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Daily growth and tidal rhythms in Miocene and modern giant clams revealed via ultra-high resolution LA-ICPMS analysis -- A novel methodological approach towards improved sclerochemistry.(Report)

Warter, Viola ; Maaaaaea Ller, Wolfga

Palaeogeography, Palaeoclimatology, Palaeoecology, Jan 1, 2017, Vol.465, p.362 [Rivista Peer Reviewed]

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  • Titolo:
    Daily growth and tidal rhythms in Miocene and modern giant clams revealed via ultra-high resolution LA-ICPMS analysis -- A novel methodological approach towards improved sclerochemistry.(Report)
  • Autore: Warter, Viola ; Maaaaaea Ller, Wolfga
  • Descrizione: To access, purchase, authenticate, or subscribe to the full-text of this article, please visit this link: http://dx.doi.org/10.1016/j.palaeo.2016.03.019 Byline: Viola Warter [viola.warter@rhul.ac.uk] (*), Wolfgang MAaAaAeA ll [w.muller@es.rhul.ac.uk] Keywords Tridacna spp.; Miocene; Daily cycles; Tidal periodicity; Ultra-high resolution LA-ICPMS; Image processing Highlights * A novel methodological approach for ultra-high resolution LA-ICPMS analysis to resolve daily growth in giant clams. * < 10 [micro]m daily variability in B/Ca, Mg/Ca, Sr/Ca and Ba/Ca is resolved in Miocene and modern Tridacna shells. * Longer-term LA-ICPMS records reveal Miocene fortnightly (tidal) and seasonal periodicities. * Image processing analysis indicates a coupling between the geochemical composition and the incremental growth pattern. * LA-ICPMS analysis facilitates rapid acquisition of longer-term (deep-time) palaeoenvironmental records at daily resolution. Abstract We present a novel approach for ultra-high resolution laser-ablation inductively-coupled-plasma mass spectrometry (LA-ICPMS) analysis, which not only allows us to clearly resolve < 10 [mu]m (daily) compositional variability in B/Ca, Mg/Ca, Sr/Ca and Ba/Ca, but also to detect long-term tidal and seasonal cycles in both Miocene and modern Tridacna (giant clam) shells. Daily element/Ca variability preserved within microscopically visible growth increments is resolved by utilizing the combined capabilities of a rotating rectangular aperture (spot size on target 4 x 50 [mu]m), the rapid signal washout of a Laurin two-volume laser ablation cell and slow compositional profiling ([less than or equal to] 1.5 [mu]m/s). Striking co-variation between oscillating cycles in B/Ca, Mg/Ca, Sr/Ca and Ba/Ca is discernible, yet also tantalizingly, sub-daily shifts between these element/Ca ratios can be observed. In comparison to a lower-resolution, seasonally-resolved [delta].sup.18O--Mg/Ca record (Warter et al., 2015), the ~ 10--20 [mu]m element/Ca cycles are determined to be daily in origin, and a further ~ 14--15 day cyclicity is superimposed on the daily cycles. The latter is interpreted to reflect (Miocene) tidal periodicity. Changes in pixel intensity during thin section observation associated with micro- and macroscopically visible low and high density bands have been quantified via image processing analysis. This reveals close correspondence to the measured trace elemental cyclicity, indicating a coupling between the geochemical composition of the shell and the incremental growth pattern. A comparison between the elemental and image processing results reveals that ultra-high-resolution LA-ICPMS analysis surpasses the latter in detecting environmental rhythms, including daily and tidal cycles. Highly-resolved LA-ICPMS analysis is a viable alternative to nanoSIMS and opens up routine investigation of long-term (deep-time) paleoenvironmental records at daily resolution. Author Affiliation: Department of Earth Sciences, Royal Holloway University of London, Egham, Surrey TW20 0EX, United Kingdom * Corresponding author. Article History: Received 3 September 2015; Revised 14 March 2016; Accepted 18 March 2016
  • Fa parte di: Palaeogeography, Palaeoclimatology, Palaeoecology, Jan 1, 2017, Vol.465, p.362
  • Soggetti: Mass Spectrometry – Analysis ; Image Processing – Analysis
  • Lingua: Inglese
  • Identificativo: ISSN: 0031-0182 ; DOI: 10.1016/j.palaeo.2016.03.019
  • Fonte: Cengage Learning, Inc.

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