Sedimentation at the margins of a late Pleistocene ice‐lobe terminating in shallow marine environments, Dundalk Bay, eastern Ireland
Sedimentation at the margins of a late Pleistocene ice‐lobe terminating in shallow marine environments, Dundalk Bay, eastern Ireland
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爱尔兰东部邓多克湾晚更新世冰瓣边缘的沉积作用，终止于浅海环境
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发表时间：
1987
期刊：
影响因子：
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通讯作者：
P. Hanvey
中科院分区：
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作者：
A. Mccabe;G. F. Dardis;P. Hanvey
爱尔兰东部Dundalk湾周围的晚更新世冰碛序列沉积在一个接地的冰瓣边缘的各种浅水，冰海环境中。沉积物基本上是近冰三角洲扇和扇体序列，并分为两个岩相组合。岩相组合1是一系列冰碛岸，形成于受爱尔兰海影响的水体中冰瓣的南缘。冰碛岸主要由浑浊羽流沉积的混合泥和冰筏沉积组成，少量出现浊积岩、交错层砾石（水下沉积物）和大块巨砾砾石（高密度泥石流）。岩相组合2沉积在冰瓣东北缘的一个狭窄的海臂中。沉积物主要由一系列聚结的、冰近端的吉尔伯特型扇三角洲组成，这些扇三角洲在远端与板状和透镜状水下沉积物互层。后者主要是冰筏杂岩、碎屑流沉积物和水下砂和砾石。这两个岩相组合披覆由雨停，泥石流和牵引流活动的组合形成的杂岩。在一些地方，序列的上部被冰盖边缘的轻微振荡所剪切。
这些层序形成了一个广泛的冰海沉积带的一部分，该沉积带与爱尔兰中东部的鼓林群接壤。岩石地层的变异性部分与冰瓣边缘的大量碎片的到来时，主要的低地冰盖激增在德鲁姆林形成。这种类型的复杂沉积连续统缺乏任何重大的侵蚀间断，不应用作气候指标或地层对比。
Late Pleistocene morainic sequences around Dundalk Bay, eastern Ireland, were deposited in a variety of shallow, glaciomarine environments at the margins of a grounded ice lobe. The deposits are essentially ice-proximal delta-fan and -apron sequences and are divided into two lithofacies associations. Lithofacies association 1 occurs as a series of morainal banks formed at the southern margin of the ice lobe in a body of water open to influences from the Irish Sea. The morainal banks consist mainly of diamictic muds deposited from turbid plumes and by ice-rafting with minor occurrences of turbidites, cross-bedded gravels (subaqueous outwash) and massive boulder gravels (high-density debris flows). Lithofacies association 2 was deposited in a narrow arm of the sea at the north-eastern margin of the ice lobe. The deposits consist mainly of a series of coalescing, ice-proximal Gilbert-type fan deltas which are interbedded distally with tabular and lens-shaped subaqueous deposits. The latter are mainly ice-rafted diamictons, debris-flow deposits and subaqueous sands and gravels. Both lithofacies associations are draped by diamictons formed by a combination of rain-out, debris flow and traction-current activity. At a few localities the upper parts of the sequence have been sheared by minor oscillations of the ice sheet margin.
These sequences form part of an extensive belt of glaciomarine deposits which border the drumlin swarms of east-central Ireland. Lithostratigraphic variability is partially related to the arrival of large volumes of debris at the ice lobe margin when the main lowland ice sheet surged during drumlin formation. Complex depositional continua of this type lack any major erosional breaks and should not be used either as climatic proxies or for stratigraphic correlations.