Labile trace elements and cosmogenic radionuclides in chondritic hosts of three consortium igneous inclusions

Three ordinary chondrites from the Yamato Mountains (Y) region of Antarctica contain cm-sized igneous inclusions being studied by a consortium. RNAA data for the labile elements Ag, Bi, Cd, Cs, Ga, In, Rb, Sb, Se, Te, Tl and Zn, and refractory Au and U in the L6 hosts of Y-75097 and Y-793241 indicate that each experienced at least one preterrestrial, high-temperature episode. This heating occurred during formation of the igneous inclusions and/or as a result of the severe shock that affected most equilibrated L chondrites. Cosmogenic 720ka ^Al, and 301ka^Cl (which are determined by AMS) in metal from these two meteorites and nominal terrestrial ages (based on ^Cl) hint that the L6 chondrites are not paired but are inconclusive in this regard. RNAA data for the H chondrite host of Y-794046 generally resemble those of other H4-6 chondrites : its contents of cosmogenic radionuclides in general, and its ^Cl content, in particular, correspond to a nominal terrestrial age of 70±60ka

Al-26 production profile and model comparisons in Canyon Diablo

The large preatmospheric size of the Canyon Diablo meteorite, a radius of about 15 m, makes it especially suitable for systematic studies of cosmogenic nuclide production rates of iron objects in a 2 pi geometry. To reconstruct the exposure history of the meteoroid, Heymann et al. investigated several fragments recovered from known geographic locations around the crater for their shock features and cosmogenic nobel gases. They applied the Signer-Nier noble gas production rate model to establish the preatmospheric depth of the specimens in the meteoroid. Cosmic ray exposure ages suggested a multi-episodic irradiation, with 170 or 540 Ma being inferred for most of the samples studied while two anomalous specimens indicated a possible third exposure age at 940 Ma. Be-10 and Cl-36 have been measured in a number of these same samples by accelerator mass spectrometry (AMS), with use being made of the preatmospheric depths determined in Heymann et al. to construct production profiles. The present study extends the cosmogenic radionuclide data to Al-26 and compares the results with both the production rate model of Reedy and Arnold and production rates determined from the cross sections used by the Reedy-Arnold model (for the major nuclear reactions making Al-26) in combination with differential fluxes calculated using the Los Alamos High Energy Transport (LAHET) Code System. Model calculations for Be-10 and Cl-36 have also been obtained

Cosmogenic radionuclides in meteorites: Depth profiles in Canyon Diablo and a temporal variation in H chondrite sources

The cosmogenic radionuclides \sp{26}Al (t\sb{{1\over 2}} = 0.71 Myr), \sp{10}Be (t\sb{{1\over 2}} = 1.5 Myr), and \sp{36}Cl (t\sb{{1\over 2}} = 0.30 Myr) have been measured in 12 fragments of the Canyon Diablo meteorite and in 39 Antarctic meteorites. Canyon Diablo results have experimentally confirmed theoretical calculations that there is a very significant matrix-dependent component to the build-up and development of the secondary flux of cosmic rays in meteorites. Cosmic-ray exposure ages calculated using these results are about 540 Myr in most cases. Terrestrial ages calculated for Antarctic meteorites from \sp{36}Cl data are generally $\u3c$100 kyr. Multivariate statistical analyses of the labile trace elements in 38 Antarctic finds and 58 non-Antarctic falls, all H chondrites, indicates that meteorites of long ($\u3e$50 kyr) terrestrial age are the most compositionally distinct from falls. Meanwhile, the Antarctic meteorites most recently captured by the Earth are not distinguishable from the (also recently captured) falls. This is strong evidence that the differences seen between Antarctic and non-Antarctic meteorites are the result of temporal variations in the H chondrite flux to Earth

Correlating military sonar use with beaked whale mass strandings: What do the historical data show?

There have been several incidents in which U.S. Navy sonar operations at sea coincided in time and location with a mass stranding of marine mammals, particularly beaked whales. Although a conclusive cause-and-effect relationship has not been established, there is strong evidence and scientific concern that use of military sonar has resulted in beaked whale mass strandings. Most previous attempts to determine whether military sonar use and whale strandings are correlated have looked at mass stranding records of beaked whales and have singled out those instances in which military operations appear to coincide in time and location with a mass stranding event. In this study, historical data on beaked whale mass strandings and military exercises that were likely to include active sonar use were compiled, and statistical analyses were performed to determine the level of correlation between these events for four geographic regions. Strandings were significantly correlated with naval activity in the Mediterranean and Caribbean Seas, but not off the coasts of Japan and southern California

Correlating military sonar use with beaked whale mass strandings:What do the historical data show?

There have been several incidents in which U.S. Navy sonar operations at sea coincided in time and location with a mass stranding of marine mammals, particularly beaked whales. Although a conclusive cause-and-effect relationship has not been established, there is strong evidence and scientific concern that use of military sonar has resulted in beaked whale mass strandings. Most previous attempts to determine whether military sonar use and whale strandings are correlated have looked at mass stranding records of beaked whales and have singled out those instances in which military operations appear to coincide in time and location with a mass stranding event. In this study, historical data on beaked whale mass strandings and military exercises that were likely to include active sonar use were compiled, and statistical analyses were performed to determine the level of correlation between these events for four geographic regions. Strandings were significantly correlated with naval activity in the Mediterranean and Caribbean Seas, but not off the coasts of Japan and southern California.</p