The geologic history of seawater oxygen isotopes from marine iron oxides

Science ◽  
2019 ◽  
Vol 365 (6452) ◽  
pp. 469-473 ◽  
Author(s):  
Nir Galili ◽  
Aldo Shemesh ◽  
Ruth Yam ◽  
Irena Brailovsky ◽  
Michal Sela-Adler ◽  
...  
Keyword(s):  
Iron Oxide ◽  
Oxygen Isotope ◽  
Iron Oxides ◽  
Isotope Composition ◽  
Geologic History ◽  
Temperature Dependent ◽  
Oxygen Isotope Fractionation ◽  
History Of ◽  
Sediment Cover

The oxygen isotope composition (δ18O) of marine sedimentary rocks has increased by 10 to 15 per mil since Archean time. Interpretation of this trend is hindered by the dual control of temperature and fluid δ18O on the rocks’ isotopic composition. A new δ18O record in marine iron oxides covering the past ~2000 million years shows a similar secular rise. Iron oxide precipitation experiments reveal a weakly temperature-dependent iron oxide–water oxygen isotope fractionation, suggesting that increasing seawater δ18O over time was the primary cause of the long-term rise in δ18O values of marine precipitates. The18O enrichment may have been driven by an increase in terrestrial sediment cover, a change in the proportion of high- and low-temperature crustal alteration, or a combination of these and other factors.

scholarly journals Oxygen isotope composition of the Phanerozoic ocean and a possible solution to the dolomite problem

2018 ◽  
Vol 115 (26) ◽  
pp. 6602-6607 ◽  
Author(s):  
Uri Ryb ◽  
John M. Eiler
Keyword(s):  
Oxygen Isotope ◽  
Isotope Exchange ◽  
Isotope Composition ◽  
Temporal Variations ◽  
Oxygen Isotope Exchange ◽  
Diagenetic Alteration ◽  
Isotope Studies ◽  
Dolomite Problem ◽  
Clumped Isotope

The18O/16O of calcite fossils increased by ∼8‰ between the Cambrian and present. It has long been controversial whether this change reflects evolution in the δ18O of seawater, or a decrease in ocean temperatures, or greater extents of diagenesis of older strata. Here, we present measurements of the oxygen and ‟clumped” isotope compositions of Phanerozoic dolomites and compare these data with published oxygen isotope studies of carbonate rocks. We show that the δ18O values of dolomites and calcite fossils of similar age overlap one another, suggesting they are controlled by similar processes. Clumped isotope measurements of Cambrian to Pleistocene dolomites imply crystallization temperatures of 15–158 °C and parent waters having δ18OVSMOWvalues from −2 to +12‰. These data are consistent with dolomitization through sediment/rock reaction with seawater and diagenetically modified seawater, over timescales of 100 My, and suggest that, like dolomite, temporal variations of the calcite fossil δ18O record are largely driven by diagenetic alteration. We find no evidence that Phanerozoic seawater was significantly lower in δ18O than preglacial Cenozoic seawater. Thus, the fluxes of oxygen–isotope exchange associated with weathering and hydrothermal alteration reactions have remained stable throughout the Phanerozoic, despite major tectonic, climatic and biologic perturbations. This stability implies that a long-term feedback exists between the global rates of seafloor spreading and weathering. We note that massive dolomites have crystallized in pre-Cenozoic units at temperatures >40 °C. Since Cenozoic platforms generally have not reached such conditions, their thermal immaturity could explain their paucity of dolomites.

scholarly journals Potential Reference Materials for Hematite Oxygen Isotope Analysis

Minerals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 987
Author(s):  
Lianjun Feng ◽  
Hongwei Li ◽  
Tiejun Li
Keyword(s):  
Oxygen Isotope ◽  
Iron Oxides ◽  
Oxygen Isotopes ◽  
Reference Materials ◽  
Isotope Composition ◽  
Isotope Analysis ◽  
Isotope Ratios ◽  
Bulk Rock ◽  
Accurate Analysis ◽  
Oxygen Isotope Ratios

Hematite is a potential mineral for reconstructing the oxygen isotope composition and paleotemperature of paleowater. A highly accurate analysis of oxygen isotopes is essential. However, relative to other oxygenated minerals, we lack hematite reference materials that allow for internationally comparable analyses between different laboratories. To address this issue, we attempted to perform bulk rock oxygen isotope analysis on five hematite reference materials (GBW07223a, GBW07825, YSBC28740-95, YSBC28756-2008, Harvard 92649). Meanwhile, the oxygen isotope ratios of iron oxides (GBW07223a, GBW07825, YSBC28740-95, YSBC28756-2008) were obtained by mass balance involving other oxygen-bearing minerals such as quartz and silicates. In addition, the oxygen isotope ratios of iron oxides in an oolitic hematite (ca. 1.65 billion years ago) are consistent with the results of previous analyses of this class of minerals.

Oxygen isotope composition in Modiolus modiolus aragonite in the context of biological and crystallographic control

2008 ◽  
Vol 72 (2) ◽  
pp. 569-577 ◽  
Author(s):  
M. Cusack ◽  
D. Parkinson ◽  
A. Freer ◽  
A. Pérez-Huerta ◽  
A. E. Fallick ◽  
...  
Keyword(s):  
Biological Control ◽  
Oxygen Isotope ◽  
Environmental Influence ◽  
Isotope Composition ◽  
Seawater Temperature ◽  
Crystal Habit ◽  
Ambient Seawater ◽  
Oxygen Isotope Fractionation ◽  
Modiolus Modiolus ◽  
Horse Mussel

AbstractLiving systems exert exquisite control on all aspects of biomineral production and organic components, including proteins, are essential to this biological control. The protein-rich extrapallial (EP) fluid of bivalve molluscs is a strong candidate for the source of such proteins. Differences in calcium carbonate polymorphs between Modiolus modiolus and Mytilus edulis are concurrent with differences in EP fluid protein profiles. In conjunction with this biological control is the environmental influence which is interpreted using proxies such as δ18O to determine the history of ambient seawater temperature. In the horse mussel, Modiolus modiolus, the difference in oxygen isotope fractionation in the nacreous aragonite and the prismatic aragonite layer results in respective δ18O values of 2.1±0.2% and 2.5±0.2%. These δ18O values result in estimates of ambient seawater of 12.1±0.6°C and 10.2±0.6°C for nacreous and prismatic aragonite, respectively. Electron backscatter diffraction is used here to determine the crystallographic orientation at high spatial resolution, allowing the measurements of stable isotopes to be accurately mapped in terms of shell architecture. These preliminary data suggest that it is essential to account for both polymorph and crystal habit when deciphering ambient seawater temperature using δ18O as a proxy.

Fruit carbonate in Lithospermeae: 14C, stable isotope composition and potential as a paleoenvrionmental proxy

2021 ◽  
Author(s):  
Konstantin Pustovoytov ◽  
Simone Riehl
Keyword(s):  
Oxygen Isotope ◽  
Isotope Composition ◽  
Atmospheric Precipitation ◽  
Warm Season ◽  
Archaeological Sites ◽  
Good Correspondence ◽  
Oxygen Isotope Fractionation ◽  
Air Temperatures ◽  
Cultural Layers ◽  
Diverse Origin

<p>The tribe Lithospermeae (fam. Boraginaceae) represents one of very few taxa vascular plants that accumulate appreciable amounts of calcium carbonate in their tissues. The CaCO<sub>3</sub> is localized in the pericarp sclerenchyma, which makes their small fruits (nutlets) mechanically durable and provides their good preservation in sediments and cultural layers. Fossil Lithospermeae fruits appear as whitish, slightly elongated entities, 3-5 mm in length.  At archaeological sites, the nutlets can be of diverse origin: in most contexts they represent carpological evidence for weed flora of the past, however, some findings suggest that they were used for decorative purposes (beads etc.).  </p><p>Here we overview the potential use of fruit carbonate of Lithospermeae in paleoecological research.   </p><p><sup>14</sup>C-dating: Fruit carbonate of the taxon can be successfully dated with radiocarbon.  </p><p>The <sup>14</sup>C concentration in the CaCO<sub>3</sub> fraction of modern nutlets is well-correlated to the recent atmospheric <sup>14</sup>C levels. Radiocarbon ages of old nutlets are in good correspondence with the age ranges of archaeological contexts. Obviously, fruit carbonate can represent a geochemically closed system for millennia in sediment environments.               </p><p>δ<sup>18</sup>O values: Our data based on an array of herbarium exemplars of Lithospermeae, suggest that the δ<sup>18</sup>O of fruit carbonate is distinctively sensitive to the amount of atmospheric precipitation during the warm season. The degree of correlation between δ<sup>18</sup>O and local air temperatures is lower.</p><p>We further performed an experiment on gromwell (Buglossoides arvensis (L.) I.M.Johnst), irrigated by water with different oxygen isotope signatures. The δ<sup>18</sup>O values of fruit CaCO<sub>3 </sub>showed correlation to the δ<sup>18</sup>O of irrigation water. The oxygen isotope fractionation in fruit carbonate turned out to be surprisingly low with 1000lnα = 4.72±3.49, which is relatively close to foraminiferal CaCO<sub>3</sub>.</p><p> δ<sup>13</sup>C values: In contrast to the oxygen isotope signature, we did not find a strong correlation of the δ<sup>13</sup>C values of fruit carbonate to precipitation and temperature.  However, the photosynthetic origin of carbon in fruit CaCO<sub>3</sub> admits a possibility of some links of δ<sup>13</sup>C to ambient factors.  </p><p>   </p>

scholarly journals Decreasing Indian summer monsoon on the northern Indian sub-continent during the last 180 years: evidence from five tree-ring cellulose oxygen isotope chronologies

2018 ◽  
Vol 14 (5) ◽  
pp. 653-664 ◽  
Author(s):  
Chenxi Xu ◽  
Masaki Sano ◽  
Ashok Priyadarshan Dimri ◽  
Rengaswamy Ramesh ◽  
Takeshi Nakatsuka ◽  
...  
Keyword(s):  
High Resolution ◽  
Oxygen Isotope ◽  
Tree Ring ◽  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
Southern Oscillation ◽  
Oxygen Isotope Fractionation ◽  
Northern India ◽  
Tree Ring Cellulose

Abstract. We have constructed a regional tree-ring cellulose oxygen isotope (δ18O) record for the northern Indian sub-continent based on two new records from northern India and central Nepal and three published records from northwestern India, western Nepal and Bhutan. The record spans the common interval from 1743 to 2008 CE. Correlation analysis reveals that the record is significantly and negatively correlated with the three regional climatic indices: all India rainfall (AIR; r  =  −0.5, p  <  0.001, n  =  138), Indian monsoon index (IMI; r  =  −0.45, p  <  0.001, n  =  51) and the intensity of monsoonal circulation (r  =  −0.42, p  <  0.001, n  =  51). The close relationship between tree-ring cellulose δ18O and the Indian summer monsoon (ISM) can be explained by oxygen isotope fractionation mechanisms. Our results indicate that the regional tree-ring cellulose δ18O record is suitable for reconstructing high-resolution changes in the ISM. The record exhibits significant interannual and long-term variations. Interannual changes are closely related to the El Niño–Southern Oscillation (ENSO), which indicates that the ISM was affected by ENSO in the past. However, the ISM–ENSO relationship was not consistent over time, and it may be partly modulated by Indian Ocean sea surface temperature (SST). Long-term changes in the regional tree-ring δ18O record indicate a possible trend of weakened ISM intensity since 1820. Decreasing ISM activity is also observed in various high-resolution ISM records from southwest China and Southeast Asia, and may be the result of reduced land–ocean thermal contrasts since 1820 CE.

scholarly journals Absence of hydrothermal oxygen isotope variations in host rocks supports magmatic origin of the giant Grängesberg iron oxide–apatite (IOA) deposit, Central Sweden

2021 ◽  
Author(s):  
Franz Weis ◽  
Valentin R. Troll ◽  
Erik Jonsson ◽  
Karin Högdahl ◽  
Chris Harris ◽  
...  
Keyword(s):  
Iron Oxide ◽  
Oxygen Isotope ◽  
Large Scale ◽  
Country Rock ◽  
Isotope Composition ◽  
Northwestern Part ◽  
Magmatic Origin ◽  
Ore Body ◽  
Two Samples ◽  
Host Rocks

AbstractThe origin of Kiruna-type iron oxide–apatite ores is controversial, and debate presently centres on a ‘magmatic’ versus a ‘hydrothermal’ mode of formation. To complement recent investigations on the Grängesberg iron oxide–apatite ore deposit in the northwestern part of the Palaeoproterozoic Bergslagen ore province in central Sweden, we investigated the oxygen isotope composition of the host rocks of this large iron oxide–apatite ore body. As the metavolcanic and metagranitoid country rocks around the Grängesberg ore body either pre-date or are coeval with ore formation, they would be expected to record an extensive isotopic imprint if the ore body had formed by large-scale hydrothermal processes involving an externally sourced fluid. A direct magmatic formation process, in turn, would have produced localized alteration only, concentrated on the immediate vicinity of the ore body. Here, we test these two hypotheses by assessing the oxygen isotope variations in the host rocks around the main Grängesberg iron oxide–apatite ore body. We analysed oxygen isotopes in quartz from metavolcanic (n = 17) and metagranitoid host rocks (n = 14) from the vicinity of the ore body, and up to 2 km distance along and across the strike of the ore body. Remarkably, we find no significant variation in δ18O values with distance from the ore body, or any deviations in country rock δ18O from common magmatic and/or regional values. Only two samples show shifts to values more negative than the common magmatic range, indicating highly localized hydrothermal overprint only. As a large-scale, low-temperature hydrothermal origin of the ore body through voluminous fluid percolation would be expected to have left a distinct imprint on the oxygen isotope values of the country rocks, our results are more consistent with an ortho-magmatic origin for the Grängesberg iron oxide–apatite ore.

scholarly journals Temperature-dependent fractionation of stable oxygen isotopes in otoliths of juvenile cod (Gadus morhua L.)

2004 ◽  
Vol 61 (2) ◽  
pp. 243-251 ◽  
Author(s):  
Hans Høie ◽  
Erling Otterlei ◽  
Arild Folkvord
Keyword(s):  
Ambient Temperature ◽  
Oxygen Isotope ◽  
Oxygen Isotopes ◽  
Gadus Morhua ◽  
Repeated Measurements ◽  
Stable Oxygen Isotopes ◽  
Temperature Dependent ◽  
Oxygen Isotope Fractionation ◽  
Stable Oxygen ◽  
Left And Right

Abstract Analysis of stable oxygen isotopes in otoliths is a promising technique for estimating the ambient temperature experienced by fish, but consistent equations relating temperature and fractionation of stable oxygen isotopes in otoliths among different fish species are lacking. Juvenile cod were reared at constant temperatures from 6 to 20°C and the sagittal otoliths were analysed for oxygen isotope values. We determined that temperature-dependent fractionation of oxygen isotopes in the otoliths was close to that reported for inorganic aragonite at low temperatures, but there were deviations from oxygen isotope fractionation equations for otoliths of other species. The linear relationship between oxygen isotope value in the cod otoliths and temperature was determined to be: 1000 Ln α = 16.75(103 TK−1) − 27.09. Temperature estimates with 1°C precision at the 95% probability level require a sample size of ≥5 otoliths. Only an insignificant amount of the variance in the data was due to variance between left and right otolith, and due to repeated measurements of otolith subsamples. This study confirms that stable isotope values of cod otoliths can give precise and accurate estimates of the ambient temperature experienced by fish.

Long-term shoreline retreat rates on Whidbey Island, Washington, USA

2012 ◽  
Vol 78 (2) ◽  
pp. 315-322 ◽  
Author(s):  
Heather E. Rogers ◽  
Terry W. Swanson ◽  
John O. Stone
Keyword(s):  
Systematic Research ◽  
Shoreline Retreat ◽  
Depositional History ◽  
Exposure Dating ◽  
Large Numbers ◽  
History Of ◽  
Sediment Cover ◽  
Topographic Shielding ◽  
Timing Of Exposure

AbstractLong-term retreat rates of Puget Sound's unconsolidated sediment shorelines have been difficult to quantify, and little systematic research has been completed to constrain retreat in this area. We put forward a new application of cosmogenic 10Be exposure dating to assess long-term shoreline retreat on Whidbey Island, WA by dating lag boulders exposed on the shore platform as the shoreline erodes. Production of 10Be in shoreline boulders is modulated by both tidal submergence and topographic shielding from the retreating bluff. By modeling the combined effect of these variables on 10Be production, the timing of exposure can be determined and used to calculate long-term (103–104 yr) bluff retreat rates. In rare cases, retreat rates are underestimated due to inherited 10Be. Within the study area, average retreat rates ranged between 0 and 8 cm yr− 1. Our results demonstrate the utility of cosmogenic nuclides for determining long-term shoreline retreat rates in areas with thick sediment cover, where large numbers of samples can be collected, and where the pre-depositional history of the boulders is uncomplicated.

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