- I am retired, but still doing some research.edit
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Investigation of glass particles recovered from Apollo 11 and Apollo 12 fines, and composition and heteorogeneity of lunar surface
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ABSTRACT Electron microprobe and petrographic analyses of crystalline rock and separates from apollo 11 lunar soil samples
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In 18 Muong Nong-type tektites, concentrations of Be-10 and of mineral inclusions anticorrelate. Be-10 is lowest and the source crater probably lies within a region between the southern Laotian border and the southwestern tip of Hainan... more
In 18 Muong Nong-type tektites, concentrations of Be-10 and of mineral inclusions anticorrelate. Be-10 is lowest and the source crater probably lies within a region between the southern Laotian border and the southwestern tip of Hainan Island, China.
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During the present study the Ivory Coast microtektite layer was found in cores from five equatorial Atlantic sites, bringing the total number of Ivory Coast microtektite-bearing cores to eleven. The strewn field appears to be restricted... more
During the present study the Ivory Coast microtektite layer was found in cores from five equatorial Atlantic sites, bringing the total number of Ivory Coast microtektite-bearing cores to eleven. The strewn field appears to be restricted to between 9°N and 12°S latitude. There is a general increase in the concentration of microtektites towards the Bosumtwi crater, which is generally thought to be the source of the Ivory Coast tektites. The relationship between the onset of the Jaramillo subchron and the Ivory Coast microtektite layer has been investigated in six cores. A plot of the difference in depth between the base of the Jaramillo subchron and the microtektite layer versus sediment accumulation rate was used to determine the average post-depositional remanent magnetization (PDRM) acquisition depth and the age difference between the onset of the Jaramillo subchron and the deposition of the microtektites. Assuming that the PDRM acquisition depth does not vary with sediment accumul...
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During the present study the Ivory Coast microtektite layer was found in cores from five equatorial Atlantic sites, bringing the total number of Ivory Coast microtektite-bearing cores to eleven. The strewn field appears to be restricted... more
During the present study the Ivory Coast microtektite layer was found in cores from five equatorial Atlantic sites, bringing the total number of Ivory Coast microtektite-bearing cores to eleven. The strewn field appears to be restricted to between 9 o N and 12°S latitude. There is a general increase in the concentration of microtektites towards the Bosumtwi crater, which is generally thought to be the source of the Ivory Coast tektites. The relationship between the onset of the Jaramillo subchron and the Ivory Coast microtektite layer has been investigated in six cores. A plot of the difference in depth between the base of the Jaramillo subchron and the microtektite layer versus sediment accumulation rate was used to determine the average post-depositional remanent magnetization (PDRM) acquisition depth and the age difference between the onset of the Jaramillo subchron and the deposition of the microtektites. Assuming that the PDRM acquisition depth does not vary with sediment accum...
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Australasian microtektites have been found in cores from nearly fifty sites in the Indian Ocean, eastern equatorial Pacific, and Philippine, Sulu, and Celebes Seas [1, 2, 3]. We previously reported the discovery of unmelted impact ejecta... more
Australasian microtektites have been found in cores from nearly fifty sites in the Indian Ocean, eastern equatorial Pacific, and Philippine, Sulu, and Celebes Seas [1, 2, 3]. We previously reported the discovery of unmelted impact ejecta (shocked quartz, coesite, stishovite), in the > 125 m size fraction of seven cores from the Australasian strewn field [4]. In six of the cores, unmelted impact ejecta were found associated with Australasian microtektites, but in one core unmelted ejecta, with the same stratigraphic age, based on magnetostratigraphy, were found without any associated microtektites. We report here the discovery of unmelted impact ejecta in three additional cores from the Australasian strewn field. The unmelted impact ejecta at one of the new sites (ODP 768) is associated with Australasian microtektites, but at the other two sites (V19-116 and V20-142) it is not. We also determined the abundance of unmelted impact ejecta in the 63-125 m size fraction at two sites (V...
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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... more
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 wit...
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Introduction: Australasian tektites have been found in Indochina, south China, the Philippines, Malaysia, Indonesia, and Australia. Microtektites belonging to this strewn field have been found throughout most of the Indian Ocean, the... more
Introduction: Australasian tektites have been found in Indochina, south China, the Philippines, Malaysia, Indonesia, and Australia. Microtektites belonging to this strewn field have been found throughout most of the Indian Ocean, the western equatorial Pacific, and the Philippine, Celebes, and Sulu seas. Altogether, this strewn field covers about 14% of the Earth’s surface. It is the youngest of the known tektite strewn fields with an age of only ~0.8 Ma. Based on abundance, shape, size, petrography, and composition of the Australasian tektites, several authors have suggested that the source crater is probably somewhere in Indochina [e.g.,1-4]. Geographic variations in the concentration (number per unit area) of Australasian microtektites is also best explained by a source area in Indochina [5]. However, in spite of the young age and large size of this strewn field, the source crater has not been found. Large, blocky, layered tektites (called Muong Nongtype tektites) are found prima...
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Although tektites are thought to be of impact origin, based primarily on geochemical data, the source craters for the Australasian and North American tektite strewn fields have not been located. Furthermore, tektites have not been found... more
Although tektites are thought to be of impact origin, based primarily on geochemical data, the source craters for the Australasian and North American tektite strewn fields have not been located. Furthermore, tektites have not been found associated with impact ejecta until recently. Impact ejecta were first found associated with tektite glass at DSDP Site 612 on the upper continental slope off New Jersey (1,2). Although some authors (e.g., 1,3,4) believe that the Site 612 tektite glass was produced during the North American tektite event, others believe that they represent a somewhat older, previously unrecognized tektite event (5). The most easily recognized impact ejecta at Site 612 are white opaque grains of coesite and coesite plus shocked quartz. In this abstract we report the discovery of grains consisting of coesite and mixtures of quartz and coesite associated with the North American and Australasian microtektite layers. One hundred and fourteen and 162 grains (mostly white o...
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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,... more
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 inclusi...
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Previous studies have shown that an 8-cm-thick layer of impact ejecta (including tektites, shocked quartz, coesite, and stishovite) occurs at Deep Sea Drilling Project (DSDP) Site 612 on the Continental Slope off New Jersey. During Leg... more
Previous studies have shown that an 8-cm-thick layer of impact ejecta (including tektites, shocked quartz, coesite, and stishovite) occurs at Deep Sea Drilling Project (DSDP) Site 612 on the Continental Slope off New Jersey. During Leg 150 of the Ocean Drilling Project (ODP) two additional sites, drilled within 9 km of Site 612, were found to contain late Eocene impact
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Microtektites from the 35 Ma upper Eocene North American tektite strewn field have recently been analyzed for major and trace element composition (in particular, the rare earth element (REE) abundances), using the electron microprobe and... more
Microtektites from the 35 Ma upper Eocene North American tektite strewn field have recently been analyzed for major and trace element composition (in particular, the rare earth element (REE) abundances), using the electron microprobe and neutron activation analysis (see also [1]). The microtektites were recovered from drill cores from the northwest Atlantic off New Jersey, the Caribbean Sea, and the Gulf of Mexico. In our study, we individually analyzed more than 100 microtektites for trace element contents. Typical sample masses were 5–50 μg. Previously, only few trace element data for bediasites and georgiaites were available. To improve the data base, and to allow detailed comparison with the microtektite data, we analyzed nine samples of bediasites from Biddings, Texas, and two tektite fragments from Dodge County, Georgia. The results were compared with previously determined REE abundances [2-4] for the calculation of "average georgiaite" and "average bediasite&qu...
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The safe disposal of high-level radioactive wastes from nuclear reactors is a major problem because of the danger of life which may arise if these substances were released into the environment. Disposal of nuclear wastes in glass requires... more
The safe disposal of high-level radioactive wastes from nuclear reactors is a major problem because of the danger of life which may arise if these substances were released into the environment. Disposal of nuclear wastes in glass requires assurance that the glass will survive for a time on the order of 10{sup 6} years. Since no man-made glasses have been around that long, it is proposed to study various naturally-occurring glasses in order to determine their durability with time in various natural environments. The purpose of the proposed research was to study the rate of solution of naturally-occurring glasses in various geological environments. During the first year of the contract the emphasis was on glass particles (i.e., microtektites) found in deep-sea sediments. 11 refs., 4 figs., 2 tabs.
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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... more
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 samp...
North American tektite fragments have been found in core 21, DSDP Site 612, taken in 1404 m of water on the Continental Rise off New Jersey (1-3). In order to better define this layer, a continuous sequence of samples taken at 1 cm... more
North American tektite fragments have been found in core 21, DSDP Site 612, taken in 1404 m of water on the Continental Rise off New Jersey (1-3). In order to better define this layer, a continuous sequence of samples taken at 1 cm intervals through the layer have been studied. The layer of tektite debris is mostly confined to an 8 cm thick layer between 111 and 119 cm in section 5 of core 21. In this interval tektite debris makes up between 52% and 80% of the > 250 pm size fraction. Approximately 40% of the grains have been moderately to almost completely pyritized with the highest percentage of pyritized fragments in the upper 3 cm of the tektite-rich layer. Less than 1 nun diameter microtektites are present but rare. They make up < 1% of the tektite debris. Unbroken tektite specimens up to several millimeters in size have also been found. Detrital mineral grains (mostly quartz), glauconite, and rock fragments are also concentrated in this layer where they make up an average...
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Fractionation effects related to evaporation and condensation had a major impact on the current elemental and isotopic composition of the Solar System. Although isotopic fractionation of moderately volatile elements has been observed in... more
Fractionation effects related to evaporation and condensation had a major impact on the current elemental and isotopic composition of the Solar System. Although isotopic fractionation of moderately volatile elements has been observed in tektites due to impact heating, the exact nature of the processes taking place during hypervelocity impacts remains poorly understood. By studying Fe in microtektites, here we show that impact events do not simply lead to melting, melt expulsion and evaporation, but involve a convoluted sequence of processes including condensation, variable degrees of mixing between isotopically distinct reservoirs and ablative evaporation during atmospheric re-entry. Hypervelocity impacts can as such not only generate isotopically heavy, but also isotopically light ejecta, with δ56/54Fe spanning over nearly 5‰ and likely even larger variations for more volatile elements. The mechanisms demonstrated here for terrestrial impact ejecta modify our understanding of the e...