Rapid δ18O and δ13C isotopic shifts in late Pleistocene marine varves on the California margin

Upper Pleistocene sediments on the continental slope off Northern California contain alternations of varves and bioturbation produced by fluctuations in intensity of the coastal upwelling system. Stable isotopic analyses of benthic Foraminifera across a particularly well developed varve/bioturbation sequence deposited ~26,000 years ago reveal rapid shifts of ~0.25‰ in δ18O and ~0.4‰ in δ13C. The δ18O shift occurs within a varved section. Based on varve counts, the isotopic change occurred in less than 100 years. Timing and magnitude of the shift coincide with similar shifts observed in almost all other high-resolution δ18O records that have been interpreted as primarily representing global in-volume fluctuations.

Neogene through Pleistocene paleoclimate of the Great Salt Lake region, northeastern Great Basin, USA

In a cooperative agreement between Amoco Production Company and the University of Arizona Geosciences Department, extensive data and resources associated with 15 deep wells drilled in the Great Salt Lake are currently on loan at the University of Arizona. Seismic data, electric and lithologic logs, cuttings and previously-prepared pollen slides will eventually permit a thorough study of both the tectonic and climatic history of the Great Salt Lake region. The preliminary study presented here concentrates on the Late Tertiary and Pleistocene climatic reconstruction of the eastern Great Basin through examination of fossil pollen.

A late Pleistocene paleohydrologic record of Sierra Nevada runoff from Owens Lake, California [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): A 323-meter (about 800,000 year) core of lake deposits beneath Owens Lake playa, Inyo County, California, contains a nearly continuous paleolimnological record based on diatom assemblages. ... Throughout most of its history, Owens Lake was characterized by freshwater diatoms, indicating a positive hydrologic input from the Owens River and overflow to lake systems downstream.

A rock-magnetic and geomagnetic secular variation record from late-Pleistocene Lake Estancia, New Mexico [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): Exposed sediments of Late Pleistocene Lake Estancia contain a high resolution record of regional climate variability for the period about 12,000 to 32,000 years. A detailed rock-magnetic study is being performed on this well-dated, well-preserved sedimentary sequence to determine how the magnetic signature of sediments responded to regional climate change.

Investigation of extinction in unsteady flames in turbulent combustion by 2D-LIF of OH radials and flamelet analysis

An experimental and theoretical investigation of premixed turbulent combustion in an engine simulator is presented. The distribution of hydroxyl radicals formed in the combustion of propane/air mixtures was visualized by 2D-LIF and used to monitor the progress of the combustion process. For stoichiometric mixtures, images showed a continuous wrinkled flame front, while in lean (λ=1.5) mixtures, local flame extinction was observed as discontinuities in the reaction zone. A bright active reaction zone was still observed in flame inlets and closed concave structures. The effects of self-absorption and of collisional quenching on the fluorescence signal are considered and appear to have only a minor net influence on the shape and width of the flame front. The images are evaluated and interpreted in terms of the Lewis number effect and the laminar flamelet model. Analysis was performed by determining the contour lines of the images (specifically, the ratios of average maximum to equilibrium OH concentration) and comparing with corresponding ratios from unstrained flame simulations. The results show that although the degree of turbulence is not high enough for straining effects to be important, flamelet curvature does play a significant role in the combustion of lean mixtures; this is manifested by a mean effective flame velocity that is less than the laminar burning velocity. © 1991 Combustion Institute.

Late Pleistocene divergence and subsequent population expansion of two closely related fish species, Japanese anchovy (Engraulis japonicus) and Australian anchovy (Engraulis australis)

Climatic oscillations during the Pleistocene ice ages produced great changes in species' geographical distribution and abundance, which could be expected to have genetic consequences. Living in the temperate upwelling zones of the northwestern Pacific, Ja

Chronic morphine selectively impairs cued fear extinction in rats: Implications for anxiety disorders associated with opiate use

Previous studies have shown that opioid transmission plays an important role in learning and memory. However, little is known about the course of opiate-associated learning and memory deficits after cessation of chronic opiate use in a behavioral animal m