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| Hammen, Th. van der; Nelson, H.W.. |
| A short time ago rumors reached Bogota that a big cavesystem had been discovered by some farmers in the southwest of the department of Tolima, between the villages of Cunday and Purificación. This region belongs morphologically and geologically to the Eastern Cordillera, and forms the westernmost spurs of this mountain chain. As the existence of these caves was completely unknown up to that time, and as no limestones were known from that region, a scientific expedition was organized for a first exploration. The geological party of this expedition was formed by Dr. J. A. Bueno, the author and his wife. We went by car from Bogota to Girardot and from there to Cunday. The next day we had a whole day’s walk to the entrance of the eaves. After two days and two... |
| Tipo: Article / Letter to the editor |
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| Ano: 1955 |
URL: http://www.repository.naturalis.nl/record/505956 |
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| Hammen, Th. van der; Gonzalez, E.. |
| The uppermost 32 metres of a 2436 metre core principally of lake sediments, Pleistocene and Holocene in age from the Sabana de Bogotá were analysed for its pollen content, at intervals of 10—15 cm. About seventy species, genera of families could be recognized, many of them for the first time. The rest of the core is being analysed and the results will be published later. The Sabana de Bogotá lies at an altitude of approximately 2500 metres above sea level, 4½°—5° North of the equator, and 74°—74½° West of Greenwich. From the diagram it may be deduced that glacial and interglacial periods affected the tropics equally as Europe and North America. It also shows that the glacial periods were at the same time pluvials, and the interglacials interpluvials.... |
| Tipo: Article / Letter to the editor |
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| Ano: 1960 |
URL: http://www.repository.naturalis.nl/record/505755 |
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| Hammen, Th. van der. |
| In the East of Holland, in the Province of Overijssel, there is a region that, from the point of view of landscape, is one of the most beautiful and the most interesting we know in this country: Twente. Already in glancing through this publication it will be clear that this region played an important part in our research. Apart from the fact that our personal predilection for Twente undoubtedly was of some influence, this choice was equally directed by the geological wealth of that region coupled to the fact that here, as a consequence of numerous recent excavations, the deposits were excellently exposed. Of course, our research equally extended over other provinces but, whereas there a stress was laid on pollenanalytical research, geological research was... |
| Tipo: Article / Letter to the editor |
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| Ano: 1952 |
URL: http://www.repository.naturalis.nl/record/505891 |
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