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.     

三江平原沼泽湿地格局变化及影响因素分析

为揭示湿地变化剧烈区湿地格局变化过程及规律,利用GIS和RS技术,结合地学信息图谱与空间自相关方法,对1954-2010年三江平原沼泽湿地格局变化及其影响因素进行研究。结果表明:1954-2010年三江平原沼泽湿地面积逐渐减少,88.7%的沼泽湿地丧失,湿地斑块数量呈先增加后减少的趋势;三江平原沼泽湿地的空间聚集性逐渐降低,且空间格局由集中连片分布转变为零星散布;降雨量减少、气温升高及径流量减少,是造成沼泽湿地减少的主要原因之一,地形地貌影响到沼泽湿地的丧失程度,以海拔20~80 m的沼泽湿地面积丧失最多。三江平原沼泽湿地的丧失同时受农业开发、居民点分布、湿地保护区建设影响,距居民点越近,沼泽湿地面积丧失呈指数增加,距保护区越近,沼泽湿地面积丧失越多。     

阿尔金断裂带东段古生代花岗岩浆作用及其大陆动力学意义

造山带花岗岩浆作用一直是地学的重要研究方向, 它记录了地球动力学深部过程的信息, 开展深入的研究工作可以更好的了解板块汇聚环境的陆壳生长和再造以及壳幔之间的相互作用。北祁连造山带是一典型的早古生代造山带, 先后经历了洋盆的打开到闭合, 敦煌地块则是主要由前寒武纪TTG片麻岩和变质表壳岩组成。北祁连造山带和敦煌地块分别位于阿尔金断裂带东段的东南侧和西北侧, 且均出露有大面积的古生代花岗岩体。本文以阿尔金主断裂两侧产出的花岗岩类为研究对象, 涉及北祁连造山带中的赵家庄二长花岗岩, 石包城复式岩体(花岗岩、正长花岗岩和花岗闪长岩)和红柳河花岗岩, 敦煌地块中的党河水库花岗闪长岩、沙枣园二长花岗岩、安盆沟复式岩体(正长花岗岩和花岗岩)以及小草湖似斑状花岗岩。通过对上述花岗岩体的岩相学、锆石U-Pb年代学、地球化学和锆石Hf同位素的研究, 取得了新的认识:     

东濮凹陷沙三段正常三角洲沉积中遗迹化石及意义

通过对钻井岩心的观察和遗迹化石的鉴定,在东濮凹陷古近纪沙河街组沙三段发现遗迹化石10属15种,包括:Skolithos vertivalis,Skolithos linearis,Skolithos isp.,Palaeophycus tubularis,Palaeophycus isp.,Planolites montanus,Planolites beverlegensis,Planolites isp.,Mermoides isp.,Taenidium isp.,Teichichnus isp.,Helminthoidichnites tenuis,Helminthopsis isp.,Beaconites isp.和Thalassinoides isp.。根据岩性特征、沉积构造和遗迹化石的组成、分布特征,研究区沙三段主要发育正常三角洲前缘亚相、前三角洲亚相,并划分了反映不同沉积环境和水体深度的2种遗迹组合,分别为Palaeophycus-Planolites遗迹组合和Planolites-Helminthoidichnites遗迹组合。     

交通地理信息系统中的时空动态分段模型研究

动态分段技术是交通地理信息系统(GIS-T)中一项重要的线性要素动态显示与分析技术,该文提出了一种时空动态分段模型,使动态分段系统的组成成分融入时态因素,并将属性的时态信息作为属性信息表的字段存储,通过时态地理信息系统技术完成物理段的时态变化。利用统一建模语言(UML)的类图设计方式开发了物理模型,描述了时空动态分段模型中对象之间的关系,并定义了必要的属性和操作;同时基于线性参照系统(LRS)表达空间实体的方法,概括了模型中所涉及到的主要拓扑关系。实验表明,时空动态分段模型弥补其他模型将时空参考分为时间参考和空间参考所产生的不足,而且更明确地将多重属性和物理实体有机结合起来。     

青海省宗马海湖地区始新—中新统干柴沟组沉积相探析

宗马海湖地区位于柴达木盆地的北缘,有着良好的油气、钾盐勘探前景。该文在分析柴达木盆地北缘宗马海湖地区区域地质背景的基础上,对始新-中新统干柴沟组的岩石学特征、地层特征、沉积构造特征及沉积相等进行了较为深入的研究。干柴沟组沉积相以滨湖亚相、浅湖亚相及扇三角洲相为主,滨-浅亚湖沉积发育最为广泛。扇三角洲相具牵引流、重力流沉积特征,中、粗粒碎屑岩为主;滨湖亚相具较高流态的水动力条件,以砂和粉砂为主,砂泥间互层频繁;浅湖亚相以泥质沉积为主,显示低能的浅水静态沉积作用。文中总结了研究区干柴沟组沉积期沉积相演化特征,建立了干柴沟沉积相平面展布图;干柴沟组沉积相的形成与季节性变化息息相关,湖水上涨、后退导致北部山区扇三角洲较发育,而南部区域始终位于滨、浅湖环境中。     

3S在耕地保护动态监管中的关键技术研究

随着3S技术的发展和逐渐成熟,应用也越来越多,该文主要利用RS技术快速获取遥感卫星影像数据,利用GPS技术获取动态监测数据,利用GIS的可视化技术和强大的空间分析功能,整合建立全省整治项目数据库,依托于省国土资源内网,遵循山东省国土资源系统"一个平台,两个市场"实施方案技术要求,充分利用现有网络、软硬件等基础设施,建立省、市、县三级国土资源耕地保护管理全业务、全流程的网上运行和全程监管机制,构建全省统一的耕地保护动态监管网络体系,实现了对耕地保护的动态监管,为耕地的"先补后占,占补平衡"提供了可靠的保障。     

青藏高原湖泊面积动态监测

高原湖泊的动态变化对区域水循环具有重要影响。受全球气候变化的影响,青藏高原湖泊自20世纪90年代开始呈现剧烈扩张趋势。为揭示近年来青藏高原湖泊面积的时空变化规律,本文提出了一种改进的半自动湖泊提取算法,结合环境减灾卫星（HJ-1A/1B）和Landsat系列卫星影像数据,对青藏高原内流流域中面积大于50 km²的127个湖泊进行了连续6年的动态监测,并分析了该区域2009-2014年湖泊面积时空变化特征。研究结果表明,该区域湖泊整体呈现显著扩张趋势,年均变化速率为231.89 km²yr^-1（0.87 %yr^-1）,6年间湖泊面积扩张速率有所减缓。其中,扩张湖泊有104个,收缩湖泊有23个,变化速率分别为271.08 km²yr^-1（1.02 % yr^-1）和-39.19 km²yr^-1（-0.15 %yr^-1）。不同区域湖泊面积变化具有明显差异,主要表现为东部及北部大部分区域湖泊扩张,南部地区大部分湖泊面积稳定,萎缩湖泊主要分布于研究区四周。最后,本文通过分析冰川融水补给对湖泊面积变化的影响,发现存在冰川融水补给的湖泊面积变化率远大于不存在冰川融水补给的湖泊。由此可见,近年来冰川融水的增加是促进青藏高原内流流域湖泊扩张的主要因素之一。