在中下层而落潮最先出现在上层, 涨(落)潮转流相差约为30min。水道内潮流为往复流, M₂ 和S₂ 分潮流流速较大, 倾角基本沿水道主轴方向。沙埕港湾口断面余流呈2 层结构, 10m 以浅基本为东南向余流流出湾口, 核心位于湾口断面南侧。10m 以深多为西北向流入湾内,入流核心位于湾口断面中部的底层区域。对潮通量的计算表明, 通过湾口进入沙埕港的潮通量约为1.63×10⁸m³。  相似文献   

长江河口水流输运时间研究     

王亚  何青  沈健 《海洋学报》2014,36(1):48-55

利用水龄理论的新方法,借助环境水动力学模型定量讨论了多年平均径流条件下长江河口径流和潮汐作用对河口水流输运时间的影响。研究给出了长江河口水流输运时间的时空格局:多年平均流量条件下,水流从徐六泾输出至河口(122.5°E)大约需要24d,南、北槽分流口以上河段水流输运时间主要由径流控制,水流输运时间为8d,向下至拦门沙滩顶水域由径流和潮汐共同控制,水龄为16d,说明最大浑浊带区域的水流输运速度较上下游为慢,从一个侧面阐述了最大浑浊带区域水动力的特征;长江河口水流输运时间存在明显的层化现象,表底层相差最大值可达6d。数值模拟试验结果表明长江河口的潮汐作用是影响河口水流输运时间的关键要素,河口巨大的进潮量增强河口水流交换能力并减小水流输运时间,从而显著影响随水体运动的物质输运格局。水流输运时间研究,不仅可以成功应用于河口水动力环境的量化研究,而且可以为泥沙输运及污染物输运等环境变化研究提供动力的基础。  相似文献   

A numerical study on the impact of tidal waves on the storm surge in the north of Liaodong Bay   总被引：1，自引：0，他引：1  

KONG Xiangpeng 《海洋学报(英文版)》2014,33(1):35-41

A storm surge is an abnormal sharp rise or fall in the seawater level produced by the strong wind and low pressure field of an approaching storm system.A storm tide is a water level rise or fall caused by the combined effect of the storm surge and an astronomical tide.The storm surge depends on many factors,such as the tracks of typhoon movement,the intensity of typhoon,the topography of sea area,the amplitude of tidal wave,the period during which the storm surge couples with the tidal wave.When coupling with different parts of a tidal wave,the storm surges caused by a typhoon vary widely.The variation of the storm surges is studied.An once-in-a-century storm surge was caused by Typhoon 7203 at Huludao Port in the north of the Liaodong Bay from July 26th to 27th,1972.The maximum storm surge is about 1.90 m.The wind field and pressure field used in numerical simulations in the research were derived from the historical data of the Typhoon 7203 from July 23rd to 28th,1972.DHI Mike21 is used as the software tools.The whole Bohai Sea is defined as the computational domain.The numerical simulation models are forced with sea levels at water boundaries,that is the tide along the Bohai Straits from July 18th to 29th（2012）.The tide wave and the storm tides caused by the wind field and pressure field mentioned above are calculated in the numerical simulations.The coupling processes of storm surges and tidal waves are simulated in the following way.The first simulation start date and time are 00：00 July 18th,2012; the second simulation start date and time are 03：00 July 18th,2012.There is a three-hour lag between the start date and time of the simulation and that of the former one,the last simulation start date and time are 00：00 July 25th,2012.All the simulations have a same duration of 5 days,which is same as the time length of typhoon data.With the first day and the second day simulation output,which is affected by the initial field,being ignored,only the 3rd to 5th day simulation results are used to study the rules of the storm surges in the north of the Liaodong Bay.In total,57 cases are calculated and analyzed,including the coupling effects between the storm surge and a tidal wave during different tidal durations and on different tidal levels.Based on the results of the 57 numerical examples,the following conclusions are obtained：For the same location,the maximum storm surges are determined by the primary vibration（the storm tide keeps rising quickly） duration and tidal duration.If the primary vibration duration is a part of the flood tidal duration,the maximum storm surge is lower（1.01,1.05 and 1.37 m at the Huludao Port,the Daling Estuary and the Liaohe Estuary respectively）.If the primary vibration duration is a part of the ebb tidal duration,the maximum storm surge is higher（1.92,2.05 and 2.80 m at the Huludao Port,the Daling Estuary and the Liaohe Estuary respectively）.In the mean time,the sea level restrains the growth of storm surges.The hour of the highest storm tide has a margin of error of plus or minus 80 min,comparing the high water hour of the astronomical tide,in the north of the Liaodong Bay.  相似文献