. Central Asiatic Expeditions of the American Museum of Natural History, under the leadership of Roy Chapman Andrews : preliminary contributions in geology, palaeontology, and zoology. Central Asiatic Expeditions (1921-1930); Scientific expeditions; Natural history; Scientific expeditions; Natural history. 10 AMERICAN MUSEUM NOVITATES [No. 135 cutting them, it seems fair to infer that these Permian sediments are younger than the granite. It is possible, of course, that even the later intrusives, such as those which cut the Jurassic series, are products of the same great bathylithic magma, but
. Central Asiatic Expeditions of the American Museum of Natural History, under the leadership of Roy Chapman Andrews : preliminary contributions in geology, palaeontology, and zoology. Central Asiatic Expeditions (1921-1930); Scientific expeditions; Natural history; Scientific expeditions; Natural history. 10 AMERICAN MUSEUM NOVITATES [No. 135 cutting them, it seems fair to infer that these Permian sediments are younger than the granite. It is possible, of course, that even the later intrusives, such as those which cut the Jurassic series, are products of the same great bathylithic magma, but if so, they belong to a much later stage in its own develop- ment than that represented by the great areas of true granite. That stage, the stage of massive granite solidification which was also the stage of maximum invasion, is probably pre-Pennsylvanian, and certainly later than the Khangai graywacke. It is entirely possible that every igneous unit in the region, no matter what its age, is genetically connected with this immense bathylith. Its early developmental stages may have been responsible for the injection phenomena of the ancient gneisses; its maximum encroachment was attained in Paleozoic time, and its old age rejuvenations may in this view be recorded in the outbreaks of later periods (Fig. 7).. Great Monaolian Granite Bathylith Fig. 5. Typical section of the Khangai graywacke series. This section is from Five-Antelope Camp, 100 miles southwest of Urga. The simply folded graywacke-slate series is undercut and penetrated by the Great Mongolian Bathylith, and locally metamorphosed by contact influence over a very wide territory. This section reproduces a ten-mile stretch along the route followed by the Expedition within the northern mountain area. These granites show considerable variety of composition and minor habit, but the dominant type is a biotite granite of medium coarse tex- ture and massive structure. It has produced an extraordinary vaiiety of end-product ef
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