LESSONS FROM A FEASIBILITY STUDY FOR COMPUTER MODELS OF COAL-BEARING DELTAS

A computer-generated model of a coal-bearing delta would be desirable if it included enough detail to reproduce the cyclical nature of the sediments. At the present stage of development of computers, and with the present state of knowledge of the quantitative aspects of transportation and sedimentation, it is not yet possible to set up such a model. However, the logical arrangement in a flow-diagram of the processes and parameters involved in delta formation strongly suggests that cyclical sedimentation can occur without the need for an external cyclical cause, such as tectonic or climatic oscillations. Attempts to provide for appropriate checks of a computer model bring out overall regularities in the assemblages of cyclic types in three different coal basins.     

Zinc content in otoliths of mackerel from the Aegean

The zinc content in otoliths of the mackerel (Scomber japonicus colias) has been determined by instrumental neutron activation analysis. Six groups each of twelve specimens of the same age selected from three areas of the Aegean sea have been analysed. The zinc content was found to be a linear function of the age and body length.     

The Danube River: an emerging regional bondDie donau: Eine bandregion der zukunftLe Danube: Un lien régional en formation

The Danube River, Europe's longest west of the Soviet Union, connects central and southeastern Europe. It flows through areas of great diversity of climates and land forms. Navigation has, in fact, been hindered by fluctuating water levels, ice, and defiles. Primarily for political reasons the river, prior to the middle of the 20th century, had never been a viable link of transportation and communication. Since the second world war, however, effective internationalization of the river, extensive navigation improvement projects, construction of dams and hydroelectric power plants, and greatly accelerated economic development in the Danube River basin in general, all point toward the river becoming one of Europe's principal axes and regional bonds.     

The Late Cenozoic Eridanos delta system in the Southern North Sea Basin: a climate signal in sediment supply?

ABSTRACT The Eridanos fluvio‐deltaic system, draining most of north‐western Europe, developed during the Late Cenozoic as a result of simultaneous uplift of the Fennoscandian shield and accelerated subsidence in the North Sea Basin. This seismo‐stratigraphic study aims to reconstruct the large‐scale depositional architecture of the deltaic portion of the basin fill and relate it to external controls. A total of 27 units have been recognized. They comprise over 62×10³ km³ in the Southern North Sea Basin alone, and have an average delta surface area of 28×10³ km², which suggests that the size of the drainage area was about 1.1×10⁶ km². Water depth in the depocentre is seen to decrease systematically over time. This trend is interrupted by a deepening phase between 6.5 and 4.5 Ma that can be correlated with the simultaneous occurrence of increased uplift of the Fennoscandian shield, increased subsidence of the Southern North Sea Basin, and a long‐term eustatic highstand. All these observations point to a tectonic control on long‐term average rates of accommodation and supply. Controls on short‐term variations are inferred from variations in rates of sediment supply and bifurcation of the delta channel network. Both rates were initially low under warm, moist, relatively stable climate conditions. The straight wave‐dominated delta front gradually developed into a lobate fluvial‐dominated delta front. Two high‐amplitude sea‐level falls affected the Pliocene units, which are characterized by widespread delta‐front failures. Changes in relative sea level and climate became more frequent from the late Pliocene onward, as the system experienced the effects of glacial–interglacial transitions. Peaks in sedimentation and bifurcation rates were coeval with cold (glacial) conditions. The positive correlation between rates of supply and bifurcation on the one hand, and climate proxies (pollen and δ¹⁸O records) on the other hand is highly significant. The evidence presented in this study convincingly demonstrates the control of climate on time‐averaged sediment supply and channel‐network characteristics, despite the expected nonuniformity and time lags in system response. The presence of a clearly discernible climate signal in time‐averaged sediment supply illustrates the usefulness of integrated seismo‐stratigraphic studies for basin‐wide analysis of delta evolution on geological time scales.