基于PSR模型的滨海湿地生态系统健康评价——以辽河三角洲滨海湿地为例

以PSR评价模型为基础,选取人口、经济、环境、资源开发、政策法规和管理决策等指标,诊断和评估滨海湿地生态系统在湿地开发和环境污染等一系列人类活动干扰下的健康现状,将健康等级分为优、良好、一般、较差和极差等5级.结果表明,辽河三角洲滨海湿地生态系统健康状态一般,由于过度的围垦开发,自然湿地面积在1988～2007年间减少了11 072 hm2,其中,碱蓬湿地减少了75%(2 440 hm2),而水产养殖场增加了182%(9 359 hm2).流域及沿岸的工农业排污致使评价区域内水体污染较严重,COD、TIN、活性磷酸盐和Pb的含量分别达到3.06 mg/dm3、795.45、44.01和6.46μg/dm3,普遍为四类或劣四类水质.环境的恶化,导致碱蓬、芦苇湿地面积萎缩,鸟类种类和数量不断减少,底栖生物多样性降低.并据此提出了辽河三角洲滨海湿地的管理与保护措施.     

Revisiting and rethinking regional urbanization in Changjiang River Delta, China

China is entering a critical and accelerating phase of urbanization.As one of the most urbanized regions in China,the Changjiang(Yangtze)River Delta has experienced dramatic urbanization and urban transformation.However,in the recent years,many changes have taken place in this region and there is limited attention to the regional urbanization path evolution,its problems and the way to solve these problems.Therefore,we should revisit the urbanization process in the Changjiang River Delta again.In this paper,we revisited urbanization paths of the Changjiang River Delta by data analysis,influence factors of urbanization by the Gray Relational Analysis,and major challenges to urbanization of the Changjiang River Delta by theoretical considerations.We found that the urbanization of the Changjiang River Delta had experienced several stages of large-scale spatial and urban system restructuring.Within the Changjiang River Delta,Shanghai,Zhejiang and Jiangshu had experienced different urbanization path with local characteristics.But with their development model gradually converging,their urbanization model is also converging.We also found that the major influence factors affecting the Changjiang River Delta urbanization were dynamic change and urbanization was driven by different key factors in different socio-economic development stages.Meanwhile,the Changjiang River Delta urbanization is facing many problems such as existing institutional arrangements,including the hukou(household registration)system and others which can not meet the needs of current socioeconomic development and urbanization.Therefore,it is imperative to promote institutional innovation and adopt a new urbanization development strategy for the sake of the orderly and sustainable urbanization development in the Changjiang River Delta.     

应用岩性统计方法判别沉积相*——以珠江口盆地三角洲沉积为例

传统的沉积相分析方法人为影响因素较大,对于相同的沉积构造、曲线形态及地震反射特征,不同人可能会有不同的认识,而岩性相对比较容易识别,并且能通过精密的仪器准确获得,因此,利用岩性数据进行沉积相判别,可以避免沉积相分析过程中人为认识相标志不同造成的差异。作者以珠江口盆地三角洲沉积的岩性数据为基础,通过对能够反映沉积速率、沉积物供给量及沉积水动力条件的不同岩性地层的厚度和层数的统计,选取单层厚度、地层厚度比、出现频率及层数比等统计参数,以交汇图、岩性百分含量三角图及箱线图为依托,最终建立各沉积亚相的定量判别标准。通过检验,其准确率在75％左右,可见该方法基本可行,为沉积相定量化研究提供了一种可供借鉴的方法。     

Sedimentary evolution of the Late Eocene Vernet lacustrine system (South-Central Pyrenees). Tectono-climatic control in an alluvial-lacustrine piggyback basin

A complete third-order tectono-sedimentary cycle filled the Vernet lacustrine piggyback basin during the late Eocene. The depositional sequence can be subdivided into five units or systems tracts with distinct architectural frameworks, which developed a progressive unconformity. Sedimentary infilling of the piggyback basin began with retrogradational alluvial fans and fluvio-alluvial deposits being deposited, arranged in two thinning- and fining-upward cycles during the uplifting and emplacement of the southernmost Pyrenean thrusts, and with three thickening- and coarsening-upward progradational floodplain and lacustrine cycles, during the quiescence of the southernmost thrusts, at the same time as the emplacement of several northernmost thrusts of the southern Pyrenees. The facies associations identified represent different depositional environments in a sheetflow-dominated system, including playa-lake deposits, floodplain deposits, sheetflow fluvial deposits and sheet deltas in ephemeral to shallow lacustrine settings. Fourth and fifth order arid/semi-arid climatic cycles can be recognized, driven either by orbital obliquity and precessional forcing (Milankovitch cyclicity), insolation cycles or possibly subprecessional autogenic mechanisms related to the emplacement of northern thrusts and the consequent changes in the drainage basin. Arid periods are recorded by sheetflood fluvial, ephemeral lacustrine or terminal splay deposits, with abundant medium-to-coarse-grained sandstone packages in red-to-grey mudstones, a product of unconfined or low-confined sheetflows or hyperconcentrated flows, with bedload and suspended load, during flood episodes, at times of lake lowstand. Semi-arid periods are recorded as relative highstand lacustrine deposits, including grey-to-white mudstones deposited in prodelta environments and fine-grained sheet sandstone units sedimented in a delta front (with minor channels and extensive sheet lobes) and prodelta environments in shallow lakes, from sheetflood events.     

世界大都会区城际轨道交通的发展规律

通过选取世界255 个大都会区城际轨道交通样本,对城际轨道交通的发展历程、空间分布和网络特征进行了规律性总结;在此基础上,进一步分析城际轨道交通规模与大都会区人口、用地、经济规模之间的相关关系,构建多个回归模型;最后,应用于珠江三角洲区域,对其城际轨道交通的规模和布局进行预测。模型显示,世界大都会区城际轨道交通的规模与经济的相关程度最高,其次是人口和用地,而人均城际轨道规模与人均GDP和人口密度呈指数相关,其中,与人均GDP正相关,与人口密度负相关。应用模型得到,珠三角城际轨道交通的规划规模超前于现有经济发展水平,但低于人口发展水平。近期应重点建设广州、佛山、深圳、东莞4 个城市重要节点的城际轨道交通,构建广佛和广深两条走廊,并联系珠海、中山、肇庆、惠州、江门的中心城区,形成以广州为中心的放射状布局;远期则需要进一步加大广州、深圳、佛山、东莞、珠海、中山的线网密度,扩大线网的覆盖范围,并对外围的肇庆、惠州和江门适当增加联系的节点,最终形成网络状布局。     

OSL dating of fine-grained quartz from Holocene Yangtze delta sediments

Holocene flood events in the Yangtze River are associated with variations in East Asian Summer Monsoon (EASM) precipitation, and so Yangtze delta sediments may preserve information about the frequency and magnitude of EASM precipitation. These flood/drought cycles of the EASM directly affect the living standards of East Asian population. However, despite its importance, little chronological control is available for the Yangtze Delta sediments; because biogenic carbonate only occurs sporadically, it has proved the difficulty to discuss sedimentation mechanisms and rates in any detail.In 2013 two sediment cores (YD13-G3 and H1) were taken from the Yangtze subaqueous delta to investigate precipitation history. In this study, we investigate the potential of quartz OSL dating of the fine silt fraction (fine-grained quartz; 4–11 μm) from these cores to estimate the depositional age of the sediments. We test whether: (1) Yangtze subaqueous delta sediments contain quartz with suitable characteristics for dating, and (2) quartz grains are well-bleached during/before the transportation process, by examining a modern analogue of suspended particulate matter, and by cross-checking with the doses derived from infrared stimulated luminescence (IRSL) signals (both IR₅₀ and pIRIR₁₆₀) from feldspar in polymineral fine grains. We find that both the quartz and feldspar luminescence characteristics are satisfactory (quartz dose recovery ratio 1.067 ± 0.004; n = 250, pIRIR₁₆₀ dose recovery ratio 1.01 ± 0.02; n = 151). Modern suspended particulate matter has measured quartz equivalent doses between 0.1 and 0.2 Gy, suggesting that this material was sufficiently bleached during/before transportation to allow dating of Holocene sediments (mean dose rates of ∼3 Gy ka⁻¹). OSL ages of 44 samples from the 2 cores show apparently rapid accumulation at ∼6 ka between 9.65 and 5.50 m in core H1 and ∼2 ka throughout core G3 and between 5.0 and 0.0 m in core H1. The pIRIR₁₆₀ signals suggest less light exposure of the core top sediments and of those from the transition layer between ∼6 ka to ∼2 ka, although there is no evidence for incomplete bleaching of quartz. The question remains as to whether significant deposition took place only at these two times, or whether the record has been disturbed by erosion/reworking.     

准噶尔西北缘玛北地区扇三角洲砂砾岩岩相分类及储集意义

准噶尔盆地西北缘三叠系处于大型逆冲推覆断裂带,盆地边缘同生断裂构造活动强烈,发育砂砾岩为主的扇三角洲沉积体系。通过对玛北地区三叠系百口泉组砂砾岩储层取芯段岩芯观察和描述、岩石薄片、扫描电镜、测井以及储层物性数据的分析,结合砂砾岩岩石构成、层理类型、沉积层序和测井曲线响应特征,对准噶尔盆地西北缘砂砾岩体岩性进行精细刻画,建立岩相模式,划分出同沉积相(微相)相符的11种岩相:其中扇三角洲前缘水下河道砂砾岩相、扇三角洲平原辫状河道砂砾岩相叠置连片展布,是最有利的储集体;扇三角洲前缘水下主河道砾岩相、水下河道末端砂岩相及河口坝—远砂坝砂岩相分布局限,储集性良好,为有利"甜点"区;水上泥石流砾岩相和水下泥石流砂砾岩相与扇三角洲平原和前缘分流河道间储集性较差的细粒砂泥岩相组成百口泉组油藏致密的顶底板;前扇三角洲粉砂岩相和泥岩相可作为良好的区域性盖层。不同的岩相类型及沉积条件提供了准噶尔西北缘百口泉组大规模低渗透岩性油气藏优良的储盖组合及顶底板条件。     

Coupled ‘storm‐flood’ depositional model: Application to the Miocene–Modern Baram Delta Province,north‐west Borneo

The Miocene to Modern Baram Delta Province is a highly efficient source to sink system that has accumulated 9 to 12 km of coastal–deltaic to shelf sediments over the past 15 Myr. Facies analysis based on ca 1 km of total vertical outcrop stratigraphy, combined with subsurface geology and sedimentary processes in the present‐day Baram Delta Province, suggests a ‘storm‐flood’ depositional model comprising two distinct periods: (i) fair‐weather periods are dominated by alongshore sediment reworking and coastal sand accumulation; and (ii) monsoon‐driven storm periods are characterized by increased wave‐energy and offshore‐directed downwelling storm flow that occur simultaneously with peak fluvial discharge caused by storm precipitation (‘storm‐floods’). The modern equivalent environment has the following characteristics: (i) humid‐tropical monsoonal climate; (ii) narrow (ca <100 km) and steep (ca 1°), densely vegetated, coastal plain; (iii) deep tropical weathering of a mudstone‐dominated hinterland; (iv) multiple independent, small to moderate‐sized (10² to 10⁵ km²) drainage basins; (v) predominance of river‐mouth bypassing; and (vi) supply‐dominated shelf. The ancient, proximal part of this system (the onshore Belait Formation) is dominated by strongly cyclical sandier‐upward successions (metre to decametre‐scale) comprising (from bottom to top): (i) finely laminated mudstone with millimetre‐scale silty laminae; (ii) heterolithic sandstone–mudstone alternations (centimetre to metre‐scale); and (iii) sharp‐based, swaley cross‐stratified sandstone beds and bedsets (metre to decimetre‐scale). Gutter casts (decimetre to metre‐scale) are widespread, they are filled with swaley cross‐stratified sandstone and their long axes are oriented perpendicular to the palaeo‐shoreline. The gutter casts and other associated waning‐flow event beds suggest that erosion and deposition was controlled by high‐energy, offshore‐directed, oscillatory‐dominated, sediment‐laden combined flows within a shoreface to delta front setting. The presence of multiple river mouths and exceptionally high rates of accommodation creation (characteristic of the Neogene to Recent Baram Delta Province; up to 3000 m Ma⁻¹), in a ‘storm‐flood’‐dominated environment, resulted in a highly efficient and effective offshore‐directed sediment transport system.     

Transition from storm wave‐dominated outer shelf to gullied upper slope: The mid‐Pliocene Orinoco shelf margin,South Trinidad

Shelf‐edge deltas are a key depositional environment for accreting sediment onto shelf‐margin clinoforms. The Moruga Formation, part of the palaeo‐Orinoco shelf‐margin sedimentary prism of south‐east Trinidad, provides new insight into the incremental growth of a Pliocene, storm wave‐dominated shelf margin. Relatively little is known about the mechanisms of sand bypass from the shelf‐break area of margins, and in particular from storm wave‐dominated margins which are generally characterized by drifting of sand along strike until meeting a canyon or channel. The studied St. Hilaire Siltstone and Trinity Hill Sandstone succession is 260 m thick and demonstrates a continuous transition from gullied (with turbidites) uppermost slope upward to storm wave‐dominated delta front on the outermost shelf. The basal upper‐slope deposits are dominantly mass‐transport deposited blocks, as well as associated turbidites and debrites with common soft‐sediment‐deformed strata. The overlying uppermost slope succession exhibits a spectacular set of gullies, which are separated by abundant slump‐scar unconformities (tops of rotational slides), then filled with debris‐flow conglomerates and sandy turbidite beds with interbedded mudstones. The top of the study succession, on the outer‐shelf area, contains repeated upward‐coarsening, sandstone‐rich parasequences (2 to 15 m thick) with abundant hummocky and swaley cross‐stratification, clear evidence of storm‐swell and storm wave‐dominated conditions. The observations suggest reconstruction of the unstable shelf margin as follows: (i) the aggradational storm wave‐dominated, shelf‐edge delta front became unstable and collapsed down the slope; (ii) the excavated scars of the shelf margin became gullied, but gradually healed (aggraded) by repeated infilling by debris flows and turbidites, and then new gullying and further infilling; and (iii) a renewed storm wave‐dominated delta‐front prograded out across the healed outer shelf, re‐establishing the newly stabilized shelf margin. The Moruga Formation study, along with only a few others in the literature, confirms the sediment bypass ability of storm wave‐dominated reaches of shelf edges, despite river‐dominated deltas being, by far, the most efficient shelf‐edge regime for sediment bypass at the shelf break.     

From outwash to coastal systems in the Portneuf–Forestville deltaic complex (Québec North Shore): Anatomy of a forced regressive deglacial sequence

Deglacial sequences typically include backstepping grounding zone wedges and prevailing glaciomarine depositional facies. However, in coastal domains, deglacial sequences are dominated by depositional systems ranging from turbiditic to fluvial facies. Such deglacial sequences are strongly impacted by glacio‐isostatic rebound, the rate and amplitude of which commonly outpaces those of post‐glacial eustatic sea‐level rise. This results in a sustained relative sea‐level fall covering the entire depositional time interval. This paper examines a Late Quaternary, forced regressive, deglacial sequence located on the North Shore of the St. Lawrence Estuary (Portneuf Peninsula, Québec, Canada) and aims to decipher the main controls that governed its stratigraphic architecture. The forced regressive deglacial sequence forms a thick (>100 m) and extensive (>100 km²) multiphased deltaic complex emplaced after the retreat of the Laurentide Ice Sheet margin from the study area ca 12 500 years ago. The sedimentary succession is composed of ice‐contact, glaciomarine, turbiditic, deltaic, fluvial and coastal depositional units. A four‐stage development is recognized: (i) an early ice‐contact stage (esker, glaciomarine mud and outwash fan); (ii) an in‐valley progradational stage (fjord head or moraine‐dammed lacustrine deltas) fed by glacigenics; (iii) an open‐coast deltaic progradation, when proglacial depositional systems expanded beyond the valley outlets and merged together; and (iv) a final stage of river entrenchment and shallow marine reworking that affected the previously emplaced deltaic complex. Most of the sedimentary volume (10 to 15 km³) was emplaced during the three‐first stages over a ca 2 kyr interval. In spite of sustained high rates of relative sea‐level fall (50 to 30 mm·year^?1), delta plain accretion occurred up to the end of the proglacial open‐coast progradational stage. River entrenchment only occurred later, after a significant decrease in the relative sea‐level fall rates (<30 mm·year^?1), and was concurrent with the formation and preservation of extensive coastal deposits (raised beaches, spit platform and barrier sands). The turnaround from delta plain accretion to river entrenchment and coastal erosion is interpreted to be a consequence of the retreat of the ice margin from the river drainage basins that led to the drastic drop of sediment supply and the abrupt decrease in progradation rates. The main internal stratigraphic discontinuity within the forced regressive deglacial sequence does not reflect changes in relative sea‐level variations.