High Waterfall Research Articles

The Maliau Basin, Sabah: Geology and tectonic setting

A field survey of the eastern half of the Maliau Basin established the presence of several good quality coal seams in the dominant mudstone sequence of the Early to Middle Miocene Tanjung Formation. Although volumetrically minor, the several metres thick sublitharenite beds dominate the landscape forming high waterfalls, concen­ tric cuesta and other ridges with dipslopes inclined into the basin. Sandstone channel fills are common. Sedimentary current indicators including current ripple marks, tabular and trough cross beds, and lineation of carbonised plant fragments indicate that the Il).ajority of currents was towards northeast. The presence of coal, dominant mudstone, marine body and trace fossils suggest that the Tanjung Formation developed in low-energy environ­ ment, probably in wide tidal flats. Except for one locality exposing open folds, the beds dip uniformly and gently inward forming an eccentric basinal structure associated with normal faulting. These phenomena could have only been caused by gravitational subsi­ dence without tectonic compression. The northern boundary strike ridge intercepts internal strike ridges at oblique angles. This pattern and the off-centre position of the youngest beds suggest that the Maliau Basin during the deposition of the Tanjung Formation became progressively narrower while its depocentre migrated towards the south rim. The structural basins contairiingthe Tanjung Formation and time-equivalent Kapilit Formation are arranged in northeast and southeast rows; the Maliau basin occupying the junction of these two directions. Geologically the Maliau Basin is the landward extension of the Tarakan Trough and is at least partially floored by melange rocks of the Kinabalu Suture Zone. Subsidence ofthis basin and other early-middle Miocene basins of east Sabah began when the East Sabah Terrane stopped drifting south and isostatic readjustment sank the denser ophiolitic basement of the suture zone.

Geomorphology of the Gran Sabana, Guayana Shield, southeastern Venezuela

The forms of the Gran Sabana have been developed mainly on rocks of the gently folded Precambrian Roraima Group, a sequence of quartzites and siliceous conglomerates, with intercalated jasper, chert, arkose, siltstone, and shale, locally intruded by diabase dikes and sills. Two planation surfaces are preserved on the Gran Sabana: the Auyán-tepui (2000–2900 m elevation) and the Wonken (900–1200 m) Surfaces, with a speculative Mesozoic initial age; they are still extending. Table mountains dominate the landscape. They comprise pediments, foothills, precipitous scarps hundreds of meters high, a rim, and a flattish summit. The table-mountain topography is controlled by joint systems; water percolates along joints and bedding planes, dissolves the siliceous cement, the quartzite disaggregates, and large blocks are isolated and collapse, accumulating at the foot of the scarps and on top of the table-mountain summits. The percolating water forms large and intricate cave systems, which frequently emerge in the scarp zone as high waterfalls. These mark the lowest level of erosion of the table mountains. Karstic structures are prominent in the summit zone. The evolution of the table-mountain topography has been controlled by a combination of tectonic, structural, stratigraphic, climatic, and temporal factors.

Heat exchanges in muddy intertidal sediments: Chichester Harbour, West Sussex, England

Temperature observations made from a lightweight tower assembly in Chichester Harbour, West Sussex, demonstrate that marked changes in temperature at intertidal mud surfaces occur on a flow tide. The magnitude and direction of these changes are dependent on the external atmospheric and marine conditions, and on the timing of tidal inundation. Calculated heat exchange values for the 3h prior to high water fall into four distinct timing zones. There is a relationship between thermal stress, measured as rate of change of temperature with time, and time of high water. Mud surfaces are net receivers of heat energy from inundating water layers.

Plaza Central Peachtree. Atlanta-(EE.UU.)

This 70-storey hotel has been constructed to meet the requirements of the city of Atlanta which needed a building with a sufficient room capacity and adequate premises for Conventions. On a structure of reinforced concrete which serves as a base and in which the common areas are situated rises a big cylindric tower, covered with coloured glass and which contains the 1.100 rooms. 230 m above ground level, the construction is crowned with a roof top cocktail lounge and a revolving restaurant with a splendid view of the city. Among the most noteworthy characteristics of this hotel is the elegantly decorated entrance hall —atrium shaped and 7 storeys high— with a pond in the centre. Further premises worth mentioning in view of their design and dimensions are the great ball room, coffee-shops and luxurious restaurants, one of which is planned in different levels and in which the most impressive feature is a 30 m high waterfall.