Late Wisconsinan glacial sediments, exposed on Whidbey Island and Camano Island, Puget Sound (Washington State, USA), were deposited in a proglacial shallow marine/outwash environment during northward retreat of the Puget Lobe of the Cordilleran ice sheet. Sediments mainly comprise massive and cross-bedded sand and gravels, and rhythmically-bedded clay and silt/fine sand couplets, interbedded with diamictons that were deposited by a range of mass flows of different viscosities. Although sediment stratigraphy and ice advance–retreat patterns are well established for the Puget Lobe, brittle and ductile deformation structures within, and separating, these sediment units are less well understood. These structures record the nature of ice–bed interactions taking place in subglacial and proglacial environments. This study examines evidence for these processes and environments. Key deformation structures identified include open to overturned folds, normal and reverse faults, clastic dikes and hydrofractures and passive-loading structures. Evidence for coeval development of ductile and brittle deformation structures shows the close relationship between porewater changes, sediment rheology and sediment system responses to changes in strain caused by ice–bed interactions.

中文翻译：

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美国华盛顿州威斯康星州普吉特洛贝晚期的同时代脆性和韧性变形

威斯康星州晚期冰川沉积物暴露在普吉特海湾（美国华盛顿州）的惠德贝岛和卡马诺岛，在科迪勒拉冰盖的普吉特叶向北撤退期间沉积在前冰川浅海/外流环境中。沉积物主要包括块状和交错层状砂砾石，以及节律层状粘土和粉砂/细砂对联，夹杂着由一系列不同粘度的质量流沉积而成的硅藻土。尽管对于 Puget Lobe、内部的脆性和韧性变形结构以及分离的沉积物地层学和冰进退模式已经很好地建立起来，但对这些沉积物单元的了解较少。这些结构记录了冰下和前冰期环境中发生的冰床相互作用的性质。本研究检查了这些过程和环境的证据。确定的主要变形结构包括开放至翻转的褶皱、正向和反向断层、碎屑岩堤和水力裂缝以及被动加载结构。韧性和脆性变形结构同时发展的证据表明，孔隙水变化、沉积物流变性和沉积物系统对冰床相互作用引起的应变变化的响应之间存在密切关系。