Review: Zeitschrift für Geomorphologie 52/3 top ↑
Three papers discuss weathering processes and long-term landscape evolution. The paper ‘Fission-track datings and geomorphic evidences for long-term stability in the Central Cordillera highlands, Colombia’ (p. 1–16) by Toro, Hermelin, Schwabe, Posada, Silva & Poupeau shows that some areas in the northern Central Cordillera plateaus of Colombia underwent little erosion since more than 5 million years ago. The ages obtained from fissiontrack dating of zircons of tephra-derived soils and colluvium (?) are interpreted as evidence for the absence of ‘drastic climatic change’ during the Quaternary and for slow erosion rates in plateau areas, which contrast with high rates in deep valleys. For the reader, the conclusions are difficult to follow, because the relationship between text, figures, tables and sample num- Reviews 409 bers is not always clear. – Pawar & Kale (‘Waterfall tufa deposits from the Deccan Basalt Province, India: Implications for weathering of basalts in the semi-arid Tropics’, p. 17–36) , in a concise, well substantiated and instructive paper, discuss the nature of the weathering and of the hydrological regime of the tufa formation that developed in non-karstic (basaltic) areas and that are closely related to waterfalls, where turbulence and agitation of supersaturated waters induce precipitation of calcite.
Ladeira & Dos Santos (‘Tectonics and Cenozoic paleosols in Itaqueri’s Hill (São Paulo- Brazil): implications for the long-term geomorphological evolution’, p. 37–62) use sediments and paleosols (laterites, silcretes) to explain the complex geomorphological development with relief inversion as a result of Cenozoic (Paleogene to recent) tectonic uplift and subsidence in combination with pronounced climatic changes and sedimentation phases.
Preliminary results about the ‘Geomorphic evolution of the Ntem alluvial basin and physiogeographic evidence for Holocene environmental changes in the rain forest of SW Cameroon (Central Africa)’ (p. 63–79) are reported by Runge, Eisenberg & Sangen. The stimulating study is part of a project that examines causes and effects of ecological changes and their consequences on settlement expansion. The project most likely will contribute to a better understanding of the fluvial morphology of tropical African rivers as well as paleohydrological processes caused by aridification and/or climate fluctuations in West and Central Africa during the late Holocene.
Morphotectonic criteria such as drainage patterns/anomalies, terraces, sedimentary features, particular landforms, are commonly used for the identification and characterization of active blind thrust faulting in alluvial environments. These criteria are discussed by two case studies from Venezuela and Colombia in humid tropical climates. The authors (Ollarves, Audemard & López, p. 81–103) convincingly show that the application of these morphotectonic criteria requires that they comply with persistency and consistency among themselves. Furthermore, second-order streams must be efficient indicators of tectonic activity, otherwise, these morphotectonic criteria do not offer useful results.
Two papers discuss erosional processes in tropical areas. Schoorl, Claessens, Ulloa, de Koning &Veldkamp (‘Geomorphological analysis and scenario modelling in the Noboa – Panjan Area, Manabi Province, Ecuador’, p. 105–118) use two different scenarios for run-off based erosion and for mass-movement erosion to simulate the impact of soil redistribution and point to methodological problems with the interpolation technique in the Digital Elevation Model (DEM). – Marinho, Castro & de Campo have researched the ‘Hydrology and gully processes in the upper Araguaia River basin, Central Brazil’ (p. 119–145) by determining the hydrological dynamic of soils and of slopes. They studied a slope representative of the most erosive critical area, which has been used as pasture for three decades. Based on representative and comprehensive analyses (physical and chemical soil analyses, soil micromorphology, soil hydrology, GPR, climatic parameters, etc.), the authors ascribe gully formation to a hydrological imbalance of soils and slopes, which is characterized by an increase in hydraulic gradient and by a complete saturation of soils and saprolites together with piping in the soil-rock contact zone.
A rare, high-magnitude storm in northern Venezuela in December 1999 triggered debris flows and flash floods, and killed some 15,000 people. Larsen & Wieczorek (‘Geomorphic effects of large debris flows and flash floods, northern Venezuela, 1999’, p. 147–175) summarize information of prehistoric, historic and recent debris flows and floods, and describe in detail the devastating event of 1999. Their paper is a good example to show the importance of geomorphologic research with regard to careful planning of human settlements on or in the vicinity of alluvial fans.
The last four contributions focus on the Paraná Basin in Brazil and Argentina, the second largest fluvial hydrosystem of South America. Parolin & Stevaux discuss ‘Dry climate and eolian dune formation in the Middle Holocene in Mato Grosso do Sul State, Central West Brazil’ (p. 177–190). Their paper contributes to a better understanding of the Holocene paleoclimate of tropicalcentral Brazil. – The instructive paper by Stevaux, Barczysczyn, Medeanic & de Nóbrega describes ‘Characterization and environmental interpretation of a floodplain Holocene paleosoil: Implications for paleohydrological reconstructions in the Upper Paraná River, Brazil’ (p. 191–206). The authors present further evidence for a wetter and warmer climate since ~ 1,700 yr BP. – Paira & Drago summarize a basin-wide survey of morphometric parameters of 1,500 lakes and examine the relationships with the main channel and with floodplain evolution in their contribution ‘Genetical, morphological and evolutional relationships of the floodplain lakes in the Middle Paraná River hydrosystem’ (p. 207–228). – ‘Dynamics of sediment transport in two subtropical plain rivers of South America’ (p. 229–241) are analyzed by Orfeo. The study sites are located in the Chaco, an area with no significant pronounced relief and nearly untouched by previous geomorphological research.
For anyone conducting research in tropical areas, this publication will be of interest. Given the nature of the volume as a compilation of contributions with diverse content, the reader will find wide geographic coverage. However, the quality of the research varies between the individual contributions. Some papers are insightful and scholarly; others are only of limited use for ‘tropical geomorphologists’. The layout (text setting/line distance, quality of figures) could have been better. The journal Annals of Geomorphology can provide some guidance for a better layout.
Klaus Heine, Regensburg
Zeitschrift für Geomorphologie N.F. 52/3