Changing of the guards: Detrital zircon provenance tracking sedimentological reorganization of a post-Gondwanan rift margin

Understanding the development of sedimentary systems during continental rifting is important for tracking environmental change and lithospheric processes. Conceptual models have been developed for the sourcing, routing and facies architecture of sediments in rift-settings, driven in part by quantitative sediment tracking. Here, we present laser ablation split-stream detrital zircon U/Pb geochronology and Hf-isotopes for post-rift (Cretaceous-Paleogene) clastic sediments from Ocean Drilling Program (ODP) wells and Plio-Pleistocene palaeoshoreline material, from the southern margin of Australia. Provenance results are contextualized through comparison with well-characterized source regions and regional pre- and syn-rift sediment reservoirs to track changes associated with Australia-Antarctica separation during East Gondwana break-up. The provenance character of the post-rift sediments studied are distinct from pre-existing sediment reservoirs and demonstrate termination of previously stable sediment routing systems and a dominance of local basement of the Proterozoic Madura and Coompana provinces (~1.2 Ga and CHUR-like Hf-signatures; Moodini Supersuite) in offshore ODP wells. A composite post-rift Cretaceous?-Eocene sample in the easternmost well expresses characteristic Phanerozoic zircon age signatures associated with source regions in eastern Australia that are interpreted to reflect inversion in the Ceduna Sub-basin to the east. Detrital zircon signatures in Plio-Pleistocene palaeoshoreline sediment are also relatively distinct, indicating derivation from coastal erosion in the Leeuwin Complex (~0.5 and 0.7 Ga subchondritic grains) and Albany–Fraser Orogen (~1.2 Ga subchondritic grains) several hundred, to over a thousand kilometers to the west. Collectively, results highlight the fundamental geological processes associated with rifting that dramatically change the character of sediment provenance via (a) isolation of pre-existing primary and secondary sources of detritus, (b) development of new source regions in basin compartmentalized highs and localized fault scarps, and (c) establishment of marine and coastal currents that redefine clastic sediment transport.     

Progress in NTHMP Hazard Assessment

The Hazard Assessment component of the U.S. National Tsunami Hazard Mitigation Program has completed 22 modeling efforts covering 113 coastal communities with an estimated population of 1.2 million residents that are at risk. Twenty-three evacuation maps have also been completed. Important improvements in organizational structure have been made with the addition of two State geotechnical agency representatives to Steering Group membership, and progress has been made on other improvements suggested by program reviewers.     

旅游环境承载力在待开发景区规划中的应用初探— — 以贵州东风湖为例

景区开发规划设计合理与否事关旅游地的生命周期和可持续发展,而旅游环境承载力是旅游业可持续发展的主要判据之一,在理论上,可以通过某种途径应用旅游环境承载力的理论方法去评价某一开发规划设计的合理性。本文以东风湖为例,探讨了待开发旅游地旅游环境承载力研究的意义,并从旅游环境承载力计算的计量模型,适合喀斯特地域特色的指标体系的建立及指标权重计算等方面,讨论了如何将旅游环境承载力的理论方法应用于待开发旅游地开发规划设计的具体操作方法,并引入了旅游环境承载量和旅游环境承载指数等新概念。      

Importance of volcanic glass alteration to sediment stabilization: offshore Japan

A minor amount (ca 1 wt%) of amorphous silica cement sourced from volcanic glass inhibits consolidation of hemipelagic sediment approaching the Nankai Trough subduction zone throughout the Shikoku Basin. The distribution and nature of the cement were examined via secondary and backscattered electron imaging. The amorphous silica occurs as altered material in contact with volcanic glass, coating grains (including grain contacts) and filling pores. Based on chemical and petrographic evidence, the cement is probably sourced from volcanic glass; this is in contrast to a previous suggestion that this silica cement is sourced dominantly from biogenic silica. Amorphous silica sourced from disseminated volcanic glass shards has the ability to form a thin coating on clay‐dominated sediment throughout the Shikoku Basin. Measured amorphous silica content in hemipelagic sediments suggests that the cementing process is active throughout the Shikoku Basin (at sites separated by >500 km). The cementation process may occur in other locations where sediment containing hydrated disseminated volcanic glass is buried sufficiently for heat to facilitate alteration (i.e. Central America, Cascadia and the Gulf of Alaska).     

The sedimentary expression of oceanic anoxic event 1b in the North Atlantic

The Aptian/Albian oceanic anoxic event 1b contains the record of several perturbations in the global carbon cycle and multiple black shale levels, particularly in the Western Tethys. The local lithological expression of an oceanic anoxic event depends on palaeogeographical and depositional setting as well as on regional palaeoclimate. Marine sediments at a particular location may therefore be more or less organic‐rich (or not at all) and they may consist of different lithologies. In most studies, however, much of the lithological variability associated with oceanic anoxic events is left unaccounted for and, thus, the exact processes leading to the enrichment of organic matter in these marine sediments and their subsequent preservation in the geological record are unknown. This study focuses on the local sedimentary processes behind the deposition of organic‐rich sediments at Deep Sea Drilling Project Site 545 and Ocean Drilling Program Sites 1049 and 1276 in the North Atlantic during oceanic anoxic event 1b. Although specifically dealing with the sediments deposited during this particular event at these localities, it is expected that the same processes were responsible for determining the exact sedimentary products at localities in similar settings, as well as during other similar events in the Mesozoic. Here, it is shown that the deposition of organic‐rich sediments during oceanic anoxic event 1b was a consequence of the enhanced productivity favoured by upwelling and by riverine nutrient input, or aeolian fertilization of the euphotic zone depending on geographical location. Slope instability processes resulted in the transfer of part of these organic‐rich sediments from the shelf to deep sea depocentres as mud‐laden organic‐rich turbidites, especially in the northern North Atlantic. The so‐called ‘black shales’ are much more varied than their name implies. The end product of sedimentation during an oceanic anoxic event at a particular location is commonly the result of several equifinal processes acting on a local scale rather than the direct result of basinal or even global mechanisms.     

科学大洋钻探与天然气水合物

天然气水合物是由水和甲烷等气体水分子组成的冰状物,主要分布于海洋陆坡区和陆地永久冻土带,是21世纪理想的替代能源。科学家已对天然气水合物的物理化学性质、产出条件、分布规律、勘查技术、开采工艺、经济评价及开采可能造成的环境影响等进行了广泛而深入的研究。大洋钻探计划（ODP）是获得深部含天然气水合物和游离气沉积物的唯一途径,已成功实施了164和 204两个以天然气水合物为主要目标的航次,分析研究了含天然气水合物沉积物的原位物理化学特性和地球物理性质,探讨了气体-水-沉积物-水合物间的相互作用机理,为气体储量计算提供了依据,对推动水合物研究作出了重大贡献。综合大洋钻探计划（IODP）的启动,将为人们深刻理解地球历史和地球系统过程（ESP）,特别是认识天然气水合物在地质过程中的作用,提供前所未有的机会。     

服务于大型综合地学科研项目的在线数据支撑平台

大型综合地学科研项目产生的数据既是项目研究成果的组成部分, 又是科技创新的重要基础。面向复杂地学信息资源汇交、管理和共享的需要, 有必要建立针对项目自身运行管理和数据产出特色的在线数据支撑平台。本文以973项目“白垩纪地球表层系统重大地质事件与温室气候变化”为例, 研究并应用 Web Services技术与地理信息技术建立服务于特定项目的数据支撑平台。论文阐述了项目数据的分类方法和数据汇交机制, 并基于“数据-功能-用户”视图理念, 设计实现了提供数据汇交、管理和共享功能的数据服务门户以及对WebGIS的集成。应用结果表明: 在线数据支撑平台对发挥多源、复杂、高成本的地学科研数据共享利用价值具有良好的支撑作用; 同时, 具有一定通用性的平台框架对同类项目数据成果的归档管理以及验收汇报演示具有示范意义。     

赣江下游污染负荷与水质响应关系模型

为了研究赣江下游入河污染物对河流水质的影响,建立了基于WASP（Water quality Analysis Simulation Program）模型富营养化原理和ELADI（Eulerian-Lagrangian Alternating Direction Implicit Method）有限差分方法的正交曲线平面二维水环境模型WESC2D（Two-Dimensional Water Environment Simulation Code）。模型采用基于双线性插值及亚网格技术的欧拉-拉格朗日方法求解对流项,在简单的浓度峰输运和赣江下游溶解氧变化过程算例检验的基础上,计算与分析了赣江下游入河排污口氨氮污染负荷与水质之间的动态响应关系。模拟与分析结果表明,WESC2D模型的计算结果与解析解吻合良好,有效地减少了欧拉-拉格朗日方法的数值耗散,并为赣江下游污染负荷与水质响应关系计算提供了重要工具。     

剥蚀型汇聚板块边缘大地震成因机理研究:来自国际综合大洋钻探344航次的报告

旨在探究剥蚀型汇聚板块边缘大地震成因机理的国际综合大洋钻探(IODP)344航次于2012年10月23日至12月11日在中美洲地震频发的哥斯达黎加西部海域实施钻探。介绍了钻探区域的大地构造特征、该航次的主要科学目标、执行情况、所取得的初步成果以及对航次后研究工作的展望等。航次后更多深入细致的研究工作正在进行中,所取得的研究成果将集中在2014年南京召开的航次后学术研讨会上汇报、交流、集成、总结,从而提升对剥蚀型汇聚板块边缘大地震起源机理的认识。     

发震带试验(SEIZE)

对发震带试验计划(SEIZE)以及南海（Nankai）海槽的发震带钻探计划（NanTroSEIZE）进行了综述。SEIZE作为大陆边缘计划(MARGINS)的重要研究内容和综合大洋钻探计划（IODP）的优先研究领域,重点对世界主要俯冲发震带进行研究。SEIZE的主要研究内容包括：①凸凹体的物理性质;②在地震周期里,应力、应变和孔隙流体成分随时间的变化;③在俯冲逆冲断层上,发震带上界和下界的确定;④引起海啸的发震带的特征;⑤大型逆冲带地震在物质转换过程中所起的作用。NanTroSEIZE将成为IODP第一个基于立管钻探的计划,也是科学大洋钻探历史上第一个分期实施的复合钻探计划;钻入发震带的复合钻探计划将最终验证关于发震带的各种假说。 