Tropical Terrains Research Articles

Comments on the performance of selected low-power HF radio sets in the tropics

The performance of five low-power HF radio sets was measured at 3.6 MHz under field conditions in Thailand. Variations in performance were noted for CW and voice transmissions as a function of type of set, type of antenna, time of day, and communication range (5-100 mi) in tropical forest (jungle), mountain, and delta terrain. Radio teletype (RTTY) tests over longer paths (out to 1320 km) were made using a jeep-mounted set. The results showed that relatively good communications can be achieved in the tropics on short and intermediate length paths with low-power sets--especially when the proper antenna is used and when the operating frequency is properly chosen.

A re-evaluation of global plantgeographic provinces of the Late Paleozoic

A re-evaluation of the global plantgeographic maps for the Late Paleozoic, which have evolved through decades of paleobotanic investigations, is required in the light of plate tectonic studies. Advances in the computerization of palynologic data offer a new approach to this problem. Analyses based upon the palynologic data file of the Department of Geosciences, University of Arizona, render better correlation analyses of the plantgeographic conditions in the Late Paleozoic possible and aid the construction of more precise climatological maps which will provide crucial evidence for current plate tectonic models. The plantgeographic reconstructions produced indicate that: 1. (1) the Euramerian flora was situated in tropical regions and extended northwards and southwards into belts of dry climate; 2. (2) the Angaran flora appears to have been located in northern temperate zones; 3. (3) the Gondwanan flora developed in the southern temperate zones. A discrepancy existed, however, in relation to the Cathaysian flora. If China formed a part of the Eurasian plate in the Late Paleozoic, then extensive areas of the Cathaysian flora occurring in the coalfields of China and Korea should, according to current geographic maps, have been located in northern arctic regions. However, paleobotanical and palynological criteria indicate that because the Cathaysian flora was closely related to the Euramerian flora, it must have occupied a tropical terrain. This independent paleobotanical evidence supports the case of those scientists who, for other reasons, expected that the China plate and the Indian plate were located further south in the Late Paleozoic and drifted to the north in Mesozoic times.