YELLOW MEDICINE, LYON AND LINCOLN COUNTIES. 599 



Cretaceous beds.] 



iflcatioii is plainly seen at the smaller end, being in layers from one to four or five inches thick. 

 Iron-rusted lamina:, a twentieth of an inch thick, sometimes mark the planes of bedding. The 

 weathered surface is in part perforated with holes from a quarter of an inch to one inch long and 

 about a twentieth of an inch in diameter, similar to those of worm-eaten wood. Other portions 

 exhibit a concretionary structure in small roundish masses and inosculated ridges, a fourth of an 

 inch in diameter or width. Sulphuret of iron is seen in two or three places, in somewhat cylin- 

 drical masses, about one and a half inches long, consisting of straight fibers, and surrounded by 

 stains of iron-rust. At another point near the foregoing, soft white matter tills a straight tube in 

 this stone, one and a half inches long and a quarter of an inch in diameter. These are believed 

 to be in the places originally occupied by fragments of wood, but are the only trace of organic 

 remains seen in this block. Its surface is soft and easily cut with a knife to a depth of about a 

 quarter of an inch, but farther within it is very hard. 



This rock is exposed about five miles to the southwest, in the N. E. } of section 20, Eids- 

 vold, on land of Henry Jacobs, being visible along an extent of about four rods in the bed of a 

 small creek and rising one to two feet. It is a compact hard sandstone, blue inside, but brown- 

 ish gray on the surface. The characteristic concretionary structure was seen here only in a de- 

 tached block, which, however, was doubtless derived from this underlying ledge. Again, near 

 the west line of this township and county the same formation outcrops along an extent of about 

 twenty feet, with a hight of one to two feet, in the north bank of the North branch of Yellow 

 Medicine river, in the S. W. J of the N. W. J of section 7, Eidsvold. 



In Alta Vista, the most northeast township of Lincoln county, this rock has a low outcrop 

 of similar extent with the last, in the south bank of the same stream, in the N. E. J of the S. E. 

 i of section 12, about ten rods west of the county line. This is on land of Col. Samuel McPhail, 

 some forty rods north of his house. The next and last outcrop of this formation is about a third 

 of a mile farther west, being in the S. W. i of the N. E. J of this section 12. It is on land of 

 George B. Mason, by whom this ledge, which is light gray calcareous sandstone, has been slight- 

 ly quarried, beginning in 1879, the price at which it is sold being $4 per cord. An excavation 

 about 80 feet long, 25 feet wide and 3 feet deep, has been thus made. The stone is in layers 

 from one inch to one and a half feet in thickness, dipping one to two degrees, or from two to five 

 feet in a hundred, to the east-northeast. In severaF places the bedding planes bear ripple-marks, 

 about three inches in width. These planes and the fissures of joints show on fully half of all their 

 exposed surfaces abundant concretionary rounded masses, an eighth to a quarter of an inch in 

 diameter; but this structure is not apparent within the stone to a greater depth than a half inch 

 or one inch, and is evidently brought into notice by weathering. No fossils could be detected 

 here nor in any of these outcrops; but the formation through its extent of seven miles from east 

 to west is nearly uniform in character, and is evidently the source of the masses noted in section 

 1, Eidsvold, which contain particles of lignite and traces of wood. 



In section 11, Ouster, Lyon county, on land cf James Morgan, much lignite in small frag- 

 ments is found along the large southern branch of the Cottonwood river, which there and thence 

 northeast to Amiret has cut a valley 75 to 100 feet deep. A tunnel has been dug into the lower 

 part of the bluff by Mr. Morgan, where springs occur at the top of a light bluish clay that is sup- 

 posed to be of Cretaceous age, and in this tunnel pieces of lignite and of wood were found. 



Clay or shale, containing fossils characteristic of the Fort Pierre and Fox Hills groups, the 

 upper divisions of the Cretaceous series, has been encountered in numerous instances by wells 

 in Yellow Medicine and Lyon counties near the foot of the slope which forms the eastern boun- 

 dary of the Coteau des Prairies. Doubtless some of these wells have reached Cretaceous strata 

 in place; but others evidently have been wholly in the glacial drift, containing disrupted and 

 transported masses of Cretaceous shale with fossils. The frequency of these fossils in the drift* 

 indicates that the upper Cretaceous formations originally covered much of this district and sup- 

 plied a large part of the drift, and that they probably underlie the drift here and in the Coteau 

 des Prairies. Notes of several of these sections are as follows: 



Wergeland. Peter Palmer; S. W. J of sec. 2: well, 51 feet; yellow and blue till, as usual, 

 with gravelly and sandy layers, 40 feet ; then blue clay, containing many fragments of Bacu- 

 lites and other fossils, pieces of lignite, concretionary nodules of pyrite, one to one and a 



"Compare also the occurrence of Baculilei in drift deposits in Brown county, pages 584 and 585; and in Nobles 

 ouuty, Am. Jour. Sci. (3), iii, 24. 1872. 



