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Show terminal recession at - 9,500 C yr B. P. These oscillations included a spike- like, major transgression to the maximum highstand centered somewhere between 14,000 and 13,500 14C yr B. P and a return to levels high enough for Pyramid Lake to spill into the Smoke Creek and Black Rock Desert basins at just before 10,000 ,4C yr B. P. Benson ( 1993) argues that the short duration of the maximum highstand indicates that the migrating jet stream spent very little time at the latitude of Lake Lahontan. Benson et al. ( 1992) associate the later, smaller transgression to the younger Dryas event. In the Holocene Lake Lahontan rose during one minor transgression to levels high enough so that Pyramid Lake spilled over into Winnemuca Dry Lake for the period from - 5,000 to 2,000 14C yr B. P. The high level of confidence in the Lahontan lake level history is no surprise. For the most part, this model is supported by an abundance of data which has received a great deal of scrutiny, especially in the critical interval of time from - 21,000 to 10,000 14C yr B. P. ( e. g., Benson, 1993; Szabo et al., 1996). The only major point of contention within this time interval is the timing of the maximum highstand. Bradbury et al ( 1989) argue that a Lahontan lake level high enough to incorporate the Walker Lake sub basin could not have occured after 23,000 C yr B. P. because a well dated sequence of sediments from Walker Lake show this lake to have been a saline lake or a play a for the entire interval from 23,000 to 5,000 14C yr B. P. ( Note: this sub basin held a shallow lake during a pluvial interval due a temporary diversion of its main source, the Walker River, into the Carson Sink). Furthermore, evidence for a deep lake during this highstand interval is also missing from the lake bottom sediments from a coring location in the Black Rock Desert ( Ewing, 1996) though this latter record does indicate a spike- like interval of fresh water conditions at the slightly older age of 14,500 14C yr B. P. The lack of evidence from lake bottom sediments from only two locations can be explained by deflation or even, perhaps by erosion from underwater currents or slumping. However, if a highstand lake did indeed exist at this time, then there must be a lake bottom sediment record preserved somewhere in the Lahontan basins. It is just a matter of time before such evidence is found assuming, of course, that the age range of sediments deposited during such a short highstand can be resolved with available dating technologies. Of the lake level history for the rest of the northwestern Great Basin, the most is known for three adjacent pluvial systems in south- central Oregon: Lake Chewaucan, Fort Rock Lake and Alkali Lake. Work in progress on Lake Chewaucan bottom sediments by R. Negrini, D. Erbes, M. Palacios- Fest, A. Cohen, P. Wigand, and earlier work by Allison ( 1982), Davis ( 1985), Berger ( 1991) have resulted in a multicomponent climate record of this basin for the time interval from approximately 230 ka to 18,000 14C yr B. P. Marginal outcrop and depocenter cores were correlated and assigned ages using lithostratigraphy, tephrochronology, sediment magnetism, paleomagnetic secular variation, radiometric methods and thermoluminescence. Paleoclimate was inferred from estimates of relative lake level through time based on high amplitude responses to lake level of lithostratigraphy, ostracod faunal analyses, geochemistry of ostracode shells, sediment magnetism and palynology. The imprecision of the resultant age control makes it impossible at the present time to determine the details regarding the response time of the Chewaucan lacustrine system to global climate changes. Thus, these records cannot be used yet as part of a geographically distributed data set with which to to test models linking Great Basin lake levels to, for example, jet stream migration. Nevertheless, the lake level of Pluvial Lake Chewaucan appeared to have varied more or less in accord with changes in global climate throughout the last couple of hundred thousand years ( Figure 1). Furthermore, the paleomagnetic secular variation ( PSV) of the Earth's magnetic field is resolved in great detail throughout much of the Chewaucan record which may eventually allow a high resolution temporal correlation with marine cores or other lake sediments. An example of the potential utility of the PSV record as a means with which to correlate climate records is its use in conjunction with the Wono tephra layer. Benson et al. ( 1997) demonstrated that the Wono tephra layer ( 27,300 ± 300 14C yr B. P.) fell during an interval |