Manganese nodules and micronodules from a series of deep-sea and shelf environments displaying a range of morphological features were selected for detailed examination by scanning electron microscopy (SEM). A summary of the morphological and petrographic characteristics of these nodules are presented. They are representative of areas in the Philippine Sea, the Tasman Sea and the Indian-Antarctic Ridge.

The Carnegie Ridge is a linear, aseismic, submarine ridge lying between the Galapagos Islands and the coast of South America. Surface ship, near bottom, and grain size studies from the saddle have been used to delineate the present geological environment and history of the ridge. Structurally the Carnegie Ridge is rather simple in profile, being bounded by east-west trending scarps which give the ridge a block-faulted appearance. Acoustic basement over the ridge appears smooth on...

Local adaptation is assumed to occur under limited gene flow. However, habitat-matching theory predicts dispersal should favour rather than hinder local adaptation when individuals selectively disperse towards habitats maximizing their performance. We provide experimental evidence that local adaptation to the upper margin of a species' thermal niche is favoured by dispersal with habitat choice, while hindered under random dispersal. Our study challenges the idea that high gene flow precludes local adaptation, and provides unique experimental...

Due to the high sensitivity of southern Africa to climate change, a reliable understanding of its hydrological system is crucial. Recent studies of the regional climatic system have revealed a highly complex interplay of forcing factors on precipitation regimes. This includes the influence of the tropical easterlies, the strength of the southern hemispheric westerlies as well as sea surface temperatures along the coast of the subcontinent. However, very few marine records have been available in...

he proposed mining of ferromanganese deposits from the deep sea will affect benthic and pelagic environments depending to a great extent on the method of nodule retrieval and separation. Three basic deep-ocean mining systems have been proposed, each of which will effect the removal under varying conditions of water, sediment and nodules from the ocean floor. This report summarizes existing oceanographhic information on potential manganese nodule mining areas at the date of publication and presents...

In addition to the large nodules of manganese dioxide that pave some regions of the ocean floor, much finely divided (<1 mm) manganese dioxide occurs within the sediment column. The fine material is a good deal more widely distributed than the large nodules, but because of the almost microscopic size of the finely divided manganese oxide, it is easily overlooked. However, the micronodules and specks of manganese oxide on the tests of forarainifera are conspicuous...

This study uses stable noble gases' (He, Ne, Ar, Kr, Xe) volume fractions and isotopic ratios from Antrim Shale natural gas to assess compositional variability and vertical fluid migration within this reservoir, in addition to distinguishing between the presence of thermogenic versus biogenic methane. R/Ra values, where R is the measured 3He/4He ratio and Ra is the atmospheric value of 1.384 ± 0.013 × 10**- 6, vary from 0.01 to 0.34 suggesting a largely dominant...