A time-transgressive model for microstructures in subglacial tills - Examples from beneath the Late Wisconsinan (MI 2) Laurentide Ice Sheet

IF 1.2 4区地球科学 Q2 Earth and Planetary Sciences

Proceedings of the Geologists Association Pub Date : 2023-10-01 DOI:10.1016/j.pgeola.2023.05.005

John Menzies , Roger C. Paulen , Jessey M. Rice

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Abstract

The complexity of subglacial till sedimentology is discussed at the microscale to develop a revised model of microstructure evolution and development in subglacial tills. Mapped thin sections from the Northwest Territories and southern Ontario, Canada reveal a myriad of microstructures. Discussion of the relevance and meaning of these microstructures leads to a new revised model of subglacial soft sediment deformation to account for the development and evolution of these microstructures. The model is time-transgressive such that over time both pervasive and non-pervasive deformation conditions persist repetitively within the subglacial till environment under mixed rheologies. Microstructure types appear to be sequential in development and, during progression, are partially or wholly overprinted, destroyed, rotated, and suffer further subsequent deformation, or remain intact but intercalated with structures of other later or earlier deformation phases. This new revised model helps explain that the vagaries of till microsedimentology can be accounted for and, in most instances, predicted.

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冰下山丘微观结构的时间海侵模型——来自晚威斯康辛州(MI 2)劳伦泰德冰盖的例子

在微观尺度上讨论了冰下till沉积学的复杂性，建立了冰下till微观结构演化和发展的修正模型。加拿大西北地区和安大略省南部的薄剖面图显示了无数的微观结构。通过对这些微观结构的相关性和意义的讨论，提出了一个新的冰下软沉积物变形修正模型，以解释这些微结构的发展和演变。该模型是时间海侵的，因此随着时间的推移，在混合流变的冰下耕作环境中，普遍和非普遍变形条件反复存在。微观结构类型在发展中似乎是连续的，在发展过程中，部分或全部被叠加、破坏、旋转，并遭受进一步的后续变形，或者保持完整，但与其他后期或早期变形阶段的结构相嵌入。这一新的修订模型有助于解释，在大多数情况下，可以解释和预测till微沉降的变幻莫测。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Proceedings of the Geologists Association 地学-地质学

CiteScore

2.70

自引率

8.30%

发文量

审稿时长

6-12 weeks

期刊介绍： The Proceedings of the Geologists'' Association is an international geoscience journal that was founded in 1859 and publishes research and review papers on all aspects of Earth Science. In particular, papers will focus on the geology of northwestern Europe and the Mediterranean, including both the onshore and offshore record. Following a long tradition, the PGA will focus on: i) a range of article types (see below) on topics of wide relevance to Earth Sciences ii) papers on aspects of Earth Science that have societal relevance including geoconservation and Earth management, iii) papers on palaeoenvironments and palaeontology of the Mesozoic and Cenozoic, iv) papers on aspects of Quaternary geology and climate change, and v) papers on the history of geology with particular reference to individuals that have shaped the subject. These topics will also steer the content of the themes of the Special Issues that are published in the PGA.