The character and age structure of valley fills in upper Wolumla Creek catchment, south coast, New South Wales, Australia
The character and age structure of valley fills in upper Wolumla Creek catchment, south coast, New South Wales, Australia
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澳大利亚新南威尔士州南海岸沃伦拉溪上游流域的山谷特征和年龄结构
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发表时间：
1998
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通讯作者：
G. Brierley
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作者：
K. Fryirs;G. Brierley
在澳大利亚新南威尔士州南海岸的沃鲁姆拉河上游的悬崖底部，广泛的山谷填充物是由“切割和填充”过程相结合形成的。山谷填充物由一系列交替的水平层状砂和泥单元组成，反映了Bega风化花岗岩中碎屑的再加工。砂单元沉积为冲积平原表面上的砂层或扇叶，或在不连续冲沟下游完整的山谷填充表面上形成的沙丘中。或者，泥沙从推移质沉积，并在河道填料内形成沙坝或部分谷底。富含有机质的泥质单元是从沼泽中的悬浮物或在突出物远缘的渗流带中沉积的。在悬崖的5 km范围内，山谷沉积物从沙丘中的砂席和扇叶沉积向下游渐变，到沼泽和渗流带中的泥浆沉积。
放射性碳年代测定表明，实际上，沃鲁姆拉河上游的整个山谷填充物都是在6000年前被挖掘出来的。在山谷边缘有明显的残留阶地。该山谷随后填充了6000年BP和1000年BP生产山谷填充约12米深，但不超过300米宽。在距今1000年左右，以小于目前切割阶段的规模重新切割到山谷填充物中，随后通道重新填充。1865年的部分计划将研究区域称为“Wolumla Big Flat”，并显示大面积的沼泽地形，表明此时山谷填充已经重新建立。在欧洲人定居的几十年内，山谷填充物再次被切割。上沃鲁姆拉河现在有一条深10米、宽100米的河道，排水面积不到20平方公里。© 1998 John Wiley & Sons，Ltd。
Extensive valley fills at the base of the escarpment in upper Wolumla Creek, on the south coast of New South Wales, Australia, have formed from a combination of ‘cut and fill’ processes. The valley fills comprise series of alternating, horizontally bedded sand and mud units, reflecting reworking of detritus from deeply weathered granites of the Bega Batholith. Sand units are deposited as sand sheets or splays on floodplain surfaces or in floodouts that form atop intact valley fill surfaces downstream of discontinuous gullies. Alternatively, sands are deposited from bedload and form bars or part of the valley floor within channel fills. Organic-rich mud units are deposited from suspension in swamps or in seepage zones at the distal margin of floodouts. Within 5 km of the escarpment, valley deposits grade downstream from sand sheet and splay deposition in floodouts, to mud deposition in swamp and seepage zones.
Radiocarbon dates indicate that virtually the entire valley fill of upper Wolumla Creek was excavated prior to 6000 years BP. Remnant terraces are evident at valley margins. The valley subsequently filled between 6000 years BP and 1000 years BP producing valley fills around 12 m deep, but no greater than 300 m wide. Reincision into the valley fill, on a scale smaller than the present incision phase, is indicated at around 1000 years BP, following which the channel refilled. Portion plans dated from 1865 refer to the study area as ‘Wolumla Big Flat’, and show large areas of swampy terrain, suggesting that the valley fill had re-established by this time. Within a few decades of European settlement the valley fill incised once more. Upper Wolumla Creek now has a channel over 10 m deep and 100 m wide in places, draining a catchment area of less than 20 km2. © 1998 John Wiley & Sons, Ltd.