DEPOSITION PATTERN ANALYSIS: AN ALTERNATIVE APPROACH TO SAND AND GRAVEL PROSPECTING IN TRINIDAD AND TOBAGO

SISNARINE SEEGOBIN
Ministry of Energy, Port of Spain,
Trinidad & Tobago

The Pleistocene sand and gravel terrace deposits along the southeastern foothills of the Northern Range of Trinidad are perhaps the most economically significant sources of construction aggregates in the island.
Systematic evaluation of these deposits has been conducted by the Government over the last two decades, guided largely by extraolation of information from existing quarroes. In recent years, however, the inherent inefficiencies of this method have become a costly burden to the Government's resource development efforts in the area, and this study represents the first step in providing comprehensive scientific control for the evaluation programme.
For the study, profiles from five (5) selected locations in the depositional area were constructed, using 1:25,000 topographic maps and aerial photographs to enhance topographic control. On these profiles auger hole data from previous exploration surveys were superimposed.
Subsequent analysis of the completed profiles and related data revealed the existence of remnants of at least seven (7) geomorphic terraces between the 7.6 m and 76.2 m levels. When the superimposed auger hole data were re-examined in light of these finding, the emerging pattern indicated that economically significant quantities of gravel were present only in the lower terraces - below 45.7 m. These findings represent the first step towards a detailed understanding of the distribution patterns exhibited by these terrace deposits. This knowledge can be used to further streamline resource evaluation efforts in the area.

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