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One of the
most astounding and unique aspects of the Orinoco Delta is the mud volcano activity of the
Pedernales-Capure region along the north coast of the delta. The mud volcanoes highlight
the dynamic nature of the Orinoco Delta and illustrate how tectonic forces and mud
diapirism are influencing delta evolution. Whereas virtually all landforms in the Pedernales-Capure region have surface elevations
close to sea level, the mound-shaped mud volcanoes provide striking relief within the
coastal zone. There are at least 7 volcanoes in the area (probably more exist), and good
examples are found at the towns of Pedernales and Capure, including the Capure cemetery.
Individual volcanoes are usually circular convex mounds of mud 100-300 m in diameter and
10-20 m tall. In several examples, the mud matrix encases cobble to pebble-size clasts of
erupted sandstone, chert, and quartzite. All 5 of the volcanoes visited, except the
Pedernales volcano, are active, as demonstrated by one or more small conical vents with
pools that bubble intermittently (gas exsolution) and that are flanked by recent mud
flows. In several examples, tar seeps and pools of oil are present and mud-flow deposits
are impregnated with petroleum. Prior studies of the Pedernales-Capure area suggest that the mud volcanoes are surface expressions of a large northeast-southwest-trending anticline and fault zone, and near Pedernales and Capure, the anticline is cored by a mud diapir that extends to a depth of >1,000 m. Regionally, the mud volcanoes occur in an ~ 20-km-wide belt that extends southwest to Maturin and northeast into southern Trinidad and offshore. The mud volcano belt parallels a regional fault zone and the South American-Caribbean plate boundary, which suggests that tectonic transpressional stresses are responsible for the diapirism, faulting, and active mud volcanism in the Pedernales-Capure region. Future studies will attempt to use Landsat TM and radar imagery to map the distribution of the volcanoes in the Pedernales-Capure region and will evaluate the provenance and ages of the mud volcano deposits. |
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Please send comments,
questions, or suggestions to Edgar Guevara.
Copyright 1998 Bureau of Economic Geology