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首页> 外文期刊>Journal of Paleolimnology >Early postglacial history of the southeastern Assiniboine Delta, glacial Lake Agassiz basin
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Early postglacial history of the southeastern Assiniboine Delta, glacial Lake Agassiz basin

机译：东南阿西尼博因三角洲的早期冰期历史，冰川阿加西兹湖盆地

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摘要

New stratigraphic evidence from the Rossendale area, Manitoba, Canada, provides insight into the early postglacial evolution of the southeastern Assiniboine Delta. In this region, much of the upper 13+ m of sediment accumulation is characterized by multiple cycles of sandy rhythmites interbedded with massive to laminated silt. These sediments were deposited rapidly by traction or turbidity currents and record the construction of the Assiniboine fan-delta during the deep-water Lockhart Phase of glacial Lake Agassiz (>10.8 14C ka BP). Shortly before ～10 14C ka BP, fluvial incision into deltaic deposits occurred locally at the Rossendale Gully site in response to the regression of glacial Lake Agassiz during the Moorhead Phase. Plant macrofossils deposited in the gully by 10 14C ka BP provide the first information on early postglacial plant colonization of the distal Assiniboine delta. These data suggest initial establishment of Scorpidium scorpioides, Potamogeton spp., Scirpus spp., and other wetland plants, followed by colonization of uplands by a Picea-Populus assemblage. Importantly, because the gully is located in a protected depression behind the Campbell beach, evidence of water table rise from aquatic macrophytes suggests that glacial Lake Agassiz transgressed to the Campbell level during the early Emerson Phase (～10 14C ka BP). Furthermore, no evidence exists for a post-Lockhart rise in Lake Agassiz above the Upper Campbell beach. If Agassiz stood at the Campbell level during the early Emerson Phase, then drainage through the southern outlet may have been possible at this time. This scenario, if true, may suggest that the northwestern outlet was temporarily closed by a glacial advance shortly before 10 14C ka BP.
机译：来自加拿大马尼托巴省罗森代尔地区的新地层证据为东南阿西尼博因三角洲的早期冰期演化提供了见识。在该地区，上部13+ m的沉积物堆积的大部分特征是沙质节奏的多个循环，这些沙质节奏与块状至层状粉砂互层。这些沉积物通过牵引流或浑浊流快速沉积，并记录了阿加西兹湖（> 10.8 14 C ka BP）深水洛克哈特相期间Assiniboine扇三角洲的构造。大约在10 14 C ka BP之前，由于Moorhead时期冰川冰川Agassiz的消退，在Rossendale Gully部位局部切入三角洲沉积物。通过10 14 C ka BP沉积在沟渠中的植物大化石提供了有关冰期后阿西尼博因三角洲早期植物定殖的第一个信息。这些数据表明，最初建立了蝎子天蝎，波达莫顿（Potamogeton spp。），Scirpus spp。和其他湿地植物，然后通过云杉-杨（Picaa-Populus）组合对高地进行定植。重要的是，由于该沟位于坎贝尔海滩后面的受保护的洼地中，地下水位从水生植物上抬升的证据表明，冰川艾格西斯湖在艾默生早期（〜10 14 C ka BP ）。此外，没有证据表明上坎贝尔海滩上方的阿加西兹湖在洛克哈特峰之后发生上涨。如果在艾默生阶段早期，阿加西（Agassiz）站在坎贝尔（Campbell）水平，那么此时可能已经可以通过南部出口排水了。如果是这样的话，则可能表明西北出口在10 14 C ka BP之前不久就因冰川运动而暂时关闭。

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