Otway Continental Margin Transect: Crustal architecture from wide‐angle seismic profiling across Australia's southern margin

The Otway Basin in southeastern Australia formed on a triangular‐shaped area of extended continental lithosphere during two extensional episodes in Cretaceous to Miocene times. The extent of the offshore continental margin is highlighted by Seasat/Geosat satellite altimeter data. The crustal architecture and structural features across this southeast Australian margin have been interpreted from offshore‐onshore wide‐angle seismic profiling data along the Otway Continental Margin Transect extending from the onshore Lake Condah High, through the town of Portland, to the deep Southern Ocean. Along the Otway Continental Margin Transect, the onshore half‐graben geometry of Early Cretaceous deposition gives way offshore to a 5 km‐thick slope basin (P‐wave velocity 2.2–4.6 km/s) to at least 60 km from the shoreline. At 120 km from the nearest shore in a water depth of 4220 m, sonobuoy data indicate a 4–5 km sedimentary sequence overlying a 7 km thick basement above the Moho at 15 km depth. Major fault zones affect the thickness of basin sequences in the onshore area (Tartwaup Fault Zone and its southeast continuation) and at the seaward edge of the Mussel Platform (Mussel Fault). Upper crustal basement is interpreted to be attenuated and thinned Palaeozoic rocks of the Delamerian and Lachlan Orogens (intruded with Jurassic volcanics) that thin from 16 km onshore to about 3.5 km at 120 km from the nearest shore. Basement rocks comprise a 3 km section with velocity 5.5–5.7 km/s overlying a deeper basement unit with velocity 6.15–6.35 km/s. The Moho shallows from a depth of 30 km onshore to 15 km depth at 120 km from the nearest shore, and then to about 12 km in the deep ocean at the limits of the transect (water depth 5200 m). The continent‐ocean boundary is interpreted to be at a prominent topographic inflection point 170 km from shore at the bottom of the continental slope in 4800 m of water. P‐wave velocities in the lower crust are 6.4–6.8 km/s, overlying a thin transition zone to an upper mantle velocity of 8.05 km/s beneath the Moho. Outstandingly clear Moho reflections seen in deep‐marine profiling data at about 10.3 s two‐way time under the slope basin and continent‐ocean boundary place further strong controls on crustal thickness. There is no evidence of massive high velocity (>7 km/s) intrusives/underplate material in the lower crust nor any synrift or early post‐rift subaerial volcanics, indicating that the Otway continental margin can be considered a non‐volcanic margin, similar in many respects to some parts of the Atlantic Ocean margins e.g. the Nova Scotia ‐ Newfoundland margin off Canada and the Galicia Bank off the Iberian Peninsula. Using this analogue, the prominent gravity feature trending northwest‐southeast at the continent‐ocean boundary may indicate the presence of highly serpentinised mantle material beneath a thin crust, but this has yet to be tested by detailed work.     

http://www.sciencedirect.com/science/article/pii/S1674987112001223

The Paleogene succession of the Himalayan foreland basin is immensely important as it preserves evidence of India-Asia collision and related records of the Himalayan orogenesis. In this paper, the depositional regime of the Paleogene succession of the Himalayan foreland basin and variations in composition of the hinterland at different stages of the basin developments are presented. The Paleogene succession of the western Himalayan foreland basin developed in two stages, i.e. syn-collisional stage and post-collisional stage. At the onset, chert breccia containing fragments derived from the hanging walls of faults and reworked bauxite developed as a result of erosion of the forebulge. The overlying early Eocene succession possibly deposited in a coastal system, where carbonates represent barriers and shales represent lagoons. Up-section, the middle Eocene marl beds likely deposited on a tidal flat. The late Eocene/Oligocene basal Murree beds, containing tidal bundles, indicate that a mixed or semi-diurnal tidal system deposited the sediments and the sedimentation took place in a tide-dominated estuary. In the higher-up, the succession likely deposited in a river-dominated estuary or in meandering rivers. In the beginning of the basin evolution, the sediments were derived from the Precambrian basement or from the metasediments/volcanic rocks possessing terrains of the south. The early and middle Eocene (54.7–41.3 Ma) succession of the embryonic foreland possibly developed from the sediments derived from the Trans-Himalayan schists and phyllites and Indus ophiolite of the north during syn-collisional stage. The detrital minerals especially the lithic fragments and the heavy minerals suggest the provenance for the late Eocene/Oligocene sequences to be from the recycled orogenic belt of the Higher Himalaya, Tethyan Himalaya and the Indus-suture zone from the north during post-collisional stage. This is also supported by the paleocurrent measurements those suggest main flows directed towards southeast, south and east with minor variations. This implies that the river system stabilized later than 41 Ma and the Higher Himalaya attained sufficient height around this time. The chemical composition of the sandstones and mudstones occurring in the early foreland basin sequences are intermediate between the active and passive continental margins and/or same as the passive continental margins. The sedimentary succession of this basin has sustained a temperature of about 200 °C and undergone a burial depth of about 6 km.     

Modern halite sedimentation processes and depositional environments,Hutt Lagoon,Western Australia

Abstract

Contemporary layered halite in the Hutt Lagoon, Western Australia, forms distinct precipitational and clastic fades, which are ascribed to seasonal ponding and playa development in the lagoon respectively. Field and laboratory documentation of the halite types and monitoring of surface water chemistry for several annual hydrologic cycles indicate that following evaporative concentration of ponded seawater halite layers, characterized by zoned and clear halite crystal varieties, are developed. During early stages of annual playa development, vadose solution and precipitation appear to be most active within and above the capillary fringe zone, causing diagenetic modification of the halite textures, fabrics and structures. Ultimately, clastic halite facies are produced by wind reworking of the earlier deposits, in response to progressive evaporative drawdown of the brine level in the main depression area of the lagoon.

The co-existence of the halite precipitates and clastites is related to a dynamic equilibrium in the water budget of the Hutt Lagoon. This equilibrium is best exemplified by limitation of brine level fluctuations to a narrow repetitive zone. Identification of similar early diagenetic features, such as vadose solution, precipitation, overgrowth, replacement and mechanical reworking of surface halite sediments, in ancient evaporite deposits may aid in a better understanding of the role of brine level fluctuation on genesis and diagenesis of subaqueous/subaerial halite.     

建筑设计与造价控制浅析

建设项目投资的控制应贯穿于立项到竣工验收整个项目的各个阶段,施工前的决策和设计尤为重要。基于这种情况,本文简述了设计阶段造价控制的必要性,论述了在建筑设计的各阶段造价控制的措施,可有效地提高经济效益。     

回应气候的山地城镇与建筑设计

回应地方气候与地理是建筑融于自然的主要方式,建筑因此获得存在于那个特定地点的充分理由以及地方性.应用山地设计和生态建筑设计理论,采取图解分析和综合演绎的方法,从山地建筑选址、布局、体形选择、通风、日照和景观等方面,探索回应气候的城市与建筑设计准则与策略,提出结合气候的山地城镇设计具体策略和手法,包括建筑选址、地域景观、通风防风、空间应变和节能设计策略等,为节能和生态建筑设计的理论与实践研究奠定基础.     

利用砂体叠加部署聪明井提高勘探开发效果

通过相应属性的叠加可提高油气勘探开发的分析效果,减少投资风险。在勘探中采用精细沉积微相分析技术,通过对勘探目标区各小层沉积微相分析,编制各层的砂体分布图,提取各层砂体中主力砂体,编制小层主力砂体的叠加图;通过对叠加图分析,确定优势储层分布区域,进行成藏风险评价,提高了布井效果。而在油田开发调整中,通过对各单层进行精细沉积微相分析,确定其平面分布特征,结合各成因砂体的控制和动用程度,确定成因砂体内的剩余油分布情况,进而确定剩余油富集砂体,并制作剩余油富集砂体叠加图,据此以成因砂体为单元部署高效聪明调整井,提高了油田的采收率和开发效果。     

数据中心集成开发技术: 新一代GIS架构技术与开发模式

解决分布式异构多源空间数据共享、不同厂家的功能共享和合作开发是当前GIS开发和应用领域的难题.提出了数据中心集成开发模型框架, 并基于该框架提出了新一代GIS架构技术和开发模式, 介绍了数据中心的核心技术——数据仓库技术、功能仓库技术、搭建与配置技术等, 同时给出了国土数据中心的应用实例, 为基于数据中心大型信息化系统解决方案的实现提供了一种新的模型.      

文物建筑保护与旅游开发协调发展及其对策

以广州市为例从文物建筑的基本特征、文物建筑保护面临的问题、面对庞大的都市旅游市场的需求压力出发,提出基于文物保护法规前提之下符合两者不同利益需求的合作协调发展对策.     

复合土钉支护技术在基坑支护工程中的应用——以广州地区为例

复合土钉支护技术是在土钉支护结构中复合其他土体加固技术的综合支护技术 ,是近年来在城市建筑深基坑支护工程中发展起来的一种具有中国特色的土钉支护技术。通过工程实例讨论了广州地区复合土钉支护工程中使用的基本支护结构、施工技术和工艺流程 ,并在此基础上提出了建议和意见     

应用SVM方法进行沉积微相识别

作者针对目前沉积微相中的特征提取问题,提出了应用ＳＶＭ（支持向量机）方法进行沉积微相识别的方案。该方法不是象传统方法那样首先试图将原输入空间降维（即特征选择变换）,而是设法将输入空间升维,以求在高维空间中问题变得线性可分（或接近线性可分）。因为升维后只是改变了内积运算,并没有使算法复杂性随着维数的增加而增加,因此这种方法才是可行的。所以。利用该方法更能胜任实际情况。实际处理表明该方法在小样本情况下