sediment type of the late Cretaceous made evident by the thickly deposited, pelagic shale of the Colon formation. This represents the beginnings of the Caribbean arc collision with the South American plate. As the collision continued, this region shifted from the passive margin stage to the foreland basin stage. These Paleogene sediments are characterized by fluvial and deltaic facies and make up the Misoa formation, fluvial sandstones that act as hydrocarbon reservoirs. Mountain building begins in the late Paleogene, producing mostly continental sandstone facies. Hydrocarbon resources Oil was discovered in producible quantities in Venezuela in 1914 at the town of Mene Grande in the east central part of the Maracaibo basin near a surface oil seep. In December 1922, Royal Dutch Shell's George Reynolds (formerly with the Anglo-Persian Oil Company) discovered the La Rosa Oil Field. The Barroso Well blew out at 100 thousand BOPD. In 1928, Jersey Standard discovered oil deposits under Lake Maracaibo. Today the basin accounts for approximately 50% of Venezuela's crude export capacity and approximately 15% of proven Venezuelan oil reserves. The region hosts one of the world's largest oil refinery complexes, the Paraguaná Refinery Complex. The nearby islands of Aruba and Curaçao also host large refineries that process oil from the Maracaibo basin. Together these refineries form the 'Venezuelan Circuit' of PDVSA. The Bolivar Coastal Field, BCF, on the eastern shore of Lake Maracaibo produces from Miocene sandstones and Eocene sandstones. West of Maracaibo, the La Paz Field produces from Cretaceous limestones, and oil is found in the stratigraphic traps of Boscan, Los Claros and the Urdaneta fields. Venezuela produces a mix of conventional heavy crude and unconventional crude derived from bitumen. This latter source, previously too expensive to produce in quantity, now makes up an increasing large percent of Venezuela's oil exports – 600,000 of Venezuela's three million barrels per day in 2006. In the Maracaibo Basin, the balance of reserves is toward its conventional deposits. As the country continues shifting toward bitumen production due to its increasing profitability and decreases in conventional reserves, the level of Maracaibo Basin oil production will decrease, while that of the Orinoco Belt and its massive bitumen deposits will increase. See also List of oil fields References External links History of the Venezuelan oil industry OPEC: Venezuela US Energy Information Administration: Venezuela Johnston Seismic Consulting Ltd. Maracaibo Basin: CSPG International Group Talks and References Natural regions of Venezuela