Geomorphic Evolution of the Northern Rupununi Basin, Guyana

摘要

The region described is located on the Amazon-Essiquibo divide and forms a tectonic depression in the heart of the Guiana Shield. The major physical aspects, including geology, tectonics, climate, geomorphic processes, drainage and relief conditions are mapped and analyzed. The surficial deposits of the area are identified and mapped and their origin postulated. Special attention is given to the evolution of laterites and laterite landforms. It is suggested that dissection of the laterite plateau and lowering of local base-level in early- and mid-Pleistocene times resulted in a change of vegetation from former forest to the present savanna. The significance of terrace and dune sands, cobbles and boulders of various rock-types, climatic and vegetative changes during the Pleistocene, and erosion surfaces, are evaluated as factors in the evolution of the present northern Rupununi landscape. (Author)