322 
exposed along Dutch Creek, in the southwest corner of Union county. 
Grand Tower limestone, a layer about 150 feet in thickness, is well 
exposed in an old quarry a short distance east of Grand Tower, in Jack- 
son county. Lingle limestone and Meisenheimer shale are other repre- 
sentatives of the Middle Devonian. The Upper Devonian is made up of 
two layers, the Alto Pass formation and the Mountain Glen shale, which 
is a black shale showing up near Mountain Glen, northwest of Jonesboro. 
Above the Devonian is the Mississippian, shown at the extreme right 
of Plate LXXI, and this is divided into the Lower Mississippian and the 
Upper Mississippian, the latter being known as the “Chester group.”. The 
Springville, or “calico,” shale (locally called “ganister”,) which is mined 
in some places to be manufactured into refractory fire-brick, is classed 
with the Lower Mississippian. The Chester group is made up of lime- 
stones, sandstones, and shales, from 700 to 1,200 feet in thickness, and 
it is partly in this group that the sink-holes in the region of Anna are 
developed, that entire region being a limestone area. Proceeding upwards, 
we come to the Pennsylvanian, whose lower layer is the Pottsville sand- 
stone which forms the bluffs at Pomona, all of the northeast corner of 
the Dongola quadrangle being in fact mostly sandstone where there is 
considerable poor, gullied land. 
Above the Upper Mississippian are the layers of the Carboniferous 
which contain coal beds developed at Murphysboro, Herrin, and Harris- 
burg—more thoroughly described in the published geology of the Herrin 
quadrangle. The coal beds indicate that at intervals there were fresh- 
water marshes which received an accumulation of plant remains, this coal 
being formed during what is known as the Carbondale and McLeansboro 
periods of the Pennsylvanian. 
The Permian epoch, which followed the Carboniferous, was one of 
uplift, faulting, and intrusions of lava, during which the eastern extension 
of the Ozark highlands occurred, and as a consequence of which we have 
faults, dikes, and volcanic plugs formed in many of the southern counties. 
During Cretaceous and Tertiary times, clays, sands, and gravels were 
laid down, as shown in the lower right-hand corner of Plate LXXI, from 
Fayville to Tamms. After this came the deposit of sands, gravels, and 
clays, with glaciation of part of the area during the Quaternary or more 
recent period. 
Glactal and wind action.—As can be seen from Plate LX XI, the south- 
ern limit of the Ilinoian ice sheet extends across the northwestern corner 
of our area. According to Savage and Shaw (712), this last advance of the 
glaciers southwards covered about 1000 square miles south of the parallel 
38 degrees. It left no sign of a terminal moraine, but worked over mate- 
rial deposited previously, brought down rocks, such as quartz, from Can- 
ada, and filled up and modified former drainage channels. An example of 
