52 M. C. Miller et al. 



these lakes because of reworking and movement of organic sediments, but 

 Lewellen (1972) reported that the maximum age of a lake is probably 

 12,000 years (based on a ^*C date of a lacustrine peat overlying a marine 

 sediment). Other recently-drained lake basins near Barrow may be 3000 to 

 5000 years old (Brown 1965). 



The present land surface and the ponds at the IBP site are relatively 

 younger than the basins studied by Brown. The most recent lake drained 

 into Footprint Creek, through a small outlet on the east side of the basin 

 (site of weir 1, Figure 3-1). There is no definitive evidence for the age of 

 this event; it probably took place several thousand years ago. 



The ponds themselves form in the center of ice wedge polygons. As 

 the ice wedges grow in the permafrost over a period of centuries, ridges or 

 rims are formed due to the upward displacement of soils (Lachenbruch 

 1962). The central depressions of these low-centered polygons form the 

 pond basins. With time these small ponds may erode; the surrounding rims 

 then coalesce to form larger ponds and eventually lakes, a process termed 

 "the thaw lake cycle" (Britton 1957). 



FIGURE 3-1. Ponds and outlets of site 7 drainage basin for pond com- 

 parison, 18 August 1972. The solid lines are the borders of the polygons 

 and the stippled area indicates open water. The dashed line encloses the 

 drainage basin. The numbers along the right side of the drainage basin 

 indicate weirs for water flow measurement. 



