ABSTRACT This paper summarizes the hydrological variability in eastern California (central Sierra Nevada) for the past 3000 yr based on three distinct paleoclimate proxies, δ 18 O, total inorganic carbon (TIC), and magnetic susceptibility (chi). These proxies, which are recorded in lake sediments of Pyramid Lake and Walker Lake, Nevada, and Mono Lake and Owens Lake, California, indicate lake-level changes that are mostly due to variations in Sierra Nevada snowpack and rainfall. We evaluated lake-level changes in the four Great Basin lake systems with regard to sediment-core locations and lake-basin morphologies, to the extent that these two factors influence the paleoclimate proxy records. We documented the strengths and weaknesses of each proxy and argue that a systematic study of all three proxies together significantly enhances our ability to characterize the regional pattern, chronology, and resolution of hydrological variability. We used paleomagnetic secular variation (PSV) to develop paleomagnetic chronostratigraphies for all four lakes. We previously published PSV records for three of the lakes (Mono, Owens, Pyramid) and developed a new PSV record herein for Walker Lake. We show that our PSV chronostratigraphies are almost identical to previously established radiocarbon-based chronologies, but that there are differences of 20–200 yr in individual age records. In addition, we used eight of the PSV inclination features to provide isochrons that permit exacting correlations between lake records. We also evaluated the temporal resolution of our proxies. Most can document decadal-scale variability over the past 1000 yr, multidecadal-scale variability for the past 2000 yr, and centennial-scale variability between 2000 and 3000 yr ago. Comparisons among our proxies show a strong coherence in the pattern of lake-level variability for all four lakes. Pyramid Lake and Walker Lake have the longest and highest-resolution records. The δ 18 O and TIC records yield the same pattern of lake-level variability; however, TIC may allow a somewhat higher-frequency resolution. It is not clear, however, which proxy best estimates the absolute amplitude of lake-level variability. Chi is the only available proxy that records lake-level variability in all four lakes prior to 2000 yr ago, and it shows consistent evidence of a large multicentennial period of drought. TIC, chi, and δ 18 O are integrative proxies in that they display the cumulative record of hydrologic variability in each lake basin. Tree-ring estimations of hydrological variability, by contrast, are incremental proxies that estimate annual variability. We compared our integrated proxies with tree-ring incremental proxies and found a strong correspondence among the two groups of proxies if the tree-ring proxies are smoothed to decadal or multidecadal averages. Together, these results indicate a common pattern of wet/dry variability in California (Sierra Nevada snowpack/rainfall) extending from a few years (notable only in the tree-ring data) to perhaps 1000 yr. Notable hydrologic variability has occurred at all time scales and should continue into the future.

Abstract Driven by requests to provide carbonate analogs for subsurface hydrocarbon exploration in rift settings, we have identified and described select examples, summarized them from a carbonate perspective, and assembled them into a GIS database. The analogs show a spectrum of sizes, shapes and styles of deposition for lacustrine and marginal marine settings, wherein the types of carbonates inferred from seismic and cores (emphasis on microbialites, tufas, and travertines) can be illustrated.

The Walker Lane, a zone of northwest-striking dextral faults east of the Sierra Nevada, accommodates 15%–25% of Pacific–North American plate motion. A distinctive feature of the Walker Lane is the coexistence of parallel dextral and normal faults, which either developed sequentially or are related by strain partitioning. In the northern Walker Lane, three en echelon dextral faults strike northwest parallel to relative motion between the Sierra Nevada and Great Basin. Each fault cuts major basins but is parallel to and 1–5 km basinward of range-front normal faults. Basins in this area have anomalous northwest trends, whereas basins and major normal faults in the adjoining Basin and Range province trend north to north-northeast. Major normal fault systems straddling the northern Walker Lane dip toward one another, thereby producing a structural low. Significant exhumation related to strike-slip faulting is restricted to one, more westerly striking, probably transpressional segment of one dextral fault. Geologic data suggest that northwest-striking range-front faults were active during a ca. 3 Ma episode of extension but have been inactive in the Quaternary. Strike-slip faulting probably started immediately after 3 Ma, either cutting or reactivating deeper parts of the northwest-striking range-front normal faults as dextral faults. North-striking normal faults are active and kinematically compatible with the northwest-striking dextral faults. The unusual northwest strike of normal faults in the northern Walker Lane may reflect reactivation of a major northwest-striking basement structure indicated by gravity data. Strain partitioning between parallel dextral and normal faults is unnecessary because the dextral faults parallel Sierra Nevada–Great Basin motion and can take up all required displacement. In contrast, Sierra Nevada–Great Basin motion in Owens Valley in the southern Walker Lane is strongly oblique to faults, so strain partitioning between parallel dextral and normal faults may be necessary.