The influence of delta growth on paleo‐tidal flow: Fraser River delta,British Columbia—Part 3: Paleo‐tidal flows and delta growth

Abstract

Tidal flow patterns computed at various stages of the tide (high tide, falling tide, ebb tide, low tide, and flooding tide) and at different chronological stages (9000, 6000, 4500, 3000, and 2300 years B.P. and the present) using tidal numerical models were presented and interpreted in relation to sedimentary processes and the growth of the Fraser River delta during the past 9000 years. The overall tidal flows are least affected by the deltaic growth at high tide than at any other state of the tide. The net tidal flow with the overall northerly component has a sedimentary effect, in that there is an asymmetry in the transportation of silt and clay with more of these fine materials moved to the north of the delta than to the south. There is also independent seismic evidence for the existence of a tidal channel some 2000 B.P. between Point Roberts and the Fraser delta. This study attempted to link closely the sedimentary structure of the deltaic growth of the Fraser River with the physical oceanographic processes.     

Pore‐water pressure measurements: Mississippi delta submarine sediments

Abstract

A pore‐water pressure probe (piezometer) was implanted in Mississippi delta sediments at a preselected site (Block 28, South Pass area, 29°00´N, 89°15´W) 145 m from an offshore production platform (water depth approx. 19 m) in September 1975. Total pore‐water pressures (u_w ) were monitored for extended periods of time at depths of approximately 15 and 8 m below the mudline concurrently with hydrostatic pressures (u₈ ) measured at depths of 15 m and approximately 1 m below the mudline. Relatively high excess pore‐water pressures, u_e = (u_w ‐u₈ ), were recorded at the time of probe insertion measuring 99 kPa (14.4 psi) at 15 m and 50 kPa (7.3 psi) at 8 m. Six hours after the probe was implanted, excess pore pressures were still high at 81 kPa (11.8 psi, 15 m) and 37 kPa (5.4 psi, 8 m). Pore pressures appeared to become relatively constant at the 8‐m depth after 7 h had elapsed, and at the 15 m depth after 10–12 h. Excess pore‐water pressures averaged 72 kPa (10.4 psi, 15 m) and 32 kPa (4.6 psi, 8 m) prior to the initial effects of Hurricane Eloise, which passed in close proximity to the probe site. Significant variations in pressures were recorded during storm activity. As the effects of the storm subsided, excess pore‐water pressures began to decline slightly at the 15‐m depth; however, concurrently at the 8‐m depth, pore pressures began to increase gradually. During the period of 21–25 days after the probe was implanted, excess pore pressures appeared to become more constant, averaging 24 kPa (3.5 psi) at 15 m and 43 kPa (6.2 psi) at the 8‐m depth. The presence of methane, a common occurrence in these delta muds, may have influenced, or contributed to, the total pore‐water pressures measured during this experiment.     

In situ pore‐pressure measurement in Mississippi delta front sediments

Abstract

A differential piezometer was used to monitor excess pore pressure in the soft clayey seafloor sediments of Block 28, South Pass, Mississippi delta, from September 1975 to March 1976. An ambient excess pore pressure of about 32 kPa was measured at a depth of 6.4 m below the mudline in a water depth of 19 m. Storm‐wave‐generated cyclic fluctuations of ± 4 kPa about the ambient were measured during Hurricane Eloise. Irregular, long‐period, small‐amplitude fluctuations in excess pore pressures persisted for 4 days following the storm. An effective stress analysis was made by using excess pore pressures; in situ field vane‐shear strength, t _fv, measurements; and laboratory wet unit weights measured by Lehigh and NOAA. The effective stress of the SEA‐SWAB site soil was calculated to be zero to a depth of about 6 m, below which it increased to 3.5 kPa at a depth of 15 m. Values of c´ = 4.6 kPa, ?´ = 56°, and T _FV/σ_vo(c/p) =0.1–0.2 were calculated, and it was concluded that these data do not represent the in situ condition of the soil because of the probability that the measured soil properties were affected by the presence of gas. However, it is clear that the soil is significantly underconsolidated.     

Shallow‐water sand bars on the Ruamahanga River delta Lake Wairarapa

In the shallow waters of Lake Wairarapa, a multiple series of sublimnic sand bars has developed around the outer edge of the Ruamahanga River delta. Shore‐normal movements in bar positions occur in response to changing lake level and wave conditions. Unlike many bar systems, most of these movements are lakeward of the breaker zone. Sediments on the bar crests are well‐sorted fine sands; the troughs are a mixture of fine sand and mud settling out of the turbid lake waters during calm conditions.     

The influence of bioturbation on sandy reservoirs: the delta front sand of the lower Zhujiang Formation,Baiyun Depression,Zhujiang River Mouth Basin

Ichnofossils are well developed in clastic rock reservoirs in marine and transitional facies, which can considerably change the physical properties of the reservoir. However, this influence is not well understood, raising an important problem in the effective development of petroleum reservoirs. This paper analyzes continental shelf margin delta reservoirs through core observation, cast thin section observation and reservoir physical property test. Some important scientific insights are obtained...     

Hydrochemical conditions of the “Chistaya Banka” polygon in the Volga’s avant delta

Characteristics of different types of river drainage were obtained during studies of a polygon in the near-mouth part of the Volga River in 2000–2003: “fast” (flowing through deep channels) and “slow” (that which passes through the littoral parts of the delta (1–2 m)). The low current velocities (lower than in the channel waters by a factor of ten), the abundance of water vegetation, and the strong heating of the waters lead to the high intensity of the biochemical processes. Therefore, the chemical composition of the waters is subjected to significant transformation with intensity so high that it allows comparing these regions with some sort of “bioreactor.” These changes influence the dissolved oxygen and various forms of carbon content.     

Does sedimentary organic delta 13C record variations in quaternary ocean [CO2(aq)]?

Ocean surface water [CO2(aq)] variations based on glacial/interglacial changes in sediment delta 13Corg are shown to compare favorably with reconstructions based on ice core [CO2]. In particular, an approximate 80 microatmospheres increase in atmospheric pCO2 during the last glacial-interglacial transition is calculated to correspond to a 3-4 micromolar increase in ocean surface water [CO2(aq)] at atmospheric equilibrium. A widespread marine delta 13Corg decrease of 1-2% accompanied this event and was not preceded by an equivalent isotopic change in surface water total dissolved inorganic carbon. These observations support the hypothesis that [CO2(aq)] influences photosynthetic isotope fractionation between marine inorganic and organic carbon pools, and therefore that plankton/sediment delta 13Corg may serve as a proxy for surface water [CO2(aq)].     

Change of deltaic depositional environment and its impacts on reservoir properties—A braided delta in South China Sea

Depositional environment can change through geological time. This paper describes a delta that evolved from river-dominated into tide-dominated. The delta is located in the Ya13-1 field of the South China Sea. Understanding the change that occurred in the deltaic setting is important because the change in depositional environments led to changes in spatial distribution of facies and other rock properties.The Oligocene sediments of the third member of the Lingshui Formation in the Ya13-1 field were deposited in a river-dominated delta, and later impacted by marine flooding, fluvial and tidal currents. As a result of these different influences, the early-stage depositional micro-facies and the sandbody distributions are quite different from those of the later stage. At the early stage, fluvial influences prevailed, resulting in a fluvial-dominated delta plain and deposition of many linguoid sand bars in the delta front. During the late stage of deposition, tide-dominated delta fronts were developed extensively and finger sand bars deposited abundantly in the delta front as a result of the tidal influence.Ya13-1 gas field is laterally divided into two large subareas and vertically into eight stratigraphic packages. Because of the different influences of marine flooding that resulted in different interbeds and intercalations, the number of stratigraphic packages in the south is different from that in the north. The change of deltaic depositional environments also resulted in different reservoir properties between the northern and southern regions as the reservoir properties of mouth bars are generally better than distributary channels. These depositional characteristics significantly impact the development of the field.     

Dramatic changes in the horizontal structure of mangrove forests in the largest delta of the northern Beibu Gulf,China

The horizontal structure of mangrove forests is an important characteristic that reflects a significant signal for coupling between mangroves and external drivers. While the loss and gain of mangroves has received much attention, little information about how the horizontal structure of mangrove forests develops from the seedling stage to maturity has been presented. Here, remote sensing images taken over approximately 15 years, UVA images, nutrient elements, sediments, and Aegiceras corniculatum...     

Sand bodies and incised valleys within the Late Quaternary Sanaga–Nyong delta complex on the middle continental shelf of Cameroon

Seismic data and sediment cores collected offshore from the Sanaga River and Nyong River mouths were used to analyse a loose mantle of yellow to reddish sandy gravel with a range of fluvial and deltaic characteristics cropping out in the middle part (25–65 m water depth) of the continental shelf of Cameroon. Contrary to most of the Atlantic shelves, where the lowstand systems tract was destroyed by erosion, we found 80–120 ms (60–90 m) of sediment mainly in the middle part of the shelf, which correspond credibly to MIS 2–4. Fluvial paleodrainage systems are preserved beneath the shelf and individual filled channels with planar infillings were mapped that cross the shelf along two surfaces of erosion. These incisions suggested westerly and northwesterly drainage shifts during presumed lowered base level. The presence of closely spaced channel fills suggests repeated avulsion of a single stream during a long-lasting sub-aerial erosion period. The seismic facies of these Pleistocene deposits distinguish themselves clearly from well-stratified older strata showing deformation (Pliocene) or intense folding (Miocene). The orientation of the paleovalleys appears strongly controlled by the N60°E trending cross faults within Mesozoic–Cenozoic strata.     

Dramatical hydro-sedimentary changes induced by bamboo fences over mangrove tidal flat of the largest delta in Beibu Gulf,southwestern China

Mangrove forest is one of the most important ecological and environmental resources by effectively promoting tidal flat deposition and preventing the coastal region from typhoon. However, there have been mass loss of mangrove forests due to anthropogenic activities. It is an urgent need to explore an effective way for mangrove restoration. Here, three rows of bamboo fences with hydro-sedimentary observation set over Aegiceras corniculatum mangrove tidal flat of the Nanliu Delta, the largest delt...     

Bulk organic δC and C/N as indicators for sediment sources in the Pearl River delta and estuary,southern China

Preservation of organic matter in estuarine and coastal areas is an important process in the global carbon cycle. This paper presents bulk δ¹³C and C/N of organic matter from source to sink in the Pearl River catchment, delta and estuary, and discusses the applicability of δ¹³C and C/N as indicators for sources of organic matter in deltaic and estuarine sediments. In addition to the 91 surface sediment samples, other materials collected in this study cover the main sources of organic material to estuarine sediment. These are: terrestrial organic matter (TOM), including plants and soil samples from the catchment; estuarine and marine suspended particulate organic carbon (POC) from both summer and winter. Results show that the average δ¹³C of estuarine surface sediment increases from −25.0 ± 1.3‰ in the freshwater environment to −21.0 ± 0.2‰ in the marine environment, with C/N decreasing from 15.2 ± 3.3 to 6.8 ± 0.2. In the source areas, C₃ plants have lower δ¹³C than C₄ plants (−29.0 ± 1.8‰ and −13.1 ± 0.5‰ respectively). δ¹³C increases from −28.3 ± 0.8‰ in the forest soil to around −24.1‰ in both riverbank soil and mangrove soil due to increasing proportion of C₄ grasses. The δ¹³C_POC increases from −27.6 ± 0.8‰ in the freshwater areas to −22.4 ± 0.5‰ in the marine-brackish-water areas in winter, and ranges between −24.0‰ in freshwater areas and −25.4‰ in brackish-water areas in summer. Comparison of the δ¹³C and C/N between the sources and sink indicates a weakening TOM and freshwater POC input in the surface sedimentary organic matter seawards, and a strengthening contribution from the marine organic matter. Thus we suggest that bulk organic δ¹³C and C/N analysis can be used to indicate sources of sedimentary organic matter in estuarine environments. Organic carbon in surface sediments derived from anthropogenic sources such as human waste and organic pollutants from industrial and agricultural activities accounts for less than 10% of the total organic carbon (TOC). Although results also indicate elevated δ¹³C of sedimentary organic matter due to some agricultural products such as sugarcane, C₃ plants are still the dominant vegetation type in this area, and the bulk organic δ¹³C and C/N is still an effective indicator for sources of organic matter in estuarine sediments.     

Sur l'origine et l'âge des levées sédimentaires profondes: Cas du delta sous-marin du Rhône (Méditerranée nord-occidentale)

The interpretation of sedimentological and geochronological results lead us to the conclusion that the sedimentary levees flanking the deep-sea channels of the Rhône deep-sea fan are made up of various kinds of turbidites originating from different coastal areas and were deposited during the Quaternary glacial epochs.     

缺水:危机四伏 开源:面向大海

我国是世界上12个严重缺水国家之一,人均淡水占有量仅是世界人均占有量的四分之一。据有关部门统计,目前,我国668个大中城市中,就有400个缺水,100个严重缺水。华北、东北、西北地区,连年干旱缺雨;南方地区水体污染严重,使水源性缺水成为城市供水的突出问题。淡水资源短缺正严重制约着我国经济的发展。解决我国水资源短缺问题已是全国上下的共识;也是摆在全国人民面前亟待解决的重大课题,当前的问题是加快落实的步伐。     

陈水扁:口出狂言

陈水扁的大陆政策台独色彩厚重。在两岸关系定位上,称“台湾与中国是两个互不隶属、互不统治、互不管辖的国家”。他说“中华人民共和国从未与台湾发生政治关系,无权参预决定台湾归属与前途”,要“推动台湾与中国关系全面正常化”。     

A Review of: “Place Matters:”

Oceanography, Units 1–16 edited by J. Stewart (Open University Press, 1977), 755 pp.

The Thermohaline Fine Structure of the Ocean by K. N. Fedorov (New York: Pergamon Press, Pergamon Marine Series. Volume 2, 1978). Translated from Russian by D. A. Brown, Technical Editor: J. S. Turner, 170 pp., no price listed.

The Ocean Basins and Margins edited by Alan E. M. Nairn and Francis G. Stehli, with William H. Kanes (New York: Plenum Press, Vol. 1–4A, 4B, 1973, 1979, 1975, 1977, and 1978) approx. 3,000 pp.

Recent Crustal Movements, 1977 edited by C.A. Whitten, R. Green, and B.K. Meade (New York: Elsevier Scientific Publishing Co., 1979), 663 pp., hardcover, $78.00.

The Alaskan Shelf‐Hydrographic, Sedimentary, and Geotechnical Environment by Ghanshyam Datt Sharma (New York: Springer Verlag, 1979), 498 pp., hardcover, $29.80.     

电影:《潜艇总动员4:章鱼奇遇记》

<正>导演:何子力编剧:何子力/柯德涛主演:蒋可/王晓彤/李晔/孙宁芳/范楚绒/洪海天/谢元真/胡谦/刘北辰/周南飞/严丽祯/谭满堂/翟巍类型:喜剧/动画/冒险制片国家,地区:中国大陆语言:汉语普通话上映日期:2014-05-30(中国大陆)片长:80分钟又名:潜艇总动员4:章鱼保罗故事讲述了章鱼保罗一家、潜艇阿力、贝贝以及海马家族一起与邪恶的独眼鲨斗智斗勇、最终获胜的冒险故事,其间章鱼一家的各种奇遇不仅惊现、刺激,而且充满了温馨和感动。爸爸章鱼保罗因为欠债     

新概念:海洋高科技

美国未来学家托夫勒是首先提出海洋高科技这个概念的。70年代初,他在论述第三次浪潮时提出,海洋工程将和航天工程一道成为新产业的骨干产业。这一观点很快被世界许多国家的政治家、经济学家、科学家所接受。日本在80年代初制定国家科学技术发展战略时明确提出,海洋开发技术、原子能技术、空间开发技术等三大科技为未来日本优先发展的现代高新技术产业,并将深海勘探、水下作业、海水增     

“礼尚往来”:

湖北宜昌的朱万礼朋友提议说:因为全年的杂志已订阅,有奖知识问答答对的话可不可以送以往的杂志。     

下篇:生还者说

“11.24特大海难”的生还者仅有22人。这22人中,有13人是在“大舜”号沉没的海面获救的,其中12人被686船救起,另一人是海军某基地岸勤部政委,今年44岁,他被“烟救”13号拖轮援救。其余9人是游到岸边,或被海浪冲到海滩获救,个别人冻僵后,还有微弱心跳,被医生救活。今年26岁的董颖小姐,现住青岛市,她是位冬泳爱好者,当救援者搬运一个个被冲到岸滩的遇难者时,她从海滩上站了起来,还走了两