24 EXPLORATIONS IN TURKESTAN. 
While it may be desirable later to make as precise a detennination as possible of 
the geologfical date and of the physiographic surroundino^s of human monuments or 
artifacts, it did not seem advisable to combine detailed local obsen-ations with a 
general reconnaissance during our first season in the field. My work was therefore 
directed to gaining a broad view of the region and its development, from which it 
should be possible to plan and direct a series of more thorough studies regarding 
the subdivisions of later geological time, in case such studies are to be undertaken 
in the coming years. It is a matter of regret that, owing to the deficient represen- 
tation of Russian material in our libraries, it has not been possible to make as full 
a study of the work of earlier observers as was desired in the preparation of this 
report. 
THE CASPIAN REGION. 
The region traversed naturally divides itself into three parts: The sea on 
the west, the mountains on the south and east, and the plains between the two. 
The waters of the Caspian are gathered in an area of relative depression ; the 
mountains are the scene of active erosion because of their relative elevation ; the 
ri\-ers stri\-e to earn,- the waste of the mountains down the \-er\- gentle slope of the 
plains and deposit it in the sea. The climatic changes, well proved to have taken 
place over other parts of the world in later geological times, may be believed to have 
had their effect in this region also. The Caspian is known to have stood at a greater 
height and to have covered a much larger area in Quaternary- time, especially to the 
east and north, as is attested by its abandoned strands and shell deposits; the 
existing glaciers of the eastern mountains have been longer than they are now, as 
proved b>- their abandoned Ouaternar}- moraines, reported by various explorers ; the 
rivers between the mountains and the sea must ha\-e, in some way appropriate to 
themselves, responded to these var\'ing conditions at their two extremities, and 
hence even in the strata of the plains some record of Quaternary' climatic variations 
may be discovered. • 
There can be no question, however, that the record of Quaternary climatic 
variations on the plains would be of much more difficult recognition than in tlie 
mountain valleys on the east, or around the great sea basin on the west. It was 
for this reason that my reconnaissance was directed chief!)- to the Caspian shorelines 
and to the extinct glaciers of the Tian Shan, and that the study of the plains was 
left to a later year. 
THE TERTIARY AND QUATERNARY CASPIAN. 
The existing Caspian Sea is the successor of the expanded water body of late 
Tertiary time which made the Black, the Caspian, and the Aral basins confluent 
and which laid down a series of stratified deposits, known as the (Tertiary) Aralo- 
Caspian fonnation, apparently the equivalent of the Congerian or Pontic stage 
of Europe. These deposits are now more or less deformed and eroded ; for example, 
near Baku and next eastward in the Apsheron peninsula, where the Caucasus range 
