The Coastal Tundra at Barrow 15 



As the area occupied by the Biome research sites was exposed by a 

 late glacial regression of the sea, geomorphic processes related to extreme 

 cold climate again developed. The sediments that had thawed beneath 

 the shallow waters of the sea refroze to form a thick and continuous per- 

 mafrost section. Presumably, ice wedge formation was active under the 

 arctic climate that existed at that time, and has continued to the present. 

 Evidence from pollen recovered from a buried ice wedge and radiocar- 

 bon dating of organic matter immediately west of the Biome research 

 area indicates that by at least 14,000 BP a tundra as cold as at present, 

 but somewhat drier, existed (Colinvaux 1964, Brown 1965). Fecal pellets 

 of microtine rodents recovered in the same ice wedge sample indicate the 

 presence of these small mammals at that time. Since ice wedges were ac- 

 tively growing 14,000 years ago, it is reasonable to assume that the thaw 

 lake cycle (Britton 1957) as we know it today was also an active geo- 

 morphic process then. The detailed historical reconstruction of the 

 Biome research area that follows is based upon this assumption. 



In the Footprint Creek drainage a lacustrine peat immediately over- 

 lying the marine sediment at 2.2 m elevation has been radiocarbon dated 

 at 12,160 ±200 years (Figure 1-6). This date provides a maximum age for 

 the thaw lake. And since this peat directly overlies marine sediment, it 

 probably also dates one of the earliest thaw lakes in the area. Aerial 

 photographic interpretation suggests that the entire area was originally 

 covered by one large lake (Figure 1-5). The shoreHne of this lake abuts 

 the surrounding uplands at an elevation of 5.5 m on both the east and 

 west sides. The topographic high point on the west is known to contain 

 large quantities of segregated ice and ice wedges (Brown 1965) and is 

 probably a remnant of the primary land surface. The net effect of this 

 early lake was to thaw the ice-rich permafrost to a depth of 3 m and re- 

 work materials of the type still found to the west. In the process most of 

 the sea salts were removed from the sediments that form the parent mate- 

 rial of the present soils. 



The initial lake probably drained as headward erosion of the Middle 

 Salt Lagoon slough cut through a shallow pass in the elevated beach 

 ridge-shoal complex. With this draining or lowering of the lake level, the 

 newly exposed lake sediments refroze, tundra vegetation developed, and 

 a new cycle of ice wedge formation began. 



In time, smaller lakes developed in this large lake basin. Each lake 

 drained as headward erosion of the small tundra-covered stream chan- 

 nels intercepted the borders of the lake basins. The youngest and smallest 

 lake apparently formed the basin within which the ponds studied in the 

 Biome aquatic program are situated (site 7; Hobbie 1980). The present- 

 day polygonal ground is not only the product of current ice wedge for- 

 mation, but probably represents previous cycles of ice wedge growth, 

 both on land and under shallow lakes or ponds. The Biome research area 



