Description and composition iron-manganese concretions from the Pacific

One the most interesting features of ocean sedimentation is the manganese formations on the surface of the ocean floor in some areas. These are especially widespread in the Pacific Ocean as concretions, grains, and crusts on rock fragments and bedrock outcrops. Iron-manganese concretions are the most abundant as they completely cover about 10% of the bottom of the Pacific Ocean where there are ore concentrations. The concretions occupy from 20-50% of the bottom and up to 80-90% on separate submarine rises. Such concretions are found in different types of bottom deposits, from abyssal red clays to terrigenous muds, but they occur most widely in red clays and quite often in carbonate muds. Their shape and their dimensions are very diverse and change from place to place, from station to station, varying from 0.5-20 cm. They may be oval, globular, reniform, or slaggy and often they are fiat or isometric concretions of an indefinite shape. The concretions generally have nuclei of pumice, basalt fragments, clayey and tuffaceous material, sharks' teeth, whale ossicles, and fossil sponges. Most concretions have concentric layers, combined with dendritic ramifications of iron and manganese oxides.

(Table 1) Sample description and tetrapyrrole pigment yield at DSDP Leg 60 Holes

In order to provide a better understanding of the fate of sedimentary chlorophyll and chlorophyll degradation products in all kinds of environments, we have recently expanded our studies to include examination of sediments returned from Legs which are not rich in organic matter, nor are even primarily biogenic. Eight core samples from the Mariana Basin and Trench, obtained from DSDP Leg 60, were analyzed for products of chlorophyll diagenesis. To date, the sediment samples from the South Philippine Sea have been the most organically barren examined. Through elimination of the bias of examining only sediments rich in organic matter, we hope that the fate of chlorophyllous material on a more global scale will eventually be elucidated.

Soil organic carbon storage and soil properties for 50 soil profiles in the Lena River Delta including land form description and map

To project the future development of the soil organic carbon (SOC) storage in permafrost environments, the spatial and vertical distribution of key soil properties and their landscape controls needs to be understood. This article reports findings from the Arctic Lena River Delta where we sampled 50 soil pedons. These were classified according to the U.S.D.A. Soil Taxonomy and fall mostly into the Gelisol soil order used for permafrost-affected soils. Soil profiles have been sampled for the active layer (mean depth 58±10 cm) and the upper permafrost to one meter depth. We analyze SOC stocks and key soil properties, i.e. C%, N%, C/N, bulk density, visible ice and water content. These are compared for different landscape groupings of pedons according to geomorphology, soil and land cover and for different vertical depth increments. High vertical resolution plots are used to understand soil development. These show that SOC storage can be highly variable with depth. We recommend the treatment of permafrost-affected soils according to subdivisions into: the surface organic layer, mineral subsoil in the active layer, organic enriched cryoturbated or buried horizons and the mineral subsoil in the permafrost. The major geomorphological units of a subregion of the Lena River Delta were mapped with a land form classification using a data-fusion approach of optical satellite imagery and digital elevation data to upscale SOC storage. Landscape mean SOC storage is estimated to 19.2±2.0 kg C/m**2. Our results show that the geomorphological setting explains more soil variability than soil taxonomy classes or vegetation cover. The soils from the oldest, Pleistocene aged, unit of the delta store the highest amount of SOC per m**2 followed by the Holocene river terrace. The Pleistocene terrace affected by thermal-degradation, the recent floodplain and bare alluvial sediments store considerably less SOC in descending order.

(Table 1) Description and tetrapyrrole-pigment yield at DSDP Leg 58 Holes

Nineteen core samples from the Shikoku Basin and the Daito Ridge and Basin province of the northwest Philippine Sea, obtained from DSDP Leg 58, were examined for products of chlorophyll diagenesis; we aimed at gaining a better understanding of the very early diagenetic history of sedimentary chlorophyll. We choose samples which, a priori, would allow isolation of tetrapyrrole pigments characteristic of (destructive) diagenesis modes. Studies of Japan Trench sediments (Louda et al., 1980; Baker and Louda, 1980) showed well the interplay of two main diagenesis schemes: anoxic preservation and oxic destruction. The results reported herein are a product of a preliminary investigation on sediments of scant organic matter content, which yielded limited tetrapyrrole pigment.

Description and analyses of manganese nodules from the South-Western Pacific

Manganese nodules from the Campbell Plateau and Macquarie Ridge have been chemically analysed and their compositions compared with other Pacific nodules. No significant differences in composition are apparent. Foraminifera from nodule nucleii are late Tertiary or Quaternary, indicating the late geological formation of manganese nodules in this region. Nodule formation may be related to late Tertiary or Quaternary submarine volcanism.

New Observations of Balmer Continuum Flux in Solar Flares:Instrument Description and First Results

Increase in the Balmer continuum radiation during solar flares was predicted by various authors, but has never been firmly confirmed observationally using ground-based slit spectrographs. Here we describe a new post-focal instrument, the image selector, with which the Balmer continuum flux can be measured from the whole flare area, in analogy to successful detections of flaring dMe stars. The system was developed and put into operation at the horizontal solar telescope HSFA2 of the Ondřejov Observatory. We measure the total flux by a fast spectrometer from a limited but well-defined region on the solar disk. Using a system of diaphragms, the disturbing contribution of a bright solar disk can be eliminated as much as possible. Light curves of the measured flux in the spectral range 350 – 440 nm are processed, together with the Hα images of the flaring area delimited by the appropriate diaphragm. The spectral flux data are flat-fielded, calibrated, and processed to be compared with model predictions. Our analysis of the data proves that the described device is sufficiently sensitive to detect variations in the Balmer continuum during solar flares. Assuming that the Balmer-continuum kernels have at least a similar size as those visible in Hα, we find the flux increase in the Balmer continuum to reach 230 – 550 % of the quiet continuum during the observed X-class flare. We also found temporal changes in the Balmer continuum flux starting well before the onset of the flare in Hα.

A vision for Southeast Asia

Participants at a recent workshop in Bali sought to develop a draft Southeast Asian Regional Plan of Action (RPOA) to support the implementation of the SSF Guidelines in the region.

Zui xin dong nan ya quan tu = Southeast Asia map /

Relief shown by spot heights.

Histoire physique, naturelle, et politique de Madagascar / par Alfred Grandidier.

v. 30-36 Text

Histoire physique, naturelle, et politique de Madagascar / par Alfred Grandidier.

v.39:Text [Mousses] (1915)

Histoire physique, naturelle, et politique de Madagascar / par Alfred Grandidier.

v.39:[Plates] [Mousses] (1915)

Histoire physique, naturelle, et politique de Madagascar / par Alfred Grandidier.

v.27:pt.1 [Myriapodes] (1902) Text

The three voyages of Captain James Cook round the world ...

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