Bedrock jointing and geomorphology in southwestern Ontario, Canada: an example of tectonic predesign
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Early Pleistocene
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Comparison of a generalized 250-foot contour map of the bedrock surface and the glacial map of central United States shows that the Pleistocene glacial lobes were closely controlled by bedrock lowlands even in areas of relatively thick drift and that positions of ice centers and deflection by adjoining lobes were of secondary importance. The implications of these relations in the study of glacial centers and possible flow units within glacial lobes are considered, and an interpretation of preglacial drainage, based on the bedrock-surface map, is proposed.
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"Caledonian vein mineralizations in the Proterozoic basement of northern Sweden." Geologiska Föreningen i Stockholm Förhandlingar, 113(1), pp. 62–63
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A general introduction to the Pleistocene with an emphasis on herpetological remains was presented in the companion volume Pleistocene Amphibians and Reptiles in North America (Holman, 1995c). For a general introduction to the Pleistocene that gives much attention to Britain and Europe, the reader is referred to Sutcliffe (1985). A detailed account of Pleistocene mammals in Britain is given by Stuart (1982), and a general account of Pleistocene mammals in Europe is given by Kurten (1968). The present chapter deals mainly with chronological divisions of the Pleistocene in Britain and Europe. Early geologists recognized that glacial deposits and land forms existed far south of existing glaciated areas, and they correctly reasoned that these features indicated not only the presence of ice sheets but the onset of cold climates, as well. As these features were mapped and stratigraphic studies were made, it was found that some sections contained weathered zones of organic soils and plant remains between layers of glacially derived sediments. It was suggested that these organic zones represented nonglacial environments and that ice sheets must have advanced and retreated several times. In Europe, before studies of deep sea sediments were made, Pleistocene chronological events were determined on the basis of piecemeal evidence from terrestrial sediments. The earliest widely accepted chronology of climatic Pleistocene intervals was the classic fourfold subdivision of Pleistocene glacial events in the Alps by Penck and Bruckner (1909). These glacial stage names, from oldest to youngest, are Gu'nz glacial, Mindcl glacial, Riss glacial, and Wiirm glacial. Between the glacial stages, intcrglacial stages were designated by compound names based on the underlying and overlying glacial stages (e.g., The Gunz-Mindel intcrglacial stage lies between the Giinz and Mindel glacial stages). These Alpine glacial stages have been widely used, and one still finds references to them (especially the younger stages) in the recent literature (e.g., Fritz, 1995).
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Comparison of a generalized 250-foot contour map of the bedrock surface and the glacial map of central United States shows that the Pleistocene glacial lobes were closely controlled by bedrock lowlands even in areas of relatively thick drift and that positions of ice centers and deflection by adjoining lobes were of secondary importance. The implications of these relations in the study of glacial centers and possible flow units within glacial lobes are considered, and an interpretation of preglacial drainage, based on the bedrock-surface map, is proposed.
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The criticisms and views expressed in the recently circulated preliminary report of the Pleistocene committee of the American Commission on Stratigraphic Nomenclature on the present stratigraphic system of classification of the Quaternary suggest some lack of familiarity with the classic area of the Middle West. The multiple classification that the committee recommends, excellent as it may be for the older rocks, is not compatible with the nature of the glacial Pleistocene. The classification for the older rocks is the natural result of acquiring an understanding of them, just as the present classification of the glacial Pleistocene has evolved from decades of investigation. The classic area of the glacial Pleistocene comprises all of the type areas for the known glacial and interglacial stages of North America. So influential were the climates on most geologic processes, even in the depths of the ocean, that correlations with the glacial and interglacial stages of the Pleistocene are sought from all quarters. It is therefore important that the system of stratigraphic classification for the glacial Pleistocene shall be one that is naturally adapted to it rather than one that applies to marine strata. The non-glacial Pleistocene, however, may well be susceptible to the latter.
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Yulong Mountains (27°10′～27°40′N, 100°9′～100°20′E), situated in the north of Lijiang County, Yunnan Province and the southeast margin of the Tibetan Plateau, are the southernmost mountains with glaciers both in China and Eurasia Along their east, northeast and west feet, there is a series of relics of the Pleistocene glaciation Studying these glaciation relics and reconstructing their history of evolution have not only an important scientific implication for understanding the changes of glaciation, climate and environment and for discussing the uplift of the Hengduan Mountains and the Tibetan Plateau, as well as the development of the Jinsha River valley and the formation and development of Asian monsoon, but also major practical values for developing and protecting the tremendous resources of hydraulics and tourism in this area The authors survey, research and map the Pleistocene glacial deposits along the eastern foot of the Yulong Mountains based on the topographic map with the scale of 1∶10 000 and air-photographs, determining ESR dates of samples of calcareous cements from the glacial and fluvioglacial deposits as well as the calcareous glacio-lacustrine deposits, dividing them into four glaciations, i e the early Middle Pleistocene Yulong Glaciation (0 7～0 6 Ma BP), the middle Middle Pleistocene Ganhaizi Glaciation (0 53～0 45 Ma BP), the late Middle Pleistocene Lijiang Glaciation (0 31～0 13 Ma BP) and the Late Pleistocene Dali Glaciation, and correlating them with the glaciations on the Tibetan Plateau Results of study show that the Yulong Mountains area was a part of the united peneplain from the Tibetan Plateau to the Yunnan-Guizhou Plateau, 500～1 000 m a s l , during the Miocene In the Pliocene and the Early Pleistocene, the Yulong Mountains uplifted and the Lijiang Basin, Daju Basin, Longpan Valley and other basins subsided due to the fault activities In the early Middle Pleistocene, the Yulong Mountains had uplifted over the snowline, and giant piedmont glaciers of the Yulong Glaciation, the largest glaciation in this area, occurred at their east, west and northeast feet The glaciers in the Ganhaizi Glaciation were also piedmont ones, but muchsmaller than the former During the following grand interglacial, the Longpan Valley and the Daju Basin became two lakes, and then cut by the modern Jinsha River In the late Middle Pleistocene and the Late Pleistocene, the larger-scale valley glaciers of the Lijiang and Dali Glaciations developed in the tributaries of the Jinsha River
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