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Glass, B. P.

Publications and source records attributed to Glass, B. P..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2002

Discovery of coesite and shocked quartz associated with the upper Eocene cpx spherule layer

At least two major impact ejecta layers have been discovered in upper Eocene strata. The upper layer is the North American microtektite layer. lt consists tektite fragments, microtektites, and shocked mineral grains (e.g., quartz and feldspar with multiple sets of PDFs, coesite and reidite (a high-pressure polymorph of zircon)). The slightly older layer contains clinopyroxene-bearing (cpx) spherules and microtektites associated with an Ir anomaly. The North American tektite layer may be derived from the Chesapeake Bay impact structure, and the cpx spherule layer may from the Popigai impact crater. A cpx spherule layer associated with a positive Ir anomaly was recently found at ODP Site 709, western Indian Ocean. A large sample (Hole 709C, core 31, section 4, 145-150 cm), originally used for a study of interstitial water by shipboard scientists, was acquired for the purpose of recovering a large number of spherules for various petrographic and geochemical studies. A split of the sample (50.35 g) was disaggregated and wet-sieved. More than 17,000 cpx spherules and several hundred microtektites (larger than 125 microns) were recovered from the sample. Rare white opaque grains were observed in the 125-250 micron size fraction after removal of the carbonate component using dilute HCI. Seven of the white opaque grains were X-rayed using a Gandolfi camera and six were found to be coesite (probably mixed with lechatelierite). Eighty translucent colorless grains from the 63-125 micron size fraction were studied with a petrographic microscope. Four of the grains exhibit one to two sets of planar deformation features (PDFs). The only other possible known occurrence of shocked minerals associated with the cpx spherule layer is at Massignano, Italy, where pancake-shaped clay spherules (thought to be diagenetically altered cpx spherules are associated with a positive Ir anomaly and Ni- rich spinel crystals. Shocked quartz grains with multiple sets of PDFs also occur at this site. Until now, unmelted impact ejecta have not been found associated with the cpx spherules at any of the other 20 sites around the world and this is the first time that coesite has been found associated with the cpx spherule layer. The discovery of coesite and shocked quartz associated with the cpx spherules at Site 709 in Indian Ocean is further evidence for the impact origin of the cpx spherule layer. We hope that future discovery of other unmelted minerals from this sample may provide materials to establish constraints on the provenance of this late Eocene ejecta.

Liu, S.↗
NASA NTRS2001

Sr and Nd Data for Upper Eocene Spherule Layers

Sr and Nd data for clinopyroxene-bearing (cpx) spherules from three sites support conclusions that there is only one cpx spherule layer and that the source crater may be Popigai. Additional information is contained in the original extended abstract.

Liu, Shaobin↗
NASA NTRS2000

Upper Eocene Spherules at ODP Site 1090B

Our two labs independently discovered upper Eocene microtektites and microkrystites at ODP Site 1090, a new South Atlantic locality near the Agulhus Ridge. This is a significant new data point for the strewn fields of these spherules, which were recently extended into the Atlantic sector of the Southern Ocean when they were reported at ODP Site 689 on the Maude Rise. The microtektites have been regarded as related to North American tektites and the microkrystites as belonging to the clinopyroxene-bearing (cpx) spherule strewn field. Initial reports indicate that Site 1090 contains a complete sequence of upper Eocene sediments composed of diatom and nannofossil oozes. The magneto- and bio-stratigraphy indicate that impact-age sediments should occur in core 30X of Hole 1090B. One of us (FTK) took 2 cc samples at 10 cm intervals over 600 cm of core for Ir analyses and the senior author (SL) took 3 cc samples at 20 cm intervals to search for spherules. Both studies proved successful and additional samples were obtained to confirm initial results and better define the Ir anomaly and spherule abundances. Peak Ir concentrations of 0.97 ng/g were found at 1090B-30X-5, 105-106cm and 0.78 ng/g at 115-116 cm. Anomalous Ir concentrations (greater than 0.1 ng/g) extend over about 100 cm of core. Preliminary results indicate that the excess Ir at this site is about 25 ng per sq cm. About 380 microtektites (>63 pm) and 2492 microkrystites (>63 pm) were recovered over a 1.8 m interval with a peak abundance of microtektites (106/gram) and microkrystites (562/gram) at 1090B-30X- 5, 114-115 cm. The largest microtektite is approximately 960 x 1140 micron in size. About 55 % are spherical, and the rest are disc, cylinder, dumbbell, teardrop, or fragments. Most of the microtektites are transparent colorless, but a few are transparent pale brown or green. Preliminary data indicate that the microtektites at Site 1090 have similar major oxide compositions to those at Site 689. About 50% of the cpx spherules are spherical, the rest are fragments. They range from yellowish translucent to dark opaque. Based on stratigraphic data, occurrence of a positive Ir anomaly, and similar appearance and major oxide compositions of the Site 1090 spherules to those at Site 689, we believe that the spherule layer(s) are the same at both sites. However, there are significant differences between these two sites. At Site 689 the peak abundance of the cpx spherules is slightly below that of the microtektites. We can distinguish no such separation at Site 1090, despite a somewhat higher sediment accumulation rates. Peak Ir concentrations are about four times higher at Site 1090, resulting in a similarly higher total flux of Ir for this site compared to Site 689 on the Maude Rise. This is generally consistent with the flux of cpx spherules (greater than 63 pm) which is estimated to be approximately -2100 per sq cm, about twice that of Site 689D (1040 sq cm) and with the cpx-spherule component being a principal carrier of the Ir signal. The number of microtektites per sq cm (greater than 63 micron) is nearly the same at both sites, approximately 300 in 1090B and 280 in 689B. A decrease in the greater than 63 micron size fraction (consisting primarily of diatoms and radiolaria) is coincident with the spherule layer at both sites suggesting that the impact(s) that produced the spherule layer(s) may have had an adverse affect on the marine plankton.

Liu, S.↗
NASA NTRS1993

K/T spherules from Haiti and Wyoming: Origin, diagenesis, and similarity to some microtektites

Spherules with relict glass cores in the K/T boundary bed of Haiti allow for a comparison of these bodies with hollow goyazite shells in the K/T boundary claystone of Wyoming and with younger microtektites of the Ivory Coast strewn field. Samples of the Haitian beds from undisturbed sections at Beloc, as determined by Jehanno et al., contain both hollow shells and relict glass cores rimmed by palagonite that has been partially converted to smectite. These palagonite rims developed from hydration zones formed when hot, splash-form droplets of andesitic impact glass were deposited into water. Mutual collisions between these droplets in the ejecta curtain may have formed point-source stresses on their surfaces. Initiation of hydration would be facilitated at these surface stress points and propagated radially into the glass. The inner surface of these merged hemispherical fronts appears mammillary, which is reflected as scalloping in Haitian relict glass cores.

Bohor, B. F.↗
NASA NTRS1993

Cretaceous-tertiary boundary spherules and Cenozoic microtektites: Similarities and differences

Bohor and Betterton pointed out that the K-T spherules can be divided into three groups. Their Type 1 spherules appear to be found in or adjacent to North America, particularly the Western Interior and in Haiti and Mexico. The Type 1 spherules occur in the lower part of the K-T boundary clay below an Ir anomaly. It is the Type 1 spherules which are most similar to microtektites. The discovery of K-T boundary spherules in Beloc, Haiti, and Mimbral, Mexico, with residual tektite-like glass cores supports the hypothesis that the Type 1 spherules are diagenetically altered microtektites. The similarities and differences of the Type 1 K-T boundary spherules to previously described Cenozoic microtektites are discussed.

Glass, B. P.↗
NASA NTRS1992

Search for microaustralites in deep-sea sediments less than 20,000 years old

Several authors have proposed that australites fell less than 20,000 years ago. We searched for microtektites in the tops of 46 deep-sea cores and were unable to find evidence for a microtektite layer less than 20,000 years old. Either the australite fall was not accompanied by microtektites, or the strewnfield did not extend into the area searched, or the australites fell about 0.77 Ma ago as indicated by their radiometric ages.

Glass, B. P.↗
NASA NTRS1988

Late Eocene impact events recorded in deep-sea sediments

Raup and Sepkoski proposed that mass extinctions have occurred every 26 Myr during the last 250 Myr. In order to explain this 26 Myr periodicity, it was proposed that the mass extinctions were caused by periodic increases in cometary impacts. One method to test this hypothesis is to determine if there were periodic increases in impact events (based on crater ages) that correlate with mass extinctions. A way to test the hypothesis that mass extinctions were caused by periodic increases in impact cratering is to look for evidence of impact events in deep-sea deposits. This method allows direct observation of the temporal relationship between impact events and extinctions as recorded in the sedimentary record. There is evidence in the deep-sea record for two (possibly three) impact events in the late Eocene. The younger event, represented by the North American microtektite layer, is not associated with an Ir anomaly. The older event, defined by the cpx spherule layer, is associated with an Ir anomaly. However, neither of the two impact events recorded in late Eocene deposits appears to be associated with an unusual number of extinctions. Thus there is little evidence in the deep-sea record for an impact-related mass extinction in the late Eocene.

Glass, B. P.↗
NASA NTRS1985

Lunar sample 14425 - Corrected analysis

A polished section of lunar sample 14425, an 8 mm glass bead, was studied using a scanning electron microscope and energy-dispersive X-ray analyzer. The silicon, aluminum, iron, magnesium, calcium, sodium, potassium, titanium, and chromium contents of the glass were determined. Two types of glass are visible in the polished section. One is clear and almost devoid of metallic spherules, while the other is cloudy and contains numerous metallic spherules, some less than one micron in size. Both glass types are homogeneous and identical in composition. This composition closely matches that of some Apollo 14 breccias or glass found in the breccias. The apparent similarity in composition between lunar sample 14425 and the high-magnesium microtektites found in a previous study was probably due to charging effects during analyses in which the sample was uncoated.

Glass, B. P.↗
NASA NTRS1985

Nd and Sr isotopic compositions of tektite material from Barbados and their relationship to North American tektites

The isotopic composition of microtektites from Barbados was determined to establish their possible source and their relationship to known tektite strewn fields. Analyzed samples included microtektites and tektite fragments from the Barbados oceanic beds, samples of deep sea ooze, in which they occur, and of underlying volcanic ash, as well as glass beads from Lake Wanapitei Crater. Isotope ratios (Sr-87/Sr-86, Nd-143/Nd-144, Rb-87/Sr-86, and Sm-147/Nd-144) were determined, and the epsilon values for Sr and Nd plotted on the diagram available for the fields of North America, Australia, Ivory Coast, and Moldavite tektites. The epsilon coordinates of all Barbados microtektite and bulk tektite samples plot precisely within the narrow field determined by North American tektites (epsilon Sr, 111; epsilon Nd, -6.2), yield an Nd model age of 0.6 AE, and are distinct from all other fields. The isotopic signatures of samples from sea ooze, ash layer, and of the Lake Wanapitei glass beads are clearly different from all known tektite classes. It is concluded that the Barbados tektites are of the same source and temporal event as the North American tektites.

Ngo, H. H.↗
NASA NTRS1982

Solution of naturally-ocurring glasses in the geological environment

As part of a study to investigate the feasibility of putting nuclear wastes in glass containers and burying them on land or dumping them in the ocean, the amount of solution experience by naturally occurring glasses from two land sites and thirty-four deep sea sites was studied. The glasses are microtektites from three strewn fields and from the Zhamanshin impact crater. The microtektites range in age from 0.7 to 35 m.y. and have a wide range in composition. The weight percent SiO2, for example, ranges from 44.8 to 81.7. Although several criteria for determining the amount of solution were considered, most of the conclusions are based on two criteria: (1) width of cracks, and (2) elevation of silica rich inclusions above the adjacent microtektite surface. All the measurements were made on scanning electron microscope photomicrographs of the microtektites.

Glass, B. P.↗
NASA NTRS1976

High-silica /greater than 60%/ lunar glasses in an Apollo 14 soil sample - Evidence for silicic lunar volcanism

The major-element compositions of 93 low-specific-gravity (less than 2.60) high-silica (greater than 60%) glass particles from a sample of lunar fines (14259,20) were determined by electron microprobe analyses. The size, shape, abundance, mineralogy, and major-element composition of more than 60% of the high-silica glasses is consistent with their being fragments of interstitial glass from mare basalts. However, one group of 30 glasses with between 72% and 78% SiO2 and an average of approximately 2.6% FeO can be distinguished from other high-silica glasses both chemically and petrographically. Glass particles with this composition do not contain crystalline inclusions and are fairly homogeneous not only within a single particle but also from particle to particle. The chemistry and petrology of these glasses suggest that they are not fragments of interstitial glass or shock-melted particles from a 'granitic' source rock. Rather, the homogeneity and lack of crystalline inclusions suggest that this group of high-silica glasses was the product of lunar acidic volcanism.

Glass, B. P.↗
NASA NTRS1975

Lunar soil and surface processes studies

Glass particles in lunar soil were characterized and compared to terrestrial analogues. In addition, useful information was obtained concerning the nature of lunar surface processes (e.g. volcanism and impact), maturity of soils and chemistry and heterogeneity of lunar surface material. It is felt, however, that the most important result of the study was that it demonstrated that the investigation of glass particles from the regolith of planetary bodies with little or no atmospheres can be a powerful method for learning about the surface processes and chemistry of planetary surfaces. Thus, the return of samples from other planetary bodies (especially the terrestrial planets and asteroids) using unmanned spacecraft is urged.

Glass, B. P.↗
NASA NTRS1974

Investigation of a glass spherule from the Luna-16 probe

A glass spherule of the form of a flattened spheroid measuring 580 microns in diameter is studied. The spherule is transparent, shiny, and of a yellowish brown tint. It contains a number of central and peripheral spherical bubble-type cavities. The surface and morphology features resemble those of Apollo spherules, but differ in chemical composition, which is close to that of the Luna-16 regolith.

Glass, B. P.↗
NASA NTRS1973

Major element compositions of Luna 20 glass particles.

Major element analyses of nineteen Luna 20 glass particles indicate that most of the Luna 20 glasses have Al2O3 contents greater than 21 wt % and compositions similar to Apollo 16 and Luna 20 rocks and soils. Three of the glass particles have low Al2O3 (less than 13 wt %) and high FeO (greater than 18 wt %) contents and were probably derived from one of the adjacent maria. The low glass content of the Luna 20 soil indicates that it is relatively young or less mature than most mare soils that have been studied.

Glass, B. P.↗
NASA NTRS1972

Micrometeorite craters on lunar glass particles - The relationship between radial fracture zones and spall zones.

Discussion of the microimpact-crater morphology observed by scanning electron microscopy on a glass bead (nearly 580 microns in maximum diameter) recovered from zone A of the Luna 16 sample. The microcrater has a diameter of approximately 200 microns and a centrally located melted region or pit that is slightly elevated above the surrounding area. Around the pit is a radial fracture zone half of which has spalled off. The spall zone is more than half again as large as the radial fracture zone.

Glass, B. P.↗
NASA NTRS1972

Chemistry and particle track studies of Apollo 14 glasses.

The abundance and the composition of Apollo 14 glasses have been studied. Glass particles were analyzed for Si, Ti, Al, Fe, Mn, Mg, Na, and K by electron microprobe analysis. The refractive indices of 26 particles were determined by the oil immersion method. Track analyses have been carried out in order to determine the uranium content and the radiation history of glass particles. The proper identification of galactic and solar flare nuclei tracks makes it possible to estimated residence times of the glass particles in the top layer of the lunar soil.

Glass, B. P.↗