Assessing pedogenic calcite stable-isotope values: Can positive linear covariant trends be used to quantify palaeo-evaporation rates?

Ufnar, David F.; Gröcke, Darren R.; Beddows, Patricia A

doi:10.1016/j.chemgeo.2008.07.022

Cited by 37 publications

(27 citation statements)

References 16 publications

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“…The fluid responsible for structural carbonate was either from significantly different diagenetic fluids (not related to surrounding calcite) or represents original body water. We believe that the latter is the most likely explanation, as burial processes would produce negative d 18 O values (Lohmann, 1988), while consumption from multiple sources of fluids, including evaporative systems (Sorensen et al, 2002;Ufnar et al, 2008;Suarez et al, 2009b) and foliage (Koch et al, 1994), will yield positive co-variant trends. The high variability of isotope values illustrates that environmental or biogenic information from fossil bone carbonate cannot be gleaned from a single sample per bone.…”

Section: Stable Isotope Geochemistrymentioning

confidence: 95%

Heterogeneous rare earth element (REE) patterns and concentrations in a fossil bone: Implications for the use of REE in vertebrate taphonomy and fossilization history

Suarez

Macpherson

González

et al. 2010

Geochimica et Cosmochimica Acta

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Section: Stable Isotope Geochemistrymentioning

confidence: 95%

Heterogeneous rare earth element (REE) patterns and concentrations in a fossil bone: Implications for the use of REE in vertebrate taphonomy and fossilization history

Suarez

Macpherson

González

et al. 2010

Geochimica et Cosmochimica Acta

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“…The weak, negative relationship between δ 13 C and δ 18 O values (r = −0.58) negates the possibility that high δ 13 C values (i.e., water stressed vegetation) are associated with evaporative enrichment of soil water in 18 O, a circumstance observed in some lacustrine settings (Ufnar et al, 2008). The most parsimonious explanation of highly enriched δ 13 C signatures of pedogenic carbonates is the presence of C 4 -photosynthesizing biomass.…”

Section: Floramentioning

confidence: 96%

The Early Miocene Critical Zone at Karungu, Western Kenya: An Equatorial, Open Habitat with Few Primate Remains

et al. 2017

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Early Miocene outcrops near Karungu, Western Kenya, preserve a range of fluvio-lacustrine, lowland landscapes that contain abundant fossils of terrestrial and aquatic vertebrates. Primates are notably rare among these remains, although nearby early Miocene strata on Rusinga Island contain a rich assemblage of fossilized catarrhines and strepsirrhines. To explore possible environmental controls on the occurrence of early Miocene primates, we performed a deep-time Critical Zone (DTCZ) reconstruction focused on floodplain paleosols at the Ngira locality in Karungu. We specifically focused on a single stratigraphic unit (NG15), which preserves moderately developed paleosols that contain a microvertebrate fossil assemblage. Although similarities between deposits at Karungu and Rusinga Island are commonly assumed, physical sedimentary processes, vegetative cover, soil hydrology, and some aspects of climate state are notably different between the two areas. Estimates of paleoclimate parameters using paleosol B horizon elemental chemistry and morphologic properties are consistent with seasonal, dry subhumid conditions, occasional waterlogging, and herbaceous vegetation. The reconstructed small mammal community indicates periodic waterlogging and open-canopy conditions. Based on the presence of herbaceous root traces, abundant microcharcoal, and pedogenic carbonates with high stable carbon isotope ratios, we interpret NG15 to have formed under a warm, seasonally dry, open riparian woodland to wooded grassland, in which at least a subset of the vegetation was likely C 4 biomass. Our results, coupled with previous paleoenvironmental interpretations for deposits on Rusinga Island, demonstrate that there was considerable environmental heterogeneity ranging from open to closed habitats in the early Miocene. We hypothesize that the relative paucity of primates at Karungu was driven by their environmental preference for locally abundant closed canopy vegetation, which was likely absent at Karungu, at least during the NG15 interval if not also earlier and later intervals that have not yet been studied in as much detail.

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“…Oxygen and carbon stable isotopic covariation has also been documented in evaporating Dead Sea brines (Stiller et al, 1985), degassing epithermal systems (Zheng, 1990) and laboratory experiments (Ufnar et al, 2008;Abongwa and Atekwana, 2013). Although several hydrological models incorporate evaporative effects in their isotopic determinations (Appelo, 2002;Cappa et al, 2003;Jones et al, 2005;Jones and Imbers, 2010), only one of these models explicitly addresses the coupled effects of evaporation on oxygen and carbon isotope fractionation (Deininger et al, 2012).…”

Section: Evaporation Experimentsmentioning

confidence: 99%

Evaporation induced 18O and 13C enrichment in lake systems: A global perspective on hydrologic balance effects

Horton

Defliese

Tripati

et al. 2016

Quaternary Science Reviews

137

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a b s t r a c tGrowing pressure on sustainable water resource allocation in the context of global development and rapid environmental change demands rigorous knowledge of how regional water cycles change through time. One of the most attractive and widely utilized approaches for gaining this knowledge is the analysis of lake carbonate stable isotopic compositions. However, endogenic carbonate archives are sensitive to a variety of natural processes and conditions leaving isotopic datasets largely underdetermined. As a consequence, isotopic researchers are often required to assume values for multiple parameters, including temperature of carbonate formation or lake water d 18 O, in order to interpret changes in hydrologic conditions. Here, we review and analyze a global compilation of 57 lacustrine dual carbon and oxygen stable isotope records with a topical focus on the effects of shifting hydrologic balance on endogenic carbonate isotopic compositions.Through integration of multiple large datasets we show that lake carbonate d 18 O values and the lake waters from which they are derived are often shifted by >þ10‰ relative to source waters discharging into the lake. The global pattern of d 18 O and d 13 C covariation observed in >70% of the records studied and in several evaporation experiments demonstrates that isotopic fractionations associated with lake water evaporation cause the heavy carbon and oxygen isotope enrichments observed in most lakes and lake carbonate records. Modeled endogenic calcite compositions in isotopic equilibrium with lake source waters further demonstrate that evaporation effects can be extreme even in lake records where d 18 O and d 13 C covariation is absent. Aridisol pedogenic carbonates show similar isotopic responses to evaporation, and the relevance of evaporative modification to paleoclimatic and paleotopographic research using endogenic carbonate proxies are discussed.Recent advances in stable isotope research techniques present unprecedented opportunities to overcome the underdetermined nature of stable isotopic data through integration of multiple isotopic proxies, including dual element 13 C-excess values and clumped isotope temperature estimates. We demonstrate the utility of applying these multi-proxy approaches to the interpretation of paleohydroclimatic conditions in ancient lake systems. Understanding past, present, and future hydroclimatic systems is a global imperative. Significant progress should be expected as these modern research techniques become more widely applied and integrated with traditional stable isotopic proxies.

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Assessing pedogenic calcite stable-isotope values: Can positive linear covariant trends be used to quantify palaeo-evaporation rates?

Cited by 37 publications

References 16 publications

Heterogeneous rare earth element (REE) patterns and concentrations in a fossil bone: Implications for the use of REE in vertebrate taphonomy and fossilization history

Heterogeneous rare earth element (REE) patterns and concentrations in a fossil bone: Implications for the use of REE in vertebrate taphonomy and fossilization history

The Early Miocene Critical Zone at Karungu, Western Kenya: An Equatorial, Open Habitat with Few Primate Remains

Evaporation induced 18O and 13C enrichment in lake systems: A global perspective on hydrologic balance effects

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