CHANGES OF DRAINAGE IN SOUTHWESTERN INDLANA. 99 



may be seen by reference to the map, PI. VIII. These perhaps may be 

 discussed to best advantage by beginning - at the east with the head waters 

 of the Patoka. 



The portion of the Patoka above Jasper seems to be following a 

 preglacial line, but at that town a deflection of the stream into another 

 drainage basin has been effected. The preglacial valley is easily traced 

 from the Patoka, in sec. 24, T. 1 S., R. 5 W., northwestward to Mill Creek 

 Valley and thence into East White River. Its breadth is about 1J miles, 

 and it has been filled with sand and loess-like silt to a height of 30 to 35 

 feet above the present level of Patoka River, in sec. 24, or to about 490 

 feet above tide. This filling was sufficient to turn the stream across a low 

 divide in the east part of Jasper. In opening a passage across this divide 

 the stream has accomplished a remarkably small amount of work. The 

 narrow part of the valley which marks the position of the old divide is only 

 about one-half mile in length, 600 to 800 feet in width, and 20 to 35 feet 

 in depth. The stream is reported to be several feet in depth through this 

 narrow portion, thus increasing the depth of erosion perhaps 10 feet. There 

 is in part of the gorge a thick-bedded sandstone which has probably greatly 

 resisted lateral erosion. 



Immediately south of Jasper the present Patoka River enters a valley 

 fully 1 mile in width which constitutes the preglacial line of discharge for 

 several southern tributaries entering" in Dubois County. The valley is not 

 occupied far by the present stream, but leads from Jasper in a course north of 

 west into Pike County, passing south of Ireland and directly under the vil- 

 lage of Otwell, its course for several miles being nearly coincident with Flat 

 Creek, though in the reverse direction. Whether it joined the East White 

 Valley near Highbanks or entered a few miles below, at the mouth of Mud 

 Creek, is undetermined. There are shallow valley-like depressions connect- 

 ing the abandoned valley with East AVhite River along each course which 

 are underlain by heavy deposits of drift, each of which apparently has a 

 width sufficient to have accommodated the old stream. Probably, however, 

 one of these lines will be found to be separated from the old valley by a 

 concealed rock barrier. This old valley, as above noted, has a rock floor 

 considerably below the present bed of the neighboring portion of East 

 White River, a boring at Otwell having failed to reach rock at a level about 

 35 feet below the river. 



