62
J.E. Conde
CARIBBEAN SEA
GULF OF PARIA
100
KM
Fig. 4.1. Orinoco River Delta and main tributaries
season between January and April is followed by a period of heavy rains
from May to August. A second drier period occurs in September and October and a second wet period in November and December. Although air
temperatures may vary considerably during the day, moderate but steady
northeasterly trade winds (Heinen et al. 1995) maintain mean annual temperatures between 25.5 and 26.6 °C, with a relative humidity of 60-80 o/o
(Wilbert 1994-1996). Mean annual evaporation ranges from 1,380 to
1,928 mm (Pannier 1979).
The Orinoco River watershed is geologically diverse (Schubert et al.
1986; Colvee et al. 1990), ranging from Precambrian formations in the
Guayana Shield (Diaz de Gamero 1996) to the delta, which dates from the
Holocene. The modern delta is composed of fluvial-marine argillaceous
sediments (Pannier 1979; Colonnello 1996) which are supplied by the Orinoco River (86-150 x 10 6 t year- 1 ; Bonilla et al. 1993; Cressa et al. 1993)
and probably by long-shore transport from the Amazon River (Van Andel
1967). Prominent landmasses in the delta are usually comprised of levees
J.E. Conde
CARIBBEAN SEA
GULF OF PARIA
100
KM
Fig. 4.1. Orinoco River Delta and main tributaries
season between January and April is followed by a period of heavy rains
from May to August. A second drier period occurs in September and October and a second wet period in November and December. Although air
temperatures may vary considerably during the day, moderate but steady
northeasterly trade winds (Heinen et al. 1995) maintain mean annual temperatures between 25.5 and 26.6 °C, with a relative humidity of 60-80 o/o
(Wilbert 1994-1996). Mean annual evaporation ranges from 1,380 to
1,928 mm (Pannier 1979).
The Orinoco River watershed is geologically diverse (Schubert et al.
1986; Colvee et al. 1990), ranging from Precambrian formations in the
Guayana Shield (Diaz de Gamero 1996) to the delta, which dates from the
Holocene. The modern delta is composed of fluvial-marine argillaceous
sediments (Pannier 1979; Colonnello 1996) which are supplied by the Orinoco River (86-150 x 10 6 t year- 1 ; Bonilla et al. 1993; Cressa et al. 1993)
and probably by long-shore transport from the Amazon River (Van Andel
1967). Prominent landmasses in the delta are usually comprised of levees