45 



During- the latter part of the Devonian Era those lowly acrogeuous 

 plants known as Rhizocarps flourished in vast numbers in the fresh 

 waters and brackish marshes of the time, and their spores by count- 

 less millions of tons were carried out as sediment into the surrounding 

 seas. ^Mingling with the mud and silt and sand, brought down by 

 erosion from the rapidly increasing land surface, they formed those 

 vast mud flats which have since, by age and pressure, been consolidated 

 into the thick beds of brown and black, finely-laminated shales which 

 form the rocks of the Genesee epoch in Indiana. At New Albany the 

 outcrops of this shale are 104 feet in thickness and especially prominent, 

 so that the local name, "New Albany black shale," has been given 

 it by geologists of the State. Along the western edge of the Corniferous 

 limestone this shale forms a continuous strip, 3 to 35 miles in width, 

 reaching from the present sue of New Albany north and northwesterly 

 to Delphi and Rensselaer. Over much of this strip it is covered by 

 a thick mantle of drift, but everywhere within the area wells or the 

 eroding streams have proven it to be the surface rock. The black shale 

 has also, by deep bores, been found to be the rock immediately under- 

 lying the drift over much of the area embraced within the two northern 

 tiers of counties in the State. 



The Genesee shale is rich in bitumens, derived from the spores of 

 the ancient Rhizocarps, which also gave it color. When kindled, it 

 will burn until they are consumed, and it is thei'efore, by the uninitiated, 

 often mistaken for coal. These bitumens are, by natural processes, some- 

 times separated from the shale and in the form of gas or petroleum 

 are collected in reservoirs in it or in the underlying Corniferous lime- 

 stone. 



During the thousands of centuries of the Devonian Period, a great 

 advancement took place in the flora and fauna of the times, especially 

 in the vegetation of the land and the development of the higher aquatic 

 vertebrates. Among the acrogens growing on land, ground pines, tree 

 ferns and equiseta or horse-tails came into existence and flourished 

 in vast numbers. Their remains are often found in the Corniferous 

 limestone, into the sediment of which they were drifted and preserved. 

 The first Phanerogams, conifers of the yew and cycad families, were 

 also evolved, their leaves and branches being found in the upper or 

 Hamilton beds of the Corniferous epoch. As the land plants increased 

 in number and variety, insect life became more varied and numerous. 



