The quaternary of the United States. A review volume for the VII congress of the international association for quaternary research / Четвертичный период США. Материалы 7-го конгресса международного совещания по проблемам исследования четвертичного периода

The quaternary of the United States THE QUATERNARY PERIOD of geologic time encompasses the last ice age proper (Pleistocene Epoch) and subsequent time (Holocene or Recent Epoch). The Quaternary is unique among the geologic periods for the relative perfection of its stratigraphic record—and thus for the unmatched opportunity it affords to decipher historical details with an accuracy impossible for earlier periods. The framework of the continents even in early-Quaternary time resembled that of the present so closely that major relations of land and sea and their effects on the general circulation of the atmosphere were probably very like those of the present, except perhaps when world-wide lowering of sea level exposed continental shelves or created significant land bridges between continents and arctic islands. Reconstructions of past conditions therefore may be controlled by a geographic framework relatively easy to visualize. <...>