North America

For North America, most Holocene paleolimnologi-cal records are for the northern continental interior, with relatively few for western and eastern regions (Fig. 1; Table 1) or for high latitudes (Fig. 2; Table 1). In nearly all North America records, the mid-Holocene is an interval of severe aridity, although the onset, duration, and magnitude of aridity vary considerably among the sites (Table 1).

15.2.1. Western North America

In the Great Basin and elsewhere in the southwestern United States, many lake basins became dry in the early Holocene, following late glacial levels that were higher than they are now. Thus, there are few complete Holocene records. The large lakes in the northern Great Basin, all part of the glacial Lake Lahontan and Lake Bonneville systems, underwent dramatic expansion and contraction during the late Quaternary (Benson et al., 1990, 1996), but there are relatively few studies of Holocene fluctuations. Lithologic data, combined with algal remains, for Ruby Marshes in Nevada (Thompson, 1992) suggest dry to shallow conditions from the early through the mid-Holocene, with deepening after 4700 B.P., a pattern similar to that in Diamond Pond in Oregon (Wigand, 1987). Pore-fluid data for a core from Walker Lake in Nevada, which occupies the southernmost basin of glacial Lake Lahontan, indicate it became a playa at ca. 9000 B.P. (Benson, 1978). Refilling of Walk-

Prik Til Prik 200
FIGURE 1 Map of the United States and southern Canada showing locations of sites mentioned in the text. (See Table 1 for an explanation of the numbers.)
Carte Provinces Canada
FIGURE 2 Map of boreal and Arctic regions of North America showing locations of sites mentioned in the text. (See Table 1 for an explanation of the numbers.)
TABLE 1 List of North American Lake Sites Referred to in the Text





Chappice, Alberta

Vance et al., 1992

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