The luminescent humic substances in speleothems

Smailer, Steven M.; White, William Β.

doi:10.1016/j.apgeochem.2013.06.002

Cited by 6 publications

(4 citation statements)

References 22 publications

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“…This fabric is referred to as columnar open (Frisia and Borsato, 2010). Under epifluorescence, white inclusion-rich bands fluoresce green to bright yellow indicating the presence of variable amounts of colloidal organic matter (cf: McGarry and Baker, 2000;van Beynen et al, 2001;Smailer and White, 2013), whereas dense translucent bands are nonfluorescent or are mottled dully fluorescent (Fig. 3d).…”

Section: Macroscopic and Microscopic Fabricsmentioning

confidence: 98%

Stalagmite records of hydroclimate in central California during termination 1

Oster

Montañez

Santare

et al. 2015

Quaternary Science Reviews

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a b s t r a c tThe last deglaciation is marked by large and abrupt hydroclimatic changes in the Great Basin and the American Southwest. However, comparatively little is known about how hydroclimate varied on the western side of the Sierra Nevada. We present new evidence for abrupt changes in precipitation amount in the central Sierra Nevada during the last deglaciation. Our new record from McLean's Cave overlaps with a previously published record from nearby Moaning Cave (Oster et al., 2009), and extends the record of hydroclimatic change in the region through Heinrich Stadial 1. McLean's Cave speleothem d 18 O, d 13 C, Mg/Ca, and Sr/Ca indicate a shift to drier conditions at the beginning of Heinrich Stadial 1 from 16.1to 17.5 ka followed by wetter conditions at the end of Heinrich Stadial 1 when the majority of Great Basin lakes reached their deglacial highstands. During the last deglaciation, coincident shifts in the Moaning and McLean's Cave proxy records indicate drier conditions in the western Sierra Nevada during millennial-scale intervals of warming at high latitudes such as the B€ olling and Aller€ od, and wetter conditions during cooler intervals such as the Older and Younger Dryas. Thus, the Sierra Nevada speleothem records are consistent with other regional records that document increased winter rainfall during millennial-scale cold periods of the last deglaciation. However, regional differences exist in the hydroclimatic response to the Younger Dryas, with central Californian and interior southwestern sites indicating an increase in winter storms that is not apparent in southern California. Dynamic simulations of atmospheric circulation indicate that wetter conditions during the Younger Dryas relative to the B€ olling at McLean's Cave may have resulted from a stronger storm track in the north Pacific at the latitude of northern California.

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Section: Macroscopic and Microscopic Fabricsmentioning

confidence: 98%

Stalagmite records of hydroclimate in central California during termination 1

Oster

Montañez

Santare

et al. 2015

Quaternary Science Reviews

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“…Baker & Genty, 1999;McGarry & Baker, 2000); however, current organic carbon quantification procedures need to be improved before speleothems can be used as high-resolution records of carbon flux, which are a major issue in the climate change context (Ciais et al, 2013). In fact, carbon measurement procedures described in the literature are either quantitative but low-resolution destructive methods Hartland et al, 2014;Li et al, 2014;Ramseyer et al, 1997;Smailer & White 2013;Van Beynen et al, 2001) or semi-quantitative but high-resolution spectroscopic methods (Baker et al, 1996;Baker et al, 1997). Spectroscopic techniques have also been used to determine the organic carbon concentrations of karst waters (Charlier et al, 2010;Tissier et al, 2013).…”

Section: Accepted Manuscriptmentioning

confidence: 98%

Geochemical mapping of organic carbon in stalagmites using liquid-phase and solid-phase fluorescence

et al. 2015

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“…During calcite crystal growth, many components of the aqueous fluid adsorb to the mineral surface and can be entrapped or incorporated into the mineral at trace to minor concentrations (Watson, 2004) in such a way as to potentially provide a record of the environmental conditions and solution composition at the time of crystallization (e.g., Borsato et al, 2007;Blythe et al 2008;Fairchild and Treble, 2009;Perrette et al, 2005). Among the impurities in calcite precipitated in low-temperature environments are large organic molecules, such as humic and fulvic acids (Neuweiler et al, 2000;Smailer and White, 2013), lipids (Pearson et al, 2005;Blyth et al, 2011), and amino acids (Walton, 1998;Penkman et al, 2008), that cannot be incorporated in calcite by simple substitution. Such organic molecules could be useful for extracting paleoenvironmental information if they are incorporated in the calcite crystals at the time of deposition and remain impervious to removal or replacement over geological timescales.…”

Section: 0 Introductionmentioning

confidence: 99%

NMR spectroscopic study of organic phosphate esters coprecipitated with calcite

Phillips

Zhang

Kubista

et al. 2016

Geochimica et Cosmochimica Acta

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Organic phosphorus incorporated in calcite during laboratory precipitation experiments and in natural cave deposits was investigated by solid-state NMR spectroscopy. For calcite precipitated in the presence of organic phosphoesters of varying size and functionality, solid-state 31 P{ 1 H} CP/MAS NMR shows that the phosphoesters were incorporated intact into the solid. Systematic changes in the 31 P NMR chemical shift of the phosphate group were observed between the solid phosphoester and that incorporated in the solid precipitate, yielding 31 P NMR chemical shifts of the coprecipitates in the range of +1.8 to -2.2 ppm.These chemical shifts are distinct from that of similarly prepared calcite coprecipitated with inorganic phosphate, 3.5 ppm. Only minor changes were noted in the phosphoester 31 P chemical shift anisotropy (CSA) which suggests no significant change in the local structure of the phosphate group, which is dominated by C-O-P bonding. Close spatial proximity of the organic phosphate group to calcite structural components was revealed by 31 P/ 13 C rotational echo double resonance (REDOR) experiments for coprecipitates prepared with 13 C-labeled carbonate. All coprecipitates showed significant 31 P dephasing effects upon 13 C-irradiation, signaling atomic-scale proximity to carbonate carbon. The dephasing rate for smaller organophosphate molecules is similar to that observed for inorganic phosphate, whereas much slower dephasing was observed for larger molecules having long and/or bulky side-chains. This result suggests that small organic molecules can be tightly enclosed within the calcite structure, whereas significant structural disruption required to accommodate the larger organic molecules leads to longer phosphate-carbonate distances. Comparison of 31 P NMR spectroscopic data from the synthetic coprecipitates with those from calcite moonmilk speleothems indicates that phosphorus occurs mainly as inorganic orthophosphate in the natural deposits, although small signals occur with characteristics consistent with phosphate monoesters. The results of this study indicate that trace-to minor concentrations of dissolved organic molecules can be effectively taken up during calcite precipitation and incorporated in the structure, leaving a resilient record of materials present during crystallization.

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The luminescent humic substances in speleothems

Cited by 6 publications

References 22 publications

Stalagmite records of hydroclimate in central California during termination 1

Stalagmite records of hydroclimate in central California during termination 1

Geochemical mapping of organic carbon in stalagmites using liquid-phase and solid-phase fluorescence

NMR spectroscopic study of organic phosphate esters coprecipitated with calcite

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