Rapid onset of ocean anoxia shown by high U and low Mo isotope compositions of sapropel S1

Authigenic uranium isotope compositions of Holocene sapropel S1 (δ238Uauth = +0.10 to +0.52 ‰; ODP core 967, 2550 mbsl) are significantly higher than the proposed upper boundary (+0.2 ‰) associated with the transport-porewater diffusion model for sediment uranium uptake. It is shown that these high δ238Uauth values are compatible with rapid initial slowdown of thermohaline overturning and the development of an anoxic water column. These conditions would favour U uptake in an organic-rich floccule layer overlying the sediment-water interface. The high δ238Uauth values correlate with low δ98Moauth values (+0.02 to −0.88 ‰), interpreted to reflect weakly euxinic conditions controlled by thiomolybdate–molybdate solution equilibria. The S1 data contrast markedly with published data from last interglacial sapropel S5 from the same core, which show δ238Uauth and δ98Moauth characteristics compatible with a restricted euxinic basin due to progressive slowdown in the thermohaline circulation. The U-Mo isotope data for S1 are similar to a range of published palaeo-settings. Sapropels are therefore shown to be useful templates for the unravelling of the interplay between productivity and deep water renewal times in ancient settings

The convolution formula for a decay rate

The convolution formula is derived within the framework of the decay-chain method for decay channels with three and four particles in a final state. To get this formula exactly for unstable particle of any type one must modify the propagators of vector and spinor fields. In this work we suggest proper modifications and get the convolution formula by direct calculation. It was noted that this approach naturally arises in the model of unstable particles with random mass.Comment: 8 pages, typos adde

Early and mid-holocene environmental conditions in the eastern Adriatic recorded in speleothems from Mala Špilja cave and Velika Špilja cave (Mljet island, Croatia)

This study presents high resolutionoxygen and carbon isotopicrecord of two U-Th dated stalagmites from the EasternAdriatic caves. The stalagmites were collected from Mala špiljaand Velika špilja caves situated on Mljet Island in the southernpart of the Croatian Adriatic. Dripwater samples werecollected from Medvjeđa špilja, Strašna peć, Špilja u Vrdolje,Kraljicina spilja, Velika špilja and Mala špilja caves. All cavesformed in well-stratified Cretaceous limestones. The averagevalue of deuterium excess of the dripwater is 9.3 ‰, indicatingthat the atmospheric conditions over the Atlantic Oceanhave greater influence on the isotopic composition precipitationin the Adriatic region than the Eastern MediterraneanSea. The longest isotopic record of the speleothems is of stalagmiteMSM-1 from Mala špilja Cave dated from 119.2±3.3 ka to 5.6±0.6 ka, although deposition was not continuous.During the Holocene the speleothem grew between 7 kaand 4 ka. That interval is characterized by several δ18Oc andδ13Cc fluctuations reflecting changes in the environment. Superimposedon these fluctuations, there is an increasing trendin the 7.0−6.5 ka interval, evident in elevated δ18O values,which primarily refers the trend to drier conditions in theeastern Adriatic, which were occasionally interrupted by wetintervals. Humid conditions are particularly pronounced bylow δ18Oc and δ13Cc values of speleothem MSM-1 between 7.3and 6 ka, as a reflection of increased precipitation and lower temperatures. The transition to today's Mediterranean climate(Cs) occurred between 6 ka and 5 ka, while the driest conditionsare recorded at ~4.7 − 4.2 ka. Comparisons betweenthe eastern Adriatic δ18Oc and δ13Cc records of the speleothemfrom Mala špilja Cave (MSM-1) and Velika špilja Cave (MljetIsland) with Soreq Cave (Israel) and Corchia Cave (Italy) togetherwith other proxies such as lake sediments demonstratethat the speleothems from the Eastern Adriatic caves recordthe local and the regional climatic changes.Key words: Holocene, speleothem; stable isotopes; EasternAdriatic, Croatia.Rekonstrukcija okoljskih razmer vzgodnjem in poznem Holocenu na podlagi zapisa v sigi jamMala Špilja in Velika Špilja (otok Mljet, Hrvaška)Raziskava temelji na visoko ločljivih zapisih kisikovih in ogljikovihizotopov, pridobljenih iz dveh stalagmitov, datiranih zuran-torijevo metodo. Kapnika sta bila vzorčena v jamah Malašpilja in Velika špilja na otoku Mljet, v južnem delu hrvaškegaJadrana. Vzorčena je bila tudi prenikla voda v jamah Medvjeđašpilja, Strašna peć, Špilja u Vrdolje, Kraljicina spilja, Velikašpilja in Mala špilja. Vse omenjene jame so v plastovitem krednemapnencu. Povprečna vrednost presežka devterija v preniklivodi je 9,3 ‰, kar kaže na prevladujoč podnebni vplivAtlantskega oceana v primerjavi z vplivom vzhodnega Sredozemlja.Najdaljši izotopski zapis smo pridobili iz kapnikaMSM-1 iz Male špilje, katerega starost je med 119,2 ±3,3 ka in5,6±0,6 ka. Za kapnik je značilnih več prekinitev izločanja. Vholocenu je kapnik rastel v obdobju med 7 ka in 4 ka. V temobdobju je več izrazitih nihanj δ18Oc in δ13Cc, kar kaže na spremembeokolja. Med 7,0 in 6,5 ka je v zapisu trend naraščanjaδ18O, kar kaže na relativno suhe razmere v vzhodnem Jadranu,ki so jih občasno prekinila vlažna obdobja. Med 7,3 in6 ka je več obdobij z nizkim vrednostmi δ18Oc in δ13Cc v vzorcuMSM-1, kar kaže na veliko padavin in nizke temperature.Prehod v današnjo sredozemsko klimo (Cs) se je zgodil med6 ka in 5 ka, najbolj suha obdobja smo zabeležili med 4,7 kain 4,2 ka. Primerjava izotopskih zapisov δ18Oc on δ13Cc iz Malešpilje (MSM-1) in Velike špilje (Mljet) z zapisi v jami Soreq (Izrael)in v sistemu Corchia (Italija) ter drugimi kazalci nekdanjihokolij, npr. jezerskimi sedimenti, kažejo, da sige vzhodnega Jadrana hranijo pomembne zapise o lokalnih in regionalnihpodnebnih spremembah.Ključne besede: Holocen, siga, stabilni izotopi, vzhodni Jadran,Hrvaška.

Time Delay Effects on Coupled Limit Cycle Oscillators at Hopf Bifurcation

We present a detailed study of the effect of time delay on the collective dynamics of coupled limit cycle oscillators at Hopf bifurcation. For a simple model consisting of just two oscillators with a time delayed coupling, the bifurcation diagram obtained by numerical and analytical solutions shows significant changes in the stability boundaries of the amplitude death, phase locked and incoherent regions. A novel result is the occurrence of amplitude death even in the absence of a frequency mismatch between the two oscillators. Similar results are obtained for an array of N oscillators with a delayed mean field coupling and the regions of such amplitude death in the parameter space of the coupling strength and time delay are quantified. Some general analytic results for the N tending to infinity (thermodynamic) limit are also obtained and the implications of the time delay effects for physical applications are discussed.Comment: 20 aps formatted revtex pages (including 13 PS figures); Minor changes over the previous version; To be published in Physica

Authenticity examination of the inscription on the ossuary attributed to James, brother of Jesus

Abstract A First Century CE ossuary belonging to a private collector, bearing engraved Aramaic inscription ''Ya'akov bar Yosef achui de Yeshua'' (James son of Joseph his brother of Jesus), has been attributed to James, Jesus' brother, first head of the Jerusalem church. The ossuary was reportedly found around Jerusalem. Previous examination suggested that the ossuary and the inscription were genuine. Our research focuses on the authenticity of the patina that covers the inscription (''letters patina''), based on its petrography and oxygen isotopic composition (d O). We compared the d 18 O values of the letters patina from the James Ossuary, with the patina sampled from the uninscribed surfaces of the same item (''surface patina''), and with surface and letters patinas from legally excavated ossuaries from Jerusalem. In addition, the results were compared with d 18 O values of carbonates formed naturally from groundwater in the Judean Mountains. Our results show that the petrography and the d 18 O values of the letters patina of the James Ossuary differ significantly from the other patinas. The oxygen isotopic composition of the letters patina could not have formed under natural temperature and water oxygen isotope composition that prevailed in Judea during the last 3000 years. The patina was most likely artificially formed from powdered chalk immersed in hot water. These observations clearly call into question the authenticity of the inscription on ''James Ossuary''

Interpreting lake isotope records of Holocene environmental change in the Eastern Mediterranean

Oxygen isotope records from lake sediment archives are becoming an increasingly common tool for palaeoenvironmental reconstruction. We discuss their interpretation in the Eastern Mediterranean region with particular reference to three records, Zeribar, Van and Eski Acıgöl during the Holocene. The latter two records have been interpreted as controlled by changes in the precipitation to evaporation ratio, and the first due to changes in precipitation seasonality. In light of recent isotope work in the region and comparison with other proxy data from the same lakes, we show both of these initial interpretations to be oversimplified. Careful interpretations of complex lake isotope systems are therefore required in order that palaeoclimatic inferences are drawn correctly

A 10-fold decline in the Eastern Mediterranean thermocline overturning circulation during the last interglacial period

Present-day Mediterranean deep-waters are well oxygenated, but the episodic formation of organic-rich sediments (sapropels) indicates that this pattern was frequently perturbed in the past. Both high export productivity and disruption of the thermohaline circulation, leading to reduced deep-water ventilation, have been proposed to account for sapropel deposition and anoxia. The last interglacial sapropel S5 is considered one of the most strongly developed. Here, we apply the redox-sensitive Mo and U (elemental and isotope) systems to quantify the intensity of anoxic deep-water conditions in the Eastern Mediterranean Sea from ODP core 967 (2550 mbsl). Both U and Mo show strong authigenic enrichment, coupled to progressive increase in δ98Moauth (+1.2–1.8‰ to +2.0–2.3‰) and decrease in δ238Uauth (+0.10‰ to −0.15‰) from the beginning to the end of S5, suggesting increasing water column euxinia and removal fluxes of Mo and U. Based on modern euxinic basins, we show that sedimentary Uauth can be used to derive estimates of water column U depletion and, ultimately, deep-water renewal rates. These principles are first tested on the modern Black Sea, which yields calculated deep-water renewal times of 830+690/−500 yrs, in good agreement with independent estimates. Applying these principles to the end of S5 suggests bottom-water U depletion of ∼50% and deep-water renewal times of 1030+820/−520 yrs. The significantly slower deep-water renewal rates in the Eastern Mediterranean Sea compared to today (∼100 yrs) would have played an important role in the formation of sapropel S5 and are consistent with the proposed suppression of overturning during the last interglacial, due to increased stratification resulting from higher riverine freshwater input under enhanced monsoon forcing

Tracing water column euxinia in Eastern Mediterranean Sapropels S5 and S7

Sapropels S5 and S7 formed in the semi-enclosed Eastern Mediterranean Sea (EMS) during peak interglacial periods MIS5e and MIS7a, respectively, are considered among the most strongly developed Quaternary sapropels. This study investigates the redox dynamics of the water column during their formation, via Fe isotope and Fe speciation studies of cores taken at 2550 m depth at site ODP-967. Both sapropels show an inverse correlation between δ56Fe and FeT/Al, with slopes mostly matching that found for the Black Sea, pointing to a benthic shelf to basin shuttle of Fe and subsequent precipitation of Fe sulphides in euxinic bottom waters. An exception to these Black Sea-type trends occurs during the later, peak, stages of S7, where the negative δ56Fe - FeT/Al slope shallows. Fe speciation studies reveal that the dominant highly reactive Fe phase (FeHR) in the sapropels is pyrite, with Fe (oxyhydr)oxides forming the second major mineral component. Correspondingly, FeHR/FeT plots show increased strengthening of anoxic water conditions during the passage from pre-sapropel sediment into the sapropel. Nevertheless, despite the evidence for euxinic conditions from both Fe isotopes and high Mo concentrations in the sapropel, Fepy/FeHR ratios remain below values commonly used to identify water column euxinia. This apparent contradiction is ascribed to the sedimentary preservation of a high flux of crystalline Fe (oxyhydr)oxide minerals to the basin, which resulted in a relatively low degree of sulphidation, despite the presence of euxinic bottom waters. Thus, the operationally defined ferruginous/euxinic boundary for EMS sapropels is better placed at Fepy/FeHR = 0.6, which is somewhat below the usually ascribed lower limit of 0.7. Consistent with the significant presence of crystalline Fe (oxyhydr)oxides, the change in the δ56Fe - FeT/Al slope during peak S7 is ascribed to an enhanced monsoon-driven flux of detrital Fe(III) oxides from the River Nile into the EMS basin and comcomitant diagenetic sulphidation. Euxinic water column conditions in sapropel S5 and S7 are interpreted here to reflect the positive balance between dissolved sulphide formation and rates of reductive dissolution of Fe (oxyhydr)oxide minerals. Both of these parameters in turn depend on the extent to which water overturn times are reduced and export productivity increased during sapropel formation

Dynamics of a Limit Cycle Oscillator under Time Delayed Linear and Nonlinear Feedbacks

We study the effects of time delayed linear and nonlinear feedbacks on the dynamics of a single Hopf bifurcation oscillator. Our numerical and analytic investigations reveal a host of complex temporal phenomena such as phase slips, frequency suppression, multiple periodic states and chaos. Such phenomena are frequently observed in the collective behavior of a large number of coupled limit cycle oscillators. Our time delayed feedback model offers a simple paradigm for obtaining and investigating these temporal states in a single oscillator.We construct a detailed bifurcation diagram of the oscillator as a function of the time delay parameter and the driving strengths of the feedback terms. We find some new states in the presence of the quadratic nonlinear feedback term with interesting characteristics like birhythmicity, phase reversals, radial trapping, phase jumps and spiraling patterns in the amplitude space. Our results may find useful applications in physical, chemical or biological systems.Comment: VERSION 4: Fig. 10(d) added, an uncited reference removed; (To appear in Physica D) (17 pages, 21 figures, two column, aps RevTeX); VERSION 3: Revised. In Section 2, small tau approximation added; Section 3 is divided into subsections; periodic solution discussed in detail; Figs. 7 and 11 discarded; Figs. 12 and 14 altered; three new figures (now Figs. 10, 11 and 21) added. VERSION 2: Figs. 1 and 2 replace