GEOCHRONOLOGY 167 
scale so that our compilation of the paleoclimatic history for the 
area can then be continued. 
The detailed study of geomorphological conditions to determine 
the aridity of the land and its associated plant cover is also 1m- 
portant to our work. Such periods as those of arroyo cutting and 
filling are normally marked, or located nearby, by archaeological 
sites. Thus we have some method of determining their age. 
The study of the migrations of small modern mammals, as well 
as fossil remains, will greatly enhance our knowledge of the local 
conditions which prevailed at the time the animals lived in the 
area. This, coupled with the study of other types of fossils, should 
throw some light on the question as to why certain species of 
animals have either migrated or become extinct in this area. 
Several preliminary tests made in the playa lake beds in the 
Southwest indicate that detailed studies in paleolimnology and 
associated fields of micropaleontology, paleobotany, palynology, 
paleoecology, and non-glacial varve analysis would be most useful. 
From such studies we should be able to deduce specific climatic 
indices which could then be fitted to a time scale through the use 
of either carbon-14 analysis, or tree-ring dating, or some other 
method of dating. It is hoped that such studies can be extended 
into the third interglacial times so that an understanding of true 
interglacial conditions which prevailed in this area could be had. 
It is also essential that the so-called thermal maximum period 
(ca. 5500-2000 B.c.) be carefully studied for its detailed effects. 
Figure 2 is a tentative summary of the past climatic conditions, 
on a generalized basis, that have existed in the Southwest for the 
last 10,000 years; beyond this is an extrapolated period extending 
to the climax of the Wisconsin glaciation at ca. 25,000 B.c. This 
diagram has been compiled from many sources, mainly Antevs, 
Fries, Bryan, Ahlmann, and others. It is not intended that it be 
considered accurate. Rather it is intended to represent a working 
model to guide our future research. The weakest portion is that of 
the flora for which there is but little local information. It is hoped 
that with the study of palynology accelerating as it is, we soon can 
have a more accurate picture of this aspect. Our intentions are 
that, as we work on a locality and we incorporate the specific data 
