Toposequences in Soils of Central Trinidad


The evolution of the soils and landscape of central Trinidad is reviewed in relation to the probable effects of eustatic changes in sea level and with particular reference to two sample areas where several surfaces of erosion and deposition are apparent. In the first area, the San Francisco Settle-ment, the soils are considered to occur as a sequence of: 'older mature soils' (Talparo, Phoenix, Las Lomas, and Arena Series) on higher ground, formed in situ from Pliocene strata; 'younger mature soils' (mainly Ecclesville and Moruga Series), formed on the slopes after erosion of the 'older mature soils'; and 'younger mature', intermediate, and 'immature' soils (Freeport, L'Ebranche, and Couva Series respectively) formed on alluvial terraces. In the second area, near Longdenville, the Freeport Series forms a low terrace on old alluvium, and the gently sloping to rolling land above this is shown to be a toposequence of the 'older mature soils' and areas of 'senile soils' (Piarco and Long Stretch Series), which have loamy seasonally waterlogged surface horizons over a dense brightly mottled horizon of clay accumulation. The formation of these toposequences appears to be a special case of the effect of erosion by retreat of slopes in producing soils of differing age and composition, which was particularly emphasized by CLINE in 1961. It is considered that, as there is no evidence of linked processes of formation of soils at eluvial, colluvial and illuvial sites, these particular sequences should preferably not be referred to as catenas.