Structural and depositional controls on Plio‐Pleistocene submarine channel geometry (Taranaki Basin,New Zealand)     

Nathalia H. Mattos  Tiago M. Alves  Aisling Scully 《Basin Research》2019,31(1):136-154

High‐quality 3D seismic data are used to investigate the effect of the Parihaka Fault on the geometry of submarine channels in Northern Graben of the Taranaki Basin, New Zealand. The Parihaka Fault comprises of four segments (S1–S4) with variable displacements. As part of the Plio‐Pleistocene Giant Foresets Formation, the older Channel Complex Systems 1 and 2 reveal a two‐stage evolution: (a) a syn‐tectonic depositional stage with channels incising the slope during early fault growth (ca. 4.5 Ma) and (b) a stage of sediment bypass (ca. 3 Ma) leading to the infill of hanging‐wall depocentres. The Channel Complex System 3 is syn‐tectonic relative to segment S3 and was formed at ca. 2.5 Ma. We show that the successive generation of new fault segments towards the north controlled the formation of depocentres in the study area. This occurred in association to rotation and uplift of the footwall block of the Parihaka Fault and subsidence of its hanging‐wall block, with fault activity controlling the orientation of channel systems. As a result, we observe three drainage types in the study area: oblique, transverse and parallel to the Parihaka Fault. This work is important as it shows that relay zones separating the Parihaka Fault segments had limited influence on the geometry and location of channel systems. Submarine channels were diverted from their original courses close to the Parihaka Fault and flowed transversally to fault segments instead of running through relay ramps, contrasting to what is often recorded in the literature. A plausible explanation for such a discrepancy relates to rapid progradation of the Giant Foresets Formation during the Plio‐Pleistocene, with channel complexes becoming less confined, favouring footwall incision and basinward deposition of submarine fans.  相似文献   

闽江口外海域晚第四纪地震层序和古河道演变     

刘阿成  唐建忠  吴巍  张杰 《海洋与湖沼》2019,50(1):61-73

为了查明闽江口外海域晚第四纪地震地层特征,进行了高分辨率浅地震剖面调查,穿透的沉积物厚度最大约90m,划分为6个地震层序,自上向下为U1—U6。U1为全新世(海洋同位素阶段(marine isotope stage,MIS) 1期)海相沉积单元,U3为MIS 3期的滨浅海—河口相,U5为MIS 5期的滨浅海与河流交互相,在MIS 5.2和5.4亚期海平面下降超过15m,发育了河流沉积;U2和U4分别为MIS 2和MIS 4期的河流充填相,而U6为MIS 6期的陆相沉积单元。根据地震层序关系研究了埋藏古河道的断面和分布特征、发育年代、演变及原因等。在全新世初期(11.5ka BP)之前,古闽江呈SE向经研究区南部和海坛岛东面流入东海(台湾海峡北口),随着研究区上游地势不断淤高,在11.5ka BP之后发育了NE向经北部向海到达西引岛附近的古河流,至约9.2ka BP海平面上升到约-30m高度时,全部河流消失于海面之下,闽江最后一次退出研究区。在闽江口东面,埋藏古丘陵的中南部高于现海面下50m(-50m),受其阻挡未能发育向东直接入海的闽江古河道。本文的研究结果提供了研究区自MIS 6末期以来古河流发育和演变等方面的新认识和证据。  相似文献   

A simple approach to estimating freshwater discharge in branched estuarine systems          下载免费PDF全文

Duc Hoang Nguyen  Duc Anh Nguyen 《水文研究》2018,32(17):2765-2778

In tidal estuaries, quantifying freshwater discharge is still a difficult problem that has not yet been overcome due to the inherent difficulty in measuring and analysing the tidal discharge, especially during periods of low river flow. Because observations are often made in the stations further upstream, where the ratio of river to tidal discharge is large, it remains difficult to determine the discharge rate in the saline region. Freshwater discharge estimation is even more difficult in a branched estuary system having multiple diversion channels that connect with each other at a junction. To date, several methods have been developed for estimating freshwater discharge in estuaries. The most widely used are analytical and conceptual models that employ salinity as the principal trace and numerical simulations. However, these methods are very time consuming and costly as they require large sets of observations before the computations can take place. This paper presents a simple approach to investigating the discharge distribution over branched channels by considering the energy loss due to friction. We develop an analytical model that can obtain the discharge rate quantitatively at a junction where the main flow bifurcates into two branches. The model uses the bed roughness, tidal water level, and cross‐sectional profile under tidally averaged conditions as input data. Two selected estuarine systems in the Hiroshima delta in Japan and the Mekong delta in Vietnam have been investigated. Computations of the newly developed model show good agreement with earlier published results computed by sophisticated analytical and numerical models.  相似文献   

Evidence for subaqueously resedimented sulphate evaporites on Mars     

Forese Carlo Wezel  Davide Baioni 《Planetary and Space Science》2010,58(11):1500-1505

This article documents the clastic nature of sulphate evaporite beds in the Tithonium Chasma located in the Valles Marineris region of Mars. These beds form a stratified succession characterised by very thick interbedded channel-fill breccia bodies. We infer that the bouldery channel-fills were deposited by voluminous mass-flow processes occurring in a relatively deep subaqueous environment. The redeposition of the coarse-grained evaporite would have responded to phases of high denudation rates in rapidly uplifting hinterlands. Tectonic activity also caused the diapiric uprise and exhumation of evaporite diapirs within the Valles Marineris chasmata, where the apparently young and well development karstic landforms probably formed during the late Amazonian age. These new data strongly suggest the deposition of both primary and resedimented evaporites in a marginal basin area, which effectively restricted ocean access through the proposed “proto-Valles Marineris Strait”. The associated ocean may be the “Ocean Borealis” of Late Noachian-Early Hesperian age.  相似文献   

古居延绿洲汉代至西夏渠系影像特征及绿洲环境变迁          下载免费PDF全文

蓝利  穆桂金  齐乌云  相马秀广  村田泰辅 《第四纪研究》2009,29(2):241-247

利用较高分辨率的遥感影像确定出古居延绿洲渠系分布和引水口的位置以及古渠道线路的走向,发现古居延绿洲主要分布在现代绿洲的东侧,至少有6处引水口分布于距雅布赖、东城圈和马圈城一线西侧的水道上。渠系由西向东进入各垦区,各引水口随水道西迁向西延伸。渠系与遗址、古耕地和红柳包间的联系以及¹⁴C\}测年数据表明：  多数渠系始建于汉代,以后长期延用,盛于西夏,弃于元末明初;   古居延绿洲早期荒漠化始于1300aB.P.;   天然水系向西迁移最终导致了古居延绿洲的废弃和完全荒漠化  相似文献   

The Brampton kame belt and Pennine escarpment meltwater channel system (Cumbria, UK): Morphology, sedimentology and formation     

Stephen J. Livingstone  David J.A. Evans  Colm Ó Cofaigh  Jonathan Hopkins 《Proceedings of the Geologists' Association. Geologists' Association》2010,121(4):423-443

The Brampton kame belt represents one of the largest glaciofluvial complexes within the UK. It is composed of an array of landform-sediment assemblages, associated with a suite of meltwater channels and situated within a palimpsest landscape of glacial features in the heart of one of the most dynamic parts of the British-Irish Ice Sheet. Glacial geomorphological mapping and sedimentological analysis have allowed a detailed reconstruction of both the morphological features and the temporal evolution of the Brampton kame belt, with processes informed by analogues from modern ice margins. The kame belt demonstrates the development of a complex glacier karst typified by the evolution of subglacial meltwater tunnels into an englacial and supraglacial meltwater system dominated by ice-walled lakes and migrating ice-contact drainage networks. Topographic inversion led to the extensive reworking of sediments, with vertical collapse and debris flows causing partial disintegration of the morphology. The resultant landform comprises a series of kettle holes, discontinuous ridges and flat-topped hills. The Pennine escarpment meltwater network, which fed the Brampton kame belt, is composed of an anastomosing subglacial channel system and flights of lateral channels. The Brampton kame belt is envisaged to have formed during the stagnation of ice in the lee of the Pennines as ice retreated westwards into the Solway Lowlands. The formation of the Brampton kame belt also has particular conceptual resonance in terms of constraining the nature of kame genesis, whereby an evolving glacier karst is a key mechanism in the spatial and temporal development of ice-contact sediment-landform associations.  相似文献   

Hydrologic response to valley‐scale structure in alpine headwaters          下载免费PDF全文

Anne A. Weekes  Christian E. Torgersen  David R. Montgomery  Andrea Woodward  Susan M. Bolton 《水文研究》2015,29(3):356-372

Few systematic studies of valley‐scale geomorphic drivers of streamflow regimes in complex alpine headwaters have compared response between catchments. As a result, little guidance is available for regional‐scale hydrological research and monitoring efforts that include assessments of ecosystem function. Physical parameters such as slope, elevation range, drainage area and bedrock geology are often used to stratify differences in streamflow response between sampling sites within an ecoregion. However, these metrics do not take into account geomorphic controls on streamflow specific to glaciated mountain headwaters. The coarse‐grained nature of depositional features in alpine catchments suggests that these landforms have little water storage capacity because hillslope runoff moves rapidly just beneath the rock mantle before emerging in fluvial networks. However, recent studies show that a range of depositional features, including talus slopes, protalus ramparts and ‘rock‐ice’ features may have more storage capacity than previously thought. To better evaluate potential differences in streamflow response among basins with extensive coarse depositional features and those without, we examined the relationships between streamflow discharge, stable isotopes, water temperature and the amplitude of the diurnal signal at five basin outlets. We also quantified the percentages of colluvial channel length measured along the stepped longitudinal profile. Colluvial channels, characterized by the presence of surficial, coarse‐grained depositional features, presented sediment‐rich, transport‐limited morphologies that appeared to have a cumulative effect on the timing and volume of flow downstream. Measurements taken from colluvial channels flowing through depositional landforms showed median recession constants (K_r) of 0.9–0.95, δ¹⁸O values of ≥?14.5 and summer diurnal amplitudes ≤0.8 as compared with more typical surface water recession constant values of 0.7, δ¹⁸O ≤ ?13.5 and diurnal amplitudes >2.0. Our results demonstrated strong associations between the percentage of colluvial channel length within a catchment and moderated streamflow regimes, water temperatures, diurnal signals and depleted δ¹⁸O related to groundwater influx. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Currents in a small channel on a sandy tidal flat   总被引：1，自引：0，他引：1  

Steve Elgar  Britt Raubenheimer 《Continental Shelf Research》2011,31(1):9-14

Channels affect drainage and bed stresses on tidal flats. Here, near-bottom currents observed on a sandy tidal flat are compared with those observed 35 m away inside a shallow (≈0.3 m deep) channel. For water depths between 0.5 and 2.5 m (when both current meters are submerged), current speeds 0.13 m above the bed on the flat are about 30% greater than those observed 0.13 m above the bed in the channel, and are approximately equal to those observed 0.58 m above the channel bed (0.26 m above the flat elevation). Flow directions on the flat are similar to those in the channel. For flows directed across the channel axis, the ratio of speeds increases from about 1.3 to about 2.2 with increasing water depth. The corresponding ratio of the vertical velocity variances (a proxy for turbulence) decreases from about 1.5 to about 0.2, suggesting that the turbulence near the bed of the channel is greater than that near the bed of the flat for water depths greater than about 1.0 m. Drag coefficients estimated with the vertical velocity variance are approximately 70% larger in the channel than over the visually smoother flat, consistent with prior studies suggesting that channels may increase tidal-flat roughness. For flows directed along the channel axis (in the cross-flat direction), the ratio of speeds (1.2) is similar to the ratio predicted by a cross-flat momentum (along-channel) balance.  相似文献   

论油气运移的"高速公路"及源外找油思想   总被引：7，自引：0，他引：7  

潘树新  卫平生  袁剑英  王天奇  赵志魁  赵占银  王立贤  雷明 《沉积学报》2011,29(3):599-604

源控论认为,有效烃源岩的展布范围或者生油凹陷的展布范围控制了油气的平面分布,油气主要分布在距离主力生油洼陷20～30 km的范围内.松辽盆地西部斜坡大部分地区超出有效烃源岩的展布范围,但在西坡发现了富拉尔基油田、平洋油气田、图牧吉油砂矿和套保油田等油区.笔者在松南西斜坡发现一条大型"人字"形沟谷体系,该沟谷体系对白城水...  相似文献   

Key controls on submarine channel development in structurally active settings     

Ian R. Clark  Joseph A. Cartwright 《Marine and Petroleum Geology》2011,28(7):1333-1349

Submarine channel-levee systems commonly develop in structurally active deepwater settings. Despite their widespread development in such settings, only recently have researchers begun to address the response of channel-levee system evolution to deformation. Key factors which govern channel evolution and morphological development are relative rates of deformation and channel deposition and erosion, and also the number and scale of deformational structures, relative to the scale of the submarine channel. Submarine channel-structure interactions can be split into four end-members: deflection, blocking, diversion and confinement. Where deformation is coeval with channel development, an increase in the relative rate of uplift versus deposition and erosion causes a transition from channel deflection to blocking. Diversion and confinement are linked by the number, scale and orientation of structures relative to the channel flow path. Increasing the number of structures and their scale typically results in channel confinement. Underlying all of these individual controls is the distribution of local accommodation, which is determined by specific structural style. This distribution of accommodation over relatively small (<10 km) length scales strongly affects local channel development in order to attain the equilibrium profile. Knowledge of these controls on submarine channel development can increase our understanding of how these deepwater sedimentary systems evolve and distribute sediment across deforming submarine slopes. Understanding the factors governing spatial variations in channel morphology may also be applied when exploring for hydrocarbon reservoirs in structurally active deepwater settings.  相似文献