720 A CENTURY OF PROGRESS IN THE NATURAL SCIENCES 



this series consists of red standstones, called the Eothliegendes, and an upper 

 magnesian limestone known as the Zeehstein. Eesting on the red sandstone at 

 the basis of the Zeehstein are black copper-bearing shales, the Kupferschiefer. 

 The Zeehstein also contains deposits of potash salts. Because of the economic im- 

 portance of these materials these rocks were studied in detail in the early part 

 of the last century. Beds of red conglomerate and magnesian limestone in Devon- 

 shire, England, were considered by Conybeare and Phillips to be equivalent to 

 the Eothliegendes and Zeehstein of Germany. 



Just before the middle of the last century Murchison, de Verneuil, and Key- 

 serling examined the thick series of marls, sandstones, and limestones which rest 

 on Upper Carboniferous beds in the west flanks of the Ural Mountains and pro- 

 posed the name Permian for this system, a term which was immediately adopted 

 in western Europe. In 1874 Karpinsky described beds with a transitional fauna 

 between Upper Carboniferous and Permian and designated them the Artinskian 

 stage. These faunas are known to have a wide distribution from the Arctic 

 Ocean to the Caspian Sea. A complex of Permian and Triassic continental beds 

 occurs in Central and Southern India; these have been studied by W. T. Blan- 

 ford, of the Indian Geological Survey, and named the Gondwana system by 

 Medlicott. These beds have yielded an important fossil flora, including the genus 

 Glossopteris, and many fossil reptiles. The fossils of this series are important 

 because of their widespread occurrence in Australia, Brazil, and South and East 

 Africa and have been used as partial evidence for the proposed continental con- 

 nections called Gondwanaland. The concept of Gondwanaland has been opposed 

 by many geologists and modified by others, notably by Schuchert in his paper 

 on Gondwanaland bridges. 



Evidence for glaciation during the Upper Carboniferous and Lower Permian 

 occurs in South Africa, India, Australia, Brazil, Uruguay, Bolivia, and the 

 Falkland Islands. The base of the Permian in Central India has been described 

 as consisting of nearly two thousand feet of an old tillite, resting on the striated 

 surface of older beds. These grade upward into sandstones and conglomerates 

 containing Glossopteris. A similar record has been noted by E. H. Schwarz in 

 South Africa, where the Dwyka tillite at the base of the Permian rests on a 

 polished and striated surface, with evidence that the movement of the ice was 

 southward away from the equator. In Australia, T. "W. David reports that the 

 tillite lies on Lower Carboniferous and older rocks and is overlain by coal- 

 bearing sandstones carrying the Glossopteris flora. Largely because of differ- 

 ences of opinion concerning the boundary between the Carboniferous and Per- 

 mian, many European and South African authors have tended to date the late 

 Paleozoic glaciation as Upper Carboniferous. In 1928 Schuchert, after a re- 

 view of the whole Permian problem, concluded that glaciation took place in 

 Middle, and probably late Middle, Permian. He interpreted the climatic change 

 as the result of the Ilercynian orogeny which began in early Carboniferous time 

 and continued periodically through the Upper Carboniferous into Permian time. 

 The Australian geologists T. W. David and C. A. Sussmilch disagreed with Schu- 

 chert's interpretation and in their reply in 1931 gave evidence of six glacial 

 stages, the first two of which were in mid-Carboniferous time, the third in Upper 

 Carboniferous, the fourth in the Lower Permian, and the last two near the top 

 of the Lower Permian. Later studies by A. C. Seward indicate that in Australia 



