Stanley V. Margolis

Development of the Circum-Antarctic Current

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 Isotopes from Calcareous Nannofossils as Paleoceanographic Indicators

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.

Oxygen and carbon isotopes of Recent calcareous nannofossils as paleoceanographic indicators

Abstract 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 worlds 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.

Biogenic Influence on Growth of Manganese Nodules

ABSTRACT 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.

Cenozoic and Late Mesozoic paleoceanographic and paleoglacial history recorded in circum-Antarctic deep-sea sediments☆

Abstract 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 worlds 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.

Pliocene Climatic and Glacial History of Antarctica As Revealed by Southeast Indian Ocean Deep-Sea Cores

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.

Fireworks pollution and health

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.

Microlaminations in Marine Manganese Nodules as Revealed by Scanning Electron Microscopy

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.

Fossil manganese nodules from Timor: Geochemical and radiochemical evidence for deep-sea origin☆

Abstract 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.