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Glass spherules, similar to microtektites, have been found near the Frasnian-Famennian boundary (F/F) (Upper Devonian) at Senzeilles, Belgium, contemporaneous with one of the largest marine mass extinctions of the Phanerozoic. These spherules exhibit a wide range of compositions and display teardrop, dumbbell, and compound morphologies analogous to microtektites. In addition, they lack crystallites, have few or no vesicles, and have a low content of volatile material. These characteristics are supportive of an impact origin. The Siljan Ring (Sweden) and Charlevoix structure (Quebec,Canada) are candidate craters of this age. The presence of microtektites near the F/F boundary supports the hypothesis that an impact caused the Upper Devonian worldwide benthic mass extinctions.

(40)Ar/(39)Ar dating of drill core samples of a glassy melt rock recovered from beneath a massive impact breccia contained within the 180-kilometer subsurface Chicxulub crater in Yucatan, Mexico, has yielded well-behaved incremental heating spectra with a mean plateau age of 64.98 +/- 0.05 million years ago (Ma). The glassy melt rock of andesitic composition was obtained from core 9 (1390 to 1393 meters) in the Chicxulub 1 well. The age of the melt rock is virtually indistinguishable from (40)Ar/(39)Ar ages obtained on tektite glass from Beloc, Haiti, and Arroyo el Mimbral, northeastern Mexico, of 65.01 +/- 0.08 Ma (mean plateau age for Beloc) and 65.07 +/- 0.10 Ma (mean total fusion age for both sites). The (40)Ar/(39)Ar ages, in conjunction with geochemical and petrological similarities, strengthen the recent suggestion that the Chicxulub structure is the source for the Haitian and Mexican tektites and is a viable candidate for the Cretaceous-Tertiary boundary impact site.

Restudy of Deep Sea Drilling Project Sites 536 and 540 in the southeast Gulf of Mexico gives evidence for a giant wave at Cretaceous-Tertiary boundary time. Five units are recognized: (1) Cenomanian limestone underlies a hiatus in which the five highest Cretaceous stages are missing, possibly because of catastrophic K-T erosion. (2) Pebbly mudstone, 45 m thick, represents a submarine landslide possibly of K-T age. (3) Current-bedded sandstone, more than 2.5 m thick, contains anomalous iridium, tektite glass, and shocked quartz; it is interpreted as ejecta from a nearby impact crater, reworked on the deep-sea floor by the resulting tsunami. (4) A 50-cm interval of calcareous mudstone containing small Cretaceous planktic foraminifera and the Ir peak is interpreted as the silt-size fraction of the Cretaceous material suspended by the impact-generated wave. (5) Calcareous mudstone with basal Tertiary forams and the uppermost tail of the Ir anomaly overlies the disturbed interval, dating the impact and wave event as K-T boundary age. Like Beloc in Haiti and Mimbral in Mexico, Sites 536 and 540 are consistent with a large K-T age impact at the nearby Chicxulub crater.

δ 18O and δ 13C values for several species of planktonic foraminifera and calcareous nannofossils from Recent deep-sea sediments have been studied in order to evaluate their paleoceanographic and paleotemperature potential. Nannofossils from Indian Ocean core-tops reflect isotopic temperatures as warm as, or warmer than, the temperatures reported by Williams et al. (1977) for shallow-dwelling planktonic foraminifera from the same samples. In general, deep-sea sediment samples from the world's major oceans indicate that nannofossil δ 18O values are from 0.5 to 1 ‰ heavier than shallow-dwelling planktonic foraminifera. Although nannofossil δ 18O values depart from thermodynamic equilibrium with oceanic surface water temperatures, the δ 18O temperature trend parallels that of surface-dwelling planktonic foraminifera. Nannofossil δ 13C values also depart from equilibrium with surface water δ 13C-ΣCO2 values. A comparison of nannofossil δ 13C data with that from planktonic foraminifera suggests that the rate of primary productivity in different water masses may be influencing the δ 13C of carbonate-secreting phytoplankton and zooplankton.

This paper discusses the adverse health effects of air and noise pollution caused by fireworks episodes on Oahu, Hawaii. During such episodes the level of suspended particulates can increase by an average of 300 percent above pre‐fireworks levels. The 24‐hour Hawaii air quality standard can be exceeded by 170 percent. Significantly the lung‐penetrating paxticles of < 4.7 μm may increase by 700 percent due to fireworks smoke. Noise levels can reach 117 dBA exceeding all noise codes. An increase of 113 percent in treated respiratory illness during a fireworks episode was statistically significant, but an 8 percent decline in pulmonary function was not.

Sedimentological and isotopic studies of cores collected by the DV “Glomar Challenger” and the USNS “Eltanin” from the circum-Antarctic region have revealed a chronology of paleoceanographic changes in the Southern Ocean and the paleoglacial history of Antarctica for the past 80 m.y. Oxygen and carbon isotopic compositions of planktonic and benthonic foraminifera and calcareous nannofossils contained in deep-sea sediment cores record paleoceanographic changes in oceanic surface and bottom waters. These data can be interpreted in terms of paleotemperatures, growth of the polar ice-caps and changes in oceanic circulation. Composite high- and low-latitude time-series plots of both oxygen and carbon isotopic data obtained from Cenozoic and Late Mesozoic calcareous micro- and nannofossils are considered in the light of existing knowledge of Antarctic glacial chronology. A slight decline in both surface- and bottom-water temperatures is recorded during the Middle to Late Maastrichtian, at the end of the Cretaceous. Circum-Antarctic oceanic surface-water isotopic temperatures recorded by calcareous nannofossils are similar to bottom-water values recorded by deep-sea benthonic foraminifera elsewhere in the world's oceans, indicating that a thermohaline circulation system driven by sinking of dense water in high latitudes was active throughout the Late Cretaceous. Temperatures during the Paleocene and Early Eocene were warmer than those during the Late Cretaceous minimum. A long-term Cenozoic cooling began during middle Early Eocene time. It was marked by periods of more stable temperatures followed by times of rapid temperature decrease. The late Middle Eocene—Late Eocene was a time of stable temperatures. A significant 5°C decrease in bottom- and surface-water temperatures occurred near the Eocene/Oligocene boundary, marking the production of Antarctic bottom waters at near-freezing temperatures from this time onward (Kennett and Shackleton, 1976). This drop was followed by a moderate Early Miocene—Early mid-Miocene warming and then a period of stable temperatures, until the Middle Miocene at which time a worldwide increase in δ 18O of both planktonic and benthonic carbonate tests occurred. This has been interpreted as either an indication of a major build-up in the Antarctic ice-sheet, or a combination of temperature drop and ice-volume increase. Small quantities of ice-rafted sediment in the circum-Antarctic region are first recorded in Early Eocene—Oligocene sediment cores from the southeastern Pacific sector of the Southern Ocean. The southeastern Indian Ocean sector north of Wilkes Land and the Ross Sea contains evidence of possible ice-rafting during the Early Oligocene, and more definitive evidence of ice-rafting during the Late Oligocene. Early Miocene deep-sea sediments also contain small amounts of ice-rafted debris. There is strong evidence for a significant intensification of ice-rafting during Middle Miocene time, confirming that the increase in O18 in carbonates at that time must in part be related to build-up of the Antarctic ice-sheet.

Evidence for the initiation of glacial ice-rafting, and for the development of sea-ice cover has been found in sediment cores from the central Arctic Ocean spanning early Pliocene (∼4.5 Myr BP) to Recent time. The glacial evidence reported here includes ice-rafted quartz grains, exhibiting glacially formed surface features, and benthic foraminifera endemic to continental shelves in core sediments from the Alpha Rise. The oldest evidence of ice-rafting occurs in sediments palaeomagnetically dated at ∼4.5 Myr BP. Variations in sediment facies indicate varying climatic regimes, and degrees of icecover in the Arctic Ocean since early Pliocene time.

Fossil Mn nodules of Cretaceous age from western Timor exhibit chemical, structural and radioisotope compositions consistent with their being of deep-sea origin. These nodules show characteristics similar to nodules now found at depths of 3,500–5,000 m in the Pacific and Indian Oceans. Slight differences in the fine structure and chemistry of these nodules and modern deep-sea nodules are attributed to diagenetic alteration after uplift of enclosing sediments.

Deep-sea drilling in the Southern Ocean south of Australia and New Zealand shows that the Circum-Antarctic Current developed about 30 million years ago in the middle to late Oligocene when final separation occurred between Antarctica and the continental South Tasman Rise. Australia had commenced drifting northward from Antarctica 20 million years before this.

Oxygen and carbon isotope analysis of planktonic foraminifera and calcareous nannofossils from five box cores from the Venezuela Basin, collected at depths between 3500 and 4800 m, has revealed a detailed paleoglacial and paleoceanographic history for the last 18,000 yrs. Several climatic events have been recorded in these cores, such as shift towards 18 O enriched values at about 13,000 yrs B.P. in planktic foraminifera, which may be related to a sudden re-advance of the Northern Hemisphere ice sheet; and a “tropical fluvial spike” at about 8000 yrs B.P., during the completion of deglaciation. Comparison of carbon isotopes of nannofossils and Globigerinoides sacculifer have revealed cyclical variations, which has been correlated with changes in surface water circulation and productivity in the present-day oceans. Cycles in surface water productivity have been found in the more northerly shallower cores analyzed. These cycles are believed to be related to variations in intensity of upwelling during the last 18,000 yrs in the northern part of the basin. The southern part of the basin had increased upwelling and productivity which resulted in increased carbonate deposition during glacial times. During the present interglacial foraminifera show increased dissolution with depth, but during the glacial period foraminifera are well preserved throughout the basin indicating increased watercolumn turnover rates. Nannofossils are well preserved during the glacial and interglacial periods. Analysis of the relationship of water depth to the preserved isotopic record of these two major calcareous plankton groups indicates that in this region, nannofossils preserve a better record of surface water isotopic variations than planktonic foraminifera.

Since their first recovery from the ocean floor in the 1 870s during the cruises of the H.M.S. Challenger (Murray & Renard 1 891 ), manganese nodules have been found to cover vast portions of the bottoms of the Pacific, Atlantic, and Indian oceans. Despite an enormous amount of research during the ensuing 100 years, the genesis of these deposits remains an enigma. For decades deep-sea manganese nodules were only a scientific curiosity, but economic and political attention has recently been focused on them. In the northeastern equatorial Pacific (Figure I) they have been shown to exhibit copper and nickel concentrations of around 3 wt% and seafloor surface coverages with potential for mineral resource exploitation (Ham­ mond 1974a,b). In response to this economic impetus, the international scientific community has launched major research programs during the last three years. Many of the tech­ nological leaders, including the -United States, Germany, Japan, France, New Zealand, and the USSR, have conducted one or more major scientific cruises to the central Pacific to map the distribution of nodules in relation to seafloor geological features and to recover nodule samples for analysis. In the United States, the princi pal scientific effort on manganese nodules has been the work of the Manganese Nodule Project, funded by the Seabed Assessment Program of the International Decade of Oceanographic Exploration Division (IDOE) of the National Science Foundation (NSF). This project focuses on ferromanganese deposits that are or may be considered potential mineral resources, that is, that contain sufficiently high

Planktonic foraminifera species diversity and ice-rafted sand grains, indication of glaciation during most of Cenozoic, middle Miocene warming trend

Crystallographically oriented etch pits have been observed on quartz sand grains from marine environments, using an electron microscope. Similar features have been produced by etching quartz in the laboratory with hydrofluoric acid and sodium hydroxide. Examination of quartz sand grain surfaces from beaches of different wave intensities along the Atlantic and Gulf coasts of the United States suggests a relationship between the effects of such chemical solution features and mechanical abrasion on sand grains. Sand grains from beaches with low wave activity exhibit oriented etch pits readily attributed to the solution of quartz by sea water. These features are the surface expression of defects within the crystal. Sand grains from beaches with moderate wave energy show a combination of chemical etch features and those phenomena thought by KRINSLEY and TAKAHASHI (1962a) to be caused by grain-to-grain impacts, while grains from high-energy beaches predominantly show impact features. If the correlation shown by the results are valid, the relative number of chemical and mechanical features on sand grains can be used to determine energy conditions along ancient shorelines.

Two independent micropaleontological examinations of core 13-4 of the Eltanin collection, taken at 57°46.2′S and 90°47.6′W show that the lower four meters of the core penetrate Eocene sediments. Electron microscope examination of the quartz grains from the Eocene portion of the core reveal surface features that have been attributed by several authors to glacial action. This evidence suggests that Antarctic glaciation existed during the Eocene.

Observations of the surfaces of manganese nodules from various areas of the Pacific have revealed an entire community of attached encrusting protozoans, including over twenty species of agglutinating foraminifera and at least as many unidentified forms. Preliminary studies indicate that a great abundance and diversity of these organisms are found in the Northeast Equatorial Pacific. The highest density of organisms are associated with the portions of nodules in contact with the sediment-water interface which shows structural evidence for relatively rapid and variable growth rates and concentrations of trace elements. Remains of these organisms have also been detected within internal portions of nodules. Chemical analyses of the tests of such organisms indicate that many forms are responsible for concentrating trace elements found in nodules. However, there is no direct evidence that benthic foraminifera are responsible for copper and nickel enrichment in manganese nodules.

Quantitative scientific determination of the authenticity and age of marble sculpture is an important goal of geo-archaeologists and conservation scientists. Geochemical and petrographic techniques are used here to investigate rock weathering and mineral alterations responsible for the “patina” and alteration layers on marble sculpture. We present oxygen and carbon isotopic, scanning electron microscopic and electron microprobe analyses of both fresh marble and weathering crusts materials from cores taken from Cycladic and Archaic Greek sculptures and from ancient quarries, to evaluate these techniques as indicators of antiquity.Calcitic marbles exhibit an altered weathering crust of variable thickness, where calcite has been recrystallized and interpenetrated with inclusions of iron oxide, clay minerals, gypsum and other authigenic minerals. The thickness and composition of these crusts varies with soil and water chemistry as well as marble density, texture and age.Microprobe analyses indicate trace element gradients from fresh to weathered calcite. Carbon and oxygen isotopes can differentiate between insitu alteration and precipitated carbonate. Dolomitic marbles can exhibit calcitic surficial layers formed by dedolomitization, which can be confirmed by isotopic and microprobe analyses.Analyses of known forgeries, ancient quarry samples and artificially weathered marbles have further documented our criteria and show that the majority of diagnostic geochemical and mineralogical features seen on ancient Greek sculptures cannot be accurately duplicated by artificial means.

Oxygen-18 and carbon-13 analyses of well-preserved calcareous nannofossils have been compared with those of foraminifera contained in Cenozoic cores collected in the Southern Ocean during the Deep Sea Drilling Project. The results indicate that calcareous nannofossils deposit calcium carbonate at or near equilibrium with oceanic surface waters and that they can be used as paleotemperature indicators.

Surface weathering crusts and patinas on ancient Greek and Roman sculpture and other artifacts have been investigated by stable isotope mass spectroscopy, scanning electron microscopy, electron microprobe and PIXE techniques. Analysis of polished cross-sections made from cores taken from fresh interior marble to outer weathered sculpted surfaces on pieces of Early Cycladic Greek to 3 rd. century A.D. Roman age indicate that there are progressive alterations of the carbonate minerals with age. The chemical, isotopic and petrographic characteristics of the weathering crusts vary with marble type, age and weathering environmental histories. These crusts, however, appear to be excellent indicators of antiquity and authenticity.

Although nothing of direct biologic interest was observed in the sample studied, small shaped glass particles and glazed pits resemble objects which elsewhere have been described as fossils. These features, although nonbiological, do bear on processes of lunar weathering and outgassing. The glazed pits are impact features. Fusion of their surfaces released gases. Electron microscopy of the glasses, pits, and angular microfractured mineral grains indicates a prevalence of destructive weathering processes-thermal expansion and contraction, abrasion by by-passing particles, and, of course, impact. ous at room temperature.

Study of 18 Cenozoic South Pacific deep-sea cores indicates an association of glacially derived ice-rafted sands and relatively low planktonic foraminiferal diversity with cooling of the Southern Ocean during the Lower Eocene, upper Middle Eocene, and Oligocene. Increased species diversity and reduction or absence of ice-rafted sands in Lower and Middle Miocene cores indicate a warming trend that ended in the Upper Miocene. Antarctic continental glaciation appears to have prevailed throughout much of the Cenozoic.

Fourteen samples of sand were collected along a range line extending from shore across the shelf near Oso Flaco, California. These samples are representative of coastal dune, beach, modern shelf and possible relict shelf sands present in that area. The samples were sieved to obtain grain size parameters, and surface microtextures of grains from similar size fractions were studied with a scanning electron microscope. Grain size distribution parameters show that anomalously coarse shelf sands are similar to the modern beach and dune sand and are distinct from the finer inner shelf sand. Scanning electron microscope (SEM) examination of the sand grain surface microtextures indicates that the coarse offshore sands have "V" shaped impact pits and etch patterns similar to present day beach and grains, which suggest that they are paleo-beach sands deposited on the outer shelf during a lower stand of sea level.

Carbon and oxygen isotope analysis of 240 m of Upper Cretaceous and Lower Tertiary limestones and marlstones from Zumaya, Spain, has revealed three distinct, negative carbon isotope excursions of up to 2 per mil, occurring both before and during the Cretaceous/Tertiary (K/T) transition. Although diagenesis has affected these rocks to varying degrees during burial and lithification, we believe that these excursions may reflect paleoceanographic changes. Sr/Ca, electron microscopic, and petrographic analysis have been used to assess the type and magnitude of diagenesis, allowing us to distinguish samples with significantly altered isotopic values. Carbon isotopes of rocks at Zumaya exhibit absolute values and ranges similar to semiconsolidated sediments of the same age. Oxygen isotopes of these rocks, however, exhibit a 1–2 per mil or more depletion, defined here as a diagenetic overprint, in comparison with values from semi-consolidated sediments of the same age. Ammonite and inoceramid macrofossils disappear in this section 12.5 and 120 m below the K/T boundary, coincident with two distinct episodes of negative δ13C values. These may reflect localized paleoceanographic or ecological changes. The last and largest of the isotope excursions corresponds with the K/T boundary marl and mass extinctions of calcareous plankton. The K/T boundary carbon isotope excursion is one of three that took place during the last 1 million years of the Cretaceous, each one possibly being associated with biotic changes in the oceanic realm. The K/T boundary excursion coincides with iridium concentration and spherules of unidentified origin, perhaps indicating that paleoceanographic change coincided with either extraterrestrial impacts or volcanic events that amplified their effects and accelerated biotic changes during times of stressed oceanic ecosystems.

The hypothesis of Cretaceous-Tertiary (K-T) boundary impact on Yucatan, Mexico, predicts that nearby sites should show evidence of proximal impact ejecta and disturbance by giant waves. An outcrop along the Arroyo el Mimbral in northeastern Mexico contains a layered clastic unit up to 3 m thick that interrupts a biostratigraphically complete pelagic-marl sequence deposited at more than 400 m water depth. The marls were found to be unsuitable for determining magnetostratigraphy, but foraminiferal biostratigraphy places the clastic unit precisely at the K-T boundary. We interpret this clastic unit as the deposit of a megawave or tsunami produced by an extraterrestrial impact. The clastic unit comprises three main subunits. (1) The basal "spherule bed" contains glass in the form of tektites and microtektites, glass spherules replaced by chlorite-smectite and calcite, and quartz grains showing probable shock features. This bed is interpreted as a channelized deposit of proximal ejecta. (2) A set of lenticular, massive, graded "laminated beds" contains intraclasts and abundant plant debris, and may be the result of megawave backwash that carried coarse debris from shallow parts of the continental margin into deeper water. (3) At the top, several thin "ripple beds" composed of fine sand are separated by clay drapes; they are interpreted as deposits of oscillating currents, perhaps a seiche. An iridium anomaly (921 +/- 23 pg/g) is observed at the top of the ripple beds. Our observations at the Mimbral locality support the hypothesis of a K-T impact on nearby Yucatan.

BROWN1 has drawn attention to the occurrence of features of “glacial origin” on sand grains from freshly weathered granite, from beaches, and from streams, all presumably lacking evidence of previous glacial history. We would like to clarify certain misleading statements presented by Brown1, not with the purpose of discrediting her findings but rather to argue with the interpretation of her data with respect to previously published literature on this subject. Krinsley and Donahue's transmission microscope work2 of 1968, referred to by Brown, has been greatly expanded on by much detailed work since the use of the scanning electron microscope to examine sand grain surface textures became widespread3–9. The statement made by Brown, quoting Krinsley and Donahue2 “that an assemblage of textures should characterize any one abrasive process, and that no single feature can be considered completely diagnostic,” was modified by Margolis and Kennett4 to read “… no single surface feature can itself be used to identify the origin of a sand grain, but rather that certain combinations of features are highly diagnostic when statistically significant percentages of the grains in the sample are examined”. With regard to Brown's statements on features of glacial origin Margolis and Kennett4 have written: “Features that in previous studies have been individually regarded as diagnostic of glacial origin such as large conchoidal fractures and breakage blocks, are also occasionally found on grains from high turbulence beaches and also occasionally on desert sands. When combinations of surface features are examined statistically, however, glacially derived sand grains exhibit unique combinations of characteristics”3,6. The point here is that the technique had advanced beyond presenting individual photographs as evidence of the history of a sand, and now involves a more quantitative treatment of data.

Oxygen and carbon isotope analysis of Upper Maastrichtian and lowermost Danian pelagic limestones and marls from Zumaya, Spain indicates that several major isotopic excursions occurred both before and during the Cretaceousl Tertiary (KIT) boundary event. Each of these excursions involved a synchronous negative shift in 8180 and 813C of approximately 2 per mil. The isotopic excursion that occurs at the Cretaceousl Tertiary boundary has previously been interpreted by most workers in terms of biologic and oceanographic changes associated with an extraterrestrial impact. However, our data indicate that this excursion is not significantly different from several others that preceed it, suggesting that the boundary excursion is not a unique event. These excursions are interpreted as indicators of episodic warming events of several 100,000 years duration with associated decreases in upwel

Backscatter scanning electron microscopy (BSEM) was used to evaluate microdiagenesis in biogenic carbonates of the Pungo River Formation, a phosphate-bearing, Miocene, continental shelf deposit in North Carolina. Results of this new high-resolution technique correlate well to the downsection δ 18 O variation of three species of benthic foraminifera. This technique is useful in the evaluation of diagenesis prior to isotopic analysis for paleoclimatic and paleoceanographic purposes.

Sediment and microfossils from three subantarctic deep-sea cores recovered in the Southeast Indian Ocean have revealed a detailed climatic and glacial history for the Pliocene Epoch. Two cores contain sediment sequences that overlap and are of middle Matuyama through Gilbert a age, and one core extends into sediment that was deposited at the beginning of the Gilbert epoch (5.1 m.y. B.P.). Quartz grains that are >62 µm in size are found throughout the cores, and examination of their surfaces by scanning electron microscopy reveals that most of them are of either primary glacial or glacial marine origin. The remaining grains have features similar to grains transported mainly in a subaqueous environment. Glacially derived quartz grains become more abundant in sediment younger than the Gilbert a event; this trend continues in sediment of Gauss through middle Matuyama age. The greater abundance of ice-rafted quartz grains in sediment younger than the Gilbert a event may reflect a major late Cenozoic increase in antarctic glaciation. Radiolarian faunas from sediment intervals of Gauss age indicate temperatures comparable to modern surface-water temperatures at the same latitudes. Warmer water faunas, however, are found in sediment of early Matuyama and late Gauss age, whereas cooler water faunas are found in middle Matuyama and upper Gilbert sediment. The warmest interval occurs directly below sediment of Gilbert c age. This interval, which is significantly warmer than the present-day surface-water temperatures at the same latitude, is followed by a marked cooling between the Gilbert b and a events and precedes the increase in glacially derived quartz grains during the Gilbert a event. There are indications that antarctic glaciation preceded major cooling of the Southern Ocean and contributed to the long-term world-wide cooling postulated for late Cenozoic time. The marked increase in ice-rafted sediment during late Gilbert time may be related to an increase in antarctic glaciation perhaps to the point where permanent ice shelves developed, the formation of which may have greatly increased antarctic bottom-water activity in the circumpolar region.

Investigation of surface features on quartz sand grains of eolian origin from 20 desert and coastal dune environments from around the world reveals that chemical solution and redeposition of silica by the action of desert dew along with mechanical wind abrasion causes frosting and rounding of sand grains. Wind-induced grain impacts create small-scale fractures that are related to wind velocity and moisture as well as the roundness, degree of polish, and size of the impacting grains. This fracture pattern, which has been reproduced experimentally by simulating wind abrasion, is most pronounced on projections from the surface of the grains. Examination with a scanning electron microscope shows that this pattern consists of minute upturned plates of quartz that overlap each other and appear to be dipping in a direction possibly consistent with internal crystallographic planes. The close spacing of these fracture plates is responsible for the frosted appearance of many desert sands. These irregular fractured plates have a high chemical potential and will dissolve under favorable physicochemical conditions. This dissolved silica can be precipitated elsewhere as an amorphous layer on grain surfaces when the solution evaporates, resulting in a progressive rounding of sharp edges and subduing of irregular mechanical fracture patterns by transfer of minute amounts of silica. The occurrence, morphology, and distribution of diagnostic mechanical and chemical surface features allows differentiation between tropical desert sands, coastal dune sands, and periglacial sands. Closely spaced chemical etch pits formed on sand grains by “abrasion solution,” or during diagenesis, when grains are exposed to high p H solutions, also can result in a frosted appearance. Defrosting can be accomplished by addition of a thin amorphous layer of silica to the grain9s surface, or by polishing during turbulent subaqueous transport.

Examination of ferromanganese nodules and micronodules from the Pacific and Indian Oceans by scanning electron microscopy has revealed previously undescribed microlaminations ranging in size from less than 0.25 µm to greater than 10 µm, which appear to be the smallest structural units in manganese nodules resolvable with the SEM. These microlaminations are believed to be primary structures, as they are laterally continuous around the nodule and remain uniform in thickness in both straight and cuspate growth regions. Theories for the origin of microlaminations include short-term changes or discontinuities in nodule growth rate (possibly produced by fluctuations in bottom currents) and recrystallization or ordering phenomena associated with different mineral phases (oxidation states) of manganese/iron hydroxides.

A suite of orange-peel grab sediment samples collected during Deep Freeze II from the Antarctic continental shelf of the Weddell Sea contained several well-sorted sand samples. These were collected in 1957 from Berkner Bank in water depths of 282 to 300 m. Samples from greater and lesser depths show poorer sorting as well as differences in other size parameters (Fig. 1). The well-sorted sands include both striated and fractured quartz grains with a considerable degree of polish. Photographs and electron micrographs of grain surfaces and replicas suggest that entire grain surfaces of both the fractured surface morphology and the polished surface have undergone quartz dissolution suggesting an extensive period of exposure to seawater. Detailed studies show features characteristic of both beach and dune sand abrasion overlying glacial features. A variable amount of rock flour is present in all samples, but is least abundant in the 290 ± 10m depth samples. The samples from depths both greater and less than 290 ± 10 m appear to be typical of periglacial marine sediments with a poorly sorted heterogeneous assortment of minerals and rock fragments. The 290 ± 10 m samples appear strikingly different and strongly resemble quartz dune or beach sands. The very good sorting, size, and surface features suggest that these are dune sands. These data indicate that Berkner Bank may have been exposed at the surface during an interglacial period when the Antarctic land surface stood approximately 300 m higher with respect to sea level than it does today.

Examination of Holocene Bahamian ooelites by scanning electron and light microscopy has revealed the morphology and orientation of aragonite crystals in the lamellar ooelitic envelope, and their modification by the boring activities of endolithic algae. The voids produced by these algae are found in progressive stages of being lined and filled with precipitated microcrystalline aragonite, which is similar to the process of micrite envelope formation in molluscan and other skeletal carbonate grains.