Sediment provenance in a tropical fluvial and marine context by magnetic ‘fingerprinting’ of transportable sand fractions
Sediment provenance in a tropical fluvial and marine context by magnetic ‘fingerprinting’ of transportable sand fractions
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DOI：
10.1111/j.1365-3091.2008.00999.x
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发表时间：
2009-04
期刊：
影响因子：
3.5
通讯作者：
B. A. Maher;S. J. Watkins;G. Brunskill;Jan Alexander;C. Fielding
中科院分区：
文献类型：
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作者：
B. A. Maher;S. J. Watkins;G. Brunskill;Jan Alexander;C. Fielding
来自澳大利亚东北部河流的沉积物的来源和通量一直是备受关注和研究的主题，Burdekin和Fitzroy河的大流域被认为是目前的关键来源。在这里，新开发的磁“指纹”方法识别沉积物的来源，陆上和海上，并与个别大洪水事件的效用，进行了调查。在Burdekin集水区，沉积物从不同的子集水区动员的强烈，局部降雨事件产生的径流。对伯德金河子流域内以及伯德金河沉积物的河口和内陆架沉积中心的未经处理和酸处理的河道沉积物样品进行了磁性测量。酸处理去除了所有离散的磁性颗粒和涂层，并留下磁性夹杂物（在主体硅酸盐颗粒内受到保护）作为样品的测量磁性特征的基础。酸处理样品的磁性显示了统计学上不同的沉积物来源分组。来自Burdekin河上游的砂样与来自Burdekin河支流（如Hann Creek、Fanning River）以及附近沿海河流（包括豪顿河）的砂样在磁性上存在差异。与1998年和1999年的洪水相比，2000年Burdekin洪水事件的悬浮沙样品似乎有不同的来源。陆地酸处理砂组分与近海断面相同酸处理砂组分的比较表明，Upstart湾和Bowling格林湾的表层沉积物来源不同。其中一些来源尚未确定，但可能代表未经采样的，较低排放的西南Burdekin子流域，和/或沿着海岸从南部漂移的沙子，甚至可能来自菲茨罗伊河，在飓风抽水的千年时间尺度。磁性包裹体方法排除了可能由水力分选和/或沉积后磁性成岩作用或自生作用引起的沉积物来源的任何混淆或混淆。
The sources and fluxes of sediment to the Great Barrier Reef lagoon from north‐eastern Australian rivers have been the subject of much concern and study, with the large catchments of the Burdekin and Fitzroy Rivers thought to be the key sources at present. Here, the utility of newly developed magnetic ‘fingerprinting’ methods for identifying sediment provenance, both onshore and offshore, and in association with individual large flood events, is investigated. Within the Burdekin catchment, sediments are mobilized from different subcatchments by runoff generated by intense, localized rainfall events. Magnetic measurements were made on untreated and acid‐treated samples of river channel sediments within the Burdekin River subcatchments and from the estuarine and inner shelf depocentres of Burdekin River sediments. The acid treatment removes all discrete magnetic particles and coatings, and leaves magnetic inclusions (protected within host silicate grains) as the basis of the measured magnetic signature of a sample. The magnetic properties of the acid‐treated samples display statistically distinct sediment provenance groupings. Sand samples from the Upper Burdekin River appear magnetically distinct from samples from tributaries of the Burdekin (e.g. Hann Creek, Fanning River) and also from nearby coastal rivers, including the Haughton. Suspended sand samples from a Burdekin flood event in 2000 appear to have a different source compared with those from floods in 1998 and 1999. Comparisons of the terrestrial, acid‐treated sand fractions with the same, acid‐treated, sand‐size fractions from transects taken offshore suggest that the surface sediments in Upstart Bay and Bowling Green Bay have different sources. Some of these sources are as yet unidentified but may represent the unsampled, lower‐discharge south‐western Burdekin subcatchments, and/or along‐shore drift of sand from the south, perhaps even from the Fitzroy River, over millennial timescales of cyclone pumping. The magnetic inclusion method precludes any obfuscation or confounding of sediment source, which might arise from hydraulic sorting and/or post‐depositional magnetic diagenesis or authigenesis.