Ir Anomalies Research Articles

A new technique for measuring Ir concentrations via ICP-MS

Impact ejecta deposits have the potential for being ideal stratigraphic markers. Identifying impact horizons, however, is done by the identification of shock-metamorphic minerals. However, such work is time consuming, often requiring searching through hundreds of grains, and is therefore not feasible when searching through extensive stratigraphic sections. Alternatively, impact horizons are frequently identified by the presence of Ir anomalies. This is typically done through either Ni Fire Assay and column chemistry or by Instrumental Neutron Activation Analyses. Both of which are time consuming and/or require specialized training. Here we present results of our new technique for measuring Ir without Fire Assay or INAA. ~90 mg of sample is dissolved in HF + Nitric followed by a mixture of HCl and Nitric. Analyses are conducted on a quadrupole mass spectrometer, using Indium to correct for instrumental drift and standard addition to avoid matrix complication. We have tested this technique with a mix of both Cody Shale doped with known amounts of Ir and with naturally Ir-rich samples. This technique is capable of identifying anomalies as low as ~1 ppb. While other geochemical techniques can provide more precise concentrations, particularly at lower concentration, the ease of this technique is well suited as a first-pass screening tool for identifying impact horizons in large stratigraphic sections.

Correction to: Investigation of Spatiotemporal Satellite Thermal IR Anomalies Associated with the Awaran Earthquake (Sep 24, 2013; M 7.7), Pakistan

Due to an unfortunate oversight the author name “Nabeel Ahamd” has been misspelt. It should be read: “Nabeel Ahmad”.

40Ar-39Ar step heating ages of North American tektites and of impact melt rock samples from the Chesapeake Bay impact structure

Abstract This study presents 40Ar-39Ar step heating ages of four North American tektites (three bediasites and one georgiaite) and of two groundmass samples extracted at different depths from clast-rich impact melt rocks (CB-W61 and CB-W84) recovered by the USGS-ICDP Eyreville B drill-core about 9 km from the centre of the Chesapeake Bay impact structure. Radiometric age determination on both North American tektites and impact melt rocks from within Chesapeake Bay crater offers the first possibility to confirm the origin of these tektites. For this aim, argon isotopic data from 13 samples/aliquots of tektite rims, cores and bulk, and 4 samples/aliquots from two impact melt rocks were obtained over 15 to 26 step heating extractions. Age spectra of all tektite samples show plateaux comprising 62–98% of the 39Ar release over consecutive intermediate and high temperature heating steps. Few low temperature extractions indicate excess 40Ar. Inverse isochron 40Ar/36Ar intercepts of tektite samples are indistinguishable from air (295.5). However, impact melt rock spectra presented complex Ar-release affecting primarily the low temperature heating-steps. Inverse isochrones indicate excess argon from which the 40Ar/36Ar intercept was used to correct the age calculation. CB-W61 and CB-W61-2 40Ar/36Ar intercepts are 354.5 ± 2.5 and 327.2 ± 6.3, respectively, and those for CB-W84 and CB-W84-2 are 332.0 ± 7.3 and 329.6 ± 5.6, respectively. The inverse isochron weighted mean age (according to currently suggested K-decay constants revisions by Schwarz et al. (2011) and Renne et al. (2011)) for all four tektites is 34.86 ± 0.25 Ma (MSWD = 0.96, P = 0.41; n = 4) and for the two impact melt rocks is 37.16 ± 3.65 Ma (MSWD = 0.83, P = 0.36). The combined tektite and impact melt rocks isochron mean age of 34.86 ± 0.23 (0.32) Ma (MSWD = 0.87, P = 0.43) is slightly – though not significantly – higher than the plateau mean age of 34.55 ± 0.27 (0.36) Ma (MSWD = 0.66, P = 0.62). Placing this age in the Global Stratotype Section and Point (GSSP) marine section exposed at Massignano, Italy, it falls below the Eocene/Oligocene (E/O) boundary overlapping with the 10.28 m Ir-anomaly. These results agree within errors with previously reported ages of 35.20 ± 0.54 Ma, especially those derived from K-Ar and Ar-Ar total fusion analysis. An age of 34.86 ± 0.32 Ma sets the Chesapeake Bay impact event close to the youngest of the three Ir anomalies at ∼35.0 Ma in the case the impactor was Ir-rich (e.g, a chondrite, primitive achondrite, stony-iron or iron meteorite). The concordance with the E/O boundary at ∼33.9 Ma seems only marginally possible, and only if the Ir contribution from the ejecta were, potentially, due either to its small amount becoming diluted in the geologic record or the impactor being Ir poor, e.g., of differentiated achondritic composition. This study also brings to front the need to re-establish the stratigraphic and palaeo-magnetic correlations across the globe for the Ir-anomalies and the magneto-stratigraphy during the mid- to late-Eocene and early-Oligocene, and the need to re-evaluate the markers for the Eocene-Oligocene boundary.

Investigation of Spatio-temporal Satellite Thermal IR Anomalies Associated with the Awaran Earthquake (Sep 24, 2013; M 7.7), Pakistan

The reliable forecast of imminent future earthquakes is still questionable due to uncertainties regarding the complex phenomena of earthquake occurrence and the hierarchical nature of the lithosphere. However, numerous retrospective studies suggest the implications of earthquake-accompanying processes within the context of earthquake forecasting. In this connection, an attempt is made here to verify the enhancement in thermal IR emissions associated with the extraordinary major (M 7.7) and shallow (depth ≈ 15 km) Awaran earthquake (Sep 24, 2013). The satellite thermal imagery record is analyzed to identify the possible effect of pre- and post-seismic changes around the epicentral region (latitude 25–29°N; longitude 63–67°E) for a suitable selected time window (July 27, 2013 to Nov 16, 2013). The pre-earthquake satellite imagery records reveal a very clear and distinct thermal anomaly developed within the earthquake preparation zone almost 6–10 days earlier, while the analysis of post-earthquake imagery record shows a decreasing trend of thermal anomaly as a function of time. The daily land surface temperature (LST) shows an anomalous rise of 7–9 °C on Sep 18, 2013, almost 6 days prior to the event occurrence, which is further authenticated by the statistical criterion $$(\bar{x} \pm 2\sigma )$$ with a confidence interval of 95%. Furthermore, the comparative and percentile analysis of daily and 5-year-averaged LST also exhibits abnormal increase associated with this particular event. In addition to all above, the present study is also consistent with the earlier findings and suggests a multi-precursory strategy for earthquake forecasting research.

Geochemical characteristics of newly discovered Elongatoolithidae eggs from the Upper Cretaceous of Jiangxi Province, southern China: Palaeoenvironmental and palaeoclimatic inferences

We analyzed identified oospecies and associated geochemical characteristics of newly discovered dinosaur eggs from the Cretaceous Hekou Formation in Yudu District, Jiangxi Province, China. Results reveal that the Yudu eggs can be identified as representatives of the known oospecies Macroolithus rugustus within Elongatoolithidae based on external shape, size, ornamentation, and internal microstructure between the columnar and cone layers. The major element found in Macroolithus rugustus shells is Ca, while trace elements mainly include Sr, Ba, As, Cr, Mn, Pb, Cd, La, and Ir, characterised by Ir and Sr abnormalities, as well as the toxic elements As and Pb. Enrichment of trace elements in shells might be due to the diet of dinosaurs and subsequent deposition in eggs, consistent with global Ir anomalies and the regional enrichment of trace elements. δ13C values for Macroolithus rugustus ranging between −8.81‰ and −7.65‰ are indicative of C3 plants with relatively high CO2 concentration and low mean annual precipitation (MAP), while δ18O values ranging between −8.51‰ and 3.14‰ indicate relatively low humidity and the alteration of water sources of female dinosaur. The Sr and Ca contents as well as δ18O values of eggshells could be associated with the drinking water and food materials together with dissolved bone apatite. In light of the red-brown colour of surrounding rocks, high Fe composition revealed by macroelement analysis, and the presence of a C3 vegetation with low MAP, the palaeoenvironment of Yudu dinosaur nesting area was most likely to be fluvial and the palaeoclimate was semi-arid to arid, which is conducive to the preservation of eggs.

Discriminating satellite IR anomalies associated with the MS 7.1 Yushu earthquake in China

In the process of exploring pre-earthquake thermal anomalies using satellite infrared data, Blackett et al. (2011) found that the previously reported anomalies before the 2001 Mw 7.7 Gujarat earthquake, in India, were related to positive biases caused by data gaps due to cloud cover and mosaicing of neighboring orbits of MODIS satellite data. They supposed that such effects could also be responsible for other cases. We noted a strip-shaped TIR anomaly on March 17th, 2010, 28 days before the Ms. 7.1 Yushu earthquake (Qin et al., 2011). Here we again investigate multi-year infrared satellite data in different bands to discriminate whether the anomaly is associated with the earthquake, or is only bias caused by the data gaps. From the water vapor images, we find lots of clouds that have TIR anomalies. However, on the cloudiness background, there is an obvious strip-shaped gap matching the tectonic faults almost perfectly. In particular, the animation loops of hourly water vapor images show that the cloud kept moving from west to east, while they never covered the strip-shaped gap. We consider that the cloud with this special spatial pattern should have implied the abnormal signals associated with the seismogenic process. Based on current physical models, the satellite IR anomalies both on TIR and water vapor bands can qualitatively be explained using synthetic mechanisms.

Satellite thermal IR and atmospheric radon anomalies associated with the Haripur earthquake (Oct 2010; Mw 5.2), Pakistan

The recent scientific progress in the context of earthquake forecasting reveals some key physical processes related to seismic activity. The lithosphere–atmosphere–ionosphere coupling model provides a comprehensive mechanism to understand the underlying key physical processes. In this study, a precursory analysis was conducted for the shallow, moderate-magnitude Haripur earthquake (Oct 2010; Mw 5.2) bounded by two major water reservoirs, highlighting its significance. This precursory analysis was performed using the land surface temperature (LST) extracted from satellite (MODIS) thermal infrared data and atmospheric radon concentration recorded at Islamabad and Murree stations using radon monitors. A significant change in LST (4–8°C) was observed in the epicentral region 6 days prior to this event. In addition, a comparison was made between daily and five-year-averaged LST that further supports our results. The radon concentration also showed anomalous behavior 3–4 days prior to this particular event with crucial meteorological indicators in the safe limit. This abnormal behavior of both precursors prior to this event proposes a possible correlation with the local seismic activity. Moreover, the higher amplitude of radon anomaly at the nearest station (Islamabad) is also validating its local cause. The results presented in this study are very encouraging and stimulate the idea of earthquake forecasting using multi-precursory approach.

Dinosaur extinction and subsequent mammalian recovery during the Cretaceous-Paleogene (K/Pg) transition in the Nanxiong Basin

Geochemical analysis of the vertebrate fossils (dinosaur eggshell fragments and chelonian bones) from the K/Pg boundary section exposed in the Nanxiong Basin, Guangdong Province, South China shows that at least three geochemical environmental events, marked by Ir anomalies, took place during the latest Cretaceous (Maastrichtian) and early Paleocene. The first geochemical environmental event occurred at about 67 Ma. In this event dinosaur diversity was hardly reduced, although it appears to have led to an increased incidence of eggshell pathology. The second event was larger, and occurred at or near the pollen-defined K/Pg boundary interval. Enrichment of other trace elements, such as Cr, Ni, Co, Zn, Pb, Cu, Mn and V, within the eggshells occurs mostly at and near the interval, and eggshells in this stratigraphic zone also show positive oxygen-18 excursions and anomalies in thickness and microstructure. Abundant Ir and other trace elements in the dinosaur eggshells reflect changes in their original mineral composition that took place before fossilization began. The anomalously abundant elements were taken into the dinosaurs’ bodies in food, and then passed into their eggs. This process would have affected the normal physiological functioning of the dinosaurian body, as well as causing the observed eggshell pathologies. The extinction of the dinosaurs in the Nanxiong Basin did not occur instantaneously, but was spread out within 250 ka with major extinction beginning at the boundary interval. The cause may have been environmental poisoning and adverse climatic changes, as indicated by geochemical analyses of the dinosaur eggshells. Through the food chain, trace elements were taken into the dinosaurian body in excessive amounts, causing imbalances in trace element levels. This affected the dinosaurs’ reproduction, leading to the formation of pathologic eggshells. The eggshells became so brittle that they failed to protect the developing embryos, contributing to the extinction of the dinosaurs. The third geochemical environmental event occurred in the early-middle Paleocene, the time interval represented by the bottom layer of the Shanghu Formation. This event may have significantly delayed the full recovery of non-marine ecosystems and mammals after the dinosaur extinction. The stepwise extinction and the Paleocene mammalian recovery observed in the Nanxiong Basin nearly coincide with the duration of the Deccan volcanism seen in India. Recent advances in Deccan volcanic studies indicate that the volcanic eruptions occurred in a series of rapid pulses, grouped into three main phases. The initial set of eruptions, phase 1, occurred at ~67.4 Ma. This phase accounts for only about 6% of the total volume of the Deccan Traps, probably because the eruptions were less intense in this phase than in the later ones. Phase 2 included the largest eruptions, took place prior to the K/Pg boundary, and accounts for ~80% of the total volume of the Deccan Traps. Phase 3 began in the early Danian, or about 270 ka after the K/Pg boundary, and accounts for ~14% of the total volume of the Deccan traps. Therefore, it seems likely that the K/Pg events that occurred in the Nanxiong Basin can be explained in terms of the effects of the Deccan volcanism on an already stressed biosphere.

Late Eocene 3He and Ir anomalies associated with ordinary chondritic spinels

During the late Eocene there was an enigmatic enhancement in the flux of extraterrestrial material to Earth. Evidence comes from sedimentary 3He records indicating an increased flux of interplanetary dust during ca. 2Myr, as well as two very large impact structures, Popigai (100km diameter) and Chesapeake Bay (40–85km), that formed within 10–20kyr at the peak of the 3He delivery. The Massignano section in Italy has one of the best sedimentary records of these events, including a well-defined 3He record, an Ir-rich ejecta bed related to the Popigai impact event, and two smaller Ir anomalies. Recently we showed that the Popigai ejecta is associated with a significant enrichment of chromite grains (>63μm) with an H-chondritic elemental composition (17 grains in 100kg of rock). Most likely these grains are unmelted fragments from the impactor. Slightly higher up (ca. 20cm) in the section, where a small Ir anomaly possibly related to the Chesapeake Bay impact has been measured, we found a weak enrichment in L-chondritic grains (8 grains in 208kg of rock). Here we report an extended data set increasing the total amount of sediment dissolved in acid and searched for extraterrestrial chromite grains from 658 to 1168kg. In altogether 760kg of background sediment from 17 levels over 14m of strata outside the interval corresponding to the Popigai and Chesapeake Bay impacts, we only found 2 extraterrestrial chromite grains. Both grains have L-chondritic compositions and were found in a 100kg sample from the ca. 10.25m level in the section where the second of the smaller Ir anomalies has been reported. A correlation appears to exist between Ir, 3He and chromite from ordinary chondrites. We also report oxygen three-isotope measurements of the extraterrestrial chromite grains associated with the Popigai ejecta and confirm an H-chondritic composition.The new results strengthen our scenario that the upper Eocene 3He and Ir enrichments originate from the asteroid belt rather than the Oort cloud as originally proposed when the 3He anomaly was discovered. The generally low background concentrations of extraterrestrial chromite through the section speak against any major single asteroid breakup event such as in the mid-Ordovician after the break-up of the L-chondrite parent body. Instead the data reconcile with a small, possibly a factor of 2–3, increase in the flux of extraterrestrial material to Earth, but of both H- and L-chondritic composition. We also report the composition of all the 2310 terrestrial chrome spinel grains recovered, and show that their chemical composition indicates a dominantly regional ophiolitic source. Four anomalous chrome spinel grains with high Ti and V concentrations were found in the Popigai ejecta. These grains originate from Siberian Traps basalts in the Popigai crater at the time of impact.

The Cretaceous–Tertiary boundary (KTB) transition in NE Brazil

At 7800 km from Yucatan the Cretaceous–Tertiary boundary (KTB) transition of the Poty Quarry, NE Brazil, is the most distant locality with published accounts of Chicxulub impact–tsunami deposits, impact spherules and Ir anomaly. New investigations based on sedimentology, biostratigraphy, mineralogy and geochemistry fail to confirm these reports. Latest Maastrichtian planktic foraminiferal zones CF1 below an erosive and bioturbated disconformity and early Danian zone P1a(1) above indicate a short hiatus, with the KTB clay (zone P0), the Ir anomaly and the characteristic negative δ 13 C excursion missing. The disconformity coincides with the globally recognized latest Maastrichtian sea-level fall. Above the disconformity, an upward-fining micro-conglomerate with abundant reworked Cretaceous foraminifera, sub-angular phosphate clasts, calcitic and phosphatic spheroids along with an early Danian zone P1a(1) assemblage is interpreted as a gravity-flow deposit. Common spheroids throughout the late Campanian–Maastrichtian appear to be chamber infillings of the benthic foraminifer Dentalina alternata . Minor Ir anomalies in thin clay layers of zone Pla and no evidence of the Chicxulub impact reveal that the Poty Quarry section remains a very important example of the complex global environmental and sea-level changes observed in KT sequences from North America to Central America that are commonly misinterpreted as impact–tsunami events. Supplementary materials: Data for trace elements are available at www.geolsoc.org.uk/SUP18585 .

Relationship between mass extinction and iridium across the Cretaceous-Paleogene boundary in New Jersey

We directly link iridium (Ir) anomalies in New Jersey to the mass extinction of marine plankton marking the Cretaceous-Paleogene (K-Pg) boundary. We confirm previous reports of an Ir anomaly 20 cm below the extinction of Cretaceous macrofauna (the “ Pinna ” bed) with new results from a muddy sand section from Tighe Park, Freehold, New Jersey (United States), but we also show that Ir anomalies correlate with marine mass extinctions at three other clay-rich New Jersey sections. Thus, we attribute the anomaly at Freehold to the downward movement of Ir and reaffirm the link between impact and mass extinction.

Multiple Ir anomalies in uppermost Triassic to Jurassic-age strata of the Blomidon Formation, Fundy basin, eastern Canada

A detailed profile of Ir concentrations in continental strata of the Blomidon Formation ostensibly spanning the Triassic–Jurassic boundary confirms the existence of multiple anomalies, with a peak Ir concentration of 450 pg/g. The total amount of Ir deposited exceeds 4 ng/cm 2, a value that requires an external source other than typical terrestrial sediment. Of the 10 other elements measure, only Zn and organic carbon are correlated to Ir. The organic carbon appears to be concentrated in mm-thick kerogenous laminae in greenish-grey to dark grey sediment layers that also host the Ir anomalies. The stratigraphic distribution of Ir and probably Zn appears to be controlled largely by redox boundaries conditions, with Ir probably forming organo-metallic complexes. We find no specific geochemical or sedimentological evidence for an extraterrestrial source for this enrichment, although we cannot exclude an impact origin. However, the close spatial and temporal relationship of the Ir anomalies in the Fundy and Newark basins to the basalts of the Central Atlantic Magmatic Province suggests alternative working hypotheses. Potentially, the volcanic rocks sourced the Ir through post-eruptive fluid mobilization into the surrounding sediments. Conversely, mantle outgassing and aerosol deposition during early stages of the eruptions may have been the source for the Ir anomalies. At this time, the data are insufficient to eliminate any of these hypotheses conclusively.

On the origin of stable IR anomalies detected by satellites above seismo-active regions

A number of experimental evidences have recently been obtained for existence of stable anomalies of infra-red outgoing Earth radiation in seismo-active regions, basically by using NOAA-series satellite data. A theoretical model for temperature enhancement of the ground surface layer in the vicinity of fault system of the Earth’s crust is developed. It is assumed that a tectonic stress in this area results in a water squeezing-out from the higher depths towards the Earth’s surface. A convection mechanism of rock warming by groundwater upward filtrating is considered as a possible reason for stable temperature anomalies arising near the fault interception. According to this model the fluid filtrates upwards from the higher depth to the Earth’s surface to provide an increase in the ground temperature similar to that found in observations.

Estimating Duration and Intensity of Neoproterozoic Snowball Glaciations from Ir Anomalies

The Neoproterozoic glaciations supposedly ended in a supergreenhouse environment, which led to rapid melting of the ice cover and precipitation of the so-called cap carbonates. If Earth was covered with ice, then extraterrestrial material would have accumulated on and within the ice and precipitated during rapid melting at the end of the glaciation. We found iridium (Ir) anomalies at the base of cap carbonates in three drill cores from the Eastern Congo craton. Our data confirm the presence of extended global Neoproterozoic glaciations and indicate that the duration of the Marinoan glacial episode was at least 3 million, and most likely 12 million, years.

Delayed climate cooling in the Late Eocene caused by multiple impacts: high-resolution geochemical studies at Massignano, Italy

High-resolution studies ( δ 13C, δ 18O, and elemental abundances) were done in rocks at and below the GSSP for the Eocene/Oligocene (E/O) boundary at Massignano, Italy. In addition to an earlier known Ir anomaly at 5.61 m, which is possibly linked to the Popigai impact event, we confirm the presence of two additional Ir anomalies in the intervals from 6.00 to 6.40 m and from 10.00 to 10.50 m, with maximum values of 259±32 ppt at 6.17 m, and 149±24 ppt at 10.28 m, respectively. The lower Ir anomaly might be derived from the Chesapeake Bay impact event, whereas for the other one no impact event is known. Similar δ 13C and δ 18O trends related to the two Ir anomalies indicate that the Ir anomaly at 10.28 m might be also derived from an impact into a continental shelf, similar to the Chesapeake Bay impact event. δ 18O values decrease in the high Ir layers to −1.16‰ and −1.17‰, respectively, which, together with the negative shifts in δ 13C in the Ir-rich levels, indicate a warm pulse superimposed on a general Late Eocene cooling trend that is characterized by δ 18O values ranging between −0.6‰ and −0.4‰. The release of methane hydrate after an impact in a continental shelf or seafloor, or impacts of 12C-rich comets during a 2.2-million-year-long comet shower, respectively, could produce these more negative carbon and oxygen excursions compared to the continuously decreasing trend over the whole Late Eocene Massignano section.

A search for soot from global wildfires in central Pacific Cretaceous-Tertiary boundary and other extinction and impact horizon sediments.

Hypotheses of global wildfires following the Cretaceous-Tertiary (KT) boundary impact are supported by high concentrations of elemental carbon (3.6 mg cm(-2)) and soot (1.8 mg cm(-2)) in DSDP Site 465, which was located several thousand kilometers from potential continental sources at 65 Ma. Soot is not preserved at four other central Pacific KT localities, but this is attributed to loss during oxic diagenesis. We find no evidence for wildfires related to major impacts in the late Eocene or to Ir anomalies and extinctions in the late Cenomanian.

Early Archean spherule beds: Chromium isotopes confirm origin through multiple impacts of projectiles of carbonaceous chondrite type

Three Early Archean spherule beds from Barberton, South Africa, have anomalous Cr isotope compositions in addition to large Ir anomalies, confirming the presence of meteoritic material with a composition similar to that in carbonaceous chondrites. The extra-terrestrial components in beds S2, S3, and S4 are estimated to be approx. l%, 50% - 60%, and 15% - 30%, respectively. These beds are probably the distal, and possibly global, ejecta from major large-body impacts. These impacts were probably much larger than the Cretaceous-Tertiary event, and all occurred over an interval of approx. 20 m.y., implying an impactor flux at 3.2 Ga that was more than an order of magnitude greater than the present flux.

Iridium concentrations and abundances of meteoritic ejecta from the Eltanin impact in sediment cores from Polarstern expedition ANT XII/4

The abundances of meteoritic ejecta from the Eltanin asteroid impact have been examined in seven sediment cores recovered by the FS Polarstern during expedition ANT XII/4 using elemental concentrations of iridium and weights of coarse (>500 μm) ejecta debris. Three cores with well-preserved impact deposits, PS2704-1, PS2708-1, and PS2709-1, each contain Ir and ejecta fluences similar to those found previously in USNS Eltanin core E13-4. Small Ir anomalies and traces of ejecta were found in cores PS2706-1 and PS2710-1, but since these cores lack well-defined deposits, these are considered to be reworked and not representative of the fallout. No evidence of ejecta was found in cores PS2702-1 and PS2705-1. These results confirm earlier speculation that the Eltanin impact resulted in deposits of ejecta with up to 1 g/cm2 of debris over a wide area of the ocean floor. However, there are still large uncertainties over the actual regional or global extent of this unique sediment deposit.

Are Ir anomalies sufficient and unique indicators for cosmic events?

Ir anomalies are often considered unique indicators for cosmic events. The present paper compares the contents and patterns of platinum group element (PGE) anomalies of magmatic and sedimentary origins with similar anomalies found in the Cretaceous–Tertiary (K/T) boundary impact clay and other PGE enriched layers across the K/T boundary and early Danian ( Parvularugoglobigerina eugubina zone) at Beloc, Haiti. This analysis demonstrates that PGE patterns provide more conclusive evidence for the reconstruction of paleoevents than that can be achieved by Ir content alone.

Ir anomalies and other elemental markers near the Palaeocene-Eocene boundary in a flysch sequence from the Western Tethys (Slovenia)

Ir abundance anomalies, platinum-group elements (PGE) enrichment and increased concentrations of meteoritic (Ni, Fe, Co) and nonmeteoritic (Sb, As, Zn and Cu) elements were found in the Palaeocene–Eocene (P/E) boundary interval in a flysch sequence from the Western Tethys (Goriska Brda section, W. Slovenia). This records one of the most important calcareous deep benthic extinctions in the history of the Earth. Although the observed geochemical patterns could indicate complex sources for these metals, such as weathering of the continental and oceanic crust, volcanic processes, as well as diagenetic mobilization and redistribution, we cannot preclude the highly speculative possibility that the observed Ir abundances may also indicate extraterrestrial contamination.