DOI: 10.25921/zv87-z873
title: NOAA/WDS Paleoclimatology - Santa Barbara Basin Stable Isotope, Geochemistry, and Lithology Data from Marine Isotope Stage 16-15 Boundary at 631.5 ka

description: The Marine Isotope Stage 16-15 boundary (Termination VII) is the first deglacial warming step of the late Quaternary following the mid-Pleistocene transition (MPT), when 41?kyr climatic cycles shifted to strong 100?kyr cycles. The detailed structure of this important climatic event has remained unknown until now. Core MV0508-19JPC from Santa Barbara Basin, California, contains a decadal-scale climatic and geochemical sediment record of 4000?years duration that includes the early part of this deglacial episode. This record reveals that the climatic shift during the early deglacial occurred rapidly (<700?years), in a progression of three abrupt warming steps. The onset of Marine Isotope Stage (MIS) 15 was remarkably abrupt with 4-5°C sea surface warming in ~50?years. The deglacial sequence contains the well-dated Lava Creek tephra (631.3?±?4?ka) from Yellowstone Caldera used to date the onset of Termination VII at 631.5?ka. The late MIS 16 and early MIS 15 interval exhibits multiple decadal-scale negative excursions in d13C of planktic foraminifera, likely the result of repeated discharges of methane from methane hydrates associated with both ocean warming and low sea level. A warm interstadial that interrupts late MIS 16 is marked by elevated concentrations of redox-sensitive elements indicating sulfidic, oxygen-deficient bottom and pore-waters, and elevated concentrations of total organic carbon and Cd, reflecting increased surface productivity. Unlike younger sediments on the California margin, these indicators of increased productivity and low dissolved oxygen do not consistently correspond with each other or with preserved laminations, possibly reflecting instability of a still evolving ocean-atmosphere system following the MPT.

description: Cores
     Core MV0508-19JPC (lat. 34.25042 deg. N; long. 119.76428 deg. W; water depth 135 m; hereafter referred to as "19JPC") is one of a suite of 32 jumbo piston cores ranging in length from 3 to 5.5 m collected in Santa Barbara Basin during a 2005 R/V Melville cruise (MV0508).  These cores sampled progressively older dipping seismic stratigraphic reflectors that crop out across the submerged flank of an actively growing anticline as described by Nicholson et al. (2006), and Marshall (2012).  Many of these cores that date as old as 735 ka exhibit alternating laminated (varved) and massive (bioturbated) sediment. Results of three of these cores (11JPC, ~293 ka), 16JPC (~450 ka), and 20JPC (~735 ka) are reported by Afshar (2011) and White et al. (2013).  Upon recovery, each core was cut into 1.5-m-long sections.  Each section was then run through a GEOTEK Multi-Sensor core logger at 1-cm intervals for measurements of P-wave velocity, magnetic susceptibility, and gamma-ray attenuated porosity, which was calibrated to yield wet bulk density.  Each core section was then cut longitudinally, described, and stored on board under refrigeration.  The 2005 Melville cores are stored in the core repository at Oregon State University,

Dating and Sedimentation Rate
	Approximate ages for 19JPC and other MV0508 cores were first assigned based on their stratigraphic position within a series of well-defined seismic sequence boundaries. The ages of these boundaries were estimated assuming relatively constant sedimentation rates between dated stratigraphic reference horizons that were correlated and mapped across the basin to seafloor outcrops and industry wells using multichannel and high-resolution USGS deep-towed chirp data (Nicholson et al., 2006; Marshall, 2012). These preliminary ages were later refined by correlating glacial-interglacial patterns in the oxygen-isotope records of the surface-dwelling planktic foraminifer Globigerina bulloides of each core with the "LR04" stacked global benthic oxygen isotope record of Lisiecki and Raymo (2005).  Additional age control was provided by diatom, coccolith and planktic foraminiferal biostratigraphic datums (Afshar, 2011; White et al., 2013). By this method, the glacial-interglacial oxygen-isotope transition in core 19JPC at 105 cm was correlated with the MIS 16-MIS 15 boundary in the stacked benthic record of Lisiecki and Raymo (2005). This boundary, also known as Termination VII, marks the first time during the Quaternary that global climate transitioned from extremely cold glacial climate and low sea-levels (high δ18O; MIS 16) to warm conditions and high sea levels of a following interglacial (low δ18O; MIS 15). 
	A linear sedimentation rate through the core was estimated using varve thickness measurements.  Digital images (grayscale) of scraped split faces of each core section were acquired using a line scanner mounted on a multi-sensor track at Oregon State University core repository.  The images were analyzed using NIH Image J software to determine an average linear sedimentation rate by counting laminations within minimally disturbed intervals using grayscale contrast of the light-dark couplets (Escobedo, 2009), assuming that these are annual layers, i.e., varves, as demonstrated by Schimmelmann et al. (2006) for younger sediment in SBB.  Core 19JPC is only intermittently laminated, so Escobedo (2009) counted the laminations in three distinctly laminated sections of 19JPC and determined sedimentation rates of 76 cm/kyr (at 231 cm), 120 cm/kyr (at 303 cm), and 94 cm/kyr (at 305 cm), with an average of 97 cm/kyr for the 4-kyr interval recorded in 19JPC . Varve counts were also made on two nearby cores (Fig. 1A) with more abundant laminations, 11JPC (~293ka; 80 cm/kyr) and 20JPC (~735 ka; 82 cm/kyr) (Escobedo; 2009), yielding similar sedimentation rates; these are all consistent with bathyal sedimentation rates (about 100 cm/kyr) determined in other SBB investigations based on biostratigraphy, oxygen isotope stratigraphy, tephrochronology, and seismic stratigraphy (Nicholson et al., 2006; Behl et al., 2007; Marshall, 2012; White et al., 2013).

 Carbon Analyses 
A total of 181 samples were analyzed for weight percentages of total carbon (TC) and total inorganic carbon (IC) using a carbon-dioxide coulometer (Engleman et al., 1985) in the laboratories of California State University, Long Beach, CA (CSULB).  For details of the method used at CSULB, see Afshar (2011).  Percent total organic carbon (TOC) was calculated as the difference (TC – TIC).  Percent CaCO3 was calculated as 
	CaCO3 = IC/0.12,
where 0.12 is the weight fraction of carbon in CaCO3.  The accuracy for both TOC and CaCO3, determined by comparison with standards is ±0.58 wt. %; the precision of TOC and CaCO3 are ±0.05 wt. % and ±0.47 wt. %, respectively (Afshar, 2011).

Oxygen and Carbon Isotopes
Stable-isotope analyses of oxygen and carbon were made on 406 samples, including duplicates, of the surface-dwelling planktic foraminifer Globigerina bulloides collected from 19JPC at 1-cm intervals.  Limited intervals of special interest were also analyzed for the isotopic composition of other species to characterize different depths in the water column. Between 5 and 15 foraminifera were picked for each stable isotopic analysis, which was performed on a Finnegan MAT 251 mass spectrometer in the isotope laboratory at the University of California, Santa Barbara following standard preparation techniques. Instrumental precision was <0.09 ‰ for both isotopes; all data are expressed as standard delta notation in per mil (‰) relative to the Vienna Pee Dee Belemnite (VPDB) standard as related to repeated analysis of NBS-19 and NBS-20 (Coplen, 1997):
δ ‰=[(Rsample/RVPDB)−1]×103 
where R is the ratio (13C: 12C) or (18O: 16O). 

Inorganic Geochemistry
	A total of 116 samples from 11JPC, 97 samples fro 20JPC, and 112 samples from 19JPC were analyzed for 40 major, minor, and trace elements by a combination of inductively coupled plasma optical emission spectrometry (ICP-OES) and ICP mass spectrometry (ICP-MS) at SGS Minerals Services in Toronto, Canada.  Samples were digested in a sequential acid leach with HNO3, HCl, HF, and HClO4 and heated until dry.  The residue was then dissolved in HNO3 and HCl. Accuracy of the ICP-MS method was determined by what SGS calls a Measurement Uncertainty (MU) for each element at various concentration ranges.  The estimated MU is assessed using the reference material uncertainty from the certificate of analysis, the uncertainty of the laboratory bias, the uncertainty of the long-term contribution, and the uncertainty from the precision of replicate samples or duplicate samples for a period of greater than three months.   The MU is the relative percent of the amount present.  For Mo in 19JPC in the range of 1-3 ppm the MU is 10.1% so for a sample containing 2 ppm Mo, the uncertainty is 2±0.20 ppm.  For U in the range of 1-10 ppm the MU is 16.6% so for a sample containing 5 ppm U, the uncertainty is 5±0.83 ppm. For all 40 elements in the 19JPC data set, the average MU is 15.4%, ranging from 7.1% (Ca) to 32.1% (Cu).  For the precision of this data set, the average percent difference between duplicate analyses for each element was 3.1% (range: 0-3.9%). 


references for methods:

Afshar, D.S., 2011, High-resolution windows into abrupt and millennial-scale changes in climate and ocean since the mid-Pleistocene transition, Santa Barbara Basin, California.  MS Thesis, California State University, Long Beach, 134 p.
Behl, R. J., Escobedo, D. K., Kennett, J. P., Nicholson, C., and Sorlien, C. C., 2007, Decadal to Million-Year Sedimentation Rates and the Ultra-High-Resolution Marine Record From Santa Barbara Basin. . Eos Trans. AGU, 88(52), Jt. Assem.. Suppl., Abstract PP41C-0677.
Coplen, T.B., 1997, Editorial: More uncertainty than necessary, Paleoceanography, 11, 369-370.
Engleman, E.E., Jackson, L.L., Norton, D.R., Fischer, A.G., 1985, Determination of carbonate carbon in geological materials by coulometric titration, Chem. Geol., 53, 125-128.
Escobedo, D.K., 2009, Extreme erosional events recorded by flood deposits in the Late Quaternary Santa Barbara Basin, coastal southern California, MS Thesis, California State University, Long Beach, 101 p.
Lisiecki, L.E., and Raymo, M. E., 2005 A Pliocene-Pleistocene stack of 57 globally distributed benthic 18O records,  Paleoceanography , 20, PA1003, doi:10.1029/2004PA001071.
Marshall, C. J., 2012, Sedimentation in an active fold and thrust belt, from 1 Ma to present, Santa Barbara Channel, California, MS Thesis, California State University, Long Beach, 94 p.
Nicholson, C., Kennett, J., Sorlien,C., Hopkins, S., Behl, R., Normark, SW., Sliter, R., Hill, T., Pak, D., Schimmelmann, A., and Cannariato, K., 2006, Santa Barbara Basin study extends global climate record, EOS (Trans. Am. Geophys. Union), 87, n. 21, 205, 208.
Schimmelmann, A., Lange, C. B., Roark, E. B., and Ingram, B. L., 2006, Resources for paleoceanographic and paleoclimatic analysis: A 6, 700-year stratigraphy and regional radiocarbon reservoir-age (AR) record based on varve counting and C-14-AMS dating for the Santa Barbara Basin, offshore California, USA, J. Sed. Res., 76, 74-80
White, S.M., Hill, T. M., Kennett, J. P., Behl, R. J., and Nicholson, C., 2013, Millennial-scale variability to 735 ka:  High-resolution climate records from Santa Barbara Basin, CA,  Paleoceanography, 28, 213-226, doi: 10.1002/palo.20022.