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The record of episodic high-energy sedimentation in the western Oak Ridges Moraine, southern Ontario.

机译：在安大略省南部的橡树岭冰a西部发生的偶发性高能沉积记录。

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摘要

The 160 km long Oak Ridges Moraine in southern Ontario has been interpreted as an interlobate moraine, a subaerial braidplain-defaic deposit, a subglacially formed ridge, or a polygenetic landform of subglacial and proglacial deposits. Because of these significant differences a detailed sedimentological study is needed in order to provide an improved depositional model. This study of the western 40 km of the moraine in the Humber River watershed challenges the concept that it was deposited from seasonal meltwater discharges, climatic modulated ice-marginal fluctuations or in an interlobate position. Instead it is interpreted to have formed in response to changes in the ice-sheet during deglaciation associated with subglacial ponding, episodic and catastrophic subglacial jökulhlaup discharge and seasonal meltwater discharge. The moraine probably formed as the ice-sheet profile and glacial hydraulic system re-equilibrated to the presence of a thinned ice-sheet and a subglacial lake in the Lake Ontario basin.; The Oak Ridges Moraine is interpreted to have been deposited in three discrete stages that record sedimentation from both high-energy and low-energy depositional processes. Stage I consists mostly of massive and diffusely-graded sand that is up to 50 m thick and forms the lowest tunnel channel infill. It was deposited rapidly from hyperconcentrated flows some distance downflow of a hydraulic jump that developed as jökulhlaup flow discharged from tunnel channels into a subglacial lake in the Lake Ontario basin. Low energy basinal sedimentation of Stage II is recorded by the upward increase in thin normally graded fine-sand, silt, and clay laminae forming varves. Stage III is characterized by rapid facies changes associated with subaqueous fan, esker and basinal sedimentation. Proximal fan sediment consists of heterogeneous gravel with sand intraclasts and planar-stratified gravel. Immediately downflow the supercritical to subcritical flow transition is recorded by steep-wailed scours and diffusely-graded infill. Farther downflow the subcritical flow region of the fan is dominated by planar cross-stratified medium sand, climbing medium scale cross-stratified sand and small-scale cross-laminated fine sand.; Based on an incomplete verve chronology and general evidence of rapid and voluminous sedimentation it is estimated that the moraine was deposited over a short period of time, maybe as little as 100 years. This study provides an additional demonstration of the value of detailed sedimentological studies to advancing understanding of Laurentide meltwater and deglacial processes.
机译：安大略省南部长160公里的橡树岭冰Mor被解释为叶间冰m，陆缘辫状平原缺乏沉积物，冰川下形成的山脊或冰川下和冰川前沉积物的多基因地貌。由于这些重大差异，需要进行详细的沉积学研究，以提供一种改进的沉积模型。对汉伯河分水岭西部40公里处的冰study的这项研究提出了挑战，认为冰it是由季节性融水排放，气候调节的冰边际波动或处于叶间位置而沉积的。取而代之的是，它被解释为是由于冰川消融期间冰盖的变化而形成的，而冰川消融与冰川下的积水，偶发性和灾难性的冰川下的jökulhlaup排放以及季节性的融水排放有关。冰Ontario的形成可能是由于冰盖轮廓和冰川水力系统重新平衡，以致于安大略湖流域中出现了变薄的冰盖和冰下湖。橡树岭冰Mor被解释为分三个独立的阶段沉积，记录了高能和低能沉积过程的沉积。第一阶段主要由块状且散布的砂砾组成，其厚度最大为50 m，形成最低的隧道通道填充物。它是从高浓度水流中迅速沉积的，而水力跃迁沿一定距离向下流动，这是由于jökulhlaup流从隧道通道排放到安大略湖流域的冰川湖中而形成的。阶段II的低能盆地沉积是通过正常梯度的细砂，粉砂和粘土薄片形成的脉管上升而记录的。第三阶段的特征是与水下扇形沉积，沉积和盆地沉积有关的快速相变。扇形沉积物的近端由异质砾石，砂质内碎屑和平面分层砾石组成。立即通过陡峭的冲刷和弥散分级的填充物记录超临界至亚临界流动的向下流动。进一步向下流动时，风机的亚临界流动区域主要由平面交叉分层中型砂，爬升中规模交叉分层中砂和小规模交叉分层细砂为主。根据不完整的年代顺序和快速而大量沉积的一般证据，估计冰ora沉积时间很短，可能只有100年。这项研究进一步证明了详细的沉积学研究对增进对Laurentide融水和冰川消融过程的理解的价值。

著录项

  • 作者

    Russell, Hazen Algar John.;

  • 作者单位

    University of Ottawa (Canada).;

  • 授予单位 University of Ottawa (Canada).;
  • 学科 Geology.
  • 学位 Ph.D.
  • 年度 2001
  • 页码 293 p.
  • 总页数 293
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 地质学;
  • 关键词

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