September 19, 1884.] 



SCIENCE. 



273 



THE CARSON-CITY ICHNOLITES. 



The fossil footprints upon the layers of 

 sandstone in the quarry at Carson City, in the 

 state of Nevada, have excited much interest 

 and discussion, not onry by reason of the num- 

 ber and grouping of animals represented, but 

 especially because some of the tracks have a 

 rough resemblance to such footprints as a man 

 of great size might make in walking upon soft 

 mud. Elaborate reports and memoirs have 

 already appeared, 1 regarding these tracks ; and 

 in California and Nevada there has been, and 

 continues to be, a great difference of opinion as 

 to the origin of the tracks which resemble the 

 imprints of human feet. These tracks occur 

 in a light, gray-colored, coarse sandstone for- 

 mation, of the mammalian age of the tertiary, 

 Lying in nearry horizontal beds, with thin part- 

 ings or layers of clay at intervals. The sec- 

 tion at one point directly above one of the 

 series of tracks is as follows : — 



Sandy clay 18 inches. 



Sandstone 4 feet. 



Clay | inch. 



Sandstone 16 feet. 



Fine clay ...... 2 feet 2 inches. 



Coarse sandstone 10 " 



Sandy clay, with tracks ... 3 " 



Sandstone 18 to 24 " 



Clay layer, with tracks . 1 to 2 " 



Sandstone below the quarry floor, 38 feet. 



The tracks represent at least ten different 

 animals, as follows : Elephas, or the mam- 

 moth ; elk, or American reindeer ; Bos, or 

 buffalo ; horse ; wolf ; tiger ; peccary ; Mylo- 

 don, or a giant sloth; the so-called 'Homo 

 Nevadensis ; ' birds. 



Bones and teeth of the elephant and of the 

 horse have also been found in the sandstone 

 beds above the ichnolites. There are also 

 casts of shells of Anodonta, and an abundance 

 of casts of reeds and aquatic plants, directly 

 overlying the layers of silt or mud on which 

 the tracks are found. 



The sequence of events is plainly recorded 

 in these beds. The floor of the quarry marks 



1 Footprints found at the Carson state prison. By H. W. 

 Harkness, M.D. Proc. (Jul. acad. sc, Aug. 7, 1882. 



On certain remarkable tracks found in the rocks of Carson 

 quarry. By Joseph LeConte. Proc. Cal. acad. sc, Aug. 27, 

 1882. 



Prehistoric footprints in the sandstone quarry of the Nevada 

 state prison. Description by Charles Drayton Gtbbes, C.E., 

 Sept. 4, 1882, to accompany diagrams of footprints. 



Harkness, Ptoc. Cal. acad. sc, August, 1883. (Abstract 

 in New- York evening post.) 



O. C. Marsh, Amer. journ. sc, No. 152 [3] xxvi., August, 



The Carson footprints. Report of Professor George Da- 

 vidson, president of the California academy of sciences, August, 

 1883. 



Ichnolites of the Carson quarry. W. P. Blake. Trans. 

 Conn. acad. arts and sciences, February, 1884. 



the close of a period of strong currents of 

 water, depositing sand . A period of quiescence 

 ensued, with the deposition of a fine cla\- or 

 silt. This was drained of water, and became 

 firm enough for animals to walk upon it and 

 leave their tracks. This layer is separated 

 from a second clayey layer by about eighteen 

 inches of sand, marking an overflow and a 

 second period of quiescence and drying-up. 

 The tracks are most numerous and distinct 

 upon this second la} T er. Immediately over it 

 we find several inches in thickness of fine 

 clayey sediment, penetrated by aquatic plants, 

 with the remains of fresh-water shells, indicat- 

 ing the existence of a shallow lake or lagoon 

 for a considerable period. The overlying coarse 

 sandstones show the influx of strong currents, 

 bearing the sand and the bones of animals 

 from some point beyond, and higher than the 

 tracks. 



It is probable that these deposits were formed 

 near the mouth of a comparatively large stream, 

 subject to floods, and flowing into a shallow 

 lake. Such conditions are not unlike those 

 we now find all along the eastern base of the 

 Sierra Nevada, where mountain torrents pour 

 out into elevated valleys without outlet, and 

 form broad lakes, which vary greatby in their 

 extent at different seasons of the year. Dur- 

 ing the season of the melting of the snows, 

 the lakes cover a much greater area than in 

 the city season, when the rivers cease to flow, 

 and the lake- water disappears by evaporation. 

 Large areas of the shores of such lakes then 

 become exposed, and are gradually dried. If, 

 as in the case of the deposits under considera- 

 tion, the upper clayey sediments are underlaid 

 by coarse sandstone, the clay layer is rapidly 

 dried by under-draining, and affords a firm 

 footing for animals in search of water. This 

 need of water may account for the number of 

 animals which crowded together at this place. 

 It is possible, also, that a warm spring existed, 

 there, as at the present time, drawing animals 

 toward it from the surrounding deserts. 



The sandstone surface is distinctly marked 

 by raindrop pits and bj^ ripple or wave marks. 



Tracks of the mammoth or elephant. 



These appear as a series of circular depres- 

 sions from three to six inches in depth, and 

 averaging twenty inches in diameter. The 

 most important series is fort} 7 feet long, and 

 has ten distinct footprints. Most of these 

 have a raised margin or border of cla}* in 

 ridges, due to the great pressure and squeezing 

 of the clay. 



