Description and chemical composition of ferromanganese deposits from Oneida Lake, New York

Saucer-shaped iron-manganese crusts occur adjacent to gravel shoal areas in Oneida lake in central New York. The crusts usually have a crude concentric banding owing to an alternation of orange, iron-rich layers and black, iron-poor layers. Materials from both types of layers are x-ray amorphous. The Oneida lake crusts, like most other freshwater manganese nodules, contain about the same Mn concentration as marine manganese nodules, but are usually higher in Fe and lower in trace metals than their marine equivalents. Although Fe and Mn may be precipitating directly from the lake water, it is more likely that the oxidate crusts are the result of precipitation of Fe and Mn when reduced sediment pore water comes in contact with well oxygenated bottom waters. Organisms, particularly bacteria, may play a role in the formation of the crusts, but to date no evidence of this has been found.

Composition of post-Jurassic deposits from the Northwest Pacific and the Galapagos Rift, data of DSDP Legs 62, 65, and 70

The monogragh contains results of mineralogicai and geochemical studies of Mesozoic and Cenozoic deposits from the Pacific Ocean collected during Deep Sea Drilling Project. Special attention is paid on the aspects of geochemical history of post-Jurassic sedimentation in the central part of the Northwest Pacific, detailed characteristics of the main stages of sedimentary evolution are given: Early Cretaceons (protooceanic), Late Cretaceons (transitional) and Cenozoic (oceanic). Results of mineralogical and geochemical studies of hydrothermal deposits from the Galapagos Rift are given as well.

Grain size, mineral and chemical compositions of modern deposits fron the northern Caspian Sea and the Volga River delta

Comprehensive investigations revealed that modern deposits in the northern Caspian Sea involve terrigenous sands and aleurites with admixture of detritus and intact bivalve shells, including coquina. Generally, these deposits overlay dark grayish viscous clays. Similar geological situation occurs in the Volga River delta; however, local deposits are much poorer in biogenic constituents. Illite prevails among clay minerals. In coarse aleurite fraction (0.100-0.050 mm) heavy transparent minerals are represented mostly by epidotes, while light minerals - mostly by quartz and feldspars. Sedimentary material in the Volga River delta is far from completely differentiated into fractions due to abundant terrigenous inflows. Comparatively better grading of sediments from the northern Caspian Sea is due to additional factors such as bottom currents and storms. When passing from the Volga River delta to the northern Caspian Sea, sediments are enriched in rare earth elements (except Eu), Ca, Au, Ni, Se, Ag, As, and Sr, but depleted in Na, Rb, Cs, K, Ba, Fe, Cr, Co, Sc, Br, Zr, ??, U, and Th. Concentrations of Zn remain almost unchanged. Sedimentation rates and types of recent deposits in the northern Caspian Sea are governed mainly by abundant runoff of the Volga River.

Beryllium-10 and aluminium-26 concentration and production rates in glacial deposits from the Quartermain Mountains

Many glacial deposits in the Quartermain Mountains, Antarctica present two apparent contradictions regarding the degradation of unconsolidated deposits. The glacial deposits are up to millions of years old, yet they have maintained their meter-scale morphology despite the fact that bedrock and regolith erosion rates in the Quartermain Mountains have been measured at 0.1-4.0 m/Ma. Additionally, ground ice persists in some Miocene-aged soils in the Quartermain Mountains even though modeled and measured sublimation rates of ice in Antarctic soils suggest that without any recharge mechanisms ground ice should sublimate in the upper few meters of soil on the order of 10**3 to 10**5 years. This paper presents results from using the concentration of cosmogenic nuclides beryllium-10 (10Be) and aluminum-26 (26Al) in bulk sediment samples from depth profiles of three glacial deposits in the Quartermain Mountains. The measured nuclide concentrations are lower than expected for the known ages of the deposits, erosion alone does not always explain these concentrations, and deflation of the tills by the sublimation of ice coupled with erosion of the overlying till can explain some of the nuclide concentration profiles. The degradation rates that best match the data range 0.7-12 m/Ma for sublimation of ice with initial debris concentrations ranging 12-45% and erosion of the overlying till at rates of 0.4-1.2 m/Ma. Overturning of the tills by cryoturbation, vertical mixing, or soil creep is not indicated by the cosmogenic nuclide profiles, and degradation appears to be limited to within a few centimeters of the surface. Erosion of these tills without vertical mixing may partially explain how some glacial deposits in the Quartermain Mountains maintain their morphology and contain ground ice close to the surface for millions of years.

Sedimentology and geochemistry of ODP Leg 129 siliceous deposits

Siliceous deposits drilled on Ocean Drilling Program Leg 129 accumulated within a few degrees of the equator during the Jurassic through early Tertiary, as constrained by paleomagnetic data. During the Jurassic and Early Cretaceous, radiolarian ooze, mixed with a minor amount of pelagic clay, was deposited near the equator, and overall accumulation rates were moderate to low. At a smaller scale, in more detail, periods of relatively higher accumulation rates alternated with periods of very low accumulation rates. Higher rates are represented by radiolarite and limestone; lower rates are represented by radiolarian claystone. Our limited data from Leg 129 suggests that accumulation of biogenic deposits was not symmetrical about the equator or consistent over time. In the Jurassic, sedimentation was siliceous; in the Cretaceous there was significant calcareous deposition; in the Tertiary claystone indicates significantly lower accumulation rates at least the northern part of the equatorial zone. Accumulation rates for Leg 129 deposits in the Cretaceous were higher in the southern part of the equatorial zone than in the northern part, and the southern side of this high productivity zone extended to approximately 15°S, while the northern side extended only to about 5°N. Accumulation rates are influenced by relative contributions from various sediment sources. Several elements and element ratios are useful for discriminating sedimentary sources for the equatorial depositional environments. Silica partitioning calculations indicate that silica is dominantly of biogenic origin, with a detrital component in the volcaniclastic turbidite units, and a small hydrothermal component in the basal sediments on spreading ridge basement of Jurassic age at Site 801. Iron in Leg 129 sediments is dominantly of detrital origin, highest in the volcaniclastic units, with a minor hydrothermal component in the basal sediments at Site 801. Manganese concentrations are highest in the units with the lowest accumulation rates. Fe/Mn ratios are >3 in all units, indicating negligible hydrothermal influence. Magnesium and aluminum concentrations are highest in the volcaniclastic units and in the basal sediments at Site 801. Phosphorous is very low in abundance and may be detrital, derived from fish parts. Boron is virtually absent, as is typical of deep-water deposits. Rare earth element concentrations are slightly higher in the volcaniclastic deposits, suggesting a detrital source, and lower in the rest of the lithologic units. Rare earth element abundances are also low relative to "average shale." Rare earth element patterns indicate all samples are light rare earth element enriched. Siliceous deposits in the volcaniclastic units have patterns which lack a cerium anomaly, suggesting some input of rare earth elements from a detrital source; most other units have a distinct negative Ce anomaly similar to seawater, suggesting a seawater source, through adsorption either onto biogenic tests or incorporation into authigenic minerals for Ce in these units. The Al/(Al + Fe + Mn) ratio indicates that there is some detrital component in all the units sampled. This ratio plotted against Fe/Ti shows that all samples plot near the detrital and basalt end-members, except for the basal samples from Site 801, which show a clear trend toward the hydrothermal end-member. The results of these plots and the association of high Fe with high Mg and Al indicate the detrital component is dominantly volcaniclastic, but the presence of potassium in some samples suggests some terrigenous material may also be present, most likely in the form of eolian clay. On Al-Fe-Mn ternary plots, samples from all three sites show a trend from biogenic ooze at the top of the section downhole to oceanic basalt. On Si-Fe-Mn ternary plots, the samples from all three sites fall on a trend between equatorial mid-ocean spreading ridges and north Pacific red clay. Copper-barium ratios show units that have low accumulation rates plot in the authigenic field, and radiolarite and limestone samples that have high accumulation rates fall in the biogenic field.

Mineralogy and geochemistry of sedimentary deposits at DSDP Leg 55 Holes

The four holes (including a re-entry hole) drilled at Site 433 allow determination of the sedimentary sequence of Suiko Seamount in the Emperor chain. The holes are in a small graben basin situated within a lateral lagoon on the seamount. The sedimentary deposits range from the Paleocene to the upper Pliocene and are not uniform and continuous. A major hiatus exists at the top of the lower Eocene reef sediment, below the lower and upper Miocene pelagic sediments. The depositional history and succession of environments are shown by mineralogical and geochemical changes in the sediments.

Annotated record of the detailed examination of Mn deposits from SESAM cruise stations

The cores and dredges described at this site were taken on the SESAM cruise from 30 April until 10 June 1976 by the Muséum National d'Histoire Naturelle from the R/V Marion Dufresne. A total of 55 cores, dredges and camera stations were recovered and are available at MNHN for sampling and study.

Description of manganese deposits collected by R/V "Jean Charcot" during its EQUAMARGE II expedition in the Equatorial Atlantic

During the Equamarge II cruise (February 4 to March 21, 1988), on board the R. V. "Jean Charcot", 12.500 kms of continuous geophysical profiling have been recorded along three sectors of the Equatorial Atlantic. Two segments ofthe West African transform margin have been intensively surveyed off Guinea and off Ivory Coast and Ghana. The active Romanche fracture zone has been surveyed in details on a distance of about 100 kms. These data (multibeam bathymetry, continuous seismic profiling, magnetism and gravity) have been supplemented by 16 geological stations (dredging and coring). This report gives a synthetic review of the onboard analysis and allows to better understand the geological structures of the three surveyed areas.