Abstracts / Quaternary International 310 (2013) 227–246246

benthic foraminifera (Uvigerina peregrina) and planktonic foraminiferalassemblage analyses including % N. pachyderma (d), and sediment lami-nation data. d18O data of G. bulloides and N. pachyderma show shifts of up to1.4& in as briefly as w80 years and 2.5& over w1000 years duringwarming. Water column stratification (shown by the difference between G.bulloides and N. pachyderma d18O) increases during interstadials. The % N.pachyderma (d) often varies in tandem with planktonic d18O, but exhibitsthreshold behavior instead of smooth change, and is generally higherduring interstadials and/or moderate water column stratification. d13Cvalues broadly correlate with shifts in d18O, and reflect changing oceancirculation, carbon cycling, and/or methane release. Preserved sedimentlaminations coincide with intervals of warm, stratified upper waters. Acomparison of our data to SBB records from the past 60,000 years (Behland Kennett, 1996; Hendy and Kennett, 1999, 2000; Hill et al., 2006) showsthat typical stadial-interstadial shifts in planktonic d18O (w1.5&) aresimilar to those recorded during the past 60,000 years, although changesin % N. pachyderma (d) are smaller, and planktonic assemblages are slightlydifferent, with fewer G. bulloides, Globigerina quinqueloba, Globorotaliascitula, and more N. pachyderma (s).

Behl, R.J., Kennett, J.P., 1996. Brief interstadial events in the Santa BarbaraBasin, NE Pacific, during the last 60 kyr: Nature 376, 243-246.Hendy, I.L., Kennett, J.P., 1999. Latest Quaternary North Pacific surfacewater responses imply atmospherically-driven climate instability: Geology27 (4), 291-294.Hendy, I.L., Kennett, J.P., 2000. Stable isotope stratigraphy and paleo-ceanography of the last 170 ka: ODP Site 1014, Tanner Basin, California:Ocean Drilling Program Scientific Reports 167, 129-140.Hill, T.M., Kennett, J.P., Pak, D.K., Behl, R.J., Robert, C., Beaufort, L., 2006. Pre-Bølling warming in Santa Barbara Basin, California: Surface and interme-diate water records of early deglacial warmth: Quaternary Science Reviews25 (21-22), 2835-2845.

CLIMATE DRIVERS OF STREAMFLOW SYNCHRONICITY IN WESTERN USRIVERS OVER MULTIPLE CENTURIES

Erika K. Wise. Department of Geography, University of North Carolina atChapel Hill, Chapel Hill, NC 27599, USAE-mail address: ekwise@email.unc.edu

Twentieth century high- and low-streamflow events in the western UShave been linked to Pacific and Atlantic Ocean influences, including thosedescribed by the El Niño–Southern Oscillation (ENSO), the Pacific DecadalOscillation, and the Atlantic Multidecadal Oscillation. Extended stream-flow records, reconstructed using tree rings, have identified drought andpluvial periods in the past that were more extreme than those recordedduring in the instrumental record. This study compares a new tree-ringbased reconstruction of Snake River streamflow with streamflow re-constructions of the Colorado, Sacramento, and Verde rivers. Resultssuggest that changes in the predominance of zonal versus meridional at-mospheric flow may have influenced patterns of synchronous and asyn-chronous streamflow in the four rivers. Spatial drought patterns indicatea zonal flow pattern during two of the most severe droughts in the SnakeRiver record (the 1630s and the 1930s), which weremuch less severe in theVerde River record. The Snake River's low-flow period in the early 1700s,which was less severe in magnitude, is replicated in the flow of all fourrivers and may be indicative of persistent meridional flow. These droughtpatterns appear to correspond to shifts in Pacific Ocean conditions; how-ever, direct comparisons between these periods and reconstructed indicessuch as ENSO are hindered by inconsistencies between existing re-constructions of paleo-teleconnections.

VARIATION IN FORAMINIFERAL DISTRIBUTIONS ACROSS THEPLEISTOCENE-HOLOCENE TRANSITION OFF THE KAYAK SLOPE,NORTHERN GULF OF ALASKA

Sarah D. Zellers, Kathryn Mueller, Diana D. Hill. Department of Biology andEarth Science, University of Central Missouri, Warrensburg, MO 64093, USAE-mail address: szellers@ucmo.edu.

The Integrated Ocean Drilling Program is considering drilling in the Gulf ofAlaska (GOA), where the interplay among climate, tectonics, and deposi-tion can be examined. A slope site off Kayak Island, sampled by jumbopiston core (EW040885JC), is providing insight into paleoceanographic,depositional, geochemical, and climatic changes across the Pleistocene-Holocene transition, including the Bølling–Alleröd (Bø–Al) warm intervaland the Younger Dryas (YD) cold interval. These intervals were determinedby geochemical analyses, siliceous microfossil distributions, and isotopicanalyses by various researchers. Foraminiferal biofacies also track the Bø–Al and YD intervals. Core EW040885JC contains four intervals with distinctfaunal assemblages. From 1124 to 680 cm core depth, samples consist ofa sandy diamictonwith amixture of outer shelf taxa (Epistominella pacifica,Uvigerina, Cassidulina, Islandiella, and Cibicides), and common Elphidiumclavatum, indicating transport into deep water by ice rafting and/or tur-bidity currents. Planktonic foraminifera are abundant and consist mainlyof Neogloboquadrina pachyderma (sinistral and some dextral) and Globi-gerina bulloides. Two samples from a short interval (680 to 640 cm), cor-responding to the Bø–Al, consist of brown, laminated calcareous oozedominated by benthic taxa (Bolivina and Bulimina) indicative of low oxy-gen and a few planktonic foraminifera. Above this zone (640 to 410 cm) arebioturbated, silty muds with low abundances of Gyroidina, Bolivina, andthe shelf taxa listed above, along with abundant planktic foraminifera (N.pachyderma and G. bulloides), corresponding, in part, to the YD. From 410cm to the top of the core (0 cm), foraminifera are not common, with mudsdominated by abundant radiolarians, diatoms, and sponge spicules. As-semblages show a change from glacially-influenced deposition, to lowoxygen bottom waters, to climatic conditions favoring silica production atthe top.

DEVELOPING ROBUST AGE MODELS FOR LAKE RECORDS: CASE STUDIESFROM CALIFORNIA

Susan R.H. Zimmerman, Tom Guilderson, Tom Brown. Center forAccelerator Mass Spectrometry, Lawrence Livermore National Laboratory,Livermore, CA 94550, USAE-mail address: zimmerman17@llnl.gov.

In recent years, it has become apparent that Earth's climate system isvariable on many scales of time and space, and includes abrupt changesthat have global effects. When attempting to understand the relationshipsof decadal- to centennial-scale variability between sites and depositionalenvironments, a “coarse” agemodel with a handful of ages does not suffice.To better describe patterns of past drought in California, we are estab-lishing robust, high-resolution 14C chronologies for regional lakes rangingfrom 34� to 42� latitude, 540 to 2100 m elevation, and in a variety ofvegetational, hydrological, geochemical, and biological settings. Almost300 radiocarbon dates have been measured on terrestrial and aquaticmacrofossils, as well as bulk sediment – macrofossil pairs. The latter haveyielded no single answer to the meaning of bulk-sediment dates; in a fewinstances, a constant off-set is implied, but in most cases there is no pat-tern, reinforcing the unreliability of bulk sediment dates. As a complementto the radiocarbon measurements, some sediment sequences have alsohad 210Pb, 137Cs, and paleomagnetic secular variation (PSV) measurements,providing independent information to refine the age model.Construction of a robust age model from any set of measured ages requireshonest recognition of uncertainties due to the reliability of individual agesand methods, differences in calendar-year calibration datasets, inter-polation between discretely-dated horizons, and sources of geologicalvariability. Calibration of radiocarbon dates to calendar years requires aninternationally-accepted calibration data-set (e.g, INTCAL-09), and is rel-atively simple to do with programs like Calib and OxCal, but requiresa rigorous propagation of errors which in reality should yield an age en-velope and probability distribution. Several calibration programs containthe ability to include Bayesian statistics (priors) of the calibration curveand construct an age-model with simulated calendar uncertainties. Wepresent examples of various methods for construction of robust, high-precision agemodels, and a picture of past droughts in California emergingfrom our lacustrine records.