Stable Isotope Geochemistry

Hoefs, Jochen

doi:10.1007/978-3-662-05406-2

Cited by 384 publications

(339 citation statements)

References 547 publications

(698 reference statements)

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“…The host rock value (δ 13 C = +1.1‰) was typical for a marine carbonate (Hoeffs, 2004) and was isotopically heavier than both the cottonballs (δ 13 C = -8.1‰) and the moonmilk (δ 13 C = -1.6‰). The carbon signatures for the soil organic carbon and leaf litter from the surface were isotopically light (δ 13 C = -24.3 and -25.4 ‰, respectively) as expected for organic matter and C3 vegetation (Sharp, 2007).…”

Section: Geochemistrymentioning

confidence: 96%

Cottonballs, a unique subaqeous moonmilk, and abundant subaerial moonmilk in Cataract Cave, Tongass National Forest, Alaska

Curry¹,

Boston²,

Spilde³

et al. 2009

IJS

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The Tongass National Forest is known for its world-class karst features and contains the largest concentration of dissolutional caves in Alaska. Within these karst systems exist unusual and possibly unique formations exhibiting possible biological origin or influence. Cataract Cave is an example of such a system. This cave hosts a unique depositional setting in which so-called "cottonballs" line two permanent pools. The cottonballs are a calcitic deposit heavily entwined within a mass of microbial filaments. They are juxtaposed with extensive subaerial calcitic moonmilk wall deposit of a more conventional nature but of an extraordinary thickness and abundance. Both the cottonballs and moonmilk are composed of microcrystalline aggregates (0.20 wt.%) compared to the cottonballs (0.12 wt.%). However, the cottonballs are dominated by monocrystalline needles, whereas the moonmilk is mainly composed of polycrystalline needles. The microbial environments of both displayed similar total microbial cell counts; however, culturable microbial counts varied between the deposits and among the various media. For both, in situ cultures and isolates inoculated in a calcium salt medium produced calcium carbonate mineralization within biofilms. Geochemical variations existed between the deposits. Moonmilk displayed a slightly higher abundance of organic carbon (0.20 wt%) compared to the cottonballs (0.12 wt%). Stable isotopic analysis revealed that the moonmilk (δ13C = -1.6‰) was isotopically heavier compared to the cottonballs (δ13C = -8.1‰) but both are lighter than the host rock (δ13C = +1.1‰). However, the organic carbon δ13C values of both deposits were similar (δ13C = -27.4 and -26.7‰) and isotopically lighter compared to other overlying surface organic carbon sources. Due to the similarities between the deposits, we infer that both the cottonballs and moonmilk are subject to a set of related processes that could collectively be accommodated by the term "moonmilk". Thus, the cottonball pool formation can be characterized as a type of subaqueous moonmilk. The differences observed between the moonmilk and cottonballs may be largely attributable to the changes in the depositional environment, namely in air or water.

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Section: Geochemistrymentioning

confidence: 96%

Cottonballs, a unique subaqeous moonmilk, and abundant subaerial moonmilk in Cataract Cave, Tongass National Forest, Alaska

Curry¹,

Boston²,

Spilde³

et al. 2009

IJS

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“…The analyses were carried out by combustion of the samples under a continuous flow of helium in an elemental analyser (Carlo Erba, CHN-1110) coupled to a Thermo Finnigan Delta Plus mass spectrometer. The enrichment or depletion of the 13 C isotopic species was measured against a standard, and expressed in "delta permil" [33].…”

Section: Carbon Isotopes (δ 13 C)mentioning

confidence: 99%

Belowground Carbon and Nitrogen on a Thinned and Un-Thinned Seasonally Dry Tropical Forest

Aquino¹,

Andrade²,

Castanho³

et al. 2017

AJPS

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The aim of this study was to quantify the dynamics of herbaceous biomass and fine root productivity, and their relationship to stocks of carbon and nitrogen, in the Vertisols of two adjacent watersheds of a seasonally dry tropical forest (SDTF) under two different types of ground cover. The two watersheds are located in the county of Iguatu in the State of Ceará, Brazil. The control watershed of 2.1 ha, has been under regeneration for 35 years (RC 35 ), while the second watershed (1.1 ha) was subjected to thinning for a period of 5 years (TC 5 ). The sampled variables were herbaceous shoot biomass, fine roots, gravimetric moisture, the isotope δ 13 C (‰), total soil carbon (TSC) and total nitrogen (TN) in the 0 -20, 20 -40 and 40 -60 cm layers, between April 2013 and March 2014. To quantify herbaceous shoot biomass, samples were taken monthly. For TSC and TN, the campaigns were held every two months. The data underwent analysis of means and were compared by t-test (p < 0.05).Under TC 5 , there was an increase in the stocks of TSC and TN of 151 and 137% respectively in the 40 -60 cm layer, in relation to RC 35 . The implementation of thinning in a SDFT is seen as a management alternative to be considered in sustainability programs in the semi-arid region, contributing to maximising the production of herbaceous forage for feeding large and small ruminants, and for bee pasture, in addition to increasing the stock of carbon in the soil of SDFT and reducing global warming.

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“…At the sediment-water interface and in the uppermost, oxygenated sediments, respiration of organic matter leads to release and formation of 13 C-depleted DIC. With increasing depth below the sediment-water interface, commonly at depths of just a few centimetres, anaerobic conditions develop, which may lead to fermentation of organic matter associated with formation of methane with d 13 C values as low as À60% (Hoefs, 2004). Formation of highly 13 C-depleted methane results in increasing d 13 C of the remaining carbonate phases, usually in the form of HCO À 3 .…”

Section: Isotopic Offsets Between Biogenic Carbonate Componentsmentioning

confidence: 99%

Multi‐component stable isotope records from Late Weichselian and early Holocene lake sediments at Imiołki, Poland: palaeoclimatic and methodological implications

Apolinarska¹,

Hammarlund

2009

J Quaternary Science

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Apolinarska, K. and Hammarlund, D. 2009. Multi-component stable isotope records from Late Weichselian and early Holocene lake sediments at Imiol --ki, Poland: palaeoclimatic and methodological implications.ABSTRACT: Late Weichselian and early Holocene climatic and environmental changes are inferred from stable carbon and oxygen isotope records obtained on bulk and biogenic carbonates from the sediment sequence of Lake Lednica, western Poland. Along with sediment and pollen stratigraphic data, a wide range of carbonate components occurring in the sediments was analysed for d 13 C and d 18 O, including shells of several gastropod species and the bivalve genus Pisidium, carapaces of the ostracod subfamily Candoninae and oogonia of the aquatic macrophyte genus Chara. The development of catchment soils and the onset of authigenic carbonate production in response to the climatic amelioration during the Late Weichselian are clearly reflected by rising carbonate content, distinct isotopic shifts in bulk carbonates and decreasing d 13 C values of bulk organic matter in the sediments. The GI-1/GS-1 (the Bølling-Allerød Interstadial complex/Younger Dryas Stadial) and the GS-1/ Preboreal transitions are marked by significant shifts in d 18 O values of 2-3%, as well as by distinct changes in carbonate content, indicative of a decrease and a subsequent increase in mean annual temperature. Corresponding d 13 C records reflect primarily changes in aquatic productivity, with favourable conditions for phytoplankton and macrophytes during GI-1 and the Preboreal resulting in persistent 13 C enrichment. The Younger Dryas Stadial is characterised by depletions in 13 C and 18 O, with indications of a climatic tripartition. Consistent offsets in d 13 C and d 18 O between records obtained on specific carbonate components reflect vital effects in combination with seasonal characteristics and habitat preferences of the respective carbonate-precipitating biota. Largely parallel first-order variations in d 13 C and d 18 O of the different carbonate components demonstrate that individual isotope records may provide important palaeoclimatic information, although more detailed reconstructions can be obtained from multi-component analysis.

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Stable Isotope Geochemistry

Cited by 384 publications

References 547 publications

Cottonballs, a unique subaqeous moonmilk, and abundant subaerial moonmilk in Cataract Cave, Tongass National Forest, Alaska

Cottonballs, a unique subaqeous moonmilk, and abundant subaerial moonmilk in Cataract Cave, Tongass National Forest, Alaska

Belowground Carbon and Nitrogen on a Thinned and Un-Thinned Seasonally Dry Tropical Forest

Multi‐component stable isotope records from Late Weichselian and early Holocene lake sediments at Imiołki, Poland: palaeoclimatic and methodological implications

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