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Facies architecture and stratigraphic heterogeneity in glacial deposits and their relation to hydrogeologic function.

机译：冰川沉积的相结构和地层非均质性及其与水文地质功能的关系。

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摘要

Glacial deposits are characterized by considerable stratigraphic heterogeneity but existing 'first generation' facies models are based almost exclusively on one-dimensional vertical profile descriptions of widely-spaced boreholes and outcrops. Such models do not adequately predict the three-dimensional geometry and heterogeneity of sedimentary facies for hydrogeologic purposes. This thesis demonstrates alternative approaches to the description of glacial deposits which integrate surface and downhole geophysical methods with architectural element analysis (AEA) of borehole data and outcrops. These methods are applied to better resolve the sedimentary architecture and hydrogeologic function of thick (>200 m) Late Pleistocene strata in southern Ontario.;AEA photomosaics of well exposed Pleistocene outcrops were integrated with an extensive subsurface GIS database consisting of drill core (>2300 m), downhole geophysical logs (natural gamma, EM conductivity) and shallow seismic reflection profiles (>12 line km) collected within a 1380 km 2 area east of Toronto. The basin stratigraphy consists of thick Late Wisconsin tills and intervening interstadial deposits overlying older glaciolacustrine sediments. Three primary aquifer systems were identified and large-scale trends in hydrogeologic parameters (hydraulic heads, transmissivity and hydraulic conductivity) were mapped. Aquifers are confined by finer-grained till deposits, including a thick (up to 60 m) regionally-extensive till member (Northern till) previously described as a homogeneous, highly impermeable aquitard. AEA and seismic reflection profiling in contrast, identify a composite internal till stratigraphy and the presence of heterogeneities over several length scales. Three principal architectural element types are identified: tabular diamict elements (DE), sorted sediment interbeds (I) and deformed zones (DZ) of complexly glaciotectonized strata. Architectural elements are defined by laterally extensive 4 th and 5th order bounding erosion surfaces and their correlative conformities; lower order surfaces define small-scale intra-element heterogeneities, including sorted sediment lenses, minor erosion surfaces and diamict 'increments'.;Accumulation of the Northern till involved aggradation of diamict elements punctuated by periods of non-deposition and subglaciofluvial reworking of till to form sorted interbeds. AEA identifies drumlins as macroforms resulting from aggradation of diamict elements across a pre-existing drumlinized erosion surface.;Interbeds and intra-element heterogeneities provide primary pathways for groundwater and contaminants through the Northern till; the lateral continuity (>103 m2) and interconnectedness of interbeds suggests a stair-case groundwater flow mechanism.
机译：冰川沉积物的特征是地层非均质性很强，但是现有的“第一代”相模型几乎完全基于对大范围钻孔和露头的一维垂直剖面描述。这样的模型不能为水文地质目的充分地预测沉积相的三维几何形状和非均质性。本文论证了冰川沉积物描述的替代方法，该方法将表层和井下地球物理方法与井眼数据和露头的建筑元素分析（AEA）相结合。这些方法可用于更好地解决安大略省南部厚（> 200 m）晚更新世地层的沉积构造和水文地质功能;将暴露良好的更新世露头的AEA光镶嵌与包括钻芯（> 2300）的广泛的地下GIS数据库集成在一起m），在多伦多以东1380 km 2区域内收集的井下地球物理测井曲线（自然伽马，电磁导率）和浅层地震反射剖面（> 12线千米）。盆地地层由较厚的威斯康星州晚期耕层和中间的陆相沉积物组成，这些沉积物覆盖在较早的冰川湖沉积物上。确定了三个主要的含水层系统，并绘制了水文地质参数（液压头，透射率和水力传导率）的大规模趋势。含水层被细粒度的直到沉积物所限制，包括之前描述为均匀，高度不可渗透的阿奎塔德的厚实区域（直至60m）的区域广泛的耕作成员（北部耕作）。相比之下，AEA和地震反射剖面可以识别出一个复合的内部地层，并且在几个长度尺度上都存在异质性。确定了三种主要的建筑元素类型：板状的铁素体元素（DE），分类的沉积物夹层（I）和复杂的冰川构造地层的变形带（DZ）。建筑元素是由横向扩展的四阶和五阶边界侵蚀面及其相关的一致性定义的。低阶表面定义了小规模的单元内异质性，包括分选的沉积物晶状体，较小的侵蚀面和铁素体的“增量”。形式排序交错。美国原子能机构（AEA）鉴定出鼓粉岩为宏观形态，这是由于预先存在的鼓粉化侵蚀表面上的敌敌畏元素聚集而形成的。互层和元素内非均质性为通过北部耕作区的地下水和污染物提供了主要途径。层间的横向连续性（> 103 m2）和互连性暗示了楼梯地下水流的机理。

著录项

  • 作者

    Boyce, Joseph Ian.;

  • 作者单位

    University of Toronto (Canada).;

  • 授予单位 University of Toronto (Canada).;
  • 学科 Geology.;Hydrologic sciences.
  • 学位 Ph.D.
  • 年度 1998
  • 页码 214 p.
  • 总页数 214
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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