Page:The Journal of geology (IA journalofgeology11893univ).pdf/145
Explanation of Map.—This map was designed for another purpose, and hence includes only a portion of the district under discussion, though it represents the principal features herein discussed. Certain features, not discussed at this time, beach lines, eskers, esker troughs, etc., appear on the map.
The shaded portions of the map represent moraines, the shading being graduated to the strength of the moraine. Arrows indicate the position and bearing of striæ. Continuous lines are used to indicate the beaches of the Maumee basin and the south-western outlet of the lake which formed them. The second beach has not been fully traced, and is therefore incompletely represented. For the same reason the fourth and later beaches are not represented. Esker troughs are bounded by broken lines. The eskers which lie in them are indicated by continuous straight lines. The boundaries between upland and lowland tracts in southern Ohio are indicated by dotted lines. The glacial boundary, indicated by a broken line, appears for a short distance in the vicinity of Cincinnati.
the state there is a more complete and more easily deciphered record of the glacial succession than in the eastern portion, since the later advances there left a portion of the earlier drift uncovered. Our remarks will, therefore, relate chiefly to that district.
The full series of moraines formed by the Great Miami ice lobe, together with portions of the outer moraines of the adjoining East White River lobe on the west, and of the Scioto lobe on the east, are shown on the accompanying map. Outside the outer moraine of these lobes there is a glaciated district extending southward beyond the limits of the map in the main, its southern margin being the glacial boundary which lies fifteen to forty miles south from this moraine. That a long interval elapsed between the deposition of this outlying drift sheet and the formation of the outermost frontal moraine is shown below. Attention is called to it at this point, since it furnishes a convenient landmark in our discussion. The drift to the north of this moraine will be called, for convenience, by the general term, the later drift, while that to the south will be called the earlier drift. Both drifts have a somewhat complex history, and will be subdivided further on.
The earlier drift. For a few miles back from the glacial boundary in Northern Kentucky and in the hilly districts of